Daily Anesthesiology Research Analysis

BACKGROUND: Acupoint stimulation has been shown to reduce the risk of postoperative nausea and vomiting (PONV) after various types of surgeries involving general anesthesia, but whether the same is true after orthopaedic surgery involving spinal anesthesia is unclear. The purpose of this study was to compare PONV rates and the quality of recovery between patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) under spinal anesthesia receiving conventional antiemetics alone and those receiving antiemetics combined with use of a transcutaneous electrical acupoint stimulation bracelet (EmeTerm; WAT Medical Enterprise). METHODS: Patients at moderate or high risk for PONV, including 195 patients undergoing THA and 153 patients undergoing TKA, were randomized to receive routine antiemetics (dexamethasone and ondansetron) alone or with use of the EmeTerm bracelet. The primary outcome was the PONV incidence within 24 hours postoperatively; secondary outcomes included the rates of severe PONV, antiemetic rescue, adverse events, and Quality of Recovery scores. RESULTS: Combining antiemetics with the EmeTerm bracelet significantly reduced PONV (16.0% compared with 31.2%; p = 0.001), severe PONV (1.1% compared with 8.1%; p = 0.002), and antiemetic rescue (3.4% compared with 13.9%; p = 0.001). Use of the bracelet reduced the risk of PONV within 24 hours by 61% (adjusted hazard ratio, 0.39; 95% confidence interval [CI], 0.24 to 0.63), and its benefit became significant at 0 to 3 and 3 to 6-hour intervals after surgery. The complete response rate was higher for the bracelet + antiemetics group compared with the group with antiemetics alone (84.0% compared with 68.8%; p = 0.001), with better Quality of Recovery scores at 24 hours in the bracelet + antiemetics group. CONCLUSIONS: The EmeTerm bracelet enhanced the efficacy of antiemetics in reducing PONV after THA and TKA under spinal anesthesia and may improve short-term recovery. LEVEL OF EVIDENCE: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

IMPORTANCE: Arthroprosthetic metal exposure has been linked to neurological dysfunction, but evidence of central nervous system exposure is largely missing. OBJECTIVE: To compare levels of all arthroplasty-relevant metals in cerebrospinal fluid (CSF), whole blood, and serum of patients with and without large joint replacement. DESIGN, SETTING, AND PARTICIPANTS: The NeuroWear pilot study was a single-site hospital-based cross-sectional study conducted between April 2018 and November 2019. Laboratory personnel and investigators were blinded to group allocation. Patients presenting for elective surgery under spinal anesthesia and patients scheduled for lumbar puncture at a university medical center were eligible for inclusion. Patients aged 18 years and older with at least 1 large joint replacement in situ (103 case participants) and age- and sex-matched arthroplasty-naive patients (108 control participants) were recruited. One case and 6 control participants were excluded. Each case participant was matched with 1 control participant to achieve equal self-reported sex and a minimal age difference. The data analyses were performed between May 2023 and February 2024. EXPOSURE: Presence of large joint replacement. MAIN OUTCOMES AND MEASURES: CSF, whole blood, and serum levels of aluminum, cobalt, chromium, molybdenum, nickel, niobium, tantalum, titanium, vanadium, and zirconium were quantified. RESULTS: A total of 204 patients (118 [58%] women and 86 [42%] men; median [range] age 69.4 [21.3-93.1] years) were included for metal analyses. In CSF, median (range) cobalt levels were significantly higher in the implant group (0.03 [0.01-0.64] μg/L) compared with the control group (0.02 [0.01-0.19] μg/L). Cobalt levels in CSF were significantly correlated with cobalt levels in serum (r = 0.72; 95% CI, 0.53-0.85) and whole blood (r = 0.82; 95% CI, 0.62-0.92). Significantly higher whole blood median (range) levels of cobalt (implant: 0.27 [0.07-24.10] μg/L; control: 0.16 [0.08-0.99] μg/L), chromium (implant: 0.47 [0.24-4.76] μg/L; control: 0.42 [0.21-1.52] μg/L), titanium (implant: 8.05 [1.14-37.20] μg/L; control: 7.15 [1.80-20.70] μg/L), niobium (implant: 0.02 [0.01-1.14] μg/L; control: 0.01 [0.01-0.11] μg/L), and zirconium (implant: 0.05 [0.01-39.90] μg/L; control: 0.03 [0.01-1.95] μg/L) were detected. Patients with an implant were found to have significantly higher median (range) CSF metal levels for titanium (implant: 0.75 [0.12-1.40] μg/L; control: 0.57 [0.13-1.10] μg/L), niobium (implant: 0.02 [0.01-0.16] μg/L; control: 0.01 [0.01-0.03] μg/L), and zirconium (implant: 0.05 [0.01-0.44] μg/L; control: 0.04 [0.01-0.28] μg/L) if those metal levels were elevated in serum. Patients with cobalt-chromium-molybdenum implant components exhibited significantly higher median (range) chromium levels in CSF than control participants (implant: 0.31 [0.02-2.05] μg/L; control: 0.23 [0.02-1.10] μg/L). CONCLUSIONS AND RELEVANCE: In this cross-sectional study, chronic exposure to arthroplasty implants was associated with corresponding metal accumulation in blood and CSF. Arthroprosthetic cobalt, chromium, titanium, niobium, and zirconium seemed to cross neural barriers and accumulate in CSF. Correlation analyses suggested cobalt-specific transport mechanisms across neural barriers. In view of the neurotoxic effects of cobalt, subsequent studies are needed to determine whether CSF metal concentrations correlate with objective measures of neurotoxic effects and whether this may be of relevance, particularly in patients with new-onset or rapid deterioration of neurological conditions following arthroplasty.

