The Incidence of Propofol Vial Coring with Blunt Needle Use Is Reduced with Angled Puncture Compared with Perpendicular Puncture

To the Editor We have noticed that coring occurs when puncturing the rubber stopper of 20 mL 1% propofol vials manufactured by AstraZeneca (London, United Kingdom) and using the BD™ short plastic blunt fill needles. We sought to determine the incidence of coring and whether coring can be reduced with different angles of needle puncture. Basic vector principles dictate that, for a given force (i.e., needle impalement of the medication rubber stopper), the amount of force required to pierce the stopper in the vertical plane is reduced with an angled approach (approximately 45°) compared with a perpendicular approach (approximately 90°). This methodology has been suggested to be effective with sharp beveled needle puncture of the rubber stopper.1 Therefore, we hypothesized that an angled approach will reduce the incidence of coring with this particular blunt fill needle. The rubber stoppers of 20 mL 1% propofol vials (Diprivan®; AstraZeneca Canada, Mississauga, Ontario) were punctured with the BD™ short plastic blunt fill needles. The stoppers were punctured in 1 of 2 ways: a perpendicular puncture (approximately 90°; Fig. 1A) and an angled puncture (approximately 45°; Fig. 1B). After puncture occurred, the vials were thoroughly inspected with the naked eye to look for coring. During this current investigation, published data indicating the incidence of coring with blunt needles were approximately 29%.2 We calculated that the minimal sample size needed to effect a 50% reduction with 80% power and alpha error of 0.05 was 137 for each group. To strengthen the study, we increased our sample size to approximately 250 per group. A 2 × 2 contingency table was used to summarize the data, and Fisher exact test was used to analyze the results.Figure 1: Comparison of actual vial approaches with the BD™ plastic blunt needle. A, Perpendicular puncture is a 90° approach to the vial. B, Acute angle puncture is an approximately 45° approach to the vial.The contingency table is presented in Table 1. Coring occurred in 29.2% of the perpendicular puncture group and 15.2% in the angled puncture group (P = 0.0001). There was a 47.8% reduction in coring (95% confidence interval, 26.8%–63.0%) when the angled puncture technique was used. The primary finding is that the frequency of coring with blunt needle impalement of the rubber stopper of Diprivan® vials is reduced with angled puncture compared with perpendicular puncture. By using an angled puncture technique, we achieved an almost 50% reduction in coring.Table 1: Contingency Table for Propofol Vial Coring with Blunt Fill Needles: Straight Versus Acute Angle PunctureThe clinical significance of coring and its microembolic consequences is not well described, likely because it does not have an immediate effect when it is accidentally injected.3,4 Certain manufactures have booklets on “Particulate Contamination” (e.g., Brauna) and describe the ways to prevent intravascular contamination from occurring, which includes the use of in-line IV filters and filter needles for medication aspiration. However, when aspirating propofol, these needles cause slow aspiration as well as the formation of many air bubbles, which can be an inconvenience in a busy practice. The BD™ short plastic blunt fill needle allows for rapid aspiration of propofol with minimal air bubbles, and we nonetheless report a simple technique to reduce the chances of obtaining a core with these blunt needles. It has been suggested that the use of blunt fill needles may reduce the risk of coring (while reducing the incidence of needle-stick injuries)1; however, this current study revealed that coring with the BD™ blunt fill needle still incurred a 29% incidence of coring. Although we only investigated Diprivan® vials, these findings may potentially be expanded to other medication vials. In addition to using this technique to puncture vials, we still recommend that all vials and syringes be inspected rigorously after puncture and aspiration to ensure that no cores can be seen, irrespective of angle of approach of puncture with blunt needles. Ferrante S. Gragasin, MD, PhD, FRCPC Z. A. Neethling van den Heever, MB, ChB, DA (SA) Department of Anesthesiology and Pain Medicine University of Alberta Edmonton, Alberta, Canada [email protected]

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