DOSE-RESPONSE CHARACTERISTICS OF ISOFLURANE ON PLASMA GLUCOSE CONCENTRATIONS

Abstract: Purpose: The dose-dependent effects of isoflurane anesthesia on insulin inhibition and insulin resistance were compared in rats. Methods: Three rats were entered into the procedure with each rat being subjected to 3 different doses of steady state concentrations of isoflurane (1.75%, 2.0%, and 2.50%). A surgical plane of anesthesia was induced by continuous infusion of isoflurane via an induction box at 4.0% isoflurane and when anesthesia was achieved the infusion of anesthesia was lowered to the steady state concentrations of isoflurane. Plasma glucose concentrations were measured every 10 minutes until two or three consistent peak values were observed. After assurance of reaching peak values sub-cutaneous insulin (0.75 units/kg) was injected between the scapulas. Following the insulin injection plasma glucose concentrations were obtained every 10 minutes via pinprick until peak minimal glucose values were reached. If the plasma glucose of any animal reached a level approximately 50 mg/dL, subcutaneous glucose was injected (2.0 grams/kg) to prevent adverse effects of hypoglycemia. Results: For absolute plasma glucose post-anesthetic values a comparison of multiple mean glucose concentrations (single factor ANOVA) yielded p=8.06 x 10-6. A post-hoc analysis revealed significant p values between 3 pairs of means: 1.75%/2.0%= 0.004; 1.75%/2.5%= 0.03; 2.0%/2.5%= 0.02 . For normalized plasma glucose values post-anesthetic a comparison of multiple means (ANOVA) yielded a p value of 0.03. Post-hoc analysis indicated that the peak response was at 2.0% with significant difference between 1.75%/2.0% =0.03 and 2.0%/2.5%=0.02. There was no significance between glucose values 1.75%/2.50%=0.68. For plasma glucose values post-insulin both absolute and normalized a mean comparison analysis (ANOVA) concluded that during post insulin the data was not statistically significant as p=0.68. Conclusions: When absolute plasma glucose concentrations were normalized by the baseline taken at conscious state the dose-dependency disappeared and concluded the largest change in plasma glucose at 2.0%. Although the data post-insulin injection was not statistically significant it can be concluded that there was normal glucose uptake and that there was no impaired insulin action on the skeletal muscle.