Intraoperative cardiac arrest
Why examiners ask this
Arrest in the operating room differs from arrest on the ward: it is witnessed, the airway is already secure, the cause is often something we did, and the cure is usually specific. The examiner wants ACLS delivered with leadership and then wants the OR-specific differential. It stresses organization under pressure and adaptability when the standard algorithm is not enough.
The 60-second answer
I declare the arrest out loud, call for help and the code cart, and assign roles. Compressions start immediately at 100–120 per minute and 5–6 cm depth,1 and I ask the surgeon to stop and help position. I turn off the volatile agent and any infusion that could be the cause, go to 100% oxygen, and ventilate at 10 breaths per minute without hyperventilating.1 For a shockable rhythm I defibrillate at 120–200 J biphasic as soon as pads are on; for asystole or PEA I give epinephrine 1 mg as soon as possible and every 3–5 minutes.1 I use end-tidal CO2 and the arterial line to judge compressions, aiming for end-tidal CO2 above 10 and ideally above 20 mmHg,1 and a rising arterial diastolic pressure (targets of 20–25 mmHg are commonly quoted). Throughout, I hunt for the cause that fits this case.
Decision points and the "why"
- Cause-directed differential — beyond the Hs and Ts, I name the anesthetic causes: hypovolemia from hemorrhage, anaphylaxis, local anesthetic toxicity, high neuraxial block, auto-PEEP, tension pneumothorax, gas or air embolism, hyperkalemia, malignant hyperthermia, a vagal response to insufflation or traction, and drug error. Each has a specific fix.
- Peri-arrest epinephrine — before pulselessness I use 10–100 mcg boluses; the 1 mg dose is for the arrested patient, because giving it to a patient with a pulse causes severe hypertension and arrhythmia.
- Disconnect the circuit — in a patient with obstructive lung disease, a 30-second disconnect relieves dynamic hyperinflation and restores venous return; it is a diagnostic and therapeutic step.
- Specific antidotes — lipid emulsion 20% 1.5 mL/kg for local anesthetic toxicity with reduced epinephrine doses of 1 mcg/kg or less; calcium, insulin and bicarbonate for hyperkalemia; dantrolene for malignant hyperthermia.
- Prone patient — I start compressions prone with counter-pressure under the sternum, because turning delays CPR; I turn once the airway and lines are secure enough to allow it.
- Echo during pauses — a brief look in the 10-second pulse check separates tamponade, a massive pulmonary embolus with a dilated RV, and hypovolemia;2 I do not extend the pause beyond 10 seconds to get it.1
- When to stop — end-tidal CO2 below 10 mmHg after 20 minutes of CPR in an intubated patient is a poor prognostic sign;1 I consider ECMO early in a reversible cause, and if the chest is already open the surgeon can perform internal cardiac massage.1
The complication they will inject
Five minutes after a spinal for knee replacement, the patient becomes bradycardic and then asystolic. I recognize a vagal or high-block arrest with profound sympathectomy. I call it, start compressions, and give atropine and epinephrine early rather than waiting, because these arrests progress fast and early epinephrine in non-shockable rhythms is associated with better neurologically intact survival.2 I support the airway and ventilate. If the stem then gives me return of circulation, I move to post-arrest care: mean pressure at least 65 mmHg and systolic at least 90 mmHg, oxygen titrated down to an SpO2 in the mid-90s to avoid hyperoxia, end-tidal CO2 35–40 mmHg, a constant temperature between 32 and 37.5 °C if the patient remains unresponsive,1 a 12-lead ECG, and a conversation with the surgeon about whether to continue. I disclose the event to the family.
Pitfalls that cost points
- Reciting ACLS without assigning roles or saying who leads.
- Never naming the anesthetic causes that make OR arrest different.
- Giving 1 mg epinephrine to a hypotensive patient with a pulse.
- Leaving the volatile running during CPR.
- Forgetting post-arrest care and the debrief.
Rapid-why
Q: Why monitor end-tidal CO2 during CPR? A: It reflects pulmonary blood flow and therefore compression quality; a sudden rise to normal values signals return of circulation.1
Q: Why amiodarone in ventricular fibrillation? A: For shock-refractory VF it improves survival to admission; 300 mg then 150 mg, with lidocaine 1–1.5 mg/kg as an alternative.1
Q: Why avoid hyperventilation during CPR? A: Positive pressure reduces venous return and coronary perfusion pressure; 10 breaths per minute is enough.
Q: Why is the OR arrest survival better than the ward? A: It is witnessed, monitored and treated within seconds, and the causes are often reversible.
Numbers to know
| Item | Value |
|---|---|
| Compression rate and depth | 100–120/min, 5–6 cm1 |
| Ventilation with secured airway | 10 breaths/min1 |
| Epinephrine in arrest | 1 mg IV every 3–5 min1 |
| Biphasic defibrillation | 120–200 J1 |
| Amiodarone | 300 mg, then 150 mg1 |
| CPR quality targets | ETCO2 >10, ideally >20 mmHg;1 diastolic ~20–25 mmHg |
| Post-arrest targets | MAP ≥65, SBP ≥90 mmHg; 32–37.5 °C1 |
Links
- ACLS adapted to the operating room, anaphylaxis, Local anesthetic systemic toxicity, hyperkalemia, High or total spinal
- Atlas: Monitor atlas: perioperative cardiac events
- AHA Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care (2020, 2023 update)
Sources
- 1.Cardiopulmonary Resuscitation (CPR) in Adults · Merck Manual Professional Edition, 2026 · merckmanuals.comBased on the 2020 AHA CPR/ECC guidelines (Panchal et al.); the primary AHA text was not reachable from the fetcher.
- 2.Cardiac Arrest · Merck Manual Professional Edition · merckmanuals.com
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.