Rapid infusion pump overestimates delivered flow during rapid vascular filling: a bench study

Despite now being rarely used in the prehospital and emergency department arena because of their excessive length and low inner diameter, narrow-bore central venous catheters (CVC) are sometime used to perform fluid resuscitation using a rapid infusion pump to enhance delivered flow. In this bench study, we tested the hypothesis that the delivered flow rate downstream from the catheter connected to a rapid infusion pump would be significantly lower than the preset flow rate, and this difference would be affected by the catheter size.

Eight units of each type of catheter [two 15 and 20 cm narrow-bore CVC and three 14, 16 and 18 G peripheral venous catheters (PVC)] were connected to a rapid infusion device and were tested with physiological saline. Measurements were repeated using glycerol solution with a viscosity similar to that of packed red blood cells. Infusion pump flow rates were preset to 100, 200, 300 and 400 ml/min. Flow rates were measured downstream from catheters, each connected to a rapid infusion device.

The downstream flow rate remained lower than the preset flow rate except with the 14 and the 16 G PVC at 100 ml/min (P<0.001). The type of catheter significantly impacted the flow rates measured with physiological saline (F4,105=1008.83, P<0.001) and glycerol solution (F4,105=1843.46, P<0.001).

Using a rapid infusion device, the delivered flow rate was lower than the preset flow rate. Even PVCs are better than narrow-bore CVC, neither is the most suitable cannula for patients requiring massive resuscitation.