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Cardiac Arrest After Cardiac Surgery: An Evidence-Based Resuscitation Protocol Patrick Michaelis, BSN, RN Richard J. Leone, MD, PhD

More than 250 000 cardiac surgical procedures are performed annually in the United States. Postoperative cardiac arrest rates range from 0.7% to 5.2%. This article reviews current evidence for cardiac arrest resuscitation after cardiac surgery. The evaluation included resuscitation guidelines and 22 studies identified through a MEDLINE search. Evidence-based resuscitation differs from advanced cardiovascular life support guidelines. European Resuscitation Council guidelines include correcting reversible causes of arrest, applying defibrillation/pacing before external cardiopulmonary resuscitation, resternotomy within 5 minutes if electrical therapies fail, and restricting epinephrine use to avoid rebound hypertension. A 2017 Society of Thoracic Surgeons protocol derived from European Resuscitation Council guidelines is now standard of care in the United States. Evidence-based practices can improve survival and reduce resternotomy rates. This article describes the clinical implementation of the Society of Thoracic Surgeons guidelines. (Critical Care Nurse. 2019;39[1]:15-25)

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ccording to the Society of Thoracic Surgeons (STS), 286 149 adult cardiac surgical procedures were performed in the United States in 2015,1 including coronary artery bypass grafts, heart valve replacements, heart valve repairs, and combined procedures.1 Since 1998, postoperative cardiac arrest rates have ranged from 0.7% to 5.2%.2-7 Most cardiac arrests occur within the first 24 hours after skin closure, and up to half of cardiac arrests occur within the first 3 postoperative hours.2,8

CE 1.0 hour, CERP A This article has been designated for CE contact hour(s). The evaluation tests your knowledge of the following objectives: 1. Explain the rationale for defibrillation of ventricular fibrillation and ventricular tachycardia before initiation of cardiopulmonary resuscitation 2. Differentiate the restricted use of epinephrine in cardiac arrest after cardiac surgery from advanced cardiovascular life support–dosed epinephrine administration in other cardiac arrest situations 3. Describe the 6 key team roles for clinical staff treating patients who are experiencing cardiac arrest after cardiac surgery To complete evaluation for CE contact hour(s) for activity C1911, visit www.ccnonline.org and click the “CE Articles” button. No CE fee for AACN members. This activity expires on February 1, 2022. The American Association of Critical-Care Nurses is an accredited provider of continuing nursing education by the American Nurses Credentialing Center’s Commission on Accreditation. AACN has been approved as a provider of continuing education in nursing by the State Boards of Registered Nursing of California (#01036) and Louisiana (#LSBN12). ©2019 American Association of Critical-Care Nurses doi: https://doi.org/10.4037/ccn2019309

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Cardiac arrest after cardiac surgery presents unique challenges and opportunities that are not addressed by the current advanced cardiovascular life support (ACLS) algorithms. Some of the standard interventions (eg, immediate cardiopulmonary resuscitation [CPR] and aggressive vasopressor therapy) may even be harmful. Before 2009, expert opinions for resuscitating cardiac surgery patients emphasized CPR and resternotomy. Investigators concluded, perhaps unsurprisingly, that early CPR is associated with better survival than is delayed CPR, brief CPR is preferable to prolonged CPR, and early resternotomy yields better outcomes than does delayed resternotomy.

Evidence-Based Guidelines To review the current evidence for resuscitation of cardiac arrest after cardiac surgery, we searched the MEDLINE database with the PubMed search engine. Key words were cardiac surgery, cardiac arrest, cardiac arrest after cardiac surgery, resuscitation, defibrillation, epinephrine in cardiac arrest, and guidelines. We identified 22 relevant studies and also searched their reference lists along with reviews, editorials, and resuscitation guidelines. The seminal 2009 study by Dunning et al9 provided a systematic, evidence-based approach to resuscitating cardiac arrest after cardiac surgery. The European Resuscitation Council (ERC) incorporated Dunning’s recommendaIf available within 1 minute, defibrillation tions into should be performed before CPR in VF its 2010 and pulseless VT arrests. guidelines for resuscitation, which were updated in 2015 and are now the standard of care in most European countries.10,11 In 2012, the European Association for Cardio-Thoracic Surgery (EACTS) integrated the ERC guidelines into the Cardiac Surgery Advanced Life Support course, now the Cardiac Surgical Unit Advanced Life Support (CSU-ALS) course, which uses best evidence to train clinicians in the resuscitation of cardiac arrest in postoperative cardiac surgery

