e41CHAPTER 136 Board Review Questions (i e , tricuspid or mitral atresia), double inlet, or common inlet; and ambiguous (i e , two ventricles with atrial isomerism) When the morphologic right atrium c[.]
CHAPTER 136 Board Review Questions (i.e., tricuspid or mitral atresia), double inlet, or common inlet; and ambiguous (i.e., two ventricles with atrial isomerism) When the morphologic right atrium connects normally to the morphologic right ventricle and the left atrium connects to the left ventricle, AV concordance is present When this connection is reversed and the morphologic right atrium connects to the morphologic left ventricle, AV connection is discordant and sometimes is referred to as ventricular inversion Ventriculoarterial connection is the manner in which the great arteries and semilunar valves connect to the ventricular outflow tracts Normally, the morphologic right ventricle connects to the pulmonary valve and the morphologic left ventricle connects to the aortic valve Four possibilities exist: concordant (i.e., normal), discordant (i.e., right ventricle to the aorta and left ventricle to the pulmonary trunk), double outlet (usually the right ventricle), and single outlet (i.e., aortic or pulmonary atresia or truncus arteriosus) Ventricular function can be assessed by the shortening fraction Shortening fraction is calculated by which of the following equations? A End-diastolic dimension minus end-systolic dimension divided by end-diastolic dimension B End-diastolic dimension minus end-systolic dimension divided by end-systolic dimension C End-systolic dimension minus end-diastolic dimension divided by end-systolic dimension D End-systolic dimension minus end-diastolic dimension divided by end-diastolic dimension Preferred response: A Rationale Echocardiography is a tomographic anatomic tool, but it also provides dynamic information about cardiac function and structure Observations about the cardiac walls, including their movement, thickness, and degrees of shortening and thickening, can be extremely useful in determining segmental and global cardiac function In general, the shortening fraction of the left ventricle should be at least 28% (end-diastolic minus end-systolic divided by end-diastolic dimension), and the walls of the left ventricle should move inward symmetrically In congenital heart disease, the major application of contrast echocardiography in the postoperative patient is which of the following? A Assessment of ventricular function B Assessment of coronary arterial flow C Detection of residual shunt lesion D Evaluation of mitral regurgitation Preferred response: C Rationale An ultrasonic contrast agent is a substance that stabilizes microbubbles in solution, which are large enough to reflect ultrasound but small enough that they disappear rapidly and are physiologically safe The agent may be as simple as an injection of saline solution into the circulation during two-dimensional echocardiographic imaging or as complex as precision-engineered microbubbles of polysaccharide that dissolve in the circulation after injection Advances in bubble technology allow imaging of myocardial capillary perfusion Contrast also can be useful in defining the identity of an imaged structure For example, a structure under the aortic arch e41 may be confusing but can be confirmed to be the innominate vein by echocardiographic contrast injection in a left arm vein In persons with congenital heart disease, the major application of contrast echocardiography is in the postoperative patient with residual shunts or as a means to exclude congenital heart disease Systemic venous injection of contrast fills the right side of the heart sequentially, and the site of residual right-to-left shunting can be defined The Ross procedure involves which of the following? A Autologous autograft in the pulmonary position and mechanical prosthesis in the aortic position B Autologous autograft in the aortic position and mechanical prosthesis in the pulmonary position C Mechanical valve in the pulmonary position and autograft in the aortic position D Placement of a pulmonary autograft in the aortic position Preferred response: D Rationale The Ross procedure involves the substitution of the diseased aortic valve with the patient’s own pulmonary valve (autograft) A pulmonary homograft is then used to replace the patient’s pulmonary valve The coronary arteries are translocated to the new aortic valve Advantages of this procedure include the lack of need for