Comparison of flow pressures in different 3-way infusion devices: an in-vitro study.

Background: The use of multiple infusions through one cannula is an increasingly common practice in anaesthesia. High pressures in the line often lead to occlusion alarms and pump disconnection. In this study, we aim to determine the pressures generated in common 3-way infusion devices, using simple low-cost equipment available and currently in use in the operating theatre environment.

Methods: We compared three different common and commercially available 3-way infusion devices that allowed multiple infusions through one cannula in vitro. One with anti-siphon valves, one without valves, and serial extension sets with side ports connected in series. An invasive blood pressure transducer was used to monitor line pressure. Seven different infusion rates were used to simulate different infusions.

Results: 3-way infusion devices with anti-siphon valves have 5.5 times the infusion pressures compared to devices without valves ( P  < 0.001). The highest pressures obtained across all devices were at the highest flow rate studied (400 ml/hr); this was 243 mmHg in the 3-way device with anti-siphon valves, compared to only 44 mmHg in the 3-way device without valves and 36 mmHg in the serial extension sets. Serial extension sets have the lowest pressures across all flow rates when compared to 3-way devices without valves. ( P  = 0.0001).

Conclusions: The presence of anti-siphon valves generate very high pressures in infusion lines that can contribute to occlusion alarm disconnection of a pump. However, when measured alone and in-vitro, these pressures are not sufficient to trigger occlusion alarms. There are 3-way infusion devices without anti-siphon valves that have lower line pressures, but clinicians should be aware of negative pressure scenarios which can lead to siphoning when using them.