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Heat-related Illnesses

General Information

Description

  • inability of physiological thermoregulation mechanisms to compensate for a rise in body temperature due to elevated extracorporeal temperatures (especially when combined with high humidity), physical exertion, or metabolism resulting in a range of conditions, such as1,2,3,4
    • heatstroke
    • heat exhaustion
    • heat cramps

Also called

  • heat stress

Definitions

  • hyperthermia - elevated body temperature with or without symptoms
  • heatstroke - core body temperature ≥ 104 degrees F (40 degrees C) with central nervous system dysfunction; can progress to multiple system organ failure1,2,3,4
    • classic heatstroke - passive hyperthermia resulting from impaired heat dissipation and/or persistent heated environment; usually takes days to develop
    • exertional heatstroke - hyperthermia associated with physical activity leading to heat exposure; usually develops faster
  • heat exhaustion - mild-to-moderate illness due to loss of salt and water during heat exposure1,2,3,4
    • core temperature may be low, normal, or high (but < 104 degrees F [40 degrees C])
    • symptoms vary and can include fatigue, tachycardia, profuse diaphoresis, nausea or vomiting, and weakness without central nervous system involvement
  • heat syncope - transient loss of consciousness or collapse during heat exposure1,3,4
    • elevated core temperature not needed to make diagnosis
    • associated with relatively rapid return to baseline
  • heat tetany - carpopedal spasm, paresthesia, and hyperventilation1
  • heat cramps - exercise-associated involuntary muscle contractions (usually in lower extremities)1,2,3,4
    • usually occur after core body temperature has cooled to normal
    • may be due to loss of electrolytes and/or water
  • heat edema - dependent edema caused by prolonged cutaneous vasodilation1,2, 3, 4
    • core body temperature normal
    • benign and self-limiting condition
    • usually in lower extremities and in older persons poorly acclimated to heat
  • heat rash1,2, 3
    • rash due to plugging of sweat glands during chronic exposure to heat and humidity
    • also referred to as lichen tropicus, prickly heat, or miliaria rubra

References

General references used

  1. Santelli J, Sullivan JM, Czarnik A, and Bedolla J. Heat illness in the emergency department: keeping your cool. Emerg Med Pract. 2014 Aug;16(8):1-21
  2. Atha WF. Heat-related illness. Emerg Med Clin North Am. 2013 Nov;31(4):1097-108
  3. Mangus CW, Canares TL. Heat-Related Illness in Children in an Era of Extreme Temperatures. Pediatr Rev. 2019 Mar;40(3):97-107full-text
  4. Lipman GS, Gaudio FG, Eifling KP, Ellis MA, Otten EM, Grissom CK. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness Environ Med. 2019 Jun 17 early online

Recommendation grading systems used

  • Wilderness Medical Society (WMS) classification for grading evidence and recommendations
    • Grade 1A
      • strong recommendation, high-quality evidence
      • benefits clearly outweigh risks and burdens or vice versa
      • supporting evidence from randomized controlled trials without important limitations or overwhelming evidence from observational studies
    • Grade 1B
      • strong recommendation, moderate-quality evidence
      • benefits clearly outweigh risks and burdens or vice versa
      • supporting evidence from randomized controlled trials with important limitations or exceptionally strong evidence from observational studies
    • Grade 1C
      • strong recommendation, low-quality or very low-quality evidence
      • benefits clearly outweigh risks and burdens or vice versa
      • supporting evidence from observational studies and case series
    • Grade 2A
      • weak recommendation, high-quality evidence
      • benefits closely balanced with risks and burdens
      • supporting evidence from randomized controlled trials without important limitations or overwhelming evidence from observational studies
    • Grade 2B
      • weak recommendation, moderate-quality evidence
      • benefits closely balanced with risks and burdens
      • supporting evidence from randomized controlled trials with important limitations or exceptionally strong evidence from observational studies
    • Grade 2C
      • weak recommendation, low-quality or very low-quality evidence
      • uncertainty in estimates of benefits, risks, and burden; benefits, risk, burden may be closely balanced
      • supporting evidence from observational studies and case series
    • Reference - WMS practice guideline on prevention and treatment of heat illness (Wilderness Environ Med 2019 Jun 17 early online)
  • American College of Sports Medicine (ACSM) quality of evidence ratings
    • Evidence Category A - recommendation based on consistent and good-quality patient- or subject-oriented evidence
    • Evidence Category B - recommendation based on inconsistent or limited-quality patient- or subject-oriented evidence
    • Evidence Category C - recommendation based on consensus, usual practice, opinion, disease-oriented evidence, or case series
    • Reference - ACSM position statement on exertional heat illness during training and competition (17473783Med Sci Sports Exerc 2007 Mar;39(3):556)