patients.12 In 2015, Ley13 published standards for resuscitating patients after cardiac surgical procedures. In 2017 the STS published an expert consensus article on resuscitating patients who experience cardiac arrest after cardiac operations.14 The consensus article is derived from the 2016 STS/EACTS protocol that distilled the current evidence into a set of guidelines for managing cardiac arrest and prearrest after cardiac surgery. It begins with the premise that CPR is ineffective in patients with tamponade, hemorrhagic hypovolemia, or tension pneumothorax. Tamponade and hemorrhage are 2 common causes of arrest after cardiac surgery. Without immediate resternotomy, patients with these conditions experience critically inadequate cerebral perfusion. Tension pneumothorax is usually treated with needle or tube thoracostomy, but if this condition is present but unrecognized, resternotomy will also decompress the chest and potentially restore a pulse. Patients who have undergone cardiac surgical procedures are clearly differentiated from all others who experience cardiac arrest. Key STS/EACTS recommendations include the following: apply defibrillation and pacing before CPR if these modalities are available within 1 minute, perform resternotomy within 5 minutes if electrical therapies fail or are not indicated, use CPR as a bridge to rapid resternotomy, establish 6 key roles on the resuscitation team, and restrict the use of epinephrine.14 In contrast, the American Heart Association has yet to differentiate the cardiac surgery patient subset from the general population in its ACLS algorithms. The STS/EACTS protocol is now the standard of care in the United States for cardiac arrest after cardiac surgery. Table 1 shows ERC/STS/ EACTS modifications to the ACLS universal algorithm. The ACLS and CSU-ALS approaches to resuscitation of postoperative cardiac surgery patients are quite different. The ACLS algorithms tend to focus on people who experience arrest outside the hospital and are resuscitated by bystanders or first responders who initiate CPR, use automated external defibrillators, and administer drugs recommended by ACLS, if available. The CSU-ALS

Authors Patrick Michaelis is a private consultant in Bellingham, Washington. Richard Leone is a cardiothoracic surgeon, Skagit Regional Health, Mount Vernon, and Kadlec Regional Medical Center, Richland, Washington. Corresponding author: Patrick Michaelis, BSN, RN, 594 Summit Place, Sedro Woolleey, WA 98284 (email: [email protected]). To purchase electronic or print reprints, contact the American Association of Critical-Care Nurses, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 899-1712 or (949) 362-2050 (ext 532); fax, (949) 362-2049; email, [email protected].

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guidelines address postoperative cardiac surgery patients who experience a witnessed arrest in the hospital and are resuscitated by experienced clinicians who apply defibrillation or pacing immediately and can administer CPR and rapid resternotomy if needed. These patients are often intubated and highly monitored. Clinicians have a wide range of treatment options. Emergency resternotomy is a standard component of the resuscitation protocol. The protocol does not recommend administering epinephrine at the ACLS dose.

Characteristics of Cardiac Arrest After Cardiac Surgical Procedures Ngaage and Cowen8 studied 7209 patients who underwent coronary artery bypass grafting or aortic valve replacement between April 1999 and June 2008. One hundred eight patients experienced cardiorespiratory arrest. Eighty-six of these patients experienced cardiac arrest only, an overall cardiac arrest rate of 1.2%. Perioperative myocardial infarction accounted for approximately one-half of the arrests, and surgical problems (tamponade and hemorrhage) caused almost one-fourth.8 Although postoperative myocardial infarction is a relatively rare complication of cardiac surgery, it is a frequent cause of perioperative cardiac arrest (Figure 1). Arrhythmia rates vary from study to study. Ngaage and Cowen8 described the frequency with which each of the major disturbances of electrical rhythm occur. Ventricular fibrillation (VF) or ventricular tachycardia (VT) accounted for 70% of the cardiac arrests in patients in their study. Asystole caused 17% of the cardiac arrests.

