gms | German Medical Science

Objective: For treatment of refractory increased intracranial pressure (ICP), a controlled lumbar drainage (LD) of cerebral spinal fluid is accepted as a last tier treatment option. On the other hand, LD in acute brain injury remains associated with the fear of tentorial herniation, because reliable biomarkers for prediction and detection of tentorial herniation during LD remain lacking. In this study, we hypothesized that an alteration of the conduction of pulsatile waveforms across the level of foramen magnum might serve as a predictor for brain herniation in patients with acute brain injury and controlled LD for treatment of refractory increased ICP.

Methods: This retrospective, single-center study included 142 patients with continuous external ventricular drain (=ICP) and lumbar drain pressure (=LP) monitoring. In all patients, continuous recordings of ICP, LP and arterial blood pressure (=ABP) were screened throughout a recording period of 4-10 days. Pressure differences between ICP and LP >5mmHg over 5 minutes were defined as a Delta (D)-Event, implicating a non-sufficient hydrostatic communication. During this period, ICP-, LP- and ABP-wave-form oscillation analysis was performed by determining eigenfrequencies (EF) and their amplitudes (AEF) via Fourier-Transformation scripted in Python. Since oscillatory behavior analysis is independent of absolute values, potential confounders such as height difference between drainage and head position did not affect results. Schematic data processing is demonstrated in Figure 1 [Fig. 1].

Results: Out of 142 screened patients with 2993 hours total recording time, 14 patients exhibited a D-Event with a median ICP of 12.2mmHg (range 10.7-18.8mmHg) and LP of 5.6mmHg (range 3.3-9.8mmHg). During the event, the median of the first two AEF of LP decreased from 1.11mmHg (range 0.34-3.62mmHg) to 0.48mmHg (range 0.17-0.83mmHg), while AEF of ABP and ICP remained stable. The ratio of first AEF between ICP and LP (*p<0.01) and between ABP and LP (*p=0.032) significantly increased 3 hours prior to the D-Events, whereas the ratio between ICP and ABP remained unaffected.

Conclusion: The oscillation behavior of LP curves changes during D-Events and the ratio of AEF between ABP and LP may serve as a simple and safe surrogate biomarker to identify D-Events during LD at bedside in real-time without the need for ICP monitoring.