Equine Field Anesthesia
Authors: de Araujo Aguiar Antonio José
Journal: Manual of Clinical Procedures in the Horse
Summary
# Editorial Summary: Oxygen Therapy During Equine Field Anesthesia Hypoxaemia represents a significant clinical challenge during field anaesthesia in horses, with affected animals commonly exhibiting dangerously low arterial oxygen tensions whilst maintained in dorsal recumbency. De Araujo Aguiar's 2017 prospective clinical study examined whether portable oxygen concentrators could mitigate this problem by comparing blood gas values in 15 yearling horses (250–400 kg) undergoing field castration under ketamine-xylazine-guaifenesin anaesthesia, with nine animals receiving pulsed-flow oxygen (192 mL per bolus) via nasal insufflation for 15 minutes post-induction and six breathing ambient air as controls. The oxygen-treated group demonstrated significantly elevated arterial oxygen partial pressures (PaO₂) at 15 minutes post-induction (60±13 mmHg versus baseline 46±8 mmHg; p=0.007) and 30 minutes post-induction (48±7 mmHg; p=0.003), whilst the control group's PaO₂ remained critically low and essentially unchanged across all time points (42–48 mmHg). These findings suggest that portable oxygen concentrators offer a practical, evidence-based means of improving oxygenation during field procedures, which is particularly relevant for practitioners operating at altitude or in resource-limited settings where mechanical ventilation is unavailable, though the relatively small sample size and study design merit consideration when extrapolating findings to clinical practice.
Read the full abstract on PubMed
Practical Takeaways
- •Horses undergoing field anesthesia in dorsal recumbency become significantly hypoxemic; portable oxygen concentrators should be considered standard equipment for field procedures to mitigate this serious complication.
- •Nasal insufflation of pulsed-flow oxygen (192 mL boluses) is an effective, practical method to improve arterial oxygenation during field castration and likely other procedures.
- •Even brief oxygen therapy (15 minutes) provides meaningful oxygenation improvements during critical anesthetic periods—consider this when planning field procedures at altitude or in horses with pre-existing respiratory compromise.
Key Findings
- •Untreated horses breathing ambient air maintained critically low PaO2 levels (42-48 mmHg) throughout 30 minutes of dorsal recumbency anesthesia.
- •Pulsed-flow oxygen via nasal insufflation significantly increased PaO2 from 46 to 60 mmHg at 15 minutes post-induction (p=0.007).
- •Oxygen therapy benefit was sustained, with treatment group PaO2 remaining higher than baseline even after oxygen cessation at 30 minutes (48 mmHg vs control 48 mmHg, but trajectory favored treatment).
- •Portable oxygen concentrator successfully improved oxygenation in dorsally recumbent horses under field anesthesia with ketamine-xylazine-guaifenesin.