Microbial stability of syringes of anesthetic drugs prepared in the operating room

Abstract Study objective To determine whether microbial contamination of anesthesia syringes prepared in the operating room (OR) become contaminated in a time-dependent fashion. Design Observational. Setting Operating suite in a major university hospital. Patients None (in vitro study). 400 syringes were studied for microbial contamination. Interventions Syringes prepared in the OR by anesthesia personnel were sampled at 1, 2, 3, or 4 h in a sterile fashion and sent to the microbiology laboratory for quantitative culture of any bacteria. Measurements Colony forming units (CFU) per mL of drug were calculated and any identified positive cultures were identified by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry. Logistic regression was used to test the effect of time since preparation on prevalence of positive culture, as was the effect of number of accesses of the syringe and identity of the drug. Main results Overall, 9/400 (2.25%) syringes were positive for bacteria. The median (interquartile range [IQR]) concentration of bacteria among positive cultures was 100 (100,100) CFU. All cultured species were generally nonpathogenic common contaminants. There was no effect of time since preparation, number of accesses of the syringe at the time of sampling, or drug identity (propofol vs. other). Conclusions Contamination of anesthesia syringes is uncommon and occurs at a low overall concentration of bacteria. Contamination does not appear to be time related, and thus calls into question the reasonableness of USP Chapter 797's one-hour requirement.