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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 •<35C Moderate •32 - 35C Severe •28 - 32C 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! ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ 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 ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ 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. 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
