SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Hypothermia and postoperative shivering are uncomfortable and may be dangerous. This study demonstrates that postoperative shivering may be controlled quickly and effectively with radiant heat, thereby reducing oxygen consumption and increasing thermal comfort.
A 25-yr-old man, subsequently shown to be malignant hyperthermia (MH) susceptible by in vitro contracture testing, developed MH during anaesthesia for tonsillectomy. Prompt treatment, including dantrolene, led to rapid resolution of the metabolic crisis. Eighteen hours later the patient's trachea was extubated in the ICU, when he had been stable and apyrexial overnight. Twenty minutes after extubation, an episode of shivering was followed by the onset of tachycardia, hypertension, tachypnoea and a rapid increase in temperature. Recurrence of MH was suspected and the patient was given another dose of dantrolene with good clinical effect. Shivering in this patient may have been an indicator or a causative factor of recurrence of MH.
The authors tested the hypothesis that during epidural anesthesia: 1) shivering-like tremor is primarily normal thermoregulatory shivering; 2) hypothermia does not produce a subjective sensation of cold; and 3) injectate temperature does not influence tremor intensity. An epidural catheter was inserted into ten healthy, nonpregnant volunteers randomly assigned to skin-surface warming below the T10 dermatome (warmed group) or no extra warming (unwarmed group). Each volunteer was given two 30-ml epidural injections of 1% lidocaine (16.0 +/- 4.7 degrees C and 40.6 +/- 0.7 degrees C at the catheter tip), in random order separated by at least 3 h. Skin-temperature gradients (forearm-fingertip) and tympanic membrane and average skin temperatures were recorded; significant vasoconstriction was prospectively defined as a gradient greater than or equal to 4 degrees C. Integrated electromyographic (EMG) intensity was recorded from four upper-body muscles. Overall thermal comfort was evaluated using a visual analog scale. Tympanic membrane temperatures decreased significantly in the unwarmed group (n = 6). Tremor occurred following ten of 12 injections in unwarmed volunteers, but only following one of eight injections in the warmed group. Integrated EMG intensity did not differ significantly following epidural injection of warm and cold lidocaine: tremor started when tympanic membrane temperature decreased about 0.5 degrees C and continued until central temperature returned to within 0.5 degrees C of control. Tremor always was preceded by hypothermia and vasoconstriction in the arms. Thermal comfort increased in both groups after epidural injection, with maximal comfort occurring at the lowest tympanic temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)
The cause of postoperative shivering is not known. The theories and possible remedies are reviewed. Five hundred patients were observed for the possible effect of lissive doses of gallamine, and of analgesic or benzodiazepine premedication. Diazepam premedication appeared to reduce the incidence of post-halothane shivering.
A group of patients who developed postoperative shivering after receiving inhalational anaesthesia were assigned, at random, to receive either doxapram or a placebo under double-blind conditions. A significantly higher proportion of patients stopped shivering after being given doxapram than after the placebo.
Sixty ASA grade 1 unpremedicated patients scheduled for minor elective surgery were randomly allocated to receive general anaesthesia consisting of either propofol-nitrous oxide in oxygen or a conventional technique of thiopentone-isoflurane-nitrous oxide-oxygen. Baseline axillary temperature readings, duration of operation and intra-operative decrease in axillary temperature were similar in both groups. The patients who received propofol-nitrous oxide-oxygen anaesthesia had a significantly lower incidence of postanaesthetic shivering than the control group. A propofol-nitrous oxide-oxygen technique may be preferable when postanaesthetic shivering is deemed undesirable.
To study the significance of normalization of ventilatory or thermal homeostasis during naloxone reversal, 95 patients were given naloxone after thiopental-N2O-O2-relaxant anaesthesia supplemented with fentanyl (6 microgram/kg/h). If naloxone 0.16 mg was given to combat postoperative apnoea during hypercapnia (end tidal carbon dioxide concentration (ETco2)8%), minute ventilation and respiratory rate were significantly higher during the first minutes as compared to the normocapnic patients. Shivering occurred in 44% in the hypercapnic group, as compared to about 30% if naloxone was given during normocapnia (ETco2 5%). Postoperative pain and restlessness were significantly increased in the hypercapnic group. During normocapnia, untoward reactions were less frequent (40%) if naloxone was given in smaller increments (0.08 + 0.08 mg) rather than in one dose (0.16 mg) (72%). This was mainly due to nausea (8% compared to 32%). The incidence and severity of shivering showed a positive correlation to the duration of anaesthesia (r = 0.42) and to the total amount of fentanyl (r = 0.32), but not to the actual postoperative oesophageal temperature (r = -0.13). The results indicate that though untoward reactions after naloxone reversal are aggravated by naloxone-induced normalization of deranged homeostatic mechanisms, their aetiology probably should be sought in an acute abstinence syndrome.
