Comparison of three methods of maintaining a sterile injectate system during cardiac output determinations

Current technique for determining cardiac output involves multiple manipulations of the injectate system and thereby raises the potential for serious infection. A randomized crossover study was undertaken to compare three methods for determining cardiac outputs, focusing on (1) ability to maintain sterile injectate, (2) operator time, and (3) cost effectiveness. The methods compared were the closed-loop injectate delivery, capped-syringe, and double-bag systems. Forty-five subjects were randomly assigned to one of three methods used, then “crossed over” to an alternate method. This resulted in six different groups: (1) 15 subjects assigned to closed loop first, then crossed over to double bag (eight) or capped syringe (seven), (2) 15 subjects assigned to double bag first, then crossed over to closed loop (seven) or capped syringe (eight), and (3) 15 subjects assigned to capped syringe first, then crossed over to double bag (seven) or closed loop (eight). Quantitative cultures of sample injectates served as indicators of contamination. The Wilcoxon signed rank analysis showed no statistical difference (p > 0.9) in patient or catheter caracteristics between treatment groups. None of 30 cultures from the closed-loop method yielded bacterial growth, compared to 6 of the 30 cultures positive from each of the other methods (p < 0.0001). The closed-loop method also required less operator time and was more cost effective than the two alternate methods examined.