ACLS adapted to the operating room

Why examiners ask this

Every candidate knows the ACLS algorithm; the examiner wants to know whether you can run it in a room where the patient is intubated, monitored with an arterial line, under drugs you gave, and often prone or draped. Arrest in the OR is usually witnessed and usually has a cause you can name. It tests organization under pressure and adaptability, especially whether you look for the anesthetic and surgical causes instead of reciting Hs and Ts.

The 60-second answer

Decision points and the "why"

• Witnessed, monitored arrest — shock VF or pulseless VT within seconds if the pads are on, because early shocks carry the highest success; the 2025 AHA guideline prefers a single-shock strategy to stacked shocks, so I resume compressions immediately after each shock.²
• Use the monitors I already have — the arterial line tells me compression quality and return of circulation without pausing, although there are inadequate adult data for a specific diastolic target; an end-tidal CO2 below 10 mmHg means I fix the compressions, and an abrupt rise suggests ROSC, with no absolute cutoff.²
• Ventilation — with a secured airway, 10 breaths per minute asynchronous with compressions;² I avoid hyperventilation because raised intrathoracic pressure cuts venous return.
• OR-specific causes first — I check the vaporizer and pumps for overdose, ask whether local anesthetic was just injected (lipid emulsion 1.5 mL/kg), whether neuraxial was placed (high spinal: epinephrine early and generously), whether the surgeon is near a great vessel, and whether insufflation, cement or tourniquet release just happened.
• Bradycardia and asystole from vagal reflexes — peritoneal traction, oculocardiac reflex or pneumoperitoneum; I tell the surgeon to stop, give atropine 0.5–1 mg or glycopyrrolate, and escalate to epinephrine quickly.
• Prone patient — AHA suggests turning supine first when that is safe; if it is not, I compress prone over the mid-thoracic spine between the scapulae, and in an ILCOR review all 12 operating-room or ICU patients given prone CPR achieved ROSC.¹
• ECPR — if the cause is reversible and the institution has ECMO, I activate the team early in refractory arrest rather than as a last resort; AHA supports ECLS for refractory arrest after cardiac surgery and in the cardiac intervention laboratory.³

The complication they will inject

ROSC comes back after 6 minutes, but the rhythm deteriorates into a wide-complex bradycardia with peaked T waves. The patient has renal failure and received succinylcholine. I treat this as hyperkalemic arrest: calcium chloride 1 g IV repeated as needed, insulin 10 units with 25 g dextrose, sodium bicarbonate 50–100 mEq, and hyperventilation, and I resume CPR if the pulse goes. AHA 2025 rates calcium, bicarbonate and insulin in hyperkalemic arrest as of uncertain effectiveness and advises against inhaled beta-agonists during arrest,³ but they are the fastest tools I have. I send a potassium, call nephrology for emergent dialysis, and keep compressions going because hyperkalemic arrests can survive prolonged resuscitation. Once stable I communicate with the surgical team, decide whether to finish or abort, plan post-arrest care with temperature control at 32–37.5 °C for at least 36 hours if the patient is not following commands and a MAP of at least 65 mmHg,⁴ and disclose to the family.

Pitfalls that cost points

• Reciting the generic algorithm without naming OR-specific causes.
• Pausing compressions to check a pulse when an arterial line is in place.
• Forgetting to turn off the volatile and infusions.
• Not telling the surgeon, who may be causing or able to fix the arrest.
• Giving amiodarone for a hyperkalemic or toxic rhythm without treating the cause.

Rapid-why

Q: Why epinephrine early in non-shockable rhythms? A: It raises aortic diastolic and coronary perfusion pressure; earlier administration in PEA and asystole improves ROSC.²

Q: Why lidocaine or amiodarone? A: For shock-refractory VF or pVT after the second or third shock; amiodarone 300 mg then 150 mg, or lidocaine 1–1.5 mg/kg then 0.5–0.75 mg/kg.⁵

Q: Why is vasopressin gone from the algorithm? A: Vasopressin alone or with epinephrine offers no advantage over epinephrine, so it was removed to simplify the algorithm.²

Q: What end-tidal CO2 makes you stop? A: I do not stop on end-tidal alone, but a value below 10 mmHg after 20 minutes of good CPR predicts very low survival and is one part of a multimodal team decision.²

Numbers to know

Links

• Intraoperative cardiac arrest, hyperkalemia, Local anesthetic systemic toxicity, anaphylaxis, Maternal cardiac arrest and resuscitative hysterotomy (coming)
• Atlas: Monitor atlas: perioperative cardiac events
• AHA Guidelines for CPR and Emergency Cardiovascular Care (2025); ASRA checklist for local anesthetic systemic toxicity