Intracranial Pressure

Topics: Traumatic brain injury, Intracranial pressure, Cerebrospinal fluid Pages: 7 (2169 words) Published: November 1, 2011
Blood, cerebrospinal fluid (CSF) and brain tissue are all constituents of the cranium. The pressure within the cranium is known as intracranial pressure (ICP); it is the same as that found in the brain tissue and CSF. (2) The pressure-volume relationship between ICP, brain tissue, blood, volume of CSF, and cerebral perfusion pressure (CPP) is known as the Monro-Kellie hypothesis.(12) This hypothesis states that the cranial compartment is considered as an enclosed and inelastic container, which has a fixed volume; if an increase of any one of the components occurs, it must be accompanied with a decrease in another in order to maintain a state of equilibrium, if this does not occur it will eventually lead to an increase in ICP. (13) The normal values for ICP are dependent on the age of the patient, their body posture and clinical conditions. In adults normal range is considered 40mm Hg. (7) ICP hypertension can be caused by a number of things, these can be: either intracranial (primary) - brain tumour, trauma, non-traumatic intracerebral haemorrhage, ischemic stroke or hydrocephalus. Or it may be extracranial (secondary) - airway obstruction, hypoxia, hypertension, seizures, posture, drug intoxication, or it may be postoperative- mass lesions, increased cerebral volume or disturbances of CSF. (14) ICP hypertension signs and symptoms vary relying on etiology. Common symptoms that suggest a rise in ICP include headache, nausea, vomiting, ocular palsies, back pain, progressive mental status decline and papilledema. (17) In regards to the boy in our case study, it is clear that he most probably has elevated ICP due to traumatic brain injury (TBI)- which is a primary cause of elevated ICP; this is evident from the symptoms that he was experiencing. In order to get a definitive diagnosis it is crucial that further tests be carried out. Sustained elevated levels of ICP will lead to reduced cerebral blood flow and hence brain herniation. Pressure will arise from the herniation, causing brain injury and may possibly lead to death. (17) Hence, it is vital to identify patients with elevated ICP. ICP monitoring may be crucial in some patients, but care should be taken as it is an invasive technique and may cause unwanted risks. Therefore monitoring should only be used in patients that will benefit from it; these include patients with severe TBI with a Glasgow Coma Scale (GCS) < 8, post craniotomy, hematomas, abscesses or tumours that occlude the CSF pathway, intracranial hemmorrhage, cerebral oedema, encephalopathy from hypertensivecrisis, and meningitis/encephalitis that causes malabsorption of CSF.(9) Utilisation of an ICP monitoring device is important in the above mentioned patients; it is also the only way to reliably diagnose a patient with an elevated ICP. The three devices used to monitor ICP include: • The subarachnoid screw- which is a hollow screw that is inserted into the Dura matter through a hole drilled in the skull; the screw is connected to an external traducer via tubing. CSF fills the screw and allows the sensor to record from within the subdural space. Advantages of this method include the decreased risk of infection and haemorrhage, and the disadvantages include misplacement of the screw, errors in ICP readings leading to underestimation and occlusion by debris. (11) • The Subdural/Epidural Catheter- which is inserted between the skull and dural tissue. The epidural sensor is placed through a burr hole drilled in the skull. It is less invasive but also less accurate and can’t be used to drain CSF; it also has a lower risk of infection or hemorrhage (19). • Ventriculostomy which is the most commonly used device and also the most accurate way to receive and monitor ICP. (19). A burr hole is drilled into the lateral ventricle of the brain (which contains CSF) and a catheter is inserted. This catheter is connected to a standard transducer set which is never pressurized. In addition to monitoring ICP the...
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