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

Open cranium model for the study of cerebrovascular dynamics in intracranial hypertension

BACKGROUND

Significant research has been devoted to developing noninvasive approaches to neuromonitoring. Clinical validation of such approaches is often limited, with minimal data available in the clinically relevant elevated ICP range.

NEW METHOD

To allow ultrasound-guided placement of an intraventricular catheter and to perform simultaneous long-duration ICP and ultrasound recordings of cerebral blood flow, we developed a large unilateral craniectomy in a swine model. We also used a microprocessor-controlled actuator for intraventricular saline infusion to reliably and reversibly manipulate ICP according to pre-determined profiles.

RESULTS

The model was reproducible, resulting in over 80 hours of high-fidelity, multi-parameter physiological waveform recordings in twelve animals, with ICP ranging from 2 to 78 mmHg. ICP elevations were reversible and reproducible according to two predetermined profiles: a stepwise elevation up to an ICP of 30-35 mmHg and return to normotension, and a clinically significant plateau wave. Finally, ICP was elevated to extreme levels of greater than 60 mmHg, simulating extreme clinical emergency.

COMPARISON WITH EXISTING METHODS

Existing methods for ICP monitoring in large animals typically relied on burr-hole approaches for catheter placement. Accurate catheter placement can be difficult in pigs, given the thickness of their skull. Additionally, ultrasound is significantly attenuated by the skull. The open cranium model overcomes these limitations.

CONCLUSIONS

The hemicraniectomy model allowed for verified placement of the intraventricular catheter, and reversible and reliable ICP manipulation over a wide range. The large dural window additionally allowed for long-duration recording of cerebral blood flow velocity from the middle cerebral artery.

Large-scale referencing of the telemetric neurovent-P-tel intracranial pressure sensor in a porcine model

The Neurovent-P-tel sensor is a promising device for telemetric intracranial pressure (ICP) measurements in cases of complex hydrocephalus. Data on its accuracy within a broad ICP range are missing. We applied a porcine model for large-scale manipulation of the ICP values. The telemetric ICP sensor was referenced against ICP values measured directly from a water column within a riser tube. A total of 34 comparative ICP measurements within an ICP range from 2 cm H2O to 31 mm Hg were performed. The mean difference between both measurement techniques was 0.4 mm Hg. The limits of agreement, where 95% of differences between both methods are expected, were from -2.4 to 3.1 mm Hg. The telemetric Neurovent-P-tel sensor system provides good accuracy within a broad range exceeding normal ICP values and might be useful in clinical practice.