The Influences of Nitric Oxide, Epinephrine, and Dopamine on Vascular Tone: Dose-Response Modeling and Simulations

Abstract

Background: Sodium nitroprusside has successfully been an excellent choice when considering a decrease in systemic vascular resistance in the critical care setting. However, reflex tachycardia and ventilation-perfusion mismatch are possible side effects of this agent. To maintain cardiac output, cerebral perfusion pressure, and concurrently drop systemic vascular resistance (SVR), low-dose epinephrine or dopamine are viable options. The aim of this paper is to conduct dose-response simulations to identify the equivalent dopamine, epinephrine, and nitroprusside infusion doses to decrease the systemic vascular resistance by 20% and by 40% from baseline resting values.

Methods: Three studies were identified in the literature wich reported epinephrine, dopamine, and sodium nitroprusside infusion doses with corresponding systemic vascular resistance responses. Infusion doses were normalized to mcg/kg/min and SVR values were normalized and scaled to the percent decrease (%SVR) in SVR from baseline resting values. The original published studies were mathematically modeled and the Hill equation parameters used for further dose-response simulations of a virtual population. One-hundred patients were simulated various doses resulting in corresponding %SVR responses for each of the three drugs.

Results: Equivalent infusion doses achieving an approximate 20-25% decrease in SVR from baseline, were identified for epinephrine, dopamine, and sodium nitroprusside. Moreover, equivalent infusion doses were identified for epinephrine and nitroprusside to decrease the SVR by 40% from baseline.

Conclusion: Even though sodium nitroprusside is traditionally used to decrease SVR, low doses of dopamine or epinephrine are viable alternatives to patients with contraindications to nitroprusside infusions or who will require prolonged infusions to avoid toxicity. The multiple comparisons procedure-modeling approach is an excellent methodology for dose-finding exercises and has enabled identification of equivalent pharmacodynamic responses for epinephrine, dopamine, and sodium nitroprusside through mathematic simulations.