anticoagulation because of the decreased incidence of thromboembolism, as well as growth of the valve as the child grows One disadvantage is the treatment of one-valve disease with a two-valve replacement Chapter 30: Diagnostic and Therapeutic Cardiac Catheterization A 2-week-old full term female with hypoplastic left heart syndrome has delayed convalescence following Norwood procedure with modified Blalock-Taussig shunt and is referred for cardiac catheterization The patient has baseline hemoglobin of 14 mg/ dL and estimated oxygen consumption of 160 mL/minute/m2 The following saturations were obtained while intubated at a fraction of inspired oxygen of 21%: descending aorta, 88%; left upper pulmonary vein, 98%; mixed venous saturation obtained in the superior vena cava, 61% What is the patient’s estimated ratio of pulmonary to systemic blood flow (Qp:Qs)? A 0.4 B 0.7 C D 2.7 E Cannot calculate with the given data Preferred response: D Rationale The Fick method uses a patient’s oxygen consumption and oxygen carrying capacity across a vascular bed to calculate blood In patients with single ventricle physiology, the systemic and pulmonary saturations are identical For this reason, only three saturations are required for calculating Qp:Qs via the Fick method As per equations in Table 30.1, the equation to calculate Qp:Qs can be simplified to include only saturations as many of the terms cancel out through division For this question, Qp:Qs is calculated as: (systemic saturation – mixed venous saturation) (pulmonary venous saturation – pulmonary artery saturation) Since the systemic and pulmonary arterial saturations are equivalent, (88 61) (98 88) 2.7 Note that a saturation of 88% in a e42 S E C T I O N XV Pediatric Critical Care: Board Review Questions patient with hypoplastic left heart syndrome after stage I palliation suggests significantly increased Qp:Qs as is demonstrated here A 12-year-old male with no prior history of cardiac disease is admitted to the pediatric intensive care unit with concerns for shock He has a history of febrile illness with malaise several weeks prior The patient is tachycardic and tachypneic with a pale appearance The first Korotkoff sound is heard intermittently with respiration at a systolic blood pressure of 85 mm Hg and consistently at 72 mm Hg On exam, the patient has weak pulses throughout, jugular venous distension, and distant heart sounds The electrocardiogram demonstrates sinus tachycardia with beat-to-beat variation in the QRS amplitude An echocardiogram shows a large pericardial effusion with respiratory variation in mitral inflow by pulse wave Doppler of 20% Given concern for tamponade, the patient is prepared for a pericardiocentesis For this patient, select the finding that is NOT representative of tamponade physiology: A Hypotension B Jugular venous distension C Large pericardial effusion D Pulsus paradoxus E All of the above are required for tamponade physiology Preferred response: C Rationale If the pericardial effusion accumulates slowly, patients can remain hemodynamically stable and potentially asymptomatic even with a large pericardial effusion Tamponade is a clinical diagnosis that is characterized by Beck’s triad: distant heart sounds, hypotension, and jugular venous distension Patients with tamponade also have tachycardia, tachypnea, narrow pulse pressures, and pulsus paradoxus The ECG and echocardiogram changes may be suggestive of a diagnosis, but must be accompanied by the clinical signs and symptoms to meet a diagnosis A 2-year-old admitted with tachypnea is referred for catheterization after an echocardiogram demonstrated right heart enlargement and partial anomalous pulmonary venous return The patient’s baseline hemoglobin is 12.5 mg/dL The patient is sedated and intubated with fraction of inspired oxygen of 21% Estimated oxygen consumption (Vo2) is 150 mL/min/ m2 and the following saturations are obtained: Innominate Vein High Right Pulmonary Pulmonary Descending SVC Atrium Artery Vein Aorta 71% 70% 85% 86% 99% 99% Calculate the pulmonary blood flow for this patient A 2.5 L/min/m2 B 4.1 L/min/m2 C 6.8 L/min/m2 D 10 L/min/m2 E Unable to calculate with the given information Preferred response: C Rationale As per Table 30.1, pulmonary blood flow can be calculated as Vo2/10 [1.36 Hgb (pulmonary vein saturation – pulmonary artery saturation)] For the question, 150 / [10 1.36 12.5 (0.9920.86)] 150/(13.6 12.5 0.13) 6.8 L/min/m2 4 A 10-month-old male is admitted for evaluation of persistent