Anesthetic concerns for robotic-assisted laparoscopic

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COPYRIGHT© 2012 EDIZIONI MINERVA MEDICA

REVIEW

Anesthetic concerns for robotic-assisted laparoscopic radical prostatectomy D. M. GAINSBURG Departments of Anesthesiology and Urology, The Mount Sinai Medical Center, New York, NY, USA

ABSTRACT The anesthetic concerns of patients undergoing robotic-assisted laparoscopic radical prostatectomy (RALP) are primarily related to the use of pneumoperitoneum in the steep Trendelenburg position. This combination will affect cerebrovascular, respiratory and hemodynamic homeostasis. Possible non-surgical complications range from mild subcutaneous emphysema to devastating ischemic optic neuropathy. The anesthetic management of RALP patients involves a thorough preoperative evaluation, careful positioning on the operative table, managing ventilation issues, and appropriate fluid management. Close coordination between the anesthesia and surgical teams is required for a successful surgery. This review will discuss the anesthetic concerns and perioperative management of patients presenting for RALP. (Minerva Anestesiol 2012;78:596-604) Key words: Prostatectomy - Anesthesia - Perioperative care.

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obotic-assisted laparoscopic radical prostatectomy (RALP) has become the second most performed robotic-assisted surgical procedure worldwide.1 The incidence of prostate cancer has been on the rise along with a concurrent increase in the number of robotic-assisted procedures. According to the GLOBOCAN 2008 project of the International Agency for Research on Cancer of the World Health Organization, prostate cancer is the second most frequently diagnosed cancer of men and the sixth leading cause of death from cancer in men. Estimated worldwide numbers from this project showed 899000 new cases of prostate cancer being diagnosed along with 258000 deaths.2 According to Intuitive Surgical (Sunnyvale, CA, USA), the manufacturer of the da Vinci® robotic operating system, there were approximately 98000 robotic-assisted prostatectomies performed worldwide in 2010. With these numbers expected to continue to grow every year, anesthesiologists need to be aware of the periop-

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erative concerns in these patients. The anesthetic management of RALP presents challenges of understanding and managing the physiological effects and risks of pneumoperitoneum in the steep Trendelenburg position. This review will discuss the anesthetic concerns and perioperative management of patients presenting for RALP. Surgical procedure In order to fully appreciate the various issues involved in the anesthetic management of patients presenting for RALP it is helpful to understand the surgical procedure. In RALP the patient is placed in the lithotomy position, arms tucked at the side of the table, and drapes placed over the patient that limits the anesthesiologist’s ability to access the patient. Pneumoperitoneum is initiated and the patient is then placed in a 30o to 45o Trendelenburg position. Additional ports are inserted into the abdo-

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GAINSBURG

men and the robotic arms are docked (attached) to the ports. Because of the limited access to the patient after draping; any lines, monitors, and patient protective devices need to be placed and secured beforehand. Additionally, special care in regard to the endotracheal tube should be taken to avoid it from becoming kinked or pulled out. Once the robot is positioned over the patient with its arms attached to the ports; movement of the patient and/or cardiopulmonary resuscitative measures cannot be performed unless the robot is first detached.3 With the surgeon sitting at the robotic console and an assistant at the patient’s side, the surgeon guides the robotic arms to dissect the bladder neck, vas deferens and seminal vesicles, and the prostate. Nerve sparing is performed when possible. The dorsal vein complex and the urethra are then divided which renders the prostate free. The prostate is placed elsewhere in the abdominal cavity and the surgeon completes the vesico-urethral anastomosis. Bilateral pelvic lymph node dissection is performed followed with the placing of a perivesical drain. The robot is undocked and moved away from the patient.4, 5 A plastic specimen bag is introduced into the abdomen, the prostate placed inside, and removed from the patient through one of the port incisions. The ports are removed, incisions are closed, and the patient is awakened.3-5 Operative times are dependent upon surgical experience with reports ranging from means of 160 to 296 min with mean blood loss reported from 50 to 287 mL;5-8 however, these numbers are surgeondependent and may be increased in a difficult case or with a surgeon early in his learning curve. Anesthetic concerns The significant anesthetic concerns are the physiological effects of pneumoperitoneum in the Trendelenburg position, restricted access to the patient secondary to the mass of the equipment set over the patient, and prevention and/ or treatment of complications due to inducing pneumoperitoneum and placing the patient in exaggerated lithotomy and steep Trendelenburg positions.

