[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Nursing](https://durgical.com/en/nursing/) › [Critical care](https://durgical.com/en/nursing/areas/critical-care/) › Intracranial pressure monitoring and the external ventricular drain: levelling, drainage, waveforms and infection # Intracranial pressure monitoring and the external ventricular drain: levelling, drainage, waveforms and infection - Procedure An ICP monitor or a ventricular drain shows the pressure inside the skull; the nurse levels it, controls drainage and prevents infection. Updated Nov 13, 2026 ## Key points - The zero point is levelled at the ear (tragus or external auditory canal), which matches the foramen of Monro; relevel after every change of position. - Clamp the EVD before moving or repositioning the patient, then unclamp and check the whole system, as the protocol sets. - Record CSF volume and appearance: blood suggests bleeding, cloudiness suggests infection. - Guidelines use a treatment threshold of about 20 to 22 mmHg; CPP = MAP − ICP, often kept around 60 to 70 mmHg. - Infection prevention: hand hygiene, minimal handling, no routine sampling, a clean dry dressing. On this page - The basics Key points - What it is - Indications - Equipment - Step by step (and why) - Next step: when to call for help - Elsewhere in DurgiPedia - Clinical Complications - Safety Contraindications and precautions - Study Test yourself - Connections Connections ## What it is Intracranial pressure (ICP) can be measured with an external ventricular drain (EVD), a catheter in a lateral ventricle that also drains cerebrospinal fluid (CSF), or with a sensor in the brain tissue that only measures. The EVD is the reference method and can be recalibrated, but carries a higher risk of infection and bleeding. The neurosurgery team inserts the device and orders the drainage level; the nurse keeps the zero point level with the ear, controls the drain during moves, records CSF volume and appearance, reads the pressure and waveform, cares for the site and calls early. ICU measures for raised pressure have their own page. ## Indications - Monitoring and treatment of ICP when the team judges the patient at risk of raised pressure (for example severe head injury, brain bleeding, hydrocephalus). - EVD: measures ICP and drains CSF to lower it. Brain-tissue sensor: measures only, cannot drain or be recalibrated. - Normal ICP: traditionally below 20 mmHg. The team sets the threshold and the CPP goal for each patient. ## Contraindications and precautions - The drainage height, the clamped or open status and the limits are ordered by neurosurgery; never change them without an order. - CSF samples are taken only when indicated, not routinely, and by the team the protocol names (often neurosurgery). - Each opening of the system is a chance for contamination: open it only when needed, with aseptic technique. - Head of the bed at the ordered height (often 15 to 30°), head in line with the body. ## Equipment - EVD system with graduated drip chamber and collection bag, pressure transducer and monitor cable. - The unit's levelling tool. - Sterile gloves, antiseptic and dressing material for the site. - Neuro-check chart (level of consciousness, Glasgow, pupils). ## Step by step (and why) - Do hand hygiene before touching any part of the system: EVD infection is a serious complication. - Level the zero point with the ear and check the chamber height ordered: a wrong level drains too much or too little. - Clamp before turning, raising the bed or transport, then unclamp and check: movement changes the level. - Read the ICP as the protocol sets (with an EVD, often clamped for about a minute) and then open again if ordered. - Look at the waveform: normally the first peak (P1) is highest; a second peak (P2) taller than P1 suggests poor compliance. - Record CSF volume at the set times and its colour and clarity: a sudden change matters more than one value. - Empty or change the collection bag with aseptic technique at the fill level the protocol sets (about three-quarters). - Check the site and dressing at the set times for leakage, redness or a wet dressing: change it with sterile technique. - Do neuro checks and compare them with ICP: a change in the patient matters even if the number seems acceptable. ## Complications - Overdrainage can collapse the ventricles and cause bleeding; underdrainage lets ICP rise. - Infection (ventriculitis): fever, cloudy CSF, redness or discharge at the site, neck stiffness, seizures or new deficits. - Bleeding, and blockage or kinking of the tubing when drainage is low or absent. - An EVD measures ventricular pressure, which may not reflect pressure in every part of the brain. ## Next step: when to call for help - Call at once: ICP above the threshold set by the team, a fall in Glasgow, a new unequal pupil, or a waveform where P2 becomes higher than P1. - Call at once: drainage that stops suddenly or becomes much higher, bright red CSF, or a break or leak in the system. - Report the same shift: cloudy CSF, fever, a wet or red site, CSF leak around the catheter. ## Test yourself Think of the answer, then tap the question to see it. ## Where is the zero point of an EVD levelled? At the ear (tragus or external auditory canal), which approximates the foramen of Monro; it is rechecked after every change in position. ## Why is the EVD clamped before turning or moving the patient? Movement changes the level of the drain, which could drain too much CSF; it is unclamped and checked afterwards, as the protocol sets. ## How is cerebral perfusion pressure calculated? CPP = mean arterial pressure − intracranial pressure. ## What can a change in CSF appearance mean? Blood can mean bleeding; cloudiness or sediment can mean infection. Both are reported to neurosurgery. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/nursing/intracranial-pressure-monitoring-and-the-external-ventricular-drain-levelling-dr/) ## Elsewhere in DurgiPedia - [Cerebral blood flow, brain metabolism and intracranial pressure](https://durgical.com/en/physiology/cerebral-blood-flow-brain-metabolism-and-intracranial-pressure/) ## Connections ## Related 4 - [Nursing measures for raised intracranial pressure and after craniotomy: position, triggers to avoid and the Cushing response](https://durgical.com/en/nursing/nursing-measures-for-raised-intracranial-pressure-and-after-craniotomy-position/) - [Neurological checks: level of consciousness, pupils and the Glasgow scale](https://durgical.com/en/nursing/neurological-checks-level-of-consciousness-pupils-and-the-glasgow-scale/) - [ICU bedside formulas: mean arterial pressure, cerebral perfusion pressure, cardiac output and index, shock index](https://durgical.com/en/nursing/icu-bedside-formulas-mean-arterial-pressure-cerebral-perfusion-pressure-cardiac/) - [Raised intracranial pressure on the ward and after head injury or brain surgery: signs, positioning, what to avoid](https://durgical.com/en/nursing/raised-intracranial-pressure-on-the-ward-and-after-head-injury-or-brain-surgery/) ## Related conditions 3 - [Raised intracranial pressure and brain herniation](https://durgical.com/en/conditions/raised-intracranial-pressure-and-brain-herniation/) - [Traumatic brain injury](https://durgical.com/en/conditions/traumatic-brain-injury/) - [Subarachnoid haemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/) [← All of nursing](https://durgical.com/en/nursing/) Educational content for students; it does not replace your institution's protocols, supervised clinical training or a prescriber's order. Dose-calculation examples use made-up numbers: they are educational, not a clinical order. Sources: [Nursing assistance in patient care with external ventricular drain: a scoping review (Sakamoto VTM et al.)](https://www.scielo.br/j/reben/a/4gPz9sdGrvbqKrgTgR8gfNq/?lang=en) (Revista Brasileira de Enfermagem, SciELO, 2021); [Evolving concepts in intracranial pressure monitoring: from traditional monitoring to precision medicine (Mathur R et al.)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11840348/) (Neurotherapeutics, PubMed Central, 2025); [Development of an Evidence-based Care Bundle for Prevention of External Ventricular Drain-related Infection (Ponnambath DK et al.)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11372675/) (Indian Journal of Critical Care Medicine, PubMed Central, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/nursing/intracranial-pressure-monitoring-and-the-external-ventricular-drain-levelling-dr/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/nursing/intracranial-pressure-monitoring-and-the-external-ventricular-drain-levelling-dr/