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Case 009: Neonate with Shock - Critical Coarctation

Presentation

A 10-day-old male infant is brought to the ED by his parents. Born full-term, discharged home at 48 hours with normal newborn screen. Doing well until today when he became increasingly fussy, refused to feed, and appeared "gray."

Vital Signs: - Heart rate: 180 bpm - Blood pressure (right arm): 68/42 mmHg - Respiratory rate: 60 - SpO2: 98% right hand, 85% right foot - Temperature: 36.5°C

Exam: - Ashen gray, mottled, lethargic - Tachypneic with grunting - Liver palpable 4 cm below costal margin - Absent femoral pulses - Weak brachial pulses - Cool lower extremities

Initial Workup

Labs: - Lactate: 8.5 mmol/L (severely elevated) - pH: 7.18 (metabolic acidosis) - Creatinine: 1.8 mg/dL (elevated - poor renal perfusion) - Glucose: 45 mg/dL

Chest X-ray: - Cardiomegaly - Pulmonary edema

ECG: - Sinus tachycardia - RVH pattern

Clinical Reasoning

Question 1: What is the critical physical exam finding?

Answer **Absent femoral pulses + differential cyanosis (98% upper, 85% lower)** This combination indicates: - Left-sided obstructive lesion - Ductus arteriosus has closed - Lower body now dependent on antegrade flow through obstruction - → Inadequate perfusion → shock Classic for **critical coarctation** or **interrupted aortic arch**

Question 2: Why did this present at day 10 and not earlier?

Answer **Ductal closure timing** - At birth, ductus provides bypass around coarctation - Passed CCHD screen at 24-48 hours (ductus still open) - Ductus typically closes days 3-10 of life - As ductus closes → lower body becomes dependent on flow through coarctation - If obstruction severe → inadequate perfusion → metabolic acidosis → shock This is why **coarctation is the most commonly missed CCHD** - presentation after discharge.

Question 3: What is the IMMEDIATE first intervention?

Answer **PROSTAGLANDIN E1 (PGE1)** - do NOT wait for echo confirmation **Starting dose:** 0.05-0.1 mcg/kg/min IV **Expected effects:** - Reopens ductus arteriosus - Restores lower body perfusion - Lactate should improve within hours - Femoral pulses may become palpable **Side effects to anticipate:** - Apnea (30%) - prepare airway equipment - Fever - Hypotension initially - Flushing

Management

Question 4: What is the full resuscitation approach?

Answer **ABCs + PGE1:** **A - Airway:** - Prepare for intubation (PGE apnea) - Low threshold to intubate if worsening **B - Breathing:** - Supplemental oxygen cautiously (avoid high FiO2 which can close ductus) - Ventilatory support as needed **C - Circulation:** - IV access (may need IO if difficult) - **PGE1** - critical intervention - Fluid bolus (10 mL/kg) - careful, may worsen pulmonary edema - Correct hypoglycemia - Correct acidosis (usually improves with perfusion) - May need inotropic support **Avoid:** - High FiO2 (promotes ductal closure) - Excessive volume (already fluid overloaded from HF)

Echo Results

Echocardiogram: - Severe discrete coarctation at isthmus - Hypoplastic transverse arch - PDA now open (after PGE) with left-to-right flow - Severely depressed LV function (EF 30%) - No VSD or other defects

Question 5: The LV function is severely depressed. Does this change surgical timing?

Answer **No - surgery is still urgent** LV dysfunction in critical coarctation is due to: - Acute afterload (severe obstruction) - Will improve after repair **Plan:** 1. Stabilize with PGE (usually 24-72 hours) 2. Allow metabolic derangements to correct 3. Surgical repair once stable 4. LV function typically recovers post-repair Delaying surgery allows worse end-organ damage.

Question 6: What surgical options exist?

Answer **Standard repair: Extended end-to-end anastomosis** - Resection of coarctation segment - Often includes arch augmentation if hypoplastic **Alternatives:** - Subclavian flap aortoplasty (less common now) - Patch aortoplasty (higher recurrence risk) **Not appropriate acutely:** - Balloon angioplasty (reserved for recurrence) - Stenting (older patients)

Post-Operative Course

Surgery successful. Day 3 post-op: - Extubated - Lactate normalized - Femoral pulses now palpable - BP right arm and leg equal - LV function improving (EF 45%)

Question 7: What long-term follow-up is needed?

Answer **Lifelong cardiology follow-up required:** 1. **Blood pressure monitoring** - Late hypertension common (30-40%) - Even with successful repair 2. **Surveillance for recoarctation** - Echo with Doppler gradients - May need CT/MRI for arch assessment 3. **Bicuspid aortic valve screening** - 50-85% of CoA patients have BAV - Needs ongoing surveillance 4. **Aortopathy screening** - Risk of ascending aortic dilation - Independent of BAV 5. **Exercise testing** at appropriate age

Teaching Points

  1. Absent femoral pulses in sick neonate = coarctation until proven otherwise
  2. PGE1 is lifesaving - start before echo if clinical suspicion high
  3. Coarctation presents when ductus closes (typically day 3-10)
  4. CCHD screening can miss coarctation - educate families about warning signs
  5. LV dysfunction from afterload is reversible after repair
  6. Lifelong follow-up for hypertension, recoarctation, aortopathy