Chapter 55: Cardiopulmonary Resuscitation

Cardiopulmonary resuscitation and emergency cardiac care (CPR-ECC) should be considered any time an individual cannot adequately oxygenate or perfuse vital organs—not only following cardiac or respiratory arrest.

This chapter presents an overview of the 2015 American Heart Association (AHA) Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, which provides revised recommendations for establishing and maintaining the “CABDs” of cardiopulmonary resuscitation: Circulation, Airway, Breathing, and Defibrillation (Table 55–1, Figures 55–1 and 55–2). The 2015 CPR-ECC guidelines have been updated with new evidence-based recommendations. Points of particular importance for the layperson are that the pulse should not be checked, and chest compression without ventilation may be as effective as compression with ventilation for the first several minutes. If a second lay rescuer is unavailable to perform mouth-to-mask ventilation, chest compressions alone are preferred to the primary rescuer attempting to do both. For the health care provider, defibrillation using biphasic electrical current works best and endotracheal tube (ETT) placement should be confirmed with a quantitative capnographic waveform analysis. More importantly, in the new guidelines, emphasis has been placed on the quality and adequacy of compressions, minimizing interruption time of compressions and preshock pause (the time taken from the last compression to the delivery of shock).

The sequence of steps in resuscitation has been changed since the 2010 guidelines from ABC (airway and breathing first, before compression) to CAB (compression first, with airway and breathing treated later). Based on the 2015 guidelines, titrating resuscitative efforts to physiological parameters does not improve outcome. Nonetheless, physiological monitoring methods to optimize CPR quality and return of spontaneous circulation (ROSC) are still useful. The rule of tens and multiples can be applied: less than 10 s to check for pulse, less than 10 s to place and secure the airway, target chest compression adequacy to maintain end-tidal pressure of carbon dioxide (PETCO₂) greater than 10 mm Hg, and target chest compression to maintain arterial diastolic blood pressure greater than 20 mm Hg and central venous oxygen saturation (SCVO₂) greater than 30%. The 2015 guidelines suggest that a lack of a PETCO₂ greater than 10 mm Hg after 20 min in an intubated patient may be considered as a marker to end resuscitative efforts. An exception to this determination applies to nonintubated patients, in whom a specific PETCO₂ cutoff should not be used to aid in the decision to end resuscitative efforts.

Changes in drug recommendations are notable for the exclusion of routine administration of high-dose epinephrine (0.1–0.2 mg/kg) during cardiac arrest. Additionally, vasopressin alone or in combination with epinephrine, according to the guidelines, offers no advantage over normal-dose epinephrine (1 mg every 3–5 min) in adult resuscitation following cardiac arrest. Amiodarone may be considered for ventricular fibrillation that is unresponsive to resuscitative efforts. Lidocaine is no longer recommended for routine use after cardiac arrest; however, it may be administered as an infusion following ROSC if the arrest occurred because of ventricular fibrillation or pulseless ventricular tachycardia. Additionally, β-blockers should not be used routinely in cardiac arrest (until after the CPR period has passed).

While the use of extracorporeal membrane oxygenation (ECMO, also referred to as extracorporeal cardiopulmonary resuscitation, ECPR) has been a topic of great interest and is increasingly available, the routine use of ECPR for cardiac arrest is not yet recommended. However, the guidelines suggest that when the etiology of the cardiac arrest is potentially reversible, the use of ECPR may be considered. The new guidelines also allow for the use of point-of-care ultrasound, but do not require it. Ultrasound techniques should only be performed by qualified personnel, and ultrasound interventions should not disrupt normal resuscitative practices and protocols.

This chapter is not intended as a substitute for a formal course in either life support without the use of special equipment (Basic Life Support [BLS]) or with the use of special equipment and drugs (Advanced Cardiac Life Support [ACLS]). Neonatal resuscitation is described in Chapter 41.

