A Retrospective Analysis of Liberal Fluid Therapy and Total Protein Changes in 124 Horses Undergoing Colic Surgery

Perioperative fluid therapy in horses undergoing colic surgery should be individualised to avoid complications associated with both hypo- and hypervolaemia. This retrospective study evaluated the haemodynamic effects of a liberal perioperative fluid therapy approach, focusing on total plasma protein (TPP) changes. Medical records of 124 horses undergoing colic surgery between March 2018 and June 2020 were reviewed. Packed cell volume (PCV) and TPP were assessed preoperatively, after surgery, on postoperative days (POD) 2, 5 and 7, and at long-term follow-up. Horses were stratified according to postoperative TPP (≤5 vs. >5 g/dL) and lesion type (strangulating vs. non-strangulating). All horses received crystalloids (median 34.3 mL/kg; range 9-99 mL/kg), while 41/124 also received colloids (HES 130/0.4, 4 mL/kg). TPP was significantly lower at anaesthetic recovery than at admission at the population level (p < 0.0001). At the individual level, recovery TPP was lower than POD7 in 106/124 horses (85.5%), while 52/124 horses (41.9%) had a recovery TPP concentration ≤ 5 g/dL. Values progressively returned toward baseline from POD2 onwards. In non-strangulating lesions, horses with TPP ≤ 5 g/dL received substantially greater crystalloid volumes than horses with TPP > 5 g/dL (56.8 vs. 31.5 mL/kg), whereas PCV changes were comparable between groups. The association between crystalloid dose and TPP reduction remained significant after adjustment for lesion type and intestinal tract involved; however, residual confounding by unmeasured indicators of disease severity cannot be excluded. Greater cumulative crystalloid administration was associated with a greater magnitude of TPP reduction. Horses with post-recovery TPP ≤ 5 g/dL had a significantly longer hospital stay than those with TPP > 5 g/dL (p = 0.006). Serial TPP monitoring may provide a practical, real-time measure of changes in plasma protein concentration and perioperative haemodilution; its role in guiding fluid administration requires prospective validation.