Reliability of the Enterprise Point-of-Care (EPOC) blood analyzer's calculated arterial oxygen-hemoglobin saturation in immobilized white rhinoceroses (Ceratotherium simum)

Abstract

Background Enterprise Point-of-Care (EPOC) blood analysis is used routinely in wildlife veterinary practice to monitor blood oxygenation, but the reliability of the EPOC calculated arterial oxygen-hemoglobin saturation (cSaO2) has never been validated in the white rhinoceros (Ceratotherium simum), despite their susceptibility to hypoxemia during chemical immobilization.

Objectives We aimed to evaluate the reliability of the EPOC cSaO2 by comparing it against arterial oxygen-hemoglobin saturation (SaO2) measured by a co-oximeter reference method in immobilized white rhinoceroses.

Methods Male white rhinoceroses in two studies (both n = 8) were immobilized by darting with different etorphine-based drug combinations, followed by butorphanol or saline (administered intravenously). Animals in both studies received oxygen via intranasal insufflation after 60 min. Blood samples were drawn, at predetermined time points, from a catheter inserted into the auricular artery and analyzed using the EPOC and a co-oximeter. Bland–Altman (to estimate bias and precision) and area root mean squares (ARMS) plots were used to determine the reliability of the EPOC cSaO2 compared with simultaneous co-oximeter SaO2 readings.

Results The rhinoceros were acidotic (pH of 7.3 ± 0.1 [mean ± standard deviation]), hypercapnic (PaCO2 of 73.7 ± 10.5 mmHg), and normothermic (body temperature of 37.4 ± 1.8°C). In total, 389 paired cSaO2-SaO2 measurements were recorded (the cSaO2 ranged between 13.2% and 99.0%, and the SaO2 ranged between 11.8% and 99.9%). The EPOC cSaO2 readings were unreliable (inaccurate, imprecise, and poor ARMS) across the entire saturation range (bias −6%, precision 5%, and ARMS 8%).

Conclusions The EPOC cSaO2 is unreliable and should not be used to monitor blood oxygenation in immobilized white rhinoceroses.