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[Thermoregulatory activity of the intercostal muscles under a hypercapnic load].

In experiments on anesthetized cats, the reactions elicited by CO2 inhalation were studied in single motor units of the intercostal muscles activated during shivering. The excitation of the bulbar respiratory center during shivering was found to modify the activity of the respiratory and tonic motor units. Most of the respiratory motor units in a hypercapnic state increased the mean firing rate by 1.5/sec. The tonic motor units both diminished the mean firing rate and changed the pattern of activity: they began to produce bursts of spikes synchronous with the respiratory rhythm. The problems of supraspinal regulation of activity of the intercostal muscles motoneuron pool are discussed.

Animals↗

Operating room temperature prior to surgical draping: effect on patient temperature in recovery room.

Assessment was made of whether a cold-room environment prior to surgical draping affected patient temperature or the incidence of shivering in the recovery room in patients undergoing major vascular surgery when warming blankets and warmed fluids were used to maintain intraoperative temperature. Forty-two patients scheduled to undergo major vascular surgery were randomly assigned in equal numbers to a "cold or "warm" room. Temperatures in the "warm" rooms were 22.2 C or above (range 22.8-25.6 C) until draping, and in "cold" rooms, 18.9 C or below (ranged 13.9-17.8 C). Once surgical drapes were placed, the room temperature control was set at its minimum, 17 C. All intravenous fluids and blood were warmed to 37.5 C, and a heating blanket was maintained at 37.8 C before and during the operative procedure. Patient temperatures initially did not differ between groups. Despite significantly greater heat loss prior to draping in the cold-room group (0.63 +/- 0.14 C) than in the warm-room group (0.32 +/- 0.10 C) (p < 0.01), there were no differences in temperature in the recovery room, shivering, myocardial, renal CNS, pulmonary, or graft morbidity in the two groups. In major intra-abdominal vascular operations the use of warming blankets and the practice of warming all fluids for infusion allow a comfortable room temperature without detriment to patient care.

Body Temperature↗

[Effect of insulin on temperature and metabolic responses in rats during normothermia and hypothermia].

As shown in our previous study, hypothermia provokes a variety of hormonal changes including inhibition of insulin secretion and increase in blood serum glucagon level. According to Therminarias et al. the administration of exogenous insulin to dogs subjected to hypothermia causes a calorigenic effect by enhancing oxygen consumption and rising the intensity of shivering thermogenesis. The study was aimed at establishing whether exogenous insulin administered to rats subjected to brief hypothermia and having the shivering thermogenesis blocked by thiobutabarbital anesthesia can influence rectal temperature, the levels of some hormones and energy metabolism. The results obtained suggest that 1) insulin administration causes an increase in the energy charge potential (ECP) both in the liver and in skeletal muscle of the rat, indicating the domination of anabolic processes both in normothermic and hypothermic conditions, 2) there is a negative correlation between the levels of insulin and free fatty acids and the activity of isocitric dehydrogenase in rat liver mitochondria, and 3) the administration of insulin at a dose provoking metabolic response both in normothermic and hypothermic conditions was ineffective in provoking temperature response, indicating the existence of a functional dissociation between the various effects of the same dose of exogenous insulin.

Animals↗

Combined spinal and epidural anesthesia for abdominal hysterectomy in a patient with myotonic dystrophy. Case report.

BACKGROUND AND OBJECTIVES: The authors report a case of myotonic dystrophy in a 34-year-old woman who presented for total abdominal hysterectomy. The goal of anesthetic management is to prevent the known triggers of myotonic crisis, such as hypothermia, shivering, and hyperkalemia; and to avoid depolarizing muscle relaxants and anticholinesterase agents. METHODS: In this patient, the authors used combined spinal and epidural block for intraoperative anesthesia and postoperative analgesia. RESULTS: The advantages of the combined technique offers rapid onset and good muscle relaxation from subarachnoid block, with the ability to supplement analgesia through the epidural catheter both during and after surgery. In addition, the potential complications associated with general anesthesia, including respiratory insufficiency, aspiration pneumonia, cardiac arrhythmia, and heart failure can be avoided. The other measures were directed toward the prevention of shivering, a common problem encountered with general or regional anesthesia. CONCLUSIONS: After the postoperation, optimal analgesia was obtained by infusing local anesthetic (0.125% bupivacaine) via the epidural catheter. No obvious side effects occurred. The authors believe combined spinal and epidural block provides a safe alternative, to other techniques, and minimizes the potential hazards of myotonic dystrophy, while offering effective intraoperative anesthesia and postoperative analgesia.

