How intravenous nitroglycerine transit time from bag-to-bloodstream can be affected by infusion technique: a simulation study

Objective: To measure the possible delays in intravenous nitroglycerine administration.

Methods: This was a simulation study of sham intravenous nitroglycerine using a standard nitroglycerine titration protocol. Variables studied were (i) common cannulae/needles, (ii) infusion accessories and (iii) presence of a parallel intravenous saline carrier line (or drive line) infusing at 30 mL/h. Outcomes were (i) delay from bag-to-bloodstream arrival and (ii) the dosage showing on the infusion pump when the sham drug first exits the cannula (aka the 'presumed initial dosage').

Results: There was a statistically significant difference in both (i) time-to-bloodstream arrival and (ii) the dosage showing on the infusion pump as the sham first exits the cannula with (i) different cannulae, (ii) different accessories and (iii) presence of a carrier line. The bag-to-bloodstream time varied 10-fold: 197-2062 s. The 'presumed initial dosage' varied sixfold: 5-30 µg/min. Adding the medication to an already flowing carrier line reduced the time for the sham to exit the cannula fourfold: from 2062 to 469 s.

Conclusions: Despite limitations, this study outlines the importance of cannula type, infusion accessories and carrier lines. Larger cannulae and greater priming volumes substantially delay drug delivery, whereas carrier lines/drive lines substantially accelerate drug delivery. Our study also shows how patients could be exposed to clinical delays, as well as incorrect presumptions about drug dosage. Guidelines, and education efforts, should highlight the clinical importance of factors that affect bag-to-bloodstream time.