ICU · neurocritical-care

ICP Monitoring and Multimodal Neuromonitoring — Comprehensive ICU Management

Also known as Intracranial pressure monitoring · ICP monitor · External ventricular drain · EVD · Intraparenchymal bolt · Codman probe · Camino probe · Cerebral perfusion pressure · CPP · Brain tissue oxygen · PbtO2 · LICOX · Cerebral microdialysis · Jugular venous bulb oximetry · SjvO2 · Multimodality neuromonitoring · Monroe-Kellie doctrine · ICP waveform · Percussion wave · Tidal wave

Intracranial pressure (ICP) monitoring is the cornerstone of neurocritical care for severe traumatic brain injury (TBI) and other intracranial hypertension states. The MONROE-KELLIE DOCTRINE governs the rigid vault: volume = brain (80%) + blood (10%) + CSF (10%) — an increase in one component MUST be offset by a decrease in another, or ICP rises. Normal ICP is 5-15 mmHg (recumbent). INTRACRANIAL HYPERTENSION (ICH) = ICP 22 mmHg (BTF 4th edition treatment threshold). DEVICES: (1) EXTERNAL VENTRICULAR DRAIN (EVD) — the GOLD STANDARD — catheter in frontal horn of lateral ventricle, transduced against a reference (external auditory meatus) — MEASURES ICP AND drains CSF (therapeutic + diagnostic) — BUT highest infection rate (pooled ventriculostomy-related infection about 8.6-11%); (2) INTRAPARENCHYMAL BOLT (Codman, Camino, Raumedic) — fibreoptic/strain-gauge probe bolted into brain parenchyma — LOWER infection (<2%), continuous reading, zero-drift over time, NO CSF drainage — most common in modern practice; (3) SUBDURAL/EPIDURAL sensors — LESS ACCURATE (overestimate/underestimate), rarely used now. ICP WAVEFORM: three peaks per cardiac cycle — P1 PERCUSSION (arterial pulsation — relatively constant), P2 TIDAL (brain COMPLIANCE — rises when compliance falls), P3 RESPIRATORY/DCOUP (venous/respiratory). P2 RISING ABOVE P1 = the brain has EXHAUSTED its compliance reserves = impending intracranial hypertension — a premonitory sign even if the MEAN ICP looks acceptable. CEREBRAL PERFUSION PRESSURE (CPP) = MAP − ICP; target 60-70 mmHg (BTF 4th ed). CPP <60 = cerebral ischaemia (secondary injury); CPP 70 = no added benefit AND increased ARDS risk (from the Robertson/Contant data — aggressive fluid/vasopressor-driven high CPP floods the injured lung). MULTIMODAL NEUROMONITORING recognises that ICP ALONE misses regional ischaemia — PbtO2 (brain tissue oxygen, LICOX/Neurotrend probe — target 20 mmHg — complements ICP), cerebral MICRODIALYSIS (lactate/pyruvate ratio over about 25 = disturbed oxidative metabolism; glycerol and glutamate = cell damage), JUGULAR VENOUS BULB OXIMETRY (SjvO2 <50% = global cerebral hypoxia, 90% = hyperaemia), and CONTINUOUS EEG (non-convulsive status detection). The integration paradigm: treat ICP + CPP + PbtO2 + metabolism TOGETHER — a normal ICP does NOT exclude ongoing brain ischaemia. KEY TRIALS: BTF 4th edition (Carney 2017), BEST:TRIP (Chesnut 2012 NEJM — ICP-guided care NOT superior to imaging-clinical exam in a Bolivian/Ecuadorian cohort, but monitoring is still standard of care in well-resourced settings), BOOST-2 (Okonkwo 2017 — PbtO2 + ICP monitoring reduced burden of brain hypoxia vs ICP alone, trend to better outcome — Phase III BOOST-3 ongoing).