From the Research
For an unsecured aneurysm following aneurysmal subarachnoid hemorrhage, the external ventricular drain (EVD) should initially be set at 20-25 mmHg (or 15-20 cm H2O) above the external auditory meatus. This higher setting helps maintain adequate cerebral perfusion pressure while minimizing the risk of rebleeding. The most recent study 1 emphasizes the importance of accurate intracranial pressure (ICP) monitoring via EVD, suggesting that a minimum period of 5-minute EVD closure is needed before documenting a true ICP. However, the study also notes that in clinical practice, EVD closures often last less than 1 minute, which may not be sufficient to reach ICP equilibrium.
Key Considerations
- The EVD should be positioned at the level of the foramen of Monro (approximately at the level of the external auditory meatus) for accurate pressure readings.
- Regular monitoring of neurological status, intracranial pressure, and cerebrospinal fluid drainage volume is essential during this period.
- The drainage system should be kept closed except when draining CSF to maintain the set pressure parameters, and strict aseptic technique must be followed to prevent infection.
- After the aneurysm is secured through surgical clipping or endovascular coiling, the EVD setting can be gradually lowered to more standard levels of 10-15 mmHg.
Evidence Summary
The provided studies 2, 3, 4, 5, 1 offer insights into EVD management and ICP monitoring in patients with aneurysmal subarachnoid hemorrhage. However, the most recent and highest quality study 1 provides the most relevant guidance on EVD setting and ICP monitoring. The study highlights the importance of waiting long enough before recording the real ICP value, with a suggested minimum period of 5-minute EVD closure.
Clinical Implications
In clinical practice, it is crucial to prioritize accurate ICP monitoring and maintain adequate cerebral perfusion pressure to minimize the risk of rebleeding in patients with unsecured aneurysms. By following the recommended EVD setting and monitoring protocol, clinicians can optimize patient outcomes and reduce the risk of complications.