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Skin-surface warming: Heat flux and central temperature
Hypothermia during spinal surgery in children: Murat et aL 17. McGuireJP, Giesbrecht GG: A comparison of three forced-air patient warming systems [Abstract]. AnesthAnalg 1993;76:$256. 18. Bissonnette B, Sessler DI, LaFlamme P: Intraoperative temperature monitoring sites in infants and children and the effect of inspired gas warming on esophageal temperature. AnesthAnalg 1989;69:192-6. 19. Muma BK, Treloar DJ, Wurmlinger K, Peterson E, Vitae A: Comparison of rectal, axillary, and tympanic membrane temperatures in infants and young children. Ann Emerg Med 1991;20:41-4. 20. Cork RC, Vaughan RW, Humphrey LS: Precision and accuracy of intraoperative temperature monitoring. Anesth Analg 1983;62:211-4. 21. Bissonnette B, Sessler DI: Mild hypothermia does not impair postanesthetic recovery in infants and children. Anesth Analg 1993;76:168-72. 22. Baydur A, Swank SM, Stiles CM, Sassoon CS: Respiratory mechanics in anesthetized young patients with kyphoscoliosis.Im-
mediate and delayed effects of corrective spinal surgery. Chest 1990;97:1157-64. 23. Schur MS, BrownJT,Kafer ER, Strope GL, Greene WB, Mandell J: Postoperative pulmonary function in children. Comparison of scoliosis with peripheral surgery. Am Rev Resp/r D/s 1984;130:46-51. 24. Mason DG, Higgins D, Boyd SG, Lloyd-ThomasAR: Sequential measurement of the median nerve somatosensory evoked potential du~ring isoflurane anaesthesia in children. BrJ Anaesth 1992;69:567-9. 25. Pathak KS, Ammadio M, Kalamchi A, Scoles PV, Shaffer JW, Mackay W: Effects of halothane, enflurane, and isoflurane on somatosensoryevoked potentials during nitrous oxide anesthesia. Anesthesiology1987;66:753-7. 26. Sebel PS, Ingram DA, Flynn PJ, Rutherfoord, CF, Rogers H: Evoked potentials during isoflurane anaesthesia. BrJ Anaesth 1986;58:580-5.
Skin-Surface Warming: Heat Flux and Central Temperature Daniel I. Sessleg, MD, and Azita Moayeri, BA D e p a r t m e n t o f Anesthesia, University o f California, San Francisco, San Francisco, CA
Abstract The authors determined the efficacy of four postoperative warming devices by measuring cutaneous and tympanic membrane temperatures, and heat loss/gain using 11 thermocouples and ten thermal flux transducers in five healthy, unanesthetized volunteers. Overall thermal comfort was evaluated at 5-10 rain intervals using a 10era visual analog scale. The warming devices were: 1) a pair of 250-W infrared heating lamps mounted 71 cm above the abdomen; 2) the Thermal Ceiling MTC XI UL (500 W) set on "high" and mounted 56 cm above the volunteer; 3) a 54-by-145 cm circulating-water blanket set to 40°C placed over the volunteer; and 4) the BairHugger forced air warmer with an adult-sized cover set on "low" (~-33 ° C), " m e d i u m " (~-38 ° C), and "high" (~-43 ° C). Following a 10-min control period, each device was placed over the volunteer and activated for a 30-min period. All devices were started "cold" and warmed up during the study period. The Bair Hugger set on " m e d i u m " decreased heat loss more than each radiant warming device and as much as the circulating-water blanket. All methods reached maximum efficacy within 20 rain. Set on "high," the Bair Hugger increased skin-surface temperature more ~ a n the circulating-water blanket. The Bair Hugger (all settings) and the water blanket raised skin temperature more than the radiant heaters. The circulating-water blanket was the most effective device for heating an optimally placed transducer on the chest (directly under and parallel to the radiant heat sources, and touching the water and Bair Hugger blankets). However, when the entire skin surface was considered, the Bair Hugger set on "high" transferred the most heat, enough to increase mean body temperature ~-1.5 degrees C / h in a postoperative patient without thermoregulatory responses. Central temperature decreased slightly (the expected thermoregulatory response) during skin-surface warming, the decrease being roughly in proportion to the efficacy of the warming devices. Cutaneous heat flux correlated well with the skin-surface temperature, but not with thermal comfort. There was no correlation between forehead and tympanic membrane temperatures. Reproduced with permission from Anesthesiology 1990;73:218-24.
