In recent years, perioperative neuropathies (nerve injury), soft tissue injuries, and other positioning-related problems have received increasing attention from the lay press, plaintiffs’ lawyers, the anesthesiology community, and clinical researchers. This chapter provides an update of current findings and discusses possible mechanisms of injury for these potentially devastating problems.

Patients in the operating room are at risk for injuries due to positioning on surgical tables. The goal of intraoperative positioning is to place and secure the patient on the operating room table to allow adequate surgical exposure and access, without compromising physiologic function (e.g., ventilation) or injuring the patient. Patient positioning is a routine function of operating room nursing personnel and the anesthesia team; however, all members of the operating room team may be involved in positioning a patient, including the anesthesia technician. For example, an anesthesia technician may place a wrist device for securing an arterial line that has the potential to overextend the wrist and places tension on the nerves.

Patients can be injured in multiple ways due to positioning on the operating room table. Injuries attributable to patient positioning include vision loss, abrasions, skin breakdown, pressure ulcers, hair loss, nerve damage, and joint damage. The mechanisms by which patients sustain injuries include pressure, friction, and shear forces. Forces that compress the skin and underlying tissues can compromise blood flow to important structures, particularly nerves. Normal capillaries have a pressure of between 23 and 33 mm Hg. Supine patients on a hard surface routinely have pressures greater than capillary pressure at points that contact the table, including the back of the head (occiput), the heels, the arms, and the sacrum. Awake patients who do not have mobility problems frequently change position when they become uncomfortable, thus preventing pressure-related injuries. Unfortunately, patients with regional or general anesthesia are either unable to move or may not have intact sensation to know that an area is being injured and they will not move to relieve the compression. Pressure injuries usually occur where tissue is compressed against a bony prominence or the tissue is at special risk (e.g., the eye). The operating room team must take great care to assure that undue pressure is not placed on any portion of the body. Even things as simple as face masks or intravenous (IV) poles can be placed in such a way as to place pressure on the body and injure a patient. Patients with compromised blood flow to tissue are at an increased risk for pressure injuries, especially those with diabetes or peripheral vascular disease. Other patient factors that increase the risk of nerve injury include thin patients (tissues have less padding from muscle mass or fat), the elderly, and the malnourished.

Friction or shear forces can also cause injury to patients. When skin rubs against a surface, it can sustain an abrasion or a burn-like injury that blisters. You might think that anesthetized patients are immobile and most of the time they are; however, the surgical team may repeatedly move the patient to facilitate surgical exposure.
For example, during total knee replacement surgery, the operative knee is flexed and extended multiple times. Movement of one portion of the body can move other portions of the body, or even the entire body. This movement can cause the skin to rub against some portion of the operating room table or attached equipment. Alternatively, the operating team may move equipment that may rub against the patient.

Another mechanism of injury due to positioning involves the overextension of joints. Each individual joint in each individual patient has a range of motion through which the joint may comfortably move. Overextending a joint can damage the joint capsule and ligaments or tendons that surround the joint. Many common sports injuries like sprains involve the overextension of joints. When a joint is overextended, it is painful. In the operating room, an anesthetized patient will not be able to tell the operating room staff that a joint is overextended. As a patient is moved from one bed to another, positioned on the table, or moved during surgery to facilitate surgical exposure, the patient is at risk for a joint injury. During these movements, the operating room staff must take care to keep joints in a neutral position that is well within the joint’s normal range of motion. For example, an anesthetized patient is positioned in the lithotomy position with his or her arms extended on arm boards for surgery. In this position, the hips may be externally rotated. The operating room staff must make sure that as the joints are moved and reach their final position, they are not overextended. The hips could be injured if they were rotated too far, and the shoulders could be injured if the arms were extended away from the body more than 90 degrees.

It is important to keep in mind that some patients, due to disease or previous injury, may have a reduced range of motion in a joint. These limitations should be identified preoperatively so that the operating room staff can avoid extending the joint beyond its reduced range of motion. For example, normal patients can tolerate a shoulder extended by an arm moved away from the body up to 90 degrees. However, a patient with an old shoulder injury may not be able to tolerate having his or her arm moved more than 45 degrees away from his or her body.

Even if joints are properly positioned at the beginning of surgery, they may be injured later during the surgery if they are moved to facilitate surgical exposure or they later become malpositioned or fall off the operating room table. The patient should be secured to the operating room table to prevent limbs or even the entire patient from falling off the table. Keep in mind that the restraints must be applied in such a way as to prevent movement but also to not improperly compress a body part.

Nerves are at particular risk for positioning injury during surgery. The injury is usually the result of stretching the nerve or prolonged compression, both of which compromise blood flow to the nerve. Both the amount of stretch or compression and the duration of the insult are determinants of the extent of injury. In addition, longer nerves seem to be more prone to injury. Other risk factors for nerve injury include nerves with an existing problem or medical conditions that can compromise blood flow. Nerve injury (neuropathy) can range from minor sensory changes (tingling or numbness) to severe injuries including paralysis. Minor injuries tend to resolve over time (<6 months); however, many injuries are permanent, resulting in lifelong pain or altered sensation, or even paralysis.

Nerve stretch is usually the result of body parts, usually extremities, placed in extreme positions. Arms or legs can be easily overextended with the good intention of improving surgical exposure. In other circumstances as mentioned above, a body part falls off of the operating room table (e.g., a leg or arm can easily fall off the table or an arm board). The extreme position of the extremity may not be recognized because of drapes covering the patient. On some occasions, movement of one part of the body may stretch another part, particularly if that part is secured to the table. For example, the surgical team may be tugging on an arm to improve surgical exposure, which ends up moving the patient’s torso. If the patient’s head was secured to the table, the movement of the torso could put the neck in an abnormal position. Throughout a surgery, the operating room staff should periodically check to make sure that equipment, body parts, and restraints have not moved in such a way as to injure the patient.

The most common source of nerve compression is inadequate padding of body parts that come into contact with the operating room table.
The majority of operating room tables are covered with padded material to reduce the risk of pressure injuries. Even so, the majority of operating rooms apply additional padding to the arms, legs, heels, and head. Special care needs to be taken to ensure that any additional operating room equipment does not press on any part of the patient. It is easy for an improperly positioned mayo stand, IV pole, or even the surgeon leaning against a body part to cause nerve compression. As with nerve stretch, inadvertent changes in patient position can lead to nerve compression that may go unrecognized for prolonged periods due to surgical draping. For example, a leg that has fallen partially off the table may be resting directly upon metal or some other unpadded portion of the table or operating room equipment. Another source of nerve compression, although not a positioning problem, can arise from excessive tissue pressure. For example, a crush injury or an infiltrated IV line can lead to swelling of an extremity that compromises blood flow to the extremity. The remainder of this chapter will look closely at particular nerves and their risk for positioning injuries.