Adult↗

Effects of a bedbath on mixed venous oxygen saturation and heart rate in coronary artery bypass graft patients.

OBJECTIVE: To determine the physiologic effects of a bedbath on critically ill patients. METHODS: Thirty hemodynamically stable coronary artery bypass graft patients were studied less than 24 hours after surgery in a repeated measures, quasi-experimental design. Study sites were the medical/surgical and coronary intensive care units of a large community hospital in the south-central United States. Two bedbaths consisting of bathing and turning phases were given to subjects early (mean, 3.6 hours) and late (mean, 18.5 hours) in the immediate postoperative period. Mixed venous oxygen saturation (Svo2) and heart rate were recorded at 1-minute intervals before, during, and for 5 minutes after each bedbath. RESULTS: Mean Svo2 decreased from baseline during the bathing phase of early and late bedbaths 1.6% and 1.9%, respectively, whereas mean heart rate increased from baseline 3.2% and 1%, respectively. During the turning phase, mean Svo2 decreased from baseline 9.2% and 12.1%, respectively, whereas mean heart rate increased from baseline 5.2% and 1.8%, respectively. Svo2 declined to less than 53% in 10 (33%) subjects during both early and late bedbaths. The most severe decreases in Svo2 occurred during early bedbaths and were usually associated with coughing, shivering, and/or agitation. CONCLUSIONS: Early bedbaths caused more dramatic declines in Svo2 than late bedbaths. Coughing, shivering, and agitation accentuated Svo2 declines and could be prevented by waiting to bathe coronary artery bypass graft patients until 1 day postoperatively. Routine bathing, at least in the early postoperative period, should be reconsidered.

Baths↗

Responses to the thermal environment.

Human responses to the thermal environment and to internal heat production serve to maintain a narrow range of internal body temperatures of 36-38 C. There are two categories of responses: voluntary or behavioral responses, and involuntary or physiological autonomic responses. Voluntary or behavioral responses consist generally of avoidance or reduction of thermal stress by modification of the body's immediate environment by modification of clothing insulation or by comfort conditioning of his microenvironment. Physiological responses consist of peripheral vasoconstriction to reduce the body's thermal conductance and increased heat production by involuntary shivering in the cold, and peripheral vasodilation to increase thermal conductance and secretion of sweat for evaporative cooling in hot environments. Autonomic responses are proportional to changes in internal and mean skin temperatures. Repeated exposures to heat, humidity, and exercise will modify the physiological response mechanisms by acclimation to produce more effective responses. Physiological responses also depend on the point in a diurnal cycle, on physical fitness, and on the sex of the individual. Behavioral responses rely on thermal sensations and thermal discomfort. Thermal discomfort appears to be closely related to the level of autonomic responses so that warm discomfort is closely correlated with skin wettedness, and cold discomfort similarly relates to cold extremities and shivering activity.

Acclimatization↗

[The serotonin syndrome: review of the literature and description of an original study].

In animals the occurrence of a behavioural syndrome consisting of hyperactivity, stereotyped movements and increase of temperature has been induced by MAOIs, 5-HT precursors (L-tryptophan) and 5-HT reuptake inhibitors. Most of these manifestations were specifically blocked by a pretreatment with an inhibitor of serotonin synthesis. In humans, the association of myoclonus, diarrhea, confusion, hypomania, agitation, hyperreflexia, shivering, incoordination, fever and diaphoresis, when patients are treated with serotoninergic agents, could constitute a "serotonin syndrome". Such cases of serotonin syndrome were reported after treatments with L-tryptophan, MAOIs, serotonin reuptake inhibitors and tricyclics alone or in association. The authors prospectively evaluated all the "serotonin-related" symptoms in 38 depressed inpatients fulfilling DSM III-R criteria of major depression. 16 (42%) out of 38 patients presented at least one symptom of serotonin syndrome. In 14 cases tremor and myoclonus occurred simultaneously and 10 patients presented at the same time tremor, myoclonus, diaphoresis and shivering. Except for two patients, symptoms were transient, lasted less than one week and disappeared with the pursuit of the treatment. Most often, serotonin syndrome thus corresponds to a reaction induced by a combination of serotoninergic agents at high dosages. In very rare cases, a toxic and potentially fatal interaction can occur between MAOIs, tricyclics and selective serotonin reuptake inhibitors at therapeutic dosages. Serotonin syndrome also provides an heuristic model of the putative mode of action of antidepressants. Serotonin-related symptoms are the physical and objective expression of the antidepressant-induced increase in serotonin. The specificity of serotonin-related syndrome also needs to be discussed since most of the symptoms, such as tremor and diaphoresis, are not in all cases related to an increase in serotonin.

