Category Archives: Pediatrics

Apnoea of prematurity

6 Well Known Step Pathogenesis of Apnea of Prematurity Based on Nelson and Clohery to Clear Your Concept

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Apnea of prematurity (AOP) is a common condition where infants born before 37 weeks gestation experience breathing pauses lasting 15-20 seconds or more, often accompanied by slow heart rates (bradycardia) or low oxygen levels. It stems from an immature central nervous system and usually resolves on its own by 37–40 weeks postmenstrual age. Based on Cloherty and Stark’s Manual of Neonatal Care (9th Edition) and relevant pediatric algorithms and Nelson’s, here is a comprehensive summary of Apnea of Prematurity (AOP).

1. Definition and Classification

  • Definition: Apnea is the cessation of airflow. It is considered pathologic (an apneic spell) when:
    • Absence of airflow lasts 20 seconds or longer.
    • It is shorter than 20 seconds but accompanied by bradycardia (heart rate < 100 bpm) or hypoxemia (cyanosis or $SpO_2$ < 85–80%).
  • Classification:
    • Central: Total absence of inspiratory efforts (no diaphragmatic activity).
    • Obstructive: Inspiratory efforts persist, but airflow is blocked, usually at the pharyngeal level.
    • Mixed: A combination where airway obstruction precedes or follows central apnea. Most spells in preterm infants are mixed.

2. Incidence, Onset, and Duration

  • Incidence: Inversely related to gestational age (GA). It occurs in essentially all infants < 28 weeks’ GA and about 25% of those < 34 weeks’ GA.
  • Onset: Typically begins 1 to 2 days after birth. If spells do not occur within the first 7 days, AOP is unlikely to develop later unless triggered by other factors.
  • Duration: Usually ceases by 36 to 37 weeks’ postmenstrual age (PMA) in infants born at $\ge 28$ weeks, but frequently persists beyond term for those born more prematurely.

3. Pathogenesis (Underlying Mechanisms)

  • Developmental Immaturity: The primary cause is an immature central respiratory drive in the brainstem.
  • Sleep State: Spells are more frequent during active (REM) sleep, which is the predominant sleep state in preterms and is characterized by irregular breathing.
  • Chemoreceptor Response: Preterm infants have a decreased ventilatory response to increased $CO_2$ and may respond to hypoxia with hypoventilation rather than sustained hyperventilation.
  • Reflexes: Apnea can be triggered by stimulation of the posterior pharynx (e.g., vigorous suctioning), lung inflation, or fluid in the larynx.
  • Airway Mechanics: Poor muscle tone can lead to airway obstruction, especially during neck flexion or if there is nasal obstruction.
  • Note on GER: While gastroesophageal reflux is common in preterms, studies have not demonstrated an association between GER and AOP frequency.

4. Differential Diagnosis (Evaluation)

Apnea in a term infant or a “sick” preterm infant is always abnormal and requires looking for secondary causes:

  • Infection: Sepsis, meningitis, or necrotizing enterocolitis.
  • Metabolic Disorders: Hypoglycemia, hypocalcemia, or electrolyte imbalances (hyponatremia).
  • Neurologic: Intracranial hemorrhage (IVH), seizures, or birth asphyxia.
  • Impaired Oxygenation: PDA (Patent Ductus Arteriosus), anemia, or pneumonia.
  • Drugs: Maternal medications (magnesium, narcotics) or drug toxicity (e.g., phenobarbitone).

5. Management and Treatment

  • Monitoring: All infants < 35 weeks’ GA should be monitored for at least the first week. Monitor heart rate and $SpO_2$ in addition to respiration.
  • Immediate Action: Respond to the infant, not the monitor alarm. Most spells respond to tactile stimulation. If the infant is unresponsive, use bag-and-mask ventilation.
  • Positioning: Avoid extreme neck flexion or extension. Prone positioning may reduce apnea by stabilizing the chest wall.
  • Pharmacotherapy (Methylxanthines):
    • Caffeine Citrate: The drug of choice due to its long half-life (once-daily dosing), high therapeutic index, and lack of need for routine level monitoring.
    • Dosing: Loading dose of 20 mg/kg (10 mg/kg caffeine base), followed by a maintenance dose of 5–10 mg/kg daily.
    • Benefits: Reduces spells, the need for mechanical ventilation, and the risk of Bronchopulmonary Dysplasia (BPD).
  • Respiratory Support:
    • nCPAP (4–6 $cm H_2O$): Reduces mixed and obstructive spells by maintaining end-expiratory lung volume.
    • NIPPV: May be attempted if CPAP fails.
  • Other Considerations:
    • Blood Transfusion: May be considered if the hematocrit is < 25–30% and spells are frequent despite caffeine.
    • GER Treatment: Pharmacologic treatment of reflux (e.g., H2 blockers) is not recommended to treat AOP and may be harmful.

6. Discharge and Follow-up

  • Discharge Criteria: Infants should be free of significant apnea for 5 to 7 days after stopping caffeine.
  • Caffeine Offset: Because caffeine effects remain for up to a week, the “countdown” to discharge typically starts several days after the last dose.
  • Recurrence: Recurrent apnea can be triggered by viral illness, anesthesia, eye examinations, or immunizations. These infants should be monitored closely until at least 44 weeks’ PMA.
  • SIDS: A history of AOP does not increase the risk of Sudden Infant Death Syndrome (SIDS).

