Performance of the On-Q pain infusion device during changes in environmental temperature.

Background: The On-Q infusion device is an elastomeric device with a flow regulator that controls the flow of a local anesthetic agent through a peripheral catheter. As variations in external temperature may affect the diameter of the tubing or viscosity of the fluid, it is feasible that alterations in flow may be caused by such temperature variations. This study evaluates the performance of this device during variations in environmental temperature.

Methods: The disposable 400 ml On-Q pain ball infusion devices were filled and connected to a single, end hole infusion catheter and set to infuse at 14 ml·h(-1) . Eighteen devices were used in the study (six of each at three different temperatures). The temperatures included hot (54°C), room temperature (21°C), and cold (6°C). The devices were allowed to flow for 24 h. The fluid delivered during each 12-h period was measured using a graduated column.

Results: There were significant differences in the output from the devices at the hot (54°C) temperature and the cold (6°C) temperature when compared to room temperature (21°C). When compared to room temperature, the output decreased to 67% and 54% of the control group (room temperature) during hours 0-12 and 12-24, respectively, in a cold environment (6°C). An increased external temperature resulted in a greater output from the devices. When compared to the room temperature devices, the output was 49% higher during the first 12 h and 40% higher during the second 12 h at an external temperature of 54°C.

Conclusions: This preliminary investigation demonstrates what may be clinically significant changes in output from the On-Q pain device based on the external temperature. These alterations in flow could result in inadequate analgesia or even potentially toxicity if these devices are used in smaller patients especially the pediatric population.