HYPOTHERMIADR SYED INAYATHULLAH

INTENSIVISIT MEEQAT HOSPITAL

types

•Accidental•Primary and secondary

•Therapeutic

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

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

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

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

Physiologic Changes Associated with Hypothermia

Epidemiology

•Common in trauma patients

•Common in areas with cold winters

•Occurs in critically ill hospitalized patients

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)

Effects on coagulation

•Impaired enzymatic function in coagulation cascade

•Prolong prothrombin time and partial thromboplastin time

•Thrombocytopenia and platelet dysfuction

Effects on immune system

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

causes

ABCDE approach (as always)

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

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

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

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

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

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

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)

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

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

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

•Thank you