A Bedside Perspective of EVDs

Caution: These are general tips and knowledge to help you feel more comfortable and properly educated for this type of situation/patient! Each facility and clinician have various policies/practices. 

CONTRAINDICATIONS: Just like any other invasive procedure, prior to drilling into a patient’s head, be sure that the doctors have assessed coagulopathic state, presence of brain abscess, or scalp infection.

DEVICES:
Generally speaking, there are two devices that could be implanted into the patient: a bolt or a drain. A patient can have just one of the two, or both. A bolt is for monitoring ICPs specifically whereas a drain can also be used to remove fluid in a therapeutic manner. There are pros and cons for each and which is chosen depends on patient-related factors.. These devices can be placed in the OR but more commonly placed at the bedside.

BOLT: A bolt is a catheter with a strain-gauge (measures a change in force) tip that is usually inserted into the parenchyma. This allows for continuous measurements of ICPs. These bolts can also be placed in the subdural and subarachnoid space. As mentioned before, it is patient/situation-dependent as well as physician preference! So why a bolt over a drain one might ask? It is less invasive, easy to install, and has much less risk of infection than an EVD. However, once inside the patient’s brain, the catheter cannot be recalibrated, if the tip of the transducer becomes kinked or occluded it can cause inaccurate measurements. 

EVD: External ventricular drain that is usually placed in the lateral or third ventricles to drain CSF, blood, mitigate intracranial hypertension, and/or instill meds. With this device, you lose the accuracy of the ICP if the drain is set to drain continuously (stay open). Be aware that if the device is set to drain continuously there is an increased risk of infection and hemorrhage. The drain has to be re-zeroed with any change in the patient head of bed or transport. 

The picture to the right shows the actual drain that is calibrated, zeroed, and where the CSF fluid drains into and can be monitored at all times. It is extremely important that this drain does not be moved or accidentally dislodged from the patient. The drain itself will be sutured on the patient, but the external device is something the bedside nurse needs to be aware of at all times. Please always clear if the drain should be set to mmHg or mmH2O as well. Orders will be patient and physician-driven, and can be adjusted in an acute situation just as other external devices on patients

Symptoms to be aware of that could indicate adverse events of drain and need to notify the LIP or team are as follows: infection, new-onset headache, decreased CPP, nausea, change in mental status (From baseline), and lethargy. Strong indications for infection are erythema and tenderness at the insertion site with weak to low indications being fever without other known sources.