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PubMed2005

Thermal effects of dorsal head immersion in cold water on nonshivering humans.

Personal floatation devices maintain either a semirecumbent flotation posture with the head and upper chest out of the water or a horizontal flotation posture with the dorsal head and whole body immersed. The contribution of dorsal head and upper chest immersion to core cooling in cold water was isolated when the confounding effect of shivering heat production was inhibited with meperidine (Demerol, 2.5 mg/kg). Six male volunteers were immersed four times for up to 60 min, or until esophageal temperature = 34 degrees C. An insulated hoodless dry suit or two different personal floatation devices were used to create four conditions: 1) body insulated, head out; 2) body insulated, dorsal head immersed; 3) body exposed, head (and upper chest) out; and 4) body exposed, dorsal head (and upper chest) immersed. When the body was insulated, dorsal head immersion did not affect core cooling rate (1.1 degrees C/h) compared with head-out conditions (0.7 degrees C/h). When the body was exposed, however, the rate of core cooling increased by 40% from 3.6 degrees C/h with the head out to 5.0 degrees C/h with the dorsal head and upper chest immersed (P < 0.01). Heat loss from the dorsal head and upper chest was approximately proportional to the extra surface area that was immersed (approximately 10%). The exaggerated core cooling during dorsal head immersion (40% increase) may result from the extra heat loss affecting a smaller thermal core due to intense thermal stimulation of the body and head and resultant peripheral vasoconstriction. Dorsal head and upper chest immersion in cold water increases the rate of core cooling and decreases potential survival time.

Adult↗
PubMed2006

Contribution of thermal and nonthermal factors to the regulation of body temperature in humans.

The set point has been used to define the regulated level of body temperature, suggesting that displacements of core temperature from the set point initiate heat production (HP) and heat loss (HL) responses. Human and animal experiments have demonstrated that the responses of sweating and shivering do not coincide at a set point but rather establish a thermoeffector threshold zone. Neurophysiological studies have demonstrated that the sensor-to-effector pathways for HP and HL overlap and, in fact, mutually inhibit each other. This reciprocal inhibition theory, presumably reflecting the manner in which thermal factors contribute to homeothermy in humans, does not incorporate the effect of nonthermal factors on temperature regulation. The present review examines the actions of these nonthermal factors within the context of neuronal models of temperature regulation, suggesting that examination of these factors may provide further insights into the nature of temperature regulation. It is concluded that, although there is no evidence to doubt the existence of the HP and HL pathways reciprocally inhibiting one another, it appears that such a mechanism is of little consequence when comparing the effects of nonthermal factors on the thermoregulatory system, since most of these factors seem to exert their influence in the region after the reciprocal cross-inhibition. At any given moment, both thermal and several nonthermal factors will be acting on the thermoregulatory system. It may, therefore, not be appropriate to dismiss the contribution of either when discussing the regulation of body temperature in humans.

Autonomic Nervous System↗
PubMed1986

Reduction of heat loss during transurethral resection of the prostate.

A prospective trial was performed on 100 patients to determine whether using a reflective blanket (Space Blanket) and heated glycine 1.5% bladder irrigation solution would decrease the fall in body temperature associated with transurethral resection of the prostate under spinal anaesthesia. Patients who received a combination of reflective blanket and heated glycine 1.5% solution had their fall in body temperature significantly reduced when compared with those patients managed without a reflective blanket and/or heated 1.5% glycine. There was a marked decrease in the number of patients shivering and no increase in blood loss was seen when heated bladder irrigation solution was used.

Age Factors↗
PubMed1988

Epidural anaesthesia for caesarean section: a comparison of 0.5% bupivacaine and 2% lignocaine both with adrenaline.

