43 results on '"Ozaki, M"'
Search Results
2. Forced-air Warming After IM Midazolam Premedication Prevents Core Hypothermia in Male Volunteers
- Author
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Matsukawa, T, primary, Hanagata, K, additional, Ozaki, M, additional, Sessler, D I, additional, Imamura, M, additional, and Kumazawa, T, additional
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- 1998
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- View/download PDF
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3. Preoperative Transdermal Nitroglycerin Decreases Redistribution Hypothermia after Induction of Anesthesia
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Morioka, N, primary, Ozaki, M, additional, Sessler, D I, additional, Matsukawa, T, additional, Yasunaka, H, additional, Atarashi, K, additional, and Suzuki, H, additional
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- 1998
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4. NON-INVASIVE BLOOD PRESSURE MONITORING WITH THE VASOTRAC[trade mark sign]-RESULTS OF A MULTICENTER CLINICAL TRIAL
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Belani, K., primary, Ozaki, M., additional, Hynson, J., additional, Hartmann, T., additional, Reyford, H., additional, Camus, Y., additional, Zimpfer, M., additional, Krivosic-Horber, R., additional, Suzuki, H., additional, Leinhart, A., additional, Poliac, M., additional, and Miller, R., additional more...
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- 1998
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5. Atropine Prevents Midazolam-induced Core Hypothermia in Elderly Patients
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Matsukawa, T., primary, Imamura, M., additional, Ozaki, M., additional, Sessler, D I, additional, Hanagata, K, additional, and Kumazawa, T., additional
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- 1998
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- View/download PDF
6. Alfentanil Slightly Reduces the Febrile Response to Interleukin-2 Administration
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Lenhardt, R., primary, Negishi, C., additional, Kim, J., additional, Sessler, D. I., additional, and Ozaki, M., additional
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- 1998
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7. Measurement of Non-Invasive Oscillometric Blood Pressure in the Elderly is Faster and More Comfortable During Cuff Inflation Than Deflation
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Morioka, N, primary, Ozaki, M, additional, Sessler, D I, additional, Matsukawa, T, additional, Ozaki, K, additional, Atarashi, K, additional, and Suzuki, H, additional
- Published
- 1998
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8. A492 The Accuracy and Precision of Four Infrared Tympanic Membrane Thermometers During Cardiopulmonary Bypass
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Matsukawa, T., primary, Imamura, M., additional, Ozaki, M., additional, Sessler, D.I., additional, and Kumazawa, T., additional
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- 1997
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9. A488 The Accuracy and Precision of Tracheal, Deep Forehead, and Deep Sternal Temperatures During High and Low Flow Anesthesia
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Matsukawa, T., primary, Ozaki, M., additional, Sessler, D.I., additional, and Kumazawa, T., additional
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- 1997
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10. A428 Clinical Evaluation of a New Point-of-Care Blood Gas Analyzer, The "IRMA System"
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Ozaki, M., primary, Morioka, N., additional, Matsukawa, T., additional, Atarashi, K., additional, Sessler, D.I., additional, and Suzuki, H., additional
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- 1997
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11. A502 Ketamine Causes a Paradoxical Increase in the Bispectral Index
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Morioka, N., primary, Ozaki, M., additional, Matsukawa, T., additional, Sessler, D.I., additional, Atarashi, K., additional, and Suzuki, H., additional
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- 1997
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12. A582 WALL TENSION DETERMINES HYPOXIC PULMONARY VASOCONSTRICTION IN ISOLATED RAT ARTERIES
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Ozaki, M., primary, Amaki, Y., additional, Marshall, C., additional, and Marshall, B.E., additional
- Published
- 1997
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13. A431 Measurement of Non-Invasive Oscillometric Blood Pressure During Cuff Inflation, Rather Than Deflation
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Morioka, N., primary, Ozaki, M., additional, Ozaki, K., additional, Sessler, D.I., additional, Matsukawa, T., additional, and Suzuki, H., additional
- Published
- 1997
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14. PROPOFOL CAUSES A DOSE-DEPENDENT DECREASE IN THE THERMOREGULATORY THRESHOLD FOR VASOCONSTRICTION BUT HAS LITTLE EFFECT ON SWEATING
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Leslie, K., primary, Sessler, D. I., additional, Bjorksten, A. R., additional, Ozaki, M., additional, Matsukawa, T., additional, Schroeder, M., additional, and Lin, S., additional
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- 1994
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15. Heat Flow and Distribution during Induction of General Anesthesia
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Matsukawa, T., primary, Sessler, D. I., additional, Sessler, A. M., additional, Schroeder, M., additional, Ozaki, M., additional, Kurz, A., additional, and Cheng, C., additional
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- 1994
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16. CUTANEOUS CONTRIBUTION TO CONTROL OF THERMOREGULATORY VASOCONSTRICTION AND SHIVERING
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Ozaki, M., primary, Sessler, D. I., additional, Cheng, C., additional, and Matsukawa, T., additional
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- 1994
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17. NITROUS OXIDE IMPAIRS THERMOREGULATION LESS THAN SEVOFLURANE
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Ozaki, M., primary, Sessler, D. I., additional, Suzuki, H., additional, Ozaki, K., additional, Tsunoda, C., additional, and Atarashi, K., additional
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- 1994
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18. Direction-Dependent Hysteresis For Thermoregulatory Vasoconstriction During Isoflurane Anesthesia
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Ozaki, M, primary, Sessler, D I, additional, Leslie, K, additional, McGuire, J, additional, Blanchard, D, additional, Schroeder, M, additional, and Moayeri, A, additional
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- 1992
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19. Learning curves for bag-and-mask ventilation and orotracheal intubation: an application of the cumulative sum method.
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Komatsu R, Kasuya Y, Yogo H, Sessler DI, Mascha E, Yang D, and Ozaki M
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- 2010
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20. SERUM INORGANIC FLUORIDE AFTER EXTENDED EXPOSURE TO SEVOFLURANE IN PATIENTS
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Toriumi, K., primary, Ozaki, M., additional, Yasuda, N., additional, Tanifuji, Y., additional, and Amaki, Y., additional
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- 1991
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21. Accuracy of postoperative end-tidal Pco2 measurements with mainstream and sidestream capnography in non-obese patients and in obese patients with and without obstructive sleep apnea.
