Cerebral microdialysis can be used to detect mitochondrial dysfunction, a potential target of neuroprotective treatment. Cyclosporin A (CsA) is a mitochondrial stabiliser that in a recent clinical stroke trial showed protective potential in patients with successful recanalisation. To investigate specific metabolic effects of CsA during reperfusion, and hypothesising that microdialysis values can be used as a proxy outcome measure, we assessed the temporal patterns of cerebral energy substrates related to oxidative metabolism in a model of transient focal ischaemia. Transient ischaemia was induced by intracerebral microinjection of endothelin-1 (150 pmol/15 µL) through stereotaxically implanted guide cannulas in awake, freely moving rats. This was immediately followed by an intravenous injection of CsA (NeuroSTAT; 15 mg/kg) or placebo solution during continuous microdialysis monitoring. After reperfusion, the lactate/pyruvate ratio (LPR) was significantly lower in the CsA group vs placebo (n = 17, 60.6 ± 24.3%, p = 0.013). Total and striatal infarct volumes (mm³) were reduced in the treatment group (n = 31, 61.8 ± 6.0 vs 80.6 ± 6.7, p = 0.047 and 29.9 ± 3.5 vs 41.5 ± 3.9, p = 0.033). CsA treatment thus ameliorated cerebral reperfusion metabolism and infarct size. Cerebral microdialysis may be useful in evaluating putative neuroprotectants in ischaemic stroke.

Cerebral micro-dialysis allows continuous sampling of extracellular metabolites, including glucose, lactate and pyruvate. Transient ischemic events cause a rapid drop in glucose and a rise in lactate levels. Following such events, the lactate/pyruvate (L/P) ratio may remain elevated for a prolonged period of time. In neurointensive care clinics, this ratio is considered a metabolic marker of ischemia and/or mitochondrial dysfunction. Here we propose a novel, sensitive microdialysis liquid chromatography-mass spectrometry (LC-MS) approach to monitor mitochondrial dysfunction in living brain using perfusion with ¹³C-labeled succinate and analysis of ¹³C-labeled tricarboxylic acid cycle (TCA) intermediates. This approach was evaluated in rat brain using malonate-perfusion (10–50 mM) and endothelin-1 (ET-1)-induced transient cerebral ischemia. In the malonate model, the expected changes upon inhibition of succinate dehydrogenase (SDH) were observed, i.e., an increase in endogenous succinate and decreases in fumaric acid and malic acid. The inhibition was further elaborated by incorporation of ¹³C into specific TCA intermediates from ¹³C-labeled succinate. In the ET-1 model, increases in non-labeled TCA metabolites (reflecting release of intracellular compounds) and decreases in ¹³C-labeled TCA metabolites (reflecting inhibition of de novo synthesis) were observed. The analysis of ¹³C incorporation provides further layers of information to identify metabolic disturbances in experimental models and neuro-intensive care patients.

Mitochondrial dysfunction after transient cerebral ischemia can be monitored by cerebral microdialysis (CMD) using changes in the lactate and pyruvate concentrations and ratio. Other metabolites associated with mitochondrial (dys)function are, e.g., tricyclic acid (TCA) and purine metabolites. Ethyl pyruvate (EP) is a putative neuroprotectant, supposedly targeting mitochondrial energy metabolism, but its effect on cerebral energy metabolism has never been described using microdialysis. In this study we monitored the metabolic effects of EP in the endothelin-1 (ET-1) rat model using perfusion with ¹³C-succinate and analysis of endogenous and ¹³C-labeled metabolites in the dialysates by liquid chromatography-mass spectrometry (LC-MS). Adult Sprague Dawley rats (n = 27 of which n = 11 were included in the study) were subjected to the microdialysis experiments. Microdialysis probes were perfused with ¹³C-labeled succinate (1 mM), and striatal dialysates were collected at 30 min intervals before induction of the insult, during intracerebral application of ET-1, and during intravenous treatment with either EP (40 mg/kg) or placebo, which was administered immediately after the insult. The rats were subjected to transient cerebral ischemia by unilateral microinjection of ET-1 in the piriform cortex, causing vasoconstriction of the medial cerebral artery. Monitoring was continued for 5 h after reperfusion, and levels of endogenous and ¹³C-labeled energy metabolites before and after ischemia-reperfusion were compared in EP-treated and control groups. Infarct volumes were assessed after 24 h. In both the EP-treated and placebo groups, ET-1-induced vasoconstriction resulted in a transient depression of interstitial glucose and elevation of lactate in the ipsilateral striatum. In the reperfusion phase, the concentrations of labeled malate, isocitrate, and lactate as well as endogenous xanthine were significantly higher in the EP-group than in the placebo-group: (mean ± SEM) labeled malate: 39.5% ± 14.9, p = 0.008; labeled isocitrate: 134.8% ± 67.9, p = 0.047; labeled lactate: 61% ± 22.0, p = 0.007; and endogenous xanthine: 93.9% ± 28.3, p = 0.0009. In the placebo group, significantly elevated levels of uridine were observed (mean ± SEM) 32.5% ± 12.7, p = 0.01. Infarct volumes were not significantly different between EP-treated and placebo groups, p = 0.4679. CMD labeled with ¹³C-succinate enabled detection of ischemic induction and EP treatment effects in the ET-1 rat model of transient focal cerebral ischemia. EP administered as a single intravenous bolus in the reperfusion-phase after transient cerebral ischemia increased de novo synthesis of several key intermediate energy metabolites (¹³C-malate, ¹³C-isocitrate, and endogenous xanthine). In summary, mitochondria process ¹³C-succinate more effectively after EP treatment.