Before CPR is initiated, unresponsiveness is established and the emergency response system is activated. During low blood flow states such as cardiac arrest, oxygen delivery to the heart and brain is limited by blood flow rather than by arterial oxygen content; thus, current guidelines place greater emphasis on immediate initiation of chest compressions than on rescuer breaths.

The patient is positioned supine on a firm surface. After initiation of chest compressions, the airway is evaluated. The airway is most commonly obstructed by posterior displacement of the tongue or epiglottis. If there is no evidence of cervical spine instability, a head-tilt chin-lift should be tried first (Figure 55–3). One hand (palm) is placed on the patient’s forehead applying pressure to tilt the head back while lifting the chin with the forefinger and index finger of the opposite hand. The jaw-thrust may be more effective in opening the airway and is executed by placing both hands on either side of the patient’s head, grasping the angles of the jaw, and lifting. Basic airway management is discussed in detail in Chapter 19, and the trauma patient is considered in Chapter 39.

Any vomitus or foreign body visible in the mouth of an unconscious patient should be removed. If the patient is conscious or if the foreign body cannot be removed by a finger sweep, the Heimlich maneuver is recommended. This subdiaphragmatic abdominal thrust elevates the diaphragm, expelling a blast of air from the lungs that displaces the foreign body (Figure 55–4). Complications of the Heimlich maneuver include rib fracture, trauma to internal viscera, and regurgitation with aspiration. A combination of back blows and chest thrusts is recommended to clear foreign body obstruction in infants (Table 55–2).

If after opening the airway there is no evidence of adequate breathing, the rescuer should initiate assisted ventilation by inflating the victim’s lungs with each breath using a bag-mask device (see Chapter 19). Breaths are delivered slowly (inspiratory time of ½–1 s) at a rate of about 10 breaths/min, with smaller tidal volumes [VT] so as to minimize adverse effect on cardiac preload. Compressions (100–120/min) should not be suspended during two-person CPR to permit ventilation unless ventilation is not possible during compressions.

With positive-pressure ventilation, even with a small VT, gastric inflation with subsequent regurgitation and aspiration is possible. Therefore, as soon as feasible, the airway should be secured with an ETT, or, if that is not possible, an alternative airway should be inserted. There is inadequate evidence to support the optimal timing of the placement of an advanced airway (supraglottic device, ETT); however, chest compressions should not be more than minimally interrupted to place any advanced airway device. The benefit of an advanced airway must be considered in light of the risk of potential interruption in compressions. Advanced airways include the esophageal–tracheal Combitube (ETC), laryngeal mask airway (LMA), pharyngotracheal lumen airway, King laryngeal tube, and cuffed oropharyngeal airway. The ETC and LMA, along with oral and nasopharyngeal airways, face masks, laryngoscopes, and ETTs, are discussed in Chapter 19. Of these, the LMA is increasingly preferred for in-hospital arrests. The choice of bag-mask ventilation versus placement of an advanced airway is dependent upon the skills of the providers. Studies conflict as to optimal use of advanced airway management techniques in comparison to bag-mask ventilation.

Independent of which airway adjunct is used, the guidelines state that rescuers must confirm ETT placement with a PETCO₂ detector—an indicator, a capnograph, or a capnometric device. The preferred choice for confirmation of ETT placement is continuous capnographic waveform analysis. All confirmation devices are considered adjuncts to clinical conformation techniques (eg, auscultation). Once an artificial airway is successfully placed, it must be carefully secured with a tie or tape (25% of airways are displaced during transportation).

Some causes of airway obstruction may not be relieved by conventional methods. Furthermore, endotracheal intubation may be technically impossible to perform (eg, severe facial trauma), or repeated attempts may be unwise (eg, cervical spine trauma). In these circumstances, cricothyrotomy or tracheotomy may be necessary. Cricothyrotomy involves placing a large intravenous catheter or a commercially available cannula into the trachea through the midline of the cricothyroid membrane (Figure 55–5). Proper location is confirmed by aspiration of air. A 12- or 14-gauge catheter requires a driving pressure of 50 psi to generate sufficient gas flow for transtracheal jet ventilation. The catheter must be adequately secured to the skin, as the jet ventilation pressure can otherwise easily propel the catheter out of the trachea and, if the tip remains beneath the skin, lead to massive subcutaneous emphysema.