BACKGROUND: The infusion of several liters of crystalloid solution at room temperature may significantly contribute to intraoperative hypothermia because warming fluid to core temperature requires body heat. The aim of this study was to evaluate the effect of delivering warmed intravenous (IV) fluid to the patient on preventing intraoperative hypothermia. METHODS: Intraoperative core and mean skin temperatures were measured during prolonged abdominal surgery in 18 patients randomly divided into two groups according to intraoperative IV fluid management. In 9 patients (control group) all IV fluids infused were at room temperature. In the other 9 patients (group receiving warmed fluids) all IV fluids were warmed using an active IV fluid tube-warming system. In all 18 patients a warming blanket covered the skin surface available for cutaneous warming. Intraoperative changes in total body heat content (kJ) were calculated from core and mean skin temperatures. RESULTS: At the end of surgery, core temperature was 36.7 +/- 0.2 degrees C in the group receiving warmed fluids and 35.8 +/- 0.2 degrees C in the control group (P < 0.05). The estimated reduction in heat loss provided by warming IV fluid was 217 kJ, a value very close to the theoretical value expected from thermodynamic calculation. During recovery, one patient shivered in the group receiving warmed fluids and seven in the control group (P < 0.05). CONCLUSION: In conclusion, infusion of warmed fluids, combined with skin-surface warming, helps to prevent hypothermia and reduces the incidence of postoperative shivering.
The contribution of the facial thermoreceptors to thermoregulatory shivering was studied. Seven subjects were exposed to -3 degrees C ambient air for 1 h. Radiant heat was applied to the facial area during 30 s periods at 10 min intervals and the effects on the integrated electromyographic activity (IEMG) in the brachial biceps, trapezius and femoral rectus muscles, and on the heart rate (HR) were studied. During cold-air exposure mean skin temperature as measured at four sites decreased by 15.5 +/- 0.6 degrees C (mean +/- SE) while rectal temperature remained virtually unchanged. During the radiant heat exposures IEMG activity decreased by 18.9 +/- 2.3%; HR decreased by 11 +/- 1 beats min-1. The changes in IEMG occurred within or slightly below the range of maximum cold receptor sensitivity (20-30 degrees C) and coincided with the maximum rate of change in chin temperature. The observed inhibition of shivering IEMG during locally applied facial heat stimulation suggest that the trigeminal region contributes an important input to the overall thermoregulatory responses.
In man hypothermia exists when core temperature (Tc) falls below 35 degrees C. The onset of hypothermia is often insidious in that it can occur without any particular symptoms of serious discomfort. There is evidence that this decrease in thermosensitivity is most likely to occur when the rate of body cooling is slow. In addition there is some evidence that the susceptibility to become hypothermic varies with the circadian rhythm of Tc, particularly in animals maintained under constant light conditions. A systematic investigation has been carried out to determine whether the thermoregulatory response to body core cooling is affected by the rate of change of body temperature, the time of day at which the cooling takes place and/or by the light regime under which the animals are maintained. The investigation was made in rabbits maintained either under a 12-h light/dark (LD) cycle or under conditions of continuous light (LL). Thermosensitivity (relationship between falling Tc and the induced increase in metabolic heat production) was determined at two different rates of body cooling (1 degrees C decrease in core temperature in either 30 or 160 min.) and at different times of the day. A chronically implanted intravascular heat exchanger was used to extract heat from the animals. The results indicate that neither the rate of body cooling nor the time of day at which the cooling took place had any clear effect on the shivering response. Likewise there was no clear difference in the shivering response of the animals maintained under (LD) conditions as compared to those maintained under (LL) conditions.
The possible role of humoral factors in the control of shivering in the common eider duck (Somateria mollissima) was investigated using a cross-circulation technique. Pairs of animals were coupled so that the arterial system of one animal was connected to the venous system of the other. The rate of blood transferral was 12.8 ml min-1. By adequate heparinization of the extracorporeal blood supply, cross-circulation could be maintained for periods of up to 12 h. The temperature of blood entering each animal Tinlet) was controlled by heat exchangers. During control experiments Tinlet was maintained at a temperature close to normal body temperature. During cooling experiments Tinlet was maintained at c. 20 degrees C. Changes in metabolic heat production and oesophageal temperature in response to blood cooling were measured in cross-circulated pairs of animals cooled simultaneously or individually. Based on analysis of the metabolic responses under the different experimental situations, no evidence was found to indicate that blood-borne substances are involved in the shivering response in these animals.
In summary, we present a new model for evaluating thermoregulatory effects of drug administration, pregnancy, illness, etc. Specifically, we experimentally manipulated both skin and core temperatures, and subsequently compensated for the changes in skin temperature using the relationships between skin and core contributions to thermoregulatory control. We thus were able to report our results for warm- and cold-responses in terms of calculated core-temperature thresholds at a single designated skin temperature. Advantages of this model include its being nearly noninvasive and requiring relatively little core temperature manipulation. Using this technique, we have shown that the shape and magnitude of thermoregulatory impairment produced by various anesthetic drugs differs. Propofol linearly increases the sweating threshold and linearly decreases the vasoconstriction and shivering threshold. In contrast, volatile anesthetics produce a nonlinear reduction in the major cold-response thresholds, reducing the vasoconstriction and shivering thresholds disproportionately at higher anesthetic concentrations. Midazolam not only produces a different magnitude of thermoregulatory impairment, but also a novel pattern of threshold changes. Anesthetic-induced thermoregulatory impairment thus depends both on anesthetic type and dose.