desaturations requiring nasal cannula support He has a large ventricular septal defect Despite poor outpatient follow-up, his growth has been normal Infectious work up is unremarkable He is referred for catheterization to more clearly delineate the source of desaturations and evaluate pulmonary vascular resistance prior to surgical referral During the catheterization, the pulmonary venous saturation was 95% and pulmonary vascular resistance was Wood units m2 at fraction of inspired oxygen (Fio2) 0.21 At 1.0 Fio2 and 20 ppm inhaled nitric oxide, the pulmonary vascular resistance decreased to Wood units m2 Per AHA guidelines, what would be the most appropriate step in cardiac management? A Initiate pulmonary vasodilator therapy with sildenafil and repeat catheterization prior to surgical repair B Initiate pulmonary vasodilator therapy for symptom management; however, he is not a surgical candidate due to pulmonary hypertension C Manage with diuretics as pulmonary vasodilator therapy is contraindicated D Refer for surgery, consider fenestrated patch repair and anticipate need for postoperative pulmonary hypertension therapy Preferred response: D Rationale Per recent AHA guidelines by Abman et al entitled Pediatric Pulmonary Hypertension, patients younger than year of age with simple shunting lesions and concern for increased pulmonary vascular resistance should undergo catheterization with acute vasodilator testing For patients with indexed pulmonary vascular resistance greater than Wood units m2, vasodilator testing is recommended If the pulmonary vascular resistance improves with testing, then it would be reasonable to refer the patient for surgical repair A 6-month-old infant is days into the postoperative period after tetralogy of Fallot repair There are persisting signs of right heart failure with hepatomegaly and ascites An echocardiogram has inadequate windows to visualize the branch pulmonary arteries What is the most appropriate management? A Communicate to the cardiac surgeon and interventional cardiologist and advocate for a diagnostic catheterization and possible pulmonary artery intervention if significant residual stenotic lesions are diagnosed B Communicate to the cardiac surgeon and interventional cardiologist and advocate for a diagnostic catheterization and possible ASD closure C Continue to medically manage with the goal of spontaneous right heart recovery D Transfer the infant to the catheterization laboratory for pulmonary artery angiography Preferred response: A Rationale Communication is essential The cardiac surgeon on a recent surgical patient will know the child’s anatomy intimately and also have an awareness of possible problems The interventional cardiologist can advise on what is technically feasible As the ICU attending, involving all providers is crucial for maximizing outcomes Arranging a catheterization without consultation will result in a poorly planned and inefficient catheterization that may lead to unnecessary angiograms and worse outcomes Right heart failure CHAPTER 136 Board Review Questions can spontaneously improve early after cardiac repair, but if recovery is prolonged 72 hours longer than anticipated, then strong consideration for residual cardiac defects is very important There are now reports on safe early postoperative interventions, thus a catheterization for merely diagnostic purposes would be incorrect Closing an ASD in the setting of right heart failure would worsen cardiac output and elevate central venous pressure In fact if there is an intact atrial septum, one of the interventions to consider is creating an ASD When should cardiac surgical patients requiring venoarterial (VA) extracorporeal membrane oxygenation (ECMO) in the postoperative period be considered for cardiac catheterization? A If there is left ventricle (LV) dysfunction, left atrial (LA) dilation, and pulmonary edema on chest radiograph B Never; cardiac catheterization due to risks of the procedure and transportation is contraindicated when cannulated for VA ECMO C Only as a last resort and should not be considered unless unable to be decannulated after weeks D Should not be considered unless unable to be decannulated after week Preferred response: A Rationale Left atrial decompression can be safely achieved in the catheterization laboratory and is important in the setting of LV dysfunction with distention Decompression of the LA with interventional techniques (placing a cannula in the LA, creating an ASD) alleviates this problem