Addition of buprenorphine to local anesthetic in adductor canal blocks after total knee arthroplasty improves postoperative pain relief: a randomized controlled trial.

BACKGROUND AND OBJECTIVES: For the hundreds of thousands of patients who undergo total knee arthroplasty (TKA) in the United States each year, early mobilization has been demonstrated to improve functional outcomes and reduce complications. Management of postoperative pain is a critical factor in achieving early mobilization. Recent studies have shown that the use of an adductor canal block (ACB) after TKA results in increased preservation of quadriceps muscle strength, without significant difference in postoperative pain when compared to femoral nerve block. This increased preservation of quadriceps muscle strength leads to earlier mobilization. Studies have also demonstrated a prolongation of analgesia with the addition of buprenorphine to local anesthetic for regional block placement. This study examined the effect on postoperative opioid consumption when adding buprenorphine to an ACB vs an ACB with local anesthetic alone, for postoperative analgesia after unilateral TKA. METHODS: A total of 100 patients scheduled for TKA were randomized to receive postoperative ACB with local anesthetic alone or with local anesthetic and buprenorphine. The primary outcome examined was total opioid analgesic (milligrams of hydrocodone equivalent) consumption in the first 24 hours postsurgery. The secondary outcomes examined were the reported incidence of the opioid side effects nausea, vomiting, and pruritis. RESULTS: Postoperative opioid consumption decreased significantly in the group that received an ACB with local anesthetic and buprenorphine compared to an ACB with local anesthetic only (25.34±2.62 vs 35.84±2.86; P=.0076). Secondary outcomes showed no statistical difference between the 2 groups in terms of the incidence of nausea, vomiting, or pruritus. CONCLUSION: The addition of buprenorphine to an adductor canal block decreases postoperative opioid consumption when compared to an ACB with local anesthetic alone. This reduction in opioid consumption, without significant increase in side effects, makes this an attractive anesthetic adjunct for TKA.

Drilling to gabbro in intact ocean crust.

Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.