An Exploratory Evaluation of the Frequency of Perioperative Changes in Electrolyte, Acid-Base, Creatinine, Glucose, and Lactate Variables in Dogs and Cats Undergoing Cranial Surgery for Tumor Resection.

OBJECTIVE:To explore the frequency and severity of abnormalities in perioperative point-of-care bloodwork in dogs and cats undergoing cranial surgery for tumor resection with particular emphasis on dyskalemia development. STUDY DESIGN:Retrospective observational study. ANIMALS:A total of 61 dogs and 14 cats undergoing cranial surgery for tumor resection between 2009 and 2023. METHODS:Medical records and point-of-care blood variables of dogs and cats undergoing surgical tumor resection were reviewed. Electrolyte, acid-base, creatinine, glucose, and lactate concentrations were recorded preoperatively, intraoperatively, and immediately postoperatively and compared to reference intervals. Medications and IV fluids administered were recorded. RESULTS:Intraoperative mannitol was administered to 24/61 (39%) dogs and 5/14 (36%) cats, and hypertonic saline to 1/61 dog. Two of 75 (3%) animals experienced mild intraoperative hyperkalemia (<5.9 mmol/L), none experienced moderate or severe hyperkalemia. Intraoperative hypokalemia was present in 6/75 (8%) animals. Mean (±SD) preoperative potassium concentration ([K+]; mmol/L) was 3.75 (±0.45), increasing to 3.91 (±0.46) intraoperatively, and decreasing postoperatively to 3.74 (±0.46). Intraoperative [K+] was significantly higher than postoperative (p < .001). Intraoperative bicarbonate, sodium, and ionized calcium concentrations were lower than preoperative concentrations but returned to baseline postoperatively and largely remained within institutional reference intervals. CONCLUSION:Intraoperative alterations in [K+], bicarbonate, sodium, and ionized calcium concentrations occurred during cranial surgery in dogs and cats, but were generally mild and transient. Clinically relevant hyperkalemia was not observed in this cohort. CLINICAL SIGNIFICANCE:Clinically significant hyperkalemia may be uncommon in veterinary cranial surgery, but routine perioperative point-of-care bloodwork remains advised to monitor electrolyte and acid-base status.