Effect of different cuff widths on the motor nerve conduction of the median nerve: an experimental study

Abstract

Background: A bloodless operative field is considered mandatory for most surgical procedures on the upper and lower extremity. This is accomplished by using either an Esmarch bandage or a pneumatic tourniquet, but a number of complications are associated with both. Nerve palsy is one of the most frequently encountered complications of this procedure. Wider cuffs have been found to cause reduced risk of tourniquet induced injury to the underlying soft tissues than the narrower ones due to the fact that lower occlusion pressures are caused by the former. To address and investigate this question, conduction in the median nerve has been measured proximal to tourniquet as well as distal to the tourniquet. Parameters of nerve conduction measured are nerve conduction velocity, latency and amplitude.

Methods: Sphygmomanometer cuffs with widths 14 cm and 7 cm were applied to the upper extremities of 20 healthy, normotensive volunteers (9 males and 11 females with age ranging from 22 to 27). Systolic blood pressure was measured first and then the cuff was inflated to about 20-30 mm Hg above it and was kept inflated for 15 minutes. Recordings were done prior to, for the period of tourniquet inflation, and following release of the tourniquet.

Results: Nerve conduction was found to be more severely affected by the 14 cm cuff than the 7 cm cuff.

Conclusion: Wider cuffs resulted in more severe changes in the nerve. This brings us to the conclusion that though lower inflation pressures are required for the occlusion of the blood supply using wider cuffs, the nerve conduction is more severely affected by the wider ones. Both electrophysiological changes and occlusion pressure should be kept in mind while choosing the width of the cuff.

Figures

Figure 1

Mean values of the percentage MNCV at different time durations before and following the application of the 14 cm and 7 cm cuff. A decrease in MNCV is evident following application of both cuffs but as can be clearly seen that this decrease is more with the 14 cm cuff after 15 minutes of inflation of the cuff.

Figure 2

Plot of increase in the percentage latency measured proximal to the two cuffs with the wider cuff (14 cm) showing greater increase in the same during the 15 minutes of inflation of 14 cm cuff in comparison to the narrower one (7 cm).

Figure 3

Figure showing the percentage amplitude change measured proximal to the two cuffs during the 15 minutes of inflation of the cuffs. The graph shows no definite pattern being followed by either of the two cuffs.