Epinephrine is more effective than other sympathomimetics in correcting cerebral hypoperfusion associated with mesenteric ischemic reperfusion insult

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Objective

To assess the efficacy of sympathomimetics in maintaining cerebral blood flow when cardiac function is impaired.

Background

Sympathomimetics are frequently used to treat hypotensive newborns with one of the goals being the preservation of cerebral blood flow. No animal model has substantiated the efficacy of this practice. Although inotropes have been extensively studied in healthy animals, little is available concerning their efficacy in "sick" hemodynamically impaired newborn animals.

Design/methods

A laparotomy was performed in anesthetized piglets (10±1 days old, n=40) to clamp a major branch of the superior mesenteric artery for 30 min. One hour after, a persistent state of impaired cardiac function was produced. Cardiac output remained 24± 2% below initial baseline. There was a parallel decrease in carotid blood flow (21± 5%) (CBF) while the decrement in systemic mean blood pressure (BP) was small (73± 2 to 67± 2 mmHg; P<0.01). Those parameters remained the same for the next two hours when treatment consisted only of intravenous normal saline at a rate of 35 ml/kg/h. One hour after the start of mesenteric reperfusion, animals were randomized to additionally receive: Dobutamine (DOB), Dopamine (DP), Epinephrine (EPI) or no inotropes (CONT). The sympathomimetics (SYMP) were given at 20 min intervals, using a randomized latin squares design, at a rate of 5, 10, 20, 40 (DOB and DP) or 0.5, 1, 2 and 4 μg/kg/min (EPI). The animals were instrumented to measure: aortic, pulmonary artery and superior sagittal sinus blood gases and lactate, cerebral oxygen extraction (CBF ext); mean systemic and pulmonary artery pressures (PAP); cardiac output (thermodilution), carotid blood flow (ultrasonic flow transducers).

Results

See Table. Mean ± s.e.m of the % change from levels immediately prior to treatment.

Conclusions

Depressed cardiac output is associated with a significant decrease in cerebral blood flow even though BP is minimally reduced. EPI may be more efficient than the other inotropes in supporting neonatal CBF when CO is impaired.

Table 1