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Kasuya Y, Akça O, Sessler DI, Ozaki M, and Komatsu R
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- 2009
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22. Opioids inhibit febrile responses in humans, whereas epidural analgesia does not: an explanation for hyperthermia during epidural analgesia.
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Negishi, C, Lenhardt, R, Ozaki, M, Ettinger, K, Bastanmehr, H, Bjorksten, A R, and Sessler, D I
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- 2001
23. Prediction of movement during propofol/nitrous oxide anesthesia. Performance of concentration, electroencephalographic, pupillary, and hemodynamic indicators.
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Leslie, Kate, Sessler, Daniel I., Smith, Warren D., Larson, Merlin D., Ozaki, Makoto, Blanchard, Don, Crankshaw, David P., Leslie, K, Sessler, D I, Smith, W D, Larson, M D, Ozaki, M, Blanchard, D, and Crankshaw, D P more...
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- 1996
24. Acquired carnitine deficiency: a clinical model for propofol infusion syndrome?
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Uezono S, Hotta Y, Takakuwa Y, Ozaki M, Uezono, Shoichi, Hotta, Yukako, Takakuwa, Yuichi, and Ozaki, Makoto
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- 2005
25. A Floating Object in the Left Atrium.
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Seino Y, Maruyama E, Nomura M, and Ozaki M
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- Adult, Female, Foreign Bodies surgery, Heart Atria diagnostic imaging, Heart Atria surgery, Humans, Echocardiography, Three-Dimensional, Echocardiography, Transesophageal, Foreign Bodies diagnostic imaging, Mitral Valve diagnostic imaging, Mitral Valve surgery, Surgical Sponges
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- 2018
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26. In reply.
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Higuchi H, Takagi S, and Ozaki M
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- Female, Humans, Pregnancy, Aorta, Abdominal anatomy & histology, Vena Cava, Inferior anatomy & histology
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- 2015
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27. Effect of lateral tilt angle on the volume of the abdominal aorta and inferior vena cava in pregnant and nonpregnant women determined by magnetic resonance imaging.
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Higuchi H, Takagi S, Zhang K, Furui I, and Ozaki M
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- Adult, Female, Humans, Magnetic Resonance Imaging, Patient Positioning, Pregnancy, Supine Position, Uterus anatomy & histology, Young Adult, Aorta, Abdominal anatomy & histology, Vena Cava, Inferior anatomy & histology
- Abstract
Background: Left-lateral tilt position is used to reduce assumed aortocaval compression by the pregnant uterus., Methods: Magnetic resonance images of 10 singleton parturients at full term and 10 healthy nonpregnant women were obtained for measurement of the abdominal aorta and inferior vena cava volume between the L1-L2 disk and L3-L4 disk levels in both the supine and left-lateral tilt positions (15°, 30°, and 45°) maintained by insertion of a 1.5-m-long polyethylene foam placed under the right side of the parturient's body., Results: Aortic volume did not differ significantly between parturients and nonpregnant women in the supine position (12.7 ± 2.0 vs.12.6 ± 2.1 ml, mean ± SD; mean difference, -0.1; 95% confidence interval [CI], -2.0 to 1.9; P = 0.95). Inferior vena cava volume in the supine position was significantly lower in parturients than in nonpregnant women (3.2 ± 3.4 vs.17.5 ± 7.8 ml; mean difference, 14.3; 95% CI, 8.3-20.2; P < 0.001). Aortic volume in parturients did not differ among left-lateral tilt positions. Inferior vena cava volume in the parturients was not increased at 15° (3.0 ± 2.1 ml; mean difference, -0.2; 95% CI, -1.5 to 1.2; P > 0.99), but was significantly increased at 30° (11.5 ± 8.6 ml; mean difference, 8.3; 95% CI, 2.3-14.2; P = 0.009) and 45° (10.9 ± 6.8 ml; mean difference, 7.7; 95% CI, 2.2-13.1; P = 0.015)., Conclusions: In parturients, the aorta was not compressed, and a 15° left-lateral tilt position did not effectively reduce inferior vena cava compression. more...
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- 2015
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28. Distribution of epidural saline upon injection and the epidural volume effect in pregnant women.
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Higuchi H, Takagi S, Onuki E, Fujita N, and Ozaki M
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- Adult, Cerebrospinal Fluid, Epidural Space anatomy & histology, Epidural Space drug effects, Female, Humans, Injections, Epidural, Magnetic Resonance Imaging, Tissue Distribution, Analgesia, Epidural, Pregnancy physiology, Sodium Chloride administration & dosage, Sodium Chloride pharmacokinetics
- Abstract
Background: How injected epidural solution is distributed and affects the epidural volume in pregnant women are unclear., Methods: Lumbar epidural catheters were placed using the loss-of-resistance technique with saline in eight full-term (39 weeks' gestation) parturients for labor and eight volunteer nonpregnant women. Lumbosacral cerebrospinal fluid volume was measured on thoracic and lumbosacral axial magnetic resonance images. Another image series was obtained after injecting 10 ml saline into the epidural space through the catheter to compare the saline distribution (dural sac coating and exit from foramina) and cerebrospinal fluid volume before and after epidural injection. Dural sac coating was based on observation of epidural saline in the anterior epidural space after injection in axial magnetic resonance images at the pedicle levels from T12 to L5. Saline leakage from the foramina was determined by the same method at six disc levels from T11-T12 to L4-L5., Results: Significantly fewer images of pregnant women than nonpregnant women showed saline surrounding the dural sac (0 [0-0] vs. 3 [1-4], median [interquartile range]; P < 0.01) and saline leakage from the foramina (0 [0-1] vs. 6 [4-6]; P < 0.01). The mean reduction in cerebrospinal fluid volume was significantly greater in pregnant (8.4 ± 1.4 ml; mean ± SD) than in nonpregnant women (4.6 ± 1.1 ml; P < 0.001)., Conclusion: Limited dural sac coating and decreased leakage from the foramina of saline injected into the epidural space may account for the facilitation of longitudinal spread of epidural analgesia in pregnant women. The epidural volume effect is greater in pregnant than in nonpregnant women. more...
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- 2011
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29. Dexmedetomidine reduces long-term potentiation in mouse hippocampus.
