e56 SECTION XV Pediatric Critical Care Board Review Questions Rationale Hypotension and cardiovascular collapse in patients after heart transplantation are related to decrease in systemic vascular res[.]
e56 S E C T I O N XV Pediatric Critical Care: Board Review Questions Rationale Hypotension and cardiovascular collapse in patients after heart transplantation are related to decrease in systemic vascular resistance rather than primary myocardial dysfunction Large fluid volumes and high-dose inotropic agents at a-adrenergic dosing range are administered, causing volume overload and vasoconstriction that can injure all donor organs Hearts that are supported on high-dose inotropic agents likely will exhibit myocardial injury A risk factor that predicts donor heart failure is a history of high-dose dopamine, dobutamine greater than 20 mg/ kg/min, and epinephrine greater than 0.1 mg/kg/min 12 A 5-year old child with dilated cardiomyopathy in your pediatric intensive care unit is waiting for an orthotopic heart transplant The child’s weight is 20 kg She is receiving intermittent noninvasive continuous positive airway pressure Her mixed venous oxygen saturation is 45%, and her left ventricular ejection fraction (LVEF) is less than 20% Inotropic support includes a milrinone drip of 0.75 mg/kg/min and an epinephrine drip of 0.02 mg/kg/min A donor organ becomes available within hour of flying time from your medical center The donor is a teenager who became brain dead after a motor vehicle accident days ago The donor weight is 40 kg Resuscitation at the accident site was required with unknown down time Vasopressin and epinephrine were initiated and given for the first 24 hours but subsequently weaned to low-dose dopamine Current evaluation of the donor heart shows an LVEF of 60% with trivial mitral valve regurgitation Would you recover this donor heart for your patient? A No; the uncertain down time and high-dose inotropic support make the donor unacceptable B No; the donor is too large for my patient C No; the distance from the center makes it impossible for ischemic time to be less than hours D Possibly; the donor is potentially acceptable I would review all of the information from the donor site Preferred response: D Rationale Donor heart availability is limited, and the number of patients who die while waiting for a heart transplant is significant Your recipient is critically ill, and the need for circulatory support is imminent (via extracorporeal membrane oxygenation or a ventricular support device), so all potential donor hearts should be critically evaluated An estimate of donor “down time” is important but often inaccurate Inotropic resuscitation of the donor is common The use of high-dose inotropic support (i.e., epinephrine and norepinephrine) for a prolonged period of time (.24 hours) reflects significant donor heart ischemia, and in such cases the donor heart should not be used for transplantation A donor/ recipient weight of greater than 2:1 is common We use the donor/ recipient aortic root size rather than weight to estimate the size mismatch We rarely use an undersized donor (i.e., weight less than 20% of the recipient) for transplantation Flight time from the transplant center is relative Ideally a total ischemic time of less than hours is ideal (i.e., the time from aortic cross-clamp at the donor site to release of the aortic cross-clamp on the recipient) It is important to remember that a perfect heart to transplant is never available We encourage direct verbal communication with the donor referral center 13 A 15-year old patient with tricuspid atresia has had palliative surgery (atrial to pulmonary connection) (Fontan) A myopathic ventricular dysfunction and protein-losing enteropathy have developed He has just had an orthotopic transplant You are discussing potential immune suppression regimens Pretransplant panel reactive antibody is 10% for class human leukocyte antigens Which of the following is of major concern for renal dysfunction in the early perioperative course after heart transplantation? A Antithymocyte globulin (ATG) B Basiliximab C Methylprednisolone D Mycophenolate E Tacrolimus Preferred response: E Rationale Immunosuppression protocols are similar from center to center with generally only small variations Initial immune suppression protocols typically include high-dose corticosteroids, induction with IL-2 receptor blockade (e.g., basiliximab) or antithymocyte globulin (ATG), followed within approximately 48 hours by introduction of a calcineurin inhibitor (CNI) such as cyclosporine or tacrolimus Induction protocols using IL-2 receptor antagonists or ATG are effective in delaying the time to first allograft rejection episode and the time needed to initiate CNI medications, which is especially useful when there is significant renal dysfunction Induction therapy also reduces the risk of death due to rejection, although it does not appear to have a long-term survival benefit, except possibly in those with a PRA 50% or diagnosis of congenital heart disease Induction therapy may also be useful in steroid avoidance protocols Some centers not use induction therapy under particular circumstances due to concerns for risk of infection or viral reactivation, although that has not been borne out in recent studies Corticosteroids have been part of standard protocols since the early days of solid organ transplantation High-dose methylprednisolone (5 to 10 mg/kg) is administered at the time of aortic cross-clamp removal and continued in tapering doses over the first several days after surgery Corticosteroids have immunosuppressive properties and benefit the allograft because of membranestabilizing and antioxidant effects on the graft Steroid-sparing/ steroid-avoidance protocols exist for other solid organ transplants and are in development for heart transplantation More controversial is the timing of the introduction of the CNIs cyclosporine and tacrolimus A major complication in the early perioperative course after heart transplantation is renal dysfunction; in the past, CNIs were major contributors Acute kidney injury is a major complication following orthotopic heart transplantation It is often multifactorial in etiology, as the premorbid risk factors of heart transplant recipients cannot necessarily be controlled One must monitor and control use of calcineurin-inhibitor immune suppression agents, especially when renal dysfunction is present or expected Therapeutic strategies include delaying the initiation of cyclosporine and tacrolimus by using antithymocyte globulin or IL-2 receptor blockade for induction of immune suppression The other option is to use a modified oral/ nasogastric protocol for tacrolimus administration This protocol targets tacrolimus levels to below ng/mL in the first days after transplantation, followed by a rapid increase in dosing and target CHAPTER 136 Board Review Questions level over the next days It is important to avoid early IV administration of these agents because they invariably lead to renal afferent arteriolar vasoconstriction and oliguria If renal dysfunction is complicating the posttransplant course, it is still difficult to withdraw CNIs completely, but lowering the target level to less than ng/L and substituting higher doses of mycophenolate mofetil and adding sirolimus are reasonable options 14 An 8-year old girl with restrictive cardiomyopathy is being evaluated for transplant A hemodynamic study is performed as part of the pretransplant evaluation Hemodynamics are as follows: blood pressure, 110/80 mm Hg; pulmonary artery, 62/40 mm Hg, mean 50 mm Hg; pulmonary artery wedge, 35 mm Hg; left ventricular end-diastolic pressure, 35 mm Hg; and cardiac index, 2.5 L/min/m2 What is your decision regarding this patient’s suitability for orthotopic heart transplant? A Before making a decision, hemodynamics should be repeated with a fraction of inspired oxygen of 1.0 and nitric oxide B Listing the patient for a heart transplant should be delayed until medical management of pulmonary hypertension can be initiated C The patient is a candidate for heart and lung transplant only D The patient is a candidate for orthotopic heart transplant with a recognized increased risk factor of elevated pulmonary vascular resistance (PVR) Preferred response: D Rationale The evaluation of pulmonary vascular resistance (PVR) in the potential heart transplant recipient is a critical part of the evaluation The right ventricle of the donor heart will acutely fail if it is exposed to excessive afterload from pulmonary vascular disease of the recipient A pretransplant hemodynamic assessment with conditions favoring pulmonary vasodilation using oxygen, nitric oxide, and or nitroprusside is necessary to determine if the recipient is an orthotopic heart transplant candidate alone or will need to be referred for a heart and lung transplant A transpulmonary gradient (pulmonary artery mean pressure–left atrial pressure) of less than 15 mm Hg or an estimated PVR index of less than to units/m2 is acceptable level of PVR for orthotopic heart transplantation