Risk Factors for Increased Intraocular Pressure and Ophthalmic Complications during Robot-Assisted Laparoscopic Prostatectomy

Abstract

Robot-assisted laparoscopic prostatectomy (RALP) is the most effective treatment option for prostate cancer. Special conditions of the operation affect intraocular pressure (IOP). The purpose of this review was to systematize new data on changes in IOP during RALP, to review the ophthalmic complications related to the robot-assisted approach, and to suggest measures to avoid such issues. A systematic search for articles of the contemporary literature was performed in PubMed database for complications in RALP procedures focused on positioning, access, and operative technique considerations. Several complications in RALP procedures can be avoided if the surgical team follows some key steps. Adequate patient positioning must avoid skin, peripheral nerve, and muscle injuries, and ocular and cognitive complications mainly related to steep Trendelenburg positioning in pelvic procedures. The robotic surgical team must be careful and work together to avoid possible complications. This review offers the first assessment of perioperative changes in IOP and ophthalmic complications during RALP and several steps in surgical planning to reach this goal. Further studies with a longer follow-up period are necessary to determine the clinical efficacy and safety of various types of general anesthesia.

1. Introduction

Minimally invasive surgery, including robot-assisted laparoscopic approaches, has been promoted in a hope that their use would reduce surgical complications. Since the Intuitive da Vinci system (Intuitive Surgical Inc., Sunnyvale, CA, USA) was approved for use in 2000, robotic surgery has increasingly become the standard procedure for the management of a broad range of common surgical procedures from general and colorectal surgery to urogynecological procedures [1]. The use of robotic surgery accounted for only 1.8% of all general surgery procedures in 2012, and this increased to 15.1% by 2018 [2]. Robotic surgery is attractive for several reasons, such as laparoscopic surgery, it offers smaller incisions, a lower risk of infection, a shorter hospital stays, and a shorter convalescence than its open counterpart. In addition, unlike laparoscopic surgery, robotic approach has the advantage of increasing surgical dexterity due to the increased degrees of freedom of the instruments. Robot-assisted laparoscopic radical prostatectomy (RALP) is now in widespread use for the management of localized prostate cancer. With the increasing popularity, frequency, and acceptance of the RALP procedure, an awareness of unique intra- and postoperative complications is heightened. There are few specific reports of the limitations and complications of RALP, including that of increases in intraocular pressure (IOP). RALP requires specific body condition, in which the patients must be placed in a steep (23–45°) Trendelenburg position (sTp). Gravity allows the abdominal viscera to be pulled away from the pelvic cavity, resulting in a clearer operating field. However, this positioning may lead to complications, with several ocular complications having been reported since the inception of robotic-assisted surgery. The risk of perioperative complications is increased by incorrect patient positioning, inadequate fixation, or even a long time in the proper patient positioning.

This review outlines general procedures most likely to develop damaging IOP levels and their causative factors, the effect of anesthetic agents and techniques on IOP, recent scientific evidence highlighting the significance of perfusion changes during surgery, key aspects of postoperative visual loss and management approaches for high-risk patients presenting for surgery, and to assess the ophthalmic complications related specifically to the RALP and to suggest measures of how to avoid them.

2. Postoperative vision loss

2.1 Incidence of postoperative vision loss

Getting blind after recovery from general anesthesia in patients who undergo RALP is a very rare (0.02–0.1%) but catastrophic complication of robotic surgery [3, 4]. The first description of perioperative visual loss (POVL) in Medline was published in 1950 [5]. A serious ophthalmic consequence, namely the retinal detachment attributed to sTp, was first reported in 1952 [6]. The penetration of robotic technology in various surgical fields increased ophthalmic complications. In recent years, cases of POVL with non-ophthalmic surgery have been reported, but the exact incidence of POVL is unknown because the data come largely from retrospective studies and case reports [7, 8]. The incidence of POVL following non-ocular surgery has been estimated to be as low as 0.0002% and as high as 0.2% [9]. The number of cases reported POVL registry yearly has been decreasing from a peak in 2000 and has been dropping since. It is probably due to a reduction in operative times along with intraoperative blood transfusion [10]. Although the incidence is extremely low, the prognosis is extremely poor [11].

2.2 Etiology of postoperative vision loss

The most common neuro-ophthalmologic causes of POVL are ischemic optic neuropathies (ION), followed by central retinal arteria occlusion [12, 13]. The etiology of POVL is multifactorial and intricately interrelated with patient, anesthetic, and surgical factors [14]. The integrity of the delicate structures of the eye that mediate vision is dependent on the IOP. Ocular perfusion pressure (OPP) depends on the difference between mean arterial pressure (MAP) and IOP, so intraoperative IOP elevation is a risk factor for postoperative blindness. Yet, IOP acts to compress the vessels within the globe akin to a Starling resistor and is a key component that determines the OPP. Venous congestion and decreased optic nerve perfusion in the absence of cerebrovascular and ocular circulatory autoregulation in an anesthetized patient contribute to the development of ION, leading to POVL [15]. Multiple factors have been proposed as risk for intraoperative IOP elevation and ocular perfusion imbalance, including the head positioning [16]. sTp combined with pneumoperitoneum caused an increase in IOP, reduced ocular perfusion, and possibly POVL. These rapid fluctuations in IOP and perfusion play a role in the pathogenesis of the visual field defects and associated ocular morbidity that frequently complicate otherwise uneventful surgeries [17]. When IOP is significantly elevated in the setting of glaucoma or prolonged sTp, it is important to maintain stable ocular perfusion by increasing MAP or decreasing IOP. The potentially negative vascular occlusive effects of elevated IOP are more likely to affect patients who experience episodes of decreased OPP due to systemic hypotension. This may result from the hypotensive effects of anesthesia or episodes of intraoperative hypotension. Given the unique patient’s sTp during RALP, ocular complications may be more likely to occur secondary to physiologic changes that occur within the eye itself.

The retina is one of the most metabolically active tissues in the body, and its functional integrity is dependent on an adequate blood supply with retinal function linearly related to the OPP. Retinal cell death has been demonstrated at OPP below 50 mmHg. Marked elevations of IOP (up to 4–5 times the normal value) with consequent borderline retinal and optic disk perfusion pressures occur for prolonged periods during many procedures, including RALP, especially, with their demand for sTp and/or hypotensive anesthesia, can induce IOP changes and ocular perfusion imbalance. The exact etiology of such outcomes is multifactorial, but ocular hypoperfusion plays a significant and frequently avoidable role. Those with preexisting compromised ocular blood flow are especially vulnerable to intraoperative ischemia, including those with hypertension, diabetes, atherosclerosis, or glaucoma. However, overly aggressive management of MAP and IOP may not be possible given a patient’s comorbidity status, and it potentially exposes the patient to risk of catastrophic choroidal hemorrhage. Anesthetic management significantly influences the pressure changes in the eye throughout the perioperative period. Strategies to safeguard retinal perfusion, reduce the ischemic risk, and minimize the potential for expulsive bleeding must be central to the anesthetic techniques selected [17].