Various systems are available that connect a high-pressure source of oxygen (eg, central wall oxygen, tank oxygen, or the anesthesia machine fresh gas outlet) to the catheter (Figure 55–6). A hand-operated jet injector or the oxygen flush valve of an anesthesia machine controls ventilation. The addition of a pressure regulator minimizes the risk of barotrauma.

Regardless of which transtracheal jet ventilation system is chosen, it must be readily available, use low-compliance tubing, and have secure connections. Direct connection of a 12- or 14-gauge intravenous catheter to the anesthesia circle system does not allow adequate ventilation because of the high compliance of the corrugated breathing tubing and breathing bag. Similarly, one cannot reliably deliver acceptable ventilation through a 12- or 14-gauge catheter with a self-inflating resuscitation bag.

Adequacy of ventilation—particularly expiration—is judged by observation of chest wall movement and auscultation of breath sounds. Acute complications include pneumothorax, subcutaneous emphysema, mediastinal emphysema, bleeding, esophageal puncture, aspiration, and respiratory acidosis. Long-term complications include tracheomalacia, subglottic stenosis, and vocal cord changes. Cricothyrotomy is not generally recommended in children younger than 10 years of age.

Tracheotomy can be performed in a more controlled fashion after oxygenation has been restored by cricothyrotomy (see Chapter 19).

Assessment of spontaneous breathing should immediately follow the opening or the establishment of the airway. Chest compressions and ventilation should not be delayed for intubation if a patent airway is established by a jaw-thrust maneuver; intubation may take place during CPR or the pulse check. Apnea is confirmed by lack of chest movement, absence of breath sounds, and lack of airflow. Regardless of the airway and breathing methods employed, a specific regimen of ventilation has been proposed for the apneic patient and described earlier in this chapter. Initially, two breaths are slowly administered (2 s per breath in adults, 1–1½ s in infants and children). If these breaths cannot be delivered, either the airway is still obstructed and the head and neck need repositioning or a foreign body is present that must be removed.

Bag-mask rescue breathing should be instituted in the apneic patient when these devices are immediately available. Supplemental oxygen, preferably 100%, should always be used if available. Successful rescue breathing, 400–700 mL VT, 8–10 times per minute in an adult with a secured airway and a ratio of 30 compressions to 2 ventilations if the airway is unsecured, is confirmed by observing the chest rising and falling with each breath and hearing and feeling the escape of air during expiration

Devices that avoid use of the provider’s mouth should be immediately available everywhere in the hospital. Ventilation with a mask may be performed in most patients by adjusting the airway or making the airtight seal more effective (see Chapter 19). Use of cricoid pressure to prevent regurgitation during cardiac arrest resuscitation may be considered; however, there are no data to support its efficacy in this (or any other) circumstance and its routine use is not recommended.

Endotracheal intubation by competent personnel should be attempted as soon as practical. Attempts at endotracheal intubation should not interrupt ventilation for more than 10 s. After intubation, the patient can be ventilated with high oxygen concentrations. A rate of 8 to 10 breaths/min should be maintained, as higher ventilatory rates may impede cardiac output during CPR in a cardiac arrest situation.

The ratio of physiological dead space to tidal volume (VD/VT) reflects the efficiency of CO₂ elimination. VD/VT increases during CPR as a result of low pulmonary blood flow and high alveolar pressures. Thus, minute ventilation may need to be increased by 50% to 100% once circulation is restored as CO₂ from the periphery is brought back to the lungs.

Circulation takes precedence over airway interventions and breathing in the cardiac arrest patient. As previously noted, chest compressions should begin prior to the delivery of breaths. Subsequent actions to assess circulation may then vary depending on whether the responder is a lay person or health care provider. Although lay rescuers should assume that an unresponsive patient is in cardiac arrest and need not check the pulse, health care providers should assess for presence or absence of a pulse.