Thirty-eight women having caesarean section under epidural anaesthesia received either lignocaine 2% or bupivacaine 0.5% both with adrenaline 1:200,000 in a double-blind, randomised study. The time to establish satisfactory surgical anaesthesia, the volume required and the quality of analgesia as assessed by the anaesthetist, patient pain and discomfort scales and patient approval, were not significantly different. Motor block assessed by the Bromage and RAM-test was greater in the lignocaine group but surgical opinion of abdominal wall relaxation was not significantly different between groups. The bupivacaine group had significantly longer durations of sensory and motor block while the lignocaine group had a higher incidence of maternal shivering, other complication rates being similar. Neonatal outcomes were uniformly good. Both local anaesthetics provided satisfactory epidural anaesthesia and neither proved to have a distinct advantage in the clinical setting of this study.

Adult↗
PubMed1980

Neurologic prognosis after cardiopulmonary arrest: III. Seizure activity.

Nineteen (30%) of 63 adult survivors of cardiopulmonary arrest had seizures after admission to the hospital. Eleven of 19 had more than one type of seizure. Myoclonic seizures began within 12 hours of the arrest in eight patients, and after 3 or more days in four patients. Only two (17%) patients with myoclonic seizures survived. Partial seizures usually began within 12 hours of the arrest and were controllable with anticonvulsants; 4 of 12 patients survived. Two of four patients with generalized tonic-clonic seizures survived; one of four with "shivering" lived. Overall, patients with seizures had a survival rate of 32% (6 of 19), compared with 43% for patients without seizures. None of the survivors had recurrent seizures within 6 months after hospital admission.

Adult↗
PubMed2003

Endothermic heat production in honeybee winter clusters.

In order to survive cold northern winters, honeybees crowd tightly together in a winter cluster. Present models of winter cluster thermoregulation consider the insulation by the tightly packed mantle bees as the decisive factor for survival at low temperatures, mostly ignoring the possibility of endothermic heat production. We provide here direct evidence of endothermic heat production by 'shivering' thermogenesis. The abundance of endothermic bees is highest in the core and decreases towards the surface. This shows that core bees play an active role in thermal control of winter clusters. We conclude that regulation of both the insulation by the mantle bees and endothermic heat production by the inner bees is necessary to achieve thermal stability in a winter cluster.

Acclimatization↗
PubMed1995

Changes in the behavioral parameters following the lipopolysaccharide administration in goats.

The present study was aimed at the establishment of an experimental model for the numerical assessment of sick animal behavior. Four goats were given bolus injections of 200 ng/kg of lipopolysaccharide (LPS) or vehicle (0 hr) under non-restrained conditions, and observed for behavioral changes and clinical symptoms during the period between -1 and 10 hr. The apparent clinical symptoms of miosis and shivering were observed during the period from 39.5 +/- 3.1 to 296.5 +/- 9.9 min and from 46.0 +/- 2.3 to 251.0 +/- 15.5 min after the LPS administration, respectively. As to the general behaviors, the total length for standing and sternum lying during the period from 0 to 5 hr after LPS administration showed no change, however, that for feeding and rumination, and the cumulative number of grooming episode were significantly reduced as compared to the control period. On the other hand, the cumulative numbers of urination, defecation and yawning showed a tendency to increase but not significantly. These results suggest that stereotyped behavioral responses, which are typically seen in acute phase of sickness, can be transiently induced in goats by treating them with LPS.

Animals↗
PubMed2004

Achieving normothermia in patients with febrile subarachnoid hemorrhage: feasibility and safety of a novel intravascular cooling catheter.

