Anesthesiology

Patient Positioning During Anesthesia: Lateral Decubitus

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.

Lateral decubitus

Placing the anesthetized patient in the lateral decubitus position should be accomplished as a coordinated effort performed by the operating room team. For patients undergoing procedures using general anesthesia, induction should occur in the supine position and after tracheal intubation the patient placed into the lateral decubitus position. Once in the lateral decubitus position, various devices including a deflatable beanbag or hip bolster support the patient both anteriorly and posteriorly. A pillow is typically placed between the legs to protect the bony prominences of the knees and the dependent leg is placed in a flexed position.

Careful attention must be paid to arm position. The down arm is either placed on an arm board or rested on the procedure table. The nondependent arm can be supported on pillows or special holders that attach to the operating room table. The head and neck should be maintained neutral.

Careful attention must be paid to the dependent eye to avoid external pressure.

The dependent ear needs to be checked to avoid bending and ischemia.

In order to avoid compression on the axillary vessels or the brachial plexus, an axillary roll must be placed between the chest wall and operating room table caudal to the axilla. The axillary roll is typically fashioned from an intravenous fluid bag.

When using a beanbag, an axillary role is not necessary as long as the beanbag is not compressing the axilla.

The position of the patient must be continuously checked and reevaluated throughout the procedure.

What common procedures are performed in this position?

The lateral decubitus position provides surgical exposure to the chest, retroperitoneum, hip, and lateral leg. Common procedures performed in this position include procedures on the lung, aorta, kidney, and hip.

What are the common variations of this position?

Once the patient is in the lateral position, the operating room table can be flexed or the kidney rest can be raised in an attempt to improve surgical access to the retroperitoneum or expand the thoracic cage.

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

Placing a patient in the lateral decubitus position alters normal physiology. Most importantly, the respiratory system undergoes alterations in ventilation and pulmonary perfusion, resulting in ventilation and perfusion (V/Q) mismatch. Further alterations occur when opening the chest and instituting one lung ventilation. Further discussion of one-lung ventilation is detailed elsewhere.

Ventilation

In the awake, spontaneously breathing patient, the dependent portion of each lung is preferentially ventilated in the erect, supine, and lateral position. This phenomenon is explained by the compliance curve of the lung and the position of each segment on that curve. However, with the induction and maintenance of anesthesia in the lateral position, ventilation favors the nondependent lung. In fact, 55% of each tidal volume is delivered preferentially to the nondependent lung.

Compression of the dependent lung by the mediastinum and transmitted pressure from the abdominal organs causes a decrease in functional residual capacity (FRC) and decreased compliance. The decrease in FRC is not consistent throughout both lungs. In fact, the nondependent lung has increased compliance and FRC compared to the dependent lung. Opening of the chest further compromises ventilation to the dependent lung by allowing the mediastinum to shift and further compress the dependent lung.

Gravity affects ventilation in the spontaneously breathing patient, but under anesthesia and positive pressure ventilation, gravitational forces do not seem to influence ventilation.

Pulmonary perfusion

Pulmonary blood flow is determined by three main components including hypoxic pulmonary vasoconstriction (HPV), gravity, and gravity independent factors. A full discussion of pulmonary perfusion is beyond the scope of this chapter. Further discussion here will specifically evaluate the influence of patient position on pulmonary perfusion.

Pulmonary blood flow is not uniform throughout the lung. Classic teaching emphasized the role of gravity on the distribution of pulmonary blood flow. West zones were described as vertical segments within the lung of varying combinations of ventilation and perfusion, explaining V/Q mismatch. Thus, patient position influenced regional lung perfusion based on gravity. In the lateral decubitus position, the dependent lung would receive greater blood flow compared to the nondependent lung.

This theory of regional blood flow is supported in the literature, but only appears to partially explain regional lung perfusion. Recent work has added to the theory of pulmonary perfusion, emphasizing the importance of nongravitational forces. This work describes central-to-peripheral perfusion gradients often compared to the layers of an onion. This model describes increased perfusion at the hilum of the lung, with decreasing flow toward the periphery.

Overall, pulmonary blood flow is the combination of both gravitational and nongravitational factors as well as the effects of HPV.

In the lateral decubitus position during positive pressure ventilation of both lungs, pulmonary blood flow is greater to the dependent lung, whereas the nondependent lung receives preferential ventilation. This leads to a predictable V/Q mismatch.

What are the options for anesthetic management?

Anesthetic management in the lateral decubitus position depends on the specifics of the surgical case. For example, total hip arthroplasty can be performed with neuraxial or general anesthesia. Thoracic surgery most often needs general endotracheal anesthesia.

What complications are associated with this position?

Complications in the lateral decubitus position are similar to those previously discussed.

Arm position needs to be carefully evaluated and maintained throughout the procedure. The basic principles previously discussed, including limiting excessive abduction or extension of the arms, should be continued in the lateral decubitus position.

Brachial plexus injuries have been reported of both the dependent and nondependent arm.

The dependent eye should be routinely checked throughout the procedure to assess for any external compression. A detailed discussion of perioperative visual loss can be found in the section on prone positioning.

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

Positioning an intubated patient in the lateral decubitus position should be performed as a coordinated effort among the operating room team.

Careful attention must be paid to any intravenous access, invasive monitoring devices, and the endotracheal tube to avoid accidental removal. The arms should be positioned with the basic positioning principles already discussed, avoiding excess abduction, flexion, or extension.

All pressure points should be padded, paying careful attention to the bony prominences of the arms and legs.

The dependent ear and eye must be checked and continuously surveyed throughout the operation to avoid any undo pressure and ischemia.

If a kidney rest is elevated to expand access to the retroperitoneal structures, it should not compress the abdomen and cause IVC obstruction, but rather be placed at the bony iliac crest.

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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