e121CHAPTER 136 Board Review Questions and/or colloid If possible, avoid vasopressors given the risk of renal vasoconstriction An adult kidney in a small child needs a normal to high blood pressure an[.]
CHAPTER 136 Board Review Questions and/or colloid If possible, avoid vasopressors given the risk of renal vasoconstriction An adult kidney in a small child needs a normal to high blood pressure and good intravascular volume for adequate perfusion If the child has one or both of the native kidneys, be alert to hypotension and dehydration from polyuria Chapter 77: Renal Pharmacology A 4-year-old female with a history of acute lymphocytic leukemia (ALL) is admitted to the pediatric intensive care unit with neutropenic fever and concern for sepsis She has not had any urine output since admission (,12 hours) and her serum creatinine increased to 0.5 mg/dL from a baseline of 0.3 mg/dL She is placed on broad coverage antibiotics with ceftazidime, vancomycin, and gentamicin The recommended intravenous (IV) gentamicin dose for a 4-year-old with normal renal function is 2.5 mg/kg What is the best approach to dosing and monitoring her gentamicin therapy? A Prescribe the recommended 2.5 mg/kg dose for one dose and obtain a trough drug level prior to giving another dose to ensure the patient is clearing B Prescribe the recommended 2.5 mg/kg dose and frequency and obtain drug levels only if the gentamicin is continued for greater than 48 hours C Prescribe mg/kg IV every hours and obtain drug levels around the third dose D Prescribe 2.5 mg/kg IV daily and not obtain drug levels unless continued past 48 hours Preferred response: A e121 Which of the following is a strategy to overcome diuretic resistance? A Fluid restriction B Combination diuretic therapy C Diuretic monotherapy with a loop diuretic D Intermittent low-dose diuretic regimen Preferred response: B Rationale Sodium reabsorption in the kidney is sequential and many of the adaptive processes increase sodium reabsorption distal to the site of diuretic action Combination therapy including loop diuretics and diuretics that work on the distal tubule may be effective Part of the effectiveness of combination diuretic therapy resides in the longer duration of effect for thiazides that prevents the postdiuretic sodium reabsorption noted with the shorter-acting loop diuretics In patients with edema a greater amount of drug may be needed in the renal tubule to produce the desired diuretic response An intermittent high-dose diuretic regimen may overcome the impaired rate of tubular secretion and increase the urinary diuretic concentration sufficient to elicit a response Which of the following diuretic categories is considered the most effective in producing diuresis? A Carbonic anhydrase inhibitors B Loop diuretics C Potassium-sparing diuretics D Thiazide diuretics Preferred response: B Rationale Rationale Due to the dynamic aspect of acute renal failure, this patient’s renal function cannot be accurately measured; thus, scheduling a dosing regimen could put her at risk for underdosing or toxicity Considering gentamicin is a concentration-dependent antibiotic, the dosing strategy should be to keep the same dose but to increase the interval as needed It is therefore best to obtain a drug level following one dose to ensure it is safe before giving another dose and this will help determine the appropriate dosing interval Loop diuretics (e.g., furosemide, bumetanide, torsemide) are antagonists of the Na1/K12Cl2 cotransported in the ascending loop of Henle Inhibition of the transporter increases the sodium, and thus water, content of the filtrate and also diminishes the medullary osmotic potential Both of these increase the excretion of sodium and water 2 Which of the following alter medication dosing in chronic renal failure? A Decrease in albumin leading to increase free drug B Decrease in volume of distribution C Increased absorption through gastric mucosa D Stable glomerular filtration Preferred response: A Rationale Patients with chronic renal failure have decreased serum albumin levels, leading to a significant increase in free drug for highly protein bound medications Glomerular filtration rate is decreased in chronic renal failure and plays the most direct role in affecting medication dosing Studies have also shown that patients with chronic renal failure have altered gastric mucosa leading to decreased, not increased, absorption of enterally administered medications Volume of distribution is not directly affected by chronic renal failure 5 A 16-year-old girl who received a deceased donor renal transplant develops delayed graft function and has an estimated glomerular filtration rate (GFR) of 35 mL/min/1.73m2 In addition to her immunosuppressive medications, she is prescribed ganciclovir for cytomegalovirus (CMV) prophylaxis Which of the following factors is most important in determining the correct ganciclovir dosage? A The donor CMV status B The extent of her fluid overload C The extent of her reduced kidney function D The need for diuretics Preferred response: C Rationale The elimination of ganciclovir from the body is directly related to kidney function, as ganciclovir is predominantly eliminated by glomerular filtration Failure to adjust the dose in the presence of decreased kidney function will lead to an accumulation of ganciclovir and possible toxicity Although fluid overload and her albumin concentration may impact the volume of distribution, it is unlikely to impact a dosage adjustment The donor CMV status and need for concurrent diuretics will not impact ganciclovir dosing e122 S E C T I O N XV Pediatric Critical Care: Board Review Questions Chapter 78: Hypertensive Urgencies and Emergencies A 9-year-old girl with end-stage kidney disease treated with chronic hemodialysis times per week presents for her scheduled dialysis treatment Her initial blood pressure is 210/140 mm Hg in the right arm and 195/150 mm Hg in the left arm You are called to help assess the patient because the nephrologists are all out of the hospital On examination, she is crying and irritable but consolable She has periorbital edema and crackles on lung exam; her weight is noted to be kg above her postdialysis weight days ago Which of the following is the best treatment regimen for this patient? A Give a dose of oral hydralazine and begin her usual dialysis treatment B Give a dose of intravenous labetalol, transfer to the ICU, and then begin dialysis C Give a dose of intravenous hydralazine, transfer to the ICU, and then begin dialysis D Give a dose of oral isradipine, transfer to the ICU, and then begin dialysis Preferred response: B of symptomatic tachycardia Amlodipine, a calcium channel blocker, might lower the blood pressure but would not prepare the patient appropriately for surgery A 16-year-old boy is transported to the PICU from an outlying hospital where he had presented with status epilepticus and severe hypertension, with blood pressure (BP) readings ranging from 175–200/110–120 mm Hg His seizures were controlled with lorazepam prior to transport, but his BPs remain elevated upon admission to the PICU No family members are yet available to provide history His examination is notable for marked periorbital edema and rales at the lung bases bilaterally Laboratory studies from the outside hospital reveal hematuria, proteinuria, and an elevated serum creatinine of 2.1 mg/dL Which of the following antihypertensive agents would be most appropriate to administer in this setting? A Intravenous enalaprilat B Intravenous furosemide C Intravenous nicardipine D Intravenous sodium nitroprusside Preferred response: C Rationale The child has hypertension from volume overload and requires dialysis Since the nephrologists are unavailable, the child should be moved to a location where she can be observed by trained personnel who can respond appropriately if her condition deteriorates While labetalol, hydralazine, and isradipine all produce vasodilation which can impair the ability to remove fluid on dialysis, intravenous labetalol has the shortest duration of action and should therefore allow the desired fluid removal Oral administration may take too long to reduce the blood pressure, so an IV agent is preferred Rationale The child has a hypertensive emergency, and immediate BP reduction with an intravenous agent is indicated Glomerulonephritis is the likely cause of his acute severe hypertension as evidenced by the peripheral edema, pulmonary edema, and laboratory findings Given the renal dysfunction, enalaprilat and nitroprusside would be contraindicated Furosemide might eventually be administered to address volume overload, but it would not be appropriate as the first agent Thus nicardipine is the best agent of the available choices 2 A 12-year-old girl was admitted to the PICU with acute severe hypertension Initial blood pressure control was achieved with intravenous nicardipine Imaging showed a mass superior to the right kidney and serum catecholamines and metanephrines were significantly elevated She is now ready for transition to oral antihypertensive therapy Which of the following agents is the best choice? A Amlodipine B Doxazosin C Labetalol D Metoprolol Preferred response: B A 3-year-old girl is admitted to the PICU from the emergency department (ED), where her parents had brought her for evaluation of headache and persistent vomiting Vital signs in the ED were notable for a heart rate of 140 beats per minute and blood pressure (BP) readings of 135–142/87–92 mm Hg; BP measurements were similar in the upper and lower extremities She had a protuberant abdomen on physical examination that was diffusely tender to palpation without rebound tenderness There was a right upper quadrant mass immediately below the costal margin that on ultrasound had a complex appearance and seemed to be displacing the right kidney laterally Serum chemistries were normal, but a complete blood cell count (CBC) was remarkable for hemoglobin of 8.5 g/dL Oral isradipine had been administered in the ED but she vomited shortly after the dose BP on admission to the PICU is 144/90 mm Hg What is the best next step in her management? A Give an intravenous bolus dose of labetalol and begin a labetalol infusion; obtain noninvasive BP measurements every to minutes B Insert an arterial line and begin a nicardipine infusion C Place a nasogastric tube and repeat a dose of isradipine; obtain noninvasive BP measurements every to minutes D Place a nasogastric tube and administer a dose of propranolol; obtain noninvasive BP measurements every to minutes Preferred response: A Rationale The patient has a pheochromocytoma Any intravenous antihypertensive agent may be used for initial management of hypertension in such patients Once the diagnosis has been made, however, the goal of therapy is to induce complete alpha-blockade in preparation for surgical removal of the tumor Doxazosin is a peripheral alpha-blocker that has found increasing use as an alternative to the older agent phenoxybenzamine, as it may be less likely to cause severe tachycardia While labetalol has some alphablocking activity, it is primarily a beta-blocker Beta-blockers are not preferred for management of hypertension in pheochromocytoma because they may worsen vasoconstriction and lead to additional episodes of acute severe hypertension After complete blockade has been achieved, beta-blockers may be used for control CHAPTER 136 Board Review Questions Rationale The child is exhibiting signs of hypertensive urgency as manifested by the headache and vomiting She is at risk of progressing to more severe neurologic manifestations of her severe hypertension and requires prompt BP reduction to prevent this from occurring The cause of her severe hypertension is likely a neuroblastoma, which causes severe hypertension by producing catecholamines; increased renin secretion due to the renal displacement may also be playing a role Oral medications should not be given because of the persistent vomiting and because the magnitude of BP reduction is unpredictable Labetalol provides a blockade of a and b receptors and is a better choice of agent than nicardipine in this case; however, if labetalol were unavailable, nicardipine would be an acceptable choice A bolus dose of labetalol will reduce the BP promptly, allowing time for the pharmacy to prepare an infusion Noninvasive monitoring of BP is acceptable until such time as an arterial line can be placed A 5-year-old child with a blood pressure of 180/110 mm Hg is admitted to the pediatric intensive care unit for initiation of blood pressure management Which of the following statements summarizes a reasonable approach to therapy for this patient? A Children who experience a hypertensive emergency should be evaluated for an antecedent cause for their hypertension B Nitroprusside should be avoided as a first-line agent because of the risk of cyanide toxicity in this setting C Particularly for hydralazine, genetic variation affecting drug metabolism is unlikely to be clinically important D Unlike the case with adults, angiotensin-converting enzyme inhibitors (e.g., enalaprilat) may be escalated quickly in children with high renin hypertension Preferred response: A Rationale Children who experience a hypertensive crisis typically have histories of long-standing hypertension Although a child can present with a hypertensive crisis and no antecedent history, this situation is not common Sodium nitroprusside remains a firstline therapy for hypertensive emergencies, largely because of its long history of use, rapid onset, and short half-life that facilitates titration to achieve controlled blood pressure reduction Unfortunately, its safety profile is poor because of its toxic metabolites, such as cyanide and thiocyanate, which can accumulate quickly in persons with conditions commonly associated with hypertension, such as renal insufficiency and failure Clinical studies have demonstrated that hypertensive patients with high renin levels are exquisitely sensitive to angiotensin-converting enzyme inhibitors, which can cause a rapid decline in blood pressure, and thus care must be taken in using them in this population Hydralazine metabolism via acetylation is genetically determined A teenager with a newly diagnosed pheochromocytoma exhibits a blood pressure of 170/110 mm Hg with a heart rate of 100 beats per minute and cool distal extremities beyond the elbows and knees Which of