Cold Weather Emergencies

Victor Politi, M.D., FACP

Medical Director -

SVCMV-Physician Assistant Program

The Case of Tommy 23h10 Call from MD working in James Bay Male, 27 y.o. Unresponsive. Found in snow, cross-country skiing Normal Airway. Breathing. O2 sat. Femoral pulse + (35) BP. GCS=3 TR = 28C. IV. Monitor. Mask with 100% O2

Frostbite

The Case of Tommy…

Friend told MD: PMH. Rx. drugs. EtOH

Major foot deformity Looks like fell in ski and could not return

home by himself… MD has some questions for you…

The Case of Tommy…

Should he intubate? Are there risks to precipitate dysrythmias?

• Cold myocardium prone to arythmias?

How should he rewarm the patient?• Danger of afterdrop?

He wants an ABG but should he ask for the blood to be warmed to normal T for analysis…or it doesn’t matter?

Answer: You’ll call him back…

The Case of Tommy… MD calls you back 30 minutes later Pt in cardiac arrest : V.fib. Now 27C 3 shocks Epinephrine + re-shock Having Amiodarone prepared… How long should he do CPR and

rescussitation?

Anything wrong ?Answer ?

Introduction

EtOH Mental illness Homelessness Province of Quebec Cold

Plan

Definitions Physiology Pathophysiology Labs findings : ABG, ECG Rewarming methods Afterdrop ACLS 2000 guidelines

Definitions

Primary VS Secondary Primary

– Normal thermoregulation– Overwhelming cold exposure

Secondary– Abnormal thermogenesis– Multiple causes

Definitions

Hypothermia : < 35C

Mild : 32-35C Moderate : 28-32C Severe : < 28C

Physiology: Heat production

Basal metabolism (Metabolic rate)– Heart / Liver

Anterior hypothalamus Thyroid / Sympathetic Preshivering muscle tone (2x) Shivering (2-5x) Posterior hypothalamus

Physiology: Heat dissipation

Radiation (55-65%)• Gradient between environement and exposed

body area.

Conduction (2-3%)• Direct contact with cold substance

Convection (10-15%)• Wind…

Evaporation (20-35%)

Physiology…

Above 32C:– Vasoconstriction– Shivering– Basal metabolic rate

Below 32C:– No shivering

Below 24C:– No basal metabolic rate

Pathophysiology

Cardiovascular– Initial tachycardia– Gradual bradycardia : HR 50% at 28C.– Not consistent ?

• Hypoglycemia, intoxication, hypovolemia,…?

– Refractory to atropine BP CI– A.fib (T < 32C)– V.fib (T < 28C)

Pathophysiology…

CNS– Cerebral metabolism 6% / 1C– Normal autoregulation until 25C– EEG flat at 19C

Renal– Cold diuresis

• Peripheral vasoconstriction• Failure to reabsorb Na+ and water.

Pathophysiology…

Respiratory– CO2 production 50% at 30C

– Decreased RR– ARDS possible

Hematology– Hemostasis and coagulation impaired– Problems with CPB

Mild (> 32C)

Increase metabolic rate Maximum shivering thermogenesis Amnesia / dysarthria / ataxia Loss of coordination Tachycardic, tachypneic Normal BP

Moderate (28– 32C)

Stupor No shivering Bradycardic / A.fib BP RR Pupils dilated (< 30C)

Severe (<28C ) Coma No corneal or oculocephalic

reflexes BP V.fib (Maximum risk: 22C) Apnea Asystole Areflexia / fixed pupils Flat EEG (19C)

Lab findings : ECG

Woman, 75 y.o Found unconscious in her apartment

Osborn (J) Wave

Mr. John J. Osborn in the early ’50’s.

When T< 33C 25%-30% of patients Positive-negative

deflection

Osborn JJ: Experimental hypothermia: respiratory and blood pH changes in relation to cardiac function. Am J Physiol 1953; 175:389.

Osborne (J) Wave…

Amplitude proportionnal to degree of hypothermia

Usually V3-V6 At junction of QRS

and ST segment

Osborn JJ: Experimental hypothermia: respiratory and blood pH changes in relation to cardiac function. Am J Physiol 1953; 175:389.

ECG in Hypothermia

Muscle tremors artifacts Early changes

– Bradycardia– T wave inversion– Prolonged PR, QRS and QT intervals

A.fib when T < 32C V.fib when T < 28C

Lab findings : ABG Man, 45 y.o,. Rectal T= 30C. LOC Intubated. Acid-base status? Technician asks you if he should

warm the blood before analysis…A) Don’t warm it : 30CB) Warm it to 37CC) heu…(30+37)/2….33.5CD) Both and I’ll pick the best one.

ABG in Hypothermia

1st ABG (30C):• pH = 7.5• pCO2 = 27

2nd ABG (37C):• pH = 7.4• pCO2 = 40

Which one do you pick? Will you try to RR or VT to pCO2 ? Everything’s perfect, I don’t touch the

ventilator ? The answer ? ….

The Good One !!!

ABG in Hypothermia……the rationale pH of water at any given T defines

neutrality H2O H+ + OH- As T , less free H+ and OH- are

generated and pH of neutrality . As T , CO2 content is the same but

pCO2 .Delaney KA and al. Assessment of Acid-Base Disturbances in Hypothermia and their physiologic consequences. Ann Emerg Med, Jan 1989; 18:72-82.

So…

1st ABG (30C):• pH = 7.5

• pCO2 = 27

2nd ABG (37C):• pH = 7.4

• pCO2 = 40

ABG in Hypothermia……the rationale

ABG machines usually warms blood to 37C.

So use the UNCORRECTED ABG for normal T .

Delaney KA and al. Assessment of Acid-Base Disturbances in Hypothermia and their physiologic consequences. Ann Emerg Med, Jan 1989; 18:72-82.

Rewarming methods :Passive rewarming Endogenous heat production

– Shivering, metabolic rate, TSH, sympathetic,…

Involves decreasing heat loss– Remove from cold environnement– Remove wet clothes– Provide blanket

Passive rewarming…

O2 consumption can > 90%

CO2 production can by 65% Possible anaerobic metabolism

Rewarming rate : 0.5C - 2.0C /h Method of choice for mild

hypothermia Adjunt for moderate hypothermia

Rewarming methods :Active external rewarming Heat to body surfaces

– Heating blankets (fluid filled)– Air blankets– Radiant warmers– Immersion in hot bath– Water bottles / Heating pads

Less effective than internal rewarming if vasoconstricted +++

Active external rewarming…

Concern about afterdrop. Rewarming rates : 1C – 2.5C / h Circulatory problem may be by

applying devices to trunk only. Very few prospective controlled

study comparing methods.

Forced Air Blankets

ED patients Moderate to severe hypothermia (< 32C) Exclusion criteria

– Cardiac arrest– Hypothalamic lesions

16 patients Randomized to passive insulation with cotton

blanket or forced air blanket @ 43C .

Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.

Forced Air Blanket…

All patients: warm iv fluids @ 38C Warm O2 (40C) End point: T = 35C Looked at:

– Rates of rewarming– Skin damage by blankets

Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.

Forced Air Blanket…

Results No afterdrop in both groups No skin erythema/damage Rewarming rates (p=0.01)

– Forced-Air: 2.4C / h– Regular blanket: 1.4C / h

Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.

Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann Emerg Med, April 1996; 27:479-484.

Forced air

Electrical heating blanket

Carbon fiber-resistive blanket VS Passive rewarming

8 patients Induced-hypothermia (33C) Skin thermal flux transducer CO2 concentration production through mask Compared:

– rates of rewarming– core heat content

Greif R and al, Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.

Electrical heatingResults

Core heat content >> electrical heating

Rates 1.5C/h > with electical heating

No afterdrop both groups

Greif R and al, Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.

