gms | German Medical Science

Objective: A drawback in the use of external ventricular drainage (EVD) originates in its nature that draining CSF (open system) and ICP monitoring is feasible at the same time, but considered to be not reliable regarding the ICP trace. Furthermore, with the more widespread use of autoregulation monitoring using the blood pressure and ICP signal, the question arises if ICP signal form an open EVD can be used for this purpose. Using an EVD system with an integrated parenchymal ICP probe we compared the different traces of ICP signal and their derived parameters under opened and closed CSF drainage.

Methods: 20 patients with either subarachnoid or intraventricular hemorrhage and indication for ventriculostomy plus ICP monitoring received an EVD in combination with an air-pouch based ICP-probe. ICP was monitored via the open ventricular catheter (ICP_evd) and the ICP probe (ICP_probe) simultaneously. Neuromonitoring Data (ICP, ABP, CPP, PRx) were recorded by ICM+ software for the time of ICU treatment. Routinely (at least every 4 hours) ICP was recorded with closed CSF drainage system for at least 15 minutes. ICP, ICP amplitude and the autoregulation parameters (PRx_probe, PRx_evd) were evaluated for every episode with closed CSF drainage and during the 3 hours before with open drainage system.

Results: 144 episodes with opened/closed drainage were evaluated. During opened drainage overall mean ICP_evd levels were non-significantly different from ICP_probe with 9.8 + 3.3 versus 8.2 + 3.2 mmHg, respectively. Limits of agreement ranged between 5.2 and -8.3 mmHg. However, 51 increases of ICP >20 mmHg with a duration of 3-30 min were missed by ICP_evd and in 101 episodes difference between ICPs was greater than 10 mmHg. After closure of EVD, ICP increased moderately for both methods. Mean PRx_evd was significantly higher (falsely indicating impaired autoregulation) and more objected to fluctuations than PRx_probe.

Conclusion: The general practice of draining CSF and monitoring ICP via an (usually opened) EVD plus frequently performed catheter closure for ICP reading is feasible for assessment of overall ICP trends. It has however clinically relevant drawbacks, namely a significant amount of undetected increases in ICP above thresholds and continuous assessment of cerebrovascular autoregulation is less reliable. In conclusion, all patients who need CSF drainage plus ICP monitoring due to the severity of their brain insult, are in need of either an EVD with integrated ICP probe or an EVD line plus a separate ICP probe.