Evaluation of serial venous and arterial lactate concentrations in healthy anesthetized sheep undergoing ovariectomy

Objective: To determine if lactate concentrations in jugular venous and auricular arterial blood differ in anesthetized sheep. Study design: Prospective, controlled experimental study. Animals: Twelve healthy adult ewes, 4-7 years and weighing 62-77 kg. Methods: Jugular venous blood was collected before anesthesia (PreO_v) for measurement of lactate concentration, packed cell volume and total protein. Ewes were administered a standard anesthesia protocol. Jugular venous (IntraO_v) and auricular arterial (IntraO_a) blood samples were obtained 40 minutes after induction of anesthesia, and again in recovery (PostO_v and PostO_a). An additional blood sample was drawn 6 weeks post-operatively from non-fasted sheep (NF_Lact). Lactate concentrations were compared among PreO_v, IntraO_v and IntraO_a, PostO_v and PostO_a, and between PreO_v and NF_Lact with paired t-test and repeated measure analyses of variance (anova) with PreO_v as a covariate (p ≤ 0.05). Results: IntraO_v lactate concentration had decreased from PreO_v There were significant differences between arterial and venous IntraO and PostO lactate concentrations. There was no significant difference between IntraO and PostO, or PreO_v and NF_Lact. Conclusions and clinical relevance: Lactate concentrations were significantly lower in anesthetized sheep compared to non-anesthetized sheep. Lactate concentrations in venous blood were higher than in arterial blood. Therefore, anesthetic status and sampling site should be considered when interpreting lactate concentrations, and the sampling site should be consistent for repeated measurements.