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Physiological effects and risks of pneumoperitoneum in the steep Trendelenburg position The combination of pneumoperitoneum along with the steep Trendelenburg position during RALP will affect cerebrovascular, respiratory, and hemodynamic homeostasis. Insufflation of carbon dioxide (CO2) to induce pneumoperitoneum significantly decreases blood flow to organs within the abdominal cavity by direct mechanical compression.3 Non-surgical risks of RALP range from mild subcutaneous emphysema to devastating ischemic optic neuropathy. Cases of brachial plexus injuries,9 corneal abrasions,7, 10 laryngeal edema,9 venous gas embolisms 11, 12 and posterior ischemic optic neuropathy 13 have been reported. The possibility of pneumothorax or pneumomediastinum must always be considered. Cerebrovascular effects The use of pneumoperitoneum and the Trendelenburg position either separately or in combination have been shown to increase intracranial pressure (ICP).14-16 The creation of pneumoperitoneum causes increased intra-abdominal pressure, which obstructs venous return from the lumbar venous plexus resulting in increased ICP.16 Several studies have also observed increased ICP in the Trendelenburg position.14, 15, 17 These increases in ICP were caused by elevated venous pressure hindering cerebral venous drainage leading to increases in cerebral blood volume and CSF volume.15, 17, 18 While most of these studies were performed using animal models, Mavrocordatos et al. in a study of 15 neurosurgical patients reported an increase in ICP from 8.8 to 13.3 mmHg when placed in the 30o Trendelenburg position.15 In patients with cerebral ischemia or cerebrovascular disorders inducing pneumoperitoneum and placing in the Trendelenburg position may have disastrous consequences because of excessive increase in ICP.19 Two recent studies have observed regional cerebral oxygen saturation (rSO2) during RALP.19, 20 Near-infrared spectroscopy (NIRS) cerebral oximetry was used to noninvasively monitor


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rSO2, which reflects a balance between cerebral oxygen supply and demand.21 Both studies showed that the use of pneumoperitoneum with the steep Trendelenburg position increased rSO2, therefore suggesting that RALP does not induce cerebral ischemia. Since NIRS measures only rSO2 of the frontal cortex, an increase does not imply normal global cerebral oxygenation.21 Another finding from these studies was that rSO2 increased in relation to increased PaCO2. This contrast with the findings of Lee et al. who reported that during laparoscopic gynecological surgery the rSO2 decreased with hypercapnea caused by CO2 pneumoperitoneum.22 Since hypercapnea causes an increase in cerebral blood volume with a resultant increase in ICP, they recommend that in order to preserve cerebral oxygenation levels that patients be maintained within normocapnic range.22 Respiratory effects During RALP the use of the steep Trendelenburg position causes abdominal contents to push the diaphragm cephalad along with all of the mediastinal structures.3 This cephalad movement reduces the lung’s functional reserve capacity (FRC), decreases pulmonary compliance, and predisposes to alelectasis.3 Further reductions in FRC and pulmonary compliance are caused by the increase in pulmonary blood volume and gravitational forces on the mediastinal structures.3 Pneumoperitoneum also impairs respiratory mechanics. Intra-abdominal pressures up to 15 mmHg are commonly used with the range being between 12-15 mmHg to allow enough operative space in the peritoneal cavity.3, 5 When combined with Trendelenburg position, the European Association for Endoscopic Surgery recommends to avoid pressures higher than 12 mmHg because of decreased pulmonary compliance.23 Therefore careful monitoring of the intra-abdominal pressure is a concern during RALP. Increased intra-abdominal pressure along with cephalad movement of the diaphragm resulted in a more than 50% rise in peak and plateau pressures.24 In order to overcome these effects an elevated peak airway pressure is required