the following medications is contraindicated as a first-line agent for the patient’s hypertension? A Esmolol B Hydralazine C Labetalol D Nicardipine Preferred response: A e123 Rationale The use of pure b-blockers should be avoided in children with suspected catecholamine-secreting tumors because the stimulation of a receptors from pheochromocytoma catecholamines without opposing stimulation of vascular b-adrenergic receptors can severely worsen blood pressure In addition, if b-adrenergic blockade is undertaken before a-adrenergic blockade in such patients and a-blockade is excessive leading to marked vasodilation, the ability to maintain cardiac output by increasing heart rate and cardiac contractility will be impaired A child is admitted from the solid organ transplantation ward to the pediatric intensive care unit with severe hypertension associated with changes in mental status, suggestive of posterior reversible encephalopathy syndrome (PRES) Which of the following statements correctly summarizes the likely clinical scenario? A Common symptoms include seizures, altered mental status, headaches, and visual changes B Magnetic resonance imaging findings include edema of the gray matter in a parietooccipital distribution C PRES is typically associated with corticosteroid prescription for immunosuppression D Radiographic findings resolve more quickly than clinical symptoms associated with PRES after blood pressure is controlled Preferred response: A Rationale PRES is characterized by the sudden onset of hypertension, headaches, altered mental status, seizures, visual loss, and even cortical blindness Neuroimaging studies during PRES typically demonstrate cerebral edema that affects the white matter in a parietooccipital distribution and is associated with immunosuppressive therapy (especially cyclosporine and tacrolimus), acute glomerulonephritis, eclampsia of pregnancy, and hypertensive encephalopathy Typically, clinical signs associated with PRES improve before radiographic findings are resolved Chapter 79: Cellular Respiration What is the best general overview of cellular respiration? A Glycolysis, b-oxidation, and amino acid catabolism are metabolic pathways within the mitochondria B Glycolysis, b-oxidation, and amino acid catabolism provide sufficient ATP to support cellular activities and overall organ function C Glycolysis, b-oxidation, and amino acid catabolism produce carnitine, which is used by the Krebs cycle to produced electron-rich NADH and FADH2, which then feed the mitochondrial electron transport system to produce ATP and reduce oxygen to water D Glycolysis, b-oxidation, and amino acid catabolism produce acetyl-CoA, which is used by the Krebs cycle to produced electron-rich NADH and FADH2, which then feed the mitochondrial electron transport system to produce ATP and reduce oxygen to water Preferred response: D e124 S E C T I O N XV Pediatric Critical Care: Board Review Questions Rationale Cellular respiration consists of a series of three related biochemical reactions: Glycolysis of carbohydrates, b-oxidation of fatty acids, and catabolism of amino acids in the cytosol to produce acetylcoenzyme A (acetyl-CoA) Metabolism of acetyl-CoA in the mitochondrial Krebs cycle to produce electron-rich nicotinamide dinucleotide (NADH) and flavin adenine dinucleotide (FADH2) Shuttling of electrons from NADH and FADH2 to oxygen through the mitochondrial electron transport system in order to synthesize ATP through oxidative phosphorylation A 3-year-old boy with a history of acute lymphoblastic leukemia is admitted with fever and lethargy Vital signs are temperature, 39.3°C; heart rate, 174 beats per minute; respiratory rate, 32 per minute; and blood pressure, 74/30 mm Hg He has an indwelling central line for chemotherapy Laboratory blood tests are sent from this central line, and 60 mL/kg of intravenous fluids are administered, as well as broad-spectrum antibiotics A norepinephrine infusion is also started Following this initial resuscitation and antipyretics, fever has resolved, and the repeat vital signs are heart rate, 130 beats per minute; respiratory rate, 23 per minute; and blood pressure, 93/54 mm Hg The measured Scvo2 now is 82% How can you interpret the Scvo2 result? A Despite improvement in vital signs, resuscitation is not adequate, and an infusion of dobutamine or milrinone is indicated B Scvo2 should be 70%, so this must represent a laboratory error C The high Scvo2 suggests that global oxygen delivery (Do2) has been restored to a level that currently exceeds total body oxygen consumption (Vo2) and may signify an altered state of cellular respiration known as cytopathic hypoxia D The nurse accidentally sent an arterial rather than a venous blood sample Preferred response: C Rationale The venous oxygen saturation sampled from a central