2.3 Risk factors for postoperative vision loss

Numerous risk factors for POVL have been identified that include older patients with elevated baseline IOP, patients with hypertension, diabetes, obesity, anemia, vascular disease, increased blood viscosity, and patients who smoke, as well as patients who experience intraoperative hypotension, blood transfusion, lower colloid use during fluid administration or prolonged surgical times, and patients who are positioned on horseshoe-shaped headrests [18]. Patients with angle-closure glaucoma are also at high risk for ocular injury even during short procedures [19].

In 2007, a case of a 62-year-old patient who developed ION with complete bilateral loss of vision after a robotic-assisted procedure lasting 6 hour 35 minutes was first reported [20]. ION was described in a 58-year-old man after laparoscopic sigmoidectomy lasting more than 6 hours. It was postulated that the patient suffered from hypotension in conjunction with an acute increase in IOP due to prolonged sTp [21]. Another mean operation time from skin incision to fascial closure reported was 105 min (range, 55–300) [22]. In this study, the mean was 5.46 hour±60.3 minutes, but similar to the 5.3 ± 1.0 hour reported earlier [23].

Although definitive evidence is lacking, the quantity of blood loss may be a risk for the occurrence of ION. The mean estimated blood loss (EBL) reported from 1500 consecutive cases was 111 mL (range, 50–500 mL) [22]. In a 62-year-old patient who developed ION, the EBL was 1200 mL [20]. In one study, the mean EBL was 350 ± 343 mL, with no cases of ION. On the other hand, one patient became blind after laparoscopic prostatectomy even without observed hypotension, hemodilution, metabolic disorders, or extreme blood loss, and baseline IOP and time spent in sTp were identified as the only factors predicting an increase in IOP [13]. Recently, a rare case of non-arteritic anterior ION in 58-year-old female patient following robotic-assisted hysterectomy was presented. On fundoscopy optic disc edema and splinter hemorrhages at the optic disc edges were observed. Fluorescein angiography showed hypofluorescence of the optic disc in the early phases due to filling delay followed by hyperfluorescence with leakage from disc capillaries in the late phases of the angiogram. So, this case of ION is an uncommon cause of POVL after robotic surgery [24]. The case of a 34-year-old female who underwent an uneventful laparoscopic hysterectomy and suffered from complete POVL following the operation was recently presented. Operating time was 174 minutes, and EBL was 75 mL. No cerebral hemorrhage or ischemia was detected on imaging. Funduscopic exam revealed no structural abnormalities. The following morning, she reported mild light perception. Later that night, she reported a partial return of visual acuity and was discharged home. At her two-week postoperative visit, her vision had returned to baseline [25].

3. Robotic-assisted laparoscopic prostatectomy

3.1 IOP changes during minimally invasive surgery

IOP is regulated by aqueous humor production, aqueous humor drainage, autoregulation and control of choroidal blood volume, vitreous humor volume, and extraocular muscle tone [17]. While the production of aqueous humor is stable, the outflow of aqueous humor to the venous system may be affected by choroidal blood volume, vitreous humor volume, and extraocular muscle tone. Many surgical procedures require pneumoperitoneum, where the air is insufflated into the abdominal cavity and subsequent head-down position, where the patient is positioned supine on the table with the head tilted below the feet at an angle of roughly 16-degree, and up to 25–40-degree in sTp, both can cause hemodynamic alterations that may influence IOP increasing venous congestion. After induction of anesthesia, there is an initial IOP decrease from baseline (IOP is reduced significantly more by propofol compared to volatile anesthetics) followed by a slight increase after insufflation of pneumoperitoneum. Afterward, the venous congestion increases both central venous pressure (CVP) and IOP. The latter increases in a time-dependent manner: mean IOP doubling within 60 minutes and, in 25% of cases, tripling within 120 minutes. This IOP increase may be exacerbated by the pneumoperitoneum-induced increase in partial pressure of carbon dioxide (PaCO₂) [23]. Indeed, the carbon dioxide (CO₂) insufflation leads to an increase in IOP due to decreased venous return and increased episcleral venous pressure. An increase in СМЗ, which is then, in turn, transmitted to the episcleral veins and from these to the capillaries and arterioles, also contributes to decreased optic nerve and ocular perfusion. The choroidal expansion may also lead to elevation [26]. This increased IOP then leads to decreased OPP. IOP, however, normally plateaus after about 30–60 minutes and decreases after return to the supine position. As the pneumoperitoneum can cause an increase in intraoperative IOP, one study compared IOP following extraperitoneal CO₂ insufflation and intraperitoneal CO₂ insufflation for the laparoscopic procedure. The change in intraoperative IOP was not statistically significant in either group, or there was no significant difference in intraoperative IOP change between the groups [27].

sTp is frequently used during minimally invasive surgery. IOP changes during laparoscopic or robotic hysterectomy conducted in the sTp were prospectively evaluated in 10 female patients with no history of ocular pathology [28]. There was a statistically significant trend of increasing the IOP from baseline to the second hour of sTp. The IOP remained significantly elevated once the patient was returned to the supine position.

Changes, in IOP depending on different positioning, were compared in patients without eye disease undergoing laparoscopic operations requiring sTp or reverse Trendelenburg tilt. A significant decrease in IOP was observed after the establishment of anesthesia irrespective of the combination of anesthetic agents employed. Elevation in IOP after abdominal insufflation with CO₂ to create pneumoperitoneum was observed in all patients with a trend toward a greater increase in IOP with standard sTp compared to a reverse Trendelenburg tilt, which was associated with a slight reduction in IOP in several patients. These changes were reversed in patients when intra-abdominal pressure (IAP) was not more than 14 mmHg, and operative time was not beyond 90 minutes. None of these required treatment on follow-up with resolution of the increase in all instances. These findings suggest that sTp and prolonged length of surgery are more important factors in attaining more dangerous elevations of IOP than the standard pneumoperitoneum induction for routine cases [29].

Current surgical robotics platforms, starting with the da Vinci® Si™ and certainly with the da Vinci® Xi™, allow one to easily obviate the risks associated with lithotomy positioning by performing RALP in supine. A majority of surgeons continue to perform robotic prostatectomy in lithotomy, although nearly two-thirds have access to the Xi system. It remains the standard approach to RALP despite advances in robotics that have allowed for greater flexibility in positioning and operative planning. The first survey of surgeons’ perspectives on RALP positioning has shown that surgeons have not been adopting supine positioning. Only 22% of all respondents used supine positioning, and only half had considered it. The biggest reason for position choice appears to be the convenience to the surgical team, and this may be related in part to training inertia. Given the significant physiologic changes associated with positioning, the modern robotic surgeon should be familiar with positioning options offered by contemporary technologies, and surgeon and surgical team education efforts should be aimed at overcoming hesitation due to practice-inertia and toward greater creativity [30].

3.2 Risk factors for increasing IOP during sTp

Multiple intraoperative factors affect the IOP increase during pneumoperitoneum in the sTp: end-tidal carbon dioxide (EtCO₂), CVP, MAP, peak airway pressure (PAP), transperitoneal absorption of CO₂, intra-abdominal pressure (IAP), and duration of surgery (DoS) (Table 1). A combination of these factors, possibly together with abnormal self-regulation in the posterior portion of the optic nerve, pro-thrombotic trends, and other specific patient factors, can lead to enough decreased oxygen supply to the optical nerve to cause ischemic injury. Additionally, there may be a potential link between prolonged increase in ICP from sTp and pneumoperitoneum and short-term postoperative cognitive impairment [38].

