Perioperative Problems and Anaesthetic Management of Hydrocephalus in a 1-Year-Old

1. Understanding the Condition

• Congenital: aqueductal stenosis, Arnold-Chiari malformation, myelomeningocele, arachnoid cysts
• Acquired: post-meningitis, post-intraventricular hemorrhage, posterior fossa tumors

2. Preoperative Problems and Assessment

A. Raised ICP - Cardinal Clinical Features

B. Airway Problems

• Macrocephaly makes the head heavy and unstable - the occiput protrudes, making the neck flex forward, which can cause airway obstruction
• Optimal laryngoscopy position requires ramping (folded blanket under shoulders) to compensate
• Atlantoaxial instability may coexist in syndromic cases (Chiari, Down syndrome)
• Distorted skull anatomy may limit positioning

C. Respiratory Problems

• Chiari malformation (common association) can cause central apnea, stridor, and impaired airway reflexes
• Prematurity-related chronic lung disease may be present
• Vomiting from raised ICP poses aspiration risk - consider full-stomach precautions

D. CNS and Neurological Co-morbidities

• Epilepsy is common - anticonvulsant medications must be continued perioperatively
• Cerebral palsy may coexist
• Assess for signs of neurological deterioration, baseline GCS equivalent (AVPU in infants)

E. Hematological / Metabolic

• Check Hb, coagulation (especially if recent shunt infection or sepsis)
• In the acutely unwell child: electrolytes, blood glucose (hypoglycemia risk in infants)
• Medications: acetazolamide, furosemide (used to reduce CSF production medically) - may cause electrolyte imbalance and metabolic alkalosis

F. Associated Congenital Anomalies

• Neural tube defects (myelomeningocele) may mean a prone position has been used previously and skin breakdown is possible
• Congenital heart disease may coexist (syndromic cases - Trisomy 21, VACTERL)
• Echocardiogram if relevant

3. Preoperative Optimization

• Continue anticonvulsants right up to surgery
• IV access early if acutely unwell; check electrolytes
• NBM guidelines: 2 hours clear fluids, 4 hours breast milk, 6 hours formula/solids (ESRA/RCOA)
• If vomiting is severe, nasogastric tube and consider sodium citrate/ranitidine for aspiration prophylaxis
• PICU/HDU bed booked postoperatively for high-risk cases
• Blood group and save; crossmatch if revision surgery or large head

4. Intraoperative Management

A. Monitoring

• Standard: pulse oximetry, ECG, NIBP (cycle every 2 min during induction), capnography (EtCO₂ - critical for ICP management), temperature probe
• Consider: invasive arterial line if ICP is severely elevated, hemodynamically compromised, or if prolonged surgery
• Peripheral IV access is usually adequate for most VP shunts
• Urinary catheter for lengthy procedures
• Neuromuscular monitoring if muscle relaxants used

B. Premedication

• Use with caution: midazolam (0.3-0.5 mg/kg oral) may help reduce anxiety/ICP rise from struggling
• Risk vs. benefit: oversedation causes hypoventilation → hypercarbia → raised ICP; anxiety also raises ICP
• Atropine (0.02 mg/kg IV/IM) - especially in neonates/infants for vagolytic effect and to reduce secretions

C. Induction

• Thiopentone 3-5 mg/kg or propofol 2-3 mg/kg (both reduce CMRO₂ and ICP)
• Thiopentone is preferred if herniation is imminent - potent ICP reduction
• Fentanyl 1-2 mcg/kg to blunt laryngoscopy response
• Suxamethonium 2 mg/kg (RSI if full stomach) - brief ICP rise is acceptable; use only if aspiration risk is high
• Rocuronium 1.2 mg/kg (modified RSI) with sugammadex available for reversal

• Sevoflurane in 100% O₂ - provides good cardiovascular stability, smooth induction
• Sevoflurane is preferred over halothane or isoflurane as it causes less cerebral vasodilation at lower concentrations
• Transition to IV TIVA or maintain with sevoflurane ≤1 MAC

• Preoxygenate well
• Secure airway with cuffed RAE tube (oral or nasal) - size 4.0-4.5 for a 1-year-old
• Avoid coughing/bucking at intubation (raises ICP acutely) - use adequate depth and lidocaine 1.5 mg/kg IV pre-laryngoscopy
• Confirm position with EtCO₂ waveform and bilateral chest auscultation
• Fix tube securely - repositioning mid-procedure is common for VP shunts

D. Positioning

• Supine with slight head-up tilt (15-20°) to facilitate venous drainage and reduce ICP
• Head turned to the side (usually left) for burr hole placement - support neck carefully, avoid excessive rotation which impairs jugular venous drainage
• Head and neck positioning: use a ring/doughnut head support to stabilize the large, heavy head
• Ramping during laryngoscopy if macrocephalic

E. Maintenance

1. Prevent further ICP rise
2. Maintain cerebral perfusion pressure (CPP = MAP - ICP); target CPP >40-50 mmHg in a 1-year-old
3. Avoid hypoxia (SaO₂ >95%)
4. Avoid hypercapnia (EtCO₂ 35-40 mmHg); mild hyperventilation (EtCO₂ 30-35 mmHg) may be used as a short-term bridge if ICP is critically high, but avoid sustained hypocapnia (causes cerebral vasoconstriction and ischemia)
5. Maintain normothermia (temperature management is critical - large exposed surface area during tunneling of shunt)

