Handbook of Clinical Anesthesia

Chapter 30

Patient Positioning and Related Injuries

Positioning of a patients for a surgical procedure is frequently a compromise between what the anesthetized patient can tolerate (structurally and physiologically) and what the surgical team requires for anatomic access (Warner MA: Patient positioning and related injuries. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 793–814). There is a lack of solid scientific information on basic mechanisms of position-related complications. Notations about positions used during anesthesia and surgery, as well as brief comments about special protective measures such as eye care and pressure-point padding, are useful information to include in the anesthesia record.

  1. Dorsal Decubitus Positions
  2. Variations of Dorsal Decubitus Positions(Table 30-1)
  3. Complications of Dorsal Decubitus Positions(Table 30-2)
  4. Brachial Plexus and Upper Extremity Injuries (Table 30-3)
  5. Ulnar Neuropathyis characterized by an occurrence predominately in men (70% to 90%), high frequency of contralateral nerve dysfunction (suggesting that many patients have asymptomatic but abnormal ulnar nerves before undergoing anesthesia), and an often delayed appearance of symptoms (48 hours after the surgical procedure).
  6. Elbow flexion (>110 degrees) can cause ulnar nerve damage by compression of the nerve by the aponeurosis of the flexor carpi ulnaris muscle and cubital retinaculum. Conversely, in some patients, the roof of the cubital is poorly formed such that the ulnar nerve s

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ubluxes over the medial epicondyle of the humerus during elbow flexion, producing recurrent mechanical trauma.

Table 30-1 Dorsal Decubitus Positions

SupineHorizontal (the arms are padded and restrained alongside the trunk or abducted on padded arm boards; this does not place the hips and knees in a neutral position, resulting in discomfort for awake patients)
Contoured (the arms are placed as for the horizontal position; the hips and knees are slightly flexed; this is a good position for routine use)
Lateral uterine or abdominal mass displacement (leftward tilt of the table or placement of a wedge under the right hip)
Lithotomy
Standard (the lower extremities are flexed at the hips and knees and simultaneously elevated to expose the perineum; at the end of surgery, both legs are lowered together to minimize torsion stress on the lumbar spine)
Exaggerated (this stresses the lumbar spine and restricts ventilation because of abdominal compression by the thighs)
Head-Down Tilt (this should be avoid in patients with intracranial pathology)
Trendelenburg position (30 to 45 degrees head down; this may require some means of preventing the patient from sliding cephalad; shoulder braces should be avoided if possible; this position should only be used when a unique surgical issue requires it for exposure and only for as long as needed)

  1. External compression in the absence of elbow flexion may occur within the condylar groove or distal to the

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medial epicondyle, where the nerve and its associated artery are relatively superficial.

Table 30-2 Complications of Dorsal Decubitus Positions

Postural hypotension (this is the most common complication of the head-up position; the legs should be lowered simultaneously from the lithotomy position if the patient has hypovolemia)
Pressure alopecia (padded head supports should be used)
Pressure-point reactions (to the heels, elbows, or sacrum; these should be protected against skin and soft tissue compression and ischemia, but there is no evidence that this is beneficial in reducing peripheral neuropathies in the perioperative period)

Table 30-3 Brachial Plexus and Upper Extremity Injuries

Brachial plexus neuropathy (most likely if the head is turned away from an excessively abducted arm; it may be associated with first rib fracture during median sternotomy)
Long thoracic nerve dysfunction (winging of the scapula reflecting serratus anterior muscle dysfunction; a viral origin should be considered)
Axillary trauma from the humeral head (abduction of the arm on an arm board to >90 degrees may thrust the head of the humerus into the axillary neurovascular bundle)
Radial nerve compression (a vertical bar of screen forces the nerve against the humerus; wrist drop)
Ulnar nerve compression (trauma occurs as the nerve passes behind the medial epicondyle of the humerus; sensory loss of the fifth finger and lateral border of the fourth finger may occur)

  1. Anatomic differences between men and women may explain the higher incidence of ulnar nerve neuropathy in men (e.g., the tubercle of the coronoid process is approximately 1.5 times larger in men, men have less adipose tissue over the medial aspect of the elbow, and men have thicker flexor cubital retinacula).
  2. The time of recognition of digital anesthesia associated with ulnar nerve dysfunction may be important in establishing the origin of the postoperative syndrome.
  3. If ulnar hypesthesia or anesthesia is noted promptly after the end of anesthesia (in the postanesthesia care unit [PACU]), it is likely to be associated with events that occurred during anesthesia and surgery.
  4. If recognition is delayed for many hours, the likelihood of cause shifts to postoperative events despite accepted methods of padding and positioning during the intraoperative period.
  5. Opioids may mask dysesthesias and pain after surgery but not loss of sensation caused by nerve dysfunction. It may be helpful to assess ulnar nerve function and record these observations before discharging patients from the PACU.

