Cotrimoxazole (TMP-SMX) in Neonates

General Stance: Use with Caution / Mostly Avoided

• Premature/preterm infants
• Jaundiced neonates
• Neonates with G6PD deficiency

Doses When Used in Neonates

1. Neonatal Sepsis / Pneumonia (Community-Based Programs, e.g., WHO IMCI)

"For an infant < 1 month, give co-trimoxazole (half paediatric tablet or 1.25 mL syrup) twice a day. Avoid co-trimoxazole in neonates who are premature or jaundiced." - WHO IMCI/ANNEX2 guidelines

2. For Serious Neonatal Infections (IV Use - e.g., Stenotrophomonas)

• Loading dose: TMP 3 mg/kg IV
• Maintenance: TMP 1 mg/kg/dose IV q12h (age < 1 month)
• Can be escalated cautiously to TMP 2-5 mg/kg/dose q6-8h in life-threatening infections with close monitoring
• Adjust for renal function (neonatal renal immaturity requires dose reduction)

3. PCP (Pneumocystis jirovecii) Prophylaxis in HIV-Exposed Infants

• Starts at 4-6 weeks of age (not in the first 4 weeks)
• Dose: TMP 150 mg/m²/day + SMX 750 mg/m²/day in 2 divided doses on 3 consecutive days per week

Standard Dosing in Older Infants (≥ 2 months) for Reference

Key Safety Points in Neonates

1. Kernicterus risk - sulfonamide component displaces bilirubin from albumin; absolute contraindication in jaundiced or premature neonates
2. Hemolysis - risk in G6PD-deficient neonates
3. Renal immaturity - neonates have low GFR; SMX can crystallize in tubules; dose reduction required
4. Folate metabolism - TMP inhibits dihydrofolate reductase; theoretical risk of megaloblastic anemia in rapidly growing neonates
5. Avoid in first 4-6 weeks of life as a general rule unless benefit clearly outweighs risk

Bottom Line

• < 4 weeks (especially preterm/jaundiced): Contraindicated / avoid
• 4-6 weeks onward: Can use for PCP prophylaxis in HIV-exposed; use with caution for infections
• Community sepsis management (resource-limited settings): WHO permits 1.25 mL syrup BD in term neonates ≥ 2500 g if no alternative exists, alongside gentamicin

Antifungal Dosing in Neonatal Candidiasis

Types of Neonatal Candidiasis

First-Line Agents

1. Amphotericin B Deoxycholate (AmB-d) - Traditional First Line

• Dose: 1 mg/kg/day IV as a single dose over 2-4 hours
• Duration: Minimum 3 weeks for invasive/disseminated disease
• Preferred in: Urinary tract involvement (CNS candidiasis), preterm neonates
• Monitoring: Serum creatinine, potassium, magnesium, CBC
• Adverse effects: Nephrotoxicity, hypokalemia, fever/chills on infusion, anemia

Neonates tolerate AmB-d better than adults; nephrotoxicity is less common in neonates.

2. Fluconazole - Equally First Line (IDSA/ESCMID)

• Dose: 12 mg/kg/day IV or oral, once daily
• Loading dose: 25 mg/kg IV on Day 1 recommended by ESCMID (due to large volume of distribution in neonates)
• Duration: Minimum 3 weeks (at least 2 weeks after last positive culture)
• Preferred in: Fluconazole-susceptible Candida, CNS involvement (good CSF penetration), stable neonates
• Do NOT use if: C. krusei (intrinsically resistant) or C. glabrata (often resistant)
• Advantage: Available orally, excellent bioavailability, CSF penetration

Lipid Formulations of Amphotericin B

Lipid formulations are not routinely recommended in neonates due to inadequate urinary and CNS concentrations - Dove Medical review.

Echinocandins (Salvage / Alternative)

Echinocandins have poor urinary tract and CSF penetration - use with caution when UTI or meningitis is present. Reserve for fluconazole-resistant or refractory cases. - Red Book 2021

Prophylaxis in Premature Neonates (NICU)

• All infants ≤ 30 weeks gestational age
• Any infant > 30 weeks with risk factors (TPN, broad-spectrum antibiotics, central lines, prior fungal colonization)

Treatment by Clinical Presentation

Key Points

1. Always remove central lines and catheters when invasive candidiasis is diagnosed
2. Perform lumbar puncture and dilated retinal exam in all neonates with suspected invasive candidiasis
3. Duration: Minimum 3 weeks for invasive disease; at least 2 weeks after last negative culture
4. 5-Flucytosine can be added for CNS candidiasis not responding to AmB-d alone (dose: 25 mg/kg/dose q6h - but monitor levels due to renal immaturity)
5. Neonates tolerate AmB-d better than older patients; it remains the gold standard especially when UTI or CNS is involved

Radiological Findings

Key Findings on AP View (Right panel):

1. Massively distended stomach - large gas bubble in the upper abdomen
2. Dilated bowel loops throughout the abdomen
3. Prominent, dense radiopaque object traversing obliquely across the mid-abdomen - appears to be a tube/catheter (possibly UVC or feeding tube) in an abnormal position
4. OG/NG tube in place
5. The bowel gas is diffusely distributed - no typical "double bubble" of duodenal atresia, but overall distension pattern

Key Findings on Lateral View (Left panel):

