Hydrocephalus
Blood in the subarachnoid space can occlude the arachnoid villi, which normally absorb cerebrospinal fluid (CSF) at the same rate that it is produced. This leads to an increased volume of CSF and hydrocephalus. The development of hydrocephalus can be acute, subacute or chronic and can cause severe headache, nausea, vomiting and change in neurological status and motor strength . Adam and Osbourne (2005) explained that acute hydrocephalus is associated with the most severe bleeds and poor outcome; it is treated by draining the excess CSF using an EVD. Mrs S had an EVD inserted as an emergency procedure before being admitted to ICU. Woodward et al (2002) explained that EVD insertion involves placing a thin soft catheter into one of the lateral ventricles of the brain via a small burr hole through the skull. The catheter is then connected to the drainage system, which is set at a level measured in cm H20. Mrs S’s EVD was set at 20 cm H20, with the aim of draining off excess CSF if her ICP rose above 20 cm H20. The amount and colour of CSF drained was recorded and it was particularly important to observe for fresh blood, as this could indicate rebleeding . CSF is normally a clear, colourless fluid; following SAH it may be obviously blood stained (i.e. rose or frank blood) but xanthochromia (yellow discolouration) can also be present around 8 hours after SAH. It was also important to ensure the drain was patent by looking for oscillation of the CSF: if this is absent, along with no drainage, it could indicate that the drain is blocked, which will result in an uncontrolled rise in ICP. Mrs S’s drain remained patent, it drained a constant amount of 10-15 ml/hour CSF, indicating that her ICP was stable at 30-35 cm H20 , and there was no change in the rose-coloured appearance of her CSF.