First author, year	Awad 2009 [31]	Molloy 2011 [13]	Hoshikawa 2014 [32]	Molloy 2014 [33]	Yoo 2015 [34]	Blecha 2017 [26]	Demasi 2017 [35]	Goel 2020 [36]	Shirono 2020 [37]
Country	USA	USA	Japan	USA	Korea	Germany	Italy	India	Japan
Procedure	RALP	Laparoscopic	RALP	RALP and gynecologic laparoscopic	RALP	RALP	RALP	RALP	RALP
sTp angle, °	25	32–37	23	32–40	29	45	30	>45	NA
Carboxyperitoneum pressure, mmHg	15	NA	NA	14–15	8–20	15	15	15	NA
Total operative time	142 (105–210) min	3 h	4.57 ± 0.03 h	2.20 ± 0.56 h	113 ± 26	218 (120–357) min	143.56 ± 7.98 min	150 ± 41.7 min	265 (129–487) min
Estimated blood loss, mL	80 (45–155)	250 (50–600)	364 ± 196	159.8 ± 146.2	440 ± 288	NA	213.2 ± 98.6	NA	275 (0–1650)
Intravenous fluid, mL	2000 (1600–3100)	2500	NA	2058.7 ± 620.8	1264 ± 358	880 (550–2200)	1545 ± 174	NA	NA
Factor(s)	MAP; PAP; EtCO2; DoS	DoS	DoS	BMI; Age	IAP	MAP; PAP	Angle of tilt	Obstruction in aqueous outflow	DoS

Table 1.

Factors determining increased IOP in sTp.

Note: NA, not available.

With the aim to explore different trends of IOP change patterns and its related factors, IOP measurements were performed at different time points in four clinical common (lithotomy, lateral, prone, and supine) surgical positions during the pelvic or abdominal surgeries using laparoscopic techniques [39]. The surgical lithotomy position after the CO₂ pneumoperitoneum was changed to have different angles with head-low and foot-high positions. After 10 minutes of position change, IOP tended to rise. The reasons were that: (1) the thoracic pressure increased due to diaphragmatic elevation after the CO₂ pneumoperitoneum, (2) the anesthesiologist increased the ventilation volume/min to maintain end-tidal carbon dioxide (EtCO₂) in a reasonable range and the airway pressure elevation was transmitted to the thoracic cavity, increasing CVP, (3) the low head position also increased the volume of blood returning to the heart, which increased the venous pressure in the head and face, causing obstruction of venous return in the eye and head, resulting in the pressure increase in episcleral vein, and leading to pressure increase in IOP. Postural position for the surgery played a role in IOP change. After postural changes, the body maintains hemodynamic stability through a series of complex regulatory mechanisms, including the self-regulation system, venous and arterial systems, and neural reflexes. However, this regulatory mechanism was weakened under anesthesia so healthcare workers needed to understand the pattern of IOP changes in different surgical positions.

The negative effect of sTp was shown when compared IOP peaks in patients with healthy eyes who underwent RALP in sTp versus patients who underwent “open” or laparoscopic access in a supine position. A statistically significant increase in IOP was observed during RALP using sTp [40].

A systematic review of the studies on both elective patients and healthy non-anesthetized volunteers in the spinal, neurosurgical, and urological fields was identified, which explored the changes in IOP according to patient positioning, all reported significant rises in IOP in both head-down and prone positioning g, and the strongest effects were seen in those patients placed in combined head-down and prone position. Rises in IOP were time-dependent in all studies. Patients undergoing laparoscopic colorectal surgery in a prolonged head-down position were likely to experience raised IOP, and thus were at risk of POVL [41].

In another study, using univariate mixed effects models, PAP, MAP, EtCO₂, and DoS were significant predictors of the IOP increase, whereas age, BMI, EBL, volume of fluid administered, mean airway pressure, and desflurane concentration were not predictive. Surgical duration and EtCO₂ were the only significant variables predicting changes in IOP during stable and prolonged sTp. Indeed, the continued absorption of intraperitoneal CO₂, resulting in increased PaCO₂ and leading to vasodilation in the choroid plexus and an increase in IOP. Positive association between PAP and IOP throughout surgery, but not an increase over time was also shown. The proposed mechanism is that an increase in IOP leads to an increase in CVP, which can reduce the outflow of intraocular fluid through the episcleral veins and increase IOP [31].

Although prior studies have reported that pneumoperitoneum may increase IOP, it is not clear whether this increase is related to the effects of pneumoperitoneum or to the sTp. One study aimed to evaluate the potential fluctuations of IOP during colorectal laparoscopic surgery in two groups of patients: those with and those without sTp. In all the patients, standard pneumoperitoneum (<14 mmHg) induction led to a mild rise in IOP. The patients with Trendelenburg positioning showed a greater increase than the patients without it, but IOP evaluation 48 hours after surgery showed no substantial differences between the two groups. At the multivariate analysis, no potential predictors of increased IOP during surgery were identified. Thus, the patient’s position during surgery may represent a stronger risk factor for IOP increase than pneumoperitoneum-related IAP [42].

The effect of sTp on IOP was examined during RALP. The highest IOP values were reached at sTp and intraperitoneal insufflation measurement time. Resistance index of the central retinal artery values was different, while impedance index of the central retinal vein values remained similar when patients were supine and awake and were anesthetized. Despite a long time of stay in sTp, the risk of ophthalmic complications was low [43].

sTp and pneumoperitoneum increased IOP directly proportional to the angle of tilt of the Trendelenburg position. Furthermore, the proportional lowering of OPP was directly correlated to the angle of tilt of the Trendelenburg position from the induction of anesthesia until the end of the procedure, but there is no agreement on the exact effects of MAP and IOP on blood flow in optic nerve [35].

Body mass index (BMI) was significantly correlated with IOP levels in patients, undergoing RALP performed with the sTp at baseline, 30, 60, and 90 minutes, and at the final time points when the surgery was finished. When the IOP levels were compared between the patients with BMI of 35 kg/m² and lower and the patients with BMI higher than 35 kg/m², the higher BMI patients had significantly higher levels of IOP. Patients’ age was also positively correlated with IOP [33]. In contrast, one study demonstrated that age, BMI, DoS, and sTp did not affect IOP. Univariate mixed effects models showed PAP and MAP to be significant predictors for IOP increase [26]. Data from a study support that IOP significantly increases in a time-dependent manner after sTp in anesthetized patients undergoing RALP. Multiple perioperative factors are believed to be involved in controlling the increase in IOP during surgery, but there was no significant relationship between the changes in IOP and the age and BMI in this cohort [44]. In participants without a history of eye disease or eye surgery who underwent laparoscopic prostatectomy, bowel, and hysterectomy surgical procedures in sTp for a minimum of 120 minutes, the IOP increased from a range of 9 to 28 mmHg in the supine position to 25 to 54 mmHg at 120 minutes in sTp. About half cases were followed up through 3.5 hours of surgery in sTp. Ending IOP in the supine position was statistically significantly higher than baseline IOP. In 26% of cases, IOP tripled within 2 hours in sTp. Ocular perfusion pressure dropped below IOP in this greater than 30 BMI kg/m² patient population. There was a significant correlation of increase in mean IOP as time progressed. Several patients complained of blurred vision for a period following surgery, but POVL was not present [13].

Despite no patient experienced any ocular complications related to IOP increase, including ION, IOP was noted to increase in a time-dependent fashion. Along with previous reports, this suggests that longer operation times may induce substantially more risk for harmful IOP increases [32]. In the present study, IOP increased when patients were in sTp, and it was thereafter elevated in a time-dependent manner during sTp. In addition, the console time significantly affected the increase in IOP during RALP at a cut-off of 4 hours. So, to prevent a marked elevation of IOP in men undergoing RALP, a console time of <4 hours is important. Without a long console time, the use of RALP may be expanded to men having a high baseline IOP without compromising safety [37].

Based on the univariate linear regression during the CO₂ pneumoperitoneum in the sTp period, BMI, PAP, total CO₂ amount, and IAP were significant predictors of IOP changes, positively correlated with IOP. Multivariate analysis revealed that the only significant predictor of IOP was IAP. A possible explanation may be that a low IAP led to a decrease in the peritoneal CO₂ absorption and PAP, which may have attenuated the IOP increase [34]. Contrary, despite the fact that MAP, EtCO₂, and airway pressure remained consistently at the same level throughout the RALP and IOP levels still increased. But, there was no relation between rise in IOP and change in MAP, airway pressure, and EtCO₂ during surgery. Thus, this rise in IOP may be due to the obstruction in aqueous outflow in sTp with normal production and absorption of aqueous fluid. As the normalization of IOP occurs after normalization of patient posture, it can only be explained by sudden release of outflow obstruction of fluid leading to fall in pressure [36].

Regarding the contribution of preexisting retinal and/or central nervous system comorbidities on the risk of ophthalmic complications s following RALP with sTp, outcomes of patients with previous retinal surgery, cerebrovascular events, aneurysms, neurosurgery, and externally healthy comparators were compared—no retinal or CNS-related perioperative complications were reported in either the study or control groups [45]. In this study, IOP was not routinely recorded during the pre-, post-, or perioperative periods and, as such, it is unclear as to whether changes in IOP contributed to the incidence of retinal and CNS-related complications.

4. Anesthetic concerns for RALP

With the advent of robotic surgery, the physiologic change after pneumoperitoneum and sTp affect IOP. Use of the da Vinci surgical system requires additional precautions not normally needed for other laparoscopic procedures. For the anesthesiologist, robotic surgery comes with the following challenges: sTp to provide the best field of view for the surgeon, longer duration of pneumoperitoneum, and limited access to the patient after robot docking [46, 47]. This combination affects ocular, homeostasis, and leads to devastating ION. The anesthetic management of RALP patients involves a careful positioning on the operative table and appropriate fluid management [48]. RALP presents a challenge for anesthesiologist due to potentially serious inherent complications because of sTp and pneumoperitoneum during the procedure, therefore, anesthesiologists need to be fully aware of, prepared to handle, the challenges generated by this new technology, and manage the associated complications [49, 50, 51, 52, 53, 54, 55].

RALP has the following principal downside: a steep learning curve, although acceptable operative times can be achieved in <20 cases, and positive surgical margin rates may require experience with >80 cases before a plateau is achieved. The significant learning curve should not be understated [56]. A highly experienced surgeon can perform a RALP in about 105 minutes with a minimum blood loss of 111 ml [22]. But, every urologist needs to perform more than 150 operations to learn how to manipulate unfamiliar instruments and get used to a limited vision field. Until the operation is fully mastered by the surgeon, the time of surgical work can be multiplied, and blood loss will increase. As a result, complications may occur more frequently [57]. These data demonstrate the lowest IOP value in the supine position and the highest in sTp, regardless of the type of anesthesia. Almost all studies were conducted at 30-degree up to 35-degree sTp. The surgeon’s working conditions are better, the steeper the positioning, the better the intra-abdominal view, and probably less bleeding. Hypotheses from previous studies show that patients placed in sTp for several hours have a high risk of ocular changes and perioperative complications.

IOP increases significantly between abdominal insufflation in supine position and 240 minutes of sTp. The greatest increase in IOP occurs within 5 minutes of placing the patient into the sTp and continues to increase significantly, while the patient is in sTp. IOP increases of the magnitude found in systematic review and meta-analysis demonstrate the need for implementing intraoperative interventions to mitigate the increase in IOP and reduce the risk for postoperative vision loss and other ocular complications in patients undergoing surgery in the sTp [58].

4.1 Anesthetic regimens during RALP

Anesthesia for patients undergoing robotic-assisted surgery is different from anesthesia for patients undergoing open or laparoscopic surgery, and new anesthetic concerns accompany robotic surgery. These concerns include physiological effects of fixed extreme positioning of the patient over a long time, pneumoperitoneum, and the need for carefully monitored relaxation of the patient. There is interest for prospective studies assessing perioperative ocular and visual events that add knowledge to the perioperative behavior of IOP in different types of surgery. Inhalation anesthesia with both sevoflurane and desflurane, as well as total intravenous anesthesia with propofol, are widely used in laparoscopic and robot-assisted procedures [59, 60]. There are no restrictions in the choice of the anesthetics [61].

Earlier, a systematic review with meta-analysis of 20 randomized controlled trials (RCT) comparing the effects of propofol-based total intravenous anesthesia (TIVA) and volatile anesthesia on IOP during laparoscopic surgery, including lower abdominal, colorectal, RALP (one study), cholecystectomy, pelvic and gynecological surgery, ophthalmic surgery, and spine surgery in the prone position was conducted. The mean IOP was significantly lower in the TIVA group after intubation, pneumoperitoneum, sTp, and lateral decubitus positioning. So, propofol-based TIVA is more effective during surgery at attenuating the elevation of IOP and should be considered in at-risk patients [62].

We found 14 full-text articles describing the effect of sTp on IOP during RALP under volatile or intravenous anesthesia. The included articles consisted of 13 prospective observational studies [23, 26, 31, 32, 35, 36, 40, 44, 63, 64, 65, 66, 67, 68] and one clinical study (Table 2) [68]. All studies were prospective single-centered. As an intervention, there was a RCT of the effect of volatile versus intravenous anesthesia. The review did not include conference abstract because of the insufficient information for assessment of the quality of evidence [69], one article in Japanese [70], and one study with only graphically presented IOP levels [38].

First author, year		Awad 2009	Hoshikawa 2014	Yoo 2014		Mondzelewski 2015	Taketani 2015	Blecha 2017	Demasi 2017	Mizumoto 2017	Hirooka 2018	Hirooka 2019	Awad 2020	Goel 2020	Balkan 2021	Kondo 2021
Country		USA	Japan	South Korea		USA	Japan	Germany	Italy	Japan	Japan	Japan	USA	India	Turkey	Japan
Study design		Observational	Observational	RCT		Cohort	Observational	Observational	Observational	Observational	Observational	Observational	Cohort	Observational	Cohort	Observational
Patients, n		33	31	66		18	25	51	50	22	20	10	24	31	34	21
Anesthetic		Desflurane	Sevoflurane	Propofol	Sevoflurane	Sevoflurane	Propofol/Desflurane	Propofol	Propofol	Propofol	Propofol/Desflurane	Propofol/Desflurane	NA	Propofol/Sevoflurane	Sevoflurane	Sevoflurane
Total operative time		142 (105–210) min	4.57±0.03 h	92 (71–142) min	105 (85–140) min	NA	318±60 min	218 (120–357) min	143.56±7.98	5.46 h±60.3 min	274.4±52.2 min	227.3±47.9 min	248.2±40.2	150±41.7 min	205.3±44.3	263±61
sTp angle, °		25	23	30		30	25–30	45	30	30	30	30	25	>45	35–45	30
Pneumoperitoneum pressure, mmHg		15	NA	15±5		15	NA	15	15	NA	NA	NA	NA	15	10	NA
Estimated blood loss, mL		80 (45–155)	364±196	415±211	431±269	291±220	267±188	NA	213.2±98.6	350±343	173.3±158.9	90±131.7	134.2±115.6	NA	NA	NA
Intravenous fluid, mL		2000 (1600–3100)	NA	1485±588	1558±557	NA	1733±534	880 (550–2200)	1545±174	NA	NA	NA	1939.6±772.2	NA	NA	2230±460
IOP, mmHg	Т0	19.9±3.6^1	13.2 (8–20)^2	17.9±3.7^1	17.5±3.6^1	13.7±3.2^1	14.9±2.1^1	19.9±3.6^1	19.9±3.3^1	NA	NA	NA	NA	NA	NA	18.3±2.4^1
	Тmin	15.9±4.8^1	9.8 (4–15)^2	NA	NA	NA	11.0±2.7^1	15.9±4.8^1	13.1±3.5^1	10.4 (8.2–12.5)^3	12.3±2.6	11.2±3.8^1	14.2 (11.7–16.6)^3	19.2^1	12.4±3.1^1	NA
	Тmax	33.9±7.4^1*	24.2 (12–33)^2*	19.9±3.8^1	23.5±4.3^1*	29,9 (27.4–32.5)^3*#	29.4±7.0^1*	33.9±7.4^1*	32.2±4.4*	29.6 (27.6–31.5)^3*	29.8±8.7*	28.3±4.8^1*	37.4 (35.0–39.9)^3*	40.0^1*	21.8±4.7^1*	25.3±2.2^1*
		Ligation of the dorsal venous complex (SP)	End of sTp	30 min of sTp		60 min of surgery	4 h of sTp	Ligation of the SP	End of surgery	End of sTp	240 min of surgery	180 min of sTp	End of sTp	End of sTp	120 min of sTp	150 min of sTp
Ocular complications		Conjunctival edema in 7 patients; resolved the next day	None	None		Optic disc hemorrhage in 1 patient	Visual field defects in 7 patients 1 week after operation	None	None	None	None	None	None	None	None	None

Table 2.

Comparative analysis of studies of IOP during RALP depending on the type of anesthesia.

Note: NA, not available; SP, Santorini’s plexus.

The data of IOP are presented as ¹mean (±SD), ²mean (range), ³mean (95% CI), ⁴median (IQR).

Time points for perioperative IOP measurements: T₀ - prior to induction of anesthesia while supine and awake, T_min - anesthetized and supine, and T_max –maximum during the operation in a sTp stay.

Statistically significant differences: *between T_0/min and T_max; #between patient’s group.

The IOP value was 13.3 ± 0.58 mmHg higher on average at the end of the period of sTp compared with the supine position. One patient maintained significantly increased pressure and represented an outlier. However, adverse ophthalmic consequences of intraoperative changes in IOP were not identified [31].

The mean IOP increased three-fold time-dependently from 9.8 mmHg to 24.2 mmHg and a maximum of 36 mmHg after 4 hours of surgery. Not any statistically significant ocular complications related to IOP increase (changes of the retinal nerve fiber layer thickness or visual acuity) were observed [32].

Based on the results of RCT, it was reported that propofol-based TIVA was more effective than sevoflurane-based inhalational anesthesia in attenuating IOP increase during RALP with pneumoperitoneum and sTp. IOP was significantly less immediately after establishing pneumoperitoneum, 30 minutes after sTp, and 5 minutes after tracheal extubation in the operating room [68].

Significant elevations of IOP were experienced during robotic surgery utilizing sTp in patients with healthy eyes, operated under inhalation anesthesia of 17 up to 53 mmHg at 60 minutes of surgery, 24 up to 52 mmHg, and 24 to 55 mmHg at 150 and 240 minutes, respectively. There were no significant changes in retinal nerve fiber layer thickness and Humphrey visual field pattern [40].

Transient but significant unilateral visual field defects were found in 28% of the patients after RALP dominantly in the lower hemifield without abnormal findings in the optic nerve head or retina, and the visual field recovered to normal within 3 months after surgery. IOP was significantly increased up to 29.4 mmHg but did not differ significantly in patients anesthetized by inhalationally or intravenously [23].

The combination of permanent 45°sTp and pneumoperitoneum during RALP has a pronounced influence on IOP. The mean IOP was significantly 4 mmHg lower after induction of TIVA and more than doubled from 15.9 up to 33.9 mmHg at the end of the operation. In 14% of patients, IOP was higher than 40 mmHg, and the highest IOP measured was 59.6 mmHg. Non-ocular complications were observed in the recovery room, 8 hours later on the ward, and the next day [26].

sTp and pneumoperitoneum increased IOP from the induction of intravenous anesthesia directly proportional to the angle of tilt to 20 mmHg, so the pulsatile ocular blood flow and OPP both significantly decreased (from 15.5 ± 3.3 to 10.0 ± 3.2 μL/s and from 70.1 ± 5.9 to 51.7 ± 11.5 mmHg, respectively) and reached their lowest levels at the end of the RALP procedure. No complications occurred during the RALP procedure, nor were any postoperative complications reported [35].

IOP transiently significantly increased from 10.4 mmHg up to 29.6 mmHg with the timing of sTp in patients anesthetized intravenously. No significant disorders in ocular structural and functional parameters were found until long after RALP. The mean visual acuity, IOP, mean deviation, pattern standard deviation, the ganglion cell complex, and retinal nerve fiber layer thicknesses and the central fovea thicknesses measured before and after surgery did not differ significantly [44].

Although IOP significantly increased during RALP from 20 to 53 mmHg in healthy patients, regardless of the type of anesthesia, there was no progression of the visual field and retinal nerve fiber layer thicknesses after surgery or any other ocular complications at 1 and 3 months after surgery [63].

The effect of the sTp surgical procedure on the retinal structure and function during RALP in 10 glaucoma patients was investigated. Average IOP (mmHg) significantly increased from 11.2 ± 3.8 up to 28.3 ± 4.8 during RALP. Two eyes of two patients exhibited significant retinal nerve fiber layer thickness progression [64].

A significant increase in IOP during RALP secondary to the sTp and CO₂ insufflation was confirmed. Accumulation of subclinical damage on the retina, such as age, hypertension, diabetes, macular degeneration, anatomic breech position of optic disk at risk, and preexisting undetected ocular disease, could potentially lead to permanent changes when combined with sTp but not lead to significant retinal changes (ganglion cell complex and retinal nerve fiber layer thickness, foveal threshold, mean deviation, and pattern standard deviation) in patients with healthy ocular system at 3 months postoperative [65].