The other option is placement of a LA cannula by cardiac surgery, and this may be preferable in a small child with an open chest Safe transport is challenging but should not be the deciding factor Catheterization on VA ECMO requires a high degree of teamwork, particularly with transport to ensure that cannula position remains stable Safe transportation is a reality in many centers Procedural risks even with anticoagulation are minimal It is important to have a high index of suspicion for residual lesions in postoperative cardiac surgery patients who cannot be weaned from ECMO Unless there is clear evidence for myocardial recovery, consideration for catheterization by the ICU attending and direct consultation with cardiac surgery and interventional cardiology should occur early and within 72 hours of the start of the unexpected course Interventions can be performed on VA ECMO and would be indicated if any residual lesions are diagnosed For an early postoperative patient who has persistent low cardiac output and is unable to be weaned from the ventilator, cardiac catheterization is characterized by which of the following? A Carries a significantly increased risk of serious adverse events when compared with late postoperative catheterization B May yield important physiologic and anatomic information that often leads to reintervention C Should only be performed on a patient supported with extracorporeal membrane oxygenation (ECMO) D Should be deferred until weeks following surgery Preferred response: B Rationale Cardiac catheterization should always be considered in the early postoperative period when a patient exhibits a persistent low output e43 state or failure to wean from mechanical ventilation Early postoperative catheterization often yields important physiologic and anatomic information and frequently leads to reintervention Whereas elective catheter-based interventions are typically deferred until weeks following surgery, the risk-benefit ratio favors early postoperative catheterization for the patient who does not follow a projected course ECMO is used in postoperative patients who fail to separate from bypass or have progressive low output These patients often require early postoperative catheterization to assess unfavorable physiology In addition, ECMO support is often used to safely support the circulation in patients for whom a high-risk catheter intervention is planned In the hands of an experienced team (i.e., interventional cardiologist, intensivist, anesthesia personnel, and nursing staff), serious adverse event rates are similar for early or late postoperative studies A balloon atrial septostomy in the preoperative patient with d-TGA is characterized by which of the following? A Increases left atrial hypertension B May increase the risk for pulmonary hypertension prior to cardiac surgery C May be performed under fluoroscopic or echocardiographic guidance D Worsens cyanosis by facilitating mixing at the atrial level Preferred response: C Rationale Balloon atrial septostomy should be considered in any newborn with a confirmed diagnosis of d-TGA who demonstrates inadequate mixing at the atrial level Signs of inadequate mixing include cyanosis, left atrial hypertension, and pulmonary hypertension Balloon atrial septostomy improves cyanosis by facilitating mixing at the atrial level, reduces left atrial hypertension, and may reduce the risk for pulmonary hypertension prior to cardiac surgery Balloon atrial septostomy may be performed in the catheterization laboratory (under fluoroscopic guidance) or in the intensive care unit (under echocardiographic guidance) at the discretion of the intensivist and cardiac interventionist Chapter 31: Pharmacology of the Cardiovascular System A 4-month-old, kg male with Trisomy 21, complete atrioventricular septal defect (AVSD), congestive heart failure, and failure to thrive is admitted to the pediatric intensive care unit (PICU) following surgical repair The intraoperative course was complicated by a brief cardiopulmonary arrest, attributed to a pulmonary hypertensive crisis on separation from cardiopulmonary bypass Spontaneous circulation was restored following minutes of cardiopulmonary resuscitation Milrinone was administered in divided doses of 25 mg, each over 20 minutes, and infusions of epinephrine, 0.1 mg/kg/min, and milrinone, 0.5 mg/kg/min, were initiated Nitric oxide at 10 ppm was added, and the patient was transferred to the PICU for further management Vital signs on arrival are