Cardiopulmonary Resuscitation in Pregnancy
Deborah Anne Cruz
Patricia Marie Constanty
Shailen S. Shah
Cardiopulmonary arrest is the abrupt cessation of spontaneous and effective ventilation and systemic perfusion. Sudden cardiac arrest (SCA) is a leading cause of death in the United States (U.S.) and Canada.1,2,3 Data from the Centers for Disease Control and Prevention (CDC) estimate that in the U.S. approximately 300,000 people die annually in out-of-hospital and emergency department settings from coronary heart disease.1,2,4,5 Approximately 250,000 of these deaths occur in an out-of-hospital setting.1,6 The annual incidence of SCA in North America is approximately 0.55 per 1,000 population.3,4 With respect to the obstetric patient population, cardiopulmonary arrest occurs in approximately 1 in 30,000 pregnancies.7,8
The goal of cardiopulmonary resuscitation (CPR) is prompt initiation of basic life support (BLS) to provide artificial ventilation and perfusion until advanced cardiac life support (ACLS) can be initiated. The desired outcome of resuscitation efforts is restoration of spontaneous and effective cardiopulmonary function. When cardiopulmonary arrest occurs during pregnancy, normal physiologic alterations of pregnancy should be integrated into resuscitation protocols recommended for the nonpregnant population, in order to facilitate optimal outcomes for both the pregnant woman and the fetus.
Since publication of the second edition of this text, several important changes in managing CPR and emergency cardiac care (ECC) have been recommended.9 As with all versions of the ECC guidelines published since 1974, the 2010 American Heart Association Guidelines for CPR and ECC contain recommendations designed to improve survival from SCA and acute life-threatening cardiopulmonary problems.
This chapter addresses the causes of cardiopulmonary arrest and presents updated recommendations for basic and advanced resuscitation techniques. The effects of pregnancy on CPR are described including modifications to resuscitation techniques that should be considered during pregnancy. The role of perimortem Cesarean delivery and infant survival data are presented. Potential complications associated with resuscitation efforts are identified. Finally, the vital need for collaboration among members of the health care team and advance preparation to facilitate optimal response to this relatively rare emergency event in pregnancy are reinforced.
Causes of Cardiopulmonary Arrest
Outside the hospital and in a coronary care unit setting, the most frequent cause of circulatory arrest is tachyarrhythmia, which occurs most often in patients with underlying heart disease. The most frequent initial rhythm in witnessed SCA is ventricular fibrillation (VF), the treatment for which centers around electrical defibrillation. The probability of successful defibrillation diminishes rapidly over time, and VF tends to deteriorate to asystole within a few minutes. For every minute that passes between collapse and defibrillation, survival rates from witnessed VF SCA decrease 7 to 10 percent if no CPR is provided.10 When bystander CPR is provided, the decrease in survival rates is more gradual and averages 3 to 4 percent per minute from collapse to defibrillation.10,11,12 If bystanders provide immediate CPR, many adults in VF can survive with intact neurologic function, especially if defibrillation is performed within approximately 5 minutes following SCA.13 This fact underscores the utility of the installation of automated external defibrillators (AEDs) in public places.
In contrast, primary respiratory events are much more common in hospitalized patients. Such events may be caused by acute respiratory failure, excessive sedation, pulmonary embolism, or airway obstruction. These principles should be kept in mind upon initiation of and throughout resuscitation efforts. For example, because an arrhythmia is likely to be the cause of sudden death
in the coronary care unit, a patient in cardiopulmonary arrest is almost always treated immediately with unsynchronized direct current (DC) cardioversion. In contrast, arrest situations on a general hospital unit are much more likely to be managed successfully if initial attention is devoted to airway management and oxygenation followed by a search for the cause of the crisis.
in the coronary care unit, a patient in cardiopulmonary arrest is almost always treated immediately with unsynchronized direct current (DC) cardioversion. In contrast, arrest situations on a general hospital unit are much more likely to be managed successfully if initial attention is devoted to airway management and oxygenation followed by a search for the cause of the crisis.
Primary Pulmonary Events
The term respiratory arrest refers to a situation in which a patient becomes unresponsive and without respirations, but an effective pulse is present. Failure to rapidly achieve effective ventilation and oxygenation results in progressive hypoxemia and acidemia that culminate in cardiovascular dysfunction, hypotension, and eventual circulatory collapse. The cause of many respiratory arrests relates to either respiratory center depression (e.g., excessive sedation) or to failure of respiratory muscles (e.g., excessive workload, impaired mechanical efficiency, excessive sedation, mucus plugging, or muscle weakness). The first compensatory response to respiratory compromise is usually tachypnea. However, as the increased workload of breathing continues, the respiratory effort and rhythm become slow, dysfunctional, and eventually cease.
Soon after ventilation ceases, the partial pressure of arterial oxygen (PaO2) dramatically decreases. Available stores of oxygen are limited and are consumed quickly. In contrast, carbon dioxide has a large storage reserve and an effective buffering system. If effective circulation is maintained, the partial pressure of arterial carbon dioxide (PaCO2) builds rather slowly, at a rate of 6 to 9 mmHg in the first apneic minute and 3 to 6 mmHg per minute thereafter.14 If the patient remains apneic and develops metabolic acidemia, H+ combines with HCO3 to generate carbon dioxide and water, dramatically increasing the rate of carbon dioxide production. Thus, life-threatening hypoxemia occurs long before significant respiratory acidemia.
Profound hypoxemia depresses neural function and produces bradycardia that is refractory to sympathetic and parasympatholytic influences. Cardiac output, the product of heart rate and stroke volume, thus decreases, which further impairs oxygen transport. The result of this process is a pulmocardiac arrest. Nearly half of hospitalized patients who suffer cardiac arrest exhibit an initial bradycardic rhythm, strongly suggesting a primary respiratory etiology.14
Primary Cardiovascular Events
The heart may become unable to maintain an adequate cardiac output because of a new arrhythmia or adverse alterations in preload, afterload, contractility, or heart rate. Intrinsic compensatory mechanisms, regulated via neurohormonal release of catecholamines, are subsequently activated in an attempt to improve cardiac output and oxygen transport. If appropriate interventions to correct the underlying problem are not initiated in a timely fashion, or if such interventions are not successful, profound hypoxemia ensues.
Neural tissue is disproportionately susceptible to hypoxemia and acidemia caused by decreased cardiac output. Circulatory arrest always produces loss of consciousness within seconds, and respiratory rhythm ceases very rapidly thereafter.14 The result of this process is a cardiopulmonary arrest. Thus, ongoing respiratory efforts indicate very recent cardiovascular collapse.
Although it is useful to consider cardiopulmonary arrest situations as primarily cardiac or pulmonary in origin, the context within which the event occurs should also be considered. Probable causes of cardiopulmonary arrest in common clinical settings and appropriate initial considerations are presented in Table 14-1.14
Causes of Cardiopulmonary Arrest in Pregnancy
Although it occurs infrequently during pregnancy, cardiopulmonary arrest is a complication for which the outcome is critically dependent on the underlying cause of the arrest and prompt initiation of resuscitation efforts. The causes of cardiopulmonary arrest during pregnancy have generally been divided into three categories: preexisting medical conditions, obstetric complications, and random, catastrophic events. In addition, iatrogenic factors also contribute to the incidence of cardiopulmonary arrest in pregnancy. The major causes of cardiac arrest during pregnancy that have been reported in the literature are listed in Box 14-1.15
Guidelines for Cardiopulmonary Resuscitation
CPR is not a single skill but rather refers to a series of assessments and interventions. In addition, cardiopulmonary arrest is not a single problem. As a consequence, the steps of CPR may vary depending on the type or etiology of the arrest. Because survival declines dramatically with time after arrest, most successfully resuscitated patients are revived within 5 to 10 minutes. The primary activities of resuscitation include:
airway management and ventilation
cardioversion/defibrillation
circulatory support
establishment of intravenous access
administration of drugs
performance of specialized procedures.
Basic Life Support
The steps of Basic Life Support (BLS) for adult patients consist of a series of sequential assessments and actions. These steps are depicted in the Simplified Adult BLS Healthcare Provider Algorithm presented in Figure 14-1. This algorithm incorporates evidence-based changes recommended by the AHA to promote more effective CPR.9 Key issues and major changes were included in the 2010 American Heart Association (AHA) Guidelines for CPR and ECC. These changes are designed to simplify lay rescuer training and to continue to emphasize the need to provide early chest compressions for the victim of a sudden cardiac arrest. A summary of changes in the 2010 AHA guidelines is presented in Table 14-2.
Table 14.1 Common Clinical Scenarios of Cardiopulmonary Arrest | ||||||||||||||||||||||||||||||||||||||||||||||||
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Box 14-1. Causes of Cardiopulmonary Arrest in Pregnancy
Venous thromboembolism
Preeclampsia/eclampsia
Sepsis
Amniotic fluid embolism (anaphylactoid syndrome of pregnancy)
Hemorrhage
Placental abruption
Placenta previa
Uterine atony
Disseminated intravascular coagulation
Trauma
Iatrogenic
Medication errors or allergy
Anesthetic complications
Hypermagnesemia
Preexisting heart disease
Congenital
Acquired
Recent studies have shown that half of all chest compressions administered by professional rescuers during CPR were too shallow and were interrupted too often.9 It is important to note that chest compressions administered by a rescuer generate only a small amount of blood flow compared to that generated by normal cardiac
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