Transfusion of rhodococcal hyperimmune plasma to newborn foals does not markedly alter serum electrolyte or protein concentrations.

Objective: To determine the effects of transfusion of Rhodococcus equi hyperimmune plasma (REHIP) on serum electrolyte and protein concentrations in neonatal foals.

Methods: A prospective observational study of 355 privately owned Thoroughbred foals from 13 farms in New York and cross-sectional study of REHIP samples. Blood was collected immediately before and after transfusion of either 1 or 2 L of REHIP to foals, and serum samples were separated and frozen until tested for concentrations of sodium (Na), potassium (K), chloride (Cl), total protein (TP), albumin, and globulins. Samples (n = 90) of REHIP were tested for concentrations of Na, K, Cl, TP, albumin, and globulins by the same methodology.

Results: REHIP transfusion resulted in small but significant increases in serum Na, albumin, globulins, and TP concentrations and small but significant decreases in serum Cl and K concentrations. Serum protein concentrations were significantly greater in foals transfused with 2 L than with 1 L. No adverse effects of transfusion were noted in any foals. In REHIP, concentrations of Na were above the serum reference interval.

Conclusions: Magnitudes of changes in serum electrolyte and protein concentrations were small. Although changes were greater for foals transfused with 2 L compared to 1 L, no foals developed marked derangements in measured parameters. Concentrations of measured parameters in REHIP did not vary greatly among manufactured lots or years.

Clinical relevance: Transfusion of REHIP to foals does not appear to have marked effects on serum concentrations of electrolytes or proteins despite the relatively high Na concentration in REHIP.