Accidental Hypothermia Cass Djurfors May 8, 2003.

Accidental Hypothermia

Cass DjurforsMay 8, 2003

Case

• Three avalanche workers caught in an avalanche

• One partially buried called on radio repeater immediately to mobilize rescue team and local paramedics by helicopter

• Plan to fly direct to local ED (Scene beyond range of STARS without refuel and nearby fuel cache buried in winter snow)

• Other two completely buried

Case

• Partially buried victim pulls shovel from rucksack on back and digs self out, performs transceiver search to locate first buried who comes up breathing

• Continues search and digs up second buried who is VSA and so begins CPR

• Burial time 40 minutes.

Case

• Paramedics land and apply monitor pads to show sinus bradycardia, confirm VSA, continue CPR

• Endotracheal intubation, bundle and fly to nearby regional ED

• Sinus bradycardia deteriorates en route to ventricular fibrillation

• Pilot does not allow defibrillation in flight

Case

• Local ED prepared with 2 EP’s, 1 anaesthetist, 1 GP surgeon, 7 nurses, various support personnel

• Patient arrives asystolic• Initial esophageal temp probe

27.5oC

Case• Management as follows:

– Confirm ETT placement– Humidified O2– 1L NS at 41C by Level One Infuser– Switch Level One Infuser to 3l NS irrigation bags for

pleural lavage via 36F tube left 2nd intercostal space and second tube 5th intercostal space

– Peritoneal lavage– Bladder irrigation – Alternating all three active internal rewarming

modalities between two Infuser chambers allowing dwell time for all 3 modes

– Maximum outflow temp from Infuser approx 41C

Case

• Meanwhile…– Team leader calls Trauma Centre intensivist re:

transfer for CPB– Intensivist unclear as to whether CPB warranted

in this case and states “will call back”– Aggressive rewarming continues to produce a

rise to 28.5C after 30 minutes– Intensivist calls back to recommend rapid

transport for CP bypass – Patient transported by ground (now dark

outside) to nearest Trauma Centre

Case

– CPB initiated– Patient rapidly warms with return of

spontaneous circulation– Proceeds to develop MODS that

results in death shortly after

Issues from Case

• Resuscitation of hypothermic patient:– CPR– ACLS– Defibrillation– Medications

• Core temperature measurement• Rewarming methods, rates, logistics

and their indications• Prognostic markers of death in

hypothermia

Definitions

• Temperature < 35 C– Mild 32-35 C– Moderate 28-32 C– Severe < 28 C

• Primary (cold exposure) • Secondary (disease process, eg. Myxedema)• Acute (rural, outdoor hypothermia)• Chronic (urban, indoor, elderly hypothermia)• Immersion vs. non-immersion (degree of

rapidity)

Epidemiology

• 723 deaths per year US 1979-1995• 50% older than 65• Male:female 3:1• Socioeconomic factors• Mentally ill 5 times greater risk

Mechanisms of Heat Loss

Mechanism Approximate % of Heat Loss

Radiation 50

Convection 30

Evaporation 15

Conduction 5

Physiology: Mild

• 37.6 normal rectal temperature• 37.0 normal oral temperature• 36.0 ↑ metabolic rate, bp, and muscle

tone• 35.0 maximum shivering • 34.0 amnesia, poor judgment • 33.3 Ataxia, apathy; cold diuresis

Danzl DF. Accidental hypothermia. Wilderness Medicine

Physiology: Moderate

• 32.0 stupor• 31.0 shivering stops• 30.0 poikilothermia; arrhythmias

develop• 29.0 ↓ LOC, HR and RR; dilated pupils


Physiology: Severe

• 28.0 ↓ VF threshold; hypoventilation• 26.0 no response to pain• 25.0 cerebral autoregulation fails,

spontaneous VF and asystole• 24.0 hypotension and bradycardia• 23.0 areflexic (incl. corneal and doll’s

eye)• 22.0 max VF riskDanzl DF. Accidental hypothermia. Wilderness Medicine

Physiology: Profound

• 20.0 lowest resumption of cardiac activity

• 19.0 EEG silent• 13.7 lowest adult accidental

hypothermia survivor Gilbert et al. Resuscitation from accidental hypothermia of 13.7oC with circulatory arrest. Lancet 355: 375, 2000.

