Use of ephedrine and dopamine in dogs for the management of hypotension in routine clinical cases under isoflurane anesthesia.

OBJECTIVE

To determine the cardiovascular responses of ephedrine and dopamine for the management of presurgical hypotension in anesthetized dogs.

STUDY DESIGN

Prospective, randomized, clinical trial.

ANIMALS

Twelve healthy client-owned dogs admitted for orthopedic surgery; six per group

METHODS

Prior to surgery, 58 anesthetized dogs were monitored for hypotension [mean arterial pressure (MAP) <60 mmHg] that was not associated with bradycardia or excessive anesthetic depth. Ephedrine (0.2 mg kg(-1), IV) or dopamine (5 microg kg(-1) minute(-1), IV) was randomly assigned for treatment in 12 hypotensive dogs. Ten minutes after the first treatment (Tx(1)-10), ephedrine was repeated or the dopamine infusion rate was doubled. Cardiovascular assessments taken at baseline, Tx(1)-10, and 10 minutes following treatment adjustment (Tx(2)-10) were compared for differences within and between treatments (p < 0.05).

RESULTS

Ephedrine increased cardiac index (CI), stroke volume index (SVI), oxygen delivery index (DO(2)I), and decreased total peripheral resistance (TPR) by Tx(1)-10, while MAP increased transiently (<5 minutes). The second ephedrine bolus produced no further improvement. Dopamine failed to produce significant changes at 5 microg kg(-1) minute(-1), while 10 microg kg(-1) minute(-1) increased MAP, CI, SVI significantly from baseline, and DO(2)I compared with Tx(1)-10. The improvement in CI, SVI, and DO(2)I was not significantly different between treatments at Tx(2)-10.

CONCLUSIONS AND CLINICAL RELEVANCE

In anesthetized hypotensive dogs, ephedrine and dopamine improved cardiac output and oxygen delivery. However, the pressure-elevating effect of ephedrine is transient, while an infusion of dopamine at 10 microg kg(-1) minute(-1) improved MAP significantly by additionally maintaining TPR.