Case Report: Two-Center Case Series of Motor-Sparing Nerve Blocks comprised of Preservative-Free Midazolam-Buprenorphine-Clonidine-Dexamethasone

Brian A. Williams ^1,2* Marsha Ritter Jones ^1,2 Patrick J. Kennedy ² Alissa M. Kmatz ² Leath R. Abdullah ² Rick L. Scanlan ² Nicholas J. McNiffe ³ William M. Fowler ⁴ Michael S. Patzkowski ^3,5,6

• ¹ University of Pittsburgh, Pittsburgh, United States
• ² VA Pittsburgh Healthcare System, Veterans Health Administration, United States Department of Veterans Affairs, Pittsburgh, Pennsylvania, United States
• ³ Brooke Army Medical Center, San Antonio, Texas, United States
• ⁴ Walter Reed National Military Medical Center, Bethesda, Maryland, United States
• ⁵ Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States
• ⁶ Defense Health Agency (DHA), Silver Spring, Maryland, United States

The four individual cases presented include three clinical scenarios where the operating surgeon, on behalf of the surgical patient, desired focal "conduction analgesia" without motor block, to facilitate postoperative physical examination and/or immediate advancement of physical therapy/ambulation objectives during early convalescence. The two centers' authors opted for available pharmacologic motor-sparing nerve blocks (entailing motor-sensory nerve fiber analgesia without the use of typical local anesthetics), as opposed to commonplace anatomic motor-sparing nerve blocks (involving local anesthetics which block sodium channels, but with no motor nerve fibers targeted). Three of the four cases involved an acute postoperative timeline, and the fourth entailed an outpatient physical exam 6 months postoperatively in a patient with chronic persistent surgical pain that was soon after diagnosed with complex regional pain syndrome (CRPS). The intervention was a 4-medication motor-sparing nerve block (midazolam-buprenorphine-clonidine-dexamethasone) that had been previously reported. All four patients were satisfied with the short-term analgesic outcomes, and the surgeons' physical therapy and related objectives were met via the avoidance of motor block. In the latter case which was later diagnosed with CRPS, the surgeon determined on physical exam that bony and soft-tissue healing was appropriate, obviating the need for repeat surgical exploration, thus allowing for earlier chronic pain consultant referral for (ultimately) CRPS management. The described 4-medication preservative-free perineural combination, previously shown to be nontoxic in vitro and in vivo, may have important clinical application when motor-sparing analgesia is desired in varying contexts and extremes of postsurgical pain. The presentations of these four cases are followed by an aggregate data summary (n=305 cases) of analgesic duration (mean 30.5 hr, 95% CI 28.5-32.5 hr), and pre-/post-intervention peak pain scores (Pre: mean 7.8/10 [95% CI 7.5-8.0]; Post: mean 6.3/10 [95% CI 6.0-6.6]) after the described 4-drug nerve block intervention, derived from quality improvement data at one of the two contributing authorcenters.