Activation of Transient Receptor Potential Vanilloid 1 Is Involved in Both Pain and Tumor Growth in a Mouse Model of Cancer Pain.

Activation of calcitonin gene-related peptide (CGRP)-positive sensory neurons in the tumor microenvironment has been shown to be involved in tumor growth. However, how CGRP-positive sensory neurons are activated requires elucidation. In this study, we focused on transient receptor potential vanilloid 1 (TRPV1) and examined the contribution of TRPV1 to tumor growth and cancer pain in a mouse cancer model in which Lewis lung carcinoma was subcutaneously inoculated in the left plantar region. Tumor inoculation gradually increased the volumes of the hind paws of wild type (WT) mice over time, but those of both αCGRP knockout mice and TRPV1 knockout mice were significantly smaller than those of WT mice after tumor inoculation. Both TRPV1 and CGRP are therefore suggested to be involved in tumor growth. In an immunohistochemical study, the percentage of phosphorylated cyclic adenosine monophosphate response element-binding protein (p-CREB)-positive profiles in CGRP-positive dorsal root ganglion (DRG) neurons in WT mice was significantly increased after tumor inoculation. The percentage of p-CREB-positive profiles in CGRP-positive DRG neurons in TRPV1 knockout mice was also increased after tumor inoculation, but was significantly lower than that in WT mice, indicating the contribution of TRPV1 to activation of CGRP-positive DRG neurons. Cancer pain in TRPV1 knockout mice was significantly lower than that in WT mice. In conclusion, TRPV1 is involved in both tumor growth and cancer pain, potentially leading to a novel strategy for the treatment of cancer pain and cancer development. Cancer pain is also suggested to facilitate tumor growth.

A Case of Decreased Amplitude in Motor Evoked Potentials Under Remimazolam Anesthesia.

Remimazolam is a newly developed benzodiazepine derivative. Although one case report on the use of remimazolam for motor evoked potential (MEP) monitoring has been reported, there has been no report of changes in the MEP response under remimazolam anesthesia, which is associated with impairment of the corticospinal motor track. This is a case of a 54-year-old woman who was diagnosed with an extradural extramedullary tumor. The patient reported being allergic to chicken eggs. We used remimazolam instead of propofol for anesthesia management. During tumor resection, the amplitudes of MEP responses at the left quadriceps femoris, left tibialis anterior, and left abductor hallucis muscle decreased. The surgery was scaled down and the tumor was removed in a reduced size. The patient had muscle weakness immediately after surgery but eventually recovered. In this case, we could detect changes in MEP response under remimazolam anesthesia, which suggested impairment of the motor tracts during surgery.

Comparison of catheter-over-needle and catheter-through-needle on leakage from the catheter insertion site during continuous femoral nerve block.

The aim of this study was to compare the incidences of leakage from the catheter insertion site during continuous femoral nerve block when using the catheter-through-needle, Contiplex Touhy™ (CT) and the newly developed catheter-over-needle, Contiplex C™ (CC). Forty adult patients who were scheduled to undergo continuous femoral nerve block for pain control following knee surgery were enrolled and were randomly assigned to a CT group or a CC group. After finishing surgery, a catheter for continuous femoral nerve block was placed using ultrasound. A catheter was advanced along the femoral nerve 5-6 cm beyond the needle tip. Then 0.25% levobupivacaine was continuously administered at a rate of 5 ml/h until 9:00 am on postoperative day 1. The incidence of leakage of the local anesthetic from the insertion site in the CT group was significantly higher than that in the CC group. In the CT group, leakage from the catheter insertion site was observed in 11 of 20 patients during the observation period. On the other hand, none of the patients in the CC group showed leakage. Contiplex C™ is more effective than Contiplex Touphy™ for prevention of leakage of local anesthetics from the insertion site during continuous femoral nerve block.