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Autonomic nerve system responses for normal and slow rewarmers after hand cold provocation: effects of long-term cold climate training
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology. (Arcum)
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
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2013 (English)In: International Archives of Occupational and Environmental Health, ISSN 0340-0131, E-ISSN 1432-1246, Vol. 86, no 3, 357-365 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE: Differences among individuals concerning susceptibility to local cold injury following acute cold exposure may be related to function of the autonomic nervous system. We hypothesized that there are differences in heart rate variability (HRV) between individuals with normal or more pronounced vasoconstriction following cold exposure and that there is an adaptation related to prolonged cold exposure in autonomic nervous system response to cold stimuli.

METHODS: Seventy-seven young men performed a cold provocation test, where HRV was recorded during cold hand immersion and recovery. Forty-three subjects were re-examined 15 months later, with many months of cold weather training between the tests. Subjects were analyzed as 'slow' and 'normal' rewarmers according to their thermographic rewarming pattern.

RESULTS: For the 'pre-training' test, before cold climate exposure, normal rewarmers had higher power for low-frequency (P(LF)) and high-frequency (P(HF)) HRV components during the cold provocation test (ANOVA for groups: p = 0.04 and p = 0.005, respectively). There was an approximately 25 % higher P(HF) at the start in normal rewarmers, in the logarithmic scale. Low frequency-to-high frequency ratio (P(LF)/P(HF)) showed lower levels for normal rewarmers (ANOVA for groups: p = 0.04). During the 'post-training' cold provocation test, both groups lacked the marked increase in heart rate that occurred during cold exposure at the 'pre-training' setting. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low-frequency and high-frequency HRV components. After winter training, the slow rewarmers showed reduced low-frequency power for some of the cold provocation measurements but not all (average total P(LF), ANOVA p = 0.05), which was not present before winter training.

CONCLUSIONS: These HRV results support the conclusion that cold adaptation occurred in both groups. We conclude that further prospective study is needed to determine whether cold adaptation provides protection to subjects at higher risk for cold injury, that is, slow rewarmers.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2013. Vol. 86, no 3, 357-365 p.
Keyword [en]
hypothermia, automatic nervous system, physiological adaptation, heart rate variability
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:umu:diva-55582DOI: 10.1007/s00420-012-0767-3ISBN: 1432-1246 (Electronic) 0340-0131 (Linking) (print)OAI: oai:DiVA.org:umu-55582DiVA: diva2:527649
Note

Originally published in thesis in manuscript form.

Available from: 2012-05-22 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Accidental hypothermia and local cold injury: physiological and epidemiological studies on risk
Open this publication in new window or tab >>Accidental hypothermia and local cold injury: physiological and epidemiological studies on risk
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: (Papers I and II) The objectives were to first determine incidence and contributing factors to cold-related injuries in northern Sweden, both those that led to hospitalization and those that led to fatality.  (Papers III and IV) A further aim was to assess post-cooling hand-rewarming responses and effects of training in a cold environment, both on fingertip rewarming and on function of the autonomic nervous system, to evaluate if there was adaptation related to prolonged occupational cold exposure.

Methods:  In a retrospective analysis, cases of accidental cold-related injury with hospital admission in northern Sweden during 2000-2007 were analyzed (Paper I).  Cases of fatal hypothermia in the same region during 1992-2008 were analyzed (Paper II).  A cohort of volunteers was studied before and after many months of occupational cold exposure. Subject hand rewarming response was measured after a cold hand immersion provocation and categorized as slow, moderate or normal in rewarming speed.  This cold provocation and rewarming assessment was performed before and after their winter training.  (Paper III).  Heart rate variability (HRV) was analyzed from the same cold provocation/recovery sequences (Paper IV).

Results:  (Paper I) For the 379 cases of hospitalization for cold-related injury, annual incidences for hypothermia, frostbite, and drowning were 3.4/100,000, 1.5/100,000, and 1.0/100,000 inhabitants, respectively.  Male gender was more frequent for all categories.  Annual frequencies for hypothermia hospitalizations increased during the study period.  Hypothermia degree and distribution of cases were 20 % mild (between 32 and 35ºC), 40% moderate (31.9 to 28ºC), and 24% severe (< 28ºC), while 12% had temperatures over 35.0ºC.  (Paper II) The 207 cases of fatal hypothermia showed an annual incidence of 1.35 per 100,000 inhabitants, 72% in rural areas, 93% outdoors, 40% found within 100 meters of a building.  Paradoxical undressing was documented in 30%.  Ethanol was detected in femoral vein blood in 43%. Contributing co-morbidity was common including heart disease, previous stroke, dementia, psychiatric disease, alcoholism, and recent trauma.  (Paper III) Post-training, baseline fingertip temperatures and cold recovery variables in terms of final rewarming fingertip temperature and vasodilation time increased significantly in moderate and slow rewarmers.  Cold-related injury (frostbite) during winter training occured disproportionately more often in slow rewarmers (4 of the 5 injuries).  (Paper IV) At ‘pre- winter-training’, normal rewarmers had higher power for low frequency and high frequency heart rate variability.  After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low frequency and high frequency heart rate variability components. 

Conclusions: Hypothermia and cold injury continues to cause injury and hospitalization in the northern region of Sweden.  Assessment and management is not standardized across hospitals.  With the identification of groups at high risk for fatal hypothermia, it should be possible to reduce the incidence, particularly for highest risk subjects; rural, living alone, alcohol-imbibing, and psychiatric diagnosis-carrying citizens.  Long-term cold-weather training may affect hand rewarming patters after a cold provocation, and a warmer baseline hand temperature with faster rewarming after a cold provocation may be associated with less general risk for frostbite.  Heart rate variability results support the conclusion that cold adaptation in the autonomic nervous system occurred in both groups, though the biological significance of this is not yet clear.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2012. 82 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1508
Keyword
cold-related injuries, hypothermia, frostbite, cold adaptation, rewarming, autonomic nervous system, heart rate variability
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-55602 (URN)978-91-7459-438-6 (ISBN)
Public defence
2012-06-16, Bergasalen, byggnad 27, Norrlands Universitetssjukhus, Umeå, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2012-05-25 Created: 2012-05-23 Last updated: 2017-03-01Bibliographically approved

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Publisher's full texthttp://www.ncbi.nlm.nih.gov/pubmed/22526086

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Brändström, HelgeWiklund, UrbanGrip, HelenaHaney, Michael

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