Prematurity

Surgical approach (context-dependent: prematurity is not an operation)

• Common prematurity-related operations encountered by anaesthetists
  • Inguinal herniotomy (± orchidopexy if older): open or laparoscopic; reduce hernia sac, high ligation; day-case vs overnight depending on post-conceptual age and comorbidity
  • PDA ligation/closure: surgical clip/ligation via thoracotomy (less common now) or catheter closure (interventional cardiology)
  • NEC laparotomy: resection of necrotic bowel, stoma formation, peritoneal drainage (very unstable physiology)
  • ROP treatment: laser photocoagulation or intravitreal anti-VEGF; often requires immobility and airway control
  • VP shunt for post-haemorrhagic hydrocephalus; airway and temperature critical

Anaesthetic management (typical patterns for ex-premature infants)

• Type of anaesthesia
  • Often GA for airway control/immobility; consider regional (spinal/caudal) for lower abdominal surgery (e.g., herniotomy) to reduce postoperative apnoea risk in selected infants
  • Avoid deep sedation without secured airway for painful procedures due to apnoea/obstruction risk
• Airway device
  • ETT commonly preferred in ex-premature infants (reflux/aspiration risk, need for controlled ventilation, prolonged procedures, ROP laser, NEC, PDA)
  • SGA may be acceptable for brief, non-intraabdominal procedures in stable larger infants; be cautious with high airway pressures/BPD
• Duration (varies with procedure)
  • Herniotomy ~30–60 min; ROP laser ~45–120 min; PDA closure ~60–120 min; NEC laparotomy often >2 h
• Painfulness
  • Herniotomy: moderate; ROP laser: painful/stressful; PDA thoracotomy: severe; NEC laparotomy: severe
  • Use multimodal analgesia; consider regional techniques (caudal/ilioinguinal blocks, paravertebral/epidural for thoracotomy where appropriate expertise/resources)
• Overarching priorities
  • Prevent apnoea/bradycardia, maintain temperature, glucose and electrolytes, avoid volutrauma/barotrauma, minimise oxygen toxicity, and plan postoperative monitoring

Definitions and epidemiology

• Prematurity: birth <37 weeks gestational age (GA).
• Extremely preterm <28 weeks; very preterm 28–31+6; moderate 32–33+6; late preterm 34–36+6.
• Perioperative risk relates to current age, postmenstrual age (PMA = GA at birth + chronological age), weight, comorbidities (esp BPD), and anaemia.

Why prematurity matters to anaesthesia (high-yield physiology)

• Respiratory: low FRC, high closing volume, compliant chest wall → rapid desaturation; immature central control → apnoea; surfactant deficiency history; BPD/CLD common.
  • Higher oxygen consumption per kg and limited reserve; atelectasis risk under GA
  • BPD: air-trapping, CO2 retention, pulmonary hypertension; sensitive to high airway pressures and high FiO2
• Cardiovascular: transitional circulation issues (PDA/PFO), limited ability to increase stroke volume → cardiac output is rate-dependent; labile BP; pulmonary hypertension risk.
  • Bradycardia with hypoxia, vagal stimulation, or apnoea; treat cause first (oxygenation/ventilation)
• Thermoregulation: large surface area:mass, thin skin, little brown fat → rapid heat loss; hypothermia worsens acidosis, coagulopathy, apnoea.
• Metabolic: limited glycogen stores → hypoglycaemia; immature renal handling → electrolyte disturbances; higher risk of hyponatraemia with hypotonic fluids.
  • Use isotonic maintenance fluids; monitor glucose and electrolytes in longer cases/ill infants
• Haematology: anaemia common; anaemia increases postoperative apnoea risk; coagulation immaturity in very preterm.
• Neurology: vulnerable to IVH/periventricular leukomalacia; avoid extremes of PaCO2 (hypocapnia reduces cerebral blood flow; hypercapnia increases ICP and pulmonary vasoconstriction).
• Drug handling: reduced protein binding, immature hepatic metabolism and renal clearance → prolonged drug effects; increased sensitivity to volatiles/opioids; careful titration.