Akathisia, Drug-Induced↗

Serotonin syndrome from venlafaxine-tranylcypromine interaction.

Excessive stimulation of serotonin 5HT1A receptors causes a syndrome of serotonin excess that consists of shivering, muscle rigidity, salivation, confusion, agitation and hyperthermia. The most common cause of this syndrome is an interaction between a monoamine oxidase inhibitor (MAOI) and a specific serotonin reuptake inhibitor. Venlafaxine is a new antidepressant agent that inhibits the reuptake of serotonin and norepinephrine. We report a venlafaxine-MAOI interaction that resulted in the serotonin syndrome in a 23-y-old male who was taking tranylcypromine for depression. He had been well until the morning of presentation when he took 1/2 tab of venlafaxine. Within 2 h he became confused with jerking movements of his extremities, tremors and rigidity. He was brought directly to a hospital where he was found to be agitated and confused with shivering, myoclonic jerks, rigidity, salivation and diaphoresis. His pupils were 7 mm and sluggishly reactive to light. Vital signs were: blood pressure 120/67 mm Hg, heart rate 127/min, respiratory rate 28/min, and temperature 97 F. After 180 mg of diazepam i.v. he remained tremulous with muscle rigidity and clenched jaws. He was intubated for airway protection and because of hypoventilation, and was paralyzed to control muscle rigidity. His subsequent course was remarkable for non-immune thrombocytopenia which resolved. The patient's maximal temperature was 101.2 F and his CPK remained < 500 units/L with no other evidence of rhabdomyolysis. His mental status normalized and he was transferred to a psychiatry ward. This patient survived without sequelae due to the aggressive sedation and neuromuscular paralysis.

Adult↗

Nothing to smile about. A cautionary tale for dentists about electronic communication.

We've all heard the adage "good news travels, but bad news travels faster." In the age of the Internet, bad news has the ability to reach millions of people in a matter or minutes. While many dentists know how to address disgruntled patients, most will never have to experience a full-fledged crisis as a result of one patient's bad experience. Dr. Rodney Shivers of Oklahoma City was the victim of a spurious e-mail smear campaign that led to his receiving thousands of harassing phone calls, threatening letters and media attention. By sharing his experience in addressing this situation, he hopes to help other dentists avoid his fate.

Child, Preschool↗

Shuddering attacks. Evaluation using electroencephalographic frequency modulation radiotelemetry and videotape monitoring.

Three children who had frequent shuddering or shivering attacks were studied using electroencephalographic frequency modulation radiotelemetry and videotape monitoring. The attacks consisted of bilateral fine tremors, sometimes associated with stiffening of the upper extremities. The attacks were not associated with any electroencephalographic abnormalities. Shuddering attacks appear to be a benign movement disorder.

Child↗

Formation of hemi-desmosomes during regeneration of crayfish nerve root sheath as studied with freeze-fracture.

The multilamellate glial sheath of mixed nerve roots of the sixth abdominal ganglion of crayfish contains numerous hemi-desmosomes which appear to attach glial lamellae to material in adjacent extracellular clefts. These junctions, which have been described in detail in an earlier report (Shivers and Brightman, '76), are irregular in shape, punctuate and may be as large as 1 mum in diameter. Surgical interruption of sixth ganglion nerve roots results in regeneration of motor axons and their multilamellate glial sheaths. As the glial processes grow and re-establish a highly organized axon sheath, hemi-desmosomes appear. These junctions are present at the advancing edge of glial processes as well as on their lateral margins. Developing hemi-desmosomes are characterized as a diffuse aggregation of 120-130 A intramembrane particles which are present three weeks following nerve section. As growth and reorganization of the sheath proceeds, the intramembrane particles appear to aggregate and form irregular clusters of varying dimensions. Regenerating nerves freeze-cleaved 8 to 16 weeks following surgery exhibit junctional particle aggregates similar to those in normal unoperated nerve roots. Origin of the intramembrane particles which comprise the junctional aggregated in unknown. Perhaps they are synthesized de novo by the regenerating glial cells or, they may be remnants of complexes which became dispersed following surgery. This is the first report of a freeze-fracture study of hemi-desmosome plasticity in an invertebrate nervous system.

