The Effect of Intra-articular Cocktail Versus Femoral Nerve Block for Patients Undergoing Hip Arthroscopy.

PURPOSE: To compare clinical efficacy and complication rate as measured by postoperative falls and development of peripheral neuritis between intra-articular blockade and femoral nerve block in patients undergoing arthroscopic hip surgery. METHODS: An institutional review board approved retrospective review was conducted on a consecutive series of patients who underwent elective arthroscopic hip surgery by a single surgeon, between November 2013 and April 2015. Subjects were stratified into 2 groups: patients who received a preoperative femoral nerve block for perioperative pain control, and patients who received an intra-articular "cocktail" injection postoperatively. Demographic data, perioperative pain scores, narcotic consumption, incidence of falls, and iatrogenic peripheral neuritis were collected for analysis. Postoperative data were then collected at routine clinical visits. RESULTS: A total of 193 patients were included in this study (65 males, 125 females). Of them, 105 patients received preoperative femoral nerve blocks and 88 patients received an intraoperative intra-articular "cocktail." There were no significant differences in patient demographics, history of chronic pain (P = .35), worker's compensation (P = .24), preoperative pain scores (P = .69), or intraoperative doses of narcotics (P = .40). Patients who received preoperative femoral nerve blocks reported decreased pain during their time in PACU (P = .0001) and on hospital discharge (P = .28); however, there were no statistically significant differences in patient-reported pain scores at postoperative weeks 1 (P = .34), 3 (P = .64), and 6 (P = .70). Administration of an intra-articular block was associated with a significant reduction in the rate of postoperative falls (P = .009) and iatrogenic peripheral neuritis (P = .0001). CONCLUSIONS: Preoperative femoral nerve blocks are associated with decreased immediate postoperative pain, whereas intraoperative intra-articular anesthetic injections provide effective postoperative pain control in patients undergoing arthroscopic hip surgery and result in a significant reduction in the rate of postoperative falls and iatrogenic peripheral neuritis. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Cysteine palmitoylation of the γ subunit has a dominant role in modulating activity of the epithelial sodium channel.

The epithelial sodium channel (ENaC) is composed of three homologous subunits (α, ß, and γ) with cytoplasmic N and C termini. Our previous work revealed that two cytoplasmic Cys residues in the ß subunit, ßCys-43 and ßCys-557, are Cys-palmitoylated. ENaCs with mutant ßC43A/C557A exhibit normal surface expression but enhanced Na(+) self-inhibition and reduced channel open probability. Although the α subunit is not palmitoylated, we now show that the two cytoplasmic Cys residues in the γ subunit are palmitoylated. ENaCs with mutant γC33A, γC41A, or γC33A/C41A exhibit reduced activity compared with wild type channels but normal surface expression and normal levels of α and γ subunit-activating cleavage. These mutant channels have significantly enhanced Na(+) self-inhibition and reduced open probability compared with wild type ENaCs. Channel activity was enhanced by co-expression with the palmitoyltransferase DHHC2 that also co-immunoprecipitates with ENaCs. Secondary structure prediction of the N terminus of the γ subunit places γCys-33 within an α-helix and γCys-44 on a coil before the first transmembrane domain within a short tract that includes a well conserved His-Gly motif, where mutations have been associated with altered channel gating. Our current and previous results suggest that palmitoylation of the ß and γ subunits of ENaCs enhances interactions of their respective cytoplasmic domains with the plasma membrane and stabilizes the open state of the channel. Comparison of activities of channels lacking palmitoylation sites in individual or multiple subunits revealed that γ subunit palmitoylation has a dominant role over ß subunit palmitoylation in modulating ENaC gating.