The degree of muscular
ischemia and its reversibility can be quantified in the early stages. This histochemical enzymatic study utilized
Nitroblue tetrazolium (NBT) which when reduced by tissue
dehydrogenase produces a blue pigment: "
formazan." Seventy Wistar rats were subjected to transient hindlimb
ischemia by means of a
tourniquet for 3, 6, 9, 12, 15 and 18 hours, followed by reperfusion. Microsurgical muscle biopsies were obtained in each rat at 1 and 12 hours, and 3, 7, 14 days after reperfusion. Time increased in muscle staining demonstrated a succino-
dehydrogenase deficit confirmed by clinical and histopathological follow-up. NBT staining time was 2 minutes (+/- 8 sec.) in the control group, between 2 and 6 minutes in the reversible
ischemia group (rats with 3 and 6 hours of
tourniquet), and more than 9 minutes (+/- 14 sec.) in the irreversible
ischemia group (animals with more than 9 hours of
tourniquet). In
vascular surgery and in limb
reimplantation this protocol is a practical method of evaluating cytoplasmic enzymatic activity and the status of myofibrillar oxidation in the early phases of ischemic injury, before histologic changes are clearly delineated.