Functional changes, such as a reduction in muscle power due to reduced nutrient intake, occur long before demonstrable anthropometric changes and are better predictors of complications than other anthropometric measurements. Therefore muscle function can be considered as a specific measure of the effect of withdrawing nutrients and refeeding. Two methods can be used in critically ill patients, according to their state of consciousness.
1. Assessment of hand-grip strength (of the non-dominant side) with a hand-grip dynamometer is reserved for co-operative patients; it has been shown to correlate with arm muscle circumference and to be the most sensitive test for predicting postoperative complications.
2. Measurement of the contraction of the adductor pollicis muscle in response to an electrical stimulus of the ulnar nerve at the wrist can be performed even in unconscious patients. The combination of an abnormal force-frequency curve and a slow relaxation rate is the most specific and sensitive predictor of nutritionally associated complications in preoperative patients.
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