Background and purpose: Making a limb transiently ischemic has been shown to induce ischemic tolerance in a distant organ. This phenomenon is known as remote ischemic limb preconditioning. We conducted a Phase IB study of remote ischemic limb preconditioning to determine the safety and feasibility of increasing durations of limb ischemia in patients with subarachnoid hemorrhage.
Methods: Patients with aneurysmal subarachnoid hemorrhage underwent limb preconditioning every 24 to 48 hours for 14 days. Limb preconditioning consisted of 3 5-minute inflations of a blood pressure cuff to 200 mm Hg around a limb followed by 5 minutes of reperfusion. In the lead-in phase, we preconditioned the upper extremities, but this proved impractical and we began preconditioning the leg in a similar manner. Ischemia times were then escalated to 7.5 and 10 minutes. After each session, a visual analog scale was obtained and the extremity examined for neurovascular complications.
Results: A total of 33 patients completed the study. Mean age was 53±12 years and mean Hunt Hess score was 2.4±0.9. In the lead-in phase, an average of 7.7±2.4 preconditioning sessions was completed with mean visual analog scale 3.6±3.4. In the dose escalation phase, an average of 8.6±2.1 preconditioning sessions was done with mean visual analog scale 1.8±2.2 and 2.5±2.9 for the 7.5- and 10-minute cohorts, respectively. No session was prematurely terminated due to subject discomfort. No objective signs of neurovascular injury were observed.
Conclusions: We found limb preconditioning to be safe and well tolerated, even at ischemia times of 10 minutes, in critically ill patients with subarachnoid hemorrhage.