Temporal and concentration effects of isoflurane anaesthesia on intestinal tissue oxygenation and perfusion in horses.
Authors: Hopster K, Hopster-Iversen C, Geburek F, Rohn K, Kästner S B R
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Isoflurane's dose-dependent effects on systemic and intestinal perfusion represent a critical consideration for equine surgical practice, particularly during prolonged procedures. Kästner and colleagues maintained nine healthy Warmblood horses under isoflurane anaesthesia for seven hours, systematically varying expiratory isoflurane concentration (ETIso) between 1.2–2.4% whilst measuring cardiac index, mean arterial pressure, and intestinal microperfusion and oxygenation via laser Doppler flowmetry and spectrophotometry at jejunal and colonic sites. Intestinal perfusion and oxygen delivery remained remarkably stable until ETIso reached 2.0%, after which both declined sharply in association with critical reductions in cardiac index (to 48 mL/kg/min) and mean arterial pressure (to 62 mmHg); notably, duration of anaesthesia itself did not compromise tissue perfusion, and all parameters recovered when isoflurane concentration was reduced. These findings suggest that whilst isoflurane concentration significantly influences splanchnic perfusion, a physiological threshold exists below which the intestinal microvasculature maintains adequate blood flow and oxygenation—implying that surgical time alone need not be restricted in healthy animals, provided isoflurane doses are kept within conservative ranges and systemic pressures maintained above these critical thresholds.
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Practical Takeaways
- •Monitor isoflurane concentration carefully during equine surgery as intestinal perfusion is only preserved up to a critical threshold; maintaining MAP above 62 mmHg and CI above 48 mL/kg/min helps protect gut tissue
- •Duration of anaesthesia alone does not compromise intestinal oxygenation in healthy horses, allowing for longer procedures without this specific concern
- •Reducing isoflurane concentration promptly can reverse perfusion and oxygenation deficits to the intestines, supporting rapid recovery protocols
Key Findings
- •Cardiac index and mean arterial blood pressure decreased continuously with increasing isoflurane concentration, reaching 40±5 mL/kg/min and 52±8 mmHg at 2.4% ETIso
- •Intestinal microperfusion and oxygenation remained stable until isoflurane concentration reached 2.0% (MAP 62±6 mmHg, CI 48±5 mL/kg/min), then decreased rapidly
- •Isoflurane concentration, but not duration of anaesthesia, influenced central and intestinal oxygenation and perfusion
- •Recovery of cardiac index, mean arterial pressure, microperfusion and oxygenation occurred when isoflurane concentration was reduced to baseline levels