Perioperative Problems and Management in a 1-Year-Old with Hydrocephalus

1. Pathophysiology - Why Hydrocephalus Matters Perioperatively

• Cranial sutures may still be partially open (fontanelle may be closed or closing by 12-18 months), offering some compliance buffer - but this reserve is limited and unreliable at this age
• Communicating hydrocephalus (impaired arachnoid granulation absorption - most common after infection or haemorrhage) vs. non-communicating/obstructive (blocked ventricular outflow - aqueductal stenosis, posterior fossa tumour, congenital malformations)
• Raised ICP reduces cerebral perfusion pressure (CPP = MAP - ICP), threatening cerebral ischaemia
• Common causes in this age group: meningomyelocele + Chiari II malformation, neonatal intraventricular haemorrhage, congenital aqueductal stenosis, post-infectious, posterior fossa tumour

2. Preoperative Assessment

Clinical Features of Raised ICP in a 1-Year-Old

Investigations

• Full blood count, electrolytes, coagulation (especially if on anticonvulsants)
• Blood glucose (hypoglycaemia risk in infants)
• CT/MRI brain - ventricular size, aetiology, degree of mass effect
• Echocardiography if cardiac anomaly suspected (associated with some congenital syndromes)
• Assess for associated anomalies: meningomyelocele, Chiari malformation, chromosomal syndromes

Medications to Note

• Anticonvulsants (phenobarbitone, levetiracetam) - enzyme induction affects drug metabolism
• Steroids (dexamethasone) - if given pre-op to reduce oedema, causes adrenal suppression
• Acetazolamide (to reduce CSF production) - metabolic acidosis risk

3. Perioperative Problems

A. Airway and Full Stomach Risk

• Raised ICP causes vomiting, making the infant at risk of a full stomach and aspiration
• Increased head size may make positioning for intubation difficult - a shoulder roll helps align the axes (occiput is large, flexes the neck forward)
• Crying, struggling, and straining during induction sharply increase ICP - must be avoided

B. ICP Management During Induction - The Central Challenge

"The major concern is protection of the airway and control of intracranial pressure. Awake tracheal intubation, crying, struggling, and straining can increase intracranial pressure. A rapid-sequence induction of anesthesia to control the airway and intracranial pressure is preferred."

• Barash Clinical Anesthesia 9e

• If IV access present: propofol (2-3 mg/kg) + suxamethonium (RSI) OR propofol + rocuronium (modified RSI)
• If no IV access and patient is not stuporous: sevoflurane inhalational induction is empirically well-tolerated even with raised ICP in infants/children, especially if fontanelles are still compliant. Begin with controlled ventilation by bag-mask as quickly as possible, then establish IV access, administer muscle relaxant, and intubate under optimal conditions
• Avoid induction in a stuporous/near-herniation child by inhalation alone - use IV RSI
• Per Miller's Anesthesia 10e: "Despite the theoretical restraints, inhaled inductions using volatile anesthetics are empirically well tolerated, even in children with closed fontanelles."
• For children >6 months who are not obtunded, supplement with fentanyl (1-2 mcg/kg) for smooth emergence and analgesia
• Ketamine: historically avoided (increases CBF/CMRO2 and early studies showed ICP rise). However, more recent evidence in intubated patients shows minimal ICP increase. In a spontaneously breathing non-intubated child with raised ICP, ketamine remains best avoided. If used for sedation during imaging (non-intubated), weigh risk carefully

C. Aspiration Prophylaxis

• Sodium citrate (0.3M, 0.4 ml/kg orally) before induction
• Ranitidine or omeprazole preoperatively
• Modified RSI with cricoid pressure - though debate exists about cricoid force in infants

D. Haemodynamic Swings During VP Shunt Surgery

"Blood pressure may decrease abruptly when the ventricle is first cannulated (as brainstem pressure is relieved)... Burrowing the subcutaneous tunnel can produce a sudden painful stimulus, and a surge in blood pressure, which should be anticipated and treated preemptively."

• Anticipate hypotension at ventricular tap - have vasopressor (phenylephrine, dopamine) ready
• Anticipate hypertensive surge during tunnelling - deepen anaesthesia or give remifentanil

E. Positioning Problems

• Supine for most VP shunts
• Double-barrelled shunt (two proximal catheters - lateral ventricle + fourth ventricle) requires prone positioning for the posterior catheter - additional airway/ventilation considerations
• Large head - careful padding and positioning to avoid pressure sores and excessive neck flexion
• Lumboperitoneal shunt - lateral decubitus position