Rewarming methods :Active internal (core) rewarming

Warm iv fluids Warm, humid oxygen Peritoneal lavage Gastric / Esophageal lavage Bladder / Rectal lavage Pleural / Mediastinal lavage Microwaves (Diathermy) Extracorporeal circulatory

rewarming

Warm iv fluids Up to 45C shown to be safe 65C fluid studied in dogs

– Journal of Trauma 1993 (8 dogs)– American Journal of Surgery 1996 (10

dogs)– Through IVC – Safe. No Complications– 2.9C/h compared to 1.25C/h (J Trauma)– 3.7C/h compared to 1.75C/h (Am J Surg)

Warm iv fluids… Saline…Not RL Long tubulure = lost of heat Can use microwave for saline (No D5W)

– Annals of EM, 1984 and 1985

– 1L of NS to 39C : 2 minutes at high power. No microwave rewarming for PRBC

– Hemolysis

– Hemoglobinuria

– Transfusion reaction

Warm, humidified O2

42C-46C Prevent heat loss Negligible heat gain Very important in management of

hypothermic patient:– Up to 30% of heat production lost through

airway.

Gastric/Oesophageal/ Bladder/Rectal lavage

Not shown to be better than external rewarming.

Limited surface area Limited heat exchange Limited utility (!) Recommend as last resort when other

modalities not available.

Peritoneal lavage Fluid at 40-45C Up to 12 L/h KCl free Hepatic rewarming Renal support when dialysate is used 2C-4C / h C.I.

– Abdominal trauma– Acute abdomen– Free intra-abdominal air

Pleural lavageClosed-thoracic lavageContinuous thoracic cavity lavage

Two large (38F) ipsilateral chest tubes 1: 2nd or 3rd anterior intercostal space,

midclavicular. 2: 5th or 6th intercostal space, posterior axillary

line. NS or tap water @ 42C Rewarms heart + greater vessels

Hall KN and al. Closed thoracic cavity lavage in the treatment of severe hypothermia in human beings. Ann Emerg Med, Feb 1990;19:204-206.

Mediastinal lavage

Requires certain expertise Limited clinical experience Case reports Internal cardiac massage 8C / h

Douglas D. Brunette, Hypothermic cardiac arrest: An 11 year review of ED management and outcome. Am J Emerg Med 2000; 18:418-422.

Extracorporeal blood rewarming techniques

Hemodialysis Arteriovenous rewarming Venovenous rewarming Cardiopulmonary bypass

Extracorporeal blood rewarming…

- Hemodialysis : renal dysfunction- AV depends on the pt’s BP- CPB is the « Gold Standard ».- CPB improves long term survival and

neurologic outcome.- 15 of 32 long term survivors and none had

neurologic deficits (7 years later).

B.H. Walpoth and al. Outcome of survivors of accidental deep hypothermia and circulatory arrest treated with extracorporeal blood warming, N Engl J Med, 1997;337:1500-5

Diathermy Ultrasonic waves Microwaves Short waves Few studies Radio wave regional hyperthermia:

Experience with Tx of tumors. Not widespread because of

dosages in human poorly defined.

Diathermy… Prospective Radio Wave vs.

Peritoneal lavage 6 dogs Rate of

rewarming 3x > for Radio wave.

J.D. White and al. Controlled comparison of Radio Wave regional hyperthermia and peritoneal lavage rewarming after immersion hypthermia, J Trauma, 1985; (25)10: 989-993.

The Afterdrop Phenomenon Continued fall in deep core T during the initial

period of rewarming. First described by James Currie in 1798 Theory of Burton and Edholm (1955):

– Attributed to peripheral vasodilatation– Return of cold blood to central circulation– Cooling of myocardium

Accepted theory until mid ’80’s

Burton, A.C., and O.G. Edholm. Man in Cold Environment. London: Arnold, 1955, p.216.

Paul Webb,An alternative explanation.J. Appl. Physiol. 1986

Fall of T during active rewarming:– Up to 2C– 10 – 30 min

Used calorimeter, rectal, esophageal and tympanic probes.

Heat loss calculation

Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986.

2 mecanisms for afterdrop Convection mecanism

– Return of cold blood from periphery– Minimal is any contribution

Conduction mecanism– Thermal gradient principal– Heat flow principal

Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986.

