Accidental renal injury by an external heating device during surgery in rats.

Hypothermia can be caused by anaesthesia and/or surgery and represents a daily challenge in the operating room. Experimental animal surgery settings typically use heating pads or warming blankets to maintain the rodent's body temperature during long-lasting experiments. Warming is crucial in small animal experiments because these animals quickly lose temperature due to their large body surface to body weight ratio. While establishing a left ventricular infarction model in rats, we inserted a rectal temperature probe. The heating pad's set point was 37°C. Although a dual set point control circuit should prevent overheating, we observed a maximum heating pad's surface temperature of 43°C between the animal's back and the surface of the heating pad. At the end of the experiments, which lasted up to 8 h, the animals showed severe haematuria and segmental kidney damage. We hypothesized that overheating of the heating pad and uneven distribution of temperature led to kidney damage. Therefore, the maximal temperature of commonly used heating pads must be tightly controlled to avoid overheating, which may cause kidney or tissue injury, may falsify the experimental data and could influence the study results.