The Effects of Intravenous Insulin on Hemodynamics and Autonomic Nervous System Activity in Anesthetized Dogs / 대한마취과학회지

ABSTRACT

BACKGROUND: Even though the cardiovascular actions of insulin were first described shortly after introduction into clinical practice, the precise physiological role and mechanism of insulin-mediated cardiovascular actions are not known. The aim of the present study was to investigate the changes in hemodynamics after an insulin injection and the role of the autonomic nervous system in mediating the responses to insulin. METHODS: Nine mongrel dogs of the male sex, weighing 20 - 26 kg, were studied. Anesthesia was maintained with pentobarbital and vecuronium after the administration of the loading dose. Femoral and pulmonary artery catheters were placed for obtaining blood samples (ABGA, electrolytes, glucose and plasma catecholamines) and measuring hemodynamic variables. Real time power spectral analysis of R-R interval variability was displayed on the color power spectrum every 30 seconds by a simple connection between the EKG monitor and computer via an A/D converter. After control values were obtained, porcine insulin was administrated intravenously as a bolus injection (2 U/kg). Blood glucose and potassium were maintained within physiological range by simultaneous infusion of 50% glucose (2-4 ml/kg/h) and potassium (0.5-1.0 mEq/kg/h). Parameters were measured respectively in 9 steps; 10min before insulin injection (control), 1, 5, 10, 20, 30, 40, 50 and 60min after insulin injection. RESULTS: Heart rate, mean arterial blood pressure and cardiac output increased and systemic vascular resistance decreased significantly after the insulin injection. No significant changes in plasma norepinephrine and epinephrine levels could be detected. Power spectral density of low frequency and ratio oflow and middle frequency power to high frequency power increased significantly 1min after insulin injection but did not increase thereafter. High frequency power remained significantly below the control value after the insulin injection. CONCLUSIONS: Although catecholamine concentration itself did not show a significant change, PSA data reveals that insulin may exert a stimulatory action on the sympathetic nervous system and a depressive action on the parasympathetic nervous system independent of hypoglycemia immediately after an insulin injection and insulin-induced vasodilation is not related to the autonomic nervous system.