Abstract Details

Title Simulating the Physiological Purpose of Cushing Reflex: An Accessory Cerebral Windkessel in Extremis

Topic Neuro Trauma and Critical Care

Presentation(s) P6 - Poster Session 6 (5:00 PM-6:00 PM)

Poster/Presentation
Number 19-001

Objective We simulate arterial hypertension and bradycardia in Cushing reflex in severe obstructive hydrocephalus (OH) using an electric circuit model.

Background Cushing reflex is the triad of hypertension, bradycardia, and irregular respirations in the setting of acute hydrocephalus and/or markedly elevated intracranial pressure (ICP). Intracranial dynamics can be understood within the framework of the cerebral windkessel. The cerebral windkessel is a buffer that protects the brain capillaries from the arterial blood pressure (ABP) pulse by diverting this pulse from the arteries through the cerebrospinal fluid (CSF) to the veins. This is akin to an electric circuit, in which direct current (DC) power (smooth blood flow) travels in the capillary circulation and alternating current (AC) power (pulsatile CSF flow) travels in the CSF pathways. Severe OH is characterized by high impedance to AC power in the CSF path due to high CSF space resistance which impairs the windkessel and reroutes AC power from the CSF through the capillaries, leading to deleterious capillary disruption, edema, elevated ICP, and herniation.

Design/Methods We model OH as windkessel impairment caused by increased resistance to AC power in the CSF pathway simulated in an electric circuit with parallel inductance and capacitance to simulate the pulsatile flow of blood and CSF as AC power, and smooth flow as DC power. We then simulate Cushing reflex by lowering the frequency from the AC voltage source (to stimulate bradycardia) and by increasing the DC voltage (to simulate arterial hypertension).

Results In our simulation, Cushing reflex improves windkessel function by reducing AC power in the cranium and augmenting DC power in the capillary circulation.

Conclusions Arterial hypertension increases DC power in the cerebral capillaries and bradycardia increases intracranial inertance and decreases total AC power, which varies proportionately with frequency. Cushing reflex ameliorates windkessel impairment and can be understood as an accessory cerebral windkessel in extremis.

Authors/Disclosures
Racheed M. Mani, MD PRESENTER	Dr. Mani has nothing to disclose.
Nahid Shirdel Abdolmaleki	Mrs. Shirdel Abdolmaleki has nothing to disclose.
Anand Ravishankar	Mr. Ravishankar has nothing to disclose.
Liu Yang, PhD	Dr. Yang has nothing to disclose.
Tingchang Wang, PhD	Mr. Wang has nothing to disclose.
Jade Basem, BA	Ms. Basem has nothing to disclose.
Chiemeka D. Uwakwe, MS	Mr. Uwakwe has nothing to disclose.
Petar M. Djuric, PhD	The institution of Prof. Djuric has received research support from NSF.
Michael Egnor, MD	Dr. Egnor has nothing to disclose.

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