Authors: La Rosa Lavinia, Twele Lara, Duchateau Luc, Gasthuys Frank, Kästner Sabine Br, Schauvliege Stijn
Journal: Journal of equine veterinary science
Summary
Intravenous magnesium sulphate has long been proposed as an analgesic agent in equine medicine, yet its efficacy in modulating pain perception remains poorly characterised. La Rosa and colleagues administered a 50 mg kg⁻¹ bolus of MgSO₄ or saline control to five healthy horses and measured electrical, thermal, and mechanical nociceptive thresholds at the pelvic limbs before and at multiple timepoints following infusion, whilst simultaneously tracking physiological parameters and plasma ion concentrations. Despite detecting significant cardiovascular effects—increased heart rate, reduced systolic blood pressure, and decreased respiratory rate following magnesium treatment—the study found no meaningful changes in any nociceptive threshold modality; confidence intervals for thermal, mechanical, and electrical thresholds spanned [-1; +2]°C, [0; +3] N, and [-1; +1] mA respectively, indicating no analgesic benefit. Whilst these findings challenge the use of IV MgSO₄ specifically for pain modulation in standing, non-sedated horses, clinicians should note the reliable cardiovascular alterations observed, which warrant consideration when using this agent in anaesthetic or perioperative contexts. Further investigation in different pain models and sedation states may be warranted before dismissing magnesium's therapeutic potential entirely.
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Practical Takeaways
- •Intravenous magnesium sulfate at 50 mg/kg does not appear to provide analgesia in standing horses based on nociceptive threshold testing, despite producing measurable physiological changes
- •While MgSO4 administration alters heart rate and blood pressure, these cardiovascular effects occur without corresponding improvements in pain perception thresholds that might be clinically relevant for pain management
- •Current evidence does not support the use of IV MgSO4 as an analgesic agent in horses, though further research in different contexts (sedated, painful conditions) may be warranted
Key Findings
- •Intravenous MgSO4 50 mg/kg produced no changes in electrical, thermal, or mechanical nociceptive thresholds in standing non-sedated horses (95% CI: [-1; +1] mA, [-1; +2]°C, [0; +3] N respectively)
- •Heart rate significantly increased (P < 0.0001) and systolic arterial pressure and respiratory rate significantly decreased (P < 0.0001 and P = 0.0002) following MgSO4 treatment compared to saline control
- •Mild changes in cardiovascular parameters and plasma ion concentrations occurred with IV MgSO4 administration but did not translate to analgesic effects on nociceptive thresholds