Anesthesiology

Patient Positioning During Anesthesia: Robotic Surgery and Other Advanced Technology

Patient transfer

Prior to achieving any surgical position, the patient must be transferred onto the operating room table. The final position of the patient is of the utmost importance, but achieving these positions requires careful planning and coordination by the operating room team. The overall plan for each patient transfer should be discussed prior to any movement.

Frequently, the patient can assist in positioning prior to induction of anesthesia. However, under general anesthesia, the operating room team must carefully move and position each patient. Pertinent patient comorbidities should be reviewed. For example, patients with morbid obesity or unstable spine fractures will require additional staff for transfer and positioning. When the patient is moved after the induction of general anesthesia, the anesthesiologist must be aware of any blood pressure alterations and ensure a safe systemic blood pressure prior to any patient movement.

All monitors, intravenous lines, and the endotracheal tube need to be carefully managed when moving a patient. The eyes should be taped to avoid corneal abrasion. With excellent communication, patients can be safely and successfully transferred within the operating room.

Robotic surgery and other advanced technology

Robotic surgery is increasing in popularity, providing novel, minimally invasive approaches to common surgical procedures. Robot-assisted surgery touts improvements in intraoperative visualization, surgical dexterity, postoperative pain, wound infections, and decreased length of hospital stay as advantages over traditional laparoscopic and open surgery.

What common procedures are performed in this position?

Robotic surgery is being performed for many surgical procedures, most commonly during prostatectomy. Other procedures performed using robotic techniques include thyroidectomy, gynecological procedures, colorectal procedures, transoral robotic surgery (TORS), cardiac surgery, thoracic surgery, and renal surgery, including nephrectomy and cystectomy.

What are the common variations of this position?

With the advent of robotic surgery and other advances in surgical care, new patient positions must be adapted to allow for adequate operative visualization. Complex surgical systems with varying approaches to the patient will dictate the exact position of the patient, but as stated previously this must be balanced against the risk to the patient.

Although robotic surgery is often performed in conventional positions as previously reviewed, some procedures require extremes of these positions. For example, robotic-assisted laparoscopic radical prostatectomy requires the patient to be in lithotomy with steep Trendelenburg, but in robot-assisted gastrectomy varying degrees of reverse Trendelenburg must be maintained. Other procedures including thoracic surgery require varying degrees of the lateral decubitus position.

What are the physiologic changes when placing a patient in this position?

Physiologic changes related to positioning in robotic-assisted surgery often present as exaggerations of common physiologic changes seen during nonrobotic-assisted surgery. The addition of CO2 pneumoperitoneum can amplify these changes.

Within the respiratory system, steep Trendelenburg and pneumoperitoneum decrease functional residual capacity (FRC) and lung compliance via encroachment of the abdominal cavity onto the diaphragm. This position increases the risk of V/Q mismatch. When placed in the steep Trendelenburg position, the functional length of the trachea decreases by 1 cm, possibly leading to right mainstem intubation and hypoxia after the patient is positioned.

Also, extremes of position can alter basic cardiovascular physiology. For example, steep Trendelenburg position can increase central venous pressure, pulmonary artery pressure, and pulmonary capillary wedge pressure. The Trendelenburg position alone may increase cardiac output secondary to an increased venous return. However, the addition of pneumoperitoneum used during robotic surgery will increase systemic vascular resistance (SVR), potentially decreasing cardiac output during robotic-assisted surgery.

Conversely, steep reverse Trendelenburg can lead to hypotension via decreased venous return to the heart. The patient’s blood pressure must be careful maintained in this position to allow adequate cerebral perfusion and adjustment of arterial line transducers should be considered. Additionally, positioning during robotic surgery can alter intraocular and intracranial pressure. These both will increase in the steep Trendelenburg position, but typically within normal limits and have been tolerated by healthy patients.

