Measurement of forearm oxygen consumption: role of heating the contralateral hand.

The classical forearm technique widely used for studies of skeletal muscle metabolism requires arterial cannulation. To avoid arterial puncture it is becoming more common to arterialize blood from a contralateral hand vein by local heating. This modification and the classical method have produced contradictory results regarding the contribution of skeletal muscle to glucose-induced thermogenesis. The effect on forearm circulation and the metabolism of heating the contralateral hand was examined before and after an oral glucose load. The results suggest that contralateral heating increases subcutaneous blood flow and decreases skeletal muscle blood flow. This facilitates mixing of superficial blood with deep venous blood. Contralateral heating increased deep venous oxygen saturation and abolished the pronounced glucose-induced increase in oxygen consumption observed in the control experiments after glucose. Heating increased rectal temperature by 0.6 degrees C, and plasma norepinephrine levels were increased compared with the control experiments. The present study explains the conflicting reports on glucose-induced thermogenesis in skeletal muscle and warns against heating the contralateral hand when using the forearm technique.