Abstract
When the heart stops, arterial pressure decays asymptotically to a value different from the venous pressure. Our study was performed to test the hypothesis that this decay is influenced by vasomotor tone and contains information that could lead to the development of an index of vasomotor tone. Twelve anesthetized dogs were subjected to brief periods of cardiac arrest by stimulating the distal ends of the cut vagi. This was done approximately 9 times in each dog at varying levels of vasomotor tone produced by IV nitroprusside and methoxamine and decay of central aortic pressure was recorded. A mathematical model of the lumped arterial bed was evolved in which each term had recognizable physiologic meaning. Using multiple nonlinear regression analysis, the pressure-time data were fitted to this model and, in most cases, fitted and observed decays were hardly distinguishable to the eye (r2 values were greater than 9). It was predicted that asymptotic pressure, calculated using the model, would rise or fall as vasomotor tone rose or fell. The average asymptotic pressures under the influence of methoxamine were significantly greater (P<.05) than control values and average asymptotic pressures under the influence of nitroprusside were significantly less (P<.05) than average control values. It is suggested that these asymptotes may form the basis for developing an index of vasomotor tone independent of flow measurement.
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Carr, I., Kusnoor, V., Green, M. et al. TOWARDS AN IN VIVO INDEX OF VASOMOTOR TONE INDEPENDENT OF FLOW MEASUREMENT. Pediatr Res 11, 387 (1977). https://doi.org/10.1203/00006450-197704000-00105
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DOI: https://doi.org/10.1203/00006450-197704000-00105
