PICU Board ReviewJanuary 2014

Stanford UniversityLoren D. Sacks, MD

Ouch!!The most common thoracic injury seen in children is:a. Pulmonary contusionb. Aortic rupturec. Clavicular fractured. Myocardial contusione. Tracheal disruption

You’ve got the shakes… A 6-year-old with renal failure develops seizures after 6 days in the PICD. Her medicationsinclude fentanyl, meperidine, digoxin, atracurium, meropenem, and dobutamine. Which of thefollowing is MOST likely implicated in her seizures?

a. Toxic metabolite of atracuriumb. Digoxin toxicityc. Accumulation of fentanyl metabolitesd. Meperidinee. Meropenem

AtracuriumNon-depolarizing neuromuscular blocking

agent, first synthesized in 1974Cisatracurium = purified R-cis R-cis isomer

Metabolization of Paralytics:Succinylcholine, Mivacurium CholinesterasesVecuronium Deacetylated and excreted in

bileAtracurium Hoffman degradation

Side effects:Renal failure can lead to increased laudanosine

DigoxinPurified glycoside similar to Digitoxin

(isolated from the foxglove plant)First described by William Withering in 1785

Mechanism: Binds to myocardial Na-K-ATPase pumpIncreases intracellular Ca+Longer Phase 4 and 0

Adverse effects: “PAT with Block” Seizures ~ 0.1%

FentanylSynthetic opioid first synthesized by Janssen

Pharmaceuticals in 1959Mechanism of actions:

Bind mu-receptors to inhibit neurotransmitter release in pain fibers

High lipophilicity allows for easy CNS penetration

Clearance:Primarily cleared by the liverNo active metabolites

MeperidineAlso known as…

Demerol!First synthetic opioid (1932)

Acts primarily at mu recepMay act at the kappa-receptor to stop shivering

Clearance: Metabolized to normeperidineNormeperidine is cleared in the urineElevated normeperidine levels are associated

with seizures (often fatal)

MeropenemCarbapenam antibiotic

Similar class: Imipenem, ErtapenamMechanism:

Beta-lactam inhibits bacterial cell-wall synthesis

Resistant to beta-lactamaseAdverse Effects:

Most common = diarrhea, nausea, vomitingC.diff in 3.6% of patients taking Meropenem

You’ve got the shakes… A 6-year-old with renal failure develops seizures after 6 days in the PICD. Her medicationsinclude fentanyl, meperidine, digoxin, atracurium, meropenem, and dobutamine. Which of thefollowing is MOST likely implicated in her seizures?a. Toxic metabolite of atracuriumb. Digoxin toxicityc. Accumulation of fentanyl metabolitesd. Meperidinee. Meropenem

My heart is racing!A 14-year-old male quadriplegic is postoperative day 7 following spinal surgery to stabilize a C4-5 fracture. He had been doing well for several days. You are called to his bedside emergently for acute tachycardia (HR 175) and hypertension (BP 220/130). He is awake and diaphoretic. You note that he has been oIiguric for over 10 hours. The best initial response in this scenario is to:

a. Obtain blood cultures and start broad spectrum antibiotics·b. Obtain an emergent head CT scanc. Institute beta blocker therapyd. Catheterize the bladdere. Administer intravenous fluids until urine output is established

Bladder Innervation

Bladder Function with SCIThroaco-lumbar Injury (Sympathetic)

Decreased internal sphincter toneDecreased distensibility of the bladder

Sacral Injury (Parasympathetic)Increased internal sphincter toneIncreased bladder distension

Rostral Spine Injury (Somatic)Stretch receptors and spinal reflexes

intact, but loss of EUS controlFrequently develop spasms as the

bladder contracts against a closed EUS

My heart is racing!A 14-year-old male quadriplegic is postoperative day 7 following spinal surgery to stabilize a C4-5 fracture. He had been doing well for several days. You are called to his bedside emergently for acute tachycardia (HR 175) and hypertension (BP 220/130). He is awake and diaphoretic. You note that he has been oIiguric for over 10 hours. The best initial response in this scenario is to:

a. Obtain blood cultures and start broad spectrum antibiotics·b. Obtain an emergent head CT scanc. Institute beta blocker therapyd. Catheterize the bladdere. Administer intravenous fluids until urine output is established

Speaking of hearts…A 4-year-old girl status post complete repair of Tetralogy of Fallot develops tachycardia on the first postoperative night. Her surface ECG (bottom) and simultaneous univentricular atrial wire recording (top) are shown in the figure below.

