Kasia Munson, MD

Emergency Medicine

PGY 2

*

*

*Define Hypothermia

*Pathophysiology of temperature regulation

*Physiologic changes in hypothermia

*Labs and Drugs in hypothermia

*Various rewarming methods

*Disposition

*

Accidental Hypothermia is defined as an unintentional drop in core body temperature below 35 C.

Mild = 32C – 35C

Moderate = 28C – 32C

Severe = <28C

*

*Mortality (in-patient)

1999 to 2011, a total of 16,911 deaths in the United States, an average of 1,301 per yearOverall - 12%

Moderate - 21%

Moderate – severe – 40%

*Sex

67% Males

*Age

Increased risk at extremes of age

50% of the recorded deaths > 65 years old

*

*

*Hypothalamus: Shivering thermogenesis and

non-shivering heat conservation and

dissipation.

*Cold hypothalamus TRH pituitary

gland TSH thyroid gland thyroxine

*Sympathetic vasoconstriction

*

*Evaporation –insensible losses and sweat

*Radiation – infrared electromagnetic energy

*Conduction –transfer to a cooler adjacent object

*Convection – transfer convective currents of air or water

*

* Decreased Heat Production:

Hypopituitarism, Hypothyroidism,

Diabetes, Insufficient fuel, Hypoglycemia,

Malnutrition, Marasmus/Kwashiorkor,

Extreme exertion, Neuromuscular

inefficiency, Age extremes, Impaired

shivering, Inactivity, Lack of adaptation

* Ireased Heat Loss

Immersion, Nonimmersion, Induced

vasodilation, Pharmacologic, Toxicologic,

Erythrodermas, Burns, Psoriasis,

Ichthyosis, Exfoliative dermatitis,

* Iatrogenic:

Emergency deliveries, Cold infusions,

Heatstroke treatment

* Impaired Thermoregulation:

Peripheral failure, Neuropathies, Acute

spinal cord transection, Diabetes,

Central failure, neurologic, Central

nervous system trauma, Cerebrovascular

accident, Hypothalamic dysfunction,

Parkinson's disease, Anorexia nervosa,

Cerebellar lesion, Neoplasm, Congenital

intracranial anomalies, Multiple sclerosis

* Misc

Sepsis, Pancreatitis, Carcinomatosis,

Cardiopulmonary disease, Vascular

insufficiency, Uremia, Paget's disease,

Giant cell arteritis, Sarcoidosis, shaken

baby syndrome, Multisystem trauma,

Shapiro's syndrome, Wernicke-Korsakoff,

Hodgkin's disease

*

*Decreased Heat Production

*Increased Heat Loss

*Ethanol

*Impaired Thermoregulation

*Iatrogenic

*Infections

*Trauma

*Miscellaneous Causes

*

*

*Patients may recover completely after presenting in a rigid, apneic state with fixed and dilated pupils.

*Resuscitative efforts should be continued until core temperature is at least 30°C to 32°C

*33-35 C = tachycardia, shivering, Increased

BMR, dysarthria, Normal BP,

ataxia

*29-32 C = stupor, dec O2 use, hypovolemia

a.fib/arrhythmias, dec pulse and

CO, dec RR, pupils dilated,

pulse down 50%, j waves

*22-28 C = V.fib, no DTR or brainstem

reflexes, acid/base changes, CBF

30%/CO 45%

*18 C = Asystole

*Central Nervous System

*Cerebral autoregulation is maintained with an increase

in vascular resistance until 25° C.

*Progressive depression of CNS, some responsive with

intact reflexes at 27 to 25° C.

*EEG flat < 20C

*Reflexes hyperactive to 32C then hypoactive to 26C

then disappear.

*

*Tachycardia progressing to bradycardia

*Atrial fibrillation < 32° C.

*Pulse < 50% at 28° C.

*Asystole and VF spontaneously < 25° C.

*EKG - the Osborn (J) wave

*

* Increased RR then progressive decrease

*Oxygen unloading capacity is <50%

*Carbon dioxide production decreases 50%

*Viscous bronchorrhea, and noncardiogenicpulmonary edema.

*depression of cough and gag reflexes

*

*Renal Blood Flow <50% at 27 to 30° C

*Cold induced diuresis

*Stiff to pseudo–rigor mortis to opisthotonos.

*Fixed, dilated pupils

*

*What exactly IS a core temperature?

*What is the best way to obtain one?

*

*

*Glucose (POC)

*ABG (uncorrected)

*CBC

*CMP (with Ca, Mg)

*Amylase and Lipase

*PT/PTT/INR

*ABG’s

*Acidosis - due to severe respiratory

depression and carbon dioxide retention

*Alkalosis - from diminished CO2

production with low metabolic rates

*Hypothermia causes a leftward shift of

the oxyhemoglobin dissociation curve

*

*CBC

*Leukocytes and platelets low

*Hct deceptively increased

*Electrolytes

*Potassium

*Glucose

*Sodium

*

*Increased thrombosis

*DIC picture

*Clinically coagulopathic

*

*Lipase

*Cortisol

*Thyroid

*

*The efficacy of most medications is

temperature dependent

*Pharmacologic manipulation of the pulse

and blood pressure should be avoided.

