Measuring the Level of Agreement between Osmometer and Calculated Plasma Osmolalities in Two Species of Chameleons, Furcifer pardalis and Chamaeleo calyptratus

Fluid therapy selection is an important consideration for managing hemodynamically unstable patients. When working with reptiles, limited information is available for species-specific osmolality. To date, osmolality has not been reported in a chameleon. Osmometer measured osmolalities in the veiled and panther chameleons were 330.5 mOsm/kg (range: 285 to 346.50 mOsm/kg) and 308.0 mOsm/kg (294 to 358.50 mOsm/kg), respectively. Bland Altman plots were used to assess the level of agreement between these measured osmolalities and the seven calculated osmolalities. There was poor agreement between the measured and calculated osmolalities. Multiple linear regression was used to develop a species-specific equation for calculated osmolality; this was useful for veiled chameleons (osmolality = 2.098 [Na + ]), but not panther chameleons.  The results of this study suggest that plasma osmolality should be considered species specific in reptiles, and that an osmometer is the preferred method for measuring osmolality in veiled and panther chameleons.