Comparison of distal oesophageal temperature with "deep" and tracheal temperatures.

PURPOSE: To compare distal oesophageal (reference) temperature with "deep-sternal," "deep-forehead," and tracheal temperatures, establishing the accuracy and precision of each. METHODS: We studied 20 patients undergoing general anaesthesia for gynaecological surgery. Their lungs were mechanically ventilated with a circle system, at a fresh-gas flow rate of 6 L.min-1 Respiratory gases were not warmed or humidified. Tracheal temperatures were recorded from a Trachelon tube inserted approximately 21 cm. Deep-body temperatures were measured at the sternum and forehead using a Coretemp thermometer. The principle of the method is to null thermal flux through a cutaneous disk, thus obliterating thermal gradients between the sides of the disk, skin surface, and subcutaneous tissues. Distal oesophageal temperatures were measured from thermocouples incorporated into oesophageal stethoscopes. Tracheal and deep-tissue temperatures were compared with oesophageal temperature using regression and Bland and Altman analyses. RESULTS: Tracheal, sternal, and forehead temperatures correlated similarly with distal oesophageal temperature, correlation coefficients (r2) being 0.7 in each case. The offset (oesophageal temperature minus study site) was considerably larger for tracheal temperature (0.7 degree C) than for the other sites (0.2 degree C). However, the precision was only 0.3 degree C at each site. CONCLUSION: Our data suggest that tracheal temperatures may not be an adequate substitute for conventional core-temperature monitoring sites. In contrast, the accuracy and precision of deep-tissue temperature monitoring at the sternum and forehead was sufficient for clinical use.

I.m. midazolam as premedication produces a concentration-dependent decrease in core temperature in male volunteers.

We tested the hypothesis that premedication with i.m. midazolam decreases core temperature dose-dependently. We studied six male volunteers, in random order, on 3 days: (1) no midazolam administration (control day), (2) midazolam 0.025 mg kg-1 i.m., (3) midazolam 0.075 mg kg-1 i.m. On the first day, subjects were maintained alert during a 30-min control period. On the second and third days, midazolam 0.025 or 0.075 mg kg-1 was administered i.m. Core temperatures were measured at the right tympanic membrane. Four adhesive skin surface probes were fixed on the chest, upper right arm, lateral calf and thigh. Finger tip perfusion was evaluated using forearm minus fingertip and calf minus toe, skin surface temperature gradients. Thirty minutes after midazolam i.m., the level of sedation in the volunteers was assessed. Peripheral venous blood was obtained immediately after the assessment of the level of sedation. Tympanic membrane temperatures after administration of midazolam 0.075 mg kg-1 i.m. were significantly lower than those on the control and midazolam 0.025 mg kg-1 i.m. days at 20 and 30 min. The decreases in tympanic membrane temperatures at 30 min after midazolam i.m. became larger as the volunteers were more deeply sedated. i.m. midazolam produced a concentration-dependent decrease in tympanic membrane temperature at 30 min after midazolam 0.025 and 0.075 mg kg-1 i.m. We conclude that midazolam impaired tonic thermoregulatory vasoconstriction, allowing core-to-peripheral heat redistribution in a dose-dependent manner after i.m. administration.

A comparison of four infrared tympanic thermometers with tympanic membrane temperatures measured by thermocouples.

PURPOSE: To compare measurements made with four infrared tympanic thermometers (Genius, Thermopit, Quickthermo, and Thermoscan) with those recorded from thermocouples positioned in the contralateral ear. METHODS: Four tympanic thermometers were evaluated in 50 healthy volunteers (12 female and 38 male). Temperatures were measured, in random order, at the right tympanic membrane four times and the highest temperature was considered to be the true value measured by each thermometer. The control temperature was measured at the left tympanic membrane using Mon-a-Therm thermocouples. RESULTS: The tympanic membrane temperature measured by Genius correlated best with the Mon-a-therm measurement (TM) (r = 0.74). The tympanic membrane temperatures measured by Thermopit, Quickthermo, and Thermoscan correlated moderately with TM (r = 0.56, 0.63, and 0.58, respectively). Mean differences between TM and each temperature (TG, TTP, TQ, and TTS) were -0.3, 0.73, 0.42, and -0.3 degrees C, respectively. Likewise standard deviations were 0.33, 0.37, 0.35, and 0.35. CONCLUSION: We conclude that all but the Thermopit (TTP) are similarly useful for the management of patients during anaesthesia.