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mediate and delayed effects of corrective spinal surgery. Chest 1990;97:1157-64. 23. Schur MS, BrownJT,Kafer ER, Strope GL, Greene WB, Mandell J: Postoperative pulmonary function in children. Comparison of scoliosis with peripheral surgery. Am Rev Resp/r D/s 1984;130:46-51. 24. Mason DG, Higgins D, Boyd SG, Lloyd-ThomasAR: Sequential measurement of the median nerve somatosensory evoked potential du~ring isoflurane anaesthesia in children. BrJ Anaesth 1992;69:567-9. 25. Pathak KS, Ammadio M, Kalamchi A, Scoles PV, Shaffer JW, Mackay W: Effects of halothane, enflurane, and isoflurane on somatosensoryevoked potentials during nitrous oxide anesthesia. Anesthesiology1987;66:753-7. 26. Sebel PS, Ingram DA, Flynn PJ, Rutherfoord, CF, Rogers H: Evoked potentials during isoflurane anaesthesia. BrJ Anaesth 1986;58:580-5.
Skin-Surface Warming: Heat Flux and Central Temperature Daniel I. Sessleg, MD, and Azita Moayeri, BA D e p a r t m e n t o f Anesthesia, University o f California, San Francisco, San Francisco, CA
Abstract The authors determined the efficacy of four postoperative warming devices by measuring cutaneous and tympanic membrane temperatures, and heat loss/gain using 11 thermocouples and ten thermal flux transducers in five healthy, unanesthetized volunteers. Overall thermal comfort was evaluated at 5-10 rain intervals using a 10era visual analog scale. The warming devices were: 1) a pair of 250-W infrared heating lamps mounted 71 cm above the abdomen; 2) the Thermal Ceiling MTC XI UL (500 W) set on "high" and mounted 56 cm above the volunteer; 3) a 54-by-145 cm circulating-water blanket set to 40°C placed over the volunteer; and 4) the BairHugger forced air warmer with an adult-sized cover set on "low" (~-33 ° C), " m e d i u m " (~-38 ° C), and "high" (~-43 ° C). Following a 10-min control period, each device was placed over the volunteer and activated for a 30-min period. All devices were started "cold" and warmed up during the study period. The Bair Hugger set on " m e d i u m " decreased heat loss more than each radiant warming device and as much as the circulating-water blanket. All methods reached maximum efficacy within 20 rain. Set on "high," the Bair Hugger increased skin-surface temperature more ~ a n the circulating-water blanket. The Bair Hugger (all settings) and the water blanket raised skin temperature more than the radiant heaters. The circulating-water blanket was the most effective device for heating an optimally placed transducer on the chest (directly under and parallel to the radiant heat sources, and touching the water and Bair Hugger blankets). However, when the entire skin surface was considered, the Bair Hugger set on "high" transferred the most heat, enough to increase mean body temperature ~-1.5 degrees C / h in a postoperative patient without thermoregulatory responses. Central temperature decreased slightly (the expected thermoregulatory response) during skin-surface warming, the decrease being roughly in proportion to the efficacy of the warming devices. Cutaneous heat flux correlated well with the skin-surface temperature, but not with thermal comfort. There was no correlation between forehead and tympanic membrane temperatures. Reproduced with permission from Anesthesiology 1990;73:218-24.
J. Clin. Anesth., vol. 6, September/October 1994
429