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Takamatsu I, Iwase A, Ozaki M, Kazama T, Wada K, and Sekiguchi M
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- Animals, Hippocampus physiology, Hypnotics and Sedatives pharmacology, Imidazoline Receptors physiology, Long-Term Potentiation physiology, Male, Mice, Mice, Inbred C57BL, Neuronal Plasticity drug effects, Neuronal Plasticity physiology, Dexmedetomidine pharmacology, Hippocampus drug effects, Long-Term Potentiation drug effects
- Abstract
Background: Dexmedetomidine (Precedex; Abbott Laboratories, Abbott Park, IL) is a selective alpha2-adrenergic agonist that also has affinity for imidazoline receptors. In clinical studies, dexmedetomidine has sedative effects and impairs memory, but the action of dexmedetomidine on synaptic plasticity in the brain has yet to be established. In the present study, the authors investigated the effects of dexmedetomidine on two forms of synaptic plasticity-long-term potentiation (LTP) and paired-pulse facilitation-in the CA1 region of mouse hippocampal slices., Methods: The authors recorded Schaffer collateral-evoked field excitatory postsynaptic potentials from mouse hippocampal slices in CA1 stratum radiatum. The slope of the rising phase of the field excitatory postsynaptic potential was used to estimate the strength of synaptic transmission., Results: Application of dexmedetomidine for 20 min before "theta burst" stimulation dose-dependently attenuated LTP, and half-inhibitory concentration of dexmedetomidine was 28.6 +/- 5.7 nm. The inhibitory effect of dexmedetomidine on LTP was not abolished by an alpha2-adrenoceptor antagonist (yohimbine), an imidazoline type 1 receptor and alpha2-adrenoceptor antagonist (efaroxan), an alpha1-adrenoceptor antagonist (prazosin), or a gamma-aminobutyric acid type A receptor antagonist (picrotoxin). However, an imidazoline type 2 receptor and alpha2-adrenoceptor antagonist (idazoxan) completely blocked the dexmedetomidine-induced attenuation. Furthermore, 2-benzofuranyl-2-imidaloline, a selective imidazoline type 2 receptor ligand, reduced LTP. 2-(4,5-dihydroimidaz-2-yl)-quinoline, another imidazoline type 2 receptor ligand, abolished the 2-benzofuranyl-2-imidaloline-induced attenuation, but the inhibitory effect of dexmedetomidine on LTP was not abolished by 2-(4,5-dihydroimidaz-2-yl)-quinoline. Dexmedetomidine did not affect paired-pulse facilitation., Conclusion: Dexmedetomidine impairs LTP in area CA1 of the mouse hippocampus via imidazoline type 2 receptors and alpha2-adrenoceptors. more...
- Published
- 2008
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30. A new noninvasive method to measure blood pressure: results of a multicenter trial.
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Belani K, Ozaki M, Hynson J, Hartmann T, Reyford H, Martino JM, Poliac M, and Miller R
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- Adult, Aged, Blood Pressure, Humans, Middle Aged, Pulse, Radial Artery physiology, Blood Pressure Determination
- Abstract
Background: Blood pressure (BP) monitoring with arterial waveform display requires an arterial cannula. We evaluated a new noninvasive device, Vasotrac (Medwave, Arden Hills, MN) that provides BP measurements approximately every 12-15 beats and displays pulse rate and a calibrated arterial waveform for each BP measurement., Methods: Surgical and critically ill patients (n = 80) served as subjects for the study. BPs, pulse waveforms, and pulse rates measured via a radial artery catheter were compared with those obtained by the Vasotrac from the opposite radial artery. Data were analyzed to determine agreement between the two systems of measurement., Results: Blood pressure measured noninvasively by the Vasotrac demonstrated excellent correlation (P<0.01) with BP measured via a radial arterial catheter (systolic r2 = 0.93; diastolic r2 = 0.89; mean r2 = 0.95). Differences in BP measured by the Vasotrac versus the radial arterial catheter were small. The mean+/-SD bias and precision were as follows: systolic BP 0.02+/-5.4 mm Hg and 3.9+/-3.7 mm Hg; diastolic BP -0.39+/-3.9 mm Hg and 2.7+/-2.8 mm Hg; mean BP -0.21+/-3.0 mm Hg and 2.1+/-2.2 mm Hg compared with radial artery measurements. The Vasotrac pulse rates were almost identical to those measured directly (r2 = 0.95). The Vasotrac BP waveform resembled those directly obtained radial artery pulsatile waveforms., Conclusions: In surgical and critically ill patients, the Vasotrac measured BP, pulse rate, and displayed radial artery waveform, which was similar to direct radial arterial measurements. It should be a suitable device to measure BP frequently in a noninvasive fashion. more...
- Published
- 1999
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31. Thermoregulatory thresholds for vasoconstriction in patients anesthetized with various 1-minimum alveolar concentration combinations of xenon, nitrous oxide, and isoflurane.
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Goto T, Matsukawa T, Sessler DI, Uezono S, Ishiguro Y, Ozaki M, and Morita S
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- Adult, Aged, Female, Humans, Isoflurane administration & dosage, Male, Middle Aged, Nitrous Oxide administration & dosage, Sympathetic Nervous System drug effects, Xenon administration & dosage, Anesthetics, Inhalation pharmacology, Body Temperature Regulation drug effects, Isoflurane pharmacology, Nitrous Oxide pharmacology, Vasoconstriction drug effects, Xenon pharmacology
- Abstract
Background: Nitrous oxide limits intraoperative hypothermia because the vasoconstriction threshold with nitrous oxide is higher than with equi-minimum alveolar concentrations of sevoflurane or isoflurane, presumably because of its stimulating actions on the sympathetic nervous system. Xenon, in contrast, does not cause sympathetic activation. Therefore, the authors tested the hypothesis that the vasoconstriction threshold during xenon-isoflurane anesthesia is less than during nitrous oxide-isoflurane anesthesia or isoflurane alone., Methods: Fifteen patients each were randomly assigned to one of three 1-minimum alveolar concentration anesthetic regimens: (1) xenon, 43% (0.6 minimum alveolar concentration) and isoflurane, 0.5% (0.4 minimum alveolar concentration); (2) nitrous oxide, 63% (0.6 minimum alveolar concentration) and isoflurane 0.5%; or (3) isoflurane, 1.2%. Ambient temperature was maintained near 23 degrees C and the patients were not actively warmed. Thermoregulatory vasoconstriction was evaluated using forearm-minus-fingertip skin temperature gradients. A gradient exceeding 0 degrees C indicated significant vasoconstriction. The core-temperature threshold that would have been observed if skin had been maintained at 33 degrees C was calculated from mean skin and distal esophageal temperatures at the time of vasoconstriction., Results: The patients' demographic variables, preinduction core temperatures, ambient operating room temperatures, and fluid balance were comparable among the three groups. Heart rates were significantly less during xenon anesthesia than with nitrous oxide. The calculated vasoconstriction threshold was lowest with xenon (34.6+/-0.8 degrees C, mean +/- SD), intermediate with isoflurane alone (35.1+/-0.6 degrees C), and highest with nitrous oxide (35.7+/-0.6 degrees C). Each of the thresholds differed significantly., Conclusions: Xenon inhibits thermoregulatory control more than isoflurane, whereas nitrous oxide is the least effective in this respect. more...