remarkable for a heart rate of 156 beats per minute and arterial blood pressure of 70/28 mm Hg Oxygen saturation is 100% on Fio2 1.0 and full ventilator support The central venous pressure is mm Hg On physical examination the infant is intubated, sedated, and medically paralyzed His skin is warm and pink, with e44 S E C T I O N XV Pediatric Critical Care: Board Review Questions pulses 11 to 21 in all extremities and capillary refill time of seconds A soft diastolic rumble is present on cardiac auscultation The lungs are clear The liver edge is palpable cm below the right costal margin Pupils are mm and sluggishly reactive to light bilaterally The neurologic exam is otherwise obscured by neuromuscular blockade The postoperative chest radiograph shows a well-positioned endotracheal tube and internal jugular vascular catheter, mild cardiomegaly and clear, well inflated lungs Laboratory data reveal pH 7.38; Paco2, 36 mm Hg; Pao2, 223 mm Hg; HCO3, 22 mmol/L, base excess, 23 mmol/L; ionized calcium, 1.6 mmol/L (reference range 1.2–1.3 mmol/L); lactate, 1.9 mmol/L (reference range ,2 mmol/L); creatinine 1.6 mg/dL (reference range 0.2–0.6 mg/dL); hemoglobin 12 g/dL (reference range 9.0–13 g/dL) Ninety minutes later, the patient’s arterial blood pressure is 50/20 mm Hg, the heart rate is 182 per minute, and there has been only 1.5 mL of concentrated urine output from the urinary catheter since PICU admission The bedside monitor shows sinus tachycardia and the physical exam is otherwise unchanged After re-zeroing the arterial catheter system, the repeat blood pressure is the same The most appropriate initial intervention is to: A Confirm the blood pressure via sphygmomanometer B Consult Cardiology for recommendations C Increase the epinephrine infusion to mg/kg/min D Infuse 40 mL Ringer’s lactate over minutes E Start a vasopressin infusion 0.0008 U/kg/min Preferred response: D Rationale An infusion of 10 mL/kg of isotonic fluid should be initiated and the response closely monitored The observation that the patient’s perfusion appeared unchanged is due to exaggerated peripheral vasodilation that can occur with milrinone, along with a generalized sunburned appearance This can be mistaken for adequate perfusion if consideration is not given to milrinone as the culprit Although following blood pressure cuff readings may be helpful in certain scenarios, there is no reason to discount the invasive arterial blood pressure reading once the system has been interrogated and no problems have been identified Increasing the epinephrine dose to mg/kg/minute would be very poorly tolerated in this scenario The patient is already tachycardic, and the risk of dysrhythmias is a known complication following repair of complete AVSD In addition, the increased afterload to the left ventricle following closure of the ventricular septal defect and correction of mitral insufficiency would only be compounded by the increase in systemic vascular resistance (SVR) from this dose of epinephrine For the same reason, adding a vasopressin infusion would not be the best choice Although the oliguria in this scenario is likely due to a decrease in SVR, the resulting “relative” hypovolemia indicates that gentle fluid repletion should be initiated to optimize organ perfusion prior to increasing vascular tone with a vasoconstrictor While alerting the cardiologists to the change in the patient’s status is an important priority, waiting for their input will delay treatment of a problem that requires immediate attention The effects of cardiopulmonary bypass and the associated inflammatory response, plus the impact of intraoperative events, combined with the major change in circulatory physiology and potential for adverse medication effects must all be considered and quickly addressed in order to ensure optimal outcomes The most likely reason for the hypotension is: A Anaphylaxis from perioperative, prophylactic cefazolin B Cumulative effect of the milrinone loading dose and infusion C Equipment error D Septic shock due to a urinary tract infection Preferred response: B Rationale This patient’s presentation on admission to the PICU with widened pulse pressure with mild diastolic hypotension and prolonged capillary refill time despite the appearance of adequate perfusion is consistent with the peripheral vasodilation that can be seen in some patients on milrinone infusions, especially following a full loading dose The response may be exaggerated in patients with mild acute kidney injury (such as this