Arterial blood gas parameters of normal foals born at 1500 metres elevation.
Authors: Hackett E S, Traub-Dargatz J L, Knowles J E, Tarr S F, Dargatz D A
Journal: Equine veterinary journal
Summary
# Arterial Blood Gas Parameters in Altitude-Born Foals: Establishing New Baseline Values When evaluating respiratory function in neonatal foals via arterial blood gas analysis, clinicians typically reference values derived from sea-level populations—a potential source of diagnostic error for foals born at elevation. Hackett and colleagues addressed this gap by collecting arterial blood samples from 16 healthy foals born at 1500 metres in Colorado within the first hour post partum and at 6-hourly intervals through 48 hours, directly comparing their findings against published sea-level data. Foals at altitude displayed significantly lower partial pressures of oxygen (mean 53.0 mmHg at 1 hour, rising to 67.5 mmHg by 48 hours) and carbon dioxide (44.1 mmHg falling to 38.3 mmHg) relative to sea-level neonates, reflecting both the reduced inspired oxygen at elevation and a compensatory hyperventilation response sustained across the first two days of life. These altitude-specific reference intervals are essential for practitioners working in mountainous regions, as applying sea-level standards could lead to misinterpretation of clinically normal blood gases as pathological, potentially triggering unnecessary intervention in otherwise healthy neonates. Equine veterinarians providing critical care at elevation should establish locally derived baseline values or adjust their interpretation thresholds accordingly to avoid diagnostic inaccuracy.
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Practical Takeaways
- •If providing critical care to neonatal foals at high altitude (1500 m+), use altitude-specific ABG reference ranges rather than sea-level values to avoid misdiagnosis of respiratory pathology
- •Expect lower PaO2 and PaCO2 in normal foals born at elevation; these values stabilize within 48 hours post-partum
- •Establish facility-specific normal values for your elevation to improve diagnostic accuracy in neonatal foal emergencies
Key Findings
- •Mean PaO2 in foals at 1500 m elevation was 53.0 mmHg at 1 h post-partum, rising to 67.5 mmHg by 48 h
- •Mean PaCO2 decreased from 44.1 mmHg at 1 h to 38.3 mmHg at 48 h post-partum
- •Both PaO2 and PaCO2 were significantly lower in altitude-born foals compared to sea-level foals at multiple time points in first 48 h
- •Altitude-specific reference values are necessary for accurate interpretation of arterial blood gas analysis in neonatal foals