INTRODUCTION: Fever is common and difficult to control in patients with subarachnoid hemorrhage (SAH). We have previously shown an inverse relationship between fever and outcome in patients with SAH. MATERIALS/METHODS: This was a prospective, single-arm, feasibility trial in which nine patients with SAH underwent temperature management using an intravascular cooling catheter (ICC) to restore and maintain 24 hours of normothermia (36.5 degrees+/-0.2 degrees C). Enrollment occurred after development of a fever of at least 38.3 degrees C within 7 days of SAH that was refractory to acetaminophen treatment. The ICC was placed at the bedside through an introducer sheath via the femoral vein into the inferior vena cava (IVC). Portable X-ray confirmed placement. RESULTS: Normothermia was achieved in seven of the nine patients treated (78%); it was achieved in 100% of the patients with a 14F catheter (n=4) and in 60% of the patients with a 9F catheter (n=5). The two patients not reaching normothermia were not adequately treated for shivering. All other patients reached normothermia irrespective of intubation status. Overall, normothermia was well tolerated and not discontinued because of discomfort or adverse events. Two incidences of deep vein thrombosis were diagnosis by ultrasound that were not associated with clinical sequelae, and IVC filters were placed. No unanticipated adverse events occurred. DISCUSSION: We have demonstrated that fever can be safely and effectively controlled in patients with SAH for at least 24 hours using an ICC. Future studies are needed to assess the effect of such sustained therapy on outcome in patients with SAH.

Adult↗
PubMed2004

Physiology and clinical relevance of induced hypothermia.

Experimental evidence and clinical experience suggest that mild hypothermia protects numerous tissues from damage during ischemic insult. However, the extent to which hypothermia becomes a valued therapeutic option will depend on the clinician's ability to rapidly reduce core body temperature and safely maintain hypothermia. To date, general anesthesia is the best way to block autonomic defenses during induction of mild-to-moderate hypothermia; unfortunately, general anesthesia is not an option in most patients likely to benefit from therapeutic hypothermia. Induction of hypothermia in awake humans is complicated by both the technical difficulties related to thermal manipulation and the remarkable efficacy of thermoregulatory defenses, especially vasoconstriction and shivering. The most effective thermal manipulation devices are generally invasive and, therefore, more prone to complications than surface methods. In an effort to inhibit thermoregulation in awake humans, several agents have been tested either alone or in combination with each other. For example, the combination of meperidine and buspirone has already been applied to facilitate induction of hypothermia in human trials. However, pharmacological induction of thermoregulatory tolerance to cold without excessive sedation, respiratory depression, or other serious toxicity remains a major focus of current therapeutic hypothermia research.

Anesthetics↗
PubMed1985

Lasting consistency of cold adaptability in rats reared in cold for many generations.

Wistar rats were successively reared in cold at 5 degrees C from 1969 to 1984. The historical changes observed in these rats were reported. The cold-adapted rats reared in cold for 8 to 11 successive generations (C8-11G) were examined on their cold tolerance and non-shivering thermogenesis. C8-11G rats showed greater nonshivering thermogenesis than that of the warm-adapted control group (W), and rats exposed to cold for periods of 2 to 8 weeks (C). The nonshivering thermogenesis of C8-11G rats was diminished to a similar level to that of W and C rats by administration of a ganglion blocker, of reserpine, or of beta-adrenoceptor blocker. The de-adapted rats reared in warm at 25 degrees C for 3 generations after being reared for many generations in cold (DA-3G) showed much more nonshivering thermogenesis as compared to W rats. Cold tolerance of DA-3G rats was at a level of intermediate between that of W and C rats. Brown adipose tissue (BAT) weight of DA-3G rats was similar to that of C rats, while chemical composition of BAT in DA-3G rats differed from that of C and W rats.

Adaptation, Physiological↗
PubMed1982

The effect of intracerebroventricular infusion of morphine, methionine-enkephalin and D-Ala2-enkephalinamide on body temperature of rabbits.

The effect of intracerebroventricular infusions of two synthetically obtained peptides: Met-enkephalin hydrochloride and D-Ala2-Met-enkephalinamide hydrochloride, and of morphine hydrochloride on rectal temperature was investigated in conscious rabbits. Morphine hydrochloride in a dose of 240 micrograms and D-Ala2-Met-enkephalinamide hydrochloride in doses of 240 and 3000 micrograms produced a hyperthermia which was accompanied by ear vasoconstriction and shivering. No such effect ensued after Met-enkephalin, possibly due to rapid enzymatic degradation of this compound. The concept of opioid involvement in the central thermoregulatory mechanism is discussed.