one) due to delayed drug clearance and those who are relatively volume depleted as was this patient In the scenario presented here, renal hypoperfusion during cardiopulmonary bypass compounded by the brief cardiopulmonary arrest led to renal insufficiency Approximately 85% of milrinone is cleared by the kidney This property of the drug, along with its relatively long elimination half-life may result in accumulation of the medication, the consequences of which may persist for several hours The need for dose adjustment should be evaluated for all medications whose effects may be intensified or prolonged by delayed renal clearance (e.g., certain sedatives and neuromuscular blocking agents) Once the child’s hemodynamic status improves, which of the following is most likely to prevent recurrence of the hypotension? A Decreasing the epinephrine to 0.05 mg/kg/min B Decreasing the milrinone to 0.25 mg/kg/min C Increasing the intravenous fluids to twice maintenance D Increasing the nitric oxide to 20 ppm E Increasing the dose of neuromuscular blocking agent Preferred response: B Rationale Continuing the milrinone infusion is the best action, albeit at a lower rate, due to the patient’s history of congestive heart failure and pulmonary hypertension, along with the change in loading conditions following closure of the ventricular septum and recent cardiopulmonary arrest In addition, there is evidence for improved outcomes in infants with postoperative cardiac dysfunction with administration of milrinone in the early postoperative period Increasing the intravenous fluids to twice maintenance in this patient with kidney injury will likely little to prevent the hypotension and instead worsen postoperative anasarca, while also increasing the workload on the heart Likewise, increasing the nitric oxide, decreasing the epinephrine infusion rate, or increasing the neuromuscular blockade will not prevent recurrence of the hypotension Following initial fluid administration and stabilization of hemodynamics, gentle up-titration of the epinephrine infusion may then be indicated to achieve optimal perfusion and to limit the number of fluid boluses CHAPTER 136 Board Review Questions A 4-month-old male with Down syndrome is admitted to the PICU for postoperative care following patch repair of a large ventricular septal defect (VSD) He was managed preoperatively for congestive heart failure with furosemide and enalapril His vital signs on admission to the PICU are significant for a temperature of 38.2°C; heart rate, 170 beats per minute; blood pressure, 86/38 mm Hg via a right radial arterial catheter (mean arterial pressure, 54 mm Hg); and oxygen saturation of 89% by pulse oximetry (with a probe on his great toe) On exam, his extremities are mottled and cool distally, with a capillary refill of 2.5 seconds A bedside arterial blood gas suggests adequate oxygenation and ventilation The arterial lactate is mmol/L You observe only a marginal change in his perfusion after three fluid boluses of 10 mL/kg The central venous pressure is now 14 mm Hg What is the most appropriate next step in his management? A Administer an intravenous (IV) milrinone bolus of 50 µg/ kg over 15 minutes followed by a continuous infusion of milrinone at 0.5 µg/kg/minute B Continue to bolus with fluids, but change to albumin for more effective intravascular volume repletion C Start epinephrine at 0.5 µg/kg/minute, titrating to achieve a goal mean arterial pressure of 65 mm Hg D Start dopamine at 15 µg/kg/minute, and overdrive pace to ensure atrioventricular synchrony Preferred response: A Rationale This patient is exhibiting signs of postoperative, decompensated cardiogenic shock, with tachycardia, cool and mottled extremities, prolonged capillary refill, and an elevated lactate, all of which indicate inadequate cardiac output The decreased saturation via pulse oximetry, while the arterial blood gas demonstrates adequate oxygenation, is a function of distal vasoconstriction, which impacts the ability of the pulse oximeter probe to provide an accurate reading Fluid resuscitation was attempted to augment preload to optimize this patient’s ventricular filling (to take advantage of the Starling relationship), but it did not restore perfusion because there is significant myocardial dysfunction Therefore the best intervention is to start milrinone, which provides both inotropy and afterload reduction, without significantly increasing myocardial oxygen demand If a patient’s blood pressure and hemodynamics