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Table 30-4 Other Dorsal Decubitus Problems

Arm complications (abduction of the arm to >90 degrees should be avoided to avoid forcing the head of the humerus into the axillary neurovascular bundle)
Lumbar backache (ligamentous relaxation during anesthesia; the lithotomy position worsens pain from a herniated intervertebral disk)
Perineal crush injury (occurs on the fracture table for repair of a fractured hip when the pelvis is retained in place by a vertical pole at the perineum)
Compartment syndrome (characterized by systemic hypotension and impaired perfusion pressure to the legs that is augmented by elevation of the extremities; decompressive fasciotomies are necessary to relieve increased tissue pressure)
Finger injury (occurs when the digits are caught between the leg and thigh sections of the operating table as the leg section is returned to the horizontal position at the termination of an operation performed in the lithotomy position)

III. Other Dorsal Decubitus Problems

(Table 30-4)

  1. Lateral Decubitus Positions
  2. Several positioning concepts should be considered when placing a patient into a lateral decubitus position.
  3. Wrapping the legs and thighs in compressive bandages is commonly used to combat venous pooling.
  4. A small support placed just caudad to the downside axilla (inappropriately called an axillary roll) can be used to lift the thorax to relieve pressure on the axillary neurovascular bundle and prevent decreased blood flow to the arm and hand. This chest support has not been shown to protect against ischemia or nerve damage but may decrease shoulder discomfort after surgery.
  5. Any padding support should be observed periodically to ensure that it does not impinge on the neurovascular structures of the axilla.
  6. Variations of Lateral Decubitus Positions(Table 30-5)
  7. Complications of Lateral Decubitus Positions(Table 30-6)

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Table 30-5 Lateral Decubitus Positions

Standard (Horizontal) Lateral Position
The downside thigh and knee are flexed, and pillows are placed between the legs and under the head to maintain alignment of the cervical and thoracic spines
Flexed Lateral Positions
Lateral jackknife (the downside iliac crest is over the table hinge to allow stretch of the upside flank; venous pooling occurs in the legs)
Kidney (an elevated table rest under the iliac crest further increases lateral flexion to expose the kidney; venous pooling and ventilation-to-perfusion mismatch may occur)

  1. Ventral Decubitus (Prone) Positions
  2. Variations of Ventral Decubitus Positions(Table 30-7)
  3. Complications of Ventral Decubitus Positions(Table 30-8)
  4. Blindness after nonocular surgery may reflect compromise of oxygen delivery to elements of the visual pathway and include ischemic optic neuropathy, retinal artery occlusion, and cortical blindness.
  5. Positioning appears to be a risk factor for some of these events (spine surgery).
  6. Prolonged spine surgery, intraoperative hypotension, and massive blood loss, which may prevent adequate oxygen delivery to the visual apparatus, have been described in patients experiencing visual loss.

Table 30-6 Complications of Lateral Decubitus Positions

Damage to the eyes or ears (pressure should be avoided)
Neck injury (lateral flexion is a risk, especially in patients with arthritis)
Suprascapular nerve injury (placement of a pad caudad to the dependent axilla prevents circumduction of the nerve; injury manifests as diffuse shoulder pain)
Long thoracic nerve dysfunction may reflect lateral flexion of the neck and stretch of the nerve

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Table 30-7 Ventral Decubitus Positions

Full prone (supportive pads should be used under the abdomen)
Prone jackknife
Kneeling

  1. The American Society of Anesthesiologists Task Force on Perioperative Blindness has published an advisory based on a review of cases and the literature (Table 30-9).
  2. Head-Elevated Positions
  3. The sitting position permits improved surgical exposure for surgeries involving the posterior fossa and cervical spine.
  4. Mean arterial pressure should be measured at the level of the circle of Willis (with the transducer placed at the level of the external ear canal) because this site provides an accurate reflection of the perfusion pressure to the brain.
  5. Compressive wraps about the legs decrease pooling of blood in the lower extremities.
  6. Complications of Head-Elevated Positions(Table 30-10)