vein (preferably at the superior vena cava-right atrial junction) provides a bedside measure of the global balance between oxygen delivery and consumption Normal Scvo2 values are approximately 65% to 75% when arterial oxygen saturation is 100% because the oxygen extraction ratio (ERO2) is typically 0.25 to 0.35 A low Scvo2 suggests that total body oxygen consumption exceeds normal oxygen delivery, whereas a high Scvo2 suggests that total body oxygen consumption may be diminished compared to the normal state of oxygen delivery The inability of cells to effectively utilize oxygen to generate ATP within mitochondria has been termed cytopathic hypoxia Although the routine use of Scvo2 monitoring in septic shock has been called into question, targeted measurement of Scvo2 can provide a bedside measure of the global state of bioenergetic homeostasis What is the product of a four-electron reduction of molecular oxygen? A Hydrogen peroxide B Hydroxyl radical C Triplet oxygen D Water Preferred response: D Rationale Complete reduction of oxygen to water by the addition of four electrons characterizes cellular respiration that occurs in the mitochondria Incomplete oxygen reduction yields reactive oxygen species that may mediate pathophysiology directly or through an alteration of intracellular signaling What is the ultimate source of electrons for oxygen reduction in the mitochondria? A Energy substrate B Hydride anion C Reduced form of flavin adenine dinucleotide (FADH2) D Reduced nicotinamide adenine dinucleotide (NADH) Preferred response: A Rationale Carbohydrates, proteins, and lipids (energy substrates) are oxidized with the resultant formation of hydrides in the form of FADH2, NADH, and NADPH Two electrons derived from each hydride bond represent the reducing equivalents for reduction of oxygen to water In considering resuscitation of a critically ill patient with shock, what rate-limiting process can the intensivist clinically manipulate that will result in the most efficient adenosine triphosphate production in tissues? A Free fatty acid availability B Glucose availability C Oxygen consumption D Oxygen delivery Preferred response: D Rationale Delivery of oxygen to tissues facilitates aerobic metabolism that is nearly 20 times more efficient in terms of adenosine triphosphate production than anaerobic metabolism Although the intensivist can alter the type of energy substrate available, this intervention has limited impact compared with oxygen availability Improved oxygen delivery will hasten lactate clearance Currently, for the most part, the effect of resuscitation on oxygen consumption occurs indirectly through effects on oxygen delivery that intensivists can manipulate directly A child is being monitored during a prolonged resuscitation for meningococcal septic shock Both blood pressure and heart rate are nearly age appropriate, and capillary refill is ,2 seconds Pulse oximetry saturation is 98%, whereas a blood sample derived from a right internal jugular catheter with the distal tip at the junction of the superior vena cava and right atrium indicates a hemoglobin of 10.4 and central venous oxygen saturation (Scvo2) of 81% at a time when the central venous pressure is 12 mm Hg Which of the following conditions most accurately describes this physiologic scenario? A Anemic dysoxia B Cytopathic dysoxia C Hypoxic dysoxia D Stagnant dysoxia Preferred response: B Rationale By all accounts, oxygen delivery appears adequate because oxygen content and cardiac output seem appropriate The high Scvo2 indicates low oxygen consumption CHAPTER 136 Board Review Questions Two days following initiation of resuscitation for a 20% total body surface area scald burn, a toddler remains in the pediatric intensive care unit with a persistent metabolic acidosis Current vital signs include the following: temperature, 38.5°C; breathing rate, 24; heart rate, 130; and blood pressure, 100/70 mm Hg Capillary refill is seconds, and urine output is now ,1 mL/kg/hour Pulse oximetry saturation is 98% on L/min of oxygen delivered by nasal prong Current laboratory findings include the following: pH, 7.33; Paco2, 30 mm Hg; Pao2, 90 mm Hg; HCO3, 15 mmol/L; Na, 143 mEq/L; K, 4.0 mEq/L; Cl, 116 mEq/L; and total carbon dioxide, 15 mEq/L What is the most likely explanation for the patient’s persistent metabolic acidosis? A Impaired lactate clearance B Inadequate central venous preload C Resuscitation with 0.9% saline solution D Unrecognized carbon monoxide poisoning Preferred response: C Rationale This child appears to exhibit normal clinical hemodynamics The metabolic acidosis is hyperchloremic and nonanion gap in nature, likely because of large-volume 0.9% saline solution administration With normal urine output and capillary refill, cardiac output and hence preload are likely adequate Carbon