If the patient has an adequate pulse (carotid artery in an adult or child, brachial or femoral artery in an infant) or blood pressure, breathing is continued at 10 to 12 breaths/min for an adult or a child older than 8 years, and 20 breaths/min for an infant or a child younger than 8 years of age (Table 55–2). If the patient is pulseless or severely hypotensive, the circulatory system must be supported by a combination of external chest compressions, intravenous drug administration, and defibrillation when appropriate. Initiation of chest compressions is mandated by the inadequacy of peripheral perfusion, and drug choices and defibrillation energy levels often depend on electrocardiographic diagnosis of arrhythmias.

External Chest Compression

Chest compressions force blood to flow either by increasing intrathoracic pressure (thoracic pump) or by directly compressing the heart (cardiac pump). During CPR of short duration, the blood flow is created more by the cardiac pump mechanism; as CPR continues, the heart becomes less compliant and the thoracic pump mechanism becomes more important. As important as the rate and force of compression are for maintaining blood flow, effective perfusion of the heart and brain is best achieved when chest compression consumes 50% of the duty cycle, with the remaining 50% devoted to the relaxation phase (allowing blood return into the chest and heart).

To perform chest compressions in the unresponsive or pulseless patient, the xiphoid process is located and the heel of the rescuer’s hand is placed over the lower half of the sternum. The other hand is placed over the hand on the sternum with the fingers either interlaced or extended, but off the chest. The rescuer’s shoulders should be positioned directly over the hands with the elbows locked into position and arms extended, so that the weight of the upper body is used for compressions. With a straight downward thrust, the sternum is depressed approximately 2 in. (5 cm) in adults, 1 to 1½ in. (2–4 cm) in children, and then allowed to return to its normal position. For an infant, compressions ½ to 1 in. (1½–2½ cm) in depth are made with the middle and ring fingers on the sternum one finger-breadth below the nipple line. Compression and release times should be equal.

Whether adult resuscitation is performed by a single rescuer or by two rescuers, two breaths are administered every 30 compressions (30:2), allowing 3 to 4 s for the two breaths. The cardiac compression rate should be 100/min regardless of the number of rescuers. A slightly higher compression rate of more than 100/min is suggested for infants, with two breaths delivered every 30 compressions.

Assessing the Adequacy of Chest Compressions

Adequacy of cardiac output can be estimated by monitoring PETCO₂ (>10 mm Hg), SCVO₂ (>30%), or arterial pulsations (with arterial diastolic relaxation pressure >20 mm Hg). Arterial pulsations during chest compressions are not a good measure of adequate chest compression; however, spontaneous arterial pulsations are an indicator of ROSC. Physiological parameters, such as PETCO₂, SCVO₂, and diastolic arterial pressure, may aid in assessing the adequacy of chest compressions but cannot be used exclusively to determine if CPR should be discontinued.

1. PETCO₂

In an intubated patient, a PETCO₂ greater than 10 mm Hg indicates good-quality chest compressions; a PETCO₂ less than 10 mm Hg has been shown to be a predictor of poor outcomes of CPR (decreased chance of ROSC) in CPR of more than 20 min duration. A transient increase in PETCO₂ may be seen with administration of sodium bicarbonate; however, an abrupt and sustained rise of PETCO₂ is an indicator of ROSC.

2. Coronary perfusion pressure (CPP)

This is the difference between the aortic diastolic pressure and the right atrial diastolic pressure. Arterial diastolic pressure in the radial, brachial, or femoral artery is a good indicator of CPP. Arterial diastolic pressure greater than 20 mm Hg is an indicator of adequate chest compressions.

3. SCVO₂

An SCVO₂ less than 30% in the jugular vein is associated with poor outcomes. If the SCVO₂ is less than 30%, attempts to improve the quality of CPR, either by improving the quality of compressions or through administration of medications, should be considered.

