TSRA Content:
Author: Jessica G.Y. Luc, MD
This is a revision and update from the previous edition of the TSRA Primer in Cardiothoracic Surgery written by Garry Weide, MD
Introduction
Cardiac arrest is a dreaded complication following any cardiac operation. Arrest can occur unexpectedly at the conclusion of surgery, during transport from the operating room, in the intensive care unit (ICU), or later during recovery on the ward. The incidence of in-hospital cardiac arrest after cardiac surgery is low, but the outcomes of resuscitation are good for patients to survive to hospital discharge if resuscitation is timely and well managed.
The two most common causes of cardiac arrest are ventricular fibrillation and pericardial tamponade. The approach to resuscitation follows the recommendation of the American Heart Association with some important caveats specific to the surgical patient.
Most cardiac surgery patients are initially intubated and ventilated with invasive monitoring in situ. This offers many advantages but can also complicate matters because patients may suffer cardiac arrest as a direct consequence of a problem with the ventilator or artificial airway. Furthermore, monitoring equipment may lead to false reassurance or precipitate inappropriate intervention.
Initial Resuscitation
When a cardiac arrest occurs, timely and appropriate intervention can be lifesaving. Assessment and treatment often occur simultaneously. The diagnosis is often made retrospectively following a resuscitation.
The initial approach to a cardiac arrest follows basic Advanced Cardiovascular Life Support (ACLS) recommendations. In addition, unique to post cardiotomy patients is the Society of Thoracic Surgeons (STS) Expert Consensus for the Resuscitation of Patients Who Arrest after Cardiac Surgery. First, it should be established that hypotension is real by palpating a central pulse. If a pulse is palpated but the arterial waveform suggests cardiac arrest, blood pressure should be measured non-invasively. If indeed there is a low blood pressure and the patient has pacing wires, reconnect the pacing wires immediately after observing the offending rhythm (see next section). If the patient is being paced, the pacemaker should be paused briefly to rule out underlying ventricular fibrillation (VF). An airway should be established if the patient is not already intubated, and the patient manually ventilated with positive pressure at a rate of 8-10 breaths/min, this removes the ventilator as a potential source for the patient's arrest. The next goal is to restore circulation. Patients should be prepared for resternotomy (target of within 5 minutes of arrest), especially if within the first 10 days post-surgery. If after the 10-day period, a senior physician should decide whether resternotomy is indicated. If the patient arrests due to massive bleeding in the ICU, then rapid resternotomy should be performed for open cardiac massage while undergoing volume resuscitation, manual control of bleeding, with immediate transport to the OR. While resuscitation is under way, an evaluation should be undertaken to determine the possible cause of cardiac arrest.
Evaluate for Reversible Causes of Cardiac Arrest
In brief, reversible causes of cardiac arrest include the 5H’s and 5T’s. The 5H’s include hypovolemia, hypoxia, hydrogen ion (acidosis), hypo or hyperkalemia, hypothermia. The 5T’s include tension pneumothorax, tamponade, toxins, thrombosis (pulmonary and coronary). One can approach this by first checking the rhythm strips for the patient on telemetry to evaluate the rhythm prior to arrest. In addition, one should check the chest tube drainage and review the chest x-ray. This may indicate whether there is impaired venous return (i.e. tension pneumothorax, cardiac tamponade, massive mediastinal bleeding, displaced endotracheal tube). One should review laboratory values including acid-base and electrolyte disturbances which may lead to arrhythmias. One should review medications that may have precipitated arrest including sedating medications, antiarrhythmics, and other medications that may affect electrolytes. In addition, an assessment of whether inotropes and vasopressors are being administered at correct rates and are reaching the vascular system. Point of care ultrasound to assess for tamponade, cardiac activity, mechanical complications, and regional wall motion abnormalities can also be undertaken.