Chapter 38: Physiologic Foundations of Cardiopulmonary Resuscitation The odds of death are increased after extracorporeal cardiopulmonary resuscitation (E-CPR) with the following risk factors? A Age B Preexisting renal insufficiency C Shorter CPR times prior to ECMO D Venovenous (VV) ECMO Cannulation Preferred response: B Rationale Data from the Extracorporeal Life Support Organization and AHA “Get with the Guidelines-Resuscitation” registries to determine risk factors related to unfavorable outcomes with E-CPR among 593 children In this study they found that odds of death were increased with a noncardiac diagnosis and preexisting renal insufficiency, and that for each additional minutes of CPR prior to ECMO initiation, the odds risk of death increased by 1.04 e57 Age was not found to increase the odds of death Longer CPR times (rather than shorter times) were found to have increased risk of death E-CPR refers to veno-arterial rather than venovenous cannulation Cerebral blood flow during CPR is increased with the following medication? A Dexmedetomidine B Metoprolol C Milrinone D Phenylephrine Preferred response: D Rationale Cerebral blood flow during CPR depends on peripheral vasoconstriction that can be enhanced using an a-adrenergic agonist or arginine vasopressin receptor agonist (V1 receptor) This action produces selective vasoconstriction of noncerebral peripheral vessels to areas of the head and scalp without causing cerebral vasoconstriction As with myocardial blood flow, pure a-agonist agents are as effective as epinephrine in generating and sustaining cerebral blood flow during CPR in adult animal models and in infant models A b-blocking agent such as metoprolol (b1 adrenergic receptor) would have a negative effect on cardiac output and no direct effect on systemic vascular resistance A selective a2 adrenoreceptor agonist such as dexmedetomidine would activate G-proteins via a2a adrenoreceptors in the brainstem and inhibit norepinephrine release, causing no effect on the peripheral vasculature Finally, use of a selective phosphodiesterase inhibitor such as milrinone would induce inhibition of cardiac and vascular tissue, resulting in vasodilation What is the most common presenting rhythm in a pediatric patient in cardiac arrest? A Asystole B Bradycardia C Torsades de pointes D Ventricular fibrillation Preferred response: A Rationale Asystole is the most common presenting rhythm in a pediatric patient who presents in cardiac arrest, noted in 25–70% of victims Bradycardia and pulseless electrical activity (PEA) are other common rhythms, while ventricular rhythms are infrequent Systemic disturbances, such as hypoxia, acidosis, sepsis, and hypovolemia, often precede the arrest and lead to the asystole rhythm A 16-year-old male with no previous medical history had a witnessed collapse on the basketball court, and the automated external defibrillator (AED) recommended defibrillation, which was given The patient arrives to your emergency room in cardiac arrest, having received several rounds of CPR with defibrillation attempts Which antiarrhythmic would NOT be appropriate? A Amiodarone B Lidocaine C Procainamide D Sotalol Preferred response: D e58 S E C T I O N XV Pediatric Critical Care: Board Review Questions Rationale Sotalol is not an appropriate antiarrhythmic choice for a ventricular arrhythmia in an acute cardiac arrest According to the 2015 AHA guidelines, amiodarone and lidocaine are appropriate first-line agents, though neither has been shown to have a survival benefit over the other Amiodarone given intravenously may depress myocardial function and lead to hemodynamic collapse, which may not be a concern in a patient undergoing active cardiopulmonary resuscitation The halflife of amiodarone is on the magnitude of days, so it will take several doses to appropriately load a patient It is contraindicated in patients with torsades de pointes as it increases the QTc and would exacerbate the arrhythmia Lidocaine has a shorter half-life (5–10 minutes) though it may depress myocardial function at high plasma concentrations Procainamide may also be used to treat ventricular arrhythmias, though like amiodarone it also prolongs the QTc What is the major pharmacologic effect of epinephrine during cardiopulmonary resuscitation? A It raises aortic systolic pressure B It raises aortic diastolic pressure C It raises the heart rate via its b-agonist actions D It improves cardiac compliance by relaxing myocardium during diastole Preferred response: B Rationale At resuscitative doses of