Animals↗
PubMed2003

[Stimulation of thermoregulatory and respiratory functions with the help of EDTA and EGTA during deep hypothermia in rats].

Influence of EDTA (C10H14N2Na2O8.2H2O) and EGTA (C14H24N2O10) on physiological functions homoiothermic organisms at deep hypothermia, was studied. White rats during cooling were in special sections without rigid fixing of head and limbs. In reply to intravenous introduction of EDTA and EGTA solutions, similar answers of the organisms were observed: raised breathing frequency and amplitude, intensity of electrical activity of muscles; these signs of activation of physiological functions lasted 8-10 minutes. Besides, of the 20th-30th minute after introduction of the second dose of preparations (at rectal temperature 17.1 +/- 0.5 degrees C), the secondary activation respiratory and thermoregulatory functions were registered. The termination of the cold shivering in experiments with introduction of EDTA and EGTA solutions occurred at lower temperatures in rectum and in a brain (16.7-17.3 degrees and 17.8-18.2 degrees C, resp.) than in control experiments (18.7 +/- 0.6 degrees C and 20.2 +/- 1.5 degrees C). The authors suppose that the activation of the thermoregulatory and respiratory functions is caused by a decrease in concentration of ions Ca2+ in the blood plasma.

Animals↗
PubMed2004

[Intravenous fluid administration and management of body temperature].

Hypothermia occurs due to body heat redistribution between core and peripheral tissues as well as imbalance between heat loss and production. Perioperative hypothermia not only induces offensive shivering and prolongation of anesthetic recovery but also increases blood loss and incidence of surgical wound infection, increasing postoperative morbidity. It has been shown that intraoperative intravenous fluid administration and blood product transfusion have considerable effects on body temperature. Thus, it is important to monitor and control the temperature of fluids. Anesthesiologists should have knowledge of the characteristics of the various kinds of fluid warmer currently available and use them appropriately according to surgical procedures and the patient's position. It was reported recently that administration of amino acid can prevent intraoperative hypothermia, possibly by increasing the heat production in the body.

Amino Acids↗
PubMed2006

CNS toxicity in closed-circuit oxygen diving: symptoms reported from 2527 dives.

INTRODUCTION: Oxygen toxicity is a problem in diving and can have fatal consequences in the water. Various aspects of oxygen diving have been studied in dry hyperbaric chambers, but there is a lack of information on in-water diving using closed-circuit oxygen apparatus. METHOD: We collected 2527 dive reports from 473 closed-circuit oxygen divers (a mean of 5.2 reports per diver), and analyzed the relationships between various symptoms and their dependence on depth and diving time. RESULTS: No CNS oxygen toxicity-related symptoms were reported at a depth of 2 m seawater (msw), but their proportion increased at depths from 3 to 6 msw. We found that CNS oxygen toxicity-related symptoms appeared in 2.5% of dives conducted at a Po2 of 119 kPa. The main symptoms and signs reported were headache: 4.5%; nausea: 2.6%; hyperventilation: 2.6%; heavy breathing: 2.4%; dizziness: 1.6%; hiccups: 1.5%; bloody sputum: 1.4%; cold shivering: 1.1%; tinnitus: 0.9%; difficulty maintaining a steady depth: 0.9%; disorientation: 0.6%; tiredness: 0.5%; tingling in the limbs: 0.4%; hearing disturbances: 0.4%; a choking sensation: 0.4%; extreme effort: 0.4%; and loss of consciousness: 0.3%. DISCUSSION: Environmental factors, light vs. dark and temperature, had no effect on symptoms. The number of symptoms increased with diving time. Divers who experienced amnesia, facial twitching, hearing disturbances (p < 0.001), and disorientation (p < 0.014) were prone to suffer loss of consciousness. It was found that some divers are more sensitive to oxygen than others (p < 0.0001).

Airway Obstruction↗