Pediatric and Neonatal Anesthesia Flashcards

A neonate born at 28 weeks gestation is scheduled for laser photocoagulation of retinopathy of prematurity at 36 weeks postmenstrual age. Which of the following best describes the risk of postoperative apnea and the recommended monitoring duration?

Answer: Risk persists until at least 60 weeks postmenstrual age; 12 hours of cardiorespiratory monitoring is required

Postoperative apnoea in ex-premature infants is strongly associated with postmenstrual age (PMA) and haematocrit. Current evidence-based guidelines recommend inpatient cardiorespiratory monitoring for at least 12 hours postoperatively in all ex-premature infants until 60 weeks PMA, as apnoeic events have been documented well beyond 44 weeks PMA, particularly in those with a history of significant prematurity. Regional anaesthesia reduces but does not eliminate the risk when supplemented with any sedation.

During inhalational induction in a 6-week-old neonate, severe laryngospasm develops. After 30 seconds of jaw thrust and CPAP without resolution, SpO₂ falls to 72%. Which is the most appropriate immediate pharmacological intervention?

Answer: Intravenous succinylcholine 2 mg/kg or intramuscular succinylcholine 4 mg/kg if IV access is absent

In life-threatening laryngospasm with failed CPAP/jaw thrust and rapidly falling SpO₂, succinylcholine remains the agent of choice due to its rapid onset (30–60 seconds IV). The neonatal/infant IV dose is 2 mg/kg (higher than adults due to larger volume of distribution). When IV access is absent, IM succinylcholine 4 mg/kg achieves adequate relaxation within 60–90 seconds. Rocuronium 1.2 mg/kg is an alternative if sugammadex is immediately available, but 0.6 mg/kg is insufficient for emergency intubating conditions. Propofol may worsen haemodynamic instability and has slower laryngeal relaxation.

A 3.2 kg term neonate with a large anterior mediastinal mass requires general anaesthesia for a diagnostic biopsy. CT shows >50% tracheal cross-sectional area compression. Which of the following pre-induction strategies is most appropriate?

Answer: Establish femoro-femoral cardiopulmonary bypass standby before induction, then use inhalational induction in a semi-upright position maintaining spontaneous ventilation

Anterior mediastinal masses with >50% tracheal compression in neonates carry extreme risk of complete airway and cardiovascular collapse on induction of general anaesthesia due to loss of negative intrathoracic pressure, muscle relaxation, and increased mediastinal pressure in the supine position. Pre-induction establishment of femoro-femoral (or ECMO) bypass standby is the safest approach when the mass is deemed high-risk. Induction should maintain spontaneous ventilation (inhalational preferred) with the patient in a semi-upright or lateral position. Awake fibreoptic intubation in a term neonate is technically extremely challenging. Rigid bronchoscopy requires general anaesthesia and does not address the cardiovascular component of collapse.

In a 2.5 kg neonate undergoing repair of oesophageal atresia with tracheo-oesophageal fistula (Gross type C), single-lung ventilation of the left lung is required. SpO₂ drops to 78% despite FiO₂ 1.0 and PEEP 5 cmH₂O. Which manoeuvre is most likely to improve oxygenation while maintaining the surgical field?

Answer: Apply 5 cmH₂O CPAP to the non-dependent (right) lung via the fistula orifice

In neonatal one-lung ventilation for TOF repair, the non-ventilated right lung causes significant intrapulmonary shunting. Applying low CPAP (5 cmH₂O) to the collapsed right lung via a separate catheter passed beyond the fistula maintains some alveolar oxygen delivery and reduces shunt fraction without fully reinflating the lung and obstructing the surgical view. This technique is well described and effective in the paediatric thoracic literature. High tidal volumes risk volutrauma to the single ventilated lung. Intermittent bilateral ventilation repeatedly disrupts surgery. HFOV is not easily portable to this specific rescue scenario in real-time.

A 4-month-old, 5.5 kg infant with unrepaired Tetralogy of Fallot develops a hypercyanotic ('Tet') spell with SpO₂ falling to 58% during awake peripheral IV cannulation. The infant is crying vigorously. Which sequence of interventions is most appropriate?

Answer: Knee-chest position → oxygen → IV propranolol 0.1 mg/kg → IV sodium bicarbonate if acidosis confirmed

A hypercyanotic spell in ToF is a medical emergency driven by dynamic RVOTO spasm, reduced SVR, and a vicious cycle of hypoxia → acidosis → further spasm. First-line: knee-chest position (increases SVR and venous return), oxygen (pulmonary vasodilation, calming). IV propranolol 0.01–0.1 mg/kg IV slows HR and relieves RVOTO spasm. Sodium bicarbonate corrects metabolic acidosis that worsens spasm. Phenylephrine (pure alpha agonist) is a second-line agent to raise SVR, not first-line. Ketamine is useful for sedation before cannulation but not for acute spell management. Atropine is contraindicated as it worsens tachycardia and spasm.

Which of the following most accurately describes the pharmacokinetic basis for using a lower MAC of volatile anaesthetic agents in preterm neonates compared with term neonates aged 1–6 months?

Answer: Lower MAC in preterms reflects reduced neuronal density and synaptic connectivity, combined with higher CNS progesterone and neurosteroid concentrations that potentiate GABA-A activity

MAC in preterm neonates is lower than in term neonates or older infants (where MAC peaks around 1–6 months). The mechanisms are multifactorial but primarily neurological: preterm brains have reduced synaptic density and less mature neural circuitry requiring lower anaesthetic concentrations for equivalent effect. Crucially, elevated endogenous neurosteroids (allopregnanolone and related progesterone metabolites, which are high in late foetal/preterm life due to placental transfer) act as potent positive allosteric modulators of GABA-A receptors, reducing the exogenous anaesthetic requirement. Cardiac output is actually relatively higher per kg in neonates (not lower), which would slow equilibration. Plasma protein binding is lower in preterms (not higher), increasing free drug.