Not only does pneumoperitoneum insufflation affect hemodynamics as previously described, insufflation within the thoracic cavity also can lead to hypotension via obstructing venous return. This is also exaggerated by placing the patient in the lateral decubitus position with an overall head up position.

What are the options for anesthetic management?

Nearly all procedures performed using advanced robotic systems demand general endotracheal anesthesia with continued neuromuscular blockade. After induction of anesthesia and tracheal intubation, the patient should be positioned as determined by the demands of the surgical procedure. Prior to positioning the robotic system, all additional intravenous access and invasive monitoring devices should be obtained. These should all be checked and secured prior to moving and positioning the patient.

Once the procedure has begun, there will be limited access to these devices. During the operation, any unanticipated patient movement could cause serious harm due to the many relatively immobile robotic arms entering the patient. For this reason, neuromuscular blockade is recommended throughout the procedure to maintain patient immobility.

Additionally, the robotic system and type of surgery being performed often dictate a new physical location for the anesthesiologist to monitor the patient. Instead of the classic position at the head of the bed, the anesthesiologist might be stationed at the side or even at the foot of the bed with the robotic system positioned above the head of the patient.

While the robot is docked, the anesthesiologist has limited access to the patient. In emergent situations such as cardiac arrest or a lost airway, the robot will have to be moved to allow access for intervention and resuscitation. Creating an emergency plan for moving the robot should be discussed and agreed upon prior to every anesthetic induction.

What complications are associated with this position?

The robotic system is typically composed of several parts including a surgical cart that remains close to the patient. The workable devices are attached to this cart and are inserted into the patient. Careful attention must be paid to the cart as well as to the robot arms so that they do not injure the patient. This includes inadvertent crush and pressure injuries. Specific to TORS, external pressure on the eyes and teeth should be avoided using goggles and dental guards, respectively.

The extreme and often steeper positions put the patient at risk of sliding off the operating table. As previously stated, the use of shoulder braces should be avoided due to their increased risk of brachial plexus injury. If they are placed too medially, they can compress the brachial plexus nerve roots and if placed too laterally they can create stretch due to the force on the shoulder.

Beanbags used to restrain the patient in the steep Trendelenburg position are also not recommended secondary to increased brachial plexus injury. A non-sliding mattress can assist in supporting a patient in this position. Additionally, steep Trendelenburg position increases the risk of ION via similar mechanisms as in the prone position.

What strategies can be used to decrease the risk of injury in this position?

Unique injuries related to positioning in robotic surgery are typically related to the steep positions deemed necessary for adequate surgical exposure. In steep positions of sometimes up to 45 degrees, the patient must be secured to the operating room table. Use of chest banding or belts appears to be favored rather than shoulder bracing and the accompanying increased risk of brachial plexus injuries.

Careful attention must be paid to all external robotic equipment. Any potential site of injury should be padded or protected. This includes goggles to cover and protect the eyes. With the expansion of robotic surgery and newer technologies, the anesthesiologist must continue to assess any position- or equipment-related injury risk to the patient.

What's the Evidence?

Cassorla, L, Lee, JW. "Patient positioning and associated risks". Miller’s Anesthesia. vol. 41. 2015. pp. 1240-65.

(Book chapter on patient positioning in the operating room.)

Cheney, FW, Domino, KB, Caplan, RA, Posner, KL. "Nerve Injury Associated with Anesthesia". Anesthesiology. vol. 90. 1999. pp. 1062-69.

(Closed claims database evaluation of anesthesia-related nerve injury.)

Coonan, TJ, Hope, CE. "Cardio-respiratory effects of change of body position". Can Anaesth Soc J. vol. 30. 1983. pp. 424-37.

(Basic physiology of many common surgical positions.)

Dunn, PF. "Physiology of the lateral decubitus position and one-lung ventilation". Int Anesthesiol Clin. vol. 38. 2000. pp. 25-53.

(A detailed description of ventilation and perfusion mismatch in the lateral decubitus position.)