Ventricular fibrillation is found most commonly in adults who experience nontraumatic cardiac arrest. The time from collapse to defibrillation is the most important determinant of survival. The chances for survival decline 7% to 10% for every minute without defibrillation (Figure 55–7). Therefore, patients who have cardiac arrest should be defibrillated at the earliest possible moment. Health care personnel working in hospitals and ambulatory care facilities must be able to provide early defibrillation to collapsed patients with ventricular fibrillation as soon as possible. Shock should be delivered within 3 to 4 min of arrest.

There is no definite relationship between the energy requirement for successful defibrillation and body size. A shock with too low an energy level will not successfully defibrillate; conversely, too high an energy level may result in myocardial injury. Defibrillators deliver energy in either monophasic or biphasic waveforms. Biphasic waveforms are recommended for cardioversion as they achieve the same degree of success but with less energy and theoretically less myocardial damage; newly manufactured defibrillators use biphasic waveforms.

In many institutions, automated external defibrillators (AEDs) are available. Such devices are increasingly being used throughout communities by police, firefighters, security personnel, sports marshals, ski patrol members, and airline flight attendants, among others. They are placed in any public location where 20,000 or more people pass by every day. AEDs are technologically advanced, microprocessor-based devices that are capable of electrocardiographic analysis with very high specificity and sensitivity in differentiating shockable from nonshockable rhythms. All AEDs manufactured today deliver some type of biphasic waveform shock. Compared with monophasic shocks, biphasic shocks deliver energy in two directions with equivalent efficacy at lower energy levels and possibly with less myocardial injury. These devices deliver impedance-compensating shocks employing either biphasic truncated exponential (BTE) or rectilinear (RBW) morphology. Biphasic shocks delivering low energy for defibrillation (120–200 joule [J]) have been found to be as or more effective than 200 to 360 J monophasic damped sine (MDS) waveform shocks. When using AEDs, one electrode pad is placed beside the upper right sternal border, just below the clavicle, and the other pad is placed just lateral to the left nipple, with the top of the pad a few inches below the axilla.

A decrease in time delay between the last compression and the delivery of a shock (the preshock pause) has received special emphasis in the new guidelines. Stacking shocks (delivering two or more shocks in immediate succession without intervening compressions) increases the time to next compression, and it has been noted that the first shock is usually associated with a 90% efficacy. Thus, stacked shocks have been replaced by a recommendation for a single shock, followed by immediate resumption of chest compressions.

For cardioversion of atrial fibrillation (Table 55–3), 120–200 J can be used initially with escalation if needed. For atrial flutter or paroxysmal supraventricular tachycardia (PSVT), an initial energy level of 50 to 100 J is often adequate. All monophasic shocks should start with 200 J. Manufacturer instructions typically provide the recommended starting shock energy level specific to the device.

Ventricular tachycardia, particularly monomorphic ventricular tachycardia, responds well to shocks at initial energy levels of 100 J. For polymorphic ventricular tachycardia or for ventricular fibrillation, initial energy can be set at 120 to 200 J, depending upon the type of biphasic waveform being used. Stepwise increases in energy levels can be used if the first shock fails, although some AEDs operate with a fixed-energy protocol of 150 J with very high success in terminating ventricular fibrillation (Table 55–3).

Cardioversion should be synchronized with the QRS complex and is recommended for hemodynamically stable, wide-complex tachycardia requiring cardioversion, PSVT, atrial fibrillation, and atrial flutter. Polymorphic ventricular tachycardia should be treated as ventricular fibrillation with unsynchronized shocks.

Invasive Cardiopulmonary Resuscitation

Thoracotomy and open-chest cardiac massage are not part of routine CPR because of the frequent incidence of complications. Nonetheless, these invasive techniques can be helpful in specific life-threatening circumstances that preclude effective closed-chest massage. Possible indications include cardiac arrest associated with penetrating or blunt chest trauma, penetrating abdominal trauma, severe chest deformity, pericardial tamponade, or pulmonary embolism. Extracorporeal membrane oxygenation is increasing employed when the cause of arrest (eg, local anesthetic systemic toxicity) is reversible.

