256. Evaluation of Intracranial Compliance in a Pig Model of Traumatic Brain Injury

Authors: Alicia Everitt; Brandon Root, MD; David Bauer, MD; Ryan Halter, PhD (West Lebanon, NH)

Introduction:

This study investigated changes in intracranial compliance (ICC) and intracranial pressure (ICP) in response to an expanding mass lesion, such as hematoma, in a pig model of traumatic brain injury (TBI) (n=8).

Methods:

An ICC catheter, ICP sensor, and Mass Effect (ME) catheter were precisely placed into the pig’s left ventricle, right frontal lobe, and left parietal lobe, respectively, using frameless stereotactic guidance (Stealth AxiEM). The ME balloon was inflated in steps of 100 uL to a total volume of 1.2 mL over one hour. At each ME volume increment, the 150 uL ICC balloon was rapidly inflated and deflated to provide a volume impulse. ICP was recorded continuously during the experiment. Compliance was calculated as the change in volume divided by the change in pressure for each ICC balloon stimulus. Compliance response was evaluated across changing ICPs and volumes.

Results:

Fogarty ME balloon inflation elevated ICP in 8/8 pigs (18.6 ± 5.3 mmHg – 31.0 ± 8.1 mmHg). Compliance ranged from 114 uL/mmHg to 33 uL/mmHg and significantly decreased as ME volume increased across all pigs (p<0.05). ICP did not respond to ICC stimulus until ICP surpassed 15 mmHg (two pigs). When baseline ICP was >20 mmHg, ICC changed less (i.e. reached a saturation point) than when baseline ICP started in a more physiologically healthy range (<20 mmHg). Change in ICC negatively correlated to change in ICP (r=-0.7).

Conclusion:

Intracranial compliance was successfully quantified during induced intracranial hypertension in a pig model of TBI. Compliance negatively correlated to pressure change and tracked an expanding focal mass lesion (e.g. hematoma growth) with statistical significance. Characterizing the compliance response to trauma may help to predict intracranial response to treatments and ICP indications of enlarging cerebral hematomas.