Blood lactate is a predictor of mortality in critically ill humans and animals. Handheld lactate meters have the potential to be used in the field to evaluate the condition of severely injured rhinoceroses but have not been compared with laboratory-based methods. Agreement between a handheld lactate meter and a laboratory method was assessed, as was the stability of rhino blood lactate in the anticoagulant sodium fluoride/potassium oxalate (fluoride/oxalate). Blood samples were obtained from 53 white rhinos that had been immobilised for management reasons. Lactate was measured by means of a handheld meter using whole blood in heparin (WBHEP), whole blood in fluoride/oxalate (WBFO) and fluoride/oxalate plasma (PFO). Results were recorded in both blood (BL) and plasma (PL) modes and compared to an established laboratory method for measuring plasma lactate. To assess the stability of lactate over time, blood lactate in fluoride/oxalate was measured on the handheld meter at intervals for up to 91 h. Agreement was best using WBFO in PL mode, with small bias (-0.16), tight 95% limits of agreement (LOA) (-1.46, 1.14) and a Pc (95% CI) of 0.97 (0.92, 0.99). The agreement was improved for all sample types when using the PL mode compared to the blood lactate (BL) mode. Blood lactate was stable in fluoride/oxalate for 91 h, with a mean change from baseline of 0.15 (-0.178, 0.478) mmol/L (mean, 95% CI). The handheld meter was found to be suitable for field use in white rhinos but provided more reliable results with the device in PL mode. Furthermore, rhino blood lactate was found to be stable in fluoride/oxalate for as long as 3 days.

The use of serum lactate has become increasingly common in Veterinary Medicine, since it is an excellent marker of tissue oxygenation, elevated in situations of tissue hypoxia, where anaerobic glycolysis is used as an energy source. Studies point out its use in dogs as a prognostic factor in several affections; however it is not commonly used in domestic felines due to the high stress threshold of the species, which may interfere with their values. The aim of the present study was to evaluate serum lactate values in domestic cats during physical restraint and after chemical restraint using the combination of 8mg/kg ketamine-S, 0.4 mg/kg midazolam, and 2 mg/kg Tramadol. To this end, 20 clinically healthy female cats without defined race, from six months to five years of age, were divided into two groups, GPR (n = 10) represented by felines that had only physical restraint and the GCR (n = 10) by felines that underwent physical restraint (TPR) and after 30 hours by chemical restraint (TCR). It was observed that in both groups (GPR and CPR) during physical restraint presented hyperlactatemia (GPR = 6.23 ± 0.9 mmol/L – GCR – Tpr = 6.66 ± 1.59 mmol/L) and mean values of 4.42 ± 1.28 mmol/L during chemical restraint (GCR – Tcr). It was concluded that physical restraint interferes with serum lactate values, with the reduction of such values with the use of chemical restraint in the feline species.