RESUMO
OBJECTIVE: To evaluate the effect of ephedrine on intramuscular blood flow and hemodynamic parameters during equine anesthesia. STUDY DESIGN: Prospective experimental study. ANIMALS: Six healthy adult Welsh Mountain ponies (five males, one female, mean weight: 267 kg, range: 213-347 kg). METHODS: Halothane-anesthetized ponies received an IV bolus of ephedrine (0.1 mg kg-1), followed 30 minutes later by a second IV ephedrine injection (0.2 mg kg-1). Changes in intramuscular blood flows (IMBF) in upper and lower triceps brachii were measured by laser Doppler flowmetry. Cardiopulmonary measurements were made at intervals for 30 minutes following each injection. Results were compared with values from a control group, similarly anesthetized but given saline in an earlier study. RESULTS: Ephedrine at either dose increased heart rate, arterial blood pressure (AP), cardiac index (CI) and intramuscular blood flow (IMBF), the effects on these parameters being significant and long-lasting following the higher dose. Systemic vascular resistance remained unchanged, and was significantly lower than in the control saline group. PaO2 decreased significantly immediately following the first injection of ephedrine, then remained unchanged for the remainder of the experiment. PaCO2 increased slowly throughout the anesthetic period. One pony developed supraventricular premature complexes following the second injection. No other side effects were seen. CONCLUSION: Ephedrine at dose rates of 0.2 mg kg-1 IV consistently increased in CI, AP, and IMBF in both forelimbs. CLINICAL RELEVANCE: Ephedrine may be of use to improve AP, CI and IMBF during halothane anesthesia, although the occurrence of an arrhythmia in one pony is of concern.