Animals↗

Intercellular junctions of antennal gland epithelial cells in the crayfish, Orconectes virilis. A freeze-fracture study.

Labyrinth and nephridial canal cells of the crayfish (Orconectes virilis) antennal gland possess two types of intercellular junctions revealed by freeze-fracture studies. Apical margins of the cells are connected by long septate junctions. In replicas, these junctions consist of many parallel rows of 80--140 A intramembrane particles situated on the PF membrane face (EF and PF fracture faces of Branton et al., 1975). Rows of pits are found on the EF fracture face and are deemed complementary to the rows of particles. Moreover, lateral margins of basal regions of the epithelial cells are attached by many intercellular junctions. These contacts are characterized in thin plastic sections by a narrow dense cytoplasmic plaque located subjacent to the plasma membrane at sites of adjoined cells, and 5 to 12 fine strands of dense material that extend across the intercellular gap between adjoined cells. In freeze-fracture replicas, EF intramembrane faces basal to the region of the plasma membrane containing septate junctions exhibit numerous discoid clusters of particles. The particle aggregates, assumed to represent freeze-cleave images of adhering junctions, range from 900 to 3,700 A in diameter, with individual particles about 185 A in diameter. These junctions appear to connect epithelial cell processes formed by basal infoldings of the plasmalemma, and occur between adiacent cells as well as adiacent processes of a single cell. The discrete aggregates of particles resemble replicated desmosomes (Shienvold and Kelly, 1974) and hemi-desmosomes (Shivers, 1976); therefore, they probably do not constitute a basis for electrical coupling between antennal gland epithelial cells.

Animals↗

Responses of sympathetic nervous system to cold exposure in vibration syndrome subjects and age-matched healthy controls.

Plasma norepinephrine and epinephrine in vibration syndrome subjects and age-matched healthy controls were measured for the purpose of estimating the responsibility of the sympathetic nervous system to cold exposure. In preliminary experiment, it was confirmed that cold air exposure of the whole body was more suitable than one-hand immersion in cold water. In the main experiment, 195 subjects were examined. Sixty-five subjects had vibration syndrome with vibration-induced white finger (VWF + group) and 65 subjects had vibration syndrome without VWF (VWF- group) and 65 controls had no symptoms (control group). In the three groups, plasma norepinephrine levels increased during cold air exposure of whole body at 7 degrees +/- 1.5 degrees C. Blood pressure increased and skin temperature decreased during cold exposure. Percent increase of norepinephrine in the VWF+ group was the highest while that in VWF- group followed and that in the control group was the lowest. This whole-body response of the sympathetic nervous system to cold conditions reflected the VWF which are characteristic symptoms of vibration syndrome. Excluding the effects of shivering and a cold feeling under cold conditions, it was confirmed that the sympathetic nervous system in vibration syndrome is activated more than in the controls. These results suggest that vibration exposure to hand and arm affects the sympathetic nervous system.

Adult↗

Cyclic and non-cyclic variations of spinal cord temperature related with temperature regulation in pigeons.

1. The temperature of the spinal cord (Tvc) was measured in unanaesthetized pigeons at different ambient temperatures (Ta). 2. In short-term experiments spontaneous or noncyclic variations of Tvc at constant (20 and 10 degrees C) and changing Ta were correlated with the amplitude of the electromyogram EMG) which indicates shivering, i.e., heat production. At constant Ta no unequivocal correlation between Tvc (and also Tskin) and EMG was found. During ambient cooling there was often an increase of Tvc which resulted in a positive correlation whereas there was a negative correlation to Tskin. 3. In long-term experiments (24h, LD 12:12Y cyclic variations of Tvc were measured at different Ta and ocrrelated with O2-consumption, i.e., heat production. As with body temperature Tvc was lowered during the dark phase of the diurnal cycle. In the light phase both Tvc and heat production increased with decreasing Ta which results in a positive correlation. In the dark phase there was a smaller increase in heat production but a decrease in Tvc, i.e., a negative correlation. 4. The results show that natural variations of Tvc are often positively ocrrelated with heat production. This is in contrast to experimental changes of Tvc where a clear negative correlation to heat production can be observed.

