Effects of dobutamine on cardiac index and arterial blood pressure in isoflurane‐anaesthetized horses under clinical conditions

Abstract

Volatile agent-induced hypotension may contribute to anaesthetic-related morbidity and mortality in horses. Dobutamine is commonly used to support arterial blood pressure (ABP) but little is known about its cardiovascular effects under clinical conditions. The aim of this clinical study was to elucidate the relationship between cardiovascular function and dobutamine infusion in isoflurane-anaesthetized horses. Forty-four horses anaesthetized for a variety of surgical procedures were studied. Premedication with acepromazine, methadone and detomidine was followed by induction of anaesthesia with ketamine and midazolam. Anaesthesia was maintained with isoflurane vaporized in oxygen. Routine anaesthetic monitoring was applied and cardiac output was measured by lithium dilution. Dobutamine was infused to maintain mean ABP above 70 mmHg. The relationship between dobutamine infusion rate, heart rate (HR), ABP and cardiac index was investigated immediately prior to (T(0)) and 15 min (T(1)) after dobutamine infusion started, followed at 30 min intervals (T(2), etc.). Arterial blood pressure increased significantly after dobutamine infusion started, HR and cardiac index increased significantly only with dobutamine infusion in combination with surgical stimulus. Although isoflurane decreases blood pressure mainly by vasodilation, dobutamine is an effective treatment for hypotension under clinical conditions in isoflurane-anaesthetized horses. The effect of dobutamine is not directly proportional to dose and surgical stimulus probably contributes to the cardiovascular improvement.

The Effect of Dobutamine and Bolus Crystalloid Fluids on the Cardiovascular Function of Isoflurane Anaesthetised Horses

“…This contrasts with previous studies that administered dobutamine at a constant rate (Raisis et al 2000a, Young et al 1998, Dyson and Pascoe 1990 in normotensive horses (Raisis et al 2000a, Hinchcliff et al 1991. The dose of dobutamine needed to achieve the required increase in MAP in this study did not differ significantly between treatments and was similar to previous studies [Mizuno et al 1994, de Vries et al 2009, Duronghongtorn et al 2006, Hinchcliff et al 1991, Donaldson 1988, Lee et al 1998.…”

Detomidine and the combination of detomidine and MK-467, a peripheral alpha-2 adrenoceptor antagonist, as premedication in horses anaesthetized with isoflurane

“…() did not find significant increases in t until 40 minutes of 4 μg kg −1 minute −1 dobutamine infusion, and de Vries et al. () reported increased CI only when the dobutamine infusion was combined with a surgical stimulus. Previous reports on the effects of dobutamine infusions on SVR in horses have described either decreases in SVR (Lee et al.…”

Cardiovascular Effects of Dobutamine and Phenylephrine Infusion in Sevoflurane-anesthetized Thoroughbred Horses

“…Dosages of dobutamine in this study were determined on the basis of those commonly recommended in the previous literatures [6, 7, 17, 22], and these dosages have been routinely used in our clinical practice. On the other hand, dosages of phenylephrine in this study were determined on the basis of the results in the preliminary experimental trials in our clinic.…”

“…Dobutamine is a synthetic catecholamine, which directly increases myocardial contractility by stimulating β 1 -adrenergic receptors and reverses anesthetic-induced hypotension in small animals [19, 24] and horses [5, 6, 7, 17, 22]. On the other hand, dobutamine is known to increase myocardial oxygen consumption and sometimes induce tachycardia and ventricular arrhythmias [15].…”