epinephrine, the a-adrenergic receptor effect predominates, increasing systemic vascular resistance in addition to increasing cardiac output The a-adrenergic–mediated vasoconstriction of epinephrine increases aortic diastolic pressure and thus coronary perfusion pressure, a critical determinant of successful resuscitation At nonresuscitative doses, epinephrine has potent b1-adrenergic receptor activity and moderate b2- and a1-adrenergic receptor ef- Bed 23 JUN 98 11:52 ***VENT TACHY HR 136 II VPB 11 fects Clinically, low doses of epinephrine increase cardiac output because of the b1-adrenergic receptor inotropic and chronotropic effects, whereas the a-adrenergic receptor–induced vasoconstriction is often offset by the b2-adrenergic receptor vasodilation The result is an increased cardiac output, with decreased systemic vascular resistance and variable effects on the mean arterial pressure Compared with monophasic defibrillators, which of the following is true about biphasic defibrillators? A They are too expensive and have an unacceptable fault rate B They have been shown to burn too much myocardium in smaller children C They require less energy output to be effective D They should be used at one-fourth the starting dose in children Preferred response: C Rationale Defibrillators can deliver energy in a variety of waveforms that are broadly characterized as monophasic or biphasic Biphasic waveforms defibrillate more effectively and at lower energies than monophasic waveforms The value of higher energy biphasic shocks was demonstrated in the BIPHASIC trial A 16-year-old female with a history of chronic medications, including metoclopramide, ondansetron, and erythromycin, presents conscious with the tracing shown in Figure 136.15, below Which of the following antiarrhythmic agents would be most appropriate in the acute setting? A Adenosine B Amiodarone C Lidocaine D Procainamide Preferred response: C Sp02 98 ST1 0.0 ST2 –0.8 ST3 0.4 PULSE 68 25 mm/sec (0BMIA10) [AI002] aVL • Fig 136.15 Rationale Due to her medication profile, this patient is at risk for acquired long QT syndrome (LQTS); this tracing represents torsades de pointes (TdP) TdP is a form of polymorphic ventricular tachycardia that occurs in the setting of either acquired or congenital LQTS, where it appears as though the QRS is twisting around an isoelectric axis Delay in treatment can cause the rhythm to degenerate into ventricular fibrillation The first-line treatment for TdP is IV magnesium, which is effective in both treatment and prevention of TdP It is effective even in the setting of a normal serum magnesium level Of the antiarrhythmics presented, lidocaine would be the most appropriate choice in the acute management of TdP, as it shortens the duration of the action potential Both amiodarone and procainamide prolong the QT interval, which worsens the pathophysiology of this arrhythmia Adenosine is used primarily to diagnose and treat supraventricular tachycardias It would not treat TdP In the setting of an unstable patient, ventricular defibrillation would be the first-line therapy CHAPTER 136 Board Review Questions Chapter 39: Performance of Cardiopulmonary Resuscitation in Infants and Children A 6-year-old child with a history of asthma is brought to the emergency department by paramedics with cardiopulmonary resuscitation (CPR) in process She developed severe respiratory distress and was intubated during the ambulance ride to the hospital Appropriate position of the endotracheal tube was documented, including exhaled end-tidal carbon dioxide (ETCO2) About minutes prior to her arrival, she became progressively hypoxemic and bradycardic and cardiopulmonary resuscitation (CPR) was started Upon arrival to the resuscitation bay, she is transferred to the stretcher with ongoing CPR, ETCO2 monitoring is confirmed, and a CPR quality recording defibrillator is placed Which of the following is the correct compression-to-ventilation ratio and frequency of chest compressions in this situation? A 15 compressions: ventilations, at least 100 compressions/ minute B 30 compressions: ventilations, no more than 120 compressions/ minute C Continuous chest compressions at a rate of 100 to 120 compressions/minute with 10 breaths per minute (asynchronous ventilation) D 100–120 compressions/minute without ventilations (“handsonly” CPR) Preferred response: C Rationale When a child has an invasive airway in place during CPR, guidelines recommend the provision of continuous chest compressions at a rate of 100 to 120 per minute with asynchronous