The improvement in cerebral blood flow (CBF) during
CPR after
epinephrine administration has been attributed to
epinephrine's alpha-
adrenergic properties.
Methoxamine, a pure alpha-1 agonist, has only been shown to be comparable to
epinephrine in restoring circulation after
cardiac arrest in a canine model. This study compares the effectiveness of equipotent doses of
epinephrine and
methoxamine in improving CBF during
CPR after a prolonged
cardiac arrest in a swine model. Twenty-five swine, weighing 15.9 to 28.2 kg, underwent instrumentation for regional CBF using tracer
microspheres. CBF was determined during normal sinus rhythm. After 10 min of
ventricular fibrillation,
CPR was begun with a pneumatic compressor. CBF measurements were again made during
CPR. After 3 min of
CPR, the swine were randomized to receive 0.02 or 0.2 mg/kg
epinephrine, 0.1, 1.0, or 10.0 mg/kg
methoxamine. Five swine were allocated to each group. CBF measurements were determined after
drug administration and compared using a Bonferroni multiple comparison procedure. A p-value less than .05 was considered statistically significant. This study demonstrated that, after a 10-min
cardiac arrest, CBF was extremely low, averaging less than 7 ml/min X 100 g during external
CPR. There were no clinically significant improvements in regional CBF after 0.02 mg/kg of
epinephrine, or the two lowest doses of
methoxamine. The addition of 10 mg/kg of
methoxamine clinically improved blood flow only to the most caudal CNS structures, including the pons, medulla, and cervical spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)