The study of the critical sTp angulation of patient with the floor more than 45° have shown the gradual rise in IOP with time. All the patients had a normal baseline mean IOP of 18–19 mmHg, remaining unchanged after creation of pneumoperitoneum indicating insignificant effect on IOP by raised IAP. As soon as the patient was placed in sTp, IOP started to rise with significant difference between IOP values at different time points with each other and baseline. The continuous rise in IOP reached maximum value of 40–41 mmHg. This information is important, especially in patients suffering from glaucoma and ocular hypertension as it may convert an advanced surgical technique into an ocular nightmare for the patient along with medicolegal issues for treating physician [36].

Changes in both IOP and optic nerve sheath diameter (ONSD) during RALP were evaluated, and any correlation between IOP and ONSD was examined during RALP. The highest IOP recorded in cohort was 32 mmHg and was associated with the 35-to 45-degree sTp and abdominal carbonic gas insufflation. Although both IOP and ONSD increased, no significant correlation between the two parameters was observed. This could be explained by the different mechanisms that increase IOP and ONSD. Based on these findings, intraoperative measurement of IOP can be useful in patients at high risk for increased IOP during RALP [66].

Small study assessed 21 patients to quantify changes in IOP in time in patients put on the sTp. In addition to confirming increased IOP during sTp, the authors concluded that the increase was moderate 90 minutes after positioning with a mean IOP value 7 mmHg above baseline, resuming to the baseline value as that before the induction of anesthesia roughly 30 minutes after returning to the supine position. No ocular complications, such as blindness, narrowing of the visual field, or impaired visual perception, were reported in the first 3 months postoperatively [67].

4.2 Other procedures

One study investigated whether IOP changes were different depending on the anesthetic drugs. Patients scheduled for pelvic laparoscopy were randomly allocated into the propofol-based TIVA group or the desflurane-based volatile group. In all the groups, IOP decreased after anesthesia was initiated (17 ± 2 to 11 ± 2 mmHg). Pneumoperitoneum in addition to the head-down position raised the IOP highly in the desflurane group, and the average IOP value was over the normal limit (22 ± 4 mmHg). In contrast, propofol kept IOP similar to the preoperative level during the whole period of pneumoperitoneum (18 ± 3 mmHg). For the laparoscopic surgery performed in the head-down position, propofol may be more helpful in preventing ocular hypertension [71].

The effects of propofol-based TIVA with those of sevoflurane anesthesia on IOP in patients undergoing lower abdominal laparoscopic surgery in sTp were compared. The change in IOP was significantly different between the groups. Maximum rise in IOP was 15.5 ± 0.9 mmHg and 19.8 ± 1.2 mmHg in TIVA group and sevoflurane group, respectively. In TIVA group, IOP remained almost equal to the baseline value, while in sevoflurane group, IOP increased significantly with the difference 4.0 ± 1.2 mmHg. So, TIVA is more effective than inhalational anesthesia in attenuating the increase in IOP during laparoscopic surgery requiring pneumoperitoneum and sTp [72].

IOP variation during repetitive positional changes in patients undergoing laparoscopic colorectal surgery was evaluated, and the effect of desflurane and propofol anesthesia on IOP change was compared. Repetitive positional changes in anesthetized patients caused markedly increased IOP in the sTp. IOP values were significantly lower in patients undergoing TIVA than in patients undergoing desflurane anesthesia during intraoperative positional changes. TIVA was more effective than inhalation anesthesia in attenuating IOP increases during frequent positional changes in long-duration laparoscopic surgeries. IOP values in sTp in the desflurane group were higher than those in the propofol group. In contrast, most of the IOP values in the sTp in the propofol group remained within the normal range [73].

Effects of combinations of four different anesthetic agents on IOP in laparoscopic gynecological operations using 12–14 mmHg pneumoperitoneum and sTp at 35° were studied in a prospective double-blind RCT. Different from other studies, two intravenous agents used in anesthesia induction were combined with two inhalation anesthetics, and their effects on IOP were investigated. Results indicate that propofol induction causes decreased changes in IOP, independent of sevoflurane, or desflurane use. In addition, there were no statistically significant differences between the IOPs in supine position after extubation and before intubation. Thus, the IOP values in supine position after extubation were not affected by the anesthesia technique. In all groups, rather than pneumoperitoneum, sTp increased IOP values by higher amounts [74].

4.3 Effects of dexmedetomidine

Whether dexmedetomidine effectively attenuates the increase in IOP remains inconclusive. The aim of systematic review and meta-analysis was to evaluate the effects of dexmedetomidine on IOP in adult patients undergoing surgery, which requires general anesthesia and endotracheal intubation. Twenty-nine RCTs were included. The IOP levels were significantly lower in patients receiving dexmedetomidine after the administration, after pneumoperitoneum, and after the patients were placed in a sTp. So, dexmedetomidine effectively attenuates the increase in IOP levels and should be considered, especially for at-risk patients [75].

Regarding the effect of dexmedetomidine, a RCT evaluated the effect of intraoperative continuous infusion versus equal volume of physiologic saline on IOP in patients undergoing RALP in the sTp. The highest mean IOP measured 60 minutes after the patients had been placed in the sTp, was 19.9 ± 5.0 mmHg in dexmedetomidine group, and 25.7 ± 5.0 mmHg in control group with significant difference. No ocular complications were noted. So, intraoperative continuous infusion of dexmedetomidine may help alleviate IOP increase in patients undergoing RALP in the sTp [76].

Also, a prospective double-blinded RCT assessed the efficacy of systemically infused dexmedetomidine in preventing the increase in IOP caused by a sTp. Patients undergoing laparoscopic or robotic-assisted surgery due to colon, prostate, or gynecological cancer received dexmedetomidine throughout the operation versus saline. IOP increased in the sTp and was 11.3 mmHg higher at the end of surgery in the saline group. This increase in IOP was attenuated in the dexmedetomidine group, for which IOP was only 4.2 mmHg higher. So, dexmedetomidine infusion attenuated the increase in IOP during laparoscopic surgery in a sTp, without further decreasing the OPP [77].

The effect of intraoperative dexmedetomidine on the IOP in patients undergoing RALP under propofol-remifentanil anesthesia was studied in a double-blind RCT. A linear mixed model analysis demonstrated IOP at 180 minutes after placing patient in the sTp, significantly lower in the dexmedetomidine group than in the control group. So, dexmedetomidine combined with propofol decreases IOP in the sTp during RALP [78].

4.4 Other ways to reduce the elevated IOP

While the literature is infrequent and undeveloped, certain anesthetic techniques, including deep neuromuscular blockade, modified positioning, providing periodic position changes or rest periods, and administering specific medications or anesthesia technique have been shown to mild-to-modest attenuate the increase in IOP [79].

One of the ways to reduce IOP during RALP may be to change the extreme head-down position, and in an RCT, modified Z Trendelenburg position was used (the patient’s head and shoulders are placed horizontally). Median IOP was in the normal range at anesthesia induction and before positioning and increased at sTp. From the start of modified Z Trendelenburg position, IOP decreased and was significantly lower. At the time of supine and the end of pneumoperitoneum, IOP decreased to normal (19.6 mmHg) in Z Trendelenburg position group but remained in the hypertensive range (24.9 mmHg) in sTp group. The significant positive effect on patient neuro-ocular safety by lowering IOP and accelerating its recovery to the normal range was reached without any negative consequences for surgery [80].

