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Performing in cold environments
Published in R. C. Richard Davison, Paul M. Smith, James Hopker, Michael J. Price, Florentina Hettinga, Garry Tew, Lindsay Bottoms, Sport and Exercise Physiology Testing Guidelines: Volume I – Sport Testing, 2022
Clare Eglin, Michael Tipton, Heather Massey
Falling Tsk and Tcore will initiate shivering, and whilst exercise often inhibits shivering, in severe conditions they can occur simultaneously up to a moderate level of exercise (oxygen consumption of 1.2 L.min−1) (Whyte and Tipton, 2020). Maximal shivering is approximately 50% of maximal oxygen uptake and therefore can be assessed by measuring oxygen consumption (no correction is required for mechanical efficiency since shivering is 0% efficient). Electromyography (EMG; common sites: pectoralis major, trapezius, sternocleidomastoid and deltoideus) is useful for identifying the onset of shivering, but there are inter-individual variations in the order of muscle recruitment, and activation of deeper muscles is not measured. Shivering can also be assessed visually, for example, using the bedside shivering assessment scale (see supplementary material). It is recommended that shivering is assessed using a combination of techniques.
Selected topics
Published in Henry J. Woodford, Essential Geriatrics, 2022
Thermoregulation becomes impaired as a consequence of frailty. Dysfunction of multiple physiological systems can contribute to this. Average core body temperature is estimated to be 0.4°C lower in older people compared to younger people.55 Core bodily temperature is a balance between heat creation from metabolism and heat loss from the skin, including evaporation of sweat. Blood flow to the skin is a key process in thermoregulation. The abilities to vasodilate and vasoconstrict are impaired in older people, making them more susceptible to hypothermia in cold conditions and overheating in hot settings. This is probably mediated by a reduction in sympathetic nervous system activity. Sweat production can be reduced when blood flow to the skin is impaired or with dehydration. Heat production is proportional to muscle mass, which declines with sarcopenia. Reduced activity can also result in less heat generation. There may be a reduced shivering response to hypothermia. Insulating fat conserves heat. There is a reduction in the subcutaneous fat layer in old age. Brown adipose tissue is important for thermogenesis in new-borns but probably not in adults. An underactive thyroid gland is a possible additional factor. Peripheral thermosensor receptors and central brain processing can be impaired in older age. There may also be cognitive aspects, such as wearing the appropriate clothing and home heating. Figure 22.1 summarises the aspects that promote hypothermia in frail older people. Paradoxical undressing can occur with hypothermia.56
Disorders of Consciousness
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Targeted temperature management (TTM) to 32–36°C for at least 24 hours in comatose survivors of cardiac arrest may improve neurologic outcome. The benefit was first demonstrated in patients with out-of-hospital cardiac arrest (OHCA) with a shockable cardiac rhythm, and TTM to 36°C was ultimately shown to be as effective as 33°C in this population.17–19 The evidence supporting TTM after in-hospital cardiac arrest and in patients with nonshockable rhythm is growing and supported by several societal guidelines.20,21 Induction of hypothermia can be instituted with IV ice-cold fluids or ice packs on the groin, armpits, neck, and head. Surface or IV cooling devices can also be used. Maintenance of hypothermia is best achieved with external or internal cooling devices with continuous temperature feedback to achieve the desired target temperature. Slow rewarming at 0.25–0.5°C per hour is recommended. Shivering can be treated with sedation and neuromuscular blockade.
Out-of-Hospital Cold Water Immersion for Classic (Non-Exertional) Heat Stroke Guided by Real-Time Core Temperature Monitoring: A Case Series
Published in Prehospital Emergency Care, 2023
Ryan C. Jacobsen, Bryan Beaver, Benjamin Abo
The patient was moved to a cooling bag and the facility provided a bucket of ice and a bucket of water that was poured onto patient while awaiting fire apparatus to access a hydrant. The patient’s clothes were also removed. Once the engine arrived a 2.5-inch hose line was placed in the cooling bag for cold-water immersion. The patient had real-time rectal core monitoring during the procedure. The patient was cooled on-scene until goal temperature was achieved. Shivering occurred at one point but ceased upon stopping cold-water immersion and required no medications or interventions. EMS performed cold-water immersion for 32 minutes and had an overall scene interval of 38 minutes. On arrival to the hospital after a 7-minute transport interval, the patient had a normal temperature, and his GCS score had improved to 15.
Circadian rhythmicity of body temperature and metabolism
Published in Temperature, 2020
Birds and mammals can increase metabolic heat production when exposed to a cold environment, and this is called cold-induced thermogenesis. Shivering is one form of cold-induced thermogenesis. It is a widespread mechanism of thermogenesis used to prevent the fall of body temperature in a cold environment. It consists of small-amplitude, high-frequency contractions of skeletal muscles. It is employed both by birds [382,392,525–531] and by mammals [532–547], including humans [548–550]. Forms of biological thermogenesis other than shivering are collectively called non-shivering thermogenesis. Birds seem to rely primarily on shivering and, if they exhibit thermoregulatory non-shivering thermogenesis, the muscles themselves are the probable source [392,528–530,551-554]. Mammals, on the other hand, use non-shivering thermogenesis extensively in response to cold stress, and the capacity to use it is strongly affected by acclimation or acclimatization [534,540–543,546,555–578]. Mammalian thermoregulatory non-shivering thermogenesis often relies on the activation of a specialized tissue, brown adipose tissue [579,580].
Pre- and peripartal management of a woman with McArdle disease: a case report
Published in Gynecological Endocrinology, 2018
Tina Stopp, Michael Feichtinger, Wolfgang Eppel, Thomas M. Stulnig, Peter Husslein, Christian Göbl
When anesthesia is planned special precautions have to be taken into consideration. Patients with McArdle disease seem to have a higher susceptibility for the development of malignant hyperthermia, although evidence is weak [18,19]. Nevertheless, trigger substances such as volatile inhalational agents should therefore be avoided. McArdle patients may not be given depolarizing muscle relaxants in case general anesthesia with Rapid Sequence Induction is required, as those substances are known to trigger rhabdomyolysis and malignant hyperthermia as well [3]. The use of tourniquets and compression stockings should be carefully monitored as some cases of acute compartment syndrome, possibly worsened by the use of compressing aids, have been described [11]. Any shivering should also be avoided by maintaining normothermia [19].