Skin/Tissues

Blood vessel

Environement

Heat transfer

Conduction Mecanism

Heat transfer

Afterdrop: an alternative explanation Active external rewarming increase

threat of further cooling of the heart…as much as thought before.

Correlated by many other papers

•Savard, G.K., K.E. Cooper, W.L. Veale, and T.J. Malkinson. Peripheral blood flow during rewarming from mild hypothermia in humans. J. Appl. Physiol. 58(1): 4-13, 1985.

•Romet, Tiit T. Mechanism of afterdrop after cold water immersion. J.Appl.Physiol. 65(4): 1535-1538, 1988.

Freezing Injury Cascade

Prefreeze phase Freeze-thaw phase Vascular stasis and progressive

ischemia

After stabilizing core temperature and addressing associated conditions -prepare to initiate rapid thawing

Protect part Stabilize core temperature Hydration No friction massage

In The ED - Prethaw

In the ED - Thaw

Rapid rewarming in 38-410 C circulating water until distal flush (thermometer monitoring)

Requires 10-30 min with active motion of part without friction massage

Parenteral analgesia

In the ED - Postthaw

Clear vesicles -aspirate (if intact) vs. debride

Hemorrhagic vesicles - aspirate Apply topical aloe vera (Dermaide)q6h Ibuprofen 400mg q 12h Tetanus prophylaxis Streptococcal prophylaxis for 48-72hr Elevation

Management: ED issues

Intubation General belief it can induce arythmias Danzl, Multicenter Hypothermia Survey,

Annals Emerg Med, Sept.87.– Data from 13 ED– 428 cases– 117 intubation– NO arythmias

Management: ED issuesBretylium

Recommended for V.fib in hypothermia Removed from new ACLS 2000:

availability and limited supply occurrence of side effects

Still recommend in textbooks (Rosen) Recommended by US Wilderness

Emergency Medical Services Institute Based on Dogs studies Good for prophylaxis only

Management: ED issues

Drugs / Shocks NO drugs if T < 30C

– Not efficacious– Not metabolised

If > 30C, intervals between doses

If < 30C and failure of 3 shocks

Defer subsequent shock + Rx until T > 30C

Sequelae

Neuropathic pain

– phantom– causalgia– “Tabes” burning– chronic

Sequelae

Thermal sensitivity– heat– cold

Sensation– hypesthesia– dysesthesia– paresthesia– anesthesia

Sequelae

Autonomic dysfunction– Hyperhidrosis– Raynaud’s

Musculoskeletal– atrophy,compartment syndrome– rhabdomyolysis, tenosynovitis, stricture– epiphyseal fusion, osteoarthritis– osteolytic lesions,necrosis,amputation

Sequelae

Dermatologic– edema– lymphedema– chronic/recurrent ulcers– epidermoid/squamous carcinoma– hair/nail deformities

Sequelae

Miscellaneous– core temperature afterdrop– acute tubular necrosis– electrolyte fluxes– psychic stress– gangrene– sepsis

Conclusion

Hypothermia is rare but treatable Good outcome after prolonged

arrests Include Hypothermia in your Dx Include T as a 5th vital sign… Call early to organize CPB if

available if patient in cardiac arrest Prevention is still the best

Other Causes of Hypothermia

The Alcatraz/San Francisco Swim Study San Francisco Bay…contest… Swims from Alcatraz Island to shore No wetsuits or protective clothing Water T = 12C (53F) Outside : T = 10C 3 Km 11 subjects for study 23 y.o to 70 y.o (!) Measured T after contest.

Thomas J. Nuckton and al. Hypothermia and afterdrop following open water swimming: The Alcatrax/San Francisco Swim Study. Am J Emerg Med 2000; 18:703-707.

Afterdrop conclusion Rectal T lags behing esophageal T

and is often > than esophageal and pulmonary T.

Think about it but you can probably not prevent it.

Issue with active external rewarming Other concerns about external

rewarming:– Acidosis– Hypotension

Questions ???