The elderly population is expanding globally. This gives numerous challenges especially regarding hip fracture patients. In the US alone over 300.000 hip fracture patients are treated each year, and a large amount of those develop opoid addiction. Hip fractures require surgical intervention within 24 h and is associated with significant pain even at rest. Postoperative analgesic treatment need to be optimized to ensure adequate pain relief and to prevent subsequent opioid addiction. Previous studies have shown that methadone effectively decreases post-operative opioid consumption but the studies focused on younger patients undergoing elective surgery. This study focus on the use of methadone on the elderly, fragile patients undergoing acute surgery, by first determining the maximal tolerable dose. The hypothesis is the maximal tolerable doses of these hip-fracture patients lies between 0.10 mg/kg and 0.20 mg/kg. This trial aims to estimate the maximum tolerable dose of methadone when administered to elderly patients undergoing surgery for a hip fracture. This project is an adaptive dose-finding trial. The continuous reassessment method will estimate the maximum tolerable dose of methadone. The primary outcome will be respiratory depression. The statistical analysis plan will be published a priori to the closure of patient recruitment and statistical analysis of database results. The results of this study will give valuable information about the maximally tolerated dose of methadone for postoperative pain relief for elderly patients with hip fractures and potential adverse events. This trial is registered on clinicaltrials.gov with trial registration: NCT05581901. Registered 17 October 2022, https://www.clinicaltrials.gov/ct2/show/NCT05581901?term=methadone&cond = hip&draw = 2&rank = 1.

Background: Hip fractures are a source of severe pain among the elderly population and pose challenges due to limited analgesic tolerance. Perioperative methadone has shown promise in our pilot study suggesting a safe dose of 0.10 mg/kg, prompting further investigation into its benefits for elderly hip fracture patients. Methods: This study employs a double-blinded randomized controlled trial to assess the analgesic effects of a single dose of methadone during hip fracture surgery. Patients aged ≥ 60 years are consecutively enrolled and randomized to receive either perioperative methadone (treatment group) or a saline solution (placebo group). A sample size of 130 patients is required for 88% statistical power. The medication is administered intravenously at anesthesia induction and monitored until discharge. A follow-up observation is conducted 3 months post-surgery. Discussion: Primary outcome: Daily consumption of opioids within the first 3 days after surgery. Secondary outcomes include pain, mobility, nausea, vomiting, time to discharge, need for antidote, delirium, and constipation. The 3-month follow-up includes opioid use, pain, EQ-5D-5L scores, mobility, and persistent side effects. If statistically significant advantages are found in the treatment group, perioperative methadone could be considered as standard care for hip fracture patients, potentially enhancing their pain management. The study’s outcomes will provide insights into the feasibility and effectiveness of incorporating methadone into routine clinical practices for this patient group. Trial registration: ClinicalTrials.gov ID: NCT06086171, submitted 4. October 2023. EU-CT: 2023–506252-24–00, UTN: U1111-1294–6125.

Background/Objectives: Intensive postoperative pain is a common challenge after knee surgeries such as total knee arthroplasty, arthroscopy, cruciate ligament or meniscus repair, and fixation of tibial plateau or distal femoral fractures. This scoping review mapped and summarized non-regional postoperative analgesia strategies to provide an overview of available approaches when regional blocks or neuraxial anesthesia are not feasible. Methods: We followed established methodological guidance for scoping reviews and report the data in accordance with the PRISMA-ScR checklist. We searched PubMed/MEDLINE, EMBASE, Scopus, and ClinicalTrials.gov in January 2025. Eligible designs included randomized controlled trials, non-randomized trials, observational studies, case series, and pilot studies. Results: We screened 3390 records and assessed 332 in full text. A total of 43 studies met the inclusion criteria, and the literature was grouped into: (1) arthroplasty, (2) arthroscopy, (3) cruciate ligament or meniscus repair, and (4) tibial plateau or distal femoral fractures. We identified substantial heterogeneity in interventions, comparators, and outcome measures across the first three sets of literature but found no focused articles for tibial plateau or distal femoral fractures. Most studies evaluated multimodal approaches combining systemic analgesics with local periarticular or intraarticular techniques. Evidence on functional recovery and mobilization was limited. Conclusions: Current evidence on non-regional postoperative analgesia in knee surgery is fragmented and varies considerably in design, intervention, and reported outcomes. Multimodal regimens and pre-emptive NSAID use were frequently associated with reduced early postoperative pain and lower opioid requirements, although comparability across studies remains limited. As existing evidence largely focuses on outcomes during hospitalization, future research should prioritize standardized pain and functional outcome reporting and directly compare systemic and local multimodal strategies, while extending follow-up beyond discharge to better characterize sustained clinical relevance.