• 9.0 lowest therapeutic hypothermia survivor Niazi et al. Profound hypothermia in Man: Report of a case. Annals of surgery. 147(2): 26466, 1958.


Causes of Hypothermia1. Decreased Heat

Production– Neuromuscular

inefficiency• Impaired shivering• Age• Immobility / inactivity

– Endocrine failure• Hypopit• Hypothyroid• Adrenal insuff

– Nutritional• Hypoglycemia• Anorexia• Malnutrition

2. Increased Heat Loss– Exposure / Immersion– Dermatologic

• Erythroderma• Burns / TENS• Psoriasis)

– Vasodilation• ETOH• Toxins

– Iatrogenic• Emergent deliveries• Cold infusion

Hanania, NA et al. Accidental Hypothermia. Critical Care Clinics. 15(2): 236-49, 1999

Causes of Hypothermia

3. Impaired Thermoregulation – Drugs

• Sedatives• Barbiturates• EtOH• TCA

– Peripheral neuropathy– SCI– DM– CNS bleed / trauma– Parkinson's– Anorexia nervosa

4. Miscellaneous– Sepsis– Pancreatitis– Carcinomatosis– Uremia– Vascular insufficiency

Hanania, NA et al. Accidental Hypothermia. Critical Care Clinics. 15(2): 236-49, 1999

Diagnosis

• High index of suspicion• Low reading thermometer

Temperature measurement

• Need an accurate approximation of core temperature

• Traditionally rectal (at least 10-15cm)• Rectal temperature lags behind core:

especially during rapid change, cooling to warming transition(Terndrup TE. An appraisal of temperature assessment by infrared emission detection tympanic thermometry. Ann Emerg Med 21:1483-1492, 1992)


• Direct tympanic thermometry is research standard, but not convenient for ER use

• Indirect infrared tympanic thermometry:– often doesn’t read below 34oC– Susceptible to cerumen or water in

the canal


• Esophageal– Falsely elevated with heated inhalation

• Bladder– Falsely elevated with peritoneal lavage– Falsely low with cold diuresis

• Oral– Found to be comparable to tympanic probe

in “hypothermic” trauma patients 35.2-35.6Kober A et al. Effectiveness of resistive heating compared with passive warming in treating hypothermia

associated with minor trauma: a randomized trial. Mayo Clin Proc;. 76:369-75, 2001.

Diagnosis: Lab

• ABG’s:– Controversy of historical interest only– Curve shifts left with colder temps causing

pH to be reported lower and O2, CO2 to be reported as higher than actual

– Blood gas analyzer runs samples at 37oC– Current consensus is that use of uncorrected

values provides better outcomesCorneli HM. Environmental Emergencies. Clinical Pediatric Emergency Medicine. 2(3):179-91, 2001.

Lab

• Coags may be reported as normal if run at 37oC despite obvious clinical coagulopathy

• Electrolyte abnormalities are common and should be addressed

• Hypoglycemia should be treated

The J or Osborne Wave

• Deflection of the J point: the junction of the QRS complex and ST segment

• Most common in leads II and V6• Diagnostic but not prognostic• Not pathognomonic: can also occur in CNS

lesions, focal cardiac ischemia and sepsis• Magnitude of J wave inversely correlates

with temperature Susi U et al. A prospective evaluation of the electrocardiographic manifestations of hypothermia. Academic Emergency Medicine: 6(11); 1121-26, 1999.

Other ECG findingsMattu A et al. Electrocardiographic Manifestations of Hypothermia. American

Journal of Emergency Medicine. 20(4); 314-26

• Artifact produced by clinically invisible preshivering muscle tone may obscure P waves

• Any arrhythmia (atrial or ventricular) is possible

• Bradycardia, Afib, VF asystole common• Treatment of Afib with anticoagulants has not

been studied and should not be undertaken• ECG changes resembling ischemia can occur

and should only be treated with rewarming

Basic Management: ABC’s

• A/B:– Supplemental O2, consider ETT– Neuromuscular blocks ineffective < 30 C– May have to use nasotracheal approach if rigid – Unlikely to induce arrhythmias with ETT

• C:– Continuous monitoring; usually volume depleted– Peripheral lines ideal; Central may precipitate dysrythmias– Avoid PA catheters under 32 C – Bolus in 250-500 cc increments with glucose checks and

5% dextrose if necessary– Theoretically avoid ringers lactate due to impaired liver– <32 C all fluids warmed to 40 to 42 C

Basic Management: ABC’s

• Remove wet clothing• Avoid rough movement as this

may precipitate VF• Nasogastric tube to relieve

distension• Foley for monitoring

ACLS in Hypothermia2000 AHA Guidelines

• For absent pulse or respirations– Start CPR– Defibrillate VF/Pulseless VT with

MAXIMUM of 3 shocks 200, 300, 360– Secure airway, ventilate with warm

humidified oxygen, start IV with warmed NS


• For core temperature>30oC– CPR– IV meds as per ACLS but with

extended dosing intervals– Repeats defibrillation attempts as

temp rises


• For core temperature<30oC– CPR– Withhold IV meds– No further shocks– Proceed with active rewarming

CPR

• Can be difficult due to chest wall inelasticity

• Optimal rate unknown• Tissue decomposition, rigor

mortis, fixed and dilated pupils are NOT indications to withhold CPR

Defibrillation

• Hypothermia is known to alter ion channel function and hence alter defibrillation efficacy

• Several case reports suggest hypothermia impairs defibrillation leading to traditional belief that defibrillation is largely ineffective below 28oC

Defibrillation

• Case reports of hypothermic VF responsive to defibrillation do exist:– Thomas et al. Successful defibrillation in profound

hypothermia. Resuscitation. 47(3): 317-20, 2000.• Successful defibrillation of hypothermic patient with core body

temperature of 25.6oC

– Cortes et al. Severe accidental hypothermia: rewarming by total cardiopulmonary bypass. Revista Espanola de Anestesiologia y Reanimacion. 41(2):109-12, 1994.

• 20-year-old male with profound hypothermia (26oC presented in deep coma with recurring ventricular fibrillation that yielded to electrical defibrillation once a core temperature of 27.4oC was reached

DefibrillationUjhelyi et al. Defibrillation energy requirements and electrical heterogeneity during

total body hypothermia. Critical Care Medicine: 29(5), 2001.

• Animal study• Compared normothermia with

hypothermia of 30oC• Induced brief VF• No change in defibrillation energy

requirements in hypothermia• Fibrillatory threshold noted to be

reduced

Defibrillation

• Bottom Line:– Attempt a maximum of three shocks

at standard energy settings (200J, 300J, 360J) in the hypothermic VF or pulseless VT patient with core body temperature below 30oC

Pacing?Dixon et al. Transcutaneous pacing in a hypothermic dog model. Annals of

Emergency Medicine. 29(5): 602-6, 1997.

• 20 mongrel dogs core temperature of 27oC

• TCP restored and maintained hemodynamic stability and allowed the hypothermic animals to rewarm in half the time required by their nonpaced counterparts

• No human studies

Medications in Hypothermic Arrest

• Generally reported to be ineffective and possibly even harmfulCorneli HM. Environmental Emergencies. Clinical Pediatric Emergency Medicine. 2(3):179-91, 2001.

• Bretylium, lidocaine, vasopressors all studied with no consensus

• Kornberger et al. Effects of epinephrine in a pig model of hypothermic cardiac arrest and closed-chest cardiopulmonary resuscitation combined with active rewarming. Resuscitation. 50(3):301-8, 2001.– Epinephrine did not improve time to spontaneous

perfusion, and even worsened mixed venous hypercarbic acidosis.

Medications in Hypothermic Arrest

• Bottom line:– Avoid in core temp <30oC

Rewarming Methods: Issues

• Severe hypothermia is uncommon• No RCT’s exist in accidental hypothermia• Evidence is primarily from case reports• Rapid rewarming, while intuitive, has

never been proven to improve outcomes• Human experimental model unethical

below 35oC• Risky to blindly generalize results of

animal studies to humans

Rewarming Methods: Issues

• Rigid treatment protocols are inherently hazardous

• Clinical circumstances and availability of resources have to be taken into account

Core Temperature Afterdrop

• The continued decline in a hypothermic patient’s temperature after removal from the cold

• Cause is temperature equilibration between the warmer core and cooler periphery and countercurrent cooling of blood perfusing the cold extremities

• Ideally, rewarming strategies would avoid significant afterdrop

Rewarming Methods

1. Passive external rewarming2. Active rewarming

1. Active external rewarming2. Active core rewarming

Passive External Rewarming

• Involves covering patient with insulating material to prevent further heat loss

