Category: Professional Posters
Purpose: Intravenous fluid administration set back-check valves are designed to close in response to the pressure differential between the primary and secondary tubing segments to ensure complete, uninterrupted delivery from the secondary container. The pressure differential is affected by the primary and secondary container head-height differential and the secondary infusion flow rate. Incomplete back-check valve closure may lead to “sympathetic flow” of primary fluid infusing concurrently with the secondary fluid. This study evaluates whether clinically relevant head-height differentials and secondary flow rates result in incomplete back-check valve closure and sympathetic flow with infusion pump administration sets.
Methods: This study was conducted in a laboratory setting. Two identical commercially available infusion pumps (Pump A and Pump B) were selected for use with two identical dedicated primary administration sets containing back-check valves upstream of the pump. The pumps were configured to deliver secondary infusions at head-height differentials of 20, 16, 8, 4, and 0 inches (the head-height scenarios). At each head-height differential, the secondary infusion was programmed to be infused at 100, 200, 300, 400, and 500 ml/hour (the flow rate scenarios). Fluid flow rates and volumes were assessed continuously by weighing the primary and secondary bags as well as the collection reservoir. The primary outcome measure was the total volume of sympathetic flow delivered in each infusion scenario. The secondary outcomes were the flow rates from primary and secondary containers over time.
Results: At a head-height differential of 20 inches, Pump A delivered negligible sympathetic flow until reaching a secondary flow rate of 500ml/hour which resulted in sympathetic flow of 3.2%. At a head-height differential of 16 inches, Pump A delivered sympathetic flows of 0.1%, 0.7%, 4.6%, 10.7%, and 22.4% with the increasing flow rate scenarios. At head-height differentials of 20 and 16 inches, Pump B delivered negligible sympathetic flow.
At head-height differentials of 8, 4, and 0 inches, sympathetic flow was present with both Pumps A and B. The sympathetic flow data is presented here as Pump A%/Pump B%. In one instance, data is not available which is noted as NA. At a head-height differential of 8 inches, Pump A and B sympathetic flows were 0.4/0.1%, 3.8/3.5%, 11.5/9.7%, 20.7/15.2%, and 30.1/24.5% with the increasing infusion rates. At a head-height differential of 4 inches, Pump A and B sympathetic flow rates increased to 4.9/1.3%, 15.7/9.0%, 28.4/18.3%, 41.2/28.4%, and 45.2/NA% with the increasing infusion rates. At a head-height differential of 0 inches, sympathetic flows were 21.6/17.4%, 37.1/29.0%, 50.8/38.9%, 59.7/46.3%, and 68.3/52.8% with the increasing infusion rates.
Conclusion: Sympathetic flow from the primary container during a secondary infusion was observed with two infusion pumps with decreasing head-height differentials and increasing secondary flow rates. These results suggest that administration set back-check valve closure may be incomplete, and that secondary infusion delivery may be inconsistent across devices in clinically representative circumstances. The potential patient impacts from sympathetic flow are delayed secondary medication administration and delivery of the primary fluid at the programmed secondary rate. Further studies are required to confirm and evaluate the clinical significance of these results.