Reduced cerebral perfusion on sudden immersion in ice water: A possible cause of drowning

Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, Copenhagen, Denmark.
Aviation Space and Environmental Medicine (Impact Factor: 0.88). 05/2007; 78(4):374-6.
Source: PubMed


Near-drowning incidents and drowning deaths after accidental immersion in open waters have been linked to cold shock response. It consists of inspiratory gasps, hyperventilation, tachycardia, and hypertension in the first 2-3 min of cold-water immersion. This study explored the immediate changes in cerebral blood flow velocity (Vmean) during cold-water immersion since cold shock induced hyperventilation may diminish Vmean and lead to syncope and drowning.
There were 13 male volunteers who were lowered into a 0 degrees C immersion tank for 30 s. Vmean in the middle cerebral artery (MCA) was measured together with ventilatory parameters and heart rate before, during, and after immersion.
Within seconds after immersion in ice water, heart rate increased from 74 +/- 16 to 107 +/- 18 bpm (mean +/- SD; p < 0.05). Immersion was associated with a marked elevation in respiratory rate (from 16 +/- 3 to 38 +/- 14 breaths x min(-1)) and tidal volume (883 +/- 360 to 2292 +/- 689 ml). The end-tidal carbon dioxide tension decreased from 38 +/- 4 to 26 +/- 5 mmHg and MCA Vmean dropped by 43 +/- 8%. Signs of imminent syncope (drowsiness, blurred vision, loss of responsiveness) were shown by two subjects (MCA Vmean dropped 62% and 68%, respectively).
Following ice-water immersion, hyperventilation induced a marked reduction in MCA Vmean to a level which has been associated with disorientation and loss of consciousness.

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    • "An important, yet less examined element of cold shock is the effect that hyperventilation-induced hypocapnia has on cerebral perfusion and how this may affect behaviour. Mantoni et al. [5] reported that cerebral blood flow dropped by 43% following a 30-s immersion in 0 °C ice water and resulted in symptoms of imminent syncope (i.e., drowsiness, blurred vision, loss of responsiveness) for those with the greatest drop (N60%), likely as a consequence of the severe cerebral hypoperfusion [7]. Whilst Datta and Tipton [8] have also reported reduced cerebral blood flow (CBF) during 12 °C water immersion (CBF down 25%), no study to date has included physical activity (e.g., treading water) during the cold-water immersion or examined the initial response (i.e., b 60 s) during realistic sudden immersion conditions . "
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    ABSTRACT: We examined the initial physiological responses and subsequent capacity to swim following cold-water immersion. An ecologically-valid model was used whereby immersion was sudden (<2s) and participants had to actively remain afloat. Participants (15 skilled swimmers, 17 less-skilled swimmers) undertook four experimental test sessions: a physiological test and a swimming test in both cold (10°C) water and temperate (27°C) water in a swimming flume (temperature order counter-balanced). For physiological testing, measures of brain perfusion [flow velocity (MCAv, Doppler) and oxygenation (NIRS)] and cardiorespiratory function [ventilation parameters and end-tidal PCO2 (PETCO2)] were recorded whilst treading water for 150s. The swimming test involved treading water (150s) before swimming at 60% (up to 120s) and 90% (to intolerance) of pre-determined maximum velocity. Multifactorial analysis revealed that swimming duration was influenced most heavily by water temperature, followed by respiratory variables and MCAv in the first 30s of immersion. The time course and severity of cold shock were similar in both groups (p=0.99), in terms of initial physiological changes (MCAv down ~20±11%, respiratory frequency increased to 58±18 breaths·min(-1), PETCO2 dropped to 12±9mmHg). Treading water following cold-water immersion increased MCAv by 30% above resting values despite maintained cold-shock-induced hyperventilation. In comparison to temperate water, swimming capacity was also reduced similarly between groups in the cold (i.e., distance decreased by 34±26% skilled; 41±33% less-skilled, p=0.99). These integrative findings verify that sudden cold-water immersion followed by physical activity leads to similar physiological responses in humans when contrasting between skilled and less-skilled swimmers. Copyright © 2014. Published by Elsevier Inc.
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    • "Caution is therefore warranted by athletes and coaches prior to implementing CWI. Potentially hazardous physiological effects that have been reported following the immersion of a significant proportion of the body in cold water include, hyperventilation leading to the development of metabolic alkalosis (Keatinge & Evans, 1961; Golden & Tipton, 2002), decreased cerebral blood flow (Mantoni et al. 2007; Tipton et al. 2000) (both of which can lead to dizziness and unconsciousness), increased blood pressure, and the development of abnormal cardiac rhythms in some individuals (Keatinge & Evans, 1961). The prevalence of cardiac arrhythmias is increased during cold water submersion with breath-holding (Tipton et al. 2010), and this should be avoided. "

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    ABSTRACT: In non-habituated subjects, cold-shock response to cold-water immersion causes rapid reduction in cerebral blood flow velocity (approximately 50%) due to hyperventilation, increasing risk of syncope, aspiration, and drowning. Adaptation to the response is possible, but requires several cold immersions. This study examines whether thorough instruction enables non-habituated persons to attenuate the ventilatory component of cold-shock response. There were nine volunteers (four women) who were lowered into a 0 degrees C immersion tank for 60 s. Middle cerebral artery mean velocity (CBFV) was measured together with ventilatory parameters and heart rate before, during, and after immersion. Within seconds after immersion in ice-water, heart rate increased significantly from 95 +/- 8 to 126 +/- 7 bpm (mean +/- SEM). Immersion was associated with an elevation in respiratory rate (from 12 +/- 3 to 21 +/- 5 breaths, min(-1)) and tidal volume (1022 +/- 142 to 1992 +/- 253 ml). Though end-tidal carbon dioxide tension decreased from 4.9 +/- 0.13 to 3.9 +/- 0.21 kPa, CBFV was insignificantly reduced by 7 +/- 4% during immersion with a brief nadir of 21 +/- 4%. Even without prior cold-water experience, subjects were able to suppress reflex hyperventilation following ice-water immersion, maintaining the cerebral blood flow velocity at a level not associated with impaired consciousness. This study implies that those susceptible to accidental cold-water immersion could benefit from education in cold-shock response and the possibility of reducing the ventilatory response voluntarily.
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