HKCEM College Tutorial Hypothermia author Dr. Lau chuleung, terry August, 2013
Triage Notes • F/91 • C/O: GE with vomiting / diarrhoea • PMH: HT • GCS E3 V4 M5 • BP 92/68 mmHg; P 48 bpm • RR 10/min; SpO2 92% RA • Temp. 33.2 ºC Triage Cat I
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
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 & 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? 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
Any bedside Investigations? • POCT - H’stix, blood gas • ECG – expected features?
What is Osborn wave? • YES! Amplitude inversely correlated with core temp. <32.2°C (90°F) • Inferior & anterior lateral leads more sensitive! • NOT pathognomonic! • Correlate with degree of hypothermia? • Which lead(s) more sensitive? • Is it pathognomonic to hypothermia? • DDx? • 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 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).
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 • 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 • 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.
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 End of Resuscitation
N Engl J Med 2012;367:1930-8. ACLS 2010 Mayo ClinProc, 2007;82(12):1449 Am J M 2006;119(4):297-301 BMJ 2006;332:706–9 Indian Pacing Electrophysiol. J2004;4(1):33-9 Key Topics in Critical Care (2004) p.174-5 CMAJ 2003 Feb 4;168(3):305 References • Rosen's Emergency Medicine • Rosen & Barkin's 5–Minute Emergency Medicine Consult • Auerbach: Wilderness Medicine, 6th ed. Ch 5