ventilations To avoid excessive ventilation, ventilations should be provided at a rate of breath every seconds (10 breaths per minute) During ongoing resuscitation of the child above, an arterial line is placed in the femoral artery Transduction during active CPR demonstrates a blood pressure of 75/22 mm Hg Among these markers of CPR quality, which one has been associated with improved survival to hospital discharge with favorable neurological outcome after pediatric cardiac arrest? A Chest compression rate 100–120 per minute B Depth of compression 50 mm C Diastolic blood pressure 25 mm Hg in infants and 30 mm Hg in older children D ETCO2 during CPR 20 mm Hg Preferred response: C Rationale In a recent large registry study of the Collaborative Pediatric Critical Care Research Network (CPCCRN), among children with an arterial line in place at the time of the arrest, a diastolic blood pressure 25 mm Hg in infants and 30 mm Hg in older children was associated with improved survival to discharge and survival to discharge with favorable neurological outcome compared to lower blood pressures e59 Following successful resuscitation from cardiac arrest, which of the following represent an optimal set of goals during the postarrest period? A Blood pressure 5th percentile for age; Paco2 35–50 mm Hg; normal Pao2; avoidance of fever B Core body temperature 32–34°C; Paco2 ,30 mm Hg; blood pressure 5th percentile for age C Core body temperature 35–37°C; Paco2 ,30 mm Hg; blood pressure 5th percentile for age D Serum glucose 60–100 mg/dL; blood pressure 5th percentile for age; normal Paco2 Preferred response: A Rationale Goals for the provision of post cardiac arrest care include: • Avoidance of hypotension (provision of isotonic fluids, vasopressors, and inotropic agents to maintain blood pressure 5th percentile for age) • Avoidance of fever with continuous core body temperature monitoring and targeted temperature management to maintain normothermia Therapeutic hypothermia can be considered following out-of-hospital cardiac arrest (OHCA) • Avoidance of significant hypocapnia/hypercapnia or hypoxemia/ hyperoxia • Monitoring for seizures A 14-year-old girl was found unresponsive and CPR is being provided for pulseless electrical activity cardiac arrest During a pulse and rhythm check, there is no pulse palpable and the monitor and defibrillator display a disorganized rhythm that appears to be ventricular fibrillation (VF) You direct the team to resume chest compressions What is your next step in management? A Amiodarone mg/kg intravenously B Continued CPR according to the PEA algorithm, as this was the original rhythm C Defibrillation for VF of J/kg D Synchronized cardioversion for VF: 0.5–1 J/kg Preferred response: C Rationale Though they encompass a smaller proportion of arrest rhythms relative to adults, ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) occur in children and require vigilance by clinicians to identify and appropriately treat Moreover, a substantial number of children have VF or pVT as a subsequent cardiac arrest rhythm—that is, they initially have a nonshockable rhythm for which CPR is initiated and then develop VF/pVT Therefore constant reassessment during resuscitation is paramount In addition to ongoing high-quality CPR, the first-line treatment of VF or pVT is defibrillation, following which CPR should be immediately resumed If two defibrillation attempts are unsuccessful, amiodarone or lidocaine should be administered, in addition to ongoing defibrillation attempts and CPR Minimization of peri-defibrillation interruptions in chest compressions has been associated with improved outcomes e60 S E C T I O N XV Pediatric Critical Care: Board Review Questions A healthy 12-year-old is playing baseball and is hit in the center of the chest by a pitch He suddenly collapses and loses consciousness, unresponsive to stimulation, with an occasional gasp (agonal) breath When paramedics arrive, the first ECG rhythm they are likely to see, is: A Asystole B Pulseless electrical activity C Sinus bradycardia D Ventricular fibrillation Preferred response: D Rationale Following a sharp blow to the chest with sudden collapse, called “commotion cordis,” the most common cause of arrest is an R on T phenomena leading to ventricular fibrillation If an AED (automated external defibrillator) had been applied prior to EMS arrival, a shock would have been advised A 12-year-old with severe asthma has respiratory distress unresponsive to albuterol aerosols and oxygen The child becomes confused, then unconscious