Hypothermia is common in trauma patients and those exposed to cold environments. It can be accidental, primary, secondary, or therapeutic. Mild hypothermia between 32-35 degrees Celsius is used for neuroprotection, while moderate (28-32 degrees) is used for cardiopulmonary bypass. Physiologic changes associated with hypothermia include coagulopathies, metabolic effects, hypokalemia, hyperglycemia, and effects on the cardiovascular, immune, and coagulation systems. Treatment follows the ABCDE approach - ensuring a patent airway, warming humidified oxygen, warm IV fluids, monitoring for hypoglycemia, and passive or active external rewarming depending on severity. Core rewarm

1. HYPOTHERMIA
DR SYED INAYATHULLAH
INTENSIVISIT
MEEQAT HOSPITAL

2. types
•Accidental
•Primary and secondary
•Therapeutic

3. Accidental
•Critically ill patients predisposed
•Due to
•Removal of clothing
•Laparotomy and opening of body cavities
•Administration of large volume of unwarmed fluids and blood
products

4. severity
•Associated with trauma score and injury severity score
•Associated with worst outcome even after correction for age,injury
severity and hypotension
•Degree epiphenomenon than causative

5. therapeutic
•Used primarily for neuroprotection
•Used in cardiothoracic cases , circulatory arrest , cardiopulmonary
bypass
•Mild hypothermia showed benefit for out of hospital cardiac arrest
with improved neurological outcomes
•May have role in reducing ICP and traumatic brain injury

6. definition
•Mild 32-35 ( used in neuroprotection)
•Moderate 28-32 ( used in cardiopulmonary bypass)
•Severe 20-28
•Deep 11-20
•Profound 6-10( being studied in military as an aortic cold flush for
soldiers who are exanguinating prior to blood resuscitation

7. Physiologic Changes Associated with
Hypothermia

8. Epidemiology
•Common in trauma patients
•Common in areas with cold winters
•Occurs in critically ill hospitalized patients

9. Key pathophysiology
•34 degree Celsius is an important threshold
•Coagulopathies , enzymatic functions diminish significantly below this
temperature
•Effects on metabolism
•Hypokalemia
•Hyperglycemia
•Mild acidosis
•Impaired drug metabolism( through p 450 pathway)

10. Effects on coagulation
•Impaired enzymatic function in coagulation cascade
•Prolong prothrombin time and partial thromboplastin time
•Thrombocytopenia and platelet dysfuction

11. Effects on immune system
•Immunosupression
•Effects on cardiovascular system
•Bradyarrythmias
•Hypertension( due to peripheral vasoconstriction)
•Hypotension (due to negative inotropic effect)
•Osborne waves

13. causes

14. ABCDE approach (as always)

15. Airway
•Must be patent
•Be gentle with airway manoeuvres
•If comatose consider cuffed tracheal tube (and gastric tube); despite
potential risk of precipitating VF (risks overstated) the indications for
intubation do not alter in hypothermia
•Humidified & warmed air/oxygen is ideal

16. Breathing
•Warm humidified oxygen if available
•Oxygen if at all possible – ODC shifts to left
•If very slow / shallow breaths assist ventilations; avoid
hyperventilation – monitor pH, PaCO2 & ET CO2.
•Changes in PaCO2 have a greater effect on pH in hypothermia
•Pulse oximeter unreliable when skin shut down
•ABGs – don’t correct for temperature

17. Circulation
•Fluids should be warm (41) – microwave can be used
for saline
•But heat in the fluids will NOT be enough to rewarm the
patient
•Saline or isotonic dextrose
•10ml/kg bolus
•5ml/kg/hour infusion
•Don’t overload (consider CVP line if cardiopulmonary
comorbidity)
•e.g 700ml saline in first hour then 350ml/hour
•Avoid Hartmann’s – cold liver cannot metabolise lactate

18. Circulation
•Monitor fluid status carefully
•Invasive monitoring if fluid shifts likely or if pre-existing
cardiorespiratory problems
•Supplemental K may be needed – check U&Es
•Inotropes usually avoided; try to avoid catecholamines in patient with
frostbite

19. Disability
•If GCS down (and it will be in profound hypothermia) rule out / treat
hypoglycaemia
•In acute hypothermia glucose not low, if hypothermia occurs after
exhaustion of energy hypoglycaemia will be present

20. Other things to consider
•D also stands for “degrees”
•Measure core temperature
•Are they shivering?
•E stands for exposure
•Remove cold wet clothes
•But expose only one bit at a time and keep covered up as
much as possible
•Keep the room as warm as possible
•K stands for potassium
•Often low

21. Management and treatment
•Prevention( pre hospital passive rewarming)
•Passive rewarming ( cover with insulating material in a warm
environment)
•Usually adequate for mild hypothermia
•Active external rewarming ( applying heat directly to skin ( heating
pads, forced air, heat lamps)
•Watch for rewarming shock ( peripheral vasodilation in setting of
intravascular hypovolemia)

22. Active core rewarming
•Used in moderate to severe hypothermia when patient is still
maintaining adequate perfusion
•Can rewarm via vascular or pulmonary routes
•Lavage of various cavities
•Thoracic, peritoneal, urinary bladder but risky (marginally effective)
•Cardiopulmonary bypass for severe hypothermia with circulatory
arrest
•Watch for hyperkalemia with rewarming

23. Therapeutic hypothermia
•Intravascular cooling catheters effective but DVT risk increases by 50
percent in 3 days
•External cooling vests
•Cold saline infusion 4 degree Celsius 30 cc/kg in 30 minutes may be
given peripheral or femoral……..unclear with IJV/subclavian

31. outcomes
•Trauma-worst outcome-presumably due to its effect on coagulation
and hypotension
•Cardiac arrest: therapeutic hypothermia is effective when used in
comatosed cardiac arrest survivors within about 6 hours of circulatory
arrest
•Traumatic brain injury and ICP ---ineffective

32. •Thank you