Introduction: Remote ischemic conditioning is a powerful phenomenon where brief periods of ischemia and reperfusion in a tissue such as the leg or arm can confer protective benefits from ischemic injury to distant tissues. Our previous work using intracranial pressure (ICP) waveform analysis has identified trends in the waveform shape that suggest transient cerebral vasodilation occurs as an effect of the procedure. We present a more rigorous analysis using data prospectively collected as part of our phase I clinical trial of RIC for aneurysmal subarachnoid hemorrhage (aSAH).
Methods: During the RIC procedure ICP was measured using intraventricular monitors simultaneously recorded with ECG (Fs = 400 Hz). ICP analysis was performed using the Morphological Clustering and Analysis of Intracranial Pulse (MOCAIP) algorithm which extracts 128 metrics from the ICP pulse-waveform (Figure 1A). Previous studies in patients undergoing CO2 inhalation identified a template of 72 metrics that consistently increase or decrease during vasodilation of the cerebral vasculature. The proportion of metrics that match this template (VDI) was found for each session and compared with VDIs from a control set of normal pressure hydrocephalus (NPH) patients using a Mann-Whitney test.
Results: Fifteen aSAH patients had ICP monitored during 29 RIC sessions of approximately 40 minutes. ICP segments of the same length were collected for 8 NPH patients. The median VDI was significantly higher in the RIC patients (0.79, 0.42, p<0.01) (Figure 1B)
Conclusions: Pulse-waveform changes observed during the RIC procedures indicate vasodilation when compared to control patients. Intracranial pressure waveform analysis is a useful tool to detect real time changes in the state of the cerebrospinal circulatory system, providing additional insight into the mechanism and effects of RIC.
Patient Care: A better understanding of the physiological changes associated with remote ischemic conditioning will help to better apply this technique to protect against cerebral ischemia.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the transient effects that occur during remote ischemic conditioning, and the importance of intracranial pressure waveform trends associated with changes in the cerebrovascular state