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Intracranial pressure monitoring
Alternative namesICP monitoring
DefinitionA sensing device placed inside the head that senses the pressure intracranially and sends its measurements to a recording device.
How the test is performedThere are three ways of monitoring intracranial pressure:
The intraventricular catheter is thought to be the most accurate, but if immediate access is necessary, a subarachnoid bolt will probably be used. If there is not a qualified neurosurgeon to place a bolt, then a epidural sensor will probably be used.
The epidural sensor is placed through a burr hole drilled in the skull, just over the epidural covering. Since the epidural lining is not perforated this procedure is less invasive , but it has the disadvantage of not being able to withdraw excess CSF.
After drying, an incision is made and the skin is pulled back until the skull is visible. A drill is then used to cut through the bone and expose the epidural tissue.
If an epidural sensor is used, it is then inserted between the skull and epidural tissue. If a bolt is used, an incision is made through the dura and arachnoid tissue exposing the subarachnoid space and the bolt is screwed into the bone. This allows for the sensor to record from the subdural/subarachnoid space.
If an intraventricular catheter is used, it is threaded through the brain matter into one of the lateral ventricles. This type of catheter is most effective and accurate in its ability to sense intracranial pressure measurements.
How to prepare for the testIf you need this procedure done, you will be in the hospital and most likely in an intensive care unit. If you are conscious your health care provider will explain the procedure and the risks and a consent form must be signed.
How the test will feelIf the procedure is performed under general anesthesia you will feel nothing until you wake from the anesthesia. At that time you will feel the normal side effects of anesthesia, plus the discomfort of the incision made in your skull.
If the procedure is performed under local anesthesia you will fell a prick on your scalp like a bee sing as the local anesthetic is injected. You may feel a tugging sensation as the skin is cut and pulled back to expose the bone. You will hear a drill sound as they cut through the skull bone. This will take a varying amount of time depending on the type of drill that is used. You will also feel a tugging sensation as they suture the skin back together after the procedure.
Your health care provider may prescribe mild pain medications for relief, but he will not want to mask neurologic signs with strong pain medications. With increased intracranial pressure neurologic deficits are common.
Why the test is performedThis test or procedure is performed to measure the intracranial pressure and determine if you are at risk for developing injury from increased intracranial pressure. It is also meant to provide a sterile access for draining excess CSF.
Normal ValuesNormally, the ICP ranges from 1 to 15 mm Hg.
Note: mm Hg = millimeters of mercury
What abnormal results mean
Intracranial pressure monitoring is usually done in cases of severe head injury or after surgeries in cases where a tumor or vascular lesion has been removed or repaired and the surgical team is concerned about brain swelling.
Elevated intracranial pressure can be treated by draining CSF through the catheter, as well as by changing ventilator settings (for those patients who are in critical condition and on a respirator) or by the application of certain intravenous medications.
Intracranial pressure monitoring is crucial in identifying the problem and allowing for immediate treatment. Raised intracranial pressure signifies compression of both neural and vascular tissues and if left untreated can result in permanent neurologic damage and in some cases can be fatal.
What the risks are
Update Date: 8/10/2003Elaine T. Kiriakopoulos, M.D, MSc, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT