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51. Cardiopulmonary Resuscitation
51.1 Introduction
Cardiac arrest in pregnancy is among the most challenging clinical scenarios. Although most features of resuscitating a pregnant woman follows same protocols as of adult resuscitation, but several aspects and considerations are uniquely different. The most obvious differences in pregnant woman resuscitation are that there are two lives involved in it, the mother and the fetus, and physiological changes in pregnancy, which are not there in nonpregnant adult patient. Inpatient sample from the USA nationwide suggests that cardiac arrest occurs in 1:12,000 admissions for delivery [1]. Globally, 800 maternal deaths occur daily [2, 3]. The Centers for Disease Control and Prevention have documented steady increase in maternal mortality trends in the USA, since 1989 to 2009, from 7.2 deaths per 100 000 live births in 1987 to 17.8 deaths per 1,00,000 live births in 2009 [4].
Management of cardiac arrest in pregnancy, labor, and delivery has received very limited attention. Knowledge deficits [5, 6]and poor resuscitation skills [7] could be major contributor to poor outcomes. Despite these problems, recent data show that the rate of survival after maternal cardiac arrest may be as high as 58.9% [1]; though higher than in most other arrest populations, this class of patients has mostly healthy bodies and comes into dangerous situation only due to exaggeration of physiological changes; thus further improvement of survival justifies appropriate training and preparation for such events despite their rarity.
The best outcome for neonatal survival is likely to be achieved only by successful maternal resuscitation. Some of the key steps in resuscitating a pregnant woman are timely initiation of uninterrupted chest compressions, left lateral displacement of uterus, midsternal hand positioning, use of small size endotracheal tube, continuous cricoid pressure, and intravenous access above the gravid uterine level; but there are many roadblocks in proper implementation of these protocols, which needs urgent attention.
First and foremost, since maternal cardiac arrest is such a rare occurrence on labor and delivery floors, obstetric care providers have very infrequent exposure to this catastrophic situation. Current advanced cardiac life support (ACLS) requirements and training are insufficient for sustaining resuscitation skills [8]. Surveys conducted on obstetric anesthesiologists, obstetricians, and emergency care physicians have found the knowledge regarding basic concepts of CPR in pregnant women to be grossly inadequate [5, 9]. They recommend that ACLS and CPR for parturients should be taught in a better manner and repeated at regular intervals to practitioners at all levels.
Secondly, the single most important step in successful resuscitation [10] is timely initiation of uninterrupted chest compressions along with recognition of cardiac rhythm and timely use of defibrillator. Further, titling the pregnant patient during the cardiac arrest usually takes time, resulting in significant uncalled interruptions in chest compressions. Supine manual leftward displacement (LUD) of the uterus has been found to be as effective as a left lateral tilt [11]. A recent simulation study shows [12] that this position could also be favorable for rescuers to perform high-quality supine chest compressions [13].
Thirdly, recent AHA guidelines emphasize more on initiating cesarean delivery within 4 min of maternal cardiac arrest [14]. Since 30% of the cardiac output is shunted to gravid uterus and unless the fetus is delivered within this time period, cardiac compressions may not be effective in maintaining the maternal cardiac output.
When performed, cesarean delivery should occur at the site of the arrest. Equipments for cesarean delivery should be readily available. Hospital should develop clear protocols to establish first responder’s role and have the appropriate number of staff to respond to a pregnant patient in cardiac arrest. Hospital should also have clear and effective system of activation of maternal cardiac arrest team, with roles clearly defined.
All the important factors related to maternal arrest, including maternal physiology, as it relates to resuscitation, causes of arrest, pre-event planning of the critically ill pregnant patient, risk stratification during pregnancy, management of the critically ill pregnant patient, basic life support (BLS), advanced cardiovascular life support (ACLS) in pregnancy, neonatal issues, emergency medical service (EMS) care, immediate postarrest care, medicolegal considerations (emergency doctrine principle works here, implying lack of intervention would have led to patient deterioration), and knowledge translation, training, and education recommendations, all are the hallmark of improving maternal cardiac arrest outcome.
