Tetsuya Uchino

Activation of Sensory Neurons Reduces Ischemia/Reperfusion-induced Acute Renal Injury in Rats

Background:Prostaglandin I2 (PGI2) produced by endothelial cells improves ischemia/reperfusion–induced acute renal injury by inhibiting leukocyte activation in rats. However, the underlying mechanism(s) of increased PGI2 production is not fully understood. Activation of sensory neurons increases endothelial PGI2 production by releasing calcitonin gene-related peptide (CGRP) in rats with hepatic ischemia or reperfusion. We examined here whether activation of sensory neurons increases PGI2 endothelial production, thereby reducing ischemia/reperfusion-induced acute renal injury. Methods:Anesthetized rats were subjected to 45 min of renal ischemia/reperfusion. Rats were pretreated with CGRP, capsazepine (a vanilloid receptor-1 antagonist), CGRP(8–37) (a CGRP receptor antagonist), or indomethacin (a cyclooxygenase inhibitor), or subjected to denervation of primary sensory nerves before ischemia/reperfusion. Results:Renal tissue levels of CGRP and 6-keto-prostaglandin F1&agr;, a stable metabolite of PGI2, increased after renal ischemia/reperfusion, peaking at 1 h after reperfusion. Overexpression of CGRP was also noted at 1 h after reperfusion. Increases in renal tissue levels of 6-keto-prostaglandin F1&agr; at 1 h after reperfusion were significantly inhibited by pretreatment with capsazepine, CGRP(8–37), and indomethacin. Pretreatment with capsazepine, CGRP(8–37), indomethacin, and denervation of primary sensory nerves significantly increased blood urea nitrogen and serum creatinine levels, renal vascular permeability, renal tissue levels of myeloperoxidase activity, cytokine-induced neutrophil chemoattractant, and tumor necrosis factor-&agr;, and decreased renal tissue blood flow. However, pretreatment with CGRP significantly improved these changes. Conclusions:Our results suggest activation of sensory neurons in the pathologic process of ischemia/reperfusion–induced acute renal injury. Such activation reduces acute renal injury by attenuating inflammatory responses through enhanced endothelial PGI2 production.

Use of Imaging Agent to Determine Postoperative Indwelling Epidural Catheter Position

Background Epidural anesthesia is widely used to provide pain relief, whether for surgical anesthesia, postoperative analgesia, treatment of chronic pain, or to facilitate painless childbirth. In many cases, however, the epidural catheter is inserted blindly and the indwelling catheter position is almost always uncertain. Methods In this study, the loss-of-resistance technique was used and an imaging agent was injected through the indwelling epidural anesthesia catheter to confirm the position of its tip and examine the migration rate. Study subjects were patients scheduled to undergo surgery using general anesthesia combined with epidural anesthesia. Placement of the epidural catheter was confirmed postoperatively by injection of an imaging agent and X-ray imaging. Results The indwelling epidural catheter was placed between upper thoracic vertebrae (n = 83; incorrect placement, n = 5), lower thoracic vertebrae (n = 123; incorrect placement, n = 5), and lower thoracic vertebra-lumbar vertebra (n = 46; incorrect placement, n = 7). In this study, a relatively high frequency of incorrectly placed epidural catheters using the loss-of-resistance technique was observed, and it was found that incorrect catheter placement resulted in inadequate analgesia during surgery. Conclusions Although the loss-of-resistance technique is easy and convenient as a method for epidural catheter placement, it frequently results in inadequate placement of epidural catheters. Care should be taken when performing this procedure.

Ultrasound visibility of regional anesthesia catheters: an in vitro study

Background Ultrasound subjective visibility of in-plane needles is correlated with the intensity difference between the needle surface and the background. Regional anesthesia catheters are difficult to visualize by an ultrasound. In the present study, we investigated the ultrasound visibility of the catheters. Methods Six catheters were placed at 0° and 30° relative to and at a depth of 1 cm below the pork phantom surface. Ultrasound images of in-plane catheters were evaluated, subjectively and objectively. Outer and inner objective visibilities were defined as the difference in the mean pixel intensity between the catheter surface and adjacent background, and between the surface and the center of the catheter, respectively. Evaluations were made based on the portion of the catheters. A P value < 0.05 was considered significant. Results Subjective visibility was more strongly correlated with the inner objective visibility than with the outer objective visibility at both angles. Metallic 19-gauge catheters were more subjectively visible than the non-metallic 20-gauge catheters at 30° degrees (P < 0.01). Subjective, and outer and inner objective visibility were significantly lower at 30° than at 0° (P < 0.01, P < 0.01, P = 0.02). Perifix ONE at 0° and Perifix FX at 30° were the most visible catheters (P < 0.01 for both). Conclusions Subjective visibility of catheters can not be evaluated in the same manner as that of the needles. For the best possible visualization, we recommend selecting a catheter with a structure that enhances the dark at the center of catheter, rather than basing the catheter selection on the bore size.