1. Five subjects with spinal cord transections and one subject unconscious from a head injury have been studied when the deep tissue temperature (;central' temperature) was artificially lowered but normally innervated skin was kept warm, usually 34-36 degrees C.2. Shivering and/or increased metabolism was evoked when the central temperature was 34.9-37 degrees C.3. These observations are compatible with the view that there is a central receptor which can cause shivering when stimulated by a fall in central temperature.
Twenty-two male Caucasians, aged 20-47 yr, were exposed in a cold room to air temperatures of -33 degrees C while lying in sleeping bags for 2 h. Skin and rectal temperatures as well as electromyographic activity of the chin, forearm, and thigh, were recorded. Shivering occurred in all the subjects, even though skin temperatures were maintained between 31 and 33 degrees C. It is suggested that a counter-current heat exchange occurs whereby the warm blood of the common carotid artery is cooled by cool venous blood in the jugular veins. This cooled arterial blood, in irrigating the hypothalamus, causes shivering.
The purpose of the present study was to clarify the importance of skeletal muscle glycogen as a fuel for shivering thermogenesis in humans during cold-water immersion. Fourteen seminude subjects were immersed to the shoulders in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Biopsies from the vastus lateralis muscle and venous blood samples were obtained before and immediately after the immersion. Metabolic rate increased during the immersion to 3.5 +/- 0.3 (SE) times resting values, whereas Tre decreased by 0.9 degrees C to approximately 35.8 degrees C at the end of the immersion. Intramuscular glycogen concentration in the vastus lateralis decreased from 410 +/- 15 to 332 +/- 18 mmol glucose/kg dry muscle, with each subject showing a decrease (P less than 0.001). Plasma volume decreased (P less than 0.001) markedly during the immersion (-24 +/- 1%). After correcting for this decrease, blood lactate and plasma glycerol levels increased by 60 (P less than 0.05) and 38% (P less than 0.01), respectively, whereas plasma glucose levels were reduced by 20% after the immersion (P less than 0.001). The mean expiratory exchange ratio showed a biphasic pattern, increasing initially during the first 30 min of the immersion from 0.80 +/- 0.06 to 0.85 +/- 0.05 (P less than 0.01) and decreasing thereafter toward basal values. The results demonstrate clearly that intramuscular glycogen reserves are used as a metabolic substrate to fuel intensive thermogenic shivering activity of human skeletal muscle.
Shivering and physiological and pathological clonus of the ankle were compared using power spectral and cross-correlation analysis of their respective electromyographic and acceleration waveforms. The major spectral peaks from each type of involuntary oscillation possessed similar frequencies (5-7 Hz). Soleus electromyographic activity was significantly correlated with the motion signal, whereas no correlation was observed between motion and tibialis anterior electromyographic signal. These data suggest that although shivering and physiological and pathological clonus are activated by different stimuli, these overt ankle oscillations may be an expression of a common spinal neuronal network.
Carbohydrates (CHO) can play an important thermogenic role during shivering, but the effect of their availability on the use of other oxidative fuels is unclear. Using indirect calorimetry and tracer methods ([U-13C]glucose ingestion), we have determined the specific contributions of plasma glucose, muscle glycogen, proteins, and lipids to total heat production (Hprod) in men exposed to cold for 2-h (liquid-conditioned suit perfused with 10 degrees C water). Measurements were made after low-CHO diet and exercise (Lo) and high-CHO diet without exercise (Hi). The size of CHO reserves had no effect on Hprod but a major impact on fuel selection before and during shivering. In the cold, a complete shift from lipid oxidation for Lo (53, 28, and 19% Hprod for lipids, CHO, and proteins, respectively) to CHO-based metabolism for Hi (23, 65, and 12% Hprod for lipids, CHO, and proteins, respectively) was observed. Plasma glucose oxidation remains a minor fuel under all conditions (<13% Hprod), falling to 7% Hprod for Lo. Therefore, adjusting plasma glucose oxidation to compensate for changes in muscle glycogen oxidation is not a strategy used for maintaining heat production. Instead, proteins and lipids share responsibility for this compensation. We conclude that humans can show remarkable flexibility in oxidative fuel selection to ensure that heat production is not compromised during sustained cold exposure.
A new mutant with shivering, Hula dance Sendai (tentatively named hus gene), was found in the IVCE strain. A congenic strain, C57BL/6JJcl-hus, was established by the cross-intercross method using IVCE-hus as the donor strain and C57BL/6JJcl as the recipient. No significant differences were observed in the age of the onset of shivering and life span between B6-hus and IVCE-hus mice. Genetic analyses demonstrated that this mutation is governed by an autosomal recessive gene (Mbphus) and is an allele of the Mbpshi gene (Chr. 18).