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to maintain a constant minute volume.24 With increased peak inspiratory pressures the risk of barotrauma increases. This potential risk might be lowered by reducing tidal volume, increasing respiratory rate, and allowing permissive hypercarbia.7 Danic et al., in a review of 1500 RALP cases, found that chest binding, steep 45° Trendelenburg position, and high insufflation pressures decreased pulmonary compliance by 68%.10 Hemodynamic effects Several studies have reported on the hemodynamic effects concerning the combination of pneumoperitoneum and the steep Trendelenburg position for RALP.20, 25-27 Mean arterial pressure (MAP) and systemic vascular resistance (SVR) were observed to increase >25% and 20% respectively during the initiation of pneumoperitoneum.25 These changes are caused by increased intra-abdominal pressure compressing the aorta and increasing afterload, and might be further enhanced by humoral factors.28 Lestar et al. observed that the addition of Trendelenburg position after insufflation did not change the increased MAP, but SVR returned to basal values.25 They also noted that central venous pressure (CVP), mean pulmonary arterial pressure, and pulmonary capillary wedge pressure were not increased by insufflation. However, in combination with the Trendelenburg position, these pressures all had a > two-fold increase from initial values. Strain on the heart, as indicated by right- and left-sided stroke work index, also increased due to the two- to three-fold increases in filling pressures without effecting cardiac performance. Other findings were that heart rate (HR), stoke volume, cardiac output (CO), and mixed venous oxygen saturation were unaffected during surgery; however, HR and CO increased significantly in the immediate post-surgical period.25 These observations probably reflect sufficient cardiac reserve in these patients. However, in patients with compromised cardiac function, increases in preload might precipitate heart failure.25 Other studies have reported different findings than those observed by Lestar et al.. during


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pneumoperitoneum with the Trendelenburg position. In an earlier retrospective report by Danic et al., MAP decreased by 17%, HR decreased by 21%, and CO decreased by 37%.10 Falabella et al. observed no change in MAP during initiation of pneumoperitoneum, but in combination with Trendelenburg position they noted an increase in MAP of approximately 20%. They also reported a decrease in CO, and an increase in SVR.26 Haas et al. observed increases in MAP and CVP similar to Lestar et al.; however, CO showed a significant increase of 22.5% in contrast to other studies.27 Other than the Danic et al., a large retrospective review, these prospective studies were limited by the relatively small numbers of patients enrolled. Other patient factors, e.g. age, cardiovascular status, obesity, and volume status, may also influence these observations.3 Severe bradycardia has also been noted to occur upon initiation of pneumoperitoneum in RALP cases.7 This is probably induced by vagal stimulation that is elicited during peritoneal distension.

Risks of the steep Trendelenburg position

Risks of pneumoperitoneum CO2 subcutaneous emphysema (SCE) is a common complication of laparoscopic surgery with an estimated incidence of approximately 0.3% to 3.9%.29 Risk factors include maximum end-tidal CO2 of 50 mmHg or greater, the use of six or more operative ports, operative time over 200 minutes, and older patients.30 SCE is thought to be a harmless and transient complication; however, severe cases may cause severe hypercarbia.29 Another concern is that SCE may develop in prefascial planes leading to life-threatening complications of pneumothorax, pneumomediastinum, and pneumopericardium.31, 32 SCE quickly resolves with cessation of insufflation. The recommended approach is keeping the patient mechanically ventilated at the end of surgery until hypercarbia is corrected in order to prevent an excessive increase in the work of breathing.33 Venous gas embolism is a potentially lifethreatening complication. Clinical presentation depends not only on the size of the bubbles, but also the rate of entry into the circulation. It

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should be suspected when there is unexplained sudden cardiovascular collapse along with changes in the capnographic tracing.3 CO2 gas embolism has been observed to occur during two distinct periods – during insufflations 34, 35 and again during dissection of the deep dorsal venous complex.11, 12 In two separate studies by Hong et al.., embolic events during RALP were only detected during transection of the deep dorsal venous complex.11, 12 In both studies the emboli were subclinical and none of the patients exhibited cardiac instability or abrupt end-tidal CO2 changes.11, 12 Since CO2 is extremely soluble in the presence of red blood cells, it is less life-threatening than a similar sized air emboli.36 Case reports of complications related to pneumoperitoneum during RALP appear in the literature. These range from a case of transient complete motor paralysis following RALP implicating venous gas embolism 37 to one case of pulmonary edema requiring reintubation and treatment with furosemide.38

