A Prospective Randomised Study to Compare the Effects of Preoperative Hypertonic Saline or Pentastarch on Haematological Variables and Long-Term Survival of Surgical Colic Cases

Aims To compare the effects of hypertonic saline and pentastarch on packed cell volume (PCV) and total protein (TP) immediately preoperatively and on long-term survival of horses undergoing emergency exploratory laparotomy. Methods One hundred horses presenting to the Philip Leverhulme Equine Hospital between 2004 and 2008 with signs of abdominal pain and PCV ≥45% were recruited. Horses were randomly allocated to receive 4 ml/kg bwt of either hypertonic saline (HS; Vetivex, 7.2%; n = 49) or pentastarch (PS; Haes-Steril, 10%; n = 51) preanaesthesia. Blood samples were collected at presentation and post fluid resuscitation. Horse survival was tracked for 4 years following the final recruited case. Results There were no significant differences between treatment groups at presentation for: age (HS, mean 13 ± 6 years; PS, mean 14 ± 6 years); body mass (HS, median 516 [130–698] kg; PS, median 525 [312–660] kg); sex (HS, 1 stallion, 34 geldings, 16 mares; PS, 2 stallions, 32 geldings, 15 mares); baseline PCV (HS, median 52 [46–70]%; PS, median 50 [45–70]%); baseline TP (HS, median 72 [46–103] g/l; PS, median 72 [50-106] g/l); and heart rate (HS, mean 80 ± 20 beats/min; PS, mean 77 ± 18 beats/min) at presentation. Hypertonic saline treatment resulted in a significantly greater reduction in both PCV (HS, mean 13 ± 7%; PS mean 7 ± 5%; P<0.001) and TP (HS, median 16 [6–32] g/l; PS, median 2 [-8 to 17] g/l; P<0.001), compared with pentastarch. There was no significant difference in long-term survival between treatments (Cox proportional hazards model, P = 0.73). Conclusions and practical significance Despite the greater reduction in haemoconcentration and likely reduction in blood viscosity incurred by HS, no benefit to overall long-term survival was demonstrated. In a clinical setting, either of these fluids remains appropriate for preoperative fluid resuscitation in colic horses. Acknowledgements All the veterinary anaesthetists who assisted in data-gathering. Ethical animal research Permission for this study was granted by the Ethical Review Committee of the University of Liverpool's Veterinary School. Signed owner consent was obtained for all cases. Sources of funding: None. Competing interests: None.