monoxide poisoning, ketoacidosis, and lactic acidosis are all associated with an elevated anion gap For a previously healthy infant with respiratory syncytial virus bronchiolitis and a pulse oximetry saturation of 90%, excluding the increased work of breathing, no change in oxygen extraction, and insignificance of dissolved oxygen, what approximate increase in cardiac output as a percentage, compared with a normal baseline, would be required to maintain oxygen delivery at the baseline status? A 5% B 10% C 15% D 20% Preferred response: B Rationale Do2 is defined as the product of arterial oxygen content of the blood and the cardiac output: Do2 CO Cao2, where Cao2 (1.34 Hb Sao2) (0.003 Pao2) Baseline status: where Do2 delivery of oxygen, Cao2 arterial oxygen content, CO cardiac output, Hb hemoglobin Sao2 oxygen saturation, and Pao2 arterial oxygen tension Assuming baseline Hb saturation is 1.0, if saturation decreases by 10%, then CO must increase by 10% for Do2 to remain constant Which element of shock resuscitation has the greatest direct effect in terms of increasing oxygen delivery? A Administer fluid bolus B Administer red blood cell transfusion C Increase inspired oxygen concentration D Increase cardiac inotropy Preferred response: B Rationale Increasing Hb will increase Do2 directly and linearly, whereas increasing cardiac preload, increasing cardiac contractility, and e125 decreasing cardiac afterload affect Do2 indirectly through an effect on CO Increasing fraction of inspired oxygen increases Pao2 and arterial oxygen saturation (Sao2) indirectly via the Pao2– Sao2 curvilinear relationship Chapter 80: Biology of the Stress Response A 5-month-old male with VACTERL association is admitted to the PICU postoperative day after anogenital reconstruction with compensated pseudomonal septic shock He is quickly and appropriately intubated and resuscitated without any period of hypoxia or hypotension Arterial oxygen saturation is adequate on only moderate ventilator settings, and blood pressure measurements are appropriate on a low-dose epinephrine infusion Urine output, however, has been very low for the last six hours despite repletion of any third-space intravascular losses What is the likely mechanism contributing to his oliguria? A Appropriate activation of vasopressin release and the reninangiotensin-aldosterone system B Inadequate leukocyte cytokine elaboration due to immunoparalysis C Insufficient endogenous production of adrenergic mediators D Ongoing renal hypoperfusion and ischemia Preferred response: A Rationale This child is demonstrating “acute renal success.” In the acute phase of this illness, his stress response system has activated mechanisms to maintain blood pressure and retain circulating volume in the face of systemic infection In this setting, endogenous activation of adrenergic mediators is likely elevated because of the stress response In fact, neural norepinephrine signaling into the macula densa contributes to renin release Because this child’s state of shock was compensated and he had no episodes of hypoxia or hypotension, it is unlikely that global renal hypoperfusion is at play here Immunoparalysis has no direct effect on renal function A 15-year-old young woman with acute respiratory distress syndrome (ARDS) secondary to influenza infection has been intubated and mechanically ventilated in the PICU for 10 days with failure to wean from elevated ventilator settings She has ongoing hemodynamic instability with a persistent vasopressor requirement to maintain adequate blood pressures, slowly progressive renal failure trending towards dialysis, and ongoing hyperglycemia and mild hyperlactatemia despite elevated mixed-venous oxygen saturations Elevated production of which endogenous hormone contributes most to her present metabolic derangement A Glucagon B Insulin C Prolactin D Vasopressin Preferred response: A Rationale Glucagon, in concert with other counterregulatory hormones and adrenergic signaling, increases catabolic and gluconeogenesis mechanisms in the stressed host Insulin is not likely to be significantly elevated in this setting, but if so, would have little effect due to tissue insulin resistance mediated by counterregulatory ... are sent from this central line, and 60 mL/kg of intravenous fluids are administered, as well as broad-spectrum antibiotics A norepinephrine infusion is also started Following this initial resuscitation... delivery The inability of cells to effectively utilize oxygen to generate ATP within mitochondria has been termed cytopathic hypoxia Although the routine use of Scvo2 monitoring in septic shock has... 12 mm Hg Which of the following conditions most accurately describes this physiologic scenario? A Anemic dysoxia B Cytopathic dysoxia C Hypoxic dysoxia D Stagnant dysoxia Preferred response: