The Accuracy and Precision of Body Temperature Monitoring Methods During Regional and General Anesthesia

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Abstract
We tested the hypotheses that accuracy and precision of available temperature monitoring methods are differ- ent between spinal anesthesia (SA) and general anes- thesia (GA), and that patients receiving SA are at equal risk for hypothermia as those receiving GA. Patients scheduled for radical retropubic prostatectomy were enrolled. Either GA (n 5 16) or SA (n 5 16) was given according to patient and clinician preference. Temper- atures were monitored with thermocouple probes at the tympanic membrane, axilla, rectum, and forehead skin surface. Tympanic temperatures were also mea- sured with an infrared device, and forehead skin tem- peratures were monitored with two brands of liquid crystal thermometer strips. Accuracy and precision of these monitoring methods were determined by using tympanic membrane temperature, measured by ther- mocouple, as the reference core temperature (Tc). At the end of surgery, Tc was similar between SA (35.0 6 0.1°C) and GA (35.2 6 0.1°C) (P 5 0.44). Accuracy and precision of each temperature monitoring method were similar between SA and GA. Rectal temperature moni- toring offered the greatest combination of accuracy and precision. All other methods underestimated Tc. These findings suggest that patients receiving SA or GA are at equal and significant risk for hypothermia, and should have their temperatures carefully monitored, recogniz- ing that most monitoring methods underestimate Tc. Implications: Body temperature should be monitored during spinal anesthesia because patients are at signif- icant risk for hypothermia. Rectal temperature is a valid method of measuring core temperature, whereas other methods tend to underestimate true core temperature. (Anesth Analg 2000;90:938 -45)