- Published
- 1999
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32. The effect of pyrogen administration on sweating and vasoconstriction thresholds during desflurane anesthesia.
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Lenhardt R, Negishi C, Sessler DI, Ozaki M, Ettinger K, Bastanmehr H, and Lobo E
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- Adult, Anesthesia, Inhalation, Body Temperature Regulation drug effects, Desflurane, Humans, Interleukin-2 blood, Isoflurane pharmacology, Male, Anesthetics, Inhalation pharmacology, Fever physiopathology, Interleukin-2 pharmacology, Isoflurane analogs & derivatives, Sweating drug effects, Vasoconstriction drug effects
- Abstract
Background: General anesthetics increase the sweating-to-vasoconstriction interthreshold range (temperatures not triggering thermoregulatory defenses), whereas fever is believed to only increase the setpoint (target core temperature). However, no data characterize thresholds (temperatures triggering thermoregulatory defenses) during combined anesthesia and fever. Most likely, the combination produces an expanded interthreshold range around an elevated setpoint. The authors therefore tested the hypothesis that thermoregulatory response thresholds during the combination of fever and anesthesia are simply the linear combination of the thresholds resulting from each intervention alone., Methods: The authors studied eight healthy male volunteers. Fever was induced on the appropriate days by intravenous injection of 30 IU/g human recombinant interleukin 2 (IL-2), followed 2 h later by an additional 70 IU/g. General anesthesia consisted of desflurane 0.6 minimum alveolar concentration (MAC). The volunteers were randomly assigned to the following groups: (1) control (no desflurane, no IL-2); (2) IL-2 alone; (3) desflurane alone; and (4) desflurane plus IL-2. During the fever plateau, volunteers were warmed until sweating was observed and then cooled to vasoconstriction. Sweating was evaluated from a ventilated capsule and vasoconstriction was quantified by volume plethysmography. The tympanic membrane temperatures triggering significant sweating and vasoconstriction identified the respective response thresholds. Data are presented as the mean +/- SD; P < 0.05 was considered significant., Results: The interthreshold range was near 0.40 degrees C on both the control day and during IL-2 administration alone. On the IL-2 alone day, however, the interthreshold range was shifted to higher temperatures. The interthreshold range increased significantly during desflurane anesthesia to 1.9+/-0.6 degrees C. The interthreshold range during the combination of desflurane and IL-2 was 1.2+/-0.6 degrees C, which was significantly greater than on the control and IL-2 alone days. However, it was also significantly less than during desflurane alone., Conclusion: The combination of desflurane and IL-2 caused less thermoregulatory inhibition than would be expected based on the effects of either treatment alone. Fever-induced activation of the sympathetic nervous system may contribute by compensating for a fraction of the anesthetic-induced thermoregulatory impairment. more...
- Published
- 1999
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33. Paralysis only slightly reduces the febrile response to interleukin-2 during isoflurane anesthesia.
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Lenhardt R, Negishi C, Sessler DI, Ozaki M, Tayefeh F, and Kurz A
- Subjects
- Body Temperature Regulation, Humans, Shivering, Vasoconstriction, Anesthesia, Anesthetics, Inhalation pharmacology, Fever prevention & control, Interleukin-2 pharmacology, Isoflurane pharmacology, Neuromuscular Nondepolarizing Agents pharmacology, Vecuronium Bromide pharmacology
- Abstract
Background: Fever sometimes occurs during anesthesia. However, it is rare considering how often pyrogenic causes are likely to be present and how common fever is after surgery. This low incidence results in part from dose-dependent inhibition of fever by volatile anesthetics. Paralysis, however, may contribute by preventing shivering and the associated increase in metabolic heat production. Therefore the authors tested the hypothesis that paralysis during anesthesia decreases the febrile response to pyrogen administration., Methods: Seven volunteers each participated on two study days. They were given 30 IU/g intravenous interleukin-2, followed 90 min later by an additional 70 IU/g dose. Anesthesia was induced 30 min after the second dose and maintained for 6 h with 0.6 minimum alveolar concentration isoflurane. The volunteers were randomly assigned to (1) paralysis with vecuronium or (2) no muscle relaxants. Body heat content and distribution were determined from measured tissue and skin temperatures. Data are presented as mean +/- SD; P < 0.05 was considered significant., Results: There was no clinically important difference in peak core (tympanic membrane) temperatures on the unparalyzed (37.6+/-0.9 degrees C) and paralyzed (37.2+/-0.6 degrees C) days. Core heat content increased 1.2+/-0.7 kcal/kg over the last 5 h of anesthesia on the unparalyzed day, but only by 0.9+/-0.4 kcal/kg when the volunteers were paralyzed. Peripheral tissue heat content increased 0.1+/-1.1 kcal/kg on the unparalyzed day but decreased 1.1+/-0.7 kcal/kg when the volunteers were paralyzed. Consequently, body heat content increased 1.3+/-1.3 kcal/kg on the unparalyzed day but decreased significantly by 0.2+/-0.8 kcal/kg when the volunteers were paralyzed., Conclusions: Paralysis prevented shivering from increasing the metabolic rate. Consequently, body heat content decreased during paralysis, whereas otherwise it increased. Thermoregulatory vasoconstriction was nonetheless able to maintain similar peak and integrated core temperatures on each study day. Administration of muscle relaxants thus is not the primary explanation for the relative paucity of intraoperative fever. more...
- Published
- 1998
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34. Heat flow and distribution during epidural anesthesia.