F. Ventilation Management

• Moderate hyperventilation (PaCO2 25-30 mmHg) is standard during anaesthesia for hydrocephalus to cause cerebral vasoconstriction and reduce ICP
• Agree target PaCO2 with surgeon at outset
• Use ETCO2 monitoring continuously; maintain ETCO2 35-38 mmHg intraoperatively unless ICP control requires lower (neurosurgeon guidance)
• Avoid hypoxia (SpO2 <95% causes cerebral vasodilation, worsens ICP)
• Avoid hypercapnia (every 1 mmHg rise in PaCO2 increases CBF by ~3%)

G. Anaesthetic Agent Selection

• Volatile agents (sevoflurane/isoflurane): safe for maintenance; at 1 MAC in children with open sutures, no significant ICP rise. Preferred if total IV anaesthesia not feasible
• Nitrous oxide: avoid - raises ICP and is generally not recommended in neurosurgery
• Propofol: reduces ICP and CMRO2 - preferred for TIVA, but avoid continuous infusion >4.5 mg/kg/h in children due to propofol infusion syndrome (lactic acidosis, lipidaemia, multiorgan failure, death)
• Opioids (fentanyl, morphine): safe; include fentanyl for smooth emergence (1-2 mcg/kg)
• Muscle relaxants: moderate relaxation helpful for the peritoneal limb of VP shunt; avoid succinylcholine in children with raised ICP if possible (fasciculations raise ICP transiently) - use rocuronium for modified RSI if time allows

4. Intraoperative Monitoring

• Invasive monitoring (arterial/CVP) generally not required for routine VP shunt - but have a low threshold if the child is critically unwell
• Head of bed elevation 15-30 degrees if feasible to aid venous drainage

5. Fluid Management

• Use isotonic crystalloids (0.9% NaCl or PlasmaLyte) - avoid hypotonic solutions (worsens cerebral oedema)
• Glucose-containing solutions only if hypoglycaemia documented - glucose excess causes osmotic diuresis and worsens cerebral oedema
• Maintenance: 4 ml/kg/hr for first 10 kg (Holliday-Segar); replace losses
• Maintain euvolaemia; avoid aggressive fluid loading
• Mannitol 0.25-0.5 g/kg IV over 20 min: used when acute ICP reduction needed intraoperatively (osmotic diuresis, reduces brain water). Requires adequate filling and urine output monitoring
• Hypertonic saline 3%: alternative to mannitol in paediatric ICP crisis - 2-5 ml/kg

6. Postoperative Problems and Management

A. Respiratory Complications

"Respiratory complications, including stridor, apnoea and bradycardia, cyanosis, and respiratory arrest, may develop after surgery in these infants with known brainstem abnormalities and potential disorders of central respiratory control."

• Patients with Chiari II malformation are at particular risk
• Post-op decision to extubate vs. keep intubated: if the child had pre-existing apnoea/bradycardia episodes, keep intubated until neurologically stable
• Otherwise, extubate awake when protective reflexes are fully recovered
• High-dependency or ICU setting for 1 year olds post-neurosurgery

B. Subdural Haematoma

• Small but significant risk after VP shunting due to bridging vein tearing from rapid brain shrinkage
• Post-shunt patients often nursed flat (not head-up) to prevent excessively rapid ventricular collapse
• Monitor for deteriorating consciousness, focal neurological signs

C. Electrolyte Disturbances

• Triphasic response after suprasellar surgery: SIADH → DI → SIADH

D. Seizures

• Pre-existing epilepsy is common with hydrocephalus
• Post-op seizures worsen cerebral oedema and ICP
• Continue anticonvulsants perioperatively (IV formulations if nil by mouth)
• If new seizure: lorazepam 0.1 mg/kg IV first line; levetiracetam 20 mg/kg IV; phenobarbitone 5-10 mg/kg IV

E. Shunt Malfunction / Underdrainage

• If shunt fails to function post-operatively: ICP rises again
• Signs: altered consciousness, Cushing's triad, sunset sign
• Needs urgent neurosurgical review

F. Hypothermia

• Infants have high surface-area to body-weight ratio
• Active warming: forced-air warming blanket, warm IV fluids, warm theatre
• Monitor temperature throughout

G. Pain Management

• VP shunt is associated with moderate post-op discomfort (tunnelling is painful)
• Paracetamol 15 mg/kg every 6 hours (oral or IV)
• Avoid NSAIDs in first 24h post-neurosurgery (antiplatelet effect, risk of haematoma)
• Low-dose morphine PCA not suitable at 1 year; nurse-controlled analgesia or regular paracetamol ± careful opioid PRN dosing

7. Summary: Key Anaesthetic Goals

• Miller's Anesthesia, 2-Volume Set, 10e - Chapters 53 (Paediatric Neurosurgery, Cerebrospinal Fluid Shunting Procedures, Paediatric VP Shunts), 31 (Ketamine, Propofol in paediatric neurology)
• Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e - Chapter 15 (Hydrocephalus in neonates and infants; Anaesthetic approach for shunts)