Careful positioning of the patient is of paramount concern during RALP. Table position changes from supine/lithotomy to the steep Trendelenburg position predisposes patients to sliding cephalad and even off the operating table.9, 10 Facial, pharyngeal, and laryngeal edema may also occur with steep Trendelenburg position. The amount of intravenous fluid given, and/or reduction in venous outflow from the patient’s head caused by pneumoperitoneum, when either is combined with prolonged steep Trendelenburg position, may lead to laryngeal edema. Restriction of fluid and limiting time in the head-down position may help to avoid this complication. If facial and/or conjunctival edema is noted at the end of the procedure, the anesthesiologist should have a high index of suspicion for the presence of laryngeal edema. In this instance a endotracheal cuff leak test should be performed before extubation.9, 10 Ocular injuries range from corneal abrasions to the devastating ischemic optic neuropathy. Corneal abrasion is a common anesthesia-relat-


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ed complication in RALP with a reported incidence of 3% to 13.5% when using either eye or plastic tape.10, 39 Possible causes can be chemosis or exposure keratopathy.39 Preventive measures include warning the patients about the risk of chemosis and corneal abrasion, instruction to avoid eye touching, restricting the amount of intravenous fluid during Trendelenburg position, and the use of eye patches or transparent occlusive dressings to protect the eyes.7, 10, 39 Ischemic optic neuropathy is a rare complication that is usually associated with patients in the prone position with significant blood loss.40 In the literature, one case of ischemic optic neuropathy to occur during RALP has been reported,13 while another case was reported during a nonrobotic laparoscopic prostatectomy.13 The RALP patient was in prolonged steep Trendelenburg position, received a large amount of intravenous fluid, and had excessive blood loss. The Trendelenburg position increases intraocular pressure during RALP with surgical duration and endtidal CO2 being significant predictors.41 Increased end-tidal CO2, which reflects increased arterial CO2, may lead to choroidal vasodilation and increased intraocular pressures.41 It is also hypothesized that elevated venous pressure in the head and neck from the head-down position leads to interstitial fluid accumulation from capillary leak, decreased venous outflow, and decreased perfusion of the optic nerve. Damage to the optic nerve may be caused by several mechanisms: ischemia caused by small pial arteries supplying the nerve, venous infarction from reduced venous outflow, and/or direct mechanical damage from the elevated interstitial pressures.40, 42 Anesthetic management Preoperative evaluation As with any elective procedure a thorough pre-anesthetic evaluation of the patient should be performed. With the mean age for patients undergoing RALP being approximately 60 years, care should be taken to ensure optimization of their cardiovascular, respiratory, metabolic, and other systems. This population of men has an increased incidence of coronary artery disease

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and renal abnormalities secondary to prostatic hypertrophy.3, 7, 10 Since postoperative facial, ocular, and laryngeal edema might delay extubation, require insertion of an oral or nasal airway, or necessitate re-intubation; patients with known or suspected airway issues might be at increased risk postoperatively.43 Preexisting peripheral neurological deficits should be documented.43 In patients with glaucoma or other ocular diseases, currently there is no known increased risk of ischemic optic neuropathy during RALP; nevertheless, ocular-specific questions should be asked and referral to an ophthalmologist for any concerns.41 In light of the cardiac implications discussed previously, patients with significant cardiac disease will require further evaluation. Echocardiogram, stress test and/or perfusion studies might be indicated.3, 10, 43 Of special concern, are patients with coronary artery disease who have drug-eluting stents. One case of stent thrombosis during RALP has been reported in a patient with a two year old drug-eluting stent in whom clopidogrel and aspirin had been stopped for seven days prior to surgery by his cardiologist.44 Consultation with a cardiologist is necessary before discontinuing antiplatelet therapy and 81 mg aspirin should be continued throughout the perioperative period.43, 45 Because of the higher peak airway pressures required to ventilate, patients with severe chronic obstructive pulmonary disease are at increased risk. Additionally, RALP is relatively contraindicated in patients with lung bullae, because of the potential complication of rupture.10, 46 With the possibility of severe hemorrhage, which in laparoscopic surgery can be difficult to control, discontinuation of anticoagulants and antiplatelet agents must be ensured at a safe preoperative interval. As previously discussed, consultation with a cardiologist should be obtained for patients with cardiac stents.44 Patients with previous abdominal surgery may undergo extensive lysis of adhesions, which lengthens the surgery and adds to the possibility of bleeding. Though bleeding is rarely significant to require transfusion, blood should be available for every patient.3 Obese patients (body mass index >30 kg m-2)