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Matsukawa T, Sessler DI, Christensen R, Ozaki M, and Schroeder M
- Subjects
- Adjuvants, Anesthesia therapeutic use, Humans, Male, Meperidine therapeutic use, Shivering, Skin Temperature, Anesthesia, Epidural, Anesthetics, Local, Body Temperature Regulation physiology, Hypothermia etiology, Lidocaine
- Abstract
Background: Core hypothermia after induction of epidural anesthesia results from both an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors thus evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution., Methods: Twelve minimally clothed male volunteers were evaluated in a approximately 22 degrees C environment for 2.5 control hours before induction of epidural anesthesia and for 3 subsequent hours. Epidural anesthesia produced a bilateral sympathetic block in only six volunteers, and only their results are reported. Shivering, when observed, was treated with intravenous meperidine. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in esophageal or tympanic membrane (core) temperatures, leaving the core hypothermia specifically resulting from redistribution., Results: Arm heat content decreased approximately 5 kcal/h after induction of anesthesia, but leg heat content increased markedly. Most of the increase in leg heat content was in the lower legs and feet. Core temperature increased slightly during the control period but decreased 0.8 +/- 0.3 degrees C in the 1st hour of anesthesia. Redistribution, contributing 89% to this initial decrease, required a net transfer of 20 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 0.4 +/- 0.3 degrees C, with redistribution contributing 62%. Thus, only 7 kcal were redistributed during the 2nd and 3rd hours of anesthesia. Redistribution therefore contributed 80% to the entire 1.2 +/- 0.3 degrees C decrease in core temperature during the 3 h of anesthesia., Conclusions: Core hypothermia during the 1st hour after induction of epidural anesthesia resulted largely from redistribution of body heat from the core thermal compartment to the distal legs. Even after 3 h of anesthesia, redistribution remained the major cause of core hypothermia. Despite the greater fractional contribution of redistribution during epidural anesthesia, core temperature decreased only half as much as during general anesthesia because metabolic rate was maintained and the arms remained vasoconstricted. more...
- Published
- 1995
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35. Increasing mean skin temperature linearly reduces the core-temperature thresholds for vasoconstriction and shivering in humans.
- Author
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Cheng C, Matsukawa T, Sessler DI, Ozaki M, Kurz A, Merrifield B, Lin H, and Olofsson P
- Subjects
- Adult, Body Temperature Regulation, Female, Humans, Male, Shivering, Skin Temperature, Vasoconstriction
- Abstract
Background: The contribution of mean skin temperature to the thresholds for sweating and active precapillary vasodilation has been evaluated in numerous human studies. In contrast, the contribution of skin temperature to the control of cold responses such as arteriovenous shunt vasoconstriction and shivering is less well established. Accordingly, the authors tested the hypothesis that mean skin and core temperatures are linearly related at the vasoconstriction and shivering thresholds in men. Because the relation between skin and core temperatures might vary by gender, the cutaneous contribution to thermoregulatory control also was determined in women., Methods: In the first portion of the study, six men participated on 5 randomly ordered days, during which mean skin temperatures were maintained near 31, 34, 35, 36, and 37 degrees C. Core hypothermia was induced by central venous infusion of cold lactated Ringer's solution sufficient to induce peripheral vasoconstriction and shivering. The core-temperature thresholds were then plotted against skin temperature and a linear regression fit to the values. The relative skin and core contributions to the control of each response were calculated from the slopes of the regression equations. In the second portion of the study, six women participated on three randomly ordered days, during which mean skin temperatures were maintained near 31, 35, and 37 degrees C. At each designated skin temperature, core hypothermia sufficient to induce peripheral vasoconstriction and/or shivering was again induced by central venous infusion of cold lactated Ringer's solution. The cutaneous contributions to control of each response were then calculated from the skin- and core-temperature pairs at the vasoconstriction and shivering thresholds., Results: There was a linear relation between mean skin and core temperatures at the response thresholds in the men: r = 0.90 +/- 0.06 for vasoconstriction and r = 0.94 +/- 0.07 for shivering. Skin temperature contributed 20 +/- 6% to vasoconstriction and 19 +/- 8% to shivering. Skin temperature in the women contributed to 18 +/- 4% to vasoconstriction and 18 +/- 7% to shivering, values not differing significantly from those in men. There was no apparent correlation between the cutaneous contributions to vasoconstriction and shivering in individual volunteers., Conclusions: These data indicate that skin and core temperatures contribute linearly to the control of vasoconstriction and shivering in men and that the cutaneous contributions average approximately 20% in both men and women. The same coefficients thus can be used to compensate for experimental skin temperature manipulations in men and women. However, the cutaneous contributions to each response vary among volunteers; furthermore, the contributions to the two responses vary within volunteers. more...
- Published
- 1995
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36. Heat flow and distribution during induction of general anesthesia.
- Author
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Matsukawa T, Sessler DI, Sessler AM, Schroeder M, Ozaki M, Kurz A, and Cheng C
- Subjects
- Adult, Arm blood supply, Humans, Leg blood supply, Male, Regional Blood Flow, Anesthesia, General, Body Temperature Regulation
- Abstract
Background: Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution., Methods: Six minimally clothed male volunteers in an approximately 22 degrees C environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in distal esophageal (core) temperature, leaving the core hypothermia specifically resulting from redistribution., Results: Core temperature was nearly constant during the control period but decreased 1.6 +/- 0.3 degree C in the first hour of anesthesia. Redistribution contributed 81% to this initial decrease and required transfer of 46 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 1.1 +/- 0.3 degree C, with redistribution contributing only 43%. Thus, only 17 kcal was redistributed during the second and third hours of anesthesia. Redistribution therefore contributed 65% to the entire 2.8 +/- 0.5 degree C decrease in core temperature during the 3 h of anesthesia. Proximal extremity heat content decreased slightly after induction of anesthesia, but distal heat content increased markedly. The distal extremities thus contributed most to core cooling. Although the arms constituted only a fifth of extremity mass, redistribution increased arm heat content nearly as much as leg heat content. Distal extremity heat content increased approximately 40 kcal during the first hour of anesthesia and remained elevated for the duration of the study., Conclusions: The arms and legs are both important components of the peripheral thermal compartment, but distal segments contribute most. Core hypothermia during the first hour after induction resulted largely from redistribution of body heat, and redistribution remained the major cause even after 3 h of anesthesia. more...
