The effect of norepinephrine and dobutamine on bladder epithelial oxygen tension.

STUDY OBJECTIVES

To assess the effects of two contrasting vasoactive agents (dobutamine [DOB] and norepinephrine [NE]) on (1) global and regional cardiorespiratory variables, (2) acid base status, and (3) bladder epithelial oxygen tension (BEOT), a putative marker of organ perfusion.

DESIGN

Measurement of aortic blood flow (ABF) and renal blood flow (RBF), mean arterial blood pressure, arterial blood gases, and BEOT 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 DOB (to 40 micrograms/kg/min) or NE (to achieve a 50% change in any hemodynamic variable). The drug therapy was then discontinued for 15 min and restarted at the previous maximum dose. A third group received 0.9% saline solution at the same infusion rate (16 mL/kg/h).

MEASUREMENTS AND RESULTS

There was a dose-related increase in mean blood pressure with NE and fall with DOB. Compared with control values, NE had no effect on ABF but decreased RBF significantly whereas DOB significantly increased ABF but had no effect on RBF. Base excess and BEOT decreased significantly and in parallel with both agents, more so with NE.

CONCLUSIONS

Despite their different macrocirculatory effects, DOB and NE both produced a significant but reversible fall in BEOT and a metabolic acidosis. BEOT shows potential as a monitor of the effectiveness of organ perfusion.