The American Society of Anesthesiologists (ASA) recently released a practice advisory dealing with the issue of perioperative peripheral neuropathies and their prevention. What does it say and what does it mean for you?

What is a practice advisory?
The ASA also releases practice guidelines and standards, so what is the difference between that and an advisory? From the standpoint of the ASA, practice advisories are reports developed to aid in decision-making, rather than to mandate a specific course of action. An advisory is issued rather than a standard or guideline because there is not adequate scientific data to recommend an absolute requirement or practice choice. These advisories are still important - they are developed by the review of existing opinion, available clinical data, open commentary and surveys about consensus practice patterns.

Due to the nature of practice advisories, they are not meant to serve as rigid guidelines, standards of practice or requirements. However, they do try to express the "current state of recommended practice" without guaranteeing that practicing in that way will lead to any specific result.

The ASA makes this clear distinction. As a result, practice advisories should be used to inform the clinician, but not necessarily to change practice. The amount that an individual or institution modifies their practice based on a practice advisory will vary depending on the situation. In many ways, the practice advisory is like a review article and serves and educational purpose.

What does this advisory deal with?
This specific advisory deals with the issue of proper positioning of the patient during surgery in order to prevent nerve injuries. Covered within the document is information about protective padding, the avoidance of pressure caused by hard surfaces, etc. It deals only with adult patients. It does not address neurological problems caused by anesthesia techniques such as regional anesthesia (spinal, epidural, nerve blocks) or other injections.

What does it say?
The task force agreed that a number of things indicate a patient might be more vulnerable to the development of nerve injuries. These things, when elicited during the preoperative evaluation, should alert the practitioner to pay special attention to the issue. These characteristics include:

• Body habitus
• Pre-existing neurological symptoms
• Diabetes
• Peripheral Vascular Disease
• Alcohol dependence
• Arthritis
• Male gender (associated with ulnar nerve problems)

Preventing Ulnar Nerve Injury
The task force goes on to suggest specific information regarding proper positioning. Specifically, they state that arm abduction in the supine patient should be ninety degrees at the most. They did note that the prone position is different and that abduction in the prone position can exceed ninety degrees.

While the data for other positioning practices is less convincing, the advisory does suggest that the arm should be positioned to avoid pressure on the ulnar groove. There seems to be no good data about what amount of arm flexion puts the ulnar nerve at risk.

Other Upper Extremity Nerves
Similarly, pressure on the spiral groove of the humerus should be avoided to protect the radial nerve. The median nerve should be protected by not extending the elbow beyond its normal range of motion.

Lower Extremity Nerves
Positions that stretch the hamstring muscles beyond their normal range of motion should be avoided because this might stretch the sciatic nerve and damage it. In addition, flexion and extension of the hip and knee joints should be considered in positioning because the sciatic nerve crosses both joints.

Hip joint extension and flexion do not seem to affect the risk for femoral nerve injury.

Pressure on the peroneal nerve at the level of the head of the fibula should be minimized. Padding used properly (i.e. not too tight) may help with protection of the peroneal nerve.

Padding
In general, it is unclear how much padding helps. However, the advisory does suggest that upper arms should be padded, chest rolls should be used for lateral positioning and elbows should be protected when possible.

Other Issues
The use of shoulder braces with the patient in a steep head down position can increase the risk of brachial plexus injury.

Clear documentation of what strategies are employed should be made on the chart because it raises awareness of the issue and generates data for future study. In addition, periodic checks of position throughout the operation might be helpful and should be documented when performed.

Should this change your practice?
The actions recommended by the task force may have questionable value and are not clearly supported by the literature. However, none of these suggested actions would result in harm to the patient. In addition, the recommendations of the task force do clearly reflect the consensus of proper practice today.

Reading over the recommendations and the reasoning behind them does serve as an educational exercise for the anesthesia provider. It seems prudent to practice in this manner until there is more data to suggest a change.

The entire practice advisory (as well as other practice advisories, standards and guidelines) can be found at the ASA website at http://www.asahq.org/) - please take a look if you have further interest.