New Anthranilic Acid Derivative, EAntS-GS, Attenuates Freund’s Complete Adjuvant-Induced Acute Pain in Rats

BACKGROUND Acute and chronic pain commonly accompany various clinical conditions such as contusion, fracture, osteoarthritis, peripheral neuropathy, and postherpetic neuralgia. Recent studies have found that antioxidative drugs can have analgesic effects. The present study tested the hypothesis that a new anthranilic acid derivative, EAntS-GS, exerts antinociceptive effects on inflammatory pain in a rat model. METHODS We induced subacute pain with a plantar injection of Freunds complete adjuvant (FCA) in Sprague-Dawley rats. EAntS-GS (1 mg/kg subcutaneous injection or 1% application) was administered every 12 h beginning 24 h after FCA administration, and the plantar test was used to determine its effect on pain. Levels of myeloperoxidase, inducible nitric oxide synthase (iNOS), and protease activated receptor 2 (PAR2) were measured to elucidate the mechanism of action of EAntS-GS. RESULTS EAntS-GS significantly reduced FCA-induced pain and myeloperoxidase, iNOS, and PAR2 levels. Our findings suggest that the new anthranilic acid derivative, EAntS-GS, exerts antinociceptive effects, and that the mechanism involves iNOS and PAR2. CONCLUSION We conclude that EAntS-GS should be considered a new therapeutic tool to treat acute and chronic pain.

Effects of high peak airway pressure on the expression of heat shock protein 70 in rat lungs: a preliminary study

Background:  Heat shock protein 70 (HSP70) is induced by a wide variety of stresses in addition to hyperthermia. Recent studies have clarified that mechanical stretching and pressure overload can induce HSP70 in some tissues and cells. However, it remains unclear whether HSP70 is induced in stretch‐subjected lungs, such as those under mechanical ventilation. This study was designed to investigate the effects of high peak airway pressure (PAP) ventilation on HSP70 expression in intact rat lungs.

Ultrasound-guided central venous tip confirmation via right external jugular vein using a right supraclavicular fossa view:

Introduction: Ultrasound-guided central venous catheter tip confirmation has a potential to precisely locate the central venous catheter, preventing its misplacement, using real-time guidance. This observational study sought to determine the accuracy of central venous catheter tip positioning via the external jugular vein via a supraclavicular fossa view under ultrasound guidance. Methods: In total, 77 patients scheduled for central venous catheter insertion via the right external jugular vein were enrolled. The depth of central venous catheter insertion was determined by advancing the tip of the guidewire to the junction of the superior vena cava and right pulmonary artery, using a right supraclavicular fossa view ultrasound method. We determined the reference insertion depth to the carina using a postoperative chest x-ray photograph method. We then compared insertion depths obtained by the ultrasound and x-ray photograph methods and body-height formula. Results: In total, 62 patients were able to advance the guidewire and underwent ultrasound-guided central venous catheter insertion. In four patients, we corrected for misplaced guidewires. According to Bland–Altman plots, the insertion depth was 0.88 cm shorter for the ultrasound method (95% limits of agreement, −1.66 to 3.41 cm) and 0.90 cm shorter for the formulaic method (95% limits of agreement, −2.77 to 4.56 cm), compared with the x-ray photograph method. The x-ray photograph method had significantly positive correlations with the ultrasound (r = 0.73) and formulaic methods (r = 0.27). Conclusion: A right supraclavicular fossa view improves the accuracy of central venous catheter tip positioning and prevents central venous catheter misplacement via the right external jugular vein.

Use of epidurography and computed tomography to identify misplacement of a section of an epidural catheter in the subarachnoid space

One or more orifices of a multi-orifice epidural catheter can be inadvertently positioned outside the epidural space, resulting in a multicompartment block with varied clinical manifestations [1,2]. Therefore, accurate diagnosis of partial catheter migration based on clinical symptoms alone is difficult in cases where cerebrospinal fluid reflux is not detectable. A 78-year-old man (height, 1.56 m; weight, 55 kg) was scheduled for surgical repair of a ruptured bladder under general anesthesia with epidural anesthesia. A 3-mL local injection of lidocaine 1% containing 1:200,000 epinephrinewas administered between the T11 and T12 spinous processes with the patient in the left lateral decubitus position. A 17-gauge Tuohy needle (Perican II, B. Braun AG, Melsungen, Germany)