Intravenous Access

Even though establishing reliable intravenous access is a high priority, it should not take precedence over initial chest compressions, airway management, or defibrillation. A preexisting internal jugular or subclavian catheter is ideal for venous access during resuscitation. If there is no central line access, an attempt should be made to establish peripheral intravenous access in either the antecubital or the external jugular vein. Peripheral intravenous sites are associated with a significant delay of 1 to 2 min between drug administration and delivery to the heart, as peripheral blood flow is drastically reduced during CPR. Administration of drugs given through a peripheral intravenous line should be followed by an intravenous flush (eg, a 20-mL fluid bolus in adults) or elevation of the extremity for 10 to 20 s, or both. Establishing central vein access can potentially cause interruption of CPR but should be considered if an inadequate response is seen to peripherally-administered drugs.

If intravenous cannulation is difficult, an intraosseous infusion can provide emergency vascular access in children and adults. A rigid 18-gauge spinal needle with a stylet or a small bone marrow trephine needle can be inserted into the distal femur or proximal tibia. If the tibia is chosen, a needle is inserted 2 to 3 cm below the tibial tuberosity at a 45° angle away from the epiphyseal plate (Figure 55–8). Once the needle is advanced through the cortex, it should stand upright without support. Correct placement is confirmed by the ability to aspirate marrow through the needle and deliver a smooth infusion of fluid. A network of venous sinusoids within the medullary cavity of long bones drains into the systemic circulation by way of nutrient or emissary veins. This route is very effective for administration of drugs, crystalloids, colloids, and blood and can achieve flow rates exceeding 100 mL/h under gravity. Much higher flow rates are possible if the fluid is placed under pressure (eg, 300 mm Hg) with an infusion bag. The onset of drug action may be slightly delayed compared with intravenous or tracheal administration. The intraosseous route may require a higher dose of some drugs (eg, epinephrine) than recommended for intravenous administration. The use of intraosseous infusion for induction and maintenance of general anesthesia, antibiotic therapy, seizure control, and inotropic support has been described. (Note that most studies have evaluated the placement of intraosseous access in patients with intact hemodynamics or hypovolemic states, not in cardiac arrest situations.) Because of the risks of osteomyelitis and compartment syndrome, however, intraosseous infusions should be replaced by a conventional intravenous route as soon as possible. In addition, because of the theoretical risk of bone marrow or fat emboli, intraosseous infusions should be avoided if possible in patients with right-to-left shunts, pulmonary hypertension, or severe pulmonary insufficiency. Some resuscitation drugs are fairly well absorbed following administration through an ETT. Lidocaine, epinephrine, atropine, naloxone, and vasopressin (but not sodium bicarbonate) can be delivered via a catheter whose tip extends past the ETT. Notably, the American Heart Association recommends endotracheal dosing only when IV and intraosseous dosing cannot be accomplished. Dosages 2 to 2½ times higher than recommended for intravenous use, diluted in 10 mL of normal saline or distilled water, are recommended for adult patients.

Arrhythmia Recognition

Successful pharmacological and electrical treatment of cardiac arrest (Figure 55–9) depends on definitive identification of the underlying arrhythmia. Interpreting rhythm strips in the midst of a resuscitation situation is frequently complicated by artifacts and variations in monitoring techniques (eg, lead systems, equipment).

Drug Administration

Many of the drugs administered during CPR have been described elsewhere in this text. Table 55–4 summarizes the cardiovascular actions, indications, and dosages of drugs commonly used during resuscitation.

