Remote Ischemic Preconditioning Mechanism Study

Overview

This research is being done because pain is a significant problem for patients with a variety of medical problems and following surgery or traumatic injury. Currently available pain medications may not relieve all types of pain or may relieve pain only at doses that produce side effects and potential complications. Although Remote Ischemic Preconditioning (RIPC) appears promising, there remain several unanswered questions about how it works. This research trial will help determine how RIPC may activate the bodies natural pain control system. The goals of this study are to see if RIPC has any effect 1) on a small area of skin that will be expose to a small amount of UV- B radiation (a mild sunburn), 2) on acute thermal heat temperatures that will be applied to skin, and 3) on the sunburn-like sensation to light touch after putting capsaicin cream (the active ingredient in hot chili peppers) on skin. Remote ischemic preconditioning is done by inflating a balloon (very similar to a blood pressure cuff) on the leg until it blocks blood flow for a few minutes. The cuff is then deflated and blood flow resumes. The process is repeated up to three times. This procedure causes the body to increase its natural pain relief system that may help to decrease the amount of postsurgical pain.

The purpose of this pilot study is to determine whether RIPC effects peripheral sensitization, central sensitization or both and determine effect size since there is no data regarding the presumed effect. These issues cannot be easily sorted out in patients experiencing postoperative pain and hypersensitivity, since surgery affects both components. In order to address this purpose the investigators will examine, in healthy volunteers, the effect of RIPC on a manipulation which generates hypersensitivity by an exclusive peripheral mechanism (ultraviolet B (UV-B) burn) and a manipulation which generates hypersensitivity by an exclusive central mechanism (topical capsaicin). Understanding the sites at which RIPC reduces the amplification of pain after injury will be useful in determining where it would be most logically applied clinically and in guiding preclinical mechanistic studies.