[Evaluation of the temperature dependent flow rate in three portable epidural infusion devices]

We evaluated the temperature dependent flow rate of local anesthetics, 0.25% bupivacaine, in three portable epidural infusion devices, Infusor of Baxter, Surefuser-A of Nipro and Excelfuser of Kobayashi Medical. Flow rate was calculated using a digital precision scale in a large temperature controlled incubator. In two preliminary studies the temperature was 25 degrees C at the patient's side and 33 degrees C on the patient's skin. All the devices increased the flow rate with an increase in temperature and there were no clinically significant differences in the infusion quality and stability. It should be remembered that the flow rate of Excelfuser is 30% greater at 33 degrees C than the inscribed value, because this calibration temperature of 22 degrees C (a new type calibrated at 32 degrees C will come to the market soon) is about 10 degrees C lower than that of others. In critical patient care we should watch the temperature of the flow controller. Additionally, according to our viscosity measurement study, we conclude that temperature depended flow rate changes are related not to the inner diameter of the flow controller, but to the viscosity of local anesthetics.