Effect of polymyxin B on survival in strangulating small intestinal lesions

Summary Background Polymyxin B is an antibiotic that targets gram‐negative bacteria by binding to lipopolysaccharide on the outer membrane of the bacteria, the endotoxin responsible for triggering systemic inflammation. Endotoxaemia is common in horses with small intestinal strangulating lesions. Although polymyxin B has been shown to reduce endotoxaemic effects in experimental studies, the efficacy in clinical cases remains unclear. Objectives To investigate whether polymyxin B influences survival to discharge on both an univariable and multivariable level. To investigate the effect that confounding factors may have on the survival to discharge. Study Design Prospective, controlled study, alternating treatment and control groups. Methods Case details, lesion, segment affected, length of ischaemic intestine and type of anastomosis (if required) were recorded using a data collection sheet created by one clinician. All horses were alternately assigned to receive polymyxin B or nothing and their survival to discharge was recorded. The use of post‐operative lidocaine and clinical parameters at admission were also recorded. Results Univariable analysis showed a higher survival rate in horses that received polymyxin B compared with those that did not. Multivariable logistic regression, when controlling for heart rate, PCV and age, abolished this effect. Findings show polymyxin B was not an independent predictor of survival. Main Limitations Limited case numbers, non‐blinded study, long study period, lack of placebo and lack of confirmation of endotoxaemia. Conclusions The use of polymyxin B in strangulating small intestinal lesions was not found to be statistically significant on survival to discharge as an independent predictor.