Central venous catheter infusions: a laboratory model shows large differences in drug delivery dynamics related to catheter dead volume.

OBJECTIVE

Central venous catheters (CVCs) are conduits for drug infusions. Dead volumes of different CVC lumens vary considerably. This study quantitatively evaluated drug delivery dynamics of CVCs in a laboratory model of continuous drug infusion.

DESIGN

CVCs studied included a triple-lumen catheter (16-gauge and 18-gauge lumens), the proximal infusion port of a pulmonary artery catheter, and a 9-Fr introducer sheath, with and without a pulmonary artery catheter in the lumen. One syringe pump infused a carrier. A second pump infused the model drug methylene blue (3 mL/hr), joining the carrier immediately upstream of the CVC. Samples were collected every minute for quantitative analysis.

SETTING

Laboratory model.

SUBJECTS

None.

INTERVENTIONS

At low fixed flow rates, experiments characterized drug delivery kinetics of different CVCs. Data collection then assessed effects of increased carrier flow.

MEASUREMENT AND MAIN RESULTS

The time to steady-state delivery after initiation of methylene blue infusion differed between CVCs. At a carrier flow of 10 mL/hr, the fastest achievement of steady-state delivery was with the 18-gauge lumen of a triple-lumen catheter. The 9-Fr introducer had the slowest time to achieve steady-state delivery. Other CVCs had intermediate kinetics. Reducing drug delivery from steady state to zero after cessation of methylene blue infusion was fastest with the 18-gauge lumen and slowest with the 9-Fr introducer. Increasing carrier flow rates from 10 to 60 mL/hr hastened the time to target for initiation and cessation of methylene blue delivery.

CONCLUSIONS

Experiments demonstrate large differences between CVCs in the dynamics for delivery of model drug methylene blue. Achieving targeted steady-state delivery, and termination of a planned continuous drug infusion, may be far slower than typically appreciated. Delivery kinetics depend on the dead volume and the rate of carrier flow. Safe and effective management of continuous drug infusions depends on understanding the dynamics of the delivery system.