The effect of urine flow rate on urinary bladder temperature in critically ill adults.

Objective: This study determined the effect of urine flow rate on bladder temperature in critically ill adults.

Design: The design was pretest-posttest quasi-experimental.

Setting: The study took place at a tertiary care center in western Washington.

Patients: Convenience sampling resulted in an intervention group of 35 and a control group of 25 patients who had undergone cardiac surgery.

Intervention: A diuretic, administered intravenously as part of usual postoperative care, provided variation in the urine flow rate.

Methods: Urinary bladder temperature (UBT), pulmonary artery temperature (PAT), and urine flow rate data were collected at 2-minute intervals for 60 minutes preintervention and 60 minutes postintervention.

Results: Unlike the control group, who experienced no significant change in mean urine flow rate or gradient (0.00 degrees C) from prephase to postphase, the intervention group experienced both a significant and close to 10-fold increase in urine flow rate ( P < .001) and a significant decrease (0.09 degrees C) in mean UBT-PAT gradient ( P < .001). The change in gradient experienced by the intervention group compared with the control group was the result of a net heat loss of 0.05 degrees C in UBT and a net heat gain of 0.04 degrees C in PAT.

Conclusions: Although statistically significant, the mean change in UBT-PAT gradient between the intervention and control groups was not clinically important, indicating that bladder temperature remains reliable even with significant changes in urine flow rate.