- Published
- 1995
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37. Epidural anesthesia increases apparent leg temperature and decreases the shivering threshold.
- Author
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Emerick TH, Ozaki M, Sessler DI, Walters K, and Schroeder M
- Subjects
- Adult, Body Temperature Regulation, Female, Humans, Leg, Monitoring, Physiologic, Anesthesia, Epidural, Shivering physiology, Skin Temperature
- Abstract
Background: Lower core temperatures than usual are required to trigger shivering during epidural and spinal anesthesia, but the etiology of this impairment remains unknown. In this investigation, we propose and test a specific mechanism by which a peripheral action of regional anesthesia might alter centrally mediated thermoregulatory responses. Conduction anesthesia blocks all thermal sensations; however, cold signals are disproportionately affected because at typical leg temperatures mostly cold receptors fire tonically. It thus seems likely that epidural and spinal anesthesia increase the leg temperature perceived by the thermoregulatory system. Because skin temperature reportedly contributes 5-20% to thermoregulatory control, increased apparent (as distinguished from actual) leg temperature would produce a complimentary decrease in the core temperature triggering thermoregulatory shivering. Accordingly, we tested the hypothesis that abnormal tolerance for hypothermia during epidural anesthesia coincides with an increase in apparent leg temperature. We defined apparent temperature as the leg-skin temperature required to induce a reduction in the shivering threshold comparable to that produced by epidural anesthesia., Methods: Six women were studied on 4 randomly ordered days: (1) leg-skin temperature near 32 degrees C; (2) leg-skin temperature near 36 degrees C; (3) leg-skin temperature near 38 degrees C; and (4) epidural anesthesia without leg-warming (leg-skin temperature approximately 34 degrees C). At each designated leg temperature, core hypothermia sufficient to evoke shivering was induced by central venous infusion of cold fluid. Upper-body skin temperature was kept constant throughout. In each volunteer, linear regression was used to calculate the correlation between the shivering thresholds on the 3 non-epidural days and concurrent leg temperatures. The slope of these regression equations thus indicated the extent to which leg-warming increased thermoregulatory tolerance for core hypothermia, and was expressed as a percentage leg-skin and leg-tissue contribution to total thermal afferent input. The skin and tissue temperatures that would have been required to produce the observed shivering threshold during epidural anesthesia, the apparent temperatures, were then interpolated from the regression., Results: There was a good linear relation between the shivering threshold and leg-skin temperature (r2 = 0.94 +/- 0.06). The contribution of leg-skin temperature to the shivering threshold was 11 +/- 3% of the total thermal input. Apparent leg-skin temperature during epidural anesthesia was 37.8 +/- 0.5 degrees C, which exceeded actual leg-skin temperature by approximately 4 degrees C. The contribution of leg-tissue temperature to the shivering threshold was 19 +/- 7% of the total. Apparent leg-tissue temperature during epidural anesthesia was 37.1 +/- 0.4 degrees C, which exceeded actual leg-skin temperature by approximately 2 degrees C., Conclusions: Because leg-skin contributed approximately 11% to the shivering threshold, it is unlikely that the entire skin surface contributes at much less than 20%. These data suggest that the shivering threshold during epidural anesthesia is reduced by a specific mechanism, namely that conduction block significantly increases apparent (as distinguished from actual) leg temperature. more...
- Published
- 1994
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38. Thermoregulatory thresholds during epidural and spinal anesthesia.
- Author
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Ozaki M, Kurz A, Sessler DI, Lenhardt R, Schroeder M, Moayeri A, Noyes KM, and Rotheneder E
- Subjects
- Adult, Anesthetics, Local pharmacology, Humans, Male, Monitoring, Physiologic, Procaine analogs & derivatives, Procaine pharmacology, Reference Values, Shivering, Sweating, Vasoconstriction, Anesthesia, Epidural, Anesthesia, Spinal, Body Temperature Regulation drug effects
- Abstract
Background: There are significant physiologic differences between spinal and epidural anesthesia. Consequently, these two types of regional anesthesia may influence thermoregulatory processing differently. Accordingly, in volunteers and in patients, we tested the null hypothesis that the core-temperature thresholds triggering thermoregulatory sweating, vasoconstriction, and shivering are similar during epidural and spinal anesthesia., Methods: Six male volunteers participated on three consecutive study days: epidural or spinal anesthesia were randomly assigned on the 1st and 3rd days (approximately T10 level); no anesthesia was given on the 2nd day. On each day, the volunteers were initially warmed until they started to sweat, and subsequently cooled by central venous infusion of cold fluid until they shivered. Mean skin temperature was kept constant near 36 degrees C throughout each study. The tympanic membrane temperatures triggering a sweating rate of 40 g.m-2.h-1, a finger flow less than 0.1 ml/min, and a marked and sustained increase in oxygen consumption (approximately 30%) were considered the thermoregulatory thresholds for sweating, vasoconstriction, and shivering, respectively. Twenty-one patients were randomly assigned to receive epidural (n = 10) or spinal (n = 11) anesthesia for knee and calf surgery (approximately T10 level). As in the volunteers, the shivering threshold was defined as the tympanic membrane temperature triggering a sustained increase in oxygen consumption., Results: The thresholds and ranges were similar during epidural and spinal anesthesia in the volunteers. However, the sweating-to-vasoconstriction (inter-threshold) range, the vasoconstriction-to-shivering range, and the sweating-to-shivering range all were significantly increased by regional anesthesia. The shivering thresholds in patients assigned to epidural and spinal anesthesia were virtually identical., Conclusions: Comparable sweating, vasoconstriction, and shivering thresholds during epidural and spinal anesthesia suggest that thermoregulatory processing is similar during each type of regional anesthesia. However, thermoregulatory control was impaired during regional anesthesia, as indicated by the significantly enlarged inter-threshold and sweating-to-shivering ranges. more...
- Published
- 1994
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39. Rate and gender dependence of the sweating, vasoconstriction, and shivering thresholds in humans.
