Administration of intravenous drugs during anaesthesia: a potential contribution to postoperative infection

Abstract

Postoperative infections are a major cause of harm to patients, and add substantially to the cost of healthcare throughout the world. Emerging data suggest that the way anaesthetists draw up and administer intravenous drugs to patients may be a previously unsuspected vector for postoperative infections. I aimed to determine whether the intravenous bolus drugs drawn up and injected by anaesthetists in the operating theatre become contaminated by micro-organisms, through such failures. I conducted a study to answer the following questions: (1) are there failures in aseptic technique specifically during the drawing up and injecting of intravenous by anaesthetists? And, if so (2) do these failures result in the injection of micro-organisms during simulated anaesthesia? In this study, micro-organisms were isolated from five (13%) of 38 collection bags from 20 simulated anaesthetics, and from the contents of ten of 197 (5%) used syringes. I then asked whether similar failures occur in clinical settings. To answer this question, I developed novel methods, (1) to incorporate 0.2 μm filter units into patients’ intravenous lines, and (2) to identify microbiological contamination (if present) from the filter units. In 300 surgical cases, anaesthetists injected all bolus drugs, except propofol and antibiotics, through these filter units. Micro-organisms were isolated in 19 (6.3%) of 300 cases, and from residual drug in 55 of 2318 (2.4%) used syringes. The next step in this research will be to evaluate the clinical importance of these inadvertently injected micro-organisms - do they make a clinically important contribution to the incidence of postoperative infection? Therefore, in the final part of my thesis I present a protocol for an adequately sized, multi-centre randomised study to definitively answer the question: can postoperative infections be reduced by the use of filter units in selected groups of patients? Thus, I have shown that micro-organisms with the potential to cause postoperative infection are being injected into at least some patients during the administration of intravenous bolus drugs during anaesthesia. These findings, added to those of other investigators, suggest that anaesthetists may well be contributing to the clinical problem of postoperative infection, and justify further work to understand how to effectively improve this aspect of patient care.