Cardiac arrest is one of the most dramatic events in the operating room. Within seconds, the anesthesiologist may shift from routine care to leading a life-threatening crisis. The response must be swift, organized, and technically sound, but intraoperative arrest requires more than CPR.

In many cardiac arrests outside the operating room, the cause may not be immediately apparent. In the operating room, however, the cause is often related to something that has just happened: hemorrhage, an anesthetic drug, the depth of anesthesia, surgical manipulation, hypoxia, embolism, pneumothorax, anaphylaxis, or a sudden change in the patient’s physiology. The operating room also provides an unusual advantage. The providers know the patient’s medical history, the patient is monitored continuously, the airway is usually secured, invasive monitoring may already be in place, medications and blood products are immediately available, and surgeons and other specialists are nearby.

These advantages fundamentally change the role of the anesthesiologist. The goal is not simply to perform CPR according to an algorithm. The goal is to lead a coordinated resuscitation while simultaneously identifying and treating the cause of the arrest. This requires two processes to occur at the same time: restoration of circulation (ROSC) and diagnosis.

Note: This post was originally published in August 2015 as Cardiac Arrest in the OR and has been completely revamped and updated for accuracy and comprehensiveness.

Recognize the Crisis Early

Cardiac arrest in the OR under anesthesia is fortunately rare. Although the incidence of intraoperative cardiac arrest has been quoted as less than 0.1%, a small percentage of a very large number still represents a meaningful number of patients. Preparation for rare events is often more challenging than preparation for routine ones. When a rare event occurs, shock and fear can erase protocol from even the most prepared mind. Let me share some of the things that I’ve learned from 46 years of OR emergencies.

Always Assume An Alarm Is Real Until Proven Otherwise

Recognizing cardiac arrest in the OR may not be easy. Most OR alarms are false alarms: a disconnected lead can mimic asystole, cautery can create interference that looks like ventricular tachycardia, the pulse oximeter can slip off the finger, or the end-tidal CO2 sensor can become obstructed with moisture. Yet sometimes the alarms are real.

I was once on a medical volunteer trip in a low-resource setting. During one case, the anesthesiologist spent precious minutes troubleshooting the loss of a pulse oximeter reading because he thought the problem was mechanical. The patient was in cardiac arrest. We successfully resuscitated the patient, but the episode was a lasting reminder that the patient must come before the monitor.

The trap of ignoring an alarm can happen to anyone. Never assume that an alarm is false. I tell my students, “Don’t just look at your monitors; look at your patient.” Feel for a pulse, listen for heart tones and breath sounds, and look at the patient’s color. Never troubleshoot the alarm before checking your patient. The devices are there to help us, not replace us. We are the most important monitor in the room.

Treat the Cause, Not Just the Rhythm

The first principle of intraoperative cardiac arrest leadership is simple: treat the cause, not just the rhythm.

Cardiac arrest is a physiologic state, not a diagnosis. The ECG tells us what the heart is doing electrically, but it does not necessarily tell us why the patient has lost circulation.

A patient with pulseless electrical activity may have suffered a massive pulmonary embolism, profound hemorrhage, cardiac tamponade, severe hypoxia, tension pneumothorax, or another reversible cause. A patient with ventricular fibrillation may have developed the arrhythmia because of myocardial ischemia, electrolyte abnormalities, hypoxia, or a drug-related problem.

The operating room provides an important advantage: the events immediately preceding the arrest are often known.

• What happened during the preceding minute?
• Was there sudden surgical bleeding?
• Was a medication administered?
• Was the patient positioned differently?
• Was a surgical structure manipulated?
• Did the surgeon release a clamp?
• Was cement inserted?
• Was the patient insufflated?
• Was there a change in airway pressure?
• Did the end-tidal carbon dioxide suddenly fall?
• Did the patient become hypotensive before becoming pulseless?

The answers can dramatically narrow the differential diagnosis.

The leader therefore needs to resist the tendency to allow the cardiac arrest algorithm to become the diagnosis. CPR, defibrillation when indicated, airway management, and medications are essential. But they are interventions, not explanations.