Isoflurane and sevoflurane produce a dose-dependent reduction in the shivering threshold in rabbits.

All general anesthetics markedly impair thermoregulatory responses; nonetheless, sufficient hyperthermia or hypothermia will trigger most protective reflexes. Shivering, however, remains an exception among thermo-regulatory responses: it is common during postanesthetic recovery, but is rare at typical anesthetic concentrations. This observation suggests that general anesthesia impairs shivering far more than other thermoregulatory defenses. Accordingly, we tested the hypothesis that low concentrations of isoflurane and sevoflurane would virtually obliterate shivering. Japanese white rabbits were anesthetized with isoflurane or sevoflurane at end-tidal concentrations of 0.2, 0.3, and 0.4 minimum alveolar anesthetic concentration (MAC) (n = 6 in each group); the normal core temperature for these rabbits is approximately 39 degrees C. Core temperatures were subsequently reduced by a water-perfused thermode positioned in the colon. The core temperature triggering shivering identified the threshold for this response. Five of the six rabbits given 0.2 MAC isoflurane shivered at a mean core temperature of 36.3 +/- 0.3 degrees C (mean +/- SD), and one rabbit failed to shiver at a minimum core temperature of 35.0 degrees C. Four of the six rabbits given 0.3 MAC isoflurane shivered at a mean core temperature of 36.2 +/- 0.6 degrees C, and two of these rabbits failed to shiver at a minimum core temperature of 35.0 degrees C. However, no rabbit given 0.4 MAC isoflurane shivered, even at minimum core temperatures of 35.0 degrees C. All of the rabbits given 0.2 MAC sevoflurane shivered at a mean core temperature of 36.6 +/- 0.7 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

A new infrared tympanic thermometer in surgery and anesthesia.

We have evaluated a new infrared tympanic thermometer, IT-10, as an intraoperative temperature monitor in patients with or without open abdominal surgery. It determines temperature by measuring infrared radiation given off by a warm object. Temperatures measured with this device were closely correlated with those measured with rectal and bladder thermometries. We conclude that this new tympanic thermometer is safe, convenient, accurate, and easily usable in the clinical situation.

[Epidural anesthesia with high dose fentanyl for thoracic surgeries].

Twenty-two elective thoracic surgeries were performed under epidural high dose fentanyl anesthesia. These included 11 mastectomies, 3 lung lobectomies, and 8 operations for esophageal carcinoma. Through an epidural catheter, 10 micrograms.kg-1 fentanyl with [E (+)] or without [E (-)] epinephrine (1: 100,000) was given. N2O (66%) and enflurane (0.2-0.8%) were also administered, and muscle relaxants were given as needed. The onset and duration of the action were approximately 20 minutes and 3 hours, respectively. Anesthesia was maintained with enflurane (up to 0.4%) in 17 patients (77.3%). There were no differences between the E (+) group and the E (-) group. Systolic pressure, diastolic pressure and heart rate during operations were about 30% lower than those observed before the operations. Patients recovered from anesthesia rapidly. Naloxone was administered intravenously in 6 patients after mastectomies or lung lobectomies (42.9%), whose respiratory rate was below 10.min-1. The patients with short operating time (shorter than 2 hours) needed more naloxone. Troubles did not occur either in the recovery room or in the ward with both naloxone and non-naloxone groups.

[The effect of prostaglandin E1 (PGE1) on body temperature and on postoperative shivering under high dose epidural fentanyl].

Ninety-nine elective abdominal surgeries were performed under high dose epidural fentanyl anesthesia. PGE1 (0.02 microgram.kg-1.min-1 = 0.02 gamma) was administered to 34 patients (0.02 gamma group), and PGE1 (0.05 gamma) was administered to 16 patients (0.05 gamma group). PGE1 was not administered to 49 patients (control group). The effect of PGE1 on body temperature and on postoperative shivering was compared within three groups. In the 0.02 gamma group, the temperature of the fingertip was significantly higher and the rectum-fingertip temperature gradient was significantly lower than in the other groups. The forearm-fingertip temperature gradient was lower in the 0.02 gamma and 0.05 gamma groups than in the control group. The incidence of postanesthetic shivering was significantly lower in the 0.05 gamma group than in the other groups. These results suggest that; 1) PGE1 (0.02 gamma and 0.05 gamma groups) affects the peripheral blood flow and peripheral temperature, and 2) PGE1 (0.05 gamma group) significantly affects the incidence of postanesthetic shivering.