Effects of aerobic and anaerobic fluid collection on biochemical analysis of peritoneal fluid in healthy horses and horses with colic.
Authors: Romero Alfredo E, Nieto Jorge E, Dechant Julie E, Hopper Kate, Aleman Monica
Journal: Veterinary surgery : VS
Summary
# Editorial Summary When evaluating peritoneal fluid biochemically to assess colic severity and aetiology, the collection method materially affects results: aerobic sampling (exposure to room air) significantly alters pH, blood gas parameters, and pH-dependent analytes compared to anaerobic collection. Researchers compared paired peritoneal fluid samples from 29 colic cases and 12 healthy horses, collecting fluid aseptically under both aerobic and anaerobic conditions, then immediately analysing pH, blood gases (PCO₂, PO₂), bicarbonate, electrolytes (sodium, potassium, ionised calcium), lactate and glucose. Anaerobic samples consistently showed higher PCO₂ and lower PO₂ and pH across both groups; ionised calcium was elevated and bicarbonate reduced under anaerobic conditions, whilst in colic cases sodium and glucose were also higher anaerobically—notably, lactate (often interpreted as an indicator of ischaemic tissue damage) showed no difference between collection methods in either group. Because air exposure significantly distorts gas tensions and pH-dependent variables that clinicians use to estimate intestinal viability and guide surgical decision-making, adopting standardised anaerobic collection protocols is essential for reliable peritoneal fluid interpretation in colic cases.
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Practical Takeaways
- •Use anaerobic collection techniques for peritoneal fluid analysis when possible—aerobic exposure alters critical diagnostic values (pH, blood gases, calcium) that guide colic case management
- •If comparing peritoneal fluid results between cases or over time, ensure consistent collection methodology; mixing aerobic and anaerobic samples may lead to misinterpretation of disease severity
- •Lactate and potassium measurements remain valid indicators of peritoneal pathology regardless of collection method, so prioritize these if anaerobic sampling is unavailable
Key Findings
- •Anaerobic collection of peritoneal fluid produced significantly higher PCO₂ and ionized Ca²⁺ compared to aerobic collection in both healthy and colic horses
- •Aerobic exposure significantly lowered pH, PCO₂, and HCO₃⁻ while increasing PO₂ in peritoneal fluid samples
- •Sample collection method (aerobic vs anaerobic) significantly affects interpretation of pH-dependent biochemical variables including HCO₃⁻ and ionized Ca²⁺
- •K⁺ and lactate values were unaffected by collection method, making them more reliable biomarkers regardless of sampling technique