Animals↗

Comparison in men of physiological responses to exercise of increasing intensity at low and moderate ambient temperatures.

In six male subjects the sweating thresholds, heart rate (fc), as well as the metabolic responses to exercise of different intensities [40%, 60% and 80% maximal oxygen uptake (VO2max)], were compared at ambient temperatures (Ta) of 5 degrees C (LT) and 24 degrees C (MT). Each period of exercise was preceded by a rest period at the same temperature. In LT experiments, the subjects rested until shivering occurred and in MT experiments the rest period was made to be of exactly equivalent length. Oxygen uptake (VO2) at the end of each rest period was higher in LT than MT (P less than 0.05). During 20-min exercise at 40% VO2max performed in the cold no sweating was recorded, while at higher exercise intensities sweating occurred at similar rectal temperatures (Tre) but at lower mean skin (Tsk) and mean body temperatures (Tb) in LT than MT experiments (P less than 0.001). The exercise induced VO2 increase was greater only at the end of the light (40% VO2max) exercise in the cold in comparison with MT (P less than 0.001). Both fc and blood lactate concentration [1a]b were lower at the end of LT than MT for moderate (60% VO2max) and heavy (80% VO2max) exercises. It was concluded that the sweating threshold during exercise in the cold environment had shifted towards lower Tb and Tsk. It was also found that subjects exposed to cold possessed a potentially greater ability to exercise at moderate and high intensities than those at 24 degrees C since the increases in Tre, fc and [1a]b were lower at the lower Ta.

Adolescent↗

Increase in oxygen consumption induced by selective spinal cord cooling in the exercising pigeon.

Six domestic pigeons with chronically implanted spinal thermodes were exercised on a treadmill at neutral ambient temperature. During the exercise the spinal cord was cooled to 34.7 +/- 0.4 degrees C (mean +/- S.E.M.). Oxygen consumption of the pigeons increased from 28.3 +/- 2.1 to 61.2 +/- 3.7 ml X min-1 X kg-1 due to exercise per se, and superimposed cooling of the spinal cord during exercise induced an additional increase in oxygen consumption to 84.9 +/- 4.5 ml X min-1 X kg-1. The result demonstrates that cooling of the spinal cord elicits shivering in exercising pigeons at thermoneutral conditions.

Animals↗

Seasonal variations in rectal temperature of Yankasa sheep.

From measurements of rectal temperature (Tre) at 06:00h (06:00Tre) and at 14:00h (14:00Tre), meteorological stress was determined in six Yankasa ewes in terms of per cent rise of 14:00Tre over 06:00Tre reference values during the harmattan and hot-dry seasons. Absolute and mean Tre values were significantly higher (P less than 0.05) during the harmattan than the hot-dry season. In both seasons, mean 14:00Tre was significantly higher (P less than 0.01) than 06:00Tre. The mean diurnal difference between 14:00Tre and 06:00Tre, i.e. delta Tre was about 1 degrees C during the harmattan but ranged between 0.5 and 0.7 degrees C during the hot-dry season. All animals were observed to shiver during harmattan nights.

Animals↗

Prediction of the thermoregulatory response for clothed immersion in cold water.

A multi-compartmental thermoregulatory model was applied to data of ten resting clothed males immersed for 3 h in water at 10 and 15 degrees C. Clothing consisted of a dry suit and either a light or heavy undergarment, representing a total insulation of 0.15 (0.95) or 0.20 m2 degrees CW-1 (1.28 clo), respectively. Data were grouped according to low (less than 14%) and high (14 to 24%) body fat individuals. Mean decreases in rectal temperature ranged from 0.79 to 1.38 degrees C, mean decreases in the mean weighted skin temperature ranged from 6.3 to 10.2 degrees C, and mean increases in the metabolic rate ranged from 33.9 to 80.8 W. The model consists of eight segments, each representing a specific region of the body. Each segment is comprised of compartments representing the core, muscle, fat, skin, and clothing. Each compartment is assigned thermophysical values of heat conduction and heat capacitance, and with the exception of clothing, physiological values of blood flow and metabolic heat production. During cold exposure, responses are directed towards increased heat production in the form of shivering and heat conservation in the form of vasoconstriction and convective heat exchange at the vascular level. Agreement between the model predictions and the experimental observations was obtained by adjusting the parameters governing these responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