• TIVA with propofol + remifentanil or propofol + fentanyl infusion: reduces CMRO₂ and ICP; preferred for raised ICP
• Sevoflurane ≤1 MAC (with minimal N₂O or avoid N₂O): acceptable if ICP controlled; at >1.5 MAC, inhalational agents cause cerebral vasodilation
• Nitrous oxide - generally avoided in neurosurgery; causes cerebral vasodilation and may expand pneumocephalus
• Muscle relaxation: atracurium or vecuronium infusion - facilitates controlled ventilation; use nerve stimulator

• Isotonic crystalloid (normal saline 0.9% or Plasmalyte/Hartmann's) - avoid hypotonic solutions (dextrose-saline, 0.18% NaCl) as they worsen cerebral edema
• Maintenance: ~4 mL/kg/hr for first 10 kg; replace blood loss ml:ml with colloid/blood
• Blood glucose monitoring: 1-year-olds are vulnerable to hypoglycemia; provide glucose-containing solution (e.g., dextrose 5% in normal saline) as separate infusion if required
• Blood transfusion trigger: Hb <7-8 g/dL (lower in healthy child; higher if ICP critically elevated)

• Scalp infiltration with local anesthetic (lidocaine with adrenaline 1:200,000) by surgeon - reduces intraoperative opioid requirement
• Paracetamol 15 mg/kg IV intraoperatively
• Fentanyl 1-2 mcg/kg boluses as needed
• NSAIDs (ibuprofen, ketorolac) - may be given postoperatively if no contraindication; avoid if intracranial bleeding is a risk
• Morphine 0.05-0.1 mg/kg can cause nausea and respiratory depression, which raises ICP - use cautiously

• Ondansetron 0.1 mg/kg IV at end of surgery - reduces postoperative vomiting (which raises ICP)

• Institutional shunt infection prevention protocol (commonly cefuroxime or cefazolin at induction)

F. Ventilation

• Controlled mechanical ventilation throughout
• Target EtCO₂ 35-40 mmHg (normocapnia)
• Avoid PEEP >5 cmH₂O (impairs venous drainage, raises ICP)
• Tidal volume 6-8 mL/kg; RR adjusted for age (~25-30 breaths/min in a 1-year-old)

5. Specific Intraoperative Hazards

6. Postoperative Management

A. Extubation

• Extubate awake in lateral/sitting position to minimize aspiration risk
• Avoid bucking/coughing at extubation - lignocaine 1.5 mg/kg IV prior, or use remifentanil wash-out technique
• Ensure full reversal of neuromuscular blockade: neostigmine 50 mcg/kg + atropine 25 mcg/kg (or glycopyrrolate 10 mcg/kg)

B. Postoperative Monitoring

• PACU minimum 2 hours; consider HDU/PICU if:
  • Preoperative raised ICP
  • Compromised airway (Chiari, macrocephaly)
  • Neonatal/premature equivalent age <60 weeks post-conceptual age (apnea monitoring for 12-24 hours)
  • Cardiovascular instability intraoperatively
• Neurological observations every 15-30 min (pupil size, GCS equivalent, limb movement)
• Monitor for signs of shunt over-drainage (headache on sitting, subdural hematoma)
• Monitor for shunt blockage - recurrence of ICP signs
• SIADH: monitor serum Na postoperatively (occurs 24-48 h post-surgery); restrict free water
• Monitor blood glucose frequently in infants

C. Postoperative Analgesia

• Regular paracetamol 15 mg/kg q4-6h (oral or IV)
• NSAIDs (ibuprofen 5-10 mg/kg q6-8h) if no contraindication
• Avoid morphine infusions unless closely monitored (respiratory depression → hypercarbia → raised ICP)

D. Post-op Complications to Watch For

• Shunt infection (fever, meningism, wound erythema) - most common cause of morbidity
• Shunt over-drainage - slit-ventricle syndrome, orthostatic headache, subdural hematoma
• Seizures - treat with IV lorazepam 0.1 mg/kg, maintain anticonvulsants
• Pneumocephalus - may worsen ICP transiently
• Apnea (especially in infants with Chiari or premature background)

7. Special Considerations for a 1-Year-Old

• Open fontanelle/cranial sutures allow some ICP buffering but are closing; the safety margin is less than in neonates
• Blood volume is small (~80 mL/kg = ~8-9 mL/kg × weight); even 20-30 mL blood loss is significant
• Temperature regulation is immature - active warming is mandatory
• Pharmacokinetics differ from adults: higher volume of distribution for most drugs, relatively immature hepatic/renal drug clearance
• Inhalational agents and prolonged anesthesia in infants have raised concerns about neurotoxicity (FDA warning >3 hours or multiple exposures); minimize total anesthetic time where possible
• For programmable VP shunts: MRI will need to be performed postoperatively to re-check and reset the valve pressure settings

Summary Table - Anaesthetic Goals