Chronic cardiac denervation affects the speed of coronary vascular regulation

OBJECTIVE: We tested the hypothesis that the rate of adaptation of coronary metabolic vasodilatation and autoregulation is modulated by the cardiac nerves. METHODS: Anaesthetised dogs (seven innervated (control) and seven with denervated hearts) were subjected to controlled pressure perfusion of the left main coronary artery. Heart rate was controlled by pacing. RESULTS: The steady state autoregulation curves and metabolic regulation curves were similar in the two groups. A sudden increase or decrease in heart rate was associated with a faster response (22% shorter half-times) in the innervated than the denervated dogs (P < 0.001). A sudden increase or decrease in coronary arterial perfusion pressure was associated with a slower response (24% longer half-times) in the innervated than the denervated hearts (P < 0.005). CONCLUSIONS: We conclude that the speed of response to metabolic and perfusion pressure changes is partly mediated by cardio-cardiac reflexes. Reflex coronary vasodilatation appears to reinforce the metabolic vasodilatation of a heart rate increase and oppose the vasoconstriction in response to increased perfusion pressur

Effect of forced-air heaters on perfusion and and temperature distribution during and after open-heart surgery

Objectives: After cardiopulmonary bypass, patients often show redistribution hypothermia, also called afterdrop. Forced-air blankets help to reduce afterdrop. This study explores the effect of forced-air blankets on temperature distribution and peripheral perfusion. The blood perfusion data is used to explain the observed temperature effects and the reduction of the afterdrop. Methods: Fifteen patients were enrolled in a randomised study. In the test group (n = 8), forced-air warmers were used. In the control group (n = 7), only passive insulation was used. Core and skin temperatures and thigh temperatures at 0, 8, 18 and 38 mm depth were measured. Laser Doppler flowmetry (LDF) was used to record skin perfusion from the big toe. Blood flow through the femoral artery was determined with ultrasound. Results: Afterdrop in the test group was smaller than in the control group (1.2 ± 0.2 °C vs 1.8 ± 0.7 °C: P = 0.04) whilst no significant difference in mean tissue thigh temperature was found between the groups. Local skin temperature was 2.5–3.0 °C higher when using forced-air heaters. However, skin perfusion was unaffected. Ultrasound measurements revealed that leg blood flow during the first hours after surgery was reduced to 70% of pre- and peri-operative values. Conclusions: Forced-air blankets reduce afterdrop. However, they do not lead to clinical relevant changes in deep thigh temperature. LDF measurements show that forced-air heating does not improve toe perfusion. The extra heat especially favours core temperature. This is underlined by the decrease in postoperative leg blood flow, suggesting that the majority of the warmed blood leaving the heart flows to core organs and not to the periphery