Hypothermia

OVERVIEW

Hypothermia occurs when core body temperature is < 35°C

  • mild: 32-35°C
  • moderate: 28-32°C
  • severe: < 28°C

Swiss staging system

  • I – clearly conscious and shivering
  • II – impaired consciousness without shivering
  • III – unconscious
  • IV – not breathing
  • V – death due to irreversible hypothermia

CAUSES

Mechanisms

  • increased heat loss
  • decreased thermogenesis
  • impaired thermogenesis

Mutliple

  • age (elderly and infants at risk)
  • environmental – exposure, drowning, alpine environment, poverty (lack of heating or shelter)
  • drugs/ tox – alcohol, sedatives, vasodilators
  • Sepsis
  • CNS disorders e.g. hypothalamic lesions, hypopituitarism
  • Endocrine/ metabolic – hypothyroidism, adrenal insufficiency, hypothermia, malnutrition
  • Trauma — burns, spinal cord injury
  • Shock
  • Skin disorders — psoriasis, exfoliating conditions
  • Iatrogenic — cold fluid administration, intra-operative, therapeutic hypothermia
  • Psychiatirc (may lead to exposure)

EFFECTS

  • CVS: bradycardia is normal; decreased Q and MAP, vasoconstriction, ECG – widening of QRS, increased PR and QT, J waves, risk of VF < 28 C, increased blood viscosity and myocardial work
  • RESP: decreased CO2 production, decreased PAO2 and PaCO2 due to increased gas solubility, increased dead space, diaphragmatic fatigue, metabolic acidosis -> pulmonary hypertension
  • GI: decreased hepatic metabolism and blood flow, decreased splanchnic circulation
  • METABOLIC: decreased BMR, shivering, left shifted oxy-Hb dissociation curve, hyperglycaemia, decreased drug metabolism
  • CNS: neuroprotection, fixed dilated pupils at < 30 C (mimics brain death)
  • HAEM: increased bleeding time, PT and APTT, VTE risk, decreased platelet and WCC
  • RENAL: decreased GFR and RBF, cold-induced diuresis

MANAGEMENT

Resuscitation

  • pulse check – palpate for up to 1 minute (consider Echo / Doppler as hard to find – do not delay CPR)
  • move patient gently if <32 degrees due to risk of triggering VF (risk is overstated)
  • no adrenaline or other drugs until >30C
  • between 30-35C double the dose intervals of ACLS drugs
  • shock VF up to 3 times if necessary, then no further shocks until T>30C
  • ‘not dead until warm and dead’ (30-32C)

Passive warming – useful in conscious patients who are able to shiver  (1.5C per hour)

  • keep dry
  • warm environment
  • insulation with blankets (e.g. aluminium foil) and hat
  • allow to mobilise if conscious (beware of hypotension on cessation of exercise)

Peripheral active warming

  • chemical heat pads
  • radiant methods
  • forced air warming blankets (1-2C/h)

NB. Afterdrop, a drop in core body temperature during rewarming may occur a consequence of peripheral vasodilation and release of cold peripheral blood to the body core. It is not usually significant.

Central active warming

  • warmed (40-46C) humidified inspired gases (1 C/h; 1.5°C/h ET tube)
  • warm IV fluids (42C)  (only give if need fluids, prevents cooling rather than promotes warming) – use Level 1 fluid warmer
  • body cavity lavage with 40C fluid e.g. peritoneal (3C/h), gastric, bladder, right-sided thoracic lavage (3-6C/h – use 2 ICCs for continuous flow)
  • RRT
  • ECMO/ bypass (9-18C/h)

Supportive care and monitoring

  • use esophageal probe preferentially (core temperature, minimal lag time)
  • use low reading thermometer
  • ABG measurements at 37C (temperature uncorrected values) to allow serial monitoring

Seek and treat cause and complications

REWARMING RATES FOR DIFFERENT METHODS

  • Shivering 1.5° C/hr
  • Warming Blanket 2° C/hr
  • Warm O2 1 °C/hr with mask; 1.5° C/hr ET tube
  • IV Fluids do not add, but do not take away either
  • Peritoneal Lavage 3° C/hr
  • Thoracic Lavage with Chest Tubes 3-6° C/hr
  • Cardiac Bypass 9-18° C/hr

THORACIC LAVAGE

  • Place two 32-36 F intercostal catheters: one anterior and one posterior lateral
  • Use 3L bags of 40-42 C saline
  • Use a Level 1 Fluid Warmer to pump warm fluids into the anterior chest tube (e.g. 180 mL/min)
  • attach auto-transfuser or pleur-evac to posterior-lat chest tube to allow continuous emptying
  • alternative is to use one chest tube with a y connector to administer 300 cc boluses with 2 minute dwell time before drainage

References and Links

LITFL

Journal articles

  • Brown DJ, Brugger H, Boyd J, Paal P. Accidental hypothermia. N Engl J Med. 2012 Nov 15;367(20):1930-8. doi: 10.1056/NEJMra1114208. Review. Erratum in: N Engl J Med. 2013 Jan 24;368(4):394. PubMed PMID: 23150960
  • Epstein E, Anna K. Accidental hypothermia. BMJ. 2006 Mar 25;332(7543):706-9. Review. PubMed PMID: 16565126; PubMed Central PMCID: PMC1410860.
  • Guly H. History of accidental hypothermia. Resuscitation. 2011 Jan;82(1):122-5. doi: 10.1016/j.resuscitation.2010.09.465. Epub 2010 Oct 30. PubMed PMID: 21036455; PubMed Central PMCID: PMC3060344.
  • Plaisier BR. Thoracic lavage in accidental hypothermia with cardiac arrest–report of a case and review of the literature. Resuscitation. 2005 Jul;66(1):99-104. Epub 2005 Apr 18. Review. PubMed PMID: 15993735.

FOAM and web resources


CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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