and unresponsive The Spo2 was 90%, then 70% and now is not picking up There is no pulse palpable and the arterial catheter tracing is flat (nonpulsatile) on the monitor The child has an occasional gasp (agonal) breath The ECG rhythm on the monitor is most likely: A Pulseless electrical activity B Sinus bradycardia C Ventricular fibrillation D Ventricular tachycardia Preferred response: A Rationale This child has progressive respiratory failure due to lower airway obstruction (asthma) with severe arterial desaturation, and has progressed to a pulseless rhythm, with evidence of no perfusion and no pulse (by palpation or arterial line) This is most likely pulseless electrical activity One should review the H’s and T’s for potential causes of PEA, with high suspicion for pneumothorax in a severe asthmatic During cardiopulmonary resuscitation (CPR), which of the following bedside monitoring tools is most predictive of return of spontaneous circulation (ROSC)? A Exhaled CO2 capnograph of 15 Torr B Femoral pulse palpable with chest compressions C Pacer spikes visible on electrocardiogram when transcutaneous pacing is initiated D Pulse oximeter waveform detected with chest compressions Preferred response: A Rationale During the low-flow phase of CPR, achieving optimal cardiac output/coronary perfusion pressure is consistently associated with an improved chance of return of spontaneous circulation Bedside capnography can be useful as a rough estimate of pulmonary blood flow Achieving an optimal exhaled carbon dioxide concentration 15 Torr has been associated with improved short-term outcome in both animal and human studies 8 A previously healthy 7-year-old boy under evaluation for syncope suddenly collapses His cardiac arrest rhythm looks like ventricular fibrillation (VF) on the monitor If high-quality standard CPR was provided (with chest compressions and 100% fraction of inspired oxygen rescue breathing), an arterial blood gas (ABG) and venous blood gas (VBG) drawn just prior to defibrillation would most likely show: A ABG: pH 7.10, Pco2 65, Po2 300 VBG: pH 7.35, Pco2 65, Po2 40 B ABG: pH 7.10, Pco2 55, Po2 50 VBG: pH 7.10, Pco2 55, Po2 50 C ABG: pH 7.05, Pco2 25, Po2 20 VBG: pH 7.25, Pco2 55, Po2 35 D ABG: pH 7.30, Pco2 30, Po2 300 VBG: pH 7.10, Pco2 75, Po2 30 Preferred response: D Rationale Provision of high-quality CPR (i.e., push hard, push fast but not too fast, allow full chest recoil, minimize interruptions, and don’t overventilate) can result in cardiac output that approaches 50% of normal The other choices have either inappropriately low Po2 levels given this scenario or a venous pH that is higher than the one recorded from the corresponding ABG Chapter 40: Structure and Development of the Upper Respiratory System A child with 22q11 deletion syndrome and congenital heart disease presents with a difficult intubation due to a laryngeal web Which abnormality in the normal larynx embryogenesis caused this to occur? A Atresia as the most common result of failure to recanalize B Cartilages and muscles derived from third and fourth branchial arches C Derivation of epithelium from mesoderm of the laryngotracheal tube D Formation of epiglottis by mesenchyme proliferation of the fourth and sixth branchial arches E Temporary occlusion of larynx until the 10th week when recanalization occurs Preferred response: E Rationale As epithelium proliferates rapidly, the temporary occlusion of the larynx ends by the 10th week when recanalization occurs Atresia is the least common result of failure to recanalize Laryngeal webs and/ or stenosis may be common results of failure to recanalize Branchial arches involved in embryogenesis of the larynx are as follows: cartilages and muscles are derived from the fourth and sixth branchial arches, whereas the third and fourth branchial arches form the epiglottis by mesenchyme proliferation Derivation of epithelium is from endoderm of the laryngotracheal tube, not mesoderm ... [AI002] aVL • Fig 136.15 Rationale Due to her medication profile, this patient is at risk for acquired long QT syndrome (LQTS); this tracing represents torsades de pointes (TdP) TdP is a form of... the normal larynx embryogenesis caused this to occur? A Atresia as the most common result of failure to recanalize B Cartilages and muscles derived from third and fourth branchial arches C Derivation... be enhanced using an a-adrenergic agonist or arginine vasopressin receptor agonist (V1 receptor) This action produces selective vasoconstriction of noncerebral peripheral vessels to areas of the