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Correspondence |
Pavia, Italy
To the Editor:
We present biochemical data relative to skeletal muscle oxidative metabolism of 22 consecutive healthy male patients undergoing anterior cruciate ligament (ACL) reconstruction under tourniquet ischemia. Ten patients were operated under spinal anesthesia (SA) with hyperbaric bupivacaine (SA - age: 24 ± 4 yr; height 177 ± 4 cm; weight 71 ± 9 kg) and 12 under general anesthesia (GA) with sevoflurane (GA - age: 24 ± 5 yr; height 173 ± 8 cm; weight 74 ± 0 kg). The number of subjects included was limited by the modification of the surgical technique subsequent to the onset of the study.
A biopsy was taken from the femoral quadriceps muscle of each patient at three different times: immediately after the induction of anesthesia and ischemia (T1- SA: 6 ± 1 min; GA: 6.4 ± 1 min); at the end of the surgical operation and before the deflation of the tourniquet (T2- SA: 91.8 ± 4.4 min; GA: 90.6 ± 2.8 min) and exactly eight minutes after the deflation of the tourniquet for both groups (T3).
The specific activity of citrate synthase (CS), enzymes of the mitochondrial electron transfer chain1 and manganese-superoxide dismutase (Mn-SOD)2 were evaluated in the mitochondrial fraction; the specific activity of copper, zinc-superoxide dismutase (Cu,Zn-SOD)2 was determined in the crude extract (Table
).
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An unexpected significant increase in the activity of the electron transfer chain enzymes was also observed during ischemia (T2) from the T1 values in both groups of patients. The significant reversal in this increase at T3 suggests the activation of a short-term regulatory mechanism during ischemia.
There were no significant changes in SOD enzyme activities during ischemia and reperfusion. This may be because, at T3, the muscle had not had enough time to produce enough free oxygen radicals to stimulate SOD activity.
The reversal at T3 of the increasing or decreasing tendencies at T2 of CS and electron transfer chain enzyme activities suggests the almost immediate onset of recovery from the combined effects of tourniquet induced ischemia and anesthesia. This should be of interest to orthopedic surgeons and to anesthesiologists.
The few data collected do not permit a firm conclusion on the effects of SA or GA. Since no difference was found between the two anesthetics in their effects on skeletal muscle oxidative metabolism, it may be that the main metabolic effects observed were due to ischemia rather than to anesthesia.
References
1 Pastoris O, Boschi F, Verri M, et al. The effects of aging on enzyme activities and metabolite concentrations in skeletal muscle from sedentary male and female subjects. Exp Gerontol 2000; 35: 95–104.[Medline]
2 Flohe L, Otting F. Superoxide dismutase assays. Methods Enzymol 1984; 105: 93–104.[Medline]
3 Whetzel TP, Stevenson TR, Sharman RB, Carlsen RC. The effect of ischemic preconditioning on the recovery of skeletal muscle following tourniquet ischemia. Plast Reconstr Surg 1997; 100: 1767–75.[Medline]
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