Daily Anesthesiology Research Analysis

BACKGROUND: The majority of dorsal root ganglion neurons are excitatory glutamatergic neurons. Recent studies suggest that a subset of dorsal root ganglion neurons are able to synthesize γ-aminobutyric acid (GABA) and are immunoreactive to vesicular GABA transporter (Vgat) that packages GABA into the synaptic vesicles critical for inhibitory neurotransmission. The current study aimed to investigate the spinal circuits innervated by these Vgat+ primary sensory neurons and interrogate the role of Vgat+ primary sensory neurons in nociceptive modification. METHODS: The authors used viral tracings, immunohistochemistry, patch clamp electrophysiologic recordings, optogenetics, chemogenetics, and behavioral assays in male Vgat-Cre mice to dissect the anatomical connectivity and function of Vgat+ primary sensory neurons. RESULTS: The data showed that the central terminals of Vgat+ primary sensory neurons made inhibitory connections with spinal cord somatostatin-positive excitatory interneurons and meanwhile formed glutamatergic connections with local GABAergic interneurons driving feedforward inhibition. The functional dichotomy of Vgat+ primary sensory neurons constituted an inhibitory spinal circuit that prevented aversive and pain-like responses of mice to innocuous or noxious mechanical stimuli. After peripheral nerve injury, the reduction of inhibitory drive from Vgat+ primary sensory neurons to spinal somatostatin-positive interneurons correlated with mechanical nociceptive sensitization. Optogenetic or chemogenetic stimulation of Vgat+ primary sensory neurons effectively alleviated the nerve injury-induced hypersensitivity to mechanical stimulation. CONCLUSIONS: The data suggested that the Vgat+ primary sensory neurons innervating a discrete spinal microcircuit were ideally suited to suppress the mechanical pain transmission.

INTRODUCTION: Adequate postoperative pain control is crucial for rehabilitation after open thoracotomy. The aim of this systematic review was to update the previous procedure-specific postoperative pain management recommendations for patients undergoing open thoracotomy. METHODS: Using previously reported PROSPECT methodology, we performed a systematic review of randomised controlled trials, systematic reviews and meta-analyses evaluating pain interventions for open thoracotomy published between 2015 and 2024. Data extracted from the included studies were evaluated by an expert subgroup that considered the relevance of the studied interventions in clinical practice and their risk/benefit profile. Recommendations were finalised after review and comments by all members of the PROSPECT working group using a modified Delphi approach. The Cochrane Risk of bias tool 2 was used to grade the quality of evidence. RESULTS: Overall, 100 studies were included. Based on the available evidence, either thoracic epidural analgesia or paravertebral blockade should be provided as a first-line analgesic intervention for open thoracotomy. Erector spinae plane, rhomboid intercostal or intercostal nerve blockade could be used as a second-line regional analgesia intervention. In addition, patients should receive basic analgesia consisting of paracetamol and non-steroidal anti-inflammatory drugs or cyclo-oxygenase-2 selective inhibitors. Acupuncture or cryoanalgesia is recommended when regional analgesia cannot be performed, albeit with a low level of supportive evidence. The choice of surgical technique, postoperative physiotherapy and approach to patient education should be based on outcomes other than pain control. DISCUSSION: In these updated guidelines on pain management after open thoracotomy, the main changes concern the recommendation of either thoracic epidural analgesia or paravertebral blockade as the first-line intervention according to patient and clinician preference, combined with basic systemic analgesia. The use of other regional blocks should be limited to patients who cannot receive thoracic epidural analgesia or paravertebral blockade. WHAT WE DID: The researchers searched through many medical studies done between 2015 and 2024. They found and carefully studied 100 different research papers from trusted medical databases. Experts then worked together to decide which pain treatments were the safest and most effective. WHY WE DID IT: When someone has an open thoracotomy, it means they have surgery where doctors open the chest to reach the lungs or heart. After this kind of surgery, people often have a lot of pain. Good pain control is very important so that patients can breathe deeply, move around and get better faster. This study looked at the best ways to manage pain after open thoracotomy. WHAT WE FOUND: They recommend two main ways to control pain: thoracic epidural analgesia, which delivers medicine near the spinal cord to block pain, and paravertebral blockade, which numbs the nerves next to the spine that send pain signals from the chest. These are the first‐choice treatments because they work best for most patients. If these cannot be used, doctors can try other methods like erector spinae plane block, rhomboid intercostal block or intercostal nerve block. These are called second‐line treatments. Patients should also take basic pain medicines, such as paracetamol and non‐steroidal anti‐inflammatory drugs, or cyclooxygenase‐2 inhibitors to help with general pain and swelling. If regional pain blocks cannot be done, acupuncture or cryoanalgesia (freezing the nerves to stop pain) might help, though there is less scientific proof for these options. The choice of operation, physiotherapy and patient education should focus on things other than pain alone, like recovery and movement.

IMPORTANCE: Prior research conducted in private for-profit health care systems has suggested that social determinants of health (SDOH) play a role in adverse postoperative outcomes. Whether these findings translate to universal health care systems is unknown. OBJECTIVE: To quantify the association of SDOH with risk of 30-day mortality after scheduled inpatient surgery. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was conducted in Ontario, Canada's most populous province. The cohort included consecutive adult patients (aged ≥18 years) who were eligible for Ontario's universal health insurance and underwent a scheduled inpatient surgical procedure between January 1, 2017, and December 31, 2023. Diagnostic and procedural, demographic, vital statistics, and other data were obtained from linked health administrative databases. EXPOSURES: SDOH including neighborhood income, immigration status, and migration recency. MAIN OUTCOME AND MEASURE: Death within 30 days of index surgery. Logistic regression models were used to estimate the adjusted and unadjusted odds ratios (AORs and ORs) of the association of each SDOH with 30-day mortality. RESULTS: Overall, 1 036 759 patients (median [IQR] age, 66 [56-74] years; 526 158 females [50.8%]) who underwent a range of scheduled inpatient surgical procedures were included. Of these patients, 1780 (0.9%) from the lowest-income areas died, as did 1307 (0.6%) from the highest-income areas. Patients from the lowest-income areas were at 52.0% increased odds of death (OR, 1.52; 95% CI, 1.42-1.64) compared with those from the highest-income areas. This association persisted with models partially adjusted for demographic and procedural factors (AOR, 1.54; 95% CI, 1.44-1.66) and fully adjusted for comorbidities (AOR, 1.43; 95% CI, 1.33-1.54). A dose-response association was demonstrated between neighborhood income and mortality, with odds of death increasing with diminishing income (eg, quintile 3 vs quintile 5: AOR, 1.18 [95% CI, 1.10-1.27]; quintile 2 vs quintile 5: AOR, 1.32 [95% CI, 1.22-1.42]). There was evidence of effect modification of the association between neighborhood income and mortality by procedure complexity (eg, effect estimate for quintile 4 and high complexity: -0.0776 [95% CI, -0.2722 to 0.1169]; P = .002). Immigrant and refugee status and recent migration (<5 years) demonstrated reduced odds of mortality in unadjusted analyses, but these associations diminished with risk adjustment. CONCLUSIONS AND RELEVANCE: In this cohort study, residency in lowest-income neighborhood was associated with increased risk of postoperative mortality despite adjustment for patient, procedure, and hospital factors. Improving postoperative outcomes likely requires addressing underlying SDOH disparities.