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are a concern because they may have an unexpected difficult airway, and a higher incidence of coronary artery disease, pulmonary dysfunction, and diabetes. Care in positioning must be taken with these patients for the steep Trendelenburg position to avoid neurological injury. In experienced RALP institutions outcomes with obese patients are similar to non-obese patients.3, 47 Anesthetic technique Pneumoperitoneum and steep Trendelenburg position necessitates the use of general endotracheal anesthesia with mechanically controlled ventilation. Care should be taken with the placement of the endotracheal tube because of tracheal shortening during pneumoperitoneum may result in endobronchial intubation.48 Choice of anesthetic agents will be dependent upon the patient’s cardiovascular status as well as the presence of other co-morbidities. Complete muscle relaxation is essential in order for optimal pneumoperitoneum to be obtained.3, 10 Danic et al. does not recommend placement of a preoperative epidural for postoperative pain control because of the minimally invasive nature of RALP.10 Hong et al., though, suggest that a thoracic epidural might be beneficial in patients with chronic obstructive pulmonary disease or morbid obesity.49 Standard monitors used for any general endotracheal anesthetic is all that is usually required. Additional monitoring and intravenous fluid lines will be dependent upon the patient’s medical condition and/or the experience of the operating team. Since there is limited access to the patient after the robot is docked, invasive monitors in higher risk patients should be placed preoperatively.3 Positioning As discussed previously, positioning is of the utmost concern in patients undergoing RALP. Care must be taken to ensure that the patient does not slide off the table when placed in the steep Trendelenburg position. Several methods are used to prevent this, but each has their drawbacks. Shoulder braces have been shown to cause brachial plexus injuries.10 Several authors advocate the technique of strapping the patient to the operating table

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with chest straps in an “x” like pattern; which, as stated earlier, could further reduce pulmonary compliance in the steep Trendelenburg position with pneumoperitoneum.9, 10 Some centers place the patient on an egg–crate foam mattress that is secured by tape to the operating room table.3 In this author’s institution our technique is place the patients legs in padded boot stirrups for lithotomy, tuck the arms into the patient’s side with foam rolls in the palms of their hands, and use horseshoe shaped shoulder braces carefully positioned over the acromioclavicular joint. This avoids compression of the upper trunk of the brachial plexus against the first rib and/or depressing the humerus into the axilla and stretching the plexus across it.9, 50 Because of the limited access and duration of the procedure, careful attention should also be given to pressure areas of the arms and legs in order to avoid ulnar neuropathy and lateral femoral cutaneous nerve injury.10 Ventilation As pneumoperitoneum is induced and intraabdominal pressure increases, so will the patient’s airway pressure. Difficulty in ventilation in patients with chronic obstructive or restrictive pulmonary disease or reactive airways can be expected.3 Different modes of ventilation may have to be trialed to determine which obtains better respiratory mechanics and gas exchange. Peak inspiratory pressures in excess of 50-60 cmH2O may result in barotrauma.51 This author prefers using the relatively newer mode of pressure control-volume guaranteed ventilation (PC-VG). In the PC-VG mode the ventilator functions as a pressure control ventilator, but tidal volume is also set. The advantage of this mode is the combination of the decelerating inspiratory flow pattern of the pressure-control mode and control of arterial CO2 via guarantee of tidal volume and ultimately minute volume. This results in peak inspiratory pressures being lower in PC-VG mode than volume-control ventilation.52 Fluid management Intraoperative intravenous should be kept to a minimum (