CARDIOVASCULAR-RESPONSES TO GRADED DOSES OF 3 CATECHOLAMINES DURING LACTIC AND HYDROCHLORIC ACIDOSIS IN DOGS

We have studied the cardiovascular effects of incremental doses of three catecholamines in dogs subjected to lactic (LAG) and hydrochloric (HCl) acidosis. Fifty-four dogs were allocated randomly to one of three groups: control, LAC and HCl acidosis (n=18 each group). In the acidotic models, 2 mol litre(-1) of lactic acid (4 mi kg(-1) h(-1)) or 2 mol litre(-1) of HCl (1 mi kg(-1) h(-1)) was infused i.v. until arterial pH was reduced to 7.00+/-0.1. Within each group, six dogs received one of three different drugs in logarithmically incremental doses: adrenaline 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 mu g kg(-1) min(-1) noradrenaline 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 mu g kg(-1) min(-1) and dobutamine 5, 10, 20, 40, 80, 160 mu g kg(-1) min(-1). Cardiovascular variables were monitored, with periodic measurements of plasma electrolyte and lactate concentrations. The pH reduction induced by HCl or lactic acid was associated with a statistically significant increase in mean pulmonary arterial pressure (MPAP), prominent especially in the LAC group where MPAP increased from mean 18 (so 5) to 27 (6) mm Hg. In the acidotic models, the reduction in myocardial responsiveness to adrenaline or noradrenaline was more prominent than that for the control for corresponding doses of drugs. In the LAC group mean cardiac index decreased significantly from 5.2 (1.8) to 2.2 (0.7) litre min(-1) m(-2) after infusion of adrenaline 3.2 mu g kg(-1) min(-1) and decreased from 5.1 (1.1 to 2.4 (0.9) litre min(-1) m(-2) after infusion of noradrenaline 3.2 mu g kg(-1) min(-1). In contrast, dobutamine showed dose-dependent increases in cardiac index and heart rate in control, as well as acidotic groups. The acute HCl acidosis induced greater hyperkalaemia than the lactic acidosis.