Since the introduction of coronary artery bypass surgery, the skill and techniques of the surgeons and anesthesiologists performing this surgery have increased significantly. However, complications still arise.

One little-discussed complication is injury to the brachial plexus nerves, which should be considered when the patient complains of acute onset of shoulder pain, weakness and/or paralysis following the surgical procedure. The cause of brachial plexus injury remains under discussion (Hudson et al., 1993), and there is much to be learned about its treatment and prevention (Swenson and Bull, 1997). Additionally, because it is difficult to diagnose and assess, it is frequently misdiagnosed in the postoperative period.

The ability to predict such nerve injury during the operation has not been an easy task. Studies are underway to develop devices for monitoring patients, which may be helpful in giving the operating team a better indication of the potential for nerve damage during surgery. Somatosensory evoked potential (SEP) monitoring may reliably predict the potential for peripheral nerve injury (Hallikainen et al., 1993), and intra-operative upper extremity SEPs may be used to predict peripheral nerve damage during surgery (Hickey et al., 1993).

There are also techniques being developed for use during the immediate postoperative period that will help assess a possible injury and give clinicians an earlier opportunity to diagnose and address this problem (Griffin and Wood, 1996). A postoperative electroneuromyography (ENMG) can be very helpful in localizing an acute injury suggesting the damaged areas in the brachial plexus. A concurrent abnormal SEP response can indicate possible additional damage (Hallikainen et al., 1993).

Possible ways of decreasing the incidence of brachial plexus injuries have been explored. For example, Jellish et al. (1997) investigated whether arm positioning during surgery would substantially affect the postoperative pain. They assigned patients to two different groups: One group was placed in the hands up (HU) position, and the other was placed in the arms at side (AAS) position. The study evaluated whether one position was more beneficial in reducing brachial plexus stress during asymmetric sternal retraction. Both groups were evaluated with peri-operative neurologic evaluation of the brachial plexus and SEPs were collected during internal mammary artery harvesting by utilizing the asymmetric sternal retraction technique. Assessment of the two groups was carried out by evaluating postoperative brachial plexus symptoms, SEP changes and demographic data. In 50% of the AAS group and in 35% of the HU group, SEP amplitude decreased substantially (>50%) on the left side. When the asymmetric retractor was removed, amplitude recovery was seen in both groups.

Asymmetric sternal retraction showed minimal benefit in reducing brachial plexus stress as measured by SEP in the HU position. In the AAS group, however, three of seven patients who reported symptoms had an ulnar nerve distribution of injury. This may have indicated that there was a higher incidence of postoperative symptoms caused from ulnar nerve compression, not the brachial plexus, in the AAS group (Jellish et al., 1997).

It is unknown whether certain pre-existing illnesses can be predisposing factors for brachial plexus injury during cardiac surgery. Hallikainen et al. (1993) found that diabetic polyneuropathy seemed to be a predisposing factor and to prolong the duration of disability.

Studies exploring the complications associated with coronary artery bypass surgery have concluded that a prolonged sternal separation may add to the risk of brachial plexus injuries. Another etiologic factor leading to postoperative neurological complications may be a rigorous asymmetrical retraction of the sternal halves during internal mammary harvesting (Lin et al., 2000). These authors called for further investigation to determine if brachial plexus injuries could be significantly reduced by an exact median sternotomy; a lower position; the smallest possible opening for the sternal retraction; and minimal, symmetrical retraction of the lower halves.

An overzealous and rigorous sternal retraction when the chest wall is opened can cause brachial plexus injury (Hudson et al., 1993). If this injury does occur, immediate consultation with arm and hand surgical experts may assist managing any physical events that could result in short- or long-term harm (Doi, 1997).

The compression or overstretching of the nerve complex, as well as the separation of the chest wall during cardiac surgery, may be a factor in subsequent problems (Lin et al., 2000). Several researchers have hypothesized that certain techniques such as proper padding of the upper extremities may substantially reduce postoperative complications (Hudson et al., 1993; Swenson and Bull, 1997). However, actual surgical techniques have not demonstrated this to be the case.

Both external mechanical factors and certain patient characteristics have been noted as possible causes of these postoperative injuries (Stoelting, 1994). Male gender was included as a predisposing cause, implying that certain anatomical predispositions, such as having a shallower cubital tunnel, may lend themselves to a more frequent occurrence of injury in males then in females. In addition, factors such as prolonged flexion of the elbow intra-operatively or in the postoperative convalescence period, alcohol abuse, vitamin deficiencies, and cancer may play a role (Stoelting, 1994).

The pain that occurs in avulsion lesions of the brachial plexus can represent a serious challenge to rehabilitation (Frampton, 1996). Although the mechanism behind this pain is not well-understood, it is clear that careful management and the use of devices, such as a transcutaneous electronic nerve stimulation (TENS) device, can play a significant role in pain relief and rehabilitation after injury.

When a brachial plexus injury does occur, the patient can anticipate a considerable amount of pain and discomfort that may result in a delay in their return to their previous employment (Frampton, 1996). Injuries of this nature may be severe enough to cause the patient's permanent disability. Emotional involvement may become another complication with the emergence of depression and anxiety. Decreasing the incidence of these neuropathies presents a significant challenge.

Dr. Episcopio is a senior attending physician in Internal Medicine at the Lehigh Valley-Muhlenberg Hospital Associations and St. Luke's Hospital in the Lehigh Valley, Pa. He is a Diplomate on both the American Board of Forensic Medicine and the American Board of Forensic Examiners. He maintains an internal medicine practice in Bethlehem, Pa.

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Nerve Damage From Coronary Artery Bypass Surgery Can Affect Arm Functioning