- Author
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Lopez M, Sessler DI, Walter K, Emerick T, and Ozaki M
- Subjects
- Adult, Female, Humans, Male, Sex Factors, Tympanic Membrane physiology, Body Temperature Regulation physiology, Sensory Thresholds physiology, Shivering physiology, Skin blood supply, Skin Temperature physiology, Sweating physiology, Vasoconstriction physiology
- Abstract
Background: The range of core temperatures not triggering thermoregulatory responses ("interthreshold range") remains to be determined in humans. Although the rates at which perioperative core temperatures vary typically range from 0.5 to 2 degrees C/h, the thermoregulatory contribution of different core cooling rates also remains unknown. In addition, sweating in women is triggered at a slightly greater core temperature than in men. However, it is unknown whether the vasoconstriction and shivering thresholds are comparably greater in women, or if women tolerate a larger range of core temperatures without triggering thermoregulatory responses. Accordingly, the authors sought to (1) define the interthreshold range; (2) test the hypothesis that, at a constant skin temperature, the vasoconstriction and shivering thresholds are greater during rapid core cooling than during slowly induced hypothermia; and (3) compare the sweating, vasoconstriction, and shivering thresholds in men and women., Methods: Eight men and eight women participated. The men participated on 2 separate days; no anesthesia or sedatives were administered. On each day, they were cutaneously warmed until sweating was induced and then were cooled by a central venous infusion of cold fluid. The cooling rates were 0.7 +/- 0.1 degrees C/h on 1 day and 1.7 +/- 0.4 degrees C/h on the other, randomly ordered. Skin temperature was maintained near 36.7 degrees C throughout each trial. The women were studied only once, in the follicular phase of their menstrual cycles, at the greater cooling rate., Results: The interthreshold range was approximately 0.2 degrees C in both men and women, but all thermoregulatory response thresholds were approximately 0.3 degrees C higher in women. All thresholds were virtually identical during slow and fast core cooling., Conclusions: Our findings confirm the existence of an interthreshold range and document that its magnitude is small. They also demonstrate that the interthreshold range does not differ in men and women, but that women thermoregulate at a significantly higher temperature than do men. Typical clinical rates of core cooling do not alter thermoregulatory responses. more...
- Published
- 1994
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40. Epidural anesthesia impairs both central and peripheral thermoregulatory control during general anesthesia.
- Author
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Joris J, Ozaki M, Sessler DI, Hardy AF, Lamy M, McGuire J, Blanchard D, Schroeder M, and Moayeri A
- Subjects
- Adolescent, Adult, Aged, Anesthetics, Local, Child, Female, Humans, Isoflurane, Male, Middle Aged, Procaine analogs & derivatives, Reference Values, Surgical Procedures, Operative, Anesthesia, Epidural, Anesthesia, General, Body Temperature Regulation physiology, Vasoconstriction physiology
- Abstract
Background: The authors tested the hypotheses that: (1) the vasoconstriction threshold during combined epidural/general anesthesia is less than that during general anesthesia alone; and (2) after vasoconstriction, core cooling rates during combined epidural/general anesthesia are greater than those during general anesthesia alone. Vasoconstriction thresholds and heat balance were evaluated under controlled circumstances in volunteers, whereas the clinical importance of intraoperative thermoregulatory vasoconstriction was evaluated in patients., Methods: Five volunteers were each evaluated twice. On one of the randomly ordered days, epidural anesthesia (approximately T9 dermatomal level) was induced and maintained with 2-chloroprocaine. On both study days, general anesthesia was induced and maintained with isoflurane (0.7% end-tidal concentration), and core hypothermia was induced by surface cooling and continued for at least 1 h after fingertip vasoconstriction was observed. Patients undergoing colorectal surgery were randomly assigned to combined epidural/enflurane anesthesia (n = 13) or enflurane alone (n = 13). In appropriate patients, epidural anesthesia was maintained by an infusion of bupivacaine. The core temperature that triggered fingertip vasoconstriction identified the threshold., Results: In the volunteers, the vasoconstriction threshold was 36.0 +/- 0.2 degrees C during isoflurane anesthesia alone, but significantly less, 35.1 +/- 0.7 degrees C, during combined epidural/isoflurane anesthesia. Cutaneous heat loss and the rates of core cooling were similar 30 min before vasoconstriction with and without epidural anesthesia. In the 30 min after vasoconstriction, heat loss decreased 33 +/- 13 W when the volunteers were given isoflurane alone, but only 8 +/- 16 W during combined epidural/isoflurane anesthesia. Similarly, the core cooling rates in the 30 min after vasoconstriction were significantly greater during combined epidural/isoflurane anesthesia (0.8 +/- 0.2 degrees C/h) than during isoflurane alone (0.2 +/- 0.1 degrees C/h). In the patients, end-tidal enflurane concentrations were slightly, but significantly, less in the patients given combined epidural/enflurane anesthesia (0.6 +/- 0.2% vs. 0.8 +/- 0.2%). Nonetheless, the vasoconstriction threshold was 34.5 +/- 0.6 degrees C in the epidural/enflurane group, which was significantly less than that in the other patients, 35.6 +/- 0.8 degrees C. When the study ended after 3 h of anesthesia, patients given combined epidural/enflurane anesthesia were 1.2 degrees C more hypothermic than those given general anesthesia alone. The rate of core cooling during the last hour of the study was 0.4 +/- 0.2 degrees C/h during combined epidural/enflurane anesthesia, but only 0.1 +/- 0.3 degrees C/h during enflurane alone., Conclusions: These data indicate that epidural anesthesia reduces the vasoconstriction threshold during general anesthesia. Furthermore, the markedly reduced rate of core cooling during general anesthesia alone illustrates the importance of leg vasoconstriction in maintaining core temperature. more...
- Published
- 1994
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41. The pupillary light reflex. Effects of anesthetics and hyperthermia.
