Objective: To determine whether in healthy horses and those with colic, exposure of peritoneal fluid to room air affects values obtained on biochemical analysis.Study Design: Prospective study.Animals: Adult horses with a primary complaint of acute abdominal pain (n=29) and 12 healthy horses.Methods: Peritoneal fluid was aseptically collected under aerobic and anaerobic conditions. After collection, pH, PCO2, PO2, HCO3 -, Na+, ionized Ca2+, K+, lactate, and glucose were immediately measured using a commercial blood gas analyzer. Biochemical variables were compared between aerobically and anaerobically obtained samples using a paired t-test.Results: In healthy horses, peritoneal fluid samples collected under anaerobic conditions had higher PCO2 and ionized Ca2+ and lower PO2, HCO3 -, and pH compared with samples exposed to air. No differences were observed for K+, Na+, glucose, and lactate. In horses with colic, samples collected anaerobically had higher PCO2, ionized Ca2+, Na+, and glucose and lower PO2, HCO3 -, and pH value compared with samples exposed to air. No differences were observed for K+ and lactate.Conclusion: Exposure of peritoneal fluid to room air had a significant effect on pH, PCO2, PO2, and variables associated or dependent on changes in pH such as HCO3 - and ionized Ca2+. Interpretation of biochemical analysis of peritoneal fluid may be influenced by sample collection method.
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