Top 5 Facts about Gower’s Sign: How to easily demonstrate Gower’s sign?

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Gowers’ sign is a medical sign that indicates weakness in the pelvic girdle and proximal lower limb muscles. It’s characterized by a patient using their hands to “walk” up their body to get to a standing position. 

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How is Gower’s Sign Performed?

  1. Start in a supine or sitting position
  2. Roll onto your stomach with your arms and legs extended
  3. Put your hands on the ground and shift your weight onto your extended arms
  4. Push your body backward to extend your legs
  5. Put your hands on your knees
  6. Walk your hands up your thighs until you’re standing

What it can indicate

  • Duchenne muscular dystrophy: A characteristic sign of this condition 
  • Guillain-Barré syndrome (GBS): Can be a sign of recovery from GBS 
  • Pelvic girdle weakness: A sign of weakness in the pelvic girdle and proximal lower extremity muscles 
  • Diskitis: Can be associated with diskitis at the L4-5 intervertebral space 

Who described it?

Gowers’ sign was described by neurologist Sir William Richard Gowers in 1879. 

Now lets dig into DMD.

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Duchenne Muscular Dystrophy (DMD)

Duchenne Muscular Dystrophy (DMD) is the most common and severe form of progressive muscular dystrophy in children. It belongs to a group of primary myopathies characterized by a progressive, genetic-based degeneration and death of muscle fibers.

1. Genetic Profile and Pathogenesis

  • Inheritance: DMD is an X-linked recessive disorder, almost exclusively affecting males and carried by females. Approximately one-third of cases result from de novo (new) mutations.
  • Molecular Defect: It is caused by a mutation (typically a deletion) in the gene for dystrophin located on chromosome Xp21.
  • Mechanism: Dystrophin is the longest known human gene and encodes a protein that connects the muscle fiber cytoskeleton to the surrounding extracellular matrix. Without functional dystrophin, muscle cells undergo chronic damage, necrosis, and replacement by fat and fibrous tissue.

2. Clinical Features

DMD typically presents between the ages of 2 and 5 years.

  • Early Signs: Delayed motor milestones (especially late walking) and mild speech or language delay are often the first indicators.
  • Muscle Weakness: Progressive, symmetric weakness begins in the pelvis and hip girdle, later involving the shoulder girdle.
  • Gait and Mobility: Affected children exhibit a waddling (Trendelenburg) gait, frequent falls, and difficulty climbing stairs (mounting them “one by one”).
  • Gower Sign: A classic clinical finding where the child, unable to stand up normally from the floor, must turn prone and “climb up his own thighs” with his hands to reach an upright position.
  • Pseudohypertrophy: Striking enlargement of the calf muscles occurs because muscle tissue is replaced by fat and connective tissue rather than true muscle growth.
  • Intellectual Function: Approximately 20% to 30% of boys have learning difficulties or non-progressive intellectual impairment.

3. Diagnostic Evaluation

Diagnosis should be initiated at the first clinical suspicion.

  • Serum Creatine Kinase (CK): Remarkably high levels (usually 10 to 40 times normal) are a hallmark of the disease.
  • Genetic Testing: Direct dystrophin gene testing is now the preferred definitive method and often avoids the need for a muscle biopsy.
  • Electromyography (EMG): Shows a “myopathic” pattern, including reduced amplitude and duration of motor unit potentials.
  • Muscle Biopsy: If performed, shows fiber necrosis, phagocytosis, and increased endomysial fat and connective tissue.

4. Progression and Complications

  • Loss of Ambulation: Most boys become wheelchair-bound by age 10 to 13.
  • Orthopedic: As weakness progresses, many develop scoliosis, particularly once they are no longer walking.
  • Cardiac: Progressive cardiomyopathy and persistent tachycardia develop in nearly all patients.
  • Respiratory: Weakness of the diaphragm and intercostal muscles leads to nocturnal hypoxia and eventual respiratory failure.
  • Prognosis: Death typically occurs in the late teens or 20s from cardiorespiratory complications.

5. Management

Management requires a specialist multidisciplinary team.

  • Corticosteroids: (e.g., Prednisone or Deflazacort) are the mainstay of treatment, as they preserve mobility, improve muscle strength, and prevent scoliosis.
  • Supportive Care: Physiotherapy and splinting are used to prevent contractures. Nocturnal hypoxia may be managed with overnight CPAP.
  • Novel Therapies: Research into exon-skipping drugs (e.g., Ataluren or Eteplirsen) allows for the production of small amounts of functional dystrophin in patients with specific mutations.
  • Genetic Counseling: Crucial for the family to detect female carriers and discuss antenatal diagnosis.

DMD vs. Becker Muscular Dystrophy (BMD): BMD is a milder allelic variant where some functional dystrophin is produced. BMD features a later onset (average 11 years), a slower course, and patients typically remain ambulatory into their late 20s or beyond, with many living into middle age.

Who described Gower’s sign?

Sir William Richard Gowers

What can Gower’s Sign indicate?

Duchenne muscular dystrophy, Guillain-Barré syndrome (GBS), pelvic girdle weakness, and diskitis.