Critical Thinking PICU QUIZ

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1 Critical Thinking DOI / Vinayak Patki* *Chief Consultant, Advanced Pediatric Critical Care Centre & Head, Dept of Pediatrics, Wanless Hospital, Miraj, , Maharashtra, India Received: 01-Apr-18/Accepted: 15-Apr-18/Published online: 30-Apr-18 Q.1 Which of the following statements regarding serum creatinine (Cr) and glomerular filtration rate (GFR) in the pediatric population is true? A. At birth, the healthy newborn s GFR is equivalent to adult levels and serum Cr is low. B. Maintenance of a stable creatinine in a pediatric patient with a prolonged ICU course is pathognomonic of preservation of renal function. C. Serum creatinine lacks sensitivity to acute and small changes in GFR. D. The relationship between GFR and serum Cr is linear in children. Q.2 Which of the following factors may be responsible for a decrease in serum creatinine levels? A. Anorexia B. Muscular body habitus C. Use of antibiotics D. Use of cimetidine Q.3.During states of reduced cardiac output and intravascular volume depletion, which substances help preserve renal vascular perfusion? A. Angiotensin II B. Kallikrein C. Prostaglandin I2 D. Vasopressin Q.4. Which of the following distinguishes typical and atypical hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)? Correspondence: Dr. Vinayak Patki, MB,DNB,FCCP,FIAP. Chief, Advanced Pediatric Critical Care Centre & Head, Dept of Pediatrics, Wanless Hospital, Miraj, , Maharashtra, India. Phone: , - patkivinayak@gmail.com A. Atypical HUS is the only one of these diseases that results from activation of the alternative complement pathway. B. Neurologic disease only occurs in TTP. C. The treatment of TTP but not HUS relies on platelet transfusion. D. TTP involves a deficiency or antibodymediated inactivation of ADAMTS13. Q.5. 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 Q.6: A 9-year-old male began hemodialysis for acute kidney injury due to multiorgan failure from septicemia. He has tolerated his sessions well but developed significant thrombocytopenia, and concern for heparininduced thrombocytopenia was raised. Which of the following methods is most likely to assure effective hemodialysis sessions and also address the concern for heparin-induced thrombocytopenia? A. Change unfractionated heparin to lowmolecular-weight heparin. B. Eliminate heparin and use citrate-containing dialysate. C. Give a heparin bolus at the start of hemodialysis but avoid the use of continuous infusion. D. Use half the previous dose of unfractionated heparin. Q.7. A 5-year-old male has Shiga toxin mediated hemolytic uremic syndrome. He is anuric with significant electrolyte abnormalities refractory to medical management; he will likely require 89

2 renal replacement therapy for the next 1 to 2 weeks. Of the following, which anatomic location would be the preferred option for placement of a hemodialysis catheter? A. Femoral vein B. Left internal jugular vein C. Right internal jugular vein D. Subclavian vein Q.8. Of the following clinical scenarios, which would be better served by a renal replacement therapy other than continuous renal replacement therapy (CRRT)? A. A 5-month-old female with complications following heart transplant, on ECMO B. A 12-year-old male with meningococcemia, hypotension, on multiple vasoactive drugs, with oliguria and serum creatinine 2.8 mg/dl C. A 14-year-old female with sepsis and multiorgan dysfunction, including renal failure, following orthotopic liver transplant D. A 17-year-old male with acute methanol intoxication Q.9. 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 / 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 Q.10. An 7 year child is being treated for Burkitt lymphoma with rasburicase in an effort to reduce the risk of acute kidney injury secondary to tumor lysis syndrome. Metabolic acidosis with rising lactate develops acutely. Which of the following would explain the pathophysiology involved in this scenario? A. Impaired renal ammonium synthesis B. Methemoglobinemia C. Pulmonary hypertension with right-to-left intracardiac shunt D. Renal bicarbonate wasting Answers Answer Q.1: C : Serum creatinine lacks sensitivity to acute and small changes in GFR Serum creatinine is the most commonly used laboratory study to assess renal function in clinical practice. It is simple, convenient, and practical requiring a single blood sample and therefore well suited for serial examination. However, the relationship between serum creatinine and GFR is complex and is influenced by several factors other than GFR. Therefore, at best, creatinine provides a crude estimate of the GFR. As illustrated in Fig. Q74.1, serum creatinine bears an inverse, nonlinear relationship with GFR and lacks sensitivity to acute and small changes in GFR. Notably, at low levels of serum creatinine corresponding to normal renal function, a substantial decrease in GFR may occur before being reflected by even a small increase in serum creatinine. In contrast, at higher levels of serum creatinine associated with renal failure, the same absolute rise in creatinine reflects a much smaller loss of remaining renal function. To a first approximation, every doubling of the serum creatinine represents a 50% decline in remaining GFR. Creatinine generation is affected by growth in addition to diet and illness, as seen with adults. The reference range for serum creatinine levels representing normal GFR will thus vary with age, size, and gender after puberty. The relationship between GFR and serum creatinine is therefore particularly complex in children. Maturational changes in serum creatinine and GFR do not parallel one another. GFR is physiologically low at birth, whereas serum creatinine is elevated; however, because of fetal-maternal-placental 90