• Indicated mainly for mild hypothermia or as an adjunct in moderate to severe hypothermia

• Patient must have endogenous thermogenesis– Humans are poikilothermic below 30oC– Shivering stops below 32oC

• Rewarming rates in mild hypothermia with PER range from 0.5-2.0oC/hrHanania et al. Accidental Hypothermia. Critical Care Clinics. 15(2):236-48, 1999

Active Rewarming

• Direct transfer of exogenous heat to the patient

• Internal or external techniques• Indications:

– Poikilothermia (T< 32oC)– Cardiovascular instability– Inadequate rate or failure to rewarm– Endocrine insufficiency– Traumatic or toxicologic peripheral vasodilation– Secondary hypothermia impairing thermoregulation– Neonatal or infant patients

Active External Rewarming

• Exogenous heat is delivered directly to the skin

• Forced air rewarming• Warming blankets or heating pads• Immersion • Arteriovenous anastomoses

rewarming

Forced Air Rewarming

• e.g. Bair Hugger• Theoretical concern: vasodilation

in extremities could transport cooler blood back to core causing afterdrop and rewarming shock

• Advantages: easy to use, readily available, low cost, noninvasive

Forced Air Rewarming

• Has been used successfully in accidental hypothermia (including profound) without evidence of afterdrop or rewarming shock

• Usually in conjunction with warmed IV fluids and heated inhalation

• Rewarming rates between 1 to 4.4oC/hr

De Caen, A. Management of profound hypothermia in children without the use of extracorporeal life support therapy. The Lancet. 360:1394-95, 2002.

Koller R, Schnider TW, Neidhart P: Deep accidental hypothermia and cardiac arrest--rewarming with forced air. Acta Anaesthesiol Scand 41:1359, 1997

Roggla et al. Severe accidental hypothermia with or without hemodynamic instability: rewarming without the use of extracorporeal circulation. Wiener Klinische Wochenschrift. 114(8-0):315-20, 2002

Steele et al. Forced air speeds rewarming in accidental hypothermia. Ann Emerg Med. 27:479, 1996

Immersion

• Impractical in ER setting• Makes monitoring and CPR

impossible

Arteriovenous Anastomoses Rewarming

• Originally described by Vangaard in 1979• Exogenous heat provided by immersion of

lower parts of extremities (hands, feet, forearms and calves) in 44-45oC water

• Mechanism: – Heat opens arteriovenous anastomoses that exist

1mm below epidermal surface in digits– Results in increased flow of warmed venous SC

blood returning to heart– Countercurrent heat loss is minimized as superficial

veins are distant from arteries

• Theoretically should minimize afterdrop

Vanggaard L et al. Immersion of distal arms and legs in warm water (AVA

rewarming) effectively rewarms mildly hypothermic humans. Space and

Environmental Medicine. 70(11):1081-8, 1999

• Voluntary mildly hypothermic subjects warmed comfortably with AVA technique at a rate of 9.9+/-3.2 degrees C with minimal afterdrop

Diathermy

• Experimental technique involving transmission of heat by ultrasonic and low frequency microwave radiation

• Animal studies promising

Active Core Rewarming

• Heated inhalation• Heated infusion• Lavage

– Gastric– Colonic– Mediastinal– Thoracic– Peritoneal– Bladder

• Hemodialysis• Extracorporeal methods

Heated Inhalation

• Must be humidified as dry air has little thermal conductivity

• 40-45oC• Although rewarming rates have

been reported at 1-2.5oC/hr, primary aim is to reduce respiratory heat loss

Warmed IV Fluids

• Cold fluid resuscitation is well known to induce hypothermia in previously normothermic trauma patientsKashuk et al. Major abdominal vascular trauma: a unified approach. J trauma. 22:672, 1982

• Heat IV fluids to 40-42oC• Conductive heat loss is significant

through long IV tubing esp. at low rates• Level 1 Fluid Warmer ideal• In theory, 1 L of fluid at 42oC should

warm a 70kg patient at 28oC by 0.33oC

Warmed IV Fluids

• New research into superheated fluids at 65oC

• Central infusion• Animal studies• No apparent complications• More work needs to be done

Fildes et al. Very hot intravenous fluid in the treatment of hypothermia. J trauma. 35:683, 1993.Sheaff et al. Safety of 65oC intravenous fluid for the treatment of hypothermia. Am J Surg. 172:52, 1996.