Key perioperative complication: postoperative apnoea (FRCA core topic)

• Definition: cessation of breathing ≥20 s, or shorter pause associated with bradycardia/desaturation/cyanosis; may be central, obstructive, or mixed.
• Risk factors: low PMA, low birth GA, history of apnoea, BPD, anaemia, sepsis, hypothermia, hypoglycaemia, opioids/sedatives, ongoing oxygen requirement.
• Timing: risk highest in first 12 h but can occur up to 24 h post-op; monitor accordingly.
• PMA thresholds (pragmatic exam-friendly): significant apnoea risk persists until ~50–60 weeks PMA; many units admit for overnight monitoring if <60 weeks PMA, or <50–55 weeks if completely well and non-anaemic (local policy varies).
  • Anaemia increases risk: consider Hb check; treat/optimise if low (thresholds vary; Hb <10 g/dL often cited as higher risk, especially in younger PMA).
• Prevention/mitigation: maintain normothermia, normoglycaemia, avoid excessive opioids, consider regional techniques, ensure adequate postoperative monitoring (apnoea/bradycardia alarms).
• Caffeine: methylxanthine respiratory stimulant; may reduce apnoea in high-risk infants (e.g., caffeine citrate 10 mg/kg loading then 5 mg/kg/day—local protocols). Consider in consultation with neonatology.

Preoperative assessment (what to actively seek)

• Gestational age at birth, chronological age, and PMA; current weight and growth trajectory.
• Respiratory history: BPD/CLD, baseline SpO2, home oxygen, recent apnoea/bradycardia, recent URTI, ventilation history, pulmonary hypertension, diuretics/bronchodilators.
• Cardiac: PDA status, echo findings (PHTN), murmurs, heart failure signs; current meds (e.g., diuretics).
• Neurology: IVH history, seizures, hydrocephalus/shunt; baseline tone and feeding.
• Haematology: Hb/haematocrit; transfusion history; consider Hb particularly if PMA <60 weeks or symptoms.
• Airway: small mandible, limited reserve; previous intubation difficulty; subglottic stenosis risk after prolonged ventilation.
• Fasting and fluids: avoid prolonged fasting; consider IV dextrose-containing isotonic fluids for small infants if prolonged fast/ill; check glucose perioperatively.
• Planning: postoperative destination (ward/HDU/NICU), monitoring duration, and whether surgery should occur in a paediatric centre with neonatal support.

Intraoperative management (practical FRCA approach)

• Environment/monitoring: warm theatre, forced-air warmer, warmed fluids, hat/occlusive wrap; standard monitoring plus temperature; consider pre-ductal SpO2 in PHTN.
• Induction: avoid hypoxia/bradycardia; gentle airway manipulation; consider atropine in high vagal tone/bradycardia-prone infants (local practice).
• Airway: appropriately sized ETT (uncuffed/cuffed microcuff depending on size/unit); confirm depth carefully; secure well; avoid repeated attempts.
• Ventilation: lung-protective strategy; avoid high pressures; use PEEP to prevent atelectasis; target normocapnia; cautious oxygen—titrate to saturations appropriate for the child’s baseline/condition.
  • BPD/PHTN: avoid hypoxia, hypercapnia, acidosis, hypothermia, pain (all increase PVR); consider iNO/vasodilators only with specialist support
• Fluids: isotonic crystalloid; avoid hypotonic solutions; glucose monitoring (especially small/long cases); careful volume to avoid PDA/PHTN decompensation.
• Analgesia: paracetamol (weight-based), regional blocks where appropriate; opioid-sparing approach; if opioids used, titrate carefully and plan monitoring.
• Regional anaesthesia: spinal (e.g., herniotomy) can reduce early apnoea risk but does not eliminate need for monitoring; may fail; avoid high block causing apnoea; ensure resuscitation readiness.
• Emergence: extubate fully awake if appropriate; ensure normothermia and adequate ventilation; consider postoperative CPAP/HFNC for BPD or if baseline support.

Postoperative care

• Monitoring: continuous SpO2 and apnoea/bradycardia monitoring for at-risk infants (often overnight); ensure staff trained to respond.
• Apnoea management: stimulate, airway reposition, oxygen; treat hypothermia/hypoglycaemia; consider CPAP; escalate to ventilation if recurrent/prolonged.
• Analgesia: regular paracetamol; cautious opioids; consider regional top-ups if catheter techniques used; avoid oversedation.
• Feeding: early enteral feeds when safe; minimise fasting; coordinate with neonates/paeds surgery.

Prematurity-associated comorbidities relevant to anaesthesia (quick list)

• BPD/CLD ± pulmonary hypertension; PDA; recurrent apnoea of prematurity; GERD/aspiration; IVH and hydrocephalus; NEC/short gut; ROP; anaemia of prematurity; sepsis risk.

FRCA exam angles (what commonly gets asked)

• Explain postoperative apnoea in the ex-premature infant: risk factors, PMA thresholds, monitoring duration, and prevention strategies.
• Anaesthetic technique for inguinal hernia repair in an ex-premature infant: GA vs spinal, airway choice, analgesia, and postoperative disposition.
• Discuss anaesthesia for ROP laser: airway, oxygen strategy, analgesia, and postoperative apnoea risk.
• Physiological differences in preterm infants relevant to anaesthesia (respiratory control, thermoregulation, pharmacology).