1. Prominent anterior bowel gas distension with air-fluid levels
2. The same oblique radiopaque structure is visible anteriorly
3. No obvious free intraperitoneal air

Diagnosis

Most Likely: Neonatal Intestinal Obstruction / Ileus

Differential Diagnosis:

1. Hirschsprung Disease - diffuse gaseous distension with failure to pass meconium; lateral view may show absent rectal gas
2. Meconium Ileus - bubbly/frothy appearance in RLQ (from meconium mixed with air), associated with cystic fibrosis
3. Paralytic ileus - from sepsis, electrolyte imbalance, or post-surgical
4. Functional immaturity of bowel - in preterm neonates

Regarding the Radiopaque Object:

Recommended Next Steps

1. Clinical correlation - has baby passed meconium? Age at presentation?
2. Rectal examination / rectal suction biopsy if Hirschsprung suspected
3. Contrast enema (Gastrografin) for meconium ileus/Hirschsprung
4. Sweat chloride test / CF genotyping if meconium ileus suspected
5. Check UVC/UAC position - reposition catheter if malpositioned
6. Serial X-rays to monitor progression

Note: This is a radiological interpretation for educational purposes. Clinical correlation with the neonatal history (gestational age, onset, feeding, meconium passage) is essential for definitive diagnosis.

Gross Classification of EA/TEF - Types C, D & E

Full Gross Classification (for context)

Key Differences: Types C vs D vs E

TYPE C - EA with Distal TEF

• Esophageal atresia: YES - proximal esophagus ends in a blind pouch
• Fistula location: The distal esophagus connects to the trachea (usually at the carina or just above)
• Proximal fistula: ABSENT
• Stomach gas: PRESENT (air enters stomach via the distal fistula from trachea)
• Clinical features:
  • Excessive salivation and drooling at birth
  • Choking, gagging, cyanosis with first feed
  • Abdominal distension (air passes into stomach through distal fistula)
  • Aspiration pneumonia from gastric acid reflux up through the fistula
• X-ray: OG tube coiled in upper pouch; gas present in abdomen (due to distal fistula)
• Prenatal: Polyhydramnios + small/absent stomach bubble

TYPE D - EA with Both Proximal AND Distal TEF

• Esophageal atresia: YES - proximal esophagus ends in a blind pouch
• Fistula location: TWO fistulae - one from the proximal pouch to trachea AND one from the distal esophagus to trachea
• Clinical features:
  • All features of Type C PLUS
  • Additional proximal fistula makes aspiration even worse
  • Saliva directly enters trachea through the proximal fistula
  • Higher aspiration risk than Type C
  • Abdominal distension present (distal fistula still allows air into stomach)
• Surgical challenge: Both fistulae must be identified and divided - risk of missing the proximal one

TYPE E - TEF without Esophageal Atresia ("H-type")

• Esophageal atresia: ABSENT - esophagus is completely intact and continuous
• Fistula location: A narrow, oblique fistula connecting an intact trachea to an intact esophagus, usually in the lower cervical/upper thoracic region (runs obliquely from trachea above to esophagus below)
• No blind pouch
• Clinical features - very different from C and D:
  • Delayed diagnosis (often missed in newborn period)
  • Intermittent symptoms: coughing/choking only with feeds
  • Recurrent aspiration pneumonia
  • Abdominal distension with crying (air enters esophagus → stomach)
  • No excessive drooling (esophagus is patent)
  • No OG tube obstruction
• Diagnosis: Contrast esophagogram (tube esophagram) in prone position; bronchoscopy
• Surgery: Right cervical approach (because fistula is high), NOT thoracotomy (unlike C/D)

Summary Comparison Table

Key Memory Aid

• Type C = most Common - proximal pouch, one fistula (distal)
• Type D = Double fistula (proximal + distal) + atresia
• Type E = Esophagus intact - "H-type" - no atresia, fistula only

Causes / Etiology of Tetralogy of Fallot (TOF)

The Core Embryological Reason

Unequal division of the conotruncus with anterior and cephalad (superior) malalignment of the infundibular (outlet) septum during the 5th week of gestation

How One Defect Creates Four Anomalies

"The primary morphologic abnormality, anterior and superior displacement of the infundibular septum, results in a malalignment VSD, overriding of the aortic valve, and obstruction of the RVOT. RV hypertrophy is a secondary occurrence." - Mulholland & Greenfield's Surgery, 7e

Neural crest-derived tissue plays a central role - failure of neural crest cell migration into the cardiac outflow tract is the underlying cellular mechanism.

Genetic Causes (25-30% of cases have a genetic basis)

Environmental / Maternal Risk Factors

Summary: Why Does TOF Happen?

CAUSE → Abnormal neural crest cell migration 
            ↓
Unequal conotruncal division (Week 5 gestation)
            ↓
Anterior malalignment of infundibular septum
            ↓
┌────────────────────────────────────┐
│ 1. Pulmonary stenosis (RVOTO)      │
│ 2. Large malaligned VSD            │  ← ALL 4 from ONE defect
│ 3. Overriding aorta                │
│ 4. RV hypertrophy (secondary)      │
└────────────────────────────────────┘
            ↓
Right-to-left shunt → CYANOSIS

• Mulholland & Greenfield's Surgery, 7e, p. 4416-4417