51.2 Causes of Cardiac Arrest in Pregnancy
The most common causes of cardiac arrest are hemorrhage, cardiovascular diseases (myocardial infarction, aortic dissection, and myocarditis), amniotic fluid embolism, sepsis, aspiration pneumonitis, pulmonary embolism, and eclampsia [1, 15]. Important iatrogenic causes of maternal cardiac arrest include hypermagnesemia from magnesium sulfate administration and anesthetic complications.
Most common etiologies of maternal arrest and mortality
Letter | Cause | Etiology | |
|---|---|---|---|
A | Anesthetic complications Accident/trauma | High neuraxial block Hypotension Loss of airway Aspiration Respiratory depression Local anesthetic systemic toxicity Trauma Suicide | |
B | Bleeding | Coagulopathy Uterine atony Placenta accrete Placenta Abruption Placenta previa Retained product of conception Uterine rupture Surgical Transfusion reaction | |
C | Cardiovascular causes | Myocardial infarction Aortic dissection Cardiomyopathy Arrhythmias Valve disease Congenital heart disease | |
D | Drugs | Oxytocin Magnesium Drug error Opioids Insulin Anaphylaxis | |
E | Embolic causes | Amniotic fluid embolus Pulmonary embolus Cerebrovascular event Venous air embolism | |
F | Fever | Sepsis Infection | |
G | General | 5Hs | 5Ts |
Hypovolemia | Tension pneumothorax | ||
Hypoxia | Tamponade cardiac | ||
Hydrogen ion (acidosis) | Toxins | ||
Hypo-/hyperkalemia | Thrombosis pulmonary | ||
Hypothermia | Thrombosis coronary | ||
H | Hypertension | Preeclampsia Eclampsia HELLP syndrome Intracranial bleed | |
51.3 Important Physiological Changes in Pregnancy
Fetal development and maternal maintenance of pregnancy require multiorgan physiological adaptations that are important to understand for the team responding to cardiopulmonary arrest during pregnancy.
51.3.1 Cardiovascular System
Cardiac output rises 30–50% as a result of increased stroke volume and, to a lesser extent, increased maternal heart rate (15–20 bpm) [16, 17]. Systemic vascular resistance decreases as a result of an increase in several endogenous vasodilators, including progesterone, estrogen, and nitric oxide, leading to a decrease in mean arterial pressure, reaching a nadir in the second trimester [18]. The enlarging uterus can produce increased afterload through compression of the aorta and decreased venous return through compression of the inferior vena cava, starting at 12–14 weeks of gestational age [19]. As a result, the supine position, which is most favorable for resuscitation, can lead to hypotension [19, 20]. A magnetic resonance imaging study comparing the maternal hemodynamic in the left lateral position with those in the supine position was performed [21]. The study found that at 20 weeks of gestational age, there was a significant increase in ejection fraction of 8% and stroke volume of 27% in the left lateral position. At 32 weeks, there was increase in ejection fraction of 11%, in end-diastolic volume of 21%, in stroke volume of 35%, and in cardiac output of 24% in the left lateral position [21].
These changes put the heart in higher-than-normal workload adapted somewhat by hormone-induced decreased SVR which is partially obliterated by increasing gravid uterus. Thus very less margin for necessity to increase cardiac output is left in later half of pregnancy. Also there is significant compression of large vessels by the growing uterus which impedes resuscitation efforts.
Uteroplacental blood flow increases from 50 to close to 1000 mL/min during pregnancy, which is up to a maximum of 20% of maternal cardiac output at term [22]. Expanded intravascular space and a fall in uterine vascular resistance facilitate sufficient placental blood flow. Overall uterine vascular reactivity is altered, which is characterized by decreased tone, enhanced vasodilation, and blunted vasoconstriction, thus bringing the fetus in greater advantage in view of critically ill scenarios. Systemic hypotension though can overwhelm the compensatory mechanisms, which attempt to maintain uterine blood flow.
51.3.2 Respiratory System
Functional residual capacity decreases by 10–25% during pregnancy as the uterus enlarges and elevates the diaphragm. Increased ventilation (i.e., increase in tidal volume and minute ventilation) occurs, beginning in first trimester, reaching at a level 20–40% above baseline by term, mediated by the elevated serum progesterone level [23]. This produces a mild respiratory alkalosis with compensatory renal excretion of bicarbonate, resulting in an arterial carbon dioxide pressure of ~28–32 mmHg (3.7–4.3 kPa) and plasma bicarbonate level of 18–21 meq/L [24]. These changes mask the symptoms of some sinister problems like embolism which may lead to a “near-miss” situation.
Oxygen consumption increases because of the demand of fetus and maternal metabolic processes, reaching at a level 20–33% above baseline by third trimester [25]. The reduced functional residual capacity reservoir and increased consumption of oxygen are responsible for the rapid development of hypoxemia in response to hypoventilation or apnea in the pregnant woman [26].
The oxyhemoglobin dissociation curve is shifted to the right in the mother during pregnancy (P50 increases from 27 to 30 mmHg). A higher partial pressure of oxygen is therefore required to achieve the same maternal oxygen saturation. The same curve is shifted to the left in the fetus (P50 is 19 mmHg) conferring relative resilience to hypoxic conditions.
51.3.3 Airway
Upper airway edema and friability occur as a result of hormonal effects and may reduce visualization during laryngoscopy and increase the risk of bleeding; thus increased chances of ventilation and/or intubation failure are there. This, along with rapid occurrence of hypoxia in pregnancy, gives the obstetric anesthesiologists and obstetricians very less time to save two lives. Thus emergency kits with all working intubation aids should always be present in the labor room.
51.3.4 Renal System
Pregnancy is characterized by glomerular hyperfiltration and increased renal blood flow by 40% to accommodate for fetal detoxification of metabolic by-products too and maintenance of maternal osmoregulation (there is increased circulatory intravascular volume). Altered tubular function prevents wasting of glucose, amino acids, and proteins which are essential for both maternal and fetal metabolisms. On balance, Starling forces favor a narrowing of the oncotic pressure-wedge pressure gradient, increasing the tendency for pulmonary edema to develop [27].
51.3.5 Gastrointestinal System
Progesterone relaxes gastrointestinal sphincters and prolongs transit time throughout the intestinal tract during the second and third trimesters [28, 29] predisposing the patient to aspiration of stomach contents. Gravid uterus pushing gastroesophageal sphincter into thorax causes anatomical and, thus, physiological changes in it, thus aggravating the condition.
51.4 Gestational Age Estimation
Decisions made during a maternal cardiac arrest may require estimation of gestational age, though it is made unimportant in protocol-based guidelines. Symphysis fundal height is measured from the top of the maternal pubic bone to the top of the uterine fundus. In a singleton pregnancy, with the fetus in a longitudinal lie, this height in centimeters will approximately correspond to the period of gestation in weeks if measured between 16 and 36 weeks of gestation. If a tape measure is not available, finger breadths are usually used as a surrogate for the centimeters. Classically accepted rule-of-thumb landmarks may be used: Gestational age is 12 weeks if the uterus is palpable at above the pubic symphysis, 20 weeks if the uterus is palpable at the level of umbilicus [30], and 36 weeks if the uterus is palpable at the level of the xiphisternum. However fundus can be a poor predictor of the gestational age and may reach the umbilicus between 15 and 19 weeks of gestation [31]. In the last month of pregnancy, after 36 weeks of gestation, there may be diminution of the fundal height from 36 weeks down to ~32 weeks as the fetal head engages into the pelvis. Fundal height may also be skewed by other factors such as abdominal distention [30] and increased body mass index; therefore, fundal height may be a poor predictor of gestational age.
The rule of the thumb in maternal resuscitation is that if the gravid uterus is felt at the umbilicus, it is taken to be as of 20 weeks, the importance being that pregnant patient with uterus below umbilicus is managed with resuscitation protocols similar to adult nonpregnant patients, whereas if the uterus is felt at or above the umbilicus, it is taken to be causing significant aortocaval compression [20], and there are unique important changes in resuscitation protocols which are to be followed essentially.
51.5 The Critically Ill Pregnant Patient
51.5.1 Pre-event Planning
- 1.
Preparation for cardiac arrest: Educate staff about the management of cardiac arrest in pregnancy.
- 2.
Prepare for perimortem cesarean delivery (PMCD): Identify contacts details or appropriate code calls to mobilize the entire maternal cardiac arrest response team, and ensure the availability of equipment for cesarean delivery and resuscitation of the neonate. In cultures that require consent for a PMCD, even in the event of cardiac arrest, pre-event consent should be obtained.
- 3.
Preparation for management of obstetric complications: Stock drugs and equipment commonly available in obstetric units, including oxytocin and prostaglandin F2α. Pre-event planning for power of attorney related to healthcare decisions should be done for the critically ill patient.
- 4.
Decision involving the resuscitation status of the neonate: Decision about the fetal viability should be made in collaboration with the obstetrician, neonatologist, and family. The decision depends upon the gestational age and, to a significant degree, the neonatal facilities available. This information should be clearly documented.
51.5.2 Severity of Illness and Early Warning Scores
Warning score chart (Reference from Carle et al. [34] ). A score >6 should trigger a call for support from intensive care unit or rapid response team and initiation of continuous monitoring of vital signs. BP blood pressure, FiO 2 fraction of inspired O2, GCS Glasgow Coma Scale Score, Sat saturation
51.5.2.1 Management of the Unstable Pregnant Patient
Applying class of recommendations and level of evidence to clinical strategies, interventions, and treatment
51.5.3 Cardiac Arrest Management
51.5.3.1 Basic Life Support (BLS)
2015 Guidelines Update for adult CPR recommend that single rescuer should initiate chest compressions before giving rescue breaths (C-A-B rather than A-B-C) [36–38] to reduce delay to first compression. The single rescuer should begin CPR with 30 chest compressions followed by 2 breaths [39]. High-quality CPR constitutes five basic components, i.e., compressing the chest at an adequate rate and depth, allowing complete chest recoil after each compression, minimizing interruptions in compressions, and avoiding excessive ventilation. The recommended chest compression rate and depth are between 100 to 120/min and 2″–2.4″ (5–6 cm), respectively.
Summary of key BLS components for adults, children, and infants
Components | Adult and adolescent | Children (Age 1 year to puberty) | Infants (28 days to 1 year) |
|---|---|---|---|
Scene safety | Make sure the environment is safe for rescuer and victim | ||
Recognition of cardiac arrest | • Check for responsiveness • No breathing or no normal breathing (gasping only) • No pulse felt within 10 s • Breathing and pulse check can be performed simultaneously in less than 10 seconds (HCP only) | ||
Activation of emergency response system | Single rescuer with no mobile device: Leave the victim, and activate ERS, and get AED before staring CPR. Otherwise send someone, and start CPR immediately | Witnessed collapse • Follow steps for adults and adolescent on the left Unwitnessed collapse • Give 2 min of CPR • Leave victim to activate ERS and get AED • Return to the child and infant, and resume CPR; use the AED as soon as available | |
Compression ventilation ratio without advanced airway | 1 or 2 rescuers: 30:2 | 1 rescuer : 30:2 2 or more rescuers: 15:2 | |
Compression ventilation ration with advanced airway | Continuous compressions @ 100–120/min Give 1 breath every 6 s (10 breaths /min) | ||
Compression rate | 100–120/min | ||
Compression depth | At least 2 in. (5 cm) No >2.4 in. (6 cm) | At least 1/3 AP diameter of chest About 2 in. (5 cm) | At least 1/3 AP diameter about 1 1/2 in. (4 cm) |
Hand placement | 2 hands on lower half of sternum | 2 hands or 1 hand (optional for small child) on lower half of the sternum | 1 rescuer 2 fingers in the center of the chest just below the nipple line 2 or more rescuers 2 thump-encircling hands in the center of the chest, just below the nipple line |
Chest recoil | Allow full chest recoil after each compression; do not lean on the chest after each compression | ||
Minimizing interruptions | Limit interruptions in chest compressions to less than 10 s | ||
Healthcare provider Adult Cardiac Arrest Algorithm—2015 Update (Reference from 2015 AHA guidelines update for CPR & ECC)
51.5.4 Basic Life Support in Pregnancy
Cardiac arrest in pregnancy in-hospital basic life support (BLS) algorithm: simultaneous C-A-B-U (chest compressions-airway-breathing-uterine displacement). AED automated external defibrillator, CPR cardiopulmonary resuscitation, PEA pulseless electrical activity (Reference from AHA Scientific statement 2015)
51.5.4.1 First Responders
Nurses are often first responders in cardiac arrest; however, any hospital staff may witness or discover a patient in arrest and should be able to begin basic emergency care [40]. Rapid mobilization of expert resuscitation teams and BLS performed competently until the arrival of these teams give woman the best chance for return of spontaneous circulation (ROSC). First responder should initiate the usual resuscitation measures simultaneously, including placement of the backboard and provision of chest compressions, and appropriate airway management, defibrillation when appropriate, and manual left uterine displacement (LUD). To accomplish all tasks effectively, a minimum of four BLS responders should be present.
51.5.5 BLS Modifications
51.5.5.1 Adult Chest Compression Science
As with all adult resuscitations, high-quality chest compressions are essential to maximize the patient’s chance of survival. For high-quality chest compressions, the patient must be supine on hard surface (Class I; Level of Evidence C). Chest compressions must be performed at least 100 per minute but not exceeding 120 per minute, at a depth of at least 2 in (5 cm) but not exceeding 2.4 in. (6 cm), allowing full chest recoil before the next chest compression, with minimum interruptions, and at a compression/ventilation ratio of 30:2 [39] (Class IIa; Level of Evidence C). Interruptions should be minimized and limited to 10 s only except for specific interventions such as insertion of advanced airways or use of a defibrillator [39] (Class IIa; Level of Evidence C) because hospital beds are typically not firm and some of the force intended to compress the chest results in mattress displacement rather than chest compression.
51.5.6 Factors Affecting Chest Compressions in Pregnant Woman
51.5.6.1 Relief of Aortocaval Compression (LUD vs. LLT)
In the pregnant patient, supine positioning will result in aortocaval compression. Relief of aortocaval compression must be maintained continuously during resuscitative efforts and continued throughout postarrest care.
During resuscitation, manual LUD, either with one hand (Fig. 51.3a) or two hands (Fig. 51.3b), should be used to relieve aortocaval compression (Class I; Level of Evidence C). Previously, left lateral tilt had been the preferred option to relieve aortocaval compression during resuscitation.
Rees and Willis [41] found certain disadvantages, at >30° left lateral tilt: (1) The manikin slid off the inclined plane at >30° left lateral tilt. (2) Chest compression force was reduced as the angle of inclination was increased. (3) Inferior vena cava compression can still occur [42]. (4) In addition, the heart has been shown to shift laterally during tilt as compared with the supine position. Therefore, chest compressions performed with the patient in a tilt could be significantly less effective than those performed with the patient in the usual supine position, and this could have a major impact on the chance of successful resuscitation [41, 43].
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