Plasma aldosterone, vasopressin and atrial natriuretic peptide in hypovolaemia: a preliminary comparative study of neonatal and mature horses.
Authors: Hollis A R, Boston R C, Corley K T T
Journal: Equine veterinary journal
Summary
# Editorial Summary Neonatal foals demonstrate markedly different physiological responses to blood loss compared with adult horses, including atypical cardiovascular compensation and altered fluid requirements—a distinction that prompted investigation into the underlying hormonal mechanisms governing fluid homeostasis across these age groups. Researchers measured plasma concentrations of three key regulatory hormones (aldosterone, vasopressin, and atrial natriuretic peptide) in five mature horses and five foals presenting with clinical hypovolaemia, collecting samples both at admission and following fluid resuscitation to normalisation of fluid balance. Mature horses showed the expected pattern of elevated aldosterone, vasopressin, and ANP during hypovolaemia that subsequently declined with rehydration; foals, however, demonstrated persistently elevated aldosterone regardless of fluid status and displayed significantly higher aldosterone concentrations than adults both before and after treatment. These divergent hormonal signatures suggest that foals may be operating under fundamentally different neuroendocrine control during hypovolaemic stress, with potential implications for how clinicians should approach fluid resuscitation protocols in this population. Whilst the small sample size necessitates cautious interpretation, the findings highlight that current fluid management strategies derived from adult equine medicine may not account for age-related differences in compensatory mechanisms—warranting larger prospective studies to optimise therapeutic approaches in neonatal cases where rapid deterioration remains a significant clinical challenge.
Read the full abstract on PubMed
Practical Takeaways
- •Neonatal foals require different fluid resuscitation protocols than mature horses due to distinct hormonal compensation mechanisms during hypovolaemic shock
- •The elevated baseline aldosterone in foals suggests their kidneys may be more responsive to volume depletion, which should inform fluid and electrolyte management strategies
- •Monitor for species-age differences in cardiovascular compensation during shock; foals may not show expected tachycardia and need closer clinical assessment beyond heart rate alone
Key Findings
- •ANP, AVP and aldosterone were significantly higher before fluid resuscitation than after in mature horses
- •Aldosterone was significantly higher in foals both before and after fluid resuscitation compared to mature horses
- •Neonatal foals and mature horses demonstrate different hormonal responses to hypovolaemia and fluid administration
- •ANP was significantly lower in mature horses after fluid resuscitation compared to foals