ICP monitor placement
Formal Definition
Intracranial pressure (ICP) monitor placement — a neurosurgical procedure to insert a pressure-measuring device into the cranial cavity in patients with suspected or confirmed elevated intracranial pressure, most commonly due to severe traumatic brain injury (TBI), large ischemic or hemorrhagic stroke, intracranial hemorrhage, or intracranial mass with edema; methods include (1) External Ventricular Drain (EVD) — gold standard, allows both ICP monitoring and therapeutic CSF drainage through a ventricular catheter connected to a strain gauge or external transducer; (2) Parenchymal fiberoptic monitor (e.g., Camino bolt) — placed through skull into brain parenchyma; less accurate with drift but easier placement; (3) Subdural or epidural monitors — less common, less accurate.
How It's Used on the Ward
"Bolting the head" or "placing an ICP monitor" — what neurosurgery does emergently when a patient has signs of elevated ICP (depressed GCS, blown pupil, Cushing's triad of bradycardia/hypertension/irregular respirations) to objectively measure and treat ICP; the monitor is a temporary device often used for days until ICP normalizes.
Example
""25-year-old unrestrained driver in MVC, brought in intubated, GCS 4T (E1 VT M3T), large right subdural hematoma on CT, midline shift 6 mm. Neurosurgery consulted; family consents to procedure. Operating room: right frontal external ventricular drain placed. Initial ICP measurement: 32 mmHg (goal <20). Treated with hypertonic saline, head of bed elevated, mild hyperventilation as bridge. ICP trends down over 12 hours to <20 with treatment. Patient ongoing ICP monitoring, awaiting definitive intervention for SDH as blood pressure stabilizes.""
Clinical Context
Indications: (1) Severe TBI with GCS ≤8. (2) Large intracranial hemorrhage (SDH, EDH, IPH) with mass effect. (3) Large ischemic stroke with edema at risk of herniation. (4) Hydrocephalus requiring CSF diversion. (5) Post-craniotomy ICP monitoring. Goals of monitoring: target ICP <20 mmHg (some say <22 to allow individual variation), cerebral perfusion pressure (CPP) = MAP - ICP, target CPP 60-70 mmHg in adults. Treatment thresholds: ICP >20 mmHg for >5-10 minutes → escalate; CPP <60 mmHg → consider vasopressor/inotropic support to maintain MAP. Placement: typically IN THE OR (but bedside placement in ICU under sterile technique is also possible in emergencies, particularly EVD). Common insertion site: Kocher's point (right or left, ~1 cm anterior to coronal suture, ~2-3 cm from midline) for frontal EVD. Complications: (1) Hemorrhage along track. (2) Infection (ventriculitis — should be replaced if infected; prophylactic antibiotics are controversial). (3) Misplacement/catheter malfunction. (4) CSF overdrainage (causes subdural hygroma, collapse). (5) Brainstem or vascular injury at placement (rare, but dangerous). Weaning: ICP monitoring continued until ICP <20 mmHg sustained ≥24 hours without intervention. EVD also allows CSF sampling (meningitis, SAH).