Response to Letter by Gonzalez and Liebeskind Regarding Article, “Remote Ischemic Limb Preconditioning After Subarachnoid Hemorrhage: A Phase Ib Study of Safety and Feasibility”
We appreciate the comments on our article by Drs Gonzalez and Liebeskind and their discussion of several interesting aspects of our preconditioning protocol.1 The importance of adequately imposing ischemia in the limb cannot be overstated and we took great care to achieve this objective consistently and uniformly. As described in the “Methods” section of our article, the blood pressure cuff was inflated to 200 mm Hg or 20 mm Hg above the systolic pressure if triple H therapy required systolic blood pressures higher than 180. The loss of blood flow was monitored by palpation of the posterior tibial or dorsalis pedis pulse.
Given our inclusion criteria of patients with Hunt–Hess score of 1 to 4, the visual analog scale will have a variable degree of sensitivity. However, the promise of preconditioning may be of most benefit to those with greater degree of disease severity. Monitoring pain and tolerability in patients with subarachnoid hemorrhage remains a challenge given that both cognition and autonomic as well as cardiovascular markers of discomfort are altered by the disease process or its treatment.
We agree with the authors that these patients need to be monitored carefully for deep vein thrombosis. Regular nursing assessments, inspection by the study staff, extremity ultrasounds when clinically warranted, and uniform use of both pharmacological and mechanical thrombosis prevention modalities were the precautions taken on all patients in our study. No additional deep vein thromboses or pulmonary embolism were reported by any of our patients at 3-month follow-up. The presence of clinical and subclinical deep vein thromboses in extremities that were not preconditioned may perhaps reflect the prevalence of this common morbidity in this high-risk patient subpopulation. The existence and potential consequences (if any) of subclinical vascular injury are unclear at the present and have not been reported in limb preconditioning other target organs.
Many questions remain on the optimal protocol, the duration of ischemia, and the quantification of risks and benefits of this technique. We hope that our preliminary, but propitious, experience will encourage further studies in search of answers.
Michael Katsnelson, MD
Sebastian Koch, MD
Miguel Perez-Pinzon, PhD
Department of Neurology
University of Miami Miller School of Medicine
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