*Dysrhythmias: Most convert spontaneously

during rewarming

*Transvenous intracardiac pacing is

hazardous

*

*Thiamine

* Antibiotics, steroids, and thyroid hormone

*Hydrocortisone

*Thyroid hormone

*

*If a patient's mental status remains altered despite

rewarming, CNS injury or infection should be

suspected.

*In children younger than 3 months, empirical

antibiotics after culture are indicated.

*Adults - Antibiotics should be administered if the

clinical picture is consistent with septic shock, if

there is failure to rewarm, or if aspiration has

occurred.

*

*Patients who are cold, stiff, and cyanotic,

with fixed pupils and inaudible heart

tones, without visible thoracic excursions,

continue to be successfully resuscitated.

*

*Remove from the cold

*careful, gentle handling

*Warm Oxygen and IV fluids

*Most rhythm disturbances require no

therapy and revert spontaneously with

rewarming.

*

*Temperature

Esophageal probe is ideal.

Alternatively, rectal or bladder probe.

*Blood Pressure

May need doppler

*O2 Sat

Uncertain reliability with poor

perfusion.

*Urine Output

Foley should be placed for accurate

measurement.

*Volume Resuscitation

*Fluids administered intravenously should be heated to 40 to 42° C.

*Rapid central venous administration may produce myocardial thermal gradients

*Most patients will be free water depleted

*

*If VT or VF is present, defibrillation should be attempted. If the single defibrillation attempt is unsuccessful, active rewarming should be initiated and CPR continued until core temperature is above 30° C.

*Use ACLS?

*Use Vasopressors?

*Advanced Life Support

*CPR should not be withheld unless DNR, obviously lethal injuries, chest wall depression is impossible, signs of life are present.

*If possible, verify with Doppler ultrasound examination that there is no spontaneous mechanical cardiac activity before chest compressions are initiated.

*

*No controlled studies comparing

rewarming methods in hypothermia

exist, rigid treatment protocols

would not be evidence based

*

Passive rewarming

* Removal from cold environment

* Insulation

Active external rewarming

* Warm water immersion* Heating blankets set at

40°C (104°F)* Radiant heat* Forced air

Active Core rewarming

* Inhalation rewarming* Heated IV fluids* GI tract lavage* Bladder lavage* Peritoneal lavage* Pleural lavage* Extracorporeal

rewarming* Mediastinal lavage by

thoracotomy

*

*By far the most important consideration

in the selection of rewarming techniques

is the patient’s cardiovascular status; a

secondary consideration is the presenting

temperature.

*

*Mild Hypothermia = Passive or

minimally invasive

*Cardiovascular instability = rapid

rewarming. ECMO if available.

*Stable patients are more

controversial.

*

*Must have intact thermoregulatory

mechanisms and be capable of

metabolic heat production

*

*Non-Invasive

*Treatment of choice for mild

hypothermia

*Minimizes convection and

evaporation

*

*Direct transfer of exogenous heat to patient

*External or Internal

*Impaired thermoregulation

*DKA

*Cardiovascular instability

*Moderate or severe hypothermia (≤32.2° C)

* Inadequate rate of rewarming or failure to

rewarm

*Traumatic or toxicologic peripheral vasodilaton

*Inhalation rewarming = humidified oxygen

by facemask or ET tube

* IV fluids and blood should be warmed to

40°C (104°F) before administration

*

*The Bair Hugger is most practical in

the emergency department

*Arteriovenous anastomosis (AVA)

*Combining of truncal AER with core

rewarming can also be successful.

*

*Delivers dialysate at 40 to 45° C to

the peritoneal cavity

*Rates average 1 to 3° C/hr

*Hepatic rewarming

*

*Gastric or colonic irrigation can cause

fluid and electrolyte fluxes. These techniques are

rarely indicated.

*Closed thoracic lavage - reserved for the

severely hypothermic patient who does not respond

to standard techniques or the patient with another

indication for a chest tube. rewarming averages

3° C/hr

*Mediastinal irrigation and direct

myocardial lavage - only in patients without

spontaneous perfusion.

*

*Ultrasonic and low-frequency microwave irradiation.

* One study rewarmed 16 piglets with microwave irradiation, another 20 human babies.

*Diathermy is still experimental

*

*Venovenous (2-3° C/hr)

Central venous to central venous or peripheral

catheter. No oxygenator/circulatory support

*Hemodialysis (3-4° C/hr)

Single- or dual-vessel cannulation, Stabilizes

electrolyte or toxicologic abnormalities.

*

*Arteriovenous (3-4° C/hr)

Percutaneous 8.5F femoral catheters . Requires

blood pressure of 60 mm Hg systolic. No

perfusionist/pump/anticoagulation.

*Cardiopulmonary bypass (up to 9.5° C/hr)

Cardiopulmonary bypass circuit Full circulatory

support with the pump and oxygenator

*

*Uncomplicated - low mortality rate

*Significant associated diseases - worse prognosis

*Asphyxia or near-drowning – very poor

*Grave prognostic indicators include evidence of

intravascular thrombosis (fibrinogen < 50 mg/dL),

cell lysis (hyperkalemia > 10-12 mEq/L), and

ammonia levels greater than 250 mmol/L

*

*Mild = Home

*Almost all others = Admission

*

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