Neurosteroid dehydroepiandrosterone sulphate enhances pain transmission in rat spinal cord dorsal horn.

BACKGROUND: The neurosteroid dehydroepiandrosterone sulphate (DHEAS) activates the sigma-1 receptor, inhibits gamma-aminobutyric acid A (GABAA) and glycine receptors, and induces hyperalgesic effects. Although its effects have been studied in various tissues of the nervous system, its synaptic mechanisms in nociceptive pathways remain to be elucidated. METHODS: The threshold of mechanical hypersensitivity and spontaneous pain behaviour was assessed using the von Frey test in adult male Wistar rats after intrathecal administration of DHEAS. We also investigated the effects of DHEAS on synaptic transmission in the spinal dorsal horn using slice patch-clamp electrophysiology. RESULTS: Intrathecally administered DHEAS elicited dose-dependent mechanical hyperalgesia and spontaneous pain behaviours (withdrawal threshold: saline; 51.0 [20.1] g, 3 µg DHEAS; 14.0 [7.8] g, P<0.01, 10 µg DHEAS; 6.9 [5.2] g, 15 min after administration, P<0.001). DHEAS at 100 µM increased the frequency of miniature postsynaptic currents in the rat dorsal spinal horn; this increase was extracellular Ca2+-dependent but not sigma-1 and N-methyl-d-aspartate receptor-dependent. DHEAS suppressed the frequency of miniature inhibitory postsynaptic currents in a GABAA receptor- and sigma-1 receptor-dependent manner. CONCLUSIONS: These results suggest that DHEAS participates in the pathophysiology of nociceptive synaptic transmission in the spinal cord by potentiation of glutamate release and inhibition of the GABAA receptor.

[Efficacy of repeated subcostal transversus abdominis plane blocks with 0.2% lidocaine via 18-gauge intravenous catheters for patients undergoing abdominal aortic aneurism surgery].

BACKGROUND: There is an increasing number of patients scheduled for abdominal aortic aneurysm resection in whom epidural anesthesia cannot be performed because of concomitant antiplatelet/anticoagulant therapy. Instead of epidural anesthesia for postoperative analgesia in such patients it is possible to use repeated bilateral subcostal transversus abdominis plane (TAP) blocks. METHODS: Four patients receiving antiplatelet/anticoagulant therapy for abdominal aortic aneurysm resection under general anesthesia were studied. After the completion of surgery and before emergence from anesthesia 18-gauge intravenous catheters were inserted bilaterally into subcostal TAP and 100 ml (50 ml on each side) of 0.2% lidocaine with 1/500,000 epinephrine were injected via the catheters twice daily until the second postoperative day. Pain intensity was assessed using a 0-10 numerical rating scale at rest and during movement, before and after each block. RESULTS: Numerical pain ratings at rest and during movement decreased after each block, and good analgesia was obtained. No complications such as nausea, vomiting or infection were observed in the postoperative period. CONCLUSIONS: These findings suggest that repeated bilateral subcostal TAP blocks with 0.2% lidocaine performed via 18-gauge intravenous catheters provide good postoperative analgesia after abdominal aortic aneurysm resection.