Table 30-8 Complications of Ventral Decubitus Positions

Damage to the eyes or ears (pressure should be avoided; the use of protective goggles should be considered)
Blindness
Neck injury (an arthritic neck may be best managed in the sagittal plane; head rotation may decrease carotid and vertebral blood flows)
Brachial plexus injuries
Thoracic outlet syndrome (it may be useful to ask patients before surgery if they are able to sleep with their arms elevated overhead)
Breast injuries
Impaired venous return (supportive pads should be used under the abdomen)

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Table 30-9 Summary of Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery

A subset of patients who undergo spine procedures in the supine position under general anesthesia have an increased risk for development of perioperative visual loss. High-risk patients are those who undergo prolonged spine procedures and those who have substantial blood loss.
The anesthesiologist should consider informing high-risk patients that there is a small, unpredictable risk of perioperative blood loss.
Use of deliberate hypotensive techniques during spine surgery has not been shown to be associated with the development of perioperative visual loss.
Colloids should be used along with crystalloids to maintain intravascular volume in patients who have substantial blood loss.
There is no apparent transfusion threshold that would eliminate the risk of perioperative visual loss related to anemia.
High-risk patients should be positioned so that the head is level or higher than the heart when possible. In addition, the head should be maintained in a neutral forward position (without significant neck flexion, extension, lateral flexion, or rotation) when possible.
Consideration should be given to the use of staged spine procedures in high-risk patients.

Table 30-10 Complications of the Sitting Position

Postural hypotension (normal compensatory reflexes are inhibited by anesthesia)
Air embolus (the potential increases with the degree of elevation or the operative site above the heart; air may pass through a probe patent foramen ovale if right atrial pressure exceeds left atrial pressure)
Pneumocephalus
Ocular compression
Edema of the face and tongue
Midcervical tetraplegia
Sciatic nerve injury

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Table 30-11 Summary of American Society of Anesthesiologists' Advisory on Prevention of Peripheral Neuropathies

Preoperative Assessment
When appropriate, it is helpful to determine if the patient can comfortably tolerate the position required for the planned operation.
Upper Extremity Positioning
Arm abduction should be limited to 90 degrees in supine patients.
The arms should be positioned to decrease pressure on the postcondylar groove of the humerus (tucked at the side in a neutral forearm position or abducted on arm boards in either a neutral or supinated forearm position).
Lower Extremity Positioning
Lithotomy positions may stretch the sciatic nerve.
Prolonged pressure on the peroneal nerve at the fibular head should be avoided.
Protective Padding
Padded arm boards may decrease the risk of upper extremity neuropathy.
Padding at the elbow and fibular head may decrease the risk of neuropathies.
Equipment
Properly functioning automatic blood pressure cuffs on the upper arms do not affect the risk of neuropathies.
Shoulder braces in steep head-down positions may increase the risk of brachial plexus neuropathies.
Postoperative Assessment
Assessment of extremity nerve function may lead to early recognition of peripheral neuropathies.
Documentation
Charting specific positioning actions during patient care may result in improvement in care.

VII. Perioperative Peripheral Neuropathies

  1. Prevention(Table 30-11)
  2. Practical Considerations
  3. Padding-Exposed Peripheral Nerves
  4. Many types of padding are available to protect exposed peripheral nerves. There are no data to suggest that one material is more effective than

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another or that any padding is better than no padding.

  1. The goal is to position and pad the exposed peripheral nerves to prevent their stretch beyond normally tolerated limits while awake, avoid direct compression of peripheral nerves if possible, and distribute over as large area as possible any compressive forces that must be placed on the peripheral nerve.
  2. Prolonged Duration in One Position
  3. Prolonged duration in the lithotomy position increases the risk of lower extremity neuropathy.
  4. As much as practical, it may be prudent to limit the time spent in a single position. However, intermittent movement of the limbs or head during the intraoperative period may increase the risk of other problems, including moving an extremity into a suboptimal position.
  5. Course of Action for the Patient with a Neuropathy
  6. Sensory versus Motor Neuropathy
  7. Sensory symptoms are usually transient (many resolve in the first 5 days). Typically, the patient is reassured and advised to avoid postures that might compress or stretch the involved nerve. If symptoms persist, a consultation with a neurologist may be indicated.
  8. If the neuropathy has a motor component, a neurologist should be consulted promptly because electromyographic studies may be needed to assess the location of any acute lesion and to determine the presence of any chronic abnormalities such as in the contralateral but asymptomatic extremity.

Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine

Title: Handbook of Clinical Anesthesia, 6th Edition

Copyright ©2009 Lippincott Williams & Wilkins

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