Effects of Isoflurane and Sevoflurane Anesthesia on Arteriovenous Shunt Flow in the Lower Limb of Diabetic Patients without Autonomic Neuropathy

Background: Failure of sympathetic nerve control caused by diabetic neuropathy results in vasodilation of arteriovenous shunts. The aim of this study was to test the hypothesis that the function of arteriovenous anastomoses was disordered in mild diabetic patients without apparent neuropathy, and that volatile anesthetics opened arteriovenous shunts more greatly in nondiabetic patients than diabetic patients.

Methods: Autonomic system function was assessed by cardiovascular reflex tests. Arterial-venous oxygen content difference (A-VDELTA]O2) and partial oxygen pressure index (Pvo2/Pao2, the ratio of oxygen tension in femoral vein blood to that in femoral artery blood) were measured before and during isoflurane or sevoflurane anesthesia in 16 diabetic and 22 nondiabetic patients. Skin temperatures of the foot and leg were measured in 14 diabetic and 15 nondiabetic patients using thermography before and during anesthesia.

Results: Pvo2/Pao2 before anesthesia was significantly higher in diabetic patients. In nondiabetics, venous oxygen content significantly increased and A-VDELTA]O2 markedly decreased during anesthesia, but these parameters were unchanged in diabetics. Foot temperatures were higher in diabetics before anesthesia, and increased gradually and significantly in both groups during anesthesia, but with a greater increase in nondiabetic patients. Induction of anesthesia caused a larger decrease in leg temperature in diabetics than in nondiabetics.