AccidentalHypothermia

The Basics

Clinical Questions

Treatment

Who gets hypothermia?

Case:

25 M Ice climber…

Temp: 31 degrees

How would you classify this pt’s hypothermia?

31 degrees C

Mild: Core temp. 32 to 35ºC

Moderate: Core temp. 28 to 32ºC

Severe: Core temp. below 28ºC

Mild:34 - amnesia and dysarthria begin33 - ataxia and apathy develop

Moderate:32 - stupor31 - shivering stops30 - dysrhythmias, CO drops, insulin ineffective

Severe:28 - high risk for VF27 - lose reflexes and voluntary movement26 - major A/B disturbance

Profound:19 - flat EEG18 - asystole

Pretend there is no history of exposure…why else could this

patient be hypothermic?

Differential Diagnosis

Increased Heat Loss

Decreased Heat

Production

Impaired Heat Regulation

What mechanisms contribute to heat loss in our patient?

Evaporation, radiation, conduction, convection….

How is the cold affecting this patient?

At the body level?

At the organ system level?

QuickTime™ and a decompressor

are needed to see this picture.

Increase HR

Progressive bradycardia

Ventricular Arrhythmias

Asystole

QuickTime™ and a decompressor

are needed to see this picture.

The J Wave

Cold diuresis

Reduced renal flow

Progressive depression

perfusion maintained until 25 degrees

19 degrees flat EEG

Initial stimulation

Progressive decrease

CO2 retention and Acidosis

Case continued….

What is the most accurate method of measuring his

temperature?

Rectal temperature (insert to 15 cm)- ? Accurately reflect brain/heart temperature- Influenced by adjacent frozen stool- lags behind core temperature changes

Oral- Often do not measure below 34 degrees C.

Tympanic- accurately reflect hypothalamus if true tympanic

Axilla- easily affected by external factors

Esophogeal (insert to 24 cm)-can be affected by warm airway temperature in tubed patient

ChemstripElectrolytesCreatinine, BUNHg, WBC, PltLactateEKGABG

Other: CK, fibrinogen, INR, cortisol, thyroid

Blood Work

Chemstrip:-Insulin ineffective below 30 degrees -persistent elevation despite rewarming signals secondary cause

Hct:-Increases 2% for every drop by 1 degree C-Beware of the hypothermic patient with a normal/low hematocrit

ABG:-Historically controversial-Use uncorrected values

Blood Work

How can you rewarm him?

Passive External Rewarming (PER)

• Providing blankets

• Moving to a warm environment

• Heated IV fluids/oral fluids

**pt must be able to produce their own heat

***slow rise in temperature

Active External Rewarming

• Applying heat to the skin:

– Warm blankets– Bear Hugger– Immersion warming– Brokeback Hug?

Active Internal Rewarming

• Peritoneal dialysis

• Bladder, gastric, or colonic lavage

• Heated intravenous fluids

• Heated humidified oxygen

• Thoracic cavity lavage

• Extracorporeal blood rewarming

• Hemodialysis

Recipe:

Warmed NS

1) Place 1L NS in 650 W microwave

2) Cook on high for 120s, turning and shaking it once at midcycle

3) Agitate before infusion

Inhaled warmed O2

• Use warmed air at 45 degrees celcius

• Up to 2 degrees/hr*

Peritoneal Lavage

• Use Arrow peritoneal lavage kit

• Up to 3 degrees C/hour

GI and bladder rewarming

• 1.5-2.0 degrees/hour

Thoracic Cavity Lavage

Up to 6 or 7 degrees/hour reported

Cardiac Bypass

• Need to consult CV surgery

• Up to 2 degrees/5 mins

Hemodialysis

• Up to 4.5 degrees/hour

Comparison of Rewarming Rates

Case Continued

• Why has this patient become more hypothermic despite your warming measures?

Approach to rewarming

Mild Hypothermia

Passive External Rewarming

+/- Active External Rewarming

Approach to rewarming

Moderate Hypothermia

Active External Rewarming

Active Internal Rewarming

Approach to Rewarming

Severe Hypothermia

Level 1 callout

If Stable, treat as moderate but be prepared for ecmo

If Unstable, ACLS and prepare for ecmo

ACLS guidelines?BLS:

-prevent heat loss, rewarm-mild AH = passive rewarming-moderate AH = AER-Severe + Stable = AER or AIR-Severe + Unstable = bypass or AIR-Do not withhold ABC’s to rewarm

ACLS:-If in VF or pulseless VT, attempt defibrillation-“Might be reasonable to perform further defibs-“Might be reasonalbe to administer vasopressor”

Cold and Dead?

“Patients with severe accidental hypothermia and cardiac arrest may benefit from resuscitation even in

cases of prolonged downtime and prolonged cpr”

The Obvious:-Decapitation

-Non-compressible chest-Ice in mouth and nose

-DNR order

The Unreliable:-rigor or livor mortis

-fixed pupils-tissue deterioration

Rosens:“Significant predictors of outcome”

asphyxia, prehospital arrest, low or no BP, high BUN, need

for intubation in ER

Literature:

Mt. Hood: only survivors had signs of life on scene, temps were above 20 degrees, K < 7

Mair et al. 1994: K > 10, pH < 6.5,

Others: fibrinogen <50mg/dL, ammonia >250mmol/L

Frostbite

Case:

In minor ER

63 M

Pernio

• Local, inflammatory, bluish-red lesions

• Caused by prolonged vasoconstriction

• Gentle drying and massaging.

Immersion Injury (Trench Foot)

Cold Injury

Non-Freezing

• Pernio• Immersion Injury

• Cold Urticaria

Freezing

• Frostnip• Frostbite

Frostnip

Reversible and superficial

No tissue loss

Pale and discomfort and tingling

Case:

27 F Car broke down on a rural road.Decided to walk out

While walking through wooded area, she gets lost, at one point ending up knee deep in a stream.

She wanders through the forest for 12 hours lost.

Eventually she is spotted by a hunter who calls EMS.

Frostbite

Classification

Treatment

• Remove wet clothing• Rapid rewarming with warm water (40

degrees)• Analgesia!!• NSAID’s?• Td

Treatment

• Thawing:– 40 degrees– Until part feels soft, erythema present– Usually requires 10-30 minutes– Active motion by patient

Treatment

• Post-thaw:– Elevate– Sterile, bulky dressing– Aloe Vera?– Blisters?– TPA?– Heparin?– Abx?– Hyperbaric O2?, Pentoxifylline?

Treatment

• Surgery?

• Admission?

Summary

1) Spectrum of freezing and non-freezing injuries

2) Treat by rapid rewarming

3) Aloe, ibuprofen, and Td (others are controversial)