Heated Irrigation

• Gastric, colonic, bladder– Limited surface area for heat transfer– Gastric lavage may be complicated by

aspiration– Average rewarming rates of 1.5-2oC/hr

Hanania et al. Accidental Hypothermia. Critical Care Clinics. 15(2):236-48, 1999


Peritoneal Lavage

• 40-45oC dialysate via minilaparotomy or percutaneous puncture

• Flow rates of ~6 L/hr• Rewarming rates of 1-3oC/hr• Electrolytes must be carefully

monitored

Closed Thoracic Lavage

• Procedure:– Two 36-40F thoracostomy tubes placed in

one or both hemithoraces– Anterior second or third intercostal space at

midclavicular line– Posterior axillary line at fifth to sixth

intercostal space– Infuse NS at 40-42oC into anterior tube,

drain by suction or gravity from posterior tube

Closed Thoracic Lavage

• Potentially hazardous in the non-arrest patient (precipitate VF)

• Clinical experience is limited• Rewarming rates average 3-6oC /hr• Ensure adequate drainage or tension

hydrothorax will ensue

Kangas et al. Treatment of hypothermic circulatory arrest with thoracotomy and pleural lavage. Annales Chirurgiae et Gynaecologiae. 83(3):258-60, 1994.

Winegard C. Successful treatment of severe hypothermia and prolonged cardiac arrest with closed thoracic cavity lavage.] Journal of Emergency Medicine. 15(5):629-32, 1997.

Danzl DF. Accidental hypothermia. Wilderness Medicine. P159.

Mediastinal Irrigation

• Standard left thoracotomy• Irrigation of mediastinum with 40oC fluid• Also allows for direct cardiac compression

and direct defibrillation• Only indicated in cardiac arrest• One uncontrolled, nonrandomized review

reported favourable results with ED thoracotomy +/- CPB compared to immediate CPB aloneBrunette et al. Hypothermic cardiac arrest: an 11 year review of ED management and outcome. Am J Emerg Med. 18(4): 418-22, 2000.

Extracorporeal Rewarming

• Hemodialysis• Arteriovenous rewarming• Venovenous rewarming• Cardiopulmonary bypass

Extracorporeal Rewarming

• Complications– Vascular injury– Air embolism– Pulmonary edema– Coagulopathy

• Contraindications– DNR order or obviously lethal injuries present– Lack of venous return– Intravascular clots or slush

Hemodialysis

• Best for stable patients with renal failure or dialyzable toxin

• Has been reported in the literature in a known dialysis patient who suffered cold exposure leading to core temp or 24.9oC. Warmed hemodialysis was performed for an average temperature rise of 1.9oC/hrOwda A. Osama S. Hemodialysis in management of hypothermia. American Journal of Kidney

Diseases. 38(2):E8, 2001 Aug

Arteriovenous Rewarming

• Femoral artery and contralateral femoral venous catheters

• Countercurrent fluid warming• Required SBP>60mmHg• Heparinization• Rates of 3-4oC/hr

Venovenous Rewarming

• Countercurrent fluid warming with roller pump

• Warmed blood is removed from central line then returned by a second IV site

• No circulatory support

Cardiopulmonary Bypass

• Considered gold standard of rewarming hypothermic arrest patients

• Preserves oxygenated flow in patients without mechanical cardiac activity

• Fastest of all rewarming strategies at 1-2oC every 3 to 5 minutes!!!


• Can be lifesaving in cases of profound hypothermia with prolonged arrest times– Walpoth et al 1997: 32 arrest patients with mean

T=21.8 rewarmed with CPB. 15 long term survivors– Schwarz et al 2000: 5 arrest patients treated with CPB,

2 survived– Gilbert et al 2000: 1 arrest patient T=13.7, warmed

with CPB, survived– Althaus et al 1982: 3 severely hypothermic patients

treated with CPB: all recovered – Vretnar et al 1994: 68 hypothermic patients (61 arrest)

mean T=21 placed in CPB. 60% survived– Koller et al 1997: 5 patients (2 arrest) on CPB, all

survived


• Standard femoral artery-femoral vein CPB includes vascular catheters, mechanical pump, membrane or bubble oxygenator and heat exchanger

