Effects of dobutamine, dopamine, phenylephrine and noradrenaline on systemic haemodynamics and intestinal perfusion in isoflurane anaesthetised horses.
Authors: Dancker C, Hopster K, Rohn K, Kästner S B
Journal: Equine veterinary journal
Summary
# Editorial Summary Maintaining adequate intestinal blood flow during equine surgery remains challenging, yet the effects of commonly used inotropic and vasopressor agents on local gut perfusion have never been systematically evaluated in horses under isoflurane anaesthesia. Dancker and colleagues conducted a randomised crossover trial in ten anaesthetised horses, measuring jejunal, colonic and gastric blood flow and tissue oxygenation alongside systemic cardiovascular parameters whilst infusing escalating doses of dobutamine, dopamine, noradrenaline and phenylephrine. High-dose dobutamine emerged as the most favourable option, increasing cardiac output and mean arterial pressure whilst improving jejunal blood flow by 47% and colonic flow by 29% compared to baseline. By contrast, dopamine at high doses paradoxically reduced colonic perfusion by 39% despite raising blood pressure, whilst noradrenaline maintained intestinal flow but offered no improvement over baseline. Phenylephrine proved problematic, decreasing colonic blood flow by 44% and tissue oxygenation by 16%, demonstrating that elevating pressure alone through pure vasoconstriction compromises regional perfusion. For practitioners managing haemodynamically unstable horses during general anaesthesia, these findings suggest dobutamine should be the preferred inotropic agent when intestinal perfusion matters—such as during colic surgery or prolonged procedures—whereas pure vasoconstrictors may inadvertently compromise the very tissues most vulnerable to ischaemic injury.
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Practical Takeaways
- •Dobutamine appears to be the superior inotrope choice during isoflurane anaesthesia in horses, maintaining systemic pressure while improving intestinal perfusion—critical for reducing postoperative colic risk
- •Avoid high-dose dopamine and phenylephrine for blood pressure support in anaesthetised horses, as both compromise intestinal blood flow and oxygen delivery despite raising MAP
- •Noradrenaline maintains intestinal perfusion while supporting blood pressure, making it a reasonable alternative if dobutamine is unavailable or contraindicated
Key Findings
- •High-dose dobutamine significantly increased cardiac output, MAP, and intestinal blood flow to jejunum (+47%) and colon (+29%) compared to baseline
- •Dopamine at highest dose increased cardiac output but decreased colonic blood flow by 39% and MAP compared to baseline
- •Noradrenaline increased MAP and SVR without affecting intestinal perfusion
- •Phenylephrine at highest dose decreased intestinal blood flow (-44% colon) and tissue oxygenation (-16% colon) despite increasing MAP and SVR