Cardiovascular effects of enoximone in isoflurane anaesthetized ponies.
OBJECTIVE
Enoximone is a phosphodiesterase III inhibitor frequently used to improve cardiac output (CO) in man. As the use of enoximone has not been reported in horses, the effects of this inodilator were examined in isoflurane anaesthetized ponies.


METHODS
Prospective, randomised, experimental study.


METHODS
Six healthy ponies, weighing 286 (212-367) +/- 52 kg, aged 5.0 +/- 1.6 years (4-6.5).


METHODS
After sedation with romifidine [80 microg kg(-1) intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg(-1) IV) and ketamine (2.2 mg kg(-1) IV) and maintained with isoflurane in oxygen (Et Iso 1.7%). The ponies were ventilated to maintain eucapnia (PaCO(2) 4.66-6.00 kPa). Each pony was anaesthetized twice with an interval of 3 weeks; receiving enoximone 0.5 mg kg(-1) IV (E) or saline (S) 90 minutes post-induction. Heart rate (HR), arterial (AP) and right atrial pressure (RAP) were measured before treatment, every 5 minutes between T0 (treatment) and T30 and then every 10 minutes until T120. Cardiac output measurements (lithium dilution technique) and blood gas analysis (arterial and central venous samples) were performed before T0 and at T5, T10, T20, T40, T60, T80, T100 and T120. Stroke volume (SV), systemic vascular resistance (SVR), venous admixture (Qs/Qt) and oxygen delivery (DO(2)) were calculated.


RESULTS
Enoximone induced significant increases in HR, CO, SV, Qs/Qt and DO(2) and a significant decrease in RAP. No significant differences were detected for AP, SVR and blood gases. No cardiac arrhythmias or other side effects were observed.


CONCLUSIONS
The present results suggest that in isoflurane anaesthetized ponies, enoximone has beneficial effects on CO and SV without producing significant changes in blood pressure. Despite an increase in Qs/Qt, DO(2) to the tissues was improved.
Schauvliege
Stijn
S
Department Of Surgery and Anaesthesia of Domestic Animals, University of Ghent, Merelbeke, Belgium. stijn.schauvliege@ugent.be
Van den Eede
Annelies
A
Duchateau
Luc
L
Gasthuys
Frank
F
D000758:Anesthesia / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017335:Enoximone / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006736:Horses / Q000502:physiology*; D007275:Injections, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D010100:Oxygen / Q000097:blood; D011446:Prospective Studies; D016896:Treatment Outcome
D018685:Anesthetics, Inhalation; D002316:Cardiotonic Agents; D002245:Carbon Dioxide; D017335:Enoximone; D007530:Isoflurane; D010100:Oxygen