Estimation of mean body temperature from mean skin and core temperature.
BACKGROUND
Mean body temperature (MBT) is the mass-weighted average temperature of body tissues. Core temperature is easy to measure, but direct measurement of peripheral tissue temperature is painful and risky and requires complex calculations. Alternatively MBT can be estimated from core and mean skin temperatures with a formula proposed by Burton in 1935: MBT = 0.64 x TCore + 0.36 x TSkin. This formula remains widely used, but has not been validated in the perioperative period and seems unlikely to remain accurate in dynamic perioperative conditions such as cardiopulmonary bypass. Therefore, the authors tested the hypothesis that MBT, as estimated with Burton's formula, poorly estimates measured MBT at a temperature range between 18 degrees and 36.5 degrees C.


METHODS
The authors reevaluated four of their previously published studies in which core and mass-weighted mean peripheral tissue temperatures were measured in patients undergoing substantial thermal perturbations. Peripheral compartment temperatures were estimated using fourth-order regression and integration over volume from 18 intramuscular needle thermocouples, 9 skin temperatures, and "deep" hand and foot temperature. MBT was determined from mass-weighted average of core and peripheral tissue temperatures and estimated from core temperature and mean skin temperature (15 area-weighted sites) using Burton's formula.


RESULTS
Nine hundred thirteen data pairs from 44 study subjects were included in the analysis. Measured MBT ranged from 18 degrees to 36.5 degrees C. There was a remarkably good relation between measured and estimated MBT: MBTmeasured = 0.94 x MBTestimated + 2.15, r = 0.98. Differences between the estimated and measured values averaged -0.09 degrees +/- 0.42 degrees C.


CONCLUSIONS
The authors concluded that estimation of MBT from mean skin and core temperatures is generally accurate and precise.
Lenhardt
Rainer
R
Outcomes Research Institute, Department of Anesthesiology & Perioperative Medicine, Neurosciences Intensive Care Unit, University of Louisville, Louisville, Kentucky 40202, USA. rainer.lenhardt@louisville.edu
Sessler
Daniel I
DI
D000368:Aged; D000465:Algorithms; D001132:Arm / Q000502:physiology; D001831:Body Temperature / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology; D006257:Head / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D009929:Organ Size / Q000502:physiology; D012881:Skin Temperature / Q000502:physiology*; D013909:Thorax / Q000033:anatomy & histology / Q000502:physiology