Cardiac output measurement by partial carbon dioxide rebreathing, 2-dimensional echocardiography, and lithium-dilution method in anesthetized neonatal foals.
Authors: Giguère Steeve, Bucki Eric, Adin Darcy B, Valverde Alexander, Estrada Amara H, Young Linda
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary When a neonatal foal is critically ill, knowing its cardiac output is crucial for guiding treatment decisions, yet most non-invasive measurement techniques have not been validated in this age group. Researchers anaesthetised ten neonatal foals and deliberately altered their cardiac output through varying anaesthetic depth and dobutamine infusion, then compared three non-invasive measurement methods—partial CO₂ rebreathing and two echocardiographic approaches—against the reference standard of lithium dilution. Cardiac output ranged from 3.09 to 11.1 L/min across the study population, and volumetric echocardiography using the Bullet formula proved most reliable, with a bias of only −4.2% and clinically acceptable agreement limits; importantly, this method remained consistent across different cardiac output levels, whereas Doppler ultrasound became progressively less accurate as output increased. For equine practitioners managing critically ill or anaesthetised foals, this finding suggests that two-dimensional echocardiography with the Bullet calculation method offers a practical, non-invasive way to monitor cardiac function and assess treatment response—though the authors rightly note that validation in conscious, sick foals is the essential next step before confident clinical implementation.
Read the full abstract on PubMed
Practical Takeaways
- •For practitioners managing anesthetized neonatal foals, the Bullet echocardiography method offers the most accurate noninvasive cardiac output measurement and should be considered for monitoring hemodynamic stability during anesthesia
- •Doppler echocardiography becomes increasingly unreliable as cardiac output increases in foals, so alternative methods should be used when higher cardiac outputs are anticipated or detected
- •Partial CO2 rebreathing technique becomes less reliable at higher cardiac outputs, limiting its utility in foals with elevated cardiac demands or under dobutamine stimulation
Key Findings
- •Volumetric echocardiography using the Bullet method showed significantly lower relative bias (-4.2 ± 20.9%) compared to other noninvasive methods for CO measurement in anesthetized neonatal foals
- •Doppler echocardiography relative bias significantly increased with increasing cardiac output (P < 0.05), whereas partial CO2 rebreathing significantly decreased (P = 0.03)
- •Lithium-dilution cardiac output measurements ranged from 3.09–11.1 L/min with cardiac indices of 79.0–209 mL/kg/min in the study population
- •The Bullet method was the most reliable noninvasive cardiac output measurement technique among volumetric echocardiography formulas evaluated in this anesthetized neonatal foal model