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Accidental hypothermia and local cold injury: physiological and epidemiological studies on risk
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology. (Arcum)
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 [en]
cold-related injuries, hypothermia, frostbite, cold adaptation, rewarming, autonomic nervous system, heart rate variability
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:umu:diva-55602ISBN: 978-91-7459-438-6 (print)OAI: oai:DiVA.org:umu-55602DiVA: diva2:527959
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
List of papers
1. Accidental cold-related injury leading to hospitalization in northern Sweden (2000-2007)
Open this publication in new window or tab >>Accidental cold-related injury leading to hospitalization in northern Sweden (2000-2007)
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(English)Manuscript (preprint) (Other academic)
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-55588 (URN)
Available from: 2012-05-22 Created: 2012-05-22 Last updated: 2012-05-25Bibliographically approved
2. Fatal hypothermia: an analysis from a sub-arctic region
Open this publication in new window or tab >>Fatal hypothermia: an analysis from a sub-arctic region
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2012 (English)In: International Journal of Circumpolar Health, ISSN 1239-9736, E-ISSN 2242-3982, Vol. 71, no 0, 1-7 p.Article in journal (Refereed) Published
Abstract [en]

Objectives. To determine the incidence as well as contributing factors to fatal hypothermia.

Study design. Retrospective, registry-based analysis.

Methods. Cases of fatal hypothermia were identified in the database of the National Board of Forensic Medicine for the 4 northernmost counties of Sweden and for the study period 1992-2008. Police reports, medical records and autopsy protocols were studied.

Results. A total of 207 cases of fatal hypothermia were noted during the study period, giving an annual incidence of 1.35 per 100,000 inhabitants. Seventy-two percent occurred in rural areas, and 93% outdoors. Many (40%) were found within approximately 100 meters of a building. The majority (75%) occurred during the colder season (October to March). Some degree of paradoxical undressing was documented in 30%. Ethanol was detected in femoral vein blood in 43% of the victims. Contributing co-morbidity was common and included heart disease, earlier stroke, dementia, psychiatric disease, alcoholism, and recent trauma.

Conclusions. With the identification of groups at high risk for fatal hypothermia, it should be possible to reduce risk through thoughtful interventions, particularly related to the highest risk subjects (rural, living alone, alcohol-imbibing, and psychiatric diagnosis-carrying) citizens.

National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-55587 (URN)10.3402/ijch.v71i0.18502 (DOI)22584518 (PubMedID)
Available from: 2012-05-22 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved
3. Hand cold recovery responses before and after 15 months of military training in a cold climate
Open this publication in new window or tab >>Hand cold recovery responses before and after 15 months of military training in a cold climate
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2008 (English)In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 79, no 9, 904-908 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: The ability of fingers to rapidly rewarm following cold exposure is a possible indicator of cold injury protection. We categorized the post-cooling hand-rewarming responses of men before and after participation in 15 mo of military training in a cold environment in northern Sweden to determine: 1) if the initial rewarming category was related to the occurrence of local cold injury during training; and 2) if cold training affected subsequent hand-rewarming responses. METHODS: Immersion of the dominant hand in 10 degrees C water for 10 min was performed pre-training on 77 men. Of those, 45 were available for successful post-training retests. Infrared thermography monitored the dorsal hand during 30 min of recovery. Rewarming was categorized as normal, moderate, or slow based on mean fingertip temperature at the end of 30 min of recovery (TFinger,30) and the percentage of time that fingertips were vasodilated (%VD). RESULTS: Cold injury occurrence during training was disproportionately higher in the slow rewarmers (four of the five injuries). Post-training, baseline fingertip temperatures and cold recovery variables increased significantly in moderate and slow rewarmers: TFinger30 increased from 21.9 +/- 4 to 30.4 +/- 6 degrees C (Moderate), and from 17.4 +/- 0 to 22.3 +/- 7 degrees C (Slow); %VD increased from 27.5 +/- 16 to 65.9 +/- 34% (Moderate), and from 0.7 +/- 2 to 31.7 +/- 44% (Slow). CONCLUSIONS: Results of the cold recovery test were related to the occurrence of local cold injury during long-term cold-weather training. Cold training itself improved baseline and cold recovery in moderate and slow rewarmers.

Keyword
cold adaptation, acclimatization, habituation, frostbite, local cold injury, thermoregulation, peripheral vasoconstriction
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-22439 (URN)10.3357/ASEM.1886.2008 (DOI)18785360 (PubMedID)
Available from: 2009-05-08 Created: 2009-05-08 Last updated: 2017-12-13Bibliographically approved
4. Autonomic nerve system responses for normal and slow rewarmers after hand cold provocation: effects of long-term cold climate training
Open this publication in new window or tab >>Autonomic nerve system responses for normal and slow rewarmers after hand cold provocation: effects of long-term cold climate training
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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
Keyword
hypothermia, automatic nervous system, physiological adaptation, heart rate variability
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:umu:diva-55582 (URN)10.1007/s00420-012-0767-3 (DOI)1432-1246 (Electronic) 0340-0131 (Linking) (ISBN)
Note

Originally published in thesis in manuscript form.

Available from: 2012-05-22 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved

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