Transcript Hypothermia - Hong Kong College of Emergency Medicine

HKCEM College Tutorial
Hypothermia
AUTHOR
DR. LAU CHU LEUNG, TERRY
AUGUST, 2013
Triage Notes
▪ F/91
▪ C/O: GE with vomiting / diarrhoea
Shock
Impaired
Consciousness
▪ PMH: HT
Hypothermia
▪ GCS E3 V4 M5
▪ BP 92/68 mmHg; P 48 bpm
▪ RR 10/min; SpO2 92% RA
▪ Temp. 33.2 ºC
Hypoxia
Triage Cat I
Bradycardia
What are your immediate management?
▪ Manage in Resuscitation Room & handle gently
▪ Stabilized ABC
▪ Oxygen
▪ Warm saline
▪ Monitoring – cardiac monitor, BP/P/GCS/SpO2, core temperature
▪ Prevent further heat loss
▪ Warm environment
▪ Remove wet clothes (if any as patient vomiting)
▪ Rewarming
▪ Ix
How to classify hypothermia?
Mild
•<35C
Moderate
•32 - 35C
Severe
•28 - 32C
Swiss Staging System
Hypothermia – Predisposing Factors
Core Temperature
Body Heat Loss - Mechanism
▪ Radiation (50+ %)
▪ secondary to infrared heat emission
▪ head and noninsulated areas of the body
▪ most rapid
▪ Conduction
▪ Transfer of heat via direct contact
▪ Important mechanism in immersion incidents
▪ thermal conductivity of water is approximately 30 times that of air
▪ Convection – air currents
▪ movement of fluid or gas, carrying significantly more heat away from the body in windy conditions by rapidly
removing the warm, insulating layer of air that initially is in direct contact with the skin
▪ Evaporation - evaporation of water from the body
▪ Respiration
Hypothermia - Classification
▪ Accidental
▪ Intentional (cardiac bypass, therapeutic)
▪ Primary - occurs when heat production in an otherwise healthy person is overcome
by the stress of excessive cold, especially when the energy stores of the body are
depleted
▪ Secondary - occur in ill persons with a wide variety of medical conditions
Hypothermia - Physiology
Hypothermia - Body Effects
Metabolic
• Basal metabolic rate (6% /C drop)
• Cardiac arrhythmias - usually resolve
spontaneously after rewarming
• AF- common when <32°C
CVS
• Bradycardia – pacing if bradycardia
persists despite rewarming
• VF - Defibrillation is usually unsuccessful
<30°C
• Hypothermia-related bleeding diathesis
Haematology
•Rewarming, rather than administration of
exogenous clotting factors
• Hct should increase 2% for every 1°C fall in
temperature
Hypothermia & Altered Mental State, DDx?
▪ Metabolic
▪ Hypothytoidism - myxedema coma
▪ Acute alcohol intoxication
▪ Adrenal insufficiency
▪ Drugs
▪ Central thermoregulatory failure
▪ Sedative-hypnotic, opioids, TCA, phenothiazines, BZ
▪ Secondary to neuroglycopenia – OHA
▪ Drop in core temperature – lithium toxicity
▪ inhibitory effect on vasoconstriction - alpha blockade
▪ CNS causes (hypothalamus is involved)
▪ Stroke, tumor, infection, ICH
Possible causes of bradycardia? Atropine?
Cardiac
•Atrioventricular block
•Sick sinus syndrome
•Ischemic heart disease
Drug
•beta-blockers, calcium-channel blockers, clonidine, digoxin, opioids, anticonvulsants
(phenobarbital), lithium
Metabolic
•Hypoxia, hypothermia, acidosis, hyperkalemia, hypercalcemia
Endocrine
•Hypothyroid
CNS
•Cushing Triad
•Hemorrhage and/or compression of the cerebellar vermis  depression of sympathetic activity
•Cervical spinal cord injury
•Seizures  particularly those with temporal lobe focus
•Oculocardiac Reflex
Atropine
NOT
effective in
hypothermic
bradycardia!
Physical Exam
▪ May not be able to palpate pulse
▪ Check for an organized rhythm on a cardiac monitor
▪ Doppler ultrasound is an ideal tool to assess cardiac activity
▪ May not be able to obtain BP
Hypothermia - Signs
Any bedside Investigations?
▪ POCT - H’stix, blood gas
▪ ECG – expected features?
ECG
What is Osborn wave?
▪ Correlate with degree of hypothermia?
▪ Which lead(s) more sensitive?
▪ Is it pathognomonic to hypothermia?
▪ DDx?
▪ YES! Amplitude inversely correlated with core
temp. <32.2°C (90°F)
▪ Inferior & anterior lateral leads more
sensitive!
▪ NOT pathognomonic!
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SAH
IHD
Chagas disease
Brugada syndrome
Hyper-Ca
cerebral injuries
early repolarization
coronary vasospastic ischemia
After resuscitation from cardiac arrest – esp VF
Very large Osborn waves may mimic RBBB
Osborn Wave in Hypothermia
Mayo Clin Proc, 2007;82(12):1449
Osborn Wave
Tex Heart Inst J 2000;27(3):316
▪ Osborne Wave in Hyper-Ca
▪ Corrected
Hypothermia - Investigations
▪ Urea and electrolytes
▪ Oliguric renal failure - consequence of low
cardiac output or rhabdomyolysis
▪ Hyperkalaemia may be severe
▪ Full blood count
▪ Thrombocytopenia may be a consequence of
hepatosplenic sequestration
▪ The packed cell volume increases slightly as
core body temperature falls.
