Conditioned Pain Modulation: Comparison of the Effects on Nociceptive and Non-nociceptive Blink Reflex.

Although conditioned pain modulation (CPM) is considered to represent descending pain inhibitory mechanisms triggered by noxious stimuli applied to a remote area, there have been no previous studies comparing CPM between pain and tactile systems. In this study, we compared CPM between the two systems objectively using blink reflexes. Intra-epidermal electrical stimulation (IES) and transcutaneous electrical stimulation (TS) were applied to the right skin area over the supraorbital foramen to evoke a nociceptive or a non-nociceptive blink reflex, respectively, in 15 healthy males. In the test session, IES or TS were applied six times and subjects reported the intensity of each stimulus on a numerical rating scale (NRS). Blink reflexes were measured using electromyography (R2). The first and second sessions were control sessions, while in the third session, the left hand was immersed in cold water at 10 °C as a conditioning stimulus. The magnitude of the R2 blink and NRS scores were compared among the sessions by 2-way ANOVA. Both the NRS score and nociceptive R2 were significantly decreased in the third session for IES, with a significant correlation between the two variables; whereas, TS-induced non-nociceptive R2 did not change among the sessions. Although the conditioning stimulus decreased the NRS score for TS, the CPM effect was significantly smaller than that for IES (p = 0.002). The present findings suggest the presence of a pain-specific CPM effect to a heterotopic noxious stimulus.

Clinical Benefit of Preoperative Exercise and Nutritional Therapy for Patients Undergoing Hepato-Pancreato-Biliary Surgeries for Malignancy.

BACKGROUND: The impact of prehabilitation on physical fitness and postoperative course after hepato-pancreato-biliary (HPB) surgeries for malignancy is unknown. The current study aimed to investigate the effect of preoperative exercise and nutritional therapies on nutritional status, physical fitness, and postoperative outcomes of patients undergoing an invasive HPB surgery for malignancy. METHODS: Patients who underwent open abdominal surgeries for HPB malignancies (major hepatectomy, pancreatoduodenectomy, or hepato-pancreatoduodenectomy) between 2016 and 2017 were subjected to prehabilitation. Patients before the introduction of prehabilitation were included as historical control subjects for 1:1 propensity score-matching (no-prehabilitation group). The preoperative nutritional status and postoperative course were compared between the two groups. RESULTS: The prehabilitation group consisted of 76 patients scheduled to undergo HPB surgeries for malignancy. An identical number of patients were selected as the no-prehabilitation group after propensity score-matching. During the waiting period, serum albumin levels were significantly deteriorated in the no-prehabilitation group, whereas this index did not deteriorate or even improved in the prehabilitation group. By performing prehabilitation, a 6-min walk distance and total muscle/fat ratio were significantly increased during the waiting period. Although the overall incidence of postoperative complications did not differ between the two groups, the postoperative hospital stay was shorter in the prehabilitation group than in the no-prehabilitation group (median, 23 vs 30 days; p = 0.045). CONCLUSION: The introduction of prehabilitation prevented nutritional deterioration, improved physical fitness before surgery, and shortened the postoperative hospital stay for the patients undergoing HPB surgeries for malignancy.

Important role of calcium chloride in preventing carbon monoxide generation during desflurane degradation with alkali hydroxide-free carbon dioxide absorbents.

We investigated whether calcium chloride (CaCl2), a supplementary additive in carbon dioxide (CO2) absorbents, could affect carbon monoxide (CO) production caused by desflurane degradation, using a Japanese alkali-free CO2 absorbent Yabashi Lime®-f (YL-f), its CaCl2-free and 1% CaCl2-added derivatives, and other commercially available alkali-free absorbents with or without CaCl2. The reaction between 1 L of desflurane gas (3-10%) and 20 g of desiccated specimen was performed in an artificial closed-circuit anesthesia system for 3 min at 20 or 40 °C. The CO concentration was measured using a gas chromatograph equipped with a semiconductor sensor detector. The systems were validated by detecting dose-dependent CO production with an alkali hydroxide-containing CO2 absorbent, Sodasorb®. Compared with YL-f, the CaCl2-free derivative caused the production of significantly more CO, while the 1% CaCl2-added derivative caused the production of a comparable amount of CO. These phenomena were confirmed using commercially available absorbents AMSORB® PLUS, an alkali-free absorbent with CaCl2, and LoFloSorb™, an alkali-free absorbent without CaCl2. These results suggest that CaCl2 plays an important role in preventing CO generation caused by desflurane degradation with alkali hydroxide-free CO2 absorbents like YL-f.

