Selective optogenetic activation of NaV1.7-expressing afferents in NaV1.7-ChR2 mice induces nocifensive behavior without affecting responses to mechanical and thermal stimuli.

In small and large spinal dorsal root ganglion neurons, subtypes of voltage-gated sodium channels, such as NaV1.7, NaV1.8, and NaV1.9 are expressed with characteristically localized and may play different roles in pain transmission and intractable pain development. Selective stimulation of each specific subtype in vivo may elucidate its role of each subtype in pain. So far, this has been difficult with current technology. However, Optogenetics, a recently developed technique, has enabled selective activation or inhibition of specific neural circulation in vivo. Moreover, optogenetics had even been used to selectively excite NaV1.8-expressing dorsal root ganglion neurons to induce nocifensive behavior. In recent years, genetic modification technologies such as CRISPR/Cas9 have advanced, and various knock-in mice can be easily generated using such technology. We aimed to investigate the effects of selective optogenetic activation of NaV1.7-expressing afferents on mouse behavior. We used CRISPR/Cas9-mediated homologous recombination to generate bicistronic NaV1.7-iCre knock-in mice, which express iCre recombinase under the endogenous NaV1.7 gene promoter without disrupting NaV1.7. The Cre-driver mice were crossed with channelrhodopsin-2 (ChR2) Cre-reporter Ai32 mice to obtain NaV1.7iCre/+;Ai32/+, NaV1.7iCre/iCre;Ai32/+, NaV1.7iCre/+;Ai32/Ai32, and NaV1.7iCre/iCre;Ai32/Ai32 mice. Compared with wild-type mice behavior, no differences were observed in the behaviors associated with mechanical and thermal stimuli exhibited by mice of the aforementioned genotypes, indicating that the endogenous NaV1.7 gene was not affected by the targeted insertion of iCre. Blue light irradiation to the hind paw induced paw withdrawal by mice of all genotypes in a light power-dependent manner. The threshold and incidence of paw withdrawal and aversive behavior in a blue-lit room were dependent on ChR2 expression level; the strongest response was observed in NaV1.7iCre/iCre;Ai32/Ai32 mice. Thus, we developed a non-invasive pain model in which peripheral nociceptors were optically activated in free-moving transgenic NaV1.7-ChR2 mice.

Extracellular signal-regulated kinase phosphorylation enhancement and NaV1.7 sodium channel upregulation in rat dorsal root ganglia neurons contribute to resiniferatoxin-induced neuropathic pain: The efficacy and mechanism of pulsed radiofrequency therapy.

Pulsed radiofrequency (PRF) therapy is one of the most common treatment options for neuropathic pain, albeit the underlying mechanism has not been hitherto elucidated. In this study, we investigated the efficacy and mechanism of PRF therapy on resiniferatoxin (RTX)-induced mechanical allodynia, which has been used as a model of postherpetic neuralgia (PHN). Adult male rats were intraperitoneally injected with a vehicle or RTX. Furthermore, PRF current was applied on a unilateral sciatic nerve in all RTX-treated rats. On both ipsilateral and contralateral sides, the paw mechanical withdrawal thresholds were examined and L4-6 dorsal root ganglia (DRG) were harvested. In the DRG of rats with RTX-induced mechanical allodynia, NaV1.7, a voltage-gated Na+ channel, was upregulated following the enhancement of extracellular signal-regulated kinase phosphorylation. Early PRF therapy, which was applied 1 week after RTX exposure, suppressed this NaV1.7 upregulation and showed an anti-allodynic effect; however, late PRF therapy, which was applied after 5 weeks of RTX exposure, failed to inhibit allodynia. Interestingly, late PRF therapy became effective after daily tramadol administration for 7 days, starting from 2 weeks after RTX exposure. Both early PRF therapy and late PRF therapy combined with early tramadol treatment suppressed NaV1.7 upregulation in the DRG of rats with RTX-induced mechanical allodynia. Therefore, NaV1.7 upregulation in DRG is related to the development of RTX-induced neuropathic pain; moreover, PRF therapy may be effective in the clinical management of patients with PHN via NaV1.7 upregulation inhibition.

Effect of cryoprecipitate on an increase in fibrinogen level in patients with excessive intraoperative blood loss: a single-center retrospective study.