Rhythm-Specific Management
Ventricular Tachycardia and Fibrillation:
Ventricular tachycardia (VT) or VF can be identified on a monitor and confirmed by a lack of pulse. The primary goal in VT or VF is rapid defibrillation. Three attempts at sequential defibrillation with 200 joules (biphasic) or 360 joules (monophasic) should be performed. Often, VT /VF responds to the first attempt at defibrillation. If the patient remains in VT /VF or has severe hypotension after 1-minute, basic life support should be continued with delivery of amiodarone 300mg IV. A further dose of 150mg may be given for recurrent or refractory VT/VF. Lidocaine 1mg/kg IV may also be used as an alternative of amiodarone. This should be followed by preparation for emergency resternotomy with continuation of external chest compressions at a rate of 100/min and a single DC shock every 2 minutes until resternotomy.
Asystole and Severe Bradycardia:
In the setting of arrest due to asystole or severe bradycardia, pacing wires (if available) should be connected to a pacemaker. If epicardial pacing wires are not present, transcutaneous pacing should be attempted. The pacemaker should be set in the DDD mode at a rate of 80-100 beats/min at maximum atrial and ventricular output voltages. Atropine 1mg IV with repeat doses of 1mg every 3-5 minutes to a total dose of 0.04mg/kg may be considered to restore an intrinsic rhythm. Again, if early medical efforts fail to revive a patient in asystole, preparation for rapid resternotomy is indicated with continuation of external chest compressions until resternotomy.
Pulseless Electrical Activity (PEA):
If a cause of PEA can be identified and treated rapidly, resuscitation from PEA is likely to be successful. Common causes of PEA are cardiac tamponade, tension pneumothorax, coronary artery occlusion or dehiscence resulting in myocardial ischemia, and severe hypovolemia due to blood loss into the chest and mediastinum. As a first step in determining the cause of PEA, pacing should be briefly paused to rule out VF. Auscultation of the chest, examination of lack of pulsatile arterial waveform or end-tidal carbon dioxide, or palpation of pulse can establish whether the patient is in PEA. If the patient is in PEA, preparation for rapid resternotomy is indicated with continuation of external chest compressions until resternotomy.
Resternotomy
The resternotomy tray should contain at a minimum 5 essential items, including a scalpel, wire cutting, heavy needle driver, sternal retractor, and sucker. If the patient’s pacing wires are not capturing, it would benefit from having a set of pacing wires that can be sewn onto the heart to pace. Once the decision is made to pursue resternotomy following discussion with faculty, the patient should be prepped and draped in a sterile fashion. A scalpel or scissors are used to cut the sutures to open the sternotomy incision and sternal wires are cut with wire cutters and removed with a heavy needle holder. The sternal edges are then separated with a sternal retractor and suction used to clear excessive blood or clot. If the pericardium has been closed, the sutures should be cut to visualize the heart. If cardiac output is not restored, pacing wires can be sewn to the heart to emergency pace the heart. In addition, amiodarone or epinephrine can be administered through injection into the heart if there was concern of lack of circulation of resuscitation medications due to lack of perfusion. If there remains no restoration of cardiac output, internal cardiac massage should be undertaken taking care to not disrupt coronary artery bypass grafts or lift the heart if the patient had a mitral valve replacement to not cause posterior ventricular rupture. If cardiac output is restored, one has successfully treated the cardiac arrest and should wait for expert assistance prior to proceeding. While waiting, one can do a thorough examination of the heart to evaluate for sites of bleeding if there was tamponade. If the patient is post coronary artery bypass grafting surgery, an examination to palpate the bypass grafts or doppler to ensure patency can be of benefit.
Other Populations
For further details regarding resuscitation of patients who arrest after cardiac surgery who are post-transplant, with ventricular assist devices, pediatric, or patients who underwent minimally invasive cardiovascular surgery, please refer to the STS Expert Consensus for the Resuscitation of Patients Who Arrest after Cardiac Surgery, ACLS, and the pediatric advanced life support (PALS) algorithm.