Pneumatic tourniquet application and nerve integrity: motor function and electrophysiology.

Limb motor function, leg girth, spontaneous potentials, and compound muscle action potentials were evaluated in a rat animal model at various times after tourniquet application and occlusion of blood flow to the sciatic nerve. The thighs of the animals were compressed by a pneumatic tourniquet at clinically relevant pressures (200, 300, and 400 mm Hg) for 1 to 3 h. Extrinsic blood supply was occluded by ligation of the common iliac and femoral arteries and intrinsic by removing a 12-mm segment of the epineurium from the sciatic nerve. Motor function deficits were noted for 1 to 5 weeks in limbs of animals subjected to tourniquet compression and from 2 to 4 weeks following vascular manipulation. Control leg girths did not change during the experiment whereas girths of tourniquet-compressed legs increased initially and then decreased and remained below control values. Girths of limbs subjected to vascular manipulation were unaltered during the 1st week but decreased in a similar fashion to those of tourniquet-compressed limbs at 3 and 6 weeks. Spontaneous potentials were present and compound muscle action potentials were reduced in animals after tourniquet application and vascular manipulation compared with control values. These electrical abnormalities were most pronounced 1 week after the treatments, progressed toward normalcy during the course of the experiment, but failed to attain control values at the termination of the study. Analysis of electrophysiologic data indicated that magnitude of pressure and duration of compression-produced nerve injury occurred independently in an additive fashion.