BACKGROUND: Cryoprecipitate, which contains fibrinogen and factor VIII in large quantities, is concentrated from fresh frozen plasma, and it has hemostatic effects in severe bleeding. We retrospectively examined the effects of cryoprecipitate on the increase in fibrinogen levels in patients with excessive intraoperative blood loss. METHODS: Ninety-seven patients who were administered cryoprecipitate during surgery between June 2014 and May 2019 were enrolled in our study and categorized according to the volume of intraoperative blood loss as follows: group A, 2000-5000 mL; group B, 5000-10,000 mL; group C, > 10,000 mL. Data were extracted from electronic medical records and electronic anesthesia records. The primary endpoint was an increase in the fibrinogen level after the administration of cryoprecipitate. RESULTS: Nine patients with no fibrinogen data and four patients with a bleeding volume of less than 2000 mL were excluded; thus, 84 patients (A: n = 36, B: n = 37, C: n = 11) were evaluated. The mean intraoperative blood loss (mL) in groups A, B, and C were 3348 ± 791, 6688 ± 1225, and 14,281 ± 5142, respectively. The fibrinogen levels (mg/dL) before cryoprecipitate administration in groups A, B, and C were 189 ± 94, 113 ± 42, and 83 ± 29, respectively (p < 0.05 among the groups). The increase in fibrinogen level (mg/dL) after cryoprecipitate administration in group C was significantly greater than that in group A (84 ± 34 versus 50 ± 36, p < 0.01). CONCLUSIONS: The results of this study indicate that the effect of cryoprecipitate on the increase in fibrinogen level was most apparent in patients with excessive intraoperative blood loss ≥ 10,000 mL. In addition, most patients with intraoperative blood loss ≥ 5000 mL had fibrinogen levels < 150 mg/dL which improved to ≥ 150 mg/dL after cryoprecipitate administration in approximately 70% of patients. Therefore, cryoprecipitate administration should be considered for patients with hypofibrinogenemia (≤ 150 mg/dL) experiencing severe bleeding (e.g., ≥ 5000 mL) and rapid administration of cryoprecipitate is necessary to maximize the hemostatic effect, especially when the bleeding volume exceeds 10,000 ml.

Intraoperative Single-Dose Intravenous Acetaminophen for Postoperative Analgesia After Skin Laser Irradiation Surgery in Paediatric Patients: A Small Prospective Study.

OBJECTIVE: Acetaminophen is an analgesic that shows efficacy in postoperative pain relief in children. Many drugs such as opioids, non-steroidal anti-inflammatory drugs, and/or acetaminophen have been used in paediatric skin laser irradiation surgery for postoperative pain relief. However, acetaminophen has some advantages over opioids, and opioids are being used less often. We aimed to demonstrate the effectiveness of intravenous (IV) acetaminophen during surgery for postoperative pain in paediatric skin laser irradiation. METHODS: The present study is a small, prospective, double-blinded, randomized controlled trial. Paediatric patients (1-12 years old with an American Society of Anesthesiologists physical Status I and II), scheduled for skin laser irradiation for a nevus or haemangioma between October 2014 and April 2016 were randomized into the acetaminophen (n=9) and placebo (saline, n=8) groups. The observational face scale (FS) and the Behavioural Observational Pain Scale (BOPS) scores were recorded on emergence from anaesthesia, and 1, 2, and 4 hr post-surgery. RESULTS: Patient characteristics were not significantly different except with regard to the irradiation area and surgery time. The observational FS and BOPS scores of the acetaminophen group were lower than those of the placebo group; median (minimum-maximum) at each recording time: 1 (0-2) - 0 (0-2) - 0 (0-1) - 0 (0-2) vs. 2 (0-4) - 0 (0-2) - 0 (0-2) - 0 (0-1) and 1 (0-3) - 1 (0-3) - 1 (0-2) - 0 (0-1) vs. 2 (0-4) - 3 (0-5) - 1 (0-4) - 0 (0-3), p=0.07 and p=0.003, respectively. No differences in post-surgical analgesic use or adverse events were observed. CONCLUSION: In this study, we showed that the IV acetaminophen group had lower observational FS and BOPS scores in the early postoperative period; however, further studies including a large number of patients are required to confirm our findings.