Contrary, increasing the angle of the operating table from 25-degree to 30-degree would provide better surgical visibility, which would lead to shorter surgery time and reduced blood loss in RALP. In a prospective RCT involved a total of 30 consecutive patients, significant time-dependent increases in IOP were observed in both the 25-degree and 30-degree Trendelenburg positions; however, the IOP values measured at the same time points were similar between the two groups. Several operative variables (DoS, EBL, and intravenous fluid intake) did not significantly differ between the two groups. So, the 25-degree sTp can reduce the risk of catastrophic position-related ophthalmologic complications after RALP without prolonging the operative time and/or increasing EBL during surgery, as compared with the 30-degree sTp [81].

Upon identification of elevated IOP readings intraoperatively, we can effect changes in position. In some patients with severe IOP elevation during sTp, when the head of the operating table was returned to the level, supine position halfway through the procedure, to meet procedural requirements, IOP appeared to improve by the end of the procedure in contrast to subjects who were not leveled. Observations that elevation of IOP over time can be mitigated by transient and periodic changes in position during surgery, open the question of whether interventions other than maintenance of MAP can decrease the effect of elevated IOP on cerebral perfusion pressure. It is possible that by measuring IOP, one can predict when a change in the level of the table should be made so as to limit further IOP increases. A second intervention is that, because the calculation of perfusion and flow to the eye (OPP) is derived by obtaining IOP readings and subtracting them from the MAP, one can maintain OPP by elevating MAP. In summary, by measuring IOP, practice changes can be implemented to ensure the patient’s ophthalmic safety [82].

There has been no study of the effect of positive end-expiratory pressure (PEEP) on IOP during pneumoperitoneum with sTp. Applying 5 cmH₂O of PEEP as compared with zero-PEEP did not significantly increase IOP during RALP. These results suggest that low PEEP <10 cm H₂O can be safely used during RALP that takes a few hours of pneumoperitoneum and sTp without a clinically significant risk of IOP increase in patients without preexisting eye disease [83].

The possible effect of perioperative fluid management on the outcome of surgical patients has recently been debated. One of the inherent risks of the liberal approach to infusion therapy is unintentional hypervolemia, which can lead to an increase in IOP. Restrictive compared to liberal intravenous fluid administration leads to a better patient’s outcomes and reduction in the length of hospital stay. In a small group of gynecological patients during robotic surgery, restrictive strategy, along with maintaining close to normal EtCO₂ levels, negated the effects of sTp, and increased PAP on IOP [84]. Contrary, in another small group of women undergoing laparoscopic gynecologic pelvic surgery, the effect of liberal versus restrictive protocols of perioperative fluid management on fluctuations in IOP during the perioperative period was explored. The main finding of this prospective study was the similar IOP measurements between patients who were treated with different preoperative fluid management protocols [85].

Continuous deep neuromuscular blockage (NMB) can improve surgical conditions and facilitate RALP to significantly attenuate the increase in IOP, as was shown in the double-blind RCT. The highest IOP value was observed at 60 minutes after CO₂ pneumoperitoneum in the sTp and was significantly lower in deep NMB group (19.8 ± 2.1 mmHg) than in the moderate NMB group (23.3 ± 2.7 mmHg). RALP was accomplished at the low IAP of 8 mmHg in 25 and 88%, respectively. The overall surgical condition was acceptable in both groups [34].

The effects of continuous systemic administration of esmolol versus placebo on IOP during laparoscopic and robotic surgeries for recto-sigmoid cancer in a sTp were investigated. The IOP increased markedly after adopting the sTp, reaching 28.8 ± 4.4 mmHg, which was ∼5.7 mmHg higher than in the esmolol group. So, esmolol can alleviate the increase in IOP during a sustained sTp without adverse effects [86].

A dangerous increase in IOP during prolonged laparoscopic intervention may be susceptible to topical drugs. In a quasi-experimental study, dorzolamide-timolol eye drops were examined during lengthy laparoscopic urologic and gynecologic procedures with the patient in sTp. Patients received treatment when IOP levels reached 38 to 40 mmHg. Repeated-measures analysis of variance showed that IOP values dropped significantly after drug intervention at 60-, 90-, and 120 minutes. Effect size of pharmacologic intervention on IOP reduction was strong [33]. On the contrary, in prospective masked interventional RCT, the effect of preoperative administration of brimonidine tartrate versus placebo (artificial tears) on IOP during RALP in sTp setting was evaluated. Significant and sustained IOP elevation of >1.5x baseline in the sTp was noted in both groups. The mean IOP 1 hour after sTp was 29.4 ± 6.9 and 27.2 ± 3.4 mmHg in the drug and placebo groups, respectively (P = 0.35). So, preoperative brimonidine does not prevent IOP spikes in sTp [87].

5. IOP in patients with glaucoma

Although acute angle closure glaucoma is increasingly prevalent and often questions arise concerning perioperative anesthetic management, evidence-based recommendations to guide safe anesthesia care in patients with glaucoma are currently lacking. Patients with low vision present challenges to the anesthesia provider that are becoming more common as the population ages [88].

Patients with primary open-angle glaucoma have decreased outflow through the trabecular meshwork of the eye, resulting in IOP. It is known that the sTp causes increased IOP, but there are no current guidelines for monitoring and treating patients with glaucoma undergoing surgical procedures while in the sTp. A case of successful intraoperative management of increased IOP in a patient with glaucoma undergoing RALP, while in sTp was described [89].

Prospective study enrolled 39 patients undergoing laparoscopic surgery, including 10 with eye diseases (six with normal tension glaucoma and four with a narrow anterior chamber and normal range IOP). All patients, with or without eye diseases, experienced significantly elevated IOP with no significant differences between groups. The average maximal IOP reached 20 mmHg at the end of surgery, with no patient had an IOP of >40 mmHg as a critical threshold during surgery. So, using pneumoperitoneum of 10 mmHg and a Trendelenburg position of 15° during a 3-hour surgical period could be performed within a safe range of IOP [90].

Given the aging population of RALP patients in whom risk for glaucoma is significant, preoperative ocular health assessment should be considered. Robotic technology for prostatectomy is increasingly frequent. Such procedures, as for robotic surgery for other pelvic procedures, require steep head-down tilt body positioning, with transient increase in IOP, and it is a relative counterindication for patients with open-angle glaucoma, aimed at avoiding additional damage to the optical nerve [31]. Specific attention should be directed toward identifying any history of glaucoma during the preoperative evaluation of patients in whom RALP is planned. If the patient has a known diagnosis of glaucoma, a discussion of the perioperative management with the ophthalmologist is recommended [91]. Since an increased IOP during the surgery was the probable cause of the retinal nerve fiber layer thickness changes, ophthalmologic examinations should be performed before and after RALP, especially in glaucoma patients. While it remains unknown whether eyedrops can effectively reduce elevated IOP during surgery, glaucoma patients should be instructed to take their medications prior to RALP when using the sTp and have their IOP routinely monitored during these surgeries. Furthermore, in patients scheduled to undergo RALP, comprehensive eye examinations should be recommended in all these subjects prior to the surgical procedure [64].

