To investigate the effect of urinary flow rate on the urinary bladder temperature, we compared the accuracy and precision of urinary bladder temperature with oesophageal temperature at both high and low urine flow rates.

Twenty-four patients ASA physical status I or II who were undergoing tympanoplasty were randomly assigned to two groups with different intravenous fluid volumes: high (10 mL kg−1 h−1, n = 12) and low (3 mL kg−1 h−1, n = 12). General anaesthesia was induced with propofol and maintained with sevoflurane (1.5–2.5%) in nitrous oxide and oxygen. Urinary bladder temperature was measured using a Foley urinary catheter; distal oesophageal temperature was measured using a stethoscope thermocouple. These temperatures were measured every 5 min during surgery and the accuracy and precision of urinary bladder temperature with oesophageal temperature were determined using regression and Bland and Altman analyses.

The correlation coefficient for oesophageal and urinary bladder temperature was 0.90 in the high urinary volume group and 0.75 in the low urinary volume group. The offset (oesophageal–urinary bladder) was −0.13 ± 0.32°C and −0.46 ± 0.45°C, respectively.

Urinary bladder temperature appears to be more accurate at high urinary flow rates than at low urinary flow rates for clinical use.