3 equilibration of creatinine, the elevated creatinine is not indicative of the infant s renal function but rather the mother s. Following birth, GFR steadily increases, reaching adult levels over the next 2 years. Serum creatinine, on the other hand, declines over the first few weeks, becoming reflective of the infant s renal function. The creatinine level then remains stable until approximately 2 years of age as muscle mass accrues proportionally to the increase in GFR. Beyond 2 years of age, when GFR per BSA has fully matured, the ongoing accretion of muscle results in a progressive rise in serum creatinine until adolescence, when adult levels are achieved (0.7 mg/dl for adolescent females and 0.9 mg/dl for adolescent males). Superimposition of a severe or chronic illness associated with malnutrition and muscle wasting makes the interpretation of GFR from serum creatinine alone even more difficult in the pediatric patient. For example, at first glance, maintenance of a stable creatinine in a patient with a prolonged ICU course may be reassuring for preservation of renal function; however, if significant muscle atrophy has occurred, this actually suggests deterioration of renal function. In the steady state when height is used as a surrogate for growth, there is a strong correlation of the parameter Ht/SCr and GFR. Answer Q.2: A : Anorexia Although the majority of serum creatinine is eliminated by glomerular filtration, a small but unpredictable amount is eliminated by tubular secretion and gastrointestinal degradation. Proximal tubular secretion of creatinine typically accounts for approximately 10% of its elimination, although considerable inter- and intraindividual variability exists. At normal levels of glomerular filtration rate (GFR), the impact of tubular secretion on GFR is minimal. However, with deteriorating renal function, the proportion of secreted versus filtered creatinine increases, resulting in a lower serum creatinine than predicted for the true level of GFR, thus decreasing the sensitivity for serum creatinine to detect mild decreases in renal function. A similar phenomenon occurs in the setting of moderate-to-severe renal failure, when the bacterial degradation of creatinine within the gastrointestinal tract can become clinically significant, leading to a decrease in serum creatinine concentration. Failure to recognize the influence of tubular secretion and gastrointestinal elimination on serum creatinine values can overestimate renal function and may lead to higher, inappropriate dosing of medications. Conversely, in patients with advanced kidney failure, administration of medications (eg, cimetidine, trimethoprim) that inhibit the tubular secretion of creatinine or administration of antibiotics that mitigate the gastrointestinal degradation of creatinine may elevate serum creatinine and lead to the subsequent underestimation of GFR without any true change in renal function. If not appreciated, this may be misconstrued as worsening renal function and lead to potential underdosing of medications. Proper interpretation of the serum creatinine as a measure of GFR requires the physician to be knowledgeable about the clinical variables, physiologic processes, and analytic factors that can affect creatinine levels (Table Q74.2). Although the clinical laboratory provides normative reference ranges alongside the results, clinicians should confirm that the reported references are age appropriate and also realize that if the patient has decreased muscle mass (eg, spina bifida, anorexia), even these ageappropriate reference ranges will be incorrect. Answer Q.3: C.Prostaglandin I2 Ration ale Vasopressin acts indirectly to increase vascular volume by stimulating salt and water reabsorption. Angiotensin II overall contributes to reduced renal blood flow, but it will also cause efferent arterioles to vasoconstrict to improve filtration fraction at the expense of blood flow. Prostaglandin I2 released locally will cause afferent arteriolar vasodilation and counteract the vasoconstrictive effects of the systemic angiotensin II. Answer Q.4: D:TTP involves a deficiency or antibody-mediated inactivation of ADAMTS13. Neurologic and other extrarenal manifestations can occur in all three forms of the thrombotic microangiopathies. Activation of the alternative complement pathway may be the underlying pathologic mechanism in all three diseases. None of the diseases should be treated with platelet transfusion routinely, as the thrombotic microangiopathy may worsen. 91

