Study objectives: To assess the effects of two contrasting vasoactive
agents (dobutamine [DOB] and norepinephrine [NE]) on (1) global and re
gional cardiorespiratory variables, (2) acid base status, and (3) blad
der epithelial oxygen tension (BEOT), a putative marker of organ perfu
sion. Design: Measurement of aortic blood flow (ABF) and renal blood f
low (RBF), mean arterial blood pressure, arterial blood gases, and BEO
T were made during infusion of placebo and varying doses of DOB and NE
. Setting: Medical school laboratory. Subjects: Eighteen anesthetized,
spontaneously breathing, male Sprague-Dawley rats divided into three
groups, Interventions: Two groups were allocated to receive escalating
doses of DOE (to 40 mu g/kg/min) or NE (to achieve a 50% change in an
y hemodynamic variable), The drug therapy was then discontinued for 15
min and restarted at the previous maximum dose, A third group receive
d 0.9% saline solution at the same infusion rate (16 mL/kg/h). Measure
ments and results: There was a dose-related increase in mean blood pre
ssure with NE and fall with DOB. Compared with control values, NE had
no effect on ABF but decreased RBF significantly whereas DOB significa
ntly increased ABF: but had no effect on RBF. Base excess and BEOT dec
reased significantly and in parallel with both agents, more so with NE
. Conclusions: Despite their different macrocirculatory effects, DOB a
nd NE both produced a significant but reversible fall in BEOT and a me
tabolic acidosis, BEOT shows potential as a monitor of die effectivene
ss of organ perfusion.