Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in hypothermic humans

Giesbrecht, Gordon G.; Goheen, M. S. L.; Johnston, Chad E.; Kenny, Glen P.; Bristow, Gerald K.; Hayward, J. S.

doi:10.1152/jappl.1997.83.5.1630

Cited by 61 publications

(53 citation statements)

References 16 publications

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“…Cutaneous heat flux (W/m 2 ) and skin temperature (°C) were measured from 12 sites (listed below) using thermal flux transducers (Concept Engineering, Old Saybrook, CT) according to our laboratory's standard procedures (11). BSA was calculated as follows: area (m 2 ) ϭ weight 0.425 (kg) ⅐ height 0.725 (cm) ⅐ 0.007184.…”

Section: Instrumentationmentioning

confidence: 99%

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Thermal effects of whole head submersion in cold water on nonshivering humans

Pretorius

Bristow²,

Steinman³

et al. 2006

Journal of Applied Physiology

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. Thermal effects of whole head submersion in cold water on nonshivering humans. J Appl Physiol 101: 669 -675, 2006. First published April 13, 2006; doi:10.1152/japplphysiol.01241.2005This study isolated the effect of whole head submersion in cold water, on surface heat loss and body core cooling, when the confounding effect of shivering heat production was pharmacologically eliminated. Eight healthy male subjects were studied in 17°C water under four conditions: the body was either insulated or uninsulated, with the head either above the water or completely submersed in each body-insulation subcondition. Shivering was abolished with buspirone (30 mg) and meperidine (2.5 mg/kg), and subjects breathed compressed air throughout all trials. Over the first 30 min of immersion, exposure of the head increased core cooling both in the body-insulated conditions (head out: 0.47 Ϯ 0.2°C, head in: 0.77 Ϯ 0.2°C; P Ͻ 0.05) and the body-exposed conditions (head out: 0.84 Ϯ 0.2°C and head in: 1.17 Ϯ 0.5°C; P Ͻ 0.02). Submersion of the head (7% of the body surface area) in the body-exposed conditions increased total heat loss by only 10%. In both body-exposed and body-insulated conditions, head submersion increased core cooling rate much more (average of 42%) than it increased total heat loss. This may be explained by a redistribution of blood flow in response to stimulation of thermosensitive and/or trigeminal receptors in the scalp, neck and face, where a given amount of heat loss would have a greater cooling effect on a smaller perfused body mass. In 17°C water, the head does not contribute relatively more than the rest of the body to surface heat loss; however, a cold-induced reduction of perfused body mass may allow this small increase in heat loss to cause a relatively larger cooling of the body core.hypothermia; heat loss; submersion; perfused body mass; thermal model; symptomless hypothermia; thermal core; cold-water near drowning MANY RECREATIONAL, COMMERCIAL, and military activities involve cold water and the possible development of accidental hypothermia. Several studies (6,11,14,21) have addressed the effect of cold-water immersion on the rate of body core cooling. The initiation and degree of hypothermia are related to many variables, including water temperature, insulation, duration of exposure, and the amount of body surface area (BSA) exposed to the water. The effect of whole head cold-water submersion on core cooling is unknown.One hypothesis predicts a substantial heat loss through the head due to the great amount of surface blood flow in the scalp and because scalp blood vessels do not vasoconstrict in response to cold as do surface vessels in other body areas (8). An alternative hypothesis predicts minimal heat loss from the head because submersion of the head and neck would only involve 7-9% more of the body surface area (20). As well, mathematical modeling predicts minimal conductive heat loss directly through the scalp and skull (27). This topic has important practical implications for conditions where th...

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Section: Instrumentationmentioning

confidence: 99%

“…Several studies (6,11,14,21) have addressed the effect of cold-water immersion on the rate of body core cooling. The initiation and degree of hypothermia are related to many variables, including water temperature, insulation, duration of exposure, and the amount of body surface area (BSA) exposed to the water.…”

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Thermal effects of whole head submersion in cold water on nonshivering humans

Pretorius

Bristow²,

Steinman³

et al. 2006

Journal of Applied Physiology

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“…È più efficace del riscaldamento passivo, permettendo di aumentare la temperatura di 1-2,5 gradi ora [42][43][44] . La precauzione da tenere è quella di riscaldare il tronco e non le estremità, per evitare il fenomeno dell'afterdrop 45,46 . Questo fenomeno può essere evitato con la somministrazione di liquidi caldi.…”