BACKGROUND: Postoperative delirium (POD) is a common and serious clinical condition that occurs after anesthesia/surgery. While its clinical impact is well recognized, the underlying electrophysiologic mechanisms remain largely unknown, posing challenges for effective treatment. This study aims to investigate hippocampal neural dynamics before and after anesthesia/surgery in aged mice, which have a tendency to develop POD. METHODS: This study included adult and aged mice with a POD model. POD-like behavior was assessed in N = 10 mice at baseline (the day before surgery), as well as at 9 h and 24 h after anesthesia/surgery. A behavioral battery, including the open field test, Y maze, buried food test, and novel object recognition, was used for assessment. In vivo chronic brain recordings were performed on awake, restrained mice using a high-density silicon probe during the same time intervals. To further investigate hippocampal neural dynamics, in vivo two-photon calcium imaging was also conducted. Additionally, aged mice were pretreated with indole-3-propionic acid (IPA), and its effects on POD-like behavior and neural activity were evaluated using electrophysiology and calcium imaging. RESULTS: The first observation was that aged mice exhibited significant POD-like behavior, as measured by Z scores, compared to adult mice after anesthesia/surgery. Analysis revealed significant age-related differences in hippocampal neuronal activities. At 9 h after surgery, aged mice exhibited a marked increase in pyramidal cell activity and a reduction in interneuron activity compared to adult mice. These changes in neuronal dynamics were associated with the onset of POD-like symptoms in aged mice. By 24 h after surgery, both pyramidal cell and interneuron activity in aged mice had returned to presurgery levels, which coincided with an improvement in POD-like behavior. Additionally, IPA pretreatment modulated neuronal activity in aged mice, attenuating pyramidal cell hyperactivity and partially ameliorating interneuron dysfunction, changes associated with mitigated POD-like behavior. CONCLUSIONS: Alterations in hippocampal neural activity may significantly contribute to brain dysfunction and POD-like behavior. IPA pretreatment may modulate neural circuit imbalances in aged mice, potentially mitigating POD incidence.