Cardiovascular effects of intravenous morphine in anesthetized horse.
Authors: Hoeberg Emma, Haga Henning Andreas, Lervik Andreas
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Cardiovascular Effects of Intravenous Morphine in Anesthetized Horse This prospective, randomised, blinded trial examined whether morphine administration alters haemodynamic stability in 33 healthy horses maintained under isoflurane and dexmedetomidine infusion—a common clinical anaesthetic protocol. Following baseline measurements of mean arterial pressure (MAP), heart rate (HR) and oxygen extraction (OE), horses received either 0.1 mg/kg morphine or saline placebo intravenously, with cardiovascular variables reassessed over 5 minutes via arterial and venous blood gas analysis. Morphine produced a MAP decrease of 9–20.5% (95% CI) and modest HR increase of 0.6–3.1 bpm, with negligible changes in oxygen extraction (−0.1 to 0.6 mL/dL)—responses statistically indistinguishable from the placebo group's 10.1–17.4% MAP reduction and 0.2–2.0 bpm HR change. One horse in the morphine cohort experienced a marked 50% MAP drop without compensatory increases in HR or OE, highlighting individual variability worthy of clinical attention. These findings suggest that at this dose, morphine adds minimal cardiovascular burden when combined with isoflurane and dexmedetomidine, supporting its continued use in routine equine anaesthesia for analgesia without expecting significant haemodynamic complications in healthy patients—though perioperative monitoring remains essential to identify outlier responses.
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Practical Takeaways
- •Morphine at 0.1 mg/kg can be safely used in anesthetized horses maintained on isoflurane and dexmedetomidine with minimal cardiovascular depression
- •While morphine does not significantly worsen blood pressure or oxygenation compared to placebo in this anesthetic protocol, individual monitoring remains essential as one horse showed marked MAP reduction
- •This dosing supports morphine's use for intraoperative analgesia in healthy horses without expecting clinically significant hemodynamic complications beyond baseline anesthetic effects
Key Findings
- •Morphine 0.1 mg/kg IV caused minimal change in mean arterial pressure (−20.5 to −9.0% decrease) compared to placebo (−17.4 to −10.1%)
- •Heart rate and oxygen extraction remained essentially unchanged with morphine administration, with overlapping confidence intervals between morphine and placebo groups
- •One horse in the morphine group experienced a 50% MAP decrease without corresponding changes in oxygen extraction or heart rate, suggesting individual variation in response