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.