Edgecombe, H, Carter, K, Yarrow, S. "Anaesthesia in the prone position". Br J Anaesth. vol. 100. 2008. pp. 165-83.

(Comprehensive and in depth review of the prone position.)

Gale, T, Leslie, K. "Anaesthesia for neurosurgery in the sitting position". J Clin Neurosci. vol. 11. 2004. pp. 693-6.

(Review of the sitting position and discussion of venous air embolism.)

Higuchi, H, Takagi, S, Zhang, K, Furui, I, Ozaki, M. "Effect of lateral tilt angle on the volume of the abdominal aorta and inferior vena cava in pregnant and nonpregnant women determined by magnetic resonance imaging". Anesthesiology. vol. 122. 2015. pp. 286-93.

(Discussion of aortocaval compression in the parturient and the effects of various degrees of left lateral tilt in the supine position.)

Knight, DJW, Mahajan, RP. "Patient position in anaesthesia". Continuing Education in Anaesthesia, Critical Care & Pain. vol. 4. 2004. pp. 160-3.

(Brief overview of patient position during anesthesia.)

Koh, JL, Levin, SD, Chehab, EL, Murphy, GS. "Neer Award 2012: Cerebral oxygenation in the beach chair position: a prospective study on the effect of general anesthesia compared with regional anesthesia and sedation". J Shoulder Elbow Surg. vol. 22. 2013. pp. 1325-31.

(A prospective study suggesting the possible benefits of avoidance of general anesthesia in the BCP.)

Lee, JR. "Anesthetic considerations for robotic surgery". Korean J Anesthesiol. vol. 66. 2014. pp. 3-11.

(An update and review of robotic surgery including a detailed discussion on the anesthetic implications of many common robotic surgeries.)

Lohser, J. "Evidence-based management of one-lung ventilation". Anesthesiol Clin. vol. 26. 2008. pp. 241-72.

(Ventilation and perfusion in the lateral decubitus position with further discussion of one-lung ventilation management.)

Murphy, GS, Szokol, JW. "Blood pressure management during beach chair position shoulder surgery: what do we know?". Can J Anesth. vol. 58. 2011. pp. 977-82.

(Brief discussion of the beach chair position and intraoperative blood pressure management.)

Picton, P, Dering, A, Alexander, A, Neff, M, Miller, BS, Shanks, A, Housey, M, Mashour, GA. "Influence of ventilation strategies and anesthetic techniques on regional cerebral oximetry in the beach chair position". Anesthesiology. vol. 123. 2015. pp. 765-74.

(Prospective study showing that increasing the inspired oxygen fraction and end-tidal carbon dioxide during general anesthesia increases regional cerebral oxygenation in the BCP.)

Prielipp, RC, Morell, RC, Butterworth, J. "Ulnar nerve injury and perioperative arm positioning". Anesthesiol Clin NA. vol. 20. 2002. pp. 589-603.

(Review of perioperative ulnar neuropathy including anatomy, risk factors, and legal implications.)

Rains, DD, Rooke, GA, Wahl, CJ. "Pathomechanisms and complications related to patient positioning and anesthesia during shoulder arthroscopy". Arthroscopy. vol. 27. 2011. pp. 532-41.

(Discussion of anesthetic options and positioning during shoulder arthroscopy.)

Roth, S. "Perioperative visual loss: what do we know, what can we do?". Br J Anaesth. vol. 103. 2009. pp. i31-i40.

(Review of perioperative visual loss including updates on risks factors and preventative recommendations.)

Washington, SJ, Smurthwaite, GJ. "Positioning the surgical patient". Anaesth Intens Care. vol. 10. 2009. pp. 476-9.

(Brief overview of patient position during anesthesia.)

Winfree, CJ, Kline, DG. "Intraoperative positioning nerve injuries". Surg Neurol. vol. 63. 2005. pp. 5-18.

(Comprehensive review of position related nerve injuries.)
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