▪ Glucose
▪ Coagulation
▪ Arterial blood gases
▪ Metabolic acidosis
▪ Type I or type II respiratory failure
▪ Thyroid function
Management Principles
▪ Careful handling of the patient
▪ Provision of basic or advanced life support
▪ No signs of life, begin CPR without delay
▪ Advanced airway management should be performed if indicated
▪ Risk of triggering a malignant arrhythmia is low
▪ Hypothermia with a perfusing rhythm
▪ Prevent further loss of heat
▪ Removing wet garments
▪ Insulating the victim from further environmental exposures
▪ Passive and active external rewarming
▪ Mild  passive rewarming
▪ Moderate  external rewarming
▪ Severe  Active core rewarming
▪ Treatment of any condition causing secondary hypothermia
▪ Drug overdose, alcohol use, or trauma
▪ Treat complications
Rewarming
▪ Consider accessibility to an appropriate facility, local expertise, resources,
and characteristics of the patient
▪ Rate Vs Methods
▪  core temperature by 1 - 2 °C per hour
▪ Faster rewarming rates (1–2°C/h) generally have better prognosis than slower
rewarming rates (<0.5°C/h).
Rewarming Methods
Hypothermia - Mx
▪ Stress-dose steroids
▪ Hydrocortisone 100mg for known adrenal insufficiency or treatment failure
▪ Empiric treatment with levothyroxine only for myxedematous patients
▪ 50–500 µg IV over several minutes
What to do next?
▪ Treatment of any condition causing secondary hypothermia
▪ Treat complications
▪ Disposal
Secondary Hypothermia
▪ Alcoholism, illicit drug, mental illness
▪ often exacerbated by concurrent homelessness
▪ Severe hypothyroidism, DKA
▪ Sepsis
▪ Multisystem trauma
▪ Prolonged cardiac arrest
▪ Multiple sclerosis with hypothalamic lesions
▪ Wernicke’s encephalopathy
▪ Episodic hypothermia with hyperhidrosis
Secondary Hypothermia
▪ Drugs  disrupt normal compensatory responses to a low
ambient temperature
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Beta-blockers
Clonidine
Meperidine
Pipamperone
Zotepine
Risperidone
Organophosphorus
Ethanol intoxication
General anesthetics
Hypothermia - Complications
▪ Monitor during and after rewarming for possible Complications
▪ Rewarming
▪ Arrhythmia - VF
▪ Core temperature after-drop
▪ Rewarming related hypotension
▪ Hypothermia
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Hypoglycemia
Paralytic ileus
Bladder atony
Bleeding diathesis
Rhabdomyolysis
Acid-base balance
Electrolytes - hyperkalemia and hypophosphatemia
If patient with hypothermia in Cardiac Arrest…
▪ ACLS 2010
▪ Severe hypothermia (body temperature <30°C [86°F]) is associated with marked depression of
critical body functions, which may make the victim appear clinically dead during the initial
assessment
▪ Lifesaving procedures should be initiated unless the victim is obviously dead
▪ Rigor mortis, decomposition, hemisection, decapitation
▪ Withholding IV drugs if core temperature <30°C
▪ Drug metabolism may be reduced  medications could accumulate to toxic levels in peripheral
circulation if given repeatedly
▪ Resuscitation should not be discontinued unless
▪ Core body temperature is greater than 30°C to 32°C (89.6°F)
▪ Still no signs of life are apparent
▪ Low serum potassium may indicate hypothermia, and not hypoxemia, as the primary
cause of the arrest
Hypothermia - VF
▪ VF should be treated with defibrillation
▪ European
▪ up to three defibrillations, with epinephrine withheld until the core temperature is higher than
30°C (86°F) and with the interval between doses doubled until the core temperature is higher
than 35°C (95°F)
▪ ACLS 2010
▪ If VT or VF is present, defibrillation should be attempted.
▪ If VT or VF persists after a single shock, the value of deferring subsequent defibrillations until
a target temperature is achieved is uncertain.
Hypothermia - ROSC
▪ After ROSC, patients should continue to be warmed to a goal temperature of
approximately 32° to 34°C
▪ Follow standard postarrest guidelines for mild to moderate hypothermia in patients
for whom induced hypothermia is appropriate
▪ For those with contraindications to induced hypothermia, rewarming can continue to
normal temperatures.
End of Resuscitation
▪ If a patient with cardiac arrest due to hypothermia is rewarmed to a core body
temperature that is higher than 32°C and asystole persists, irreversible cardiac
arrest is very likely, and termination of CPR should be considered.
▪ If serum potassium level > 12 mmol/L, termination of CPR should be considered
▪ Hyperkalaemia can be caused by
▪ Hypoxic and traumatic cell death
▪ Medications (e.g., depolarizing neuromuscular blockers)
▪ A severely hyperkalaemia is associated with nonsurvival and is considered a marker of hypoxia before
cooling
References
▪ N Engl J Med 2012;367:1930-8.
▪ Rosen's Emergency Medicine
▪ ACLS 2010
▪ Rosen & Barkin's 5–Minute Emergency
Medicine Consult
▪ Mayo Clin Proc, 2007;82(12):1449
▪ Am J M 2006;119(4):297-301
▪ BMJ 2006;332:706–9
▪ Indian Pacing Electrophysiol. J
2004;4(1):33-9
▪ Key Topics in Critical Care (2004) p.174-5
▪ CMAJ 2003 Feb 4;168(3):305
▪ Auerbach: Wilderness Medicine, 6th ed.
Ch 5
Thank you