A randomized controlled trial comparing paravertebral block via the surgical field with thoracic epidural block using ropivacaine for post-thoracotomy pain relief.

PURPOSE: We conducted a comparative study to evaluate analgesic efficacy between paravertebral block via the surgical field (PVB-sf), in which the catheter was inserted into the ventral side of the sympathetic trunk in the paravertebral space by a thoracic surgeon under thoracoscopic visualization, and epidural block (Epi) using ropivacaine for post-thoracotomy pain relief. METHODS: Lung cancer patients scheduled for lobectomy via thoracotomy were randomly allocated to receive either PVB-sf or Epi (n = 36 per group). Before thoracotomy closure, 0.375% ropivacaine was administered as a bolus (PVB-sf, 20 mL; Epi, 5 mL), followed by a 300-mL continuous infusion of 0.2% ropivacaine at 5 mL/h. Postoperative pain was assessed using a visual analog scale (VAS) score at various time points, including the primary endpoint of 2 h after ropivacaine bolus injection. Sensory block area, vital signs, serum ropivacaine concentrations, and side effects were also evaluated. RESULTS: The Epi group showed significantly lower VAS scores and blood pressure and a wider sensory block area than the PVB-sf group at all evaluation time points. While the mean serum ropivacaine concentration in the PVB-sf group was significantly higher than that in the Epi group until 1 h after injection of the ropivacaine bolus, there was no significant difference at any subsequent assessment point. The incidence of side effects was similar between the groups. CONCLUSION: The Epi was superior to PVB-sf for the management of post-thoracotomy pain in this patient cohort. The number of dermatomes anaesthetized by Epi was greater than that anaesthetized by PVB-sf. No difference in complication rates was observed between the two groups.

Spinal cord stimulation markedly ameliorated refractory neuropathic pain in transthyretin Val30Met familial amyloid polyneuropathy.

Although spinal cord stimulation has been reported to be effective for controlling neuropathic pain in diabetic neuropathy, it has rarely been investigated in other peripheral neuropathies. We describe, for the first time, the efficacy of spinal cord stimulation for refractory neuropathic pain in a patient with transthyretin Val30Met associated familial amyloid polyneuropathy (FAP ATTR Val30Met). A 72-year-old man was diagnosed as having FAP ATTR Val30Met when he was 70 years old. He had been complained of burning pain in the distal portion of his bilateral lower limbs since he was 69 years old. Because conventional symptomatic therapies, including nonsteroidal anti-inflammatory drugs, antiepileptic drugs, and tricyclic antidepressants did not ameliorate pain, he underwent bilateral lumbar spinal cord electrical stimulation at high frequency and low voltage at the level of Th12 vertebral body and this was markedly effective. Our case expands the application of spinal cord stimulation, which should be considered as an alternative therapeutic approach for relief of neuropathic pain, which can be extremely distressful for patients and may lead to an impaired quality of life.

Preliminary measurement of intraoperative sympathetic nerve activity using microneurography and laser Doppler flowmetry during surgical resection of suprasellar tumors.

Intraoperative microneurography (enabling direct measurement of sympathetic outflow) and laser Doppler flowmetry were used to measure skin sympathetic nerve activity (SSNA) and skin blood flow (SBF) as indicators of hypothalamic damage during resection of 12 suprasellar tumors, 6 craniopharyngiomas, 4 meningiomas, 1 pituitary adenoma, and 1 germ cell tumor. SSNA was measured from a tungsten microelectrode inserted into the peroneal nerve, and SBF was measured from the foot innervated by the peroneal nerve. SBF reduction was induced by nociceptive procedures and non-nociceptive procedures before tumor exposure, on exposed tumors, and directly on the hypothalamus. SSNA could be reliably recorded in only 4 patients because of technical difficulties. In these patients, SSNA bursts appeared, followed by SBF reduction. The number of SSNA bursts was 37% to 100% of the number of SBF reduction events. Various surgical procedures involving painful stimuli or mechanical stress on the hypothalamus induced SSNA bursts and SBF reduction. The present findings suggest that SSNA and SBF can be used to detect sympathetic nerve activity, as an indicator of hypothalamic function, during neurosurgical procedures.