Synthesized Recommendation Grading System for DynaMed Content

  • The DynaMed Team systematically monitors clinical evidence to continuously provide a synthesis of the most valid relevant evidence to support clinical decision-making (see 7-Step Evidence-Based Methodology).
  • Guideline recommendations summarized in the body of a DynaMed topic are provided with the recommendation grading system used in the original guideline(s), and allow users to quickly see where guidelines agree and where guidelines differ from each other and from the current evidence.
  • In DynaMed content, we synthesize the current evidence, current guidelines from leading authorities, and clinical expertise to provide recommendations to support clinical decision-making in the Overview & Recommendations section.
  • We use the Grading of Recommendations Assessment, Development and Evaluation (GRADE) to classify synthesized recommendations as Strong or Weak.
    • Strong recommendations are used when, based on the available evidence, clinicians (without conflicts of interest) consistently have a high degree of confidence that the desirable consequences (health benefits, decreased costs and burdens) outweigh the undesirable consequences (harms, costs, burdens).
    • Weak recommendations are used when, based on the available evidence, clinicians believe that desirable and undesirable consequences are finely balanced, or appreciable uncertainty exists about the magnitude of expected consequences (benefits and harms). Weak recommendations are used when clinicians disagree in judgments of relative benefit and harm, or have limited confidence in their judgments. Weak recommendations are also used when the range of patient values and preferences suggests that informed patients are likely to make different choices.
  • DynaMed synthesized recommendations (in the Overview & Recommendations section) are determined with a systematic methodology:
    • Recommendations are initially drafted by clinical editors (including ≥ 1 with methodological expertise and ≥ 1 with content domain expertise) aware of the best current evidence for benefits and harms, and the recommendations from guidelines.
    • Recommendations are phrased to match the strength of recommendation. Strong recommendations use "should do" phrasing, or phrasing implying an expectation to perform the recommended action for most patients. Weak recommendations use "consider" or "suggested" phrasing.
    • Recommendations are explicitly labeled as Strong recommendations or Weak recommendations when a qualified group has explicitly deliberated on making such a recommendation. Group deliberation may occur during guideline development. When group deliberation occurs through DynaMed Team-initiated groups:
      • Clinical questions will be formulated using the PICO (Population, Intervention, Comparison, Outcome) framework for all outcomes of interest specific to the recommendation to be developed.
      • Systematic searches will be conducted for any clinical questions where systematic searches were not already completed through DynaMed content development.
      • Evidence will be summarized for recommendation panel review including for each outcome, the relative importance of the outcome, the estimated effects comparing intervention and comparison, the sample size, and the overall quality rating for the body of evidence.
      • Recommendation panel members will be selected to include at least 3 members that together have sufficient clinical expertise for the subject(s) pertinent to the recommendation, methodological expertise for the evidence being considered, and experience with guideline development.
      • All recommendation panel members must disclose any potential conflicts of interest (professional, intellectual, and financial), and will not be included for the specific panel if a significant conflict exists for the recommendation in question.
      • Panel members will make Strong recommendations if and only if there is consistent agreement in a high confidence in the likelihood that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. Panel members will make Weak recommendations if there is limited confidence (or inconsistent assessment or dissenting opinions) that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. No recommendation will be made if there is insufficient confidence to make a recommendation.
      • All steps in this process (including evidence summaries which were shared with the panel, and identification of panel members) will be transparent and accessible in support of the recommendation.
    • Recommendations are verified by ≥ 1 editor with methodological expertise, not involved in recommendation drafting or development, with explicit confirmation that Strong recommendations are adequately supported.
    • Recommendations are published only after consensus is established with agreement in phrasing and strength of recommendation by all editors.
    • If consensus cannot be reached then the recommendation can be published with a notation of "dissenting commentary" and the dissenting commentary is included in the topic details.
    • If recommendations are questioned during peer review or post publication by a qualified individual, or reevaluation is warranted based on new information detected through systematic literature surveillance, the recommendation is subject to additional internal review.

DynaMed Editorial Process

  • DynaMed topics are created and maintained by the DynaMed Editorial Team and Process.
  • All editorial team members and reviewers have declared that they have no financial or other competing interests related to this topic, unless otherwise indicated.
  • DynaMed content includes Practice-Changing Updates, with support from our partners, McMaster University and F1000.

Special acknowledgements

  • DynaMed topics are written and edited through the collaborative efforts of the above individuals. Deputy Editors, Section Editors, and Topic Editors are active in clinical or academic medical practice. Recommendations Editors are actively involved in development and/or evaluation of guidelines.
  • Editorial Team role definitions
    Topic Editors define the scope and focus of each topic by formulating a set of clinical questions and suggesting important guidelines, clinical trials, and other data to be addressed within each topic. Topic Editors also serve as consultants for the internal DynaMed Editorial Team during the writing and editing process, and review the final topic drafts prior to publication.
    Section Editors have similar responsibilities to Topic Editors but have a broader role that includes the review of multiple topics, oversight of Topic Editors, and systematic surveillance of the medical literature.
    Recommendations Editors provide explicit review of Overview and Recommendations sections to ensure that all recommendations are sound, supported, and evidence-based. This process is described in "Synthesized Recommendation Grading."
    Deputy Editors oversee DynaMed internal publishing groups. Each is responsible for all content published within that group, including supervising topic development at all stages of the writing and editing process, final review of all topics prior to publication, and direction of an internal team.

How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T114802, Heat-related Illnesses; [updated 2018 Nov 30, cited place cited date here]. Available from https://www.dynamed.com/topics/dmp~AN~T114802. Registration and login required.

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