Hypothermia — Viva

Q1: Definition and staging (2 min)

"Define hypothermia and stage it for me."

• Definition: unintentional core temperature below 35 C, low-reading thermometer (tympanic thermocouple if breathing; oesophageal if a tube/SGA is in place; rectal/bladder practical). Infrared tympanic devices that do not seal the ear are not designed for low cores.
• ANZCOR: mild 32 to 35, moderate 28 to 32, severe below 28.
• Swiss HT I to IV only (no HT V in ERC/Paal 2021): HT I conscious (~35 to 32); HT II impaired consciousness, below 32 to 28, may or may not shiver; HT III unconscious with vital signs (below 28 C, not 28 to 24); HT IV vital signs absent (classically below 24 C; vital signs can persist below 24 C).
• Revised Swiss: AVPU; shivering not stage-defining.^[5][3]

Q2: ECG changes and why gentle handling matters (2 min)

"What ECG changes do you expect, and why is the patient handled gently?"

• Sinus bradycardia; Osborn (J) wave; prolonged intervals; AF; VF; asystole; shivering artefact.
• J-wave 32 C cut-off is exam convention, not in fetched ERC/Paal this pass.
• Cold myocardium + afterdrop (further cooling after rewarming starts) + rough movement → VF. Cut wet clothes; only warmed fluid 38 to 42 C.^[5]

Q3: Staged rewarming (3 min)

"Take me through rewarming by stage."

• HT I: passive external while able to shiver. Do not quote unsourced 0.5 to 2 C/h as a universal rate.
• HT II: active external (forced warm air / heat packs, trunk first). Afterdrop has no sourced 1 to 2 C magnitude this pass.
• HT III to IV: warmed IV 38 to 42 C, gases, lavage bridge; ECLS/ECMO for arrest (ECMO preferred over CPB). Do not quote unsourced 10 C/h as a universal ECLS rate.
• Paal high-risk transfer: below 30 C if young/healthy, below 32 C if elderly/comorbid, ventricular arrhythmia, or SBP below 90 mmHg.^[5]

Q4: Cardiac arrest and HOPE (3 min)

"A cold patient arrests. Walk me through it."

• Life check up to one minute (pulse, ECG, EtCO2, ultrasound). Do not compress a slow but perfusing pulse.
• Three shocks, then delay further VF shocks until core above 30 C.
• Withhold adrenaline below 30 C; 6 to 10 min at 30 to 34 C.^[3]
• HOPE for ECLS triage (NPV 97% if below 0.10). Not a 32 C death clock. Not a universal K 8 versus 12 rhyme.
• ANZCOR avalanche: burial over 35 min + obstructed airway, or K above 12 mmol/L.
• Unwitnessed ECLS series: overall survival 27%; most survivors intact. Some series (including Wanscher at 15.5 to 20.2 C) show excellent selected outcomes — do not teach "100%" as typical.^[8][3]

Q5: Secondary causes and pitfalls (2 min)

"What secondary causes must you look for, and name three pitfalls."

• Glucose always; sepsis; myxoedema (levothyroxine and hydrocortisone; passive rewarming first); overdose (naloxone trial).
• Pitfalls: 32 C cease clock; HT V; shivering-stop as the stage; infrared tympanic as sole reading; standard 3-to-5-min adrenaline below 30 C; trusting 37 C clotting tests in a bleeding trauma patient; cardioverting stable cold AF.^[5]

References3ShowHide

1. [3]Lott C, Truhlář A, Alfonzo A, et al. European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances Resuscitation, 2021.PMID 33773826
2. [5]Paal P, Pasquier M, Darocha T, Lechner R, Kosinski S, Wallner B, Zafren K, Brugger H. Accidental Hypothermia: 2021 Update Int J Environ Res Public Health, 2022.PMID 35010760
3. [8]Pasquier M, Rousson V, Darocha T, et al. Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: An external validation of the HOPE score Resuscitation, 2019.PMID 30940473