A useful mental model is: Resuscitation keeps the patient alive while the team searches for the reason the patient arrested. The two processes should proceed simultaneously.

Lead Two Processes at Once

During an arrest, the anesthesiologist is often responsible for coordinating several activities simultaneously:

• High-quality chest compressions
• Rhythm assessment
• Defibrillation when indicated
• Oxygenation and ventilation
• Medication administration
• Hemodynamic monitoring
• Diagnostic evaluation
• Communication with the surgeon
• Mobilization of additional personnel and equipment
• Manage residual anesthesia and determine whether to restart it

No single clinician can perform all these tasks effectively. The leader’s job is therefore not to personally perform every intervention. The leader must organize the system.

This distinction becomes particularly important as the resuscitation becomes more complex. The anesthesiologist often leads the code in the OR but may feel pulled toward familiar tasks such as starting IVs, giving medications, or managing the anesthetic. Those tasks can distract from leadership. A leader who attempts to do everything may become the bottleneck in the resuscitation.

The leader is therefore functioning less like another member of the resuscitation team and more like the conductor of an orchestra. The individual musicians must perform their tasks, but someone must coordinate the entire performance.

This is more challenging in settings such as Ambulatory Surgery Centers where the resuscitation leader may be the only anesthesiologist on site. In those situations, the leader should use available personnel, including the surgeons, as effectively as possible.

Delegating tasks is only the first step. The leader must also make the team’s diagnostic thinking visible, so everyone is working from the same evolving explanation.

Practical Management During Cardiac Arrest in the OR

The principles above are most useful when they translate quickly into visible actions at the bedside. The following practical steps help the team maintain momentum, protect the surgical field, and keep diagnostic thinking active during the resuscitation.

Emergency Check Lists

I am not going to review BLS or ACLS guidelines here. Preparation requires knowing those protocols. As noted earlier, however, fear can erase protocol from even the best-prepared mind. Consider having laminated checklists for the most common emergencies available in your own OR. OR crisis checklists from Ariadne Labs can be found here for both online and printed use.

Tailor the ACLS Algorithm to the Patient’s Diagnosis

ACLS is a starting point, especially in the OR. Diagnosis-driven resuscitation does not mean abandoning ACLS; it means leading the team to use ACLS intelligently. The algorithm provides the base rhythm response, but the leader must decide when the patient’s diagnosis requires different priorities, different medications, or a different definitive treatment. For example:

• In Local Anesthetic Toxicity (LAST) you must modify ACLS to direct seizure control with benzodiazepines and call for 20% lipid emulsion early. Keep the team from reflexively using lidocaine, procainamide, vasopressin, beta blockers, calcium channel blockers, or high-dose epinephrine when possible.
• With a hyperkalemic arrest you must call for calcium early, then direct insulin/glucose, ventilation, and bicarbonate when appropriate to shift potassium intracellularly.
• Malignant Hyperthermia requires stopping triggering agents, early treatment with Dantrolene, management of hyperkalemia and acidosis, avoid calcium channel blockers, and start active cooling.

Tailor the ACLS algorithm to the working diagnoses.

Have The Gurney Outside the OR for all Prone and Sitting Cases

Turning a prone patient supine onto a gurney is usually easier and faster than rotating the patient on the OR table. Time is critical during an arrest and waiting for a gurney to be brought from preop or the recovery room can cost valuable minutes. If the patient is prone or sitting, keep the gurney immediately outside the OR.

Call for Crash Cart/Defibrillator Early

Call for the crash cart and defibrillator as soon as you become concerned that the patient is becoming unstable. Even if you never need it, having it close by will save critical minutes if the patient does decompensate. It will also prevent you from having to send one of your assistants out of the room. This could happen just when you need your OR nurse the most.

Secure the Airway

If the airway is not secured you must secure it. This can be difficult depending on surgical positioning. For more discussion see: Optimize head and neck position as best you can.

