FOAL FLUID THERAPY
Dr Karin Kruger BVSc, MSc, DACVIM
Equine Specialist Physician, Witbos Veterinary Clinic
+27713914407; [email protected]
Introduction
As with all therapeutic interventions, one cannot separate fluid therapy in the foal
from its physiology and the pathophysiology of each individual disease process. For
this reason, there can never be a ‘one size fits all’ approach to fluid therapy, and
each patient’s fluid plan needs to be individually designed, monitored and redesigned based on its individual and temporal needs at each stage of disease and
treatment.
When designing a fluid therapy plan, one must have clearly defined and measurable
goals such as:
• Replacing lost fluids and electrolytes and correcting acid-base imbalances.
e.g. foal diarrhea, hyperkalemia in uroperitoneum, acute renal failure,
metabolic
acidosis
due
to
hyperlactataemia
or
hyponatraemia/hyperchloraemia
• Providing maintenance fluids to patients who cannot drink on their own
and/or where the intestine does not work
e.g. 3-5 ml/kg/day
• Replacing ongoing fluid and electrolyte losses.
e.g. reflux, diarrhea, hyperhidrosis and polyuria
• Maintaining blood pressure and oncotic pressure.
e.g. endotoxaemia and sepsis increases vascular permeability,
reduces vascular response and causes myocardial suppression with
resultant hypotension, hypoperfusion and edema. Oncotic pressure
(60-80% albumin) should be above 14mmHg (normal 15-23 in
neonates).
Physiological and pathophysiological considerations
Neonatal foals do not always mount protective physiological responses to disease
states. It is not uncommon to find a normal respiratory rate in a foal with hypoxaemia,
or a normal heart rate in a severely hypovolaemic foal. Hypovolaemia can therefore
be difficult to detect in a foal, as classical signs such as tachycardia, decreased
pulse pressure, reduced jugular fill, tachypnoea and cold extremities are not always
present. Any foal that has not nursed appropriately for 6 hours should be considered
hypovolaemic. In the absence of a good nursing history, palpating the mare’s udder
may provide valuable clues to whether the foal has been suckling.
Fluid therapy in neonatal foals is especially challenging because of differences in
renal, cardiovascular, and endocrine physiology that can dramatically impact sodium
and water balance. They have increased body water compared to adults, but are
prone to edema and fluid overload and their kidneys tend to retain sodium.
Both hypoxia and sepsis, which are common in sick neonates, can result in
increased capillary permeability and delay much needed maturation of endocrine
responses governing blood volume, bl ood pressure, and fluid balance.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
210