6. Recommendations for robotic-assisted and laparoscopic procedures

Most of the complications assessed are related specifically to RALP approaches, and therefore are not expected in open surgery. The present review is focused on avoidable RALP-related ophthalmic complications and suggests how the surgical team should work in a way to avoid them. In the light of evidence from the existing literature, surgical and anesthesiologic measures to prevent and manage ocular complications in robotic-assisted laparoscopic interventions are suggesting. It is advisable to develop an interdisciplinary collaboration between surgeons, anesthesiologists, and ophthalmologists on a procedural and medicolegal level with the intent of mutual training [92]. Some advocate preoperative ocular examination and regular monitoring of ONSD as a representative of raised intracranial and intraocular pressure during intraoperative period to ensure early awareness of surgical team, implement early interventions as needed, and thus reduce intraoperative ocular complications and POVL.

A Molloy/Bridgeport Anesthesia Associates Observation Scale enabling caregivers to determine when to institute preventive measures to optimize ocular perfusion was designed based on a prospective repeated-measures correlation regression model. Visual assessment of presence of eyelid edema or chemosis and baseline IOP values determine the probability of when an IOP greater than 40 mmHg (critical threshold) is reached. Significant predictors of IOP greater than 40 mmHg are determined to be presence of chemosis and baseline IOP and significantly correlated to increasing IOP. The receiver operating characteristic curve area under the curve score is 0.86 ± 0.03. Caregivers can use this observation scale to assess the need and timing for IOP-normalizing interventions and possibly to prevent POVL [82].

On 11 September 2012, the APSF convened a multidisciplinary consensus of experts to create a statement of safety recommendations for those patients at-risk, and to assure that suggested management reflects evolving information. Those experts explained how (1) sTp in robotic pelvic surgery, (2) IAP from insufflation, (3) low colloid/crystalloid ratios, and (4) a long duration of such conditions could all increase the risk of retro-orbital and/or optic nerve edema and compartment syndrome. These hydrostatic and osmotic forces are the variable components within the Starling equation that describe net fluid movement between compartments [93].

Joint consensus on anesthesia in urologic and gynecologic robotic surgery, written by Società Italiana di Anestesia Analgesia Rianimazione e Terapia Intensiva (SIAARTI), Società Italiana di Ginecologia e Ostetricia (SIGO), and Società Italiana di Urologia (SIU), recommend to limit the use of 30 degrees sTp only for the time strictly necessary for surgery to be performed, using a position tailored to the pelvic operatory field of the subject; the sTp should be avoided in high risk-patients (Level moderate, Grade A) [94].

Whether patients should be informed of ION, especially those undergoing higher-risk surgery and complex instrumented surgery, is controversial. Because most patients are first seen by anesthesiologists soon before surgery, consider requesting that the surgeon discuss the possible complication at an earlier, more relaxed, preoperative visit [95].

Under the auspices of the Anesthesia Patient Safety Foundation, an interdisciplinary consensus of experts has been created to make recommendations on patient safety [93]. The experts explained that (1) abdominal position, (2) sTp, (3) intra-abdominal pressure, (4) colloid-to-crystalloid ratio, and (5) prolonged duration of such conditions increase the risk of developing optic nerve edema and compartment syndrome [96].

Given the lack of scientific proof of cause and effect, the informed consent process itself was emphasized. The APSF thinks that anesthesia professionals and surgeons should discuss, with those patients at-risk, the remote chance of partial or complete blindness, the current state of understanding of those risks, and the interventions that may reduce those risks. Furthermore, the APSF considers that if this is not in a joint consent, nor part of the surgical consent, then it should be made a part of the anesthesia consent. Suggested and speculative interventions might include the following: minimizing intra-abdominal pressure, degree and duration of Trendelenburg, and the amount of crystalloid; deliberate hypotension should be carefully reconsidered, the head may be elevated, colloid may be substituted for some of the crystalloid, anemia should be monitored, and considerations of staging the procedure could be made [93].

7. Conclusions

Robotic surgery is becoming more prevalent and is being increasingly used in various specialties. RALP presents a challenge not only for surgeons but also for anesthesiologists. The detailed understanding of physiological changes of RALP is essential. The performing of the RALP requires the use of sTp. With the increasing popularity, frequency, and acceptance of the RALP procedure, an awareness of unique intra- and postoperative complications is heightened, including that of increases in IOP. The sTp required for operative exposure has been shown to increase this value. We found that IOP increases significantly depending on the duration of the operation. Despite this increase, there were small or no significant postoperative changes in visual function and ophthalmic complications in patients without prior eye disease.

There are several perioperative factors involved in the increase in IOP. Some of these factors, such as hemodynamic management, ventilation strategy, and volemic load, can be controlled by an anesthesiologist. Other factors, such as patient positioning and duration, are inherent in the operation itself. The exact nature of the relationship between the angle and duration of sTp and the increase in IOP remains unclear.

Most patients generally tolerate robotic prostatectomy well and appreciate the benefits; however, anesthesiologists must have an intimate knowledge of the physiological changes associated with RALP. Specifically, anesthesiologists must consider the changes in the cardiopulmonary, ocular, and intracranial systems that occur when patients are placed in the lithotomy and sTp, and when pneumoperitoneum is created.

Intraoperative head-low position had certain effects on the IOP of patients, showing different patterns of changes with the surgical process. Therefore, the head-low angle should be minimized without affecting the surgical operation. Intraoperative IOP measurement is recommended for patients in head-low foot-high lithotomy position. After the operation, the nurses should make a good handover and pay attention to the postoperative IOP changes and the occurrence of any adverse events, to identify the problems early and provide appropriate treatment.

While the literature is infrequent and undeveloped, certain anesthetic parameters, including deep neuromuscular blockade, modified positioning, and the use of dexmedetomidine have been shown to have mild-to-modest decreases in IOP. These modifications may prove to have even greater significance in patients with preexisting ophthalmologic pathologies, such as glaucoma, which were excluded from the studies’ analyses. Well-selected patients, adequate positioning, mentorship training during the learning curve, and avoiding last-longing procedures are key steps to prevent RALP-related complications. Fortunately, those specific complications are rare, but one should keep alert as they can be devastating if not recognized early, thus surgeons should have a low threshold of suspicion. A dedicated robotic team is essential to reduce perioperative complications. Hence, anesthesiologists need to stay abreast of current knowledge and be prepared to give better quality of anesthesia care to patients. Meticulous preoperative ophthalmological assessment, restriction of intravenous fluids, “rest stops,” eyelid taping, and ocular dressings are the major protective measures suggested by the literature. Collaboration between the surgical team and the anesthetist is also essential. Further studies should focus on resident training, cost-effectiveness, and long-term outcomes in anesthesia for robotic surgery.

Careful preoperative evaluation, intraoperative conduction, minimizes the risk of complications and helps patients to reach full recovery. Excellent outcomes are the result of individualized approach to the patient and good communication between team members. Large prospective studies are needed to assess the relationship between sTp and ophthalmic complications and to develop clinical recommendations for the prevention and treatment of elevated IOP in elderly patients with preexisting eye diseases during operations of longer duration. Up to this point, it is necessary to consider the available data of the effect of patient positioning on IOP. Aggressive assessment of elevated IOP may be required when the operation time exceeds 5 hours. A patient with glaucoma may not be a candidate for robotic surgery due to the risk of ophthalmic complications.