📊 Chapter 144: Intracranial Pressure Monitoring

Indications (severe TBI, Reye syndrome, encephalitis) · CPP (MAP-ICP) · EVD (gold standard, therapeutic) · Intraparenchymal probes (Codman, Camino) · Drift · Normal ICP (<20 mmHg) · Treatment thresholds · Lundberg waves

🔍 Core Concepts: ICP Monitoring

📌 Indications (severe TBI)
GCS 3-8 after resuscitation + abnormal CT (haematoma, contusion, swelling). Normal CT + 2 of: age >40 (adult), motor posturing, hypotension. Also indicated for Reye syndrome, acute liver failure, encephalitis.
🧠 CPP = MAP - ICP
Target CPP >40 mmHg (infants) to >60 mmHg (adolescents). CPP <40 associated with cerebral ischaemia.
💧 EVD (External Ventricular Drain)
Gold standard (accurate, allows CSF drainage). Site: Kocher's point (10.5 cm back from nasion, 3 cm lateral). Zero at foramen of Monro (tragus).
🪢 Intraparenchymal probes (Codman, Camino)
Strain-gauge or fibre-optic. Advantages: no patent ventricles needed, lower infection. Disadvantage: cannot drain CSF, drift (error over time), expensive.
📊 Normal ICP & thresholds
Normal: <10-15 mmHg (infants), <20 mmHg (older children). Treatment threshold: >20-25 mmHg. Sustained >40 mmHg predicts poor outcome.
⚠️ Complications
EVD: infection (ventriculitis), haemorrhage (0.8-1%), malposition, obstruction. Intraparenchymal: drift (1-4 mmHg over days), breakage, lower infection.
📈 Lundberg waves
A waves (plateau, >50 mmHg for 5-20 min, pathological). B waves (oscillations 0.5-2/min, vasogenic). C waves (normal variations).

🩺 Stepwise ICP Monitoring & Management

1
Indications for ICP monitor
Severe TBI (GCS 3-8) with abnormal CT, or normal CT with hypotension/motor posturing. Also indicated in acute liver failure, Reye syndrome, encephalitis.
2
Choose monitor type
EVD (gold standard, allows CSF drainage). Intraparenchymal probe (if ventricles small, coagulopathy – lower infection).
3
Insertion & zeroing
Kocher's point (10.5 cm back from nasion, 3 cm lateral). For EVD, zero transducer at tragus (foramen of Monro). Intraparenchymal probes zeroed before insertion.
4
Monitor & treat elevated ICP
Target CPP >40-60 mmHg. First-tier: head of bed 30°, sedation, normothermia, mannitol/hypertonic saline, mild hyperventilation (PaCO2 30-35). Second-tier: barbiturates, hypothermia, decompressive craniectomy.
5
EVD management
Drain CSF if ICP >20-25 mmHg. Monitor for infection (daily CSF cultures if suspected). Wean EVD before removal (raise drain height, clamp).