The systemic and regional hemodynamic effects of dopamine, dobutamine, dopexamine and 5% dextrose in sevoflurane anesthetized dogs.

This study examined the influence of dopamine (DA), dobutamine (DB), dopexamine (DX) and 5% dextrose (5Dx) on microcirculation in the kidney and muscle, and on their relations to other cardiopulmonary changes in dogs. Six English Pointers (two male, four female, 23 ± 6 kg, 2 ± 1 years) were mask-induced and maintained with sevoflurane anesthesia at 2.6% end tidal concentration under controlled ventilation in left lateral recumbency. Cardiopulmonary variables measured include direct blood pressures, cardiac output (CO) by thermodilution technique, heart rate (HR), blood gases, and end tidal gases. During one hour of anesthetic stabilization time, a laser Doppler flowmeter was incorporated to monitor dynamic changes in intrarenocortical blood flow (IRBF) and intramuscular blood flow (IMBF), utilizing fine stainless optical fibers embedded within the cortex of the right kidney guided by ultrasonography and the right biceps femoris, respectively. First measurement of variables (baseline: BL) was taken prior to drug infusion followed by subsequent measurements at 15-minute intervals for a further 2 hours. On separate occasions, DA, DB and DX diluted in 5Dx were infused at 2, 4, 8, 16 µg kg−1 minute−1, and the equivalent volume of 5Dx, for the control group, at 12.5, 25, 50, 100 mL h−1 was infused, each dose lasting for 15 minutes. The order of each drug administration was random, with a minimum of 1 week's rest between drugs. Data collected during and following infusions were compared with BL, using anova for repeated measures followed by Dunnet's post-test where applicable (p < 0.05). Data from 5Dx were compared with those from DA, DB and DX at equivalent time points by anova for repeated measures followed by Bonferroni's post-test where applicable (p < 0.05). DA, DB and DX all increased IMBF in dose dependent manner, up 250% higher than BL, with all being statistically significant at the highest infusion rate. Among groups significance occurred only in DA compared to 5Dx value at 16 µg kg−1 minute−1. IRBF increase was less distinctive than IMBF, being 150% higher than BL in DA and DB, and 120% in DX, even at the highest infusion rate. 5Dx did not increase IRBF, all values being lower than BL. HR changed little following DA and 5Dx but increased, with increased infusion rates, up to 165 ± 27 from 116 ± 10 (DB) and up to 138 ± 9 from 105 ± 16 beats minute−1 (DX). DA significantly increased mean arterial blood pressure (MAP) up to 116 ± 26 from 67 ± 14 mm Hg (BL). In contrast, DX significantly decreased MAP, down to 42 ± 8 from 62 ± 9 mm Hg (BL). Slight changes of MAP were seen at all time points in DB and 5Dx. CO increased significantly, in a dose related manner in all treatment groups, reaching the maximum of 9.2 ± 3.4 from 3 ± 1 L minute−1 (BL) in DB. All drugs demonstrated potential benefit in improving regional and systemic hemodynamics. Whilst DA was more effective in raising MAP, IRBF and IMBF; DX was effective in improving CO, IRBF and IMBF despite a marked decrease in MAP. This study presents that microcirculatory changes tend to follow those of CO but are less dependent on vascular driving force.