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Types of Intracranial Pressure Monitoring Devices
There are three main types of intracranial pressure (ICP) monitoring devices that are commonly used in hospitals:
External Ventricular Drainage (EVD) Catheter
An EVD catheter is a small plastic tube that is inserted through a small hole in the skull and into the ventricle of the brain. Cerebrospinal fluid (CSF) will continuously drain through the catheter into a drainage bag system outside of the body. This allows doctors to directly measure the pressure of CSF and determine if intracranial pressure is elevated or normal. EVD catheters provide the most direct measurement of ICP but also carry higher risks of infections due to passing through the skin and skull.
Intraparenchymal Pressure Sensors
Intraparenchymal sensors are small, solid-state devices that are implanted directly into the brain tissue, usually in the white matter. They have a pressure-sensitive transducer tip that is able to detect fluctuations in ICP. The sensor is connected to an external monitor via a thin cable passing through the skin. This type of sensor contact brain tissue directly and provides a continuous measurement of ICP but also has risks of hemorrhage or infection during placement.
Subdural Pressure Sensors
Subdural sensors are thin silicon plates with a pressure transducer that is placed between the brain’s surface and the dura mater (the tough outer covering of the brain). The transducer converts pressure changes into electrical signals to monitor ICP trends. Subdural sensors have less risk of intraparenchymal hemorrhage compared to intraventricular catheters or intraparenchymal sensors but only provide an indirect measurement of overall pressure trends rather than an exact pressure reading.
Indications for Intracranial Pressure Monitoring
There are several medical conditions where monitoring ICP may be necessary or beneficial. Some common indications for placing an ICP monitor include:
Traumatic Brain Injury – ICP monitoring can help guide treatment and manage elevated pressure after a head injury from accidents, assaults or other traumatic events.
Stroke – Large or severe strokes can cause cerebral edema and elevation of ICP. Monitoring pressure helps detect dangerous surges.
Brain Tumors – Especially large or rapidly growing brain tumors can compromise fluid circulation and elevate pressure. ICP monitoring during tumor resection surgeries also helps.
Infections – Bacterial meningitis or encephalitis cause inflammation that elevates pressure. Knowing the degree of pressure helps guide antibiotic treatment.
Hydrocephalus – The buildup of CSF in ventricles due to blockages requires monitoring to detect overwhelming pressure rises.
Congenital Malformations – Conditions present from birth that affect fluid drainage like aqueductal stenosis may require lifelong ICP monitoring.
Post-Neurosurgery – Monitoring for several days after brain surgery detects pressure changes related to edema or postoperative complications.
ICP Monitoring Procedure and Setup
Placing an ICP monitor usually requires a brief surgical procedure involving making an incision in the skin of the head and drilling a small hole into the skull. The proper type of monitor is then inserted or placed depending on the individual patient’s needs and medical condition.
Once in place, the monitor is externally connected to transducers and an electronic monitoring device. This setup continuously measures the pressure and may also record other important readings like pulse, oxygen saturation and body temperature.
Alarms can be preset to sound if pressure reaches certain thresholds to alert clinical staff. The monitoring period typically lasts several days but may occasionally need to remain in place longer depending on the underlying condition and patient recovery.
Before removing the monitor, another brief procedure cleans and closes the small incision site. Doctors analyze the pressure data obtained to guide treatment decisions and evaluate if further monitoring may be necessary.
Factors That Influence ICP Readings
Many external and internal physiological factors can directly influence a patient’s intracranial pressure at any given time. Some key things that change the ICP readout on monitors include:
– Positioning – Lying flat increases pressure versus being raised 30 degrees.
– Breathing – Deeper breaths cause slight temporary pressure changes with each respiratory cycle.
– Fluid Volume – Dehydration decreases pressure but excess fluids like IV sources or a full bladder raise it.
– Heartbeat – Each pulse transiently elevates pressure a few mmHg then immediately falls off.
– Cerebral Blood Flow – More flow to the brain, like fever responses, momentarily boosts pressure.
– Metabolism – Higher cellular activity and chemical processes alter fluid and pressure dynamics.
– Brain Compliance – Stiffer more edematous tissue resists pressure changes less than healthy elastic tissue.
– CSF Dynamics – Blocked absorption and drainage deteriorate the balance of CSF production and reabsorption.
Careful consideration of all these internal and external influences helps clinicians properly diagnose pressure derangements and determine appropriate treatments.
Managing Elevated Intracranial Pressure
If ICP monitoring determines pressure is too high, certain medical interventions may become necessary. The general treatment approach aims to lower pressure through these main strategies:
Medical Therapy – Osmotic diuretic drugs like mannitol draw fluid from brain cells to reduce swelling while steroids reduce inflammation.
Sedation – Medications calm the patient and suppress spontaneous breathing efforts to inhibit pressure surges.
Hyperventilation – Blowing off excess carbon dioxide from lungs via a ventilator constricts blood vessels and lowers pressure.
Decompression – Surgically removing a small piece of skull relieves compression on swollen brain tissue.
Drainage – Inserting an EVD catheter pulls excess CSF from the ventricles to make more room.
Therapy – Whole body cooling, hyperosmolar solutions and other interventions address the underlying pathophysiology driving pressure elevations.
Keeping ICP below a target threshold, usually 20-25 mmHg but individualized, improves oxygen delivery to the brain and limits further injury from herniation. Persistent or refractory high pressure despite treatments carries worse neurological outcomes. Close ICP monitoring guides appropriate and timely interventions.
Outcomes of ICP Monitoring
Success rates from ICP monitoring rely on starting early when pressures first become elevated rather than waiting until clinical deterioration occurs. Some research findings regarding monitoring outcomes include:
– Over 50% of severely brain injured patients experienced at least one episode of elevated ICP not detected by clinical exams alone.
– Starting medical ICP-lowering therapies guided by monitors modestly improves mortality rates and decreases poor functional outcomes versus clinical assessment alone.
– In neurosurgical patients, additional information from monitors helped optimize operations and postoperative care compared to no pressure data available.
– Long term studies show patients who have their ICP controlled within normal limits by monitoring have better five year survival rates than when controls were poorer.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile
