Determinination of plasma osmolality and agreement between measured and calculated values in healthy adult Hispaniolan Amazon parrots (Amazona ventralis)

Objective - To determine plasma osmolality in healthy adult Hispaniolan Amazon parrots (Amazona ventralis) and validate osmolality equations in these parrots. Animals - 20 healthy adult Hispaniolan Amazon parrots. Procedures - A blood sample (0.5 mL) was collected from the right jugular vein of each parrot and placed into a lithium heparin microtainer tube. Samples were centrifuged, and plasma was harvested and frozen at -30°C. Samples were thawed, and plasma osmolality was measured in duplicate with a freezing-point depression osmometer. The mean value was calculated for the 2 osmolality measurements. Results - Plasma osmolality values were normally distributed, with a mean ± SD of 326.0 ± 6.878 mOsm/kg.The equations (2 X [Na⁺ + K⁺]) + (glucose/18), which resulted in bias of 2.3333 mOsm/kg and limits of agreement of -7.0940 to 11.7606 mOsm/kg, and (2 X [Na⁺ + K⁺]) + (uric acid concentration/16.8) + (glucose concentration/18), which resulted in bias of 5.8117 mOsm/kg and limits of agreement of -14.6640 to 3.0406 mOsm/kg, yielded calculated values that were in good agreement with the measured osmolality. Conclusions and Clinical Relevance - IV administration of large amounts of hypotonic fluids can have catastrophic'consequences. Osmolality of the plasma from parrots in this study was significantly higher than that of commercially available prepackaged fluids. Therefore, such fluids should be used with caution in Hispaniolan Amazon parrots as well as other psittacines. Additional studies are needed to determine whether the estimation of osmolality has the same clinical value in psittacines as it does in other animals.