Oxygen consumption and carbon dioxide elimination after release of unilateral lower limb pneumatic tourniquets

Oxygen consumption (VO2), carbon dioxide elimination (VCO2), and respiratory exchange ratio (RQ) were continuously measured in 15 male and 15 female adults during knee surgery, with the leg exsanguinated by an inflatable tourniquet around the thigh. Arterial blood was also intermittently sampled for blood gas analysis, electrolytes, and lactate content before and after tourniquet deflation. There was a significant increase in VO2 and VCO2 after tourniquet deflation, which was more pronounced in the male (aged 29.5 +/- 14.8 yr, mean +/- SD) than the female (aged 56.9 +/- 15.6 yr) patients, both in terms of maximal increase (P less than 0.001) and percent of increase from values before deflation (P less than 0.001 and P = 0.01). The body weights and tourniquet inflation times were not significantly different between the male and female patients. Excess VO2 (O2 debt) and excess VCO2 over 12 min after deflation of the tourniquet were also significantly higher for male (593.5 +/- 222.9 mL and 714.9 +/- 463.8 mL, respectively) than for female patients (302 +/- 73.3 mL and 196 +/- 162.22 mL, respectively; P less than 0.01). There was no correlation between the duration of tourniquet inflation time and peak increase in VO2, peak increase in VCO2, and O2 debt over 12 min after deflation of the tourniquet; however, tourniquet time was weakly correlated with excess VCO2 over 12 min after tourniquet deflation (r = 0.55, P = 0.002). There was a significant decrease in pHa (P less than 0.001) from release of PaCO2 and lactate after tourniquet deflation. Plasma potassium levels also increased significantly after tourniquet release (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)