allow, a loading dose is given before initiating the infusion A catecholamine such as epinephrine, as a sole agent and initiated at the dose provided in the scenario, would not be the best option for several reasons First, the patient is already tachycardic, and epinephrine at 0.5 µg/kg/minute may increase the heart rate further and increase myocardial oxygen demand in a heart whose function is already impaired Escalating this patient’s heart rate would also decrease the diastolic interval for ventricular filling, thus compromising cardiac output even further In addition, patients who undergo repair of large ventricular septal defects are at increased risk for developing junctional ectopic tachycardia (JET), a tachyarrhythmia unique to the postoperative state in children, in which the loss of atrioventricular synchrony compromises cardiac output Patients in whom this rhythm is poorly tolerated may require treatment with antiarrhythmics and active cooling if conservative measures such as avoiding fever and minimizing catecholamine-induced increases in adrenergic tone fail Response B would not be the most appropriate next step because the central venous pressure is already elevated due to ventricular dysfunction, and rather than augmenting cardiac output, e45 additional fluid boluses would likely produce pulmonary edema High-dose dopamine would not be the best choice for similar reasons as those stated for epinephrine In addition, at a dose of 15 µg/kg/minute, dopamine exhibits strong a-adrenergic (vasoconstrictive) properties, which would increase afterload and compromise distal perfusion even further The consequences of increasing heart rate with overdrive pacing were detailed earlier Norepinephrine _ the heart rate This action is mediated by Therefore would be an effective agent for reversing this response A Increases, the hypothalamus, isoproterenol B Decreases, a reflex response, atropine C Decreases, a vagal response, isoproterenol D Has no effect on, the sinus node, ventricular pacing Preferred response: B Rationale Norepinephrine exhibits strong a-adrenergic properties at doses used to reverse vasodilatory (hyperdynamic) shock The resulting increase in vascular tone triggers a compensatory vagally mediated reflex slowing of the heart, which atropine will reverse via a muscarinic receptor blockade Neither the hypothalamus nor the sinus node has been implicated You have decided to add an epinephrine infusion to the management of an 11-year-old girl with myocarditis Your goal is to improve cardiac contractility via epinephrine’s effect on b receptors A medical student on call with you asks why epinephrine is more selective for b receptors than norepinephrine How you respond to this question? A Because of an increased number of hydroxyl groups on the phenylethylamine core B Because of a decrease in size of the substituent on the amino group C Because of an increase in size of the substituent on the amino group D Because of a lack of hydroxyl group at position on the phenylethylamine core Preferred response: C Rationale Increasing the size of the substituent on the amino group enhances b selectivity, while decreasing the size favors a selectivity Hydroxyl groups are the same in terms of number and location for all catecholamines Catecholamines and phosphodiesterase III (PDE III) inhibitors share a common mechanism in that both groups of agents which of the following? A Decrease intracellular calcium in the vascular smooth muscle B Decrease the activity of protein kinase A C Increase the activity of adenylate cyclase D Increase the levels of cyclic adenosine monophosphate (cAMP) in the cardiac myocyte Preferred response: D Rationale Catecholamines vary in terms of their effect on intracellular calcium in the vascular smooth muscle PDE III inhibitors increase activity of adenylate cyclase Both groups of drugs increase levels of the second messenger, cAMP ... (placing a cannula in the LA, creating an ASD) alleviates this problem The other option is placement of a LA cannula by cardiac surgery, and this may be preferable in a small child with an open chest... vascular resistance (SVR) from this dose of epinephrine For the same reason, adding a vasopressin infusion would not be the best choice Although the oliguria in this scenario is likely due to... in patients with mild acute kidney injury (such as this one) due to delayed drug clearance and those who are relatively volume depleted as was this patient In the scenario presented here, renal