Neither dopamine nor dobutamine corrects mesenteric blood flow depression caused by positive end-expiratory pressure in a rat model of acute lung injury

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Abstract

Objective

To determine if either dopamine or dobutamine would counteract the deleterious effect that positive end-expiratory pressure (PEEP) has on cardiac output and mesenteric blood flow in a rat model of acute lung injury.

Design

Prospective, randomized, controlled trial in a clinically relevant model of acute lung injury.

Setting

Microcirculation research laboratory.

Subjects

Male Sprague-Dawley rats.

Interventions

The animals were anesthetized with pentobarbital (30 mg/kg) by intraperitoneal injection. They underwent tracheostomy, jugular and femoral vein cannulation, femoral artery cannulation, carotid artery thermistor placement, and bowel preparation for in vivo video microscopy. Acute lung injury was created by administering 0.1 N hydrochloric acid (1 mL/kg) via the tracheostomy. Dopamine or dobutamine (2.5 or 12.5 [micro sign]g/kg/min), followed by two intravenous fluid boluses, was administered to rats ventilated with 5, 10, 15, and 20 cm H2 O of PEEP.

Measurements and Main Results

Mean arterial pressure, thermodilution cardiac output, mesenteric arteriolar diameter, and red blood cell velocity were measured and mesenteric blood flow was calculated. Cardiac output was depressed in rats exposed to 20 cm H2 O of PEEP by 32 +/- 2%. The corresponding values for cardiac output depression at 20 cm H2 O of PEEP in rats receiving 2.5 and 12.5 [micro sign]g/kg/min of dopamine and 2.5 and 12.5 [micro sign]g/kg/min of dobutamine were 31 +/- 1%, 21 +/- 1%, 29 +/- 0%, and 24 +/- 2%, respectively. Mesenteric blood flow was depressed in rats ventilated with 20 cm H2 O of PEEP by 74 +/- 3%, while the corresponding values in rats exposed to 20 cm H2 O of PEEP and receiving 2.5 or 12.5 [micro sign]g/kg/min of dopamine or 2.5 or 12.5 [micro sign]g/kg/min of dobutamine were 86 +/- 3%, 77 +/- 3%, 73 +/- 3%, and 66 +/- 3%, respectively. Fluid boluses did not correct the deficits in cardiac output or mesenteric blood flow caused by the combination of acute lung injury and PEEP.

Conclusions

The higher doses of dopamine and dobutamine partially, but insignificantly, corrected the cardiac output depression caused by PEEP in a model of acute lung injury. Neither dose of dopamine nor dobutamine was able to improve PEEP-induced mesenteric blood flow depression. (Crit Care Med 1998; 26: 1875-1880)

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