Telemetry of intracranial pressure

Clinical and radiological findings in long-term intracranial pressure monitoring

BACKGROUND

Advantages of telemetric devices for long-term intracranial pressure (ICP) measurement have been mentioned several times in the literature. However, descriptions of associated complications are lacking. Therefore, the presented observational study focused on clinical and radiological findings after insertion of an intraparenchymal telemetric ICP monitor.

METHODS

Between April 2010 and February 2013, 185 telemetric ICP catheters were implanted for diagnostic purposes. All patients were clinically followed. Radiological, microbiological and clinical data were analysed.

RESULTS

One brain abscess (0.5 %) and two cutaneous infections (1.1 %) occurred in 185 patients. Staphylococcus spp. could be detected in all cases. Six patients (3.2 %) suffered from single new-onset seizures and one patient (0.5 %) from a temporary hemiparesis. Intracerebral haemorrhages occurred in 15.6 %, most of the time as small punctate bleedings. Perifocal oedematous reactions surrounding inserted telemetric catheters could be observed in 46.9 %. Multiple imaging studies revealed a tendency of complete oedema resolution over time.

CONCLUSIONS

Infectious as well as haemorrhagic complication rates are well comparable with the common literature. The long-term implantation of an ICP probe does not seem to increase the risk of wound infections or brain abscess formation. Surprisingly, very high numbers of oedematous reactions after insertion of the intraparenchymal ICP monitor were seen. Reasons therefore could only be speculated upon.

Evaluation of a new large animal model for controlled intracranial pressure changes induced by capnoperitoneum

BACKGROUND

A standardized large animal model for controlled ICP manipulation within a relevant range and repetitive ICP measurements is missing. We sought to develop such a model on the base of controlled IPP changes induced by capnoperitoneum.

METHODS

We utilized six female pigs (mean body weight 59.5 ± 18.4 kg) for experiments. A ventricular catheter connected with a burr hole reservoir was implanted. ICP was measured directly as cm H2O within a riser tube after percutaneous cannulation of the reservoir. A noninvasive intraperitoneal pressure (IPP) measurement was established (intravesical). Animals were placed in lateral position and a capnoperitoneum was induced. Measurements of ICP, IPP, MAP and respiratory parameters were performed at baseline IPP and after CO2 insufflation to IPP levels of 20 and 30 mmHg.

RESULTS

Baseline IPP in lateral position referenced to median line was 9.8 (±2) mm Hg, while corresponding ICP was 10 (±2.2) mm Hg. After IPP elevation to 20 mmHg, ICP increased to 18.8 (±1.9) mm Hg. At 30 mmHg IPP, ICP increased to 22.8 (±2.8) mm Hg. Except peak airway pressure, all other parameters were kept constantly. Mean ICP variation in the individual subject was 13.4 (±2.5) mm Hg, while a ICP range from minimum 9 to maximum 31 mmHg was documented.

CONCLUSIONS

We report a large animal model that allows (1) repeated measurement of the ICP and (2) manipulation of the ICP within a large pressure range by controlled IPP changes due to capnoperitoneum.

Telemetric ICP measurement with the first CE-approved device: data from animal experiments and initial clinical experiences

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic(®) NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedic's NEUROVENT(®) P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.