Functional evaluation and practice survey to guide purchasing of intravenous cannulae

There are wide variations in the physical designs and attributes between different brands of intravenous cannulae that makes product selection and purchasing difficult. In a systematic assessment to guide purchasing, we assessed two cannulae - Cannula P and I. We proposed that the results of in-vitro performance testing of the cannulae would be associated with preference after clinical comparison.

We designed an observer-blinded randomised head-to-head trial between the 18, 20 and 22 gauge versions of Cannula P and I. Our primary end-point was pressure (mmHg) generated during various flow rates and our secondary end-point was the force (Newton) required to slide the catheter away from the needle. This was followed by a prospective electronic survey following a two-week clinical trial period.

The mean difference in resistance between Cannula P and I was: 307 mmHg.L-1.hr-1 (95% CI: 289-325, p < 0.001) for 22G; 135 mmHg.L-1.hr-1 (95% CI: 125-144, p < 0.001) for 20G; and 27 mmHg.L-1.hr-1 (95% CI: 26-28, p < 0.001) for 18G. The mean difference in the force needed to displace the catheter away from its needle was: 1.41 N (95% CI: 1.09-1.73, p < 0.001) for 22G; 0.19 N (95% CI: -0.04-0.41, p = 0.12) for 20G; and 1.96 N (95% CI: 1.40-2.52, p < 0.001) for 18G. After a trial period, all 16 anaesthetist who had used both cannulae preferred Cannula I to P.

The evaluation process described here could help hospitals improve efficient product selection and purchasing decisions for intravenous cannulae.