- Author
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Belani KG, Sessler DI, Larson MD, Lopez MA, Washington DE, Ozaki M, McGuire J, Merrifield B, and Schroeder M
- Subjects
- Adult, Female, Humans, Isoflurane pharmacology, Light, Male, Nitrous Oxide pharmacology, Pupil drug effects, Reflex, Pupillary physiology, Anesthetics pharmacology, Fever physiopathology, Reflex, Pupillary drug effects
- Abstract
Background: The pupillary light reflex often is evaluated in the perianesthetic period to assess drug effects and brainstem function. Mild hypothermia alone or combined with isoflurane does not impair pupillary responses. Although perioperative hyperthermia is less common than hypothermia, abnormal increases in core temperature remain an important thermal disturbance. Accordingly, the pupillary effects of hyperthermia alone and hyperthermia combined with isoflurane and enflurane were evaluated. Additionally, the effects of nitrous oxide on pupillary responses were determined., Methods: The pupillary light reflex was evaluated in 31 non-surgical volunteers participating in concurrent thermoregulatory studies. Pupillary reflexes were quantified using a portable infrared pupillometer during (1) hyperthermia alone (n = 9), (2) hyperthermia with 0.8% and 1.2% end-tidal isoflurane (n = 8), (3) hyperthermia with 1.7% end-tidal enflurane (n = 5), and (4) inhalation of 60% N2O (n = 9)., Results: Mild hyperthermia alone (core temperature 38.5 +/- 0.3 degrees C) produced no clinically significant change in the pupillary light reflex. Pupillary responses were decreased markedly with 0.8% isoflurane, 1.2% isoflurane, and 1.7% enflurane when the volunteers were normothermic. Mild hyperthermia combined with isoflurane or enflurane dilated the pupil and increased the amplitude of the light reflex. Sixty-percent nitrous oxide decreased the pupillary reflex only 26 +/- 4%., Conclusions: Anesthetic-induced inhibition of the pupillary response to light is reversed partially by core hyperthermia. In contrast to enflurane and isoflurane, 60% N2O has little effect on the pupil. more...
- Published
- 1993
- Full Text
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42. Pupillary assessment of sensory block level during combined epidural/general anesthesia.
- Author
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Larson MD, Sessler DI, Ozaki M, McGuire J, and Schroeder M
- Subjects
- Adult, Electric Stimulation, Female, Humans, Male, Middle Aged, Predictive Value of Tests, Psychomotor Performance drug effects, Anesthesia, Epidural methods, Anesthesia, General methods, Autonomic Nerve Block, Pupil drug effects, Reflex, Pupillary drug effects
- Abstract
Background: Currently, no reliable method exists to determine the level of sensory block during combined epidural/general anesthesia. However, the pupil dilates markedly in response to noxious electrical stimulation during general anesthesia. Presumably, sensory block produced by epidural anesthesia decreases or obliterates this autonomic response. Accordingly, we tested the hypothesis that pupillary dilation in response to noxious stimulation would predict the level of sensory block achieved during combined epidural/general anesthesia., Methods: We studied eight volunteers and ten patients during combined epidural/general anesthesia. The volunteers were given an epidural infusion of 2% 2-chloroprocaine while general anesthesia was maintained with 0.8% isoflurane and 60% N2O. In the patients, an epidural infusion of 0.25% bupivacaine was combined with isoflurane and vecuronium. Noxious electrical stimulation was administered to dermatomal segments in a caudal-to-rostral progression. A twofold increase in pupil size following electrical stimulation was considered the predicted block level in volunteers. In patients, an increase in pupil size exceeding 50% was considered the predicted level. After general anesthesia was discontinued, observers blinded to the pupillary measurements independently determined the actual epidural block level using pain in response to a pinprick as the criterion., Results: The level predicted by pupillary responses was within two dermatomal segments of the actual level in all the volunteers. The predicted and actual block levels were within two segments in eight of the ten patients and never differed by more than four dermatomes., Conclusions: We conclude that dilation of the pupil in response to electrical stimulation is an accurate test of the sensory block level during combined epidural/general anesthesia. more...
- Published
- 1993
- Full Text
- View/download PDF
43. Physiologic responses to hyperthermia during epidural anesthesia and combined epidural/enflurane anesthesia in women.
- Author
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Lopez M, Ozaki M, Sessler DI, and Valdes M
- Subjects
- Adult, Female, Humans, Sweating physiology, Vasodilation physiology, Anesthesia, Epidural, Anesthesia, Inhalation, Body Temperature Regulation physiology, Enflurane, Hyperthermia, Induced
- Abstract
Background: During combined epidural/isoflurane anesthesia, the core temperature triggering finger-tip vasoconstriction is approximately 1 degree C less than that triggering redilation. This hysteresis suggests that thermoregulatory responses are not dependent entirely on current thermal status (state-dependence), but may be influenced also by the system's recent thermal history (direction-dependence). Once triggered, the gain and maximum response intensity of many thermoregulatory responses is nearly normal during isoflurane anesthesia. However, it remains unknown whether preserved gain and maximum response intensities are a characteristic paradigm describing thermoregulatory responses to general anesthetics. Also unknown is whether the sweating and pre-capillary vasodilation thresholds are comparably impaired by different volatile anesthetics. Accordingly, the authors tested the hypotheses that, during one minimum alveolar concentration of enflurane anesthesia: (1) there is a direction-dependent hysteresis for sweating; (2) the sweating and active vasodilation thresholds increase approximately 1.2 degrees C, as they do during one minimum alveolar concentration of isoflurane; and (3) the gain and maximum intensity of sweating are well preserved., Methods: Six female volunteers each were studied on 2 days, once during epidural anesthesia alone and once with combined enflurane (1.7%)/epidural anesthesia. On each study day, core hyperthermia was induced by cutaneous warming restricted to the legs. Warming continued until chest sweating reached maximal values; the volunteers then were cooled gradually until sweating stopped. The core temperature at which the sweating rate departed from baseline values was considered the activation threshold. Gain was expressed as the slope of the sweating rate versus core temperature curve within the range 25-75% of the maximum sweating rate. Hysteresis was evaluated by subtracting the tympanic membrane temperature at which the sweating rate suddenly increased during warming (approximately 25% above baseline values) from that at which sweating precipitously decreased during cooling (approximately 75% of maximum values)., Results: The sweating threshold was 1.4 +/- 0.7 degrees C higher during combined enflurane/epidural anesthesia than during epidural anesthesia alone. Maximum intensity was approximately 700 g.m-2.h-1, and the gain approximately 1,300 g.m-2.h-1.degrees C-1 during each treatment. No hysteresis was detected on either study day., Conclusions: One minimum alveolar concentration of enflurane increased the sweating threshold only slightly more than previously reported for isoflurane. As in previous studies of sweating and vasoconstriction during isoflurane anesthesia, gain and maximum response intensity were well preserved during enflurane anesthesia. An increase in the interthreshold range (temperatures not triggering thermoregulatory responses), with little change in gain and maximum response intensities, appears to be the typical effect of volatile anesthetics. Sweating during enflurane anesthesia appears to be state-dependent and little influenced by the direction of core temperature perturbations. more...
- Published
- 1993
- Full Text
- View/download PDF
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