Section: Riscaldamento Esterno Attivounclassified

Accidental hypothermia

Casagranda

Lombardi²,

Turchetti³

et al. 2006

Emerg Care J

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Nel mese di dicembre 2002 un giovane di 23 anni viene coinvolto in un incidente stradale sul ponte del fiume Tanaro, nella città di Alessandria. Questi, una volta sceso indenne dalla macchina, per evitare di essere investito da un'altra automobile finisce accidentalmente, alle ore 6.15, nell'acqua del fiume, la cui temperatura è di 5,1 °C mentre quella dell'aria è 1,5 °C. Viene trovato, nudo, dai vigili del fuoco verso le ore 7.45 sulla riva a circa 500 metri dal luogo della caduta, in apparente arresto cardiaco. L'équipe del 118 con il medico a bordo, giunta sul posto, conferma la diagnosi di arresto cardiaco in asistolia/FV a onde fini. Il paziente viene intubato per via orotracheale, massaggiato e ventilato. Vengono incannulate due vene periferiche con un cateterino da 16 F. Sul posto viene defibrillato per 3 volte a 300 J e altre 3 a 360 J. Durante il tentativo di rianimazione vengono praticate 6 fiale di adrenalina, 1 fiala di atropina e 250 cc di soluzione glucosata al 5%. Visti i tentativi infruttuosi di rianimazione, si decide di trasportare il paziente presso il DEA di II livello, distante circa 8 chilometri dal luogo dell'evento, continuando durante il percorso la rianimazione cardiopolmonare (RCP). Arriva in Pronto Soccorso verso le 8.10 dove continua il supporto delle funzioni vitali. La misurazione della temperatura timpanica evidenzia valori al di sotto dei 30 °C. Nel frattempo si allerta l'équipe cardiochirurgica per il riscaldamento in circolazione extra-corporea (CEC). In attesa del trasferimento in sala operatoria, il paziente viene portato in rianimazione dove si misura la temperatura vescicale, che è 28,5 °C. L'emogasanalisi arteriosa evidenzia pH 6,81, PaO 2 110 mmHg, PaCO 2 48 mmHg, HCO 3 7,9 mEq/l, lattato 26,5 mmd/l. Persiste asistolia. Durante la permanenza in rianimazione vengono somministrati thiopentone 1 g, idrocortisone 2 g, bicarbonato di sodio 400 mEq e si applica pacing esterno. Il riscaldamento viene effettuato con ventilazione in ossigeno 100% umidificato a 42 °C, con soluzione salina 0,9% riscaldata a 42 °C e con dispositivo di riscaldamento corporeo ad aria calda. Alle ore 10.15 viene portato in sala operatoria di cardiochirurgia, sempre in asistolia, dopo 150 minuti di massaggio cardiaco esterno (MCE) mai interrotto, con una temperatura di 27,3 °C. Alle 10.48 viene eseguita sternotomia mediana e si collega il paziente alla macchina cuore-polmone mediante il posizionamento di una cannula aortica in aorta ascendente, di una cannula venosa in atrio destro e di uno scarico sinistro in vena polmonare superiore destra dopo eparinizzazione sistemica. Durante le manovre di collegamento il cuore viene massaggiato direttamente. Il flusso di perfusione sistemica è di 2,4 l/min/m 2 con un gradiente di riscaldamento che non supera i 10 °C. Alle 11.46 l'emogasanalisi di controllo evidenzia pH 7,29, PaO 2 221 mmHg, PaCO 2 39,7 mmHg, HCO 3 18,8 mEq/l, Anion Gap 30 mEq/l, lattato 24 mmd/l, glucosio 333 mg/dl, K 2,5 mEq/l, Na 152 mEq/l, Ca ++ 2,29 mEq/l, Cl -103 mEq/l. Alle 13.30, raggiunta l...

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“…As well, a mildly hypothermic, vigorously shivering individual rewarms at a rate of 3-4˚C/hr (25). Inhibition of shivering results in a greater post-cooling fall in the core temperature (T c; afterdrop) and a reduction in the rate of rewarming (26). As shivering heat production can effectively rewarm a mildly hypothermic individual, application of external heat is not necessary but may still be beneficial as it helps conserve energy stores and decreases work of the heart.…”

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Comparison of Heat Donation Through the Head or Torso on Mild Hypothermia Rewarming

Sran

McDonald

Steinman

et al. 2014

Wilderness & Environmental Medicine

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This study compared head vs. torso warming using a similar source of heat donation. Six subjects were cooled in 8˚C water to either a core temperature of 35˚C or for 60 min. They were then rewarmed by either shivering only, or charcoal heater applied to the head, or torso. There were no significant differences in rewarming rate between the three conditions. Head warming did not inhibit average shivering heat production resulting in greater net heat gain during 35-60 min of rewarming compared to shivering. Head warming is as effective as torso warming for hypothermic victims.Head warming could be a preferred method in some cases: extreme conditions in which removal of the insulation and exposure of the torso to the cold is contraindicated; excessive movement is contraindicated (e.g., severe hypothermia which has a risk of ventricular fibrillation, or potential spinal injury); or if emergency personnel are working on the torso.iii ACKNOWLEDGEMENTS

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Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in hypothermic humans

Cited by 61 publications

References 16 publications

Thermal effects of whole head submersion in cold water on nonshivering humans

Thermal effects of whole head submersion in cold water on nonshivering humans

Accidental hypothermia

Comparison of Heat Donation Through the Head or Torso on Mild Hypothermia Rewarming

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