An external ventricular drain often known as an EVD is often used an interim treatment for obstructive hydrocephalus. It has an added measure of measuring the ICP. It works on a simple basis that CSF will drain from the ventricles if the pressure ICP is set higher than that of the pressure setting on the drain. For examples if you set the pressure level at 10mmHg, and if the pressure in the CSF is 20mmHg than fluid will drain. If the ICP is less than that set at the level of the drain than it will ‘swing’
An EVD involves placing a catheter within the ventricles. The manometer is set at the EAM which is at the level of foramen on Munro.
During admission they may raise the pressure on the drain to try and encourage the brains normal physiological mechanism of resorption of CSF. More likely patients undergo a VP Shunt for permanent management of their hydrocephalus.
Indications for EVD
- Hydrocephalus
- Treatment of ventriculitis e.g for administration of antibiotics
Complications of EVD
- Intra-operatively- malposition of the drain, bleeding
- Post-Operatively: Infection- ventriculitis- replace catheter give potential for intra-thecal or iv antibiotics
- Post-Operatively: Blockage- is the bag draining, is the EVD Swinging, try to flush and aspirate the EVD. These must be performed under sterile conditions
- CSF Leakage: occurrs when the drain exits the scalp. May need to suture to tighten the space between the drain or the scalp. The drain may also have become displaced.