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Pulseless electrical activity (PEA) occurred in 13% of the cardiac arrests.8 When defibrillation is performed immediately, patients with VF and pulseless VT (pVT) have a high rate of survival. In patients who experience out-of-hospital arrests, asystole carries a dismal prognosis, but in postoperative cardiac surgery patients, asystole can often be corrected by temporary cardiac pacing. In postoperative cardiac surgery patients, PEA is often caused by tamponade or hemorrhage. Rapid resternotomy can decompress the heart and great vessels, restoring spontaneous circulation while revealing the underlying problem. If the electrocardiogram (ECG) and pressure waveforms are incompatible with viable cardiac output, for example during VF or asystole, the arrest protocol can be initiated without first checking a pulse. If the waveforms suggest perfusion but cardiac arrest is suspected, briefly palpate a carotid or femoral pulse while comparing the ECG tracings to pressure waveforms. In cardiac arrest, all waveforms, including those for arterial pressure, central venous pressure, pulmonary artery pressure, pulse oximetry, and end-tidal carbon dioxide, eventually become nonpulsatile. An ECG trace showing a sinus rhythm at a reasonable rate (approximately 50 to 120/min) in the absence of

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pulsatile pressure waveforms should be considered a cardiac arrest (ie, PEA). Early identification and correction of reversible problems can eliminate the need for resuscitation. Endotracheal tube malposition, intravenous infusion errors, and tension pneumothorax should be

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ruled out during every patient assessment. Figure 2 shows the STS/EACTS protocol for cardiac arrest in patients after cardiac surgery. The interval between cardiac arrest and resuscitation is one of the strongest predictors of survival. Early

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resuscitation yields the best outcomes. In 2002, Weisfeldt and Becker15 proposed a 3-phase, time-sensitive model of cardiac arrest and indicated the most effective therapy during each phase. In 2006, Gilmore et al16 found that although CPR offers no benefit over defibrillation during the first 5 minutes of cardiac arrest, CPR is of considerable benefit between 5 and 15 minutes after arrest begins. 1. Electrical phase (0 to 5 minutes after onset of arrest): During this phase the body still has oxygenated blood, and immediate defibrillation or pacing yields a higher survival rate than does CPR. However, if electrical therapies either fail or are not indicated (as in patients with PEA), CPR should be initiated immediately and the resuscitation team should prepare for rapid resternotomy. 2. Circulatory phase (5 to 15 minutes after onset of arrest): CPR is important during this phase because it restores oxygenated blood to the vital organs. After cardiac surgical procedures, the main role of CPR is to support circulation as a bridge to resternotomy. The early onset of the circulatory phase underscores the importance of resternotomy within 5 minutes. 3. Metabolic phase (more than 15 minutes after onset of arrest): Therapy, at least the type that is supported by current science, may be less effective during this phase because of cellular damage. The intra-aortic balloon pump is an effective first-line treatment. Mechanical circulatory support can provide myocardial salvage while ensuring adequate circulation and protecting end organs. Extracorporeal membrane oxygenation may be employed to support the heart and lungs during periods of cardiogenic shock and poor oxygenation even in the presence of mechanical ventilation. A left ventricular assist device can help off-load the left ventricle. Induced hypothermia may also be of benefit during this phase.

Management of Arrhythmias During Cardiac Arrest After Cardiac Surgery In VF or pVT, up to 3 stacked shocks, if available within 1 minute, should be administered before CPR and resternotomy are performed.17,18 A dedicated, bedside, stand-alone defibrillator facilitates delivery of the first shock within 1 minute (Figure 3). After 3 failed attempts at defibrillation, CPR should be initiated, a bolus of 300 mg of amiodarone should be given through a central catheter, and resternotomy should be performed within 5 minutes.14

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Early defibrillation is crucial. In an observational study of a mixed population of 6789 inpatients with cardiac arrest due to VF or pVT, defibrillation within 2 minutes resulted in a return of spontaneous circulation in 66.7% of patients, and 39.3% of patients survived to hospital discharge. When defibrillation occurred more than 2 minutes after arrest, the rate of return of spontaneous circulation dropped to 49.0%, and 22.2% of patients survived to hospital discharge.17

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In 2007, Richardson et al18 constructed a best evidence topic according to a structured protocol. The authors investigated the number of defibrillation attempts that should be made before reopening the chest in postoperative cardiac surgery patients who experience cardiac arrest. The authors identified 1183 relevant articles and selected 15 as best evidence on the subject. These studies demonstrated that the first shock in patients with VF or VT had a success rate of about 78%; the second shock, about 35%; the third shock, about 14%. No significant benefit was seen after a fourth shock. The combined defibrillation success rate of the 3 shocks was around 88%. Almost 9 of 10 patients successfully regained spontaneous circulation through defibrillation.18 The unfortunate 10th patient became a candidate for rapid resternotomy, with CPR bridging the interval between defibrillation and chest reopening. In asystole or severe bradycardia, cardiac pacing, if available within 1 minute, should be administered before CPR and resternotomy are performed. Transcutaneous pacing may be implemented before CPR, but only if it is available within 1 minute. With transcutaneous pacing, assess sedation needs. If pacing attempts are unsuccessful, CPR should be initiated and resternotomy should be performed within 5 minutes (Table 2). After cardiac surgical procedures, asystole is usually an electrical—rather than a metabolic—problem. For example, sinus arrest, sinus exit block, or atrioventricular block in the absence of viable escape rhythms can cause ventricular asystole, which can often be corrected by epicardial or transcutaneous pacing. Bradycardia usually responds well to artificial cardiac pacing. Atropine has not been shown to improve outcomes in cardiac surgery patients with asystole or severe bradycardia, and its administration may delay resternotomy. Therefore, the STS/EACTS protocol states that atropine should not be a routine part of the resuscitation protocol for cardiac surgery patients.14 If PEA is present, initiate CPR immediately while preparing for emergency resternotomy. The STS/EACTS protocol recommends that emergency resternotomy be performed within 5 minutes in a patient with arrest that is not caused by VF or VT and does not resolve after pacing and exclusion of readily reversible causes. Resternotomy is mandatory if external CPR does not generate a systolic pressure of at least 60 mm Hg. If CPR consistently maintains a systolic pressure above 60 mm Hg, resternotomy

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may be deferred beyond 5 minutes if necessary.14 External CPR usually generates a cardiac index of around 0.6 L/min per square meter.19 If the external cardiac pacemaker is connected and functioning before the arrest, consider turning the pacemaker off briefly to exclude underlying VF: pacing spikes may mimic narrow ventricular complexes on the ECG. In patients who experience cardiac arrests in which defibrillation and pacing are not indicated, potential causes of PEA should be assessed. In patients undergoing noncardiac surgical procedures, arrests due to PEA are associated with poor outcomes. In contrast, PEA arrest after cardiac surgery is likely due to tension pneumothorax, tamponade, or hemorrhage. Prompt decompression of tension pneumothorax and rapid resternotomy to treat tamponade and hemorrhage are associated with excellent outcomes. Reversible causes of hypoxia were most likely addressed during the patient’s routine care. Acidosis (hydrogen ions), hyperkalemia, and hypokalemia are unlikely causes of PEA because serum pH and potassium are carefully monitored after a surgical procedure. Hypothermia is also unlikely to cause cardiac arrest, but if hypothermia occurs, active rewarming is recommended instead of the passive rewarming that would have already been implemented in the intensive care unit. Similarly, PEA due to drug effects (toxins) is unusual, but the STS/EACTS protocol recommends ceasing all drug infusions unless a specific drug is suspected as the causative agent. Thromboembolic or mechanical obstruction (eg, pulmonary embolus, coronary thrombosis, or valve obstruction) is difficult to treat without resternotomy and cardiopulmonary bypass. In patients with PEA or ventricular arrest during epicardial pacing, ECG traces are either absent or highly

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variable and are subject to chest compression artifact, rendering the ECG unreliable as a trigger for an intraaortic balloon pump. The intra-aortic balloon pump trigger should be changed to pressure mode at a frequency of 1:1 and at maximal augmentation. These settings allow cardiac massage to be intensified without interference from the ECG trace and may improve mean blood pressure and coronary artery perfusion. If cardiac massage is interrupted for a significant period, triggering should be changed to an internal mode at 100/min until massage is restarted.14

Epinephrine and Infusions When cardiac arrest occurs shortly after a surgical procedure, defibrillation, pacing, and/or rapid resternotomy can restore spontaneous circulation. In these situations, epinephrine can be dangerous. Consider a hypothetical 70-year-old patient who experiences cardiac arrest 1 hour after 3-vessel coronary artery bypass grafting. The patient’s cardiac rhythm is PEA. Cardiopulmonary resuscitation is initiated and, according to ACLS guidelines, 1 mg of epinephrine is administered. The surgeon performs emergency resternotomy and relieves the causative tamponade. Spontaneous circulation is restored but unfortunately the patient’s blood...