4 Answer Q.5: B:Loop diuretics Loop diuretics (eg, furosemide, bumetanide, torsemide) are antagonists of the Na+/K+2Cl 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. Answer Q.6: B.Eliminate heparin and use citratecontaining dialysate. Heparin-induced thrombocytopenia is a well known but rare complication in patients exposed to heparin. Patients on hemodialysis are at risk for forming clots when their blood is exposed to the extracorporeal circuit. Although heparin is the most common anticoagulant prescribed during hemodialysis, any method of anticoagulation can be utilized. Citrate functions as an anticoagulant due to its ability to chelate calcium, which is an essential cofactor in the clotting cascade and for platelet activation. Citrate can be administered as an infusion, or citratecontaining dialysate may be used. The first is used mostly in continuous renal replacement therapy (CRRT). Dialysate solutions that have substituted some of the acetate in the acid bath with citrate have been found to function well as an anticoagulant. The citrate in the dialysate will bind calcium locally at the dialyzer membrane, preventing clotting within the dialyzer. Monitoring of ionized calcium is not required as the concentration of citrate is low, and thus the patient is not at risk for hypocalcemia. The risk for heparin-induced thrombocytopenia (HIT) is not dose dependent, thus reducing the dose will not be beneficial. Use of low-molecular-weight heparin (LMWH) is not a good choice, as risk of HIT, though lower, is still a possibility; therefore for patients found to have HIT from unfractionated heparin, LMWH is contraindicated. Changing modality will not mitigate the risk of HIT due to heparin exposure. Answer Q.7: C: Right internal jugular vein The most desirable site for a double lumen hemodialysis catheter is the right internal jugular vein; it provides access to a high-flow area in the superior vena cava/right atrium, permits a straight venous path for the operator from insertion site to the target location, can be readily accessed for insertion of either tunneled or nontunneled catheters depending on the indication, allows ambulation and reduces discomfort for the patient as compared to the femoral site, and is less susceptible to complicating venous stenosis that will limit future permanent vascular access creation such as AV fistula. By contrast, subclavian access is associated with increased risk of stenosis that would result in loss of potential sites for AV-fistula formation in the ipsilateral arm, and therefore it is not recommended. A femoral vein is associated with an increased risk of infection and limits ambulation. A saphenous vein is too small to support a double lumen venous hemodialysis catheter. A left internal jugular vein is more challenging for successful placement of the catheter. Answer Q.8: D.A 17-year-old male with acute methanol intoxication CRRT is a reasonable choice for nearly any critically ill patient who requires renal replacement therapy. CRRT is appropriate for patients with volume overload or renal dysfunction in the setting of hypotension or multisystem organ failure to provide continuous renal support for fluid and metabolic balance. CRRT machines can be connected directly to an ECMO circuit. Acute intoxications call for rapid removal of the toxic molecule; for this reason, a more efficient modality such as intermittent hemodialysis would be more appropriate. Answer Q.9 : C.Intravenous nicardipine Rationle 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 nicar dipine is the best agent of the available choices. Answer Q.10: B :Methemoglobinemia Recombinant urate oxidase (rasburicase) exerts its pharmacologic activity by enzymatic oxidation of uric 92

5 acid into allantoin. It works rapidly, often dropping the uric acid to less-than-normal levels within hours. Although contraindicated in patients with glucose- 6-phosphate dehydrogenase deficiency, overall it is well tolerated. The traditional recommended dosage is 0.15 to 0.20 mg/kg administered intravenously daily for up to 7 days. Investigators recommend the use of rasburicase as the first-line intervention for high-risk patients and as backup moderaterisk therapy for patients in whom hyperuricemia develops despite the use of allopurinol and hydration. Rasburicase is remarkably well tolerated. The rare but serious adverse events that require prompt and permanent discontinuation of rasburicase are methemoglobinemia and hemolysis. How to cite this article: Patki V. Critical Thinking - PICU quiz - Critical care Nephrology. J Pediatr Crit Care 2018;5(2): How to cite this URL: Patki V. Critical Thinking - PICU quiz -Critical care Nephrology. J Pediatr Crit Care 2018;5(2): Available from: 93