Recovery of nerve conduction after a pneumatic tourniquet: observations on the hind-limb of the baboon

Abstract

SUMMARY A small pneumatic cuff inflated around the knee was used to produce tourniquet paralysis in baboons. A cuff pressure of 1,000 mm Hg maintained for one to three hours produced paralysis of distal muscles lasting up to three months. Nerve conduction studies showed that most of the motor fibres to the abductor hallucis muscle were blocked at the level of the cuff and that they conducted impulses normally in their distal parts. There was a significant correlation between the duration of compression and that of the subsequent conduction block. When tested two to three weeks after the tourniquet, the amplitude of the response of m. abductor hallucis to nerve stimulation distal to the cuff was usually slightly reduced compared with the precompression figure. This was assumed to mean that a small proportion of the motor fibres had undergone Wallerian degeneration as a result of compression. Maximal motor conduction velocity was reduced in recovering nerves. It was also reduced when a cuff pressure of 500 mm Hg was used, which was insufficient to produce persistent conduction block. In such cases a reduced velocity without evidence of block could be demonstrated 24 hours after compression. Ascending nerve action potentials were recorded from the sciatic nerve in the thigh, with stimulation at the ankle. Before compression the fastest afferent fibres had a significantly higher velocity than the fastest motor fibres in the same nerve trunk. Results after compression suggested that the high-velocity afferent fibres had a susceptibility to the procedure similar to that of the fastest motor fibres.In clinical practice, particularly in orthopaedic surgery, it is well recognized that the application of a tourniquet to a limb is sometimes followed by paralysis which may persist for weeks or months. While most of the reports in the literature date from the period when rubber tubing or Esmarch bandages were used (Lejars, 1912;Eckhoff, 1931), occasional examples have been reported after pneumatic tourniquets (Bruner, 1951;Moldaver, 1954 by Denny-Brown and Brenner in 1944. They found that there was local demyelination of nerve fibres under the tourniquet but no loss of axonal continuity through the lesion. The electrical excitability of the motor nerves distal to the tourniquet was preserved, and in most cases power in the affected muscles recovered within a few weeks. Conduction velocity during the recovery period was studied by Mayer and Denny-Brown (1964) who found it to be reduced at the site of the tourniquet compared with the velocity above and below this level.In the present experiments we have reinvestigated the conduction block produced by a tourniquet, with special reference to the timecourse of recovery. In baboons it has been possible to apply a pneumatic cuff rather than the narrower rubber tubing used by Mayer and Denny-Brown in the cat. Recovery in individual 638

The contribution of ischaemia and deformation to the conduction block generated by compression of the cat sciatic nerve

“…This has led to a comprehensive investigation of neuronal compression including histological, electrophysiological and clinical examination of various animal and human models (DennyBrown & Brenner, 1944 a, b;Fullerton & Gilliatt, 1967 a, b;Anderson, Fullerton, Gilliatt & Hern, 1970;Ochoa, Fowler & Gilliatt, 1971Fowler, Danta & Gilliatt, 1972;Ochoa & Marotte, 1973;Gilliatt, 1980;Rydevik & Nordborg, 1980;Gelberman, Hergenroeder, Hargens, Lundborg & Akeson, 1981;Gelberman, Szabo, Williamson, Hargens, Yaru & Minteer-Convery, 1983;Powell & Myers, 1986;Lundborg, 1988;Dahlin, Shyu, Danielsen & Andersson, 1989;Olmarker, 1990). These studies have provided detailed information regarding the changes in nerve structure and function which follow compression, but have left doubts regarding the fundamental causes of such changes.…”

Biceps vs extensor carpi radialis recovery in Frankel grades A and B in spinal cord injury patients

“…Fowler et al suggested that conduction block could be caused by disruption of the nodes of Ranvier due to the pressure gradi ent created in a compression injury. 24 There is a pressure gradient in the nerve between its compressed and uncompressed parts. The compression caused a longitudinal movement of the axon and its myelin from the compression site as well as a disruption of the nodes due to the dislocation of the paranodal myelin with the lesions being concentrated at the edges of the compress ion zone.…”

The Effect of Pneumatic Tourniquets on Skeletal Muscle Physiology

“…More recently (Weingarden et al 1979) EMG abnormalities have been detected in the muscles of patients who had pneumatic tourniquets applied to their limbs during surgery. Fowler et al (1972) have applied tourniquets at a pressure of 1,000 mmHg to the limbs of baboons for periods of 1 to 3 hours. This resulted in a nerve conduction block at the tourniquet application site; however, there was no marked effect on the conduction of impulses in the nerve distal to the site of the tourniquet.…”

“…Paul (1961) found a block in neuromuscular transmission after 13 minutes in a rat muscle nerve preparation subject to anoxia, whilst the muscle fibres of the preparation remained sensitive to direct electrical stimulation for 40 minutes. On release of 3-hour pneumatic tourniquets from baboons a block in nerve conduction has been observed which, in the case of some animals, did not show significant signs of recovery until 6 to 8 weeks had elapsed (Fowler et al 1972). However, there was little change in the conduction capacity of the nerve distal to the tourniquet.…”