• Heparin-coated perfusion equipment has been developed and used successfully in patients with contraindications to heparinization

“No one is dead until they are warm and dead”

Prognostic Markers

• Survival is difficult to predict• Literature is littered with case reports of

dramatic saves• Mortality rate in severe hypothermia 40-75%• Wide variation in human physiologic

responses to hypothermia• Accurate triage markers of death are needed• No validated prognostic indicators in the

literature

Mair et al. Prognostic markers in patients with severe accidental

hypothermia and cardiocirculatory arrest. Resuscitation; 27:47-54,

1994• Retrospective study of 22 patients with severe

hypothermia and cardiac arrest treated with CPB• Found that in avalanche victims

– K>9 mmol/L– pH<6.50 (central venous)– Activated clotting time>400s

Were not compatible with re-establishment of circulation

• Results could not be applied to non-avalanche causes of hypothermia

Schaller et al. Hyperkalemia: a prognostic factor during acute

severe hypothermia. JAMA; 264: 1842, 1990.

• Retrospective review of 9 hypothermic avalanche victims and 15 hypothermic intoxications

• All avalanche victims were hyperkalemic (6.8-24.5) and none survived

• All intoxications were not hyperkalemic (2.7-5.3) and all survived

Segesser et al. Perfusion without systemic heparinization for

rewarming in accidental hypothermia. Ann Thoracic Surg.

52:560-561, 1991.

• Reports resuscitation of hypothermic patient with K=9.5 mmol/L

Wollnek et al. Cold water submersion and cardiac arrest in treatment of severe hypothermia

with cardiopulmonary bypass. Resuscitation; 52(3):255-63, 2002.

• Base excess, pH, K– Not reliable prognostic markers

Bottom Line

• Decision to continue or terminate resuscitative efforts in hypothermic arrest patients cannot at this time be based on lab values

• May be useful to guide judgment in situations of multiple victims with limited resources

CHR Protocol

• Mild hypothermia>32oC– External passive rewarming

• Warm blankets and environment

– External active rewarming:• Forced air warming blanket

– Internal rewarming• Warm IV fluids (<45oC)

CHR Protocol

• Moderate hypothermia 28-32oC with stable hemodynamics– External active rewarming:

• Forced air warming blanket

– Internal active rewarming:• Warm IV fluids• Consult ICU re:

– Warmed humidified ventilation– Hemodialysis with warm dialysate (esp if

intoxication suspected)

CHR Protocol

• Severe hypothermia <28oC or <32oC with unstable hemodynamics– Trauma team activation, Level 1– Consult CV surgery team:

• Surgeon, nursing staff, anesthetist, perfusionist and OR, anesthesia tech at 0050

• Take to trauma OR

CHR Protocol

• Severe hypothermia continued: hemodynamically stable– External active rewarming

• Forced air warming blanket

– Internal active rewarming• Warm IV fluids• Warmed humidified ventilation• Warmed peritoneal lavage• Place percutaneous femoral arterial and venous

catheters for extra-corporeal support access in case of hemodynamic deterioration

• If neurologic or other major bleeding injury ruled out, consider CPB even if stable with T<28oC

CHR Protocol

• Severe hypothermia continued: hemodynamically unstable: VT, VF, asystole– ACLS protocol– CPR– 1 series of 3 defibrillations at T<30oC – Withhold other rewarming strategies while

awaiting extra-corporeal support– Place percutaneous arterial and venous

cannulae if vessels accessed pre-arrest or cutdown if post-arrest

CHR Protocol

• Bypass protocol for severe hypothermia– Neurologic injury suspected

• Establish ECMO– Minimal dose heparin 0-3000U at time of cannulation– Heparin bonded extracorporeal circuit and oxygenator– Arterial and venous cannulae are not heparin bonded:

avoid stasis– Biomedicus pump– Heat exchanger– Heparin – ACT management: risk/benefit– Continue CPR until circulation established

CHR Protocol

• Bypass protocol for severe hypothermia– Neurologic injury not suspected

• Regular cardio-pulmonary bypass with full heparinization

• With femoral cannulation, LV decompression may be inadequate: continued CPR may be required until perfusing rhythm re-established

• Sternotomy for difficult femoral access and pediatric patients

Questions?

Accidental Hypothermia Cass Djurfors May 8, 2003.

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