Asking for Help Is a Sign of Strength

We all tend to wait before asking for help. We believe we can manage the issue ourselves because most of the time we can. Denial is common: surely this cannot be happening; it must be a mechanical malfunction. We may also worry that someone will think poorly of us if we ask for assistance.

Most of us have experienced that queasy feeling that tells us things are happening too fast. We are not quite in control, and we do not yet know exactly what is going on. Listen to that instinct and call for backup. Make sure the surgeon and OR nurse know you are worried. If you do not end up needing the help, thank the team for coming and send them away. Knowing when to ask for help shows strength; it is not a sign of weakness.

Manage the Anesthetic

During a crisis, unless it’s a fire, immediately increase oxygen to 100% and turn off or reduce the anesthetic agent as appropriate. Small but important actions are often overlooked during resuscitation. If the resuscitation is successful, remember to resume an appropriate level of anesthesia for pain control and amnesia until the skin incision is closed.

Who Should Do Chest Compressions in Cardiac Arrest in the OR?

The anesthesia team may be tempted to do chest compressions, but this is usually not ideal for abdominal or chest cases. Access is limited, compression position may be suboptimal, and it can interfere with running the resuscitation.

In the OR, ask the surgeon or a surgical team member to perform compressions when feasible. They can work from their side of the drape, often with better access to the sternum, while the anesthesia team has more space to manage the resuscitation.

If the surgeon must control bleeding or manage another critical task, another team member can quickly gown and glove to relieve the person doing compressions. A five-minute scrub is not needed; just gown and glove.

If needed, lower the drape to improve communication between the surgical and anesthesia teams.

Don’t Forget Ongoing Blood Loss!

Do not forget that blood loss may continue during a code. I once cared for a teenage boy undergoing T3 to L4 thoracolumbar fusion who arrested from an air embolism. We turned him supine, performed CPR and ACLS, and successfully resuscitated him. About 10 minutes later, he again became hypotensive and developed pulseless electrical activity. In our relief after the initial save, we had missed ongoing bleeding from his open back wound. He had lost several units of blood into the sheets during the code. Rapid transfusion resuscitated him again, and he recovered fully.

Never forget that factors related to the ongoing surgery can deteriorate during CPR. Problems unrelated to the initial arrest can worsen while the team’s attention is focused on resuscitation. Once again: big picture.

Check the Defibrillator Pads

Cardiac arrest in the OR is complicated by the surgical field. The chest area may be wet with blood, sweat, and other secretions. During CPR, the defibrillator pads may come loose. If the code has gone on for a while, keep checking for a good connection before shocking.

Communication is Key

If it’s too noisy to hear, ask for quiet. It’s okay to ask for unneeded people to leave. Provide a verbal summary of resuscitative steps periodically. This can help keep everyone in the loop. It also allows others to point out suggestions on other things to do or try. Ask for suggestions as the code progresses. Many coordinated brains in an emergency are often better than one.

Resuscitation is Vital, But Don’t Forget the Surgical Field

Avoid contaminating the surgical field if at all possible. While resuscitation takes precedence, preventing infection and other complications is also important. Cover the surgical site. Have helpers doing chest compressions gown and glove. Consider additional antibiotic prophylaxis once resuscitation is successful.

Integrate the Surgical Team

The resuscitation must stay coordinated with the operative field, making the surgical team active participants in diagnosis and treatment.

The surgical team is part of the response. Intraoperative cardiac arrest is a shared crisis requiring anesthesia and surgery to combine information and action; the surgeon is not an observer.

Share What Each Team Can See

The surgeon may see information essential to identifying and correcting the cause—for example, major bleeding in the operative field while anesthesia sees hypotension and PEA.

Neither clinician has the complete picture alone. The anesthesiologist should ask early and directly:

“What is happening in the field?”

That question can redirect the team toward the reversible cause.

The Leader Must Remain Calm—but Not Passive

Calm leadership is often misunderstood. Being calm does not mean speaking softly, moving slowly, or appearing detached from the urgency of the situation. Effective crisis leadership combines urgency with control. The leader should sound as though the situation is serious but manageable.