Based on the electrocardiograms the most likely diagnosis of her tachycardia is:a. Atrial fibrillationb. Atrial flutterc. Junctional ectopic tachycardiad. Ectopic atrial tachycardiae. Sinus tachycardia

Atrial Fibrillation

Automatic signals from multiple foci in the atrium, often around the pulmonary veins

Result in atrial “quivering”, but near-normal ventricular conduction

Atrial Flutter

Rapid atrial contractions due to a re-entrant circuit (usually in the RA in infants)

Rare in infancy, this condition usually resolves after conversion

Characteristic saw-tooth patterns in II, III, and aVF

Ectopic Atrial Tachycardia

Impulse arises from a single ectopic focus in the atrium

Accounts for 10-20% of all pediatric SVT

Back to the question at hand…

Junctional Ectopic TachycardiaEnhanced automaticity in the region of the

AV-NodeFeatures:

AV DissociationVentricular rate > Atrial rateUsually occurs in the immediate post-op period

Causes: May be inflammation/injury of conducting fibersFamily history in 50-55% of adult patientsMost common occurrence is after Tet Repair

Take a deep breath…Which of the following findings in a tracheal aspirate is MOST indicative of bacterial pneumonia in a patient who has been ventilated in your PICU for one week?

a. 15,000 colony-forming units of Gram-negative rods on a bronchoalveolar lavageb. Gram-positive organisms in chains on a gram stain of tracheal aspiratec. Positive tracheal aspirate for Pseudomonasd. Lobar infiltrate that clears within 24 hourse. Positive blood culture for coagulase-negative staphylococci

Make a match…

Na+ Cl- K+ CO2156 110 3.5 22

130 90 4.0 22

148 93 2.8 28

130 92 4.5 15

Match the disease entity with the most likely set of serum electrolytes: a) Diabetes insipidusb) Syndrome of inappropriate antidiuretic hormone secretionc) Diabetes insipidusd) Hyperaldosteronism

Our friend the nephron

Diabetic KetoacidosisAnion-Gap Acidosis and Hyperglycemia

Low insulin inability to utilize glucoseProduction of beta-hydroxybutyrate, acetoacetic

acidPotassium

Extracellular shifts due to acidosis, lack of insulinWasted in urine (H-K-ATPase symporter)

SodiumPseudohyponatremia due to hyperglycemia“True Na” = (Measured Na) + 1.6x[(Glucose -

100)/100]

Diabetes InsipidusCentral DI:

Lack of ADH production from the posterior pituitary

Nephrogenic DI:Inability of the collecting duct to respond to ADHV2 Receptor located on X-q28Aquaporin-2 Receptor accounts for ~10% of

congenital cases Loss of ADH:

Inability to resorb free H2O excessive, dilute UOP

Hypovolemia increased aldosterone

SIADHRelease of excessive ADH

Associated with CNS pathology (tumor, TBI, etc.)

Can be induced by carbamazepine, cyclophosphamide

Results: Retention of H2O volume expansionDepressed aldosterone

HyperaldosteronismAldosterone

Primary mineralocorticoid Synthesized in zona glomerulosa

Normal actions: Distal convoluted tubule K+ and H+

excretionCollecting duct Na+ and Cl- resaborptionH2O follows Na+

Excessive states: Metabolic alkalosis and hypokalemia

Make a match…

Na+ Cl- K+ CO2156 110 3.5 22

130 90 4.0 22

148 93 2.8 28

130 92 4.5 15

Match the disease entity with the most likely set of serum electrolytes: a) Diabetic ketoacidosisb) Syndrome of inappropriate antidiuretic hormone secretionc) Diabetes insipidusd) Hyperaldosteronism

References Rogers’ Textbook of Pediatric Intensive Care, 4th Edition Livingstone, “Pharmacology of Muscle Relaxants and their Antagonists” 2000 Dean M. “Opioids in renal failure and dailysis” Journal of Pain and Symptom Management, 2004 Labroo RB, et.al. “Fentanyl metabolism by human hepatic and intestinal cytochrome P450 3A4:

implications for interindividual variability in disposition, efficacy, and drug interactions” Drug Metabolism and Disposition 1994

Arnold R., Verrico P., and Davison SN, “Opioid use in renal failure”, Medical College of Wisconsin, 2009

Thulhammer F. and Horl WH, “Pharmacokinetics of meropenem in patients with renal failure and patients receiving renal replacement therapy” Clinical Pharmacokinetics 2000

Yoshimura N, “Bladder afferent pathway and spinal cord injury: possible mechanisms inducing hyperreflexia of the urinary bladder”, Progress in Neurobiology 1999

“Guidelines for Diagnosis and Reporting of Ventilator Associated Pneumonia” CDC.gov, 2013 Fagon J, et.al. “Invasive and noninvasive strategies for management of suspected ventilator-

associated pneumonia.” Annals of Internal Medicine, 2000 Chastre J, et.al. “Evaluation of bronchoscopic techniques for the diagnosis of nosocomial

pneumonia.” American Journal of Respiratory and Critical Care Medicine, 1995 Imamura M, et.al. “Prophylactic amiodarone reduces junctional ectopic tachycardia after

tetralogy of Fallot repair”. Journal of Thoracic and Cardiovascular Surgery.2011 UpToDate.com (multiple topics) Emedicine.com (multiple topics)