Atropine is not included as a drug for pulseless electrical activity/asystole in the new CPR-ECC guidelines; however, its use is retained for symptomatic bradycardia. Infusions of chronotropic drugs (eg, dopamine, epinephrine, isoproterenol) can be considered as an alternative to pacing if atropine is ineffective in the setting of symptomatic bradycardia. Calcium chloride, sodium bicarbonate, and bretylium are conspicuously absent from this table. Calcium (2–4 mg/kg of the chloride salt) is helpful in the treatment of documented hypocalcemia, hyperkalemia, hypermagnesemia, or a calcium channel blocker overdose. When used, 10% calcium chloride can be given at 2 to 4 mg/kg every 10 min. Sodium bicarbonate (0.5–1 mEq/kg) is not recommended in the guidelines and should be considered only in specific situations such as preexisting metabolic acidosis or hyperkalemia, or in the treatment of tricyclic antidepressant or barbiturate overdose. Sodium bicarbonate elevates plasma pH by combining with hydrogen ions to form carbonic acid, which readily dissociates into carbon dioxide and water. Because carbon dioxide, but not bicarbonate, readily crosses cell membranes and the blood–brain barrier, arterial hypercapnia causes intracellular tissue acidosis. Although successful defibrillation is not related to arterial pH, increased intramyocardial carbon dioxide may reduce the possibility of successful cardiac resuscitation. Furthermore, bicarbonate administration can lead to detrimental alterations in osmolality and the oxygen–hemoglobin dissociation curve. Therefore, effective alveolar hyperventilation and adequate tissue perfusion are the treatments of choice for the respiratory and metabolic acidosis that accompany resuscitation.

Intravenous fluid therapy with either colloid or balanced salt solutions is indicated in patients with intravascular volume depletion (eg, acute blood loss, diabetic ketoacidosis, thermal burns). Dextrose-containing solutions may lead to a hyperosmotic diuresis and may worsen neurological outcome. They should be avoided unless hypoglycemia is suspected. Likewise, administration of free water (eg, D₅W) may lead to cerebral edema.

Emergency Pacemaker Therapy

Transcutaneous cardiac pacing (TCP) is a noninvasive method of rapidly treating arrhythmias caused by conduction disorders or abnormal impulse. TCP is not routinely recommended in cardiac arrest. TCP use may be considered to treat asystole, bradycardia caused by heart block, or tachycardia from a reentrant mechanism. If there is concern about the use of atropine in high-grade block, TCP is always appropriate. If the patient is unstable with marked bradycardia, TCP should be implemented immediately while awaiting treatment response to drugs. A pacemaker unit has become a built-in feature of some defibrillator models. Disposable pacing electrodes are usually positioned on the patient in an anterior–posterior manner. The placement of the negative electrode corresponds to a V₂ electrocardiograph position, whereas the positive electrode is placed on the left posterior chest beneath the scapula and lateral to the spine. Note that this positioning does not interfere with paddle placement during defibrillation. Failure to capture may be due to electrode misplacement, poor electrode-to-skin contact, or increased transthoracic impedance (eg, barrel-shaped chest, pericardial effusion). Current output is slowly increased until the pacing stimuli obtain electrical and mechanical capture. A wide QRS complex following a pacing spike signals electrical capture, but mechanical (ventricular) capture must be confirmed by an improving pulse or blood pressure. Conscious patients may require sedation to tolerate the discomfort of skeletal muscle contractions. Transcutaneous pacing can provide effective temporizing therapy until transvenous pacing or other definitive treatment can be initiated. TCP has many advantages over transvenous pacing because it can be used by almost all acute care providers and can be initiated quickly at the bedside.

Precordial Thump

The precordial thump is to be considered only in witnessed, monitored, pulseless ventricular tachycardia when a defibrillator is not immediately available. It provides only 5 to 10 joules of mechanical energy to the heart. Recent studies suggest the precordial thump rarely results in ROSC and usually results in either no change in rhythm or deterioration into ventricular fibrillation or asystole. The latter situation may represent the phenomenon known as commotio cordis, where blunt impact to the chest without structural trauma results in ventricular arrhythmias or asystole.

A resuscitation team leader integrates the assessment of the patient, including electrocardiographic diagnosis, with the electrical and pharmacological therapy (Table 55–5). This person must have a firm grasp of the guidelines for cardiac arrest presented in the CPR-ECC algorithms (Figures 55–9,55–10,55–11,55–12,55–13).