The team should perceive:

“We have a problem, we understand what we are doing, and we are working through it.”

This matters because the emotional state of the leader influences the team. If the leader becomes visibly overwhelmed, communication deteriorates. Multiple people may begin issuing contradictory commands. Tasks may be duplicated while other essential tasks are neglected.

Conversely, a leader who remains organized can impose structure on an otherwise chaotic environment.

The goal is not to eliminate stress. It is to prevent stress from controlling the team.

How Do You Know CPR Is Effective?

Start With Your Patient

Look at your patient’s color. Is it improving? Can you feel a pulse with the compressions? Can you hear breath sounds with ventilation?

End Tidal Carbon Dioxide monitoring

Capnography is standard in the modern OR, and end-tidal carbon dioxide helps assess chest compression adequacy and return of spontaneous circulation. Kalenda first reported this in 1978, showing that ETCO2 increased with effective CPR, fell as rescuers fatigued, and improved when a fresh rescuer took over.

ETCO2 reflects pulmonary blood flow. When cardiac output falls, less carbon dioxide returns to the lungs and the capnograph drops abruptly.

During anesthesia, a sudden ETCO2 drop can signal hypotension or poor cardiac output; a rise after treatment suggests improving perfusion.

Use ETCO2 to gauge CPR effectiveness and ROSC. Values should exceed 10 mm Hg; values above 20 mm Hg suggest adequate compressions or ROSC. If ETCO2 is lower, improve compressions.

An ETCO2 below 10 mm Hg after 20 minutes of standard ACLS is associated with failure of ROSC.

Intravascular Monitors

During chest compressions, aim for diastolic pressure of 30-40mm Hg by arterial line catheter at time of full compressions. Coronary perfusion pressure (CPP) should be greater than 15 mmHg. (CPP= Diastolic BP- CVP)

Ultrasonography

Consider using a portable ultrasound or echocardiogram machine to identify cardiac motion. Our ability to feel a very weak pulse is limited. Sometimes what we think is pulseless electrical activity is really severe hypotension and poor perfusion, with persistent cardiac motion. A patient whose heart is still beating has a much higher chance of survival. This holds true even if we can’t feel the pulse. Place the ultrasound probe sub-xiphoid or parasternal. Aim it toward the heart. This can tell you if there is still cardiac motion.

May the force be with you

Christine E. Whitten MD, author:

Anyone Can Intubate: A Step-by-Step Guide, 5th Edition
Pediatric Airway Management: A Step-by-Step Guide
Basic Airway Management: A Step-by-Step Guide

Further Reading

• Kodali, B. S., & Urman, R. D. (2014). Capnography during cardiopulmonary resuscitation: Current evidence and future directions. Journal of Emergencies, Trauma, and Shock, 7(4), 332–340.
• McEvoy, M. D., Thies, K.-C., Einav, S., Ruetzler, K., Moitra, V. K., Nunnally, M. E., Banerjee, A., Weinberg, G., Gabrielli, A., Maccioli, G. A., Dobson, G., & O’Connor, M. F. (2018). Cardiac arrest in the operating room: Part 2—Special situations in the perioperative period. Anesthesia & Analgesia, 126(3), 889–903. https://doi.org/10.1213/ANE.0000000000002595
• Moitra, V. K., Einav, S., Thies, K. C., Nunnally, M. E., Gabrielli, A., Maccioli, G. A., Weinberg, G., Banerjee, A., Ruetzler, K., Dobson, G., McEvoy, M. D., & O’Connor, M. F. (2018). Cardiac arrest in the operating room: Resuscitation and management for the anesthesiologist: Part 1. Anesthesia & Analgesia, 126(3), 876–888. https://doi.org/10.1213/ANE.0000000000002596
• Smith, Z. (2025). Editorial: Cardiac arrest in the operating room: Reevaluating advanced cardiovascular life support. APSF Newsletter, 2, 44–45.