Episode 196: The Critically Ill Infant

We discuss an approach to the critically ill infant.

Ellen Duncan, MD, PhD
Brian Gilberti, MD

May 1st, 2024 Download Leave a Comment Tags:

Show Notes

The Critically Ill Infant: THE MISFITS


  • ‘T’ in the mnemonic stands for trauma, which includes both accidental and intentional causes.
  • Considerations for Non-accidental Trauma:
    • Stresses the importance of considering non-accidental trauma, especially given that it may not always present with obvious external signs.
  • Anatomical Vulnerabilities:
    • Highlights specific anatomical considerations for infants who suffer from trauma:
      • Infants have proportionally larger heads, increasing their susceptibility to high cervical spine (c-spine) injuries.
      • Their liver and spleen are less protected, making abdominal injuries potentially more severe.


  • 5 T’s of Cyanotic Congenital Heart Disease: Introduces a mnemonic to help remember key right-sided ductal-dependent lesions:
    • Truncus Arteriosus: Single vessel serving as both pulmonary and systemic outflow tract.
    • Transposition of the Great Arteries: The pulmonary artery and aorta are switched, leading to improper circulation.
    • Tricuspid Atresia: Absence of the tricuspid valve, leading to inadequate development of the right ventricle and pulmonary circulation issues.
    • Tetralogy of Fallot: Comprises four defects—ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta.
    • Total Anomalous Pulmonary Venous Connection (TAPVC): Pulmonary veins do not connect to the left atrium but rather to the right heart or veins, causing oxygen-rich blood to mix with oxygen-poor blood.
  • Other Significant Conditions:
    • Ebstein’s Anomaly: Malformation of the tricuspid valve affecting right-sided heart function.
    • Pulmonary Atresia/Stenosis: Incomplete formation or narrowing of the pulmonary valve obstructs blood flow to the lungs.
  • Left-sided Ductal-Dependent Lesions:
    • Conditions such as aortic arch abnormalities (coarctation or interrupted arch), critical aortic stenosis, and hypoplastic left heart syndrome are highlighted. These generally present with less obvious cyanosis and more pallor.
  • Diagnostic and Management Considerations:
    • Routine prenatal ultrasounds detect most cases, but conditions like coarctation of the aorta and TAPVC might not be apparent until after birth when the ductus arteriosus closes.
    • Emphasizes the importance of a thorough physical exam: checking for murmurs, assessing hepatosplenomegaly, feeling for femoral pulses, measuring pre- and post-ductal saturations, and taking blood pressures in all four limbs.
  • Treatment Recommendations:
    • Early initiation of alprostadil (a prostaglandin) for patients with suspected ductal-dependent lesions to maintain ductal patency.
    • Preparedness for potential complications from alprostadil treatment, such as apnea and hypotension, which may necessitate intubation and hemodynamic support.


  • Focuses on acute salt-wasting crisis in undiagnosed Congenital Adrenal Hyperplasia (CAH).
  • Electrolyte imbalances: ↓Na, ↑K, ↓HCO3, ↓Glu.
  • Treatment: hydrocortisone (25mg for babies, 50mg for kids, 100mg for adults).


  • Electrolyte abnormalities such as hypoglycemia (values: <60 in infants, <40 in neonates).
  • Broad differential.
  • Rule of 50s for correction: D% x #ml/kg fluid = 50.

Inborn Errors of Metabolism

  • Major classes include organic acidurias (profound anion gap metabolic acidosis) and urea cycle defects (hyperammonemia)
  • Recommendation: Draw gas and ammonia level.


  • Emphasized as a critical condition in the differential diagnosis for ill infants, though placed later in the mnemonic for easier recall.
  • Presentation and Diagnosis:
    • Sepsis in infants often presents nonspecifically, making early detection challenging.
    • Immediate drawing of blood cultures upon suspicion of sepsis.
  • Initial Treatment:
    • Prompt initiation of antimicrobials and fluids.
    • Use of vancomycin for gram-positive and MRSA coverage, a third-generation cephalosporin or pip-tazo for broad bacterial coverage, and acyclovir for HSV. (tailor based on age and institutional guidelines)
  • Supportive Care:
    • Highlights the necessity of fluid resuscitation to stabilize the patient.


  • Formula-Related Electrolyte Imbalances:
    • Incorrect mixing of infant formula can cause hypo- or hypernatremia.
  • Consequences of Electrolyte Imbalances:
    • Both conditions can lead to severe outcomes including altered mental status, seizures, coma, and potentially death.
  • Management Strategies:
    • Treatment varies based on the sodium levels:
      • Symptomatic hyponatremia is treated with hypertonic saline.
      • Hypernatremia requires fluid resuscitation.

Intestinal Catastrophe

  • Specific Conditions:
    • Malrotation with Midgut Volvulus: Twisting of the intestines that can obstruct blood flow.
    • Necrotizing Enterocolitis (NEC): Can occur in both full-term and preterm infants, involves inflammation and bacterial infection that can destroy bowel tissue.
    • Hirschsprung-associated Enterocolitis: Complication of Hirschsprung’s disease involving blockage and infection.
    • Intussusception: Older infants might only show altered mental status instead of the typical intermittent pain and lethargy.
  • Symptoms:
    • Common symptoms include bilious emesis (green vomit) or hematemesis (vomiting blood).
  • Emergency Response:
    • Urges early mobilization of pediatric surgery and radiology teams upon suspicion of these conditions.


  • Includes intentional or unintentional ingestion.
  • One pill killers include: calcium channel blockers (CCB), tricyclic antidepressants (TCA), opiates, sulfonylureas, Class 1 antiarrhythmics, antimalarials, camphor, oil of wintergreen.


  • The second ‘S’ in the mnemonic refers to seizures, which can be triggered by various conditions such as hypoglycemia, sepsis, inborn errors of metabolism, and trauma.
  • First-Line Treatment:
    • Actively seizing patients should initially be treated with benzodiazepines.
  • Second-Line Medications:
    • Includes fosphenytoin, phenobarbital, levetiracetam (Keppra), and valproic acid.
  • Management of Reversible Causes:
    • Urges prompt treatment of any identifiable causes like hypoglycemia or electrolyte imbalances.
  • Special Consideration:
    • Notes the possibility of pyridoxine-dependent epilepsy in neonates, recommending pyridoxine (vitamin B6) for intractable seizures unresponsive to multiple antiepileptic drugs (AEDs).


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