Serotonin Plays a Key Role in the Development of Opioid-Induced Hyperalgesia in Mice.

Opioid usage for pain therapy is limited by its undesirable clinical effects, including paradoxical hyperalgesia, also known as opioid-induced hyperalgesia (OIH). However, the mechanisms associated with the development and maintenance of OIH remain unclear. Here, we investigated the effect of serotonin inhibition by the 5-HT3 receptor antagonist, ondansetron (OND), as well as serotonin deprivation via its synthesis inhibitor para-chlorophenylalanine, on mouse OIH models, with particular focus on astrocyte activation. Co-administering of OND and morphine, in combination with serotonin depletion, inhibited mechanical hyperalgesia and astrocyte activation in the spinal dorsal horn of mouse OIH models. Although previous studies have suggested that activation of astrocytes in the spinal dorsal horn is essential for the development and maintenance of OIH, herein, treatment with carbenoxolone (CBX), a gap junction inhibitor that suppresses astrocyte activation, did not ameliorate mechanical hyperalgesia in mouse OIH models. These results indicate that serotonin in the spinal dorsal horn, and activation of the 5-HT3 receptor play essential roles in OIH induced by chronic morphine, while astrocyte activation in the spinal dorsal horn serves as a secondary effect of OIH. Our findings further suggest that serotonergic regulation in the spinal dorsal horn may be a therapeutic target of OIH. PERSPECTIVE: The current study revealed that the descending serotonergic pain-facilitatory system in the spinal dorsal horn is crucial in OIH, and that activation of astrocytes is a secondary phenotype of OIH. Our study offers new therapeutic targets for OIH and may help reduce inappropriate opioid use.

Preoperative Implementation of Transverse Thoracic Muscle Plane Block and Rectus Sheath Block Combination for Pediatric Cardiac Surgery.

Systemic intravenous administration of opioids is the main treatment strategy for intraoperative and postoperative pain management in patients undergoing cardiac surgery with sternotomy. However, using lower doses of opioids may achieve the well-established benefits of the fast-track approach, with minimal opioid-related side effects. Postoperative pain is coupled with a long stay in the intensive care unit. Although neuraxial anesthesia has some benefits, its use remains controversial due to the potential development of epidural hematoma after anticoagulation for cardiopulmonary bypass and coagulopathy after cardiac surgery. Therefore, there is a need for other effective postoperative analgesic strategies, such as peripheral nerve blocks other than neuraxial anesthesia, for cardiac surgery with sternotomy. The effects of real-time ultrasound-guided transverse thoracic muscle plane (TTP) block on postoperative pain after sternotomy have been reported; however, the pain and discomfort in the epigastric area caused by chest drainage tubes placed through the rectus abdominis muscle also are major postoperative problems after cardiac surgery. Herein, the authors report on a preoperative combination of TTP block and rectus sheath block (RSB) for postoperative pain management after cardiac surgery with sternotomy that addresses pain in both the chest and epigastric areas. Considering previous studies, it is presumed that preemptive analgesic effects can be expected via a combination of the TTP block and RSB, and indeed, the preemptive effect was observed in the present study's patients. In this article, the procedure and tips for combining the TTP block and RSB are introduced.

A novel parameter for pulmonary blood flow during palliative procedures: velocity time integral of the pulmonary vein†.

OBJECTIVES: The main goal of palliative procedures for congenital heart defects is adequate pulmonary blood flow (PBF), but precise intraoperative PBF evaluation is sometimes difficult. The purpose of this preliminary study was to investigate the usefulness of velocity time integral of the pulmonary vein (PV-VTI) measured by transoesophageal echocardiography (TOE) at the time of palliative procedure as a parameter for PBF. METHODS: Case histories of 63 patients who underwent palliative procedures (bilateral pulmonary artery banding in 18 patients, main pulmonary artery banding in 22 patients and systemic-to-pulmonary artery shunt in 23 patients) and whose intraoperative PV-VTI was measured by TOE from 2011 to 2017 at our centre were retrospectively reviewed. Low-body-weight infants, cases in which cardiopulmonary bypass was used and cases that were anatomically difficult to measure were excluded. RESULTS: PV-VTIs measured at 4 orifices of the pulmonary veins were all significantly decreased in both the bilateral pulmonary artery banding and main pulmonary artery banding groups and increased in the systemic-to-pulmonary artery shunt group immediately after the procedure. There were significant correlations between the velocity time integrals of both right and left pulmonary veins and arterial oxygen saturation (r = 0.564 and 0.703). Nine patients (6 bilateral pulmonary artery banding and 3 systemic-to-pulmonary artery shunt) required unplanned early reoperation due to inadequate PBF; their PV-VTIs were significantly different from those of patients not requiring reoperation. No major complications related to TOE occurred postoperatively. CONCLUSIONS: The PV-VTI measured by TOE during palliative procedures reflected the change of PBF and could help identify patients at higher risk of early reoperation due to inadequate PBF. This parameter may be a useful additional tool for evaluating intraoperative PBF.

Anesthetic management of a patient with a giant ovarian tumor containing 83 l of fluid.

We report the anesthetic management of a patient scheduled for tumor resection with a giant ovarian tumor containing 83 l of fluid. A 59-year-old woman [height 154 cm; weight 146 kg (ideal: 52 kg)] with a giant ovarian tumor was scheduled for tumor resection. Her preoperative abdominal circumference was 194 cm, which made supine positioning difficult. The thoracoabdominal computed tomography revealed a right giant cystic ovarian tumor with an estimated mass of 100 kg. Evidence of malignant tumor was not observed. In the operation room, she was intubated using a video laryngoscope (Airway Scope®, Hoya, Tokyo, Japan) in a semirecumbent position under conscious sedation. Following general anesthesia, the tumor fluid was gradually aspirated at a rate of 500 ml/min, and during this procedure, spontaneous respiration was preserved with pressure support ventilation. After the fluid was drained, the tumor was resected in a supine position. There were no major perioperative complications in hemodynamic and respiratory status, such as supine hypotensive syndrome or re-expansion pulmonary edema. Her weight decreased to 50 kg postoperatively. Maintenance of spontaneous respiration and slow aspiration of the tumor fluid prevented respiratory and hemodynamic failure and resulted in safe anesthesia management during giant ovarian tumor resection.