Accidental hypothermia

Background

1. Definition: Core Temp <35C (95F)
2. Severity:
   1. Mild hypothermia: 32-35C (90-95F)
   2. Moderate hypothermia: 28-32C (82-90F)
   3. Severe hypothermia: <28C (82F)
3. Pt not dead until warm and dead: 30-32C (86-89.6F)

DDx

1. Accidental (environmental) exposure
2. Metabolic disorders
   1. Hypoglycemia
   2. Hypothyroidism
   3. Hypoadrenalism
   4. Hypopituitarism
3. Hypothalamic and CNS
   1. Head trauma
   2. Tumor
   3. Stroke
   4. Wernicke encephalopathy
4. Drugs
   1. Ethanol
   2. Sedatives-hypnotics
5. Sepsis
6. Dermal disease
   1. Burns
   2. Exfoliative dermatitis
7. Acute incapacitating illness
8. Massive fluid or blood resuscitation

ECG

1. Typical sequence is sinus brady > a fib w/ slow ventricular response > v-fib > asystole
2. Other ECG findings:
   1. Osborn (J) wave
   2. T-wave inversions
   3. PR, QRS, QT prolongation
   4. Muscle tremor artifact
   5. AV block
   6. PVCs

Treatment

General

1. Handle pt gently
   1. V-fib may be induced by rough handling of pt due to irritable myocardium (anecdotal)
2. O2
   1. Hypothermia causes leftward shift of oxyhemoglobin dissociation curve
3. IVF
   1. Reasons:
      1. Hypothermia > impaired renal concentrating ability > cold diuresis
      2. Pts are prone to rhabdo
      3. Intravascular volume is lost due to extravascular shift
      4. 65°C > 45°C more efficacious
4. CPR
   1. Only perform if pt truly does not have a pulse (unnecessary CPR may lead to V-fib)
   2. Spend 30-45s attempting to detect respiratory activity and pulse before starting CPR
5. Dysrhythmias
   1. Occur once temp <30C (86F)
   2. Rewarming is treatment of choice
      1. Most dysrhythmias (e.g. sinus brady, a-fib/flutter) require no other therapy
         1. Activity of antiarrhythmics is unpredictable in hypothermia
         2. Hypothermic heart is relatively resistant to atropine, pacing, and countershock
   3. V-fib
      1. May be refractory to therapy until pt is rewarmed
      2. Attempt a single defibrillation attempt
         1. If unsuccessful continue CPR and attempt defibrillation again once temp >30C (86F)
6. Abx
   1. Give if suspect sepsis (e.g. hypothermia fails to correct w/ rewarming measures)
7. Thiamine
   1. Consider if Wernicke disease is possible cause of hypothermia (e.g. alcoholic pt)
8. Hydrocortisone
   1. Consider if pt has history of adrenal suppression or insufficiency
9. Thyroxine
   1. Consider if any suspicion for hypothyroidism/myxedema coma

Rewarming

1. Passive
   1. Consider in pt w/ mild hypothermia who is able to generate intrinsic heat
   2. Techniques
      1. Removal from cold environment
      2. Insulation
2. Active External
   1. Consider in:
      1. Moderate-severe hypothermia
      2. Mild hypothermia in pt who is unstable or cannot generate intrinsic heat
      3. Failure to respond to passive external rewarming
      4. May be ineffective in pts w/ poor perfusion or in cardiac arrest
   2. Techniques
      1. Rewarm trunk BEFORE the extremities
         1. Otherwise may lead to hypotension, core temperature afterdrop
      2. Warm water immersion
      3. Heating blankets
      4. Radiant heat
      5. Forced air
3. Active Internal
   1. Consider alone or along with active external warming in:
      1. Cardiovascular instability / life-threatening dysrhythmias
      2. Severe hypothermia
      3. Moderate hypothermia which fails to respond to less aggressive measures
   2. Techniques
      1. Heated IV fluids: 40C (104F)
         1. If central line is placed avoid irritating the heart
      2. GI tract lavage
      3. Bladder lavage
      4. Pleural lavage
      5. Peritoneal lavage

Complications

1. Aspiration PNA
2. DIC
3. Bleeding

Source

Tintinalli

See Also

• Therapeutic Hypothermia