Prospective, double-blind, randomized controlled trial of electrophysiologically guided femoral nerve block in total knee arthroplasty

Yoon Seok Youm,1 Sung Do Cho,1 Chang Ho Hwang21Department of Orthopedic Surgery, 2Department of Physical Medicine and Rehabilitation, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Republic of KoreaBackground: The purpose of this study was to compare electrophysiologically guided and traditional nerve stimulator analgesia femoral nerve block after total knee arthroplasty.Methods: Patients scheduled for unilateral total knee arthroplasty were randomized to electrophysiologically guided or traditional nerve stimulator analgesia by pre-emptive single injection femoral nerve block with corresponding assistance. We assessed pain scores using a visual analog scale (VAS, 0 = no pain, 100 = the worst pain) and the volumes of morphine consumed at 4, 24, 48, and 72 hours after total knee arthroplasty.Results: Of the 60 patients enrolled, eight withdrew from the study. The remaining 52 patients were randomized to the electrophysiologically guided group (n = 27) or traditional nerve stimulator analgesia (n = 25) group. Four hours after total knee arthroplasty, VAS scores were significantly lower in the electrophysiologically guided group than in the traditional nerve stimulator group at rest (4.8 ± 1.4 versus 5.9 ± 0.8, P < 0.01) and while moving (6.2 ± 1.1 versus 6.9 ± 0.9, P < 0.01). The total volumes of morphine injected at 24, 48, and 72 hours were significantly decreased in the electrophysiologically guided group (P < 0.05 each). Variable × time interaction of VAS was significant in the electrophysiologically guided group (P < 0.05), with each VAS score at 24, 48, and 72 hours being significantly lower than the baseline score (P < 0.05). VAS scores at every time point were significantly lower in the electrophysiologically group guided than in the traditional nerve stimulator group (P < 0.05).Conclusion: Electrophysiologically guided single injection femoral nerve block may provide better postoperative analgesia and a greater reduction in the demand for pain killers than femoral nerve block using traditional nerve stimulator analgesia.Keywords: femoral nerve, nerve block, electrophysiologic concepts, arthroplasty, knee, ropivacain

Coupled Ca2+/H+ transport by cytoplasmic buffers regulates local Ca2+ and H+ ion signaling.

Ca(2+) signaling regulates cell function. This is subject to modulation by H(+) ions that are universal end-products of metabolism. Due to slow diffusion and common buffers, changes in cytoplasmic [Ca(2+)] ([Ca(2+)]i) or [H(+)] ([H(+)]i) can become compartmentalized, leading potentially to complex spatial Ca(2+)/H(+) coupling. This was studied by fluorescence imaging of cardiac myocytes. An increase in [H(+)]i, produced by superfusion of acetate (salt of membrane-permeant weak acid), evoked a [Ca(2+)]i rise, independent of sarcolemmal Ca(2+) influx or release from mitochondria, sarcoplasmic reticulum, or acidic stores. Photolytic H(+) uncaging from 2-nitrobenzaldehyde also raised [Ca(2+)]i, and the yield was reduced following inhibition of glycolysis or mitochondrial respiration. H(+) uncaging into buffer mixtures in vitro demonstrated that Ca(2+) unloading from proteins, histidyl dipeptides (HDPs; e.g., carnosine), and ATP can underlie the H(+)-evoked [Ca(2+)]i rise. Raising [H(+)]i tonically at one end of a myocyte evoked a local [Ca(2+)]i rise in the acidic microdomain, which did not dissipate. The result is consistent with uphill Ca(2+) transport into the acidic zone via Ca(2+)/H(+) exchange on diffusible HDPs and ATP molecules, energized by the [H(+)]i gradient. Ca(2+) recruitment to a localized acid microdomain was greatly reduced during intracellular Mg(2+) overload or by ATP depletion, maneuvers that reduce the Ca(2+)-carrying capacity of HDPs. Cytoplasmic HDPs and ATP underlie spatial Ca(2+)/H(+) coupling in the cardiac myocyte by providing ion exchange and transport on common buffer sites. Given the abundance of cellular HDPs and ATP, spatial Ca(2+)/H(+) coupling is likely to be of general importance in cell signaling