Pain, be it post-operative in nature or arising from acute and chronic injuries, is a common and frustrating clinical manifestation. In fact, the current opioid crisis highlights the need for the medical community to discover alternative means for pain control. Personalized Blood Flow Restriction (PBFR) rehabilitation is the application of a tourniquet on the proximal arm or leg that is inflated to a set percentage of full blood flow occlusion with the goal to restore positive muscle quantity and quality changes. It is rapidly becoming an accepted rehabilitation modality in clinics throughout the world. What is still unknown is the effects of PBFR on pain. There is a large amount of published literature on PBFR out of academic settings that has helped in our understanding of mechanisms and application of PBFR. Unfortunately, the totality of the literature has not addressed the basic question, does PBFR create or reduce pain, since these studies were not clinical in nature. Fortunately, this practice gap is being addressed through anecdotal clinical reports and large-scale randomized control trials.
Tourniquets are used in an estimated one million surgical procedures annually in North America and the growing popularity of PBFR in the rehabilitation setting could potentially surpass surgical numbers. It is well established that prolonged tourniquet time and high-pressure gradients are associated with increased pain post-operatively. For instance, patients undergoing TKA demonstrated that tourniquet use in surgery resulted in significantly higher pain scores at 2 and 4 days postoperative versus a no tourniquet group. Tourniquet pain is described as a poorly localized, dull, tight, aching sensation at the site of tourniquet application. The pain is thought to be mediated by the unmyelinated, slow conducting C fibers that are usually inhibited by the A-delta fibers. The A-delta fibers are blocked by mechanical compression after about 30 min, while the C fibers continue to function and can exacerbate pain symptoms through the mechanical compression.
Our initial concern applying PBFR to wounded warriors who had suffered combat injuries ranging from amputation to knee reconstructions would be an increase in the patient’s pain response from the tourniquet similar to published OR tourniquet outcomes. Our initial study enrolled service members post-knee arthroscopy with two primary goals. To assess the pain response as well as the potential for thrombus formation since neither of these had been documented in the PBFR literature. Our results demonstrated a significant reduction in pain in the PBFR group after the intervention as well as no radiographic signs of thrombus formation. We repeated this trial in the upper extremity after wrist fractures and also found a significant reduction in pain in the PBFR cohort. This analgesic effect has also been found in non-operative patients with three recent studies finding reduced pain in subjects with anterior knee pain both immediately after the treatment and after 8-weeks of rehabilitation. In fact, the reduction in pain was 93% greater in anterior knee pain subjects using PBFR compared to heavy lifting controls.
Although the mechanisms behind the pain reduction are poorly understood, one simple hypothesis could be the analgesic effects of exercise. For instance, a recent study has found that exercise is as effective as analgesic drugs in relieving lower limb osteoarthritis pain. However, brief tourniquet application in the absence of exercise may also create a pain-relieving response. In subjects undergoing total knee arthroplasty, the simple inflation of a tourniquet for a short bout of time prior to surgery significantly reduced post-operative pain for days. The same study design was repeated in subjects undergoing gall-bladder removal and found reduced pain and narcotic use in subjects that received a brief tourniquet inflation prior to surgery. This has created interest in the ability of tourniquet inflation and deflation cycles, referred to as Ischemic Preconditioning or IPC, to mitigate the delayed onset muscle soreness (DOMS) after intense activity. In two recent studies, post tourniquet application in the absence of exercise significantly reduced DOMS after strenuous activity and returned strength and performance measures back to baseline levels more rapidly.
We currently have multiple clinical trials assessing the pain relief associated with PBFR. From this, clinicians may glean a better understanding of the timing, dose and appropriate patients to utilize PBFR on. Not only to restore muscle to its pre-injury level but to use PBFR prior to treatments as a way to reduce pain during rehab, prior to games to help athletes deal with nagging injuries or post-game to aide in a faster recovery. Understanding that tourniquet pressure, application and total time may be key factors in the pain response will be of upmost importance for clinical applications.