Toshiyuki Minonishi

Mechanism of the ropivacaine-induced increase in intracellular Ca2+ concentration in rat aortic smooth muscle

Background:  Ropivacaine is a long‐acting local anesthetic with low cardiac toxicity that induces vasoconstriction in vitro and in vivo. Vascular smooth muscle tone is regulated by changes in both intracellular Ca2+ concentration ([Ca2+]i) and myofilament Ca2+ sensitivity. Therefore, the aim of this study was to examine the mechanism underlying the increase in [Ca2+]i in ropivacaine‐induced vascular contraction.

Volatile anesthetics inhibit angiotensin II-induced vascular contraction by modulating myosin light chain phosphatase inhibiting protein, CPI-17 and regulatory subunit, MYPT1 phosphorylation.

BACKGROUND: Vascular contraction is regulated by myosin light chain (MLC) phosphorylation. Inhibition of MLC phosphatase (MLCP) increases MLC phosphorylation for a given Ca2+ concentration, and results in promoting myofilament Ca2+ sensitivity. MLCP activity is mainly determined by protein kinase C (PKC) and Rho kinase through the phosphorylation of both PKC-potentiated inhibitory protein (CPI-17) and myosin phosphatase target subunit (MYPT1). We have previously demonstrated that sevoflurane inhibits PKC phosphorylation and membrane translocation of Rho kinase. This study was designed to investigate the effects of sevoflurane and isoflurane on CPI-17, MYPT1, and MLC phosphorylation in response to angiotensin II (Ang II) in rat aortic smooth muscle. METHODS: The effects of sevoflurane or isoflurane (1–3 minimum alveolar concentration) on the vasoconstriction and phosphorylation of MLC, CPI-17, MYPT1 at Thr853 and MYPT1 at Thr696 in response to Ang II were investigated using isometric force transducer and Western blotting, respectively. RESULTS: Ang II (10−7 M) elicited a transient contraction of rat aortic smooth muscle that was inhibited by both sevoflurane and isoflurane in a concentration-dependent manner. Ang II also induced an increase in the phosphorylation of MLC, CPI-17, MYPT1/Thr853 and MYPT1/Thr696. Sevoflurane inhibited the phosphorylation of MLC, CPI-17, and MYPT1/Thr853 in response to Ang II in a concentration-dependent manner. Isoflurane also inhibited MLC phosphorylation in response to Ang II, which was associated with decreases in MYPT1/Thr853, but not in CPI-17. Neither sevoflurane nor isoflurane affected the Ang II-induced phosphorylation of MYPT1/Thr696. CONCLUSION: Although both volatile anesthetics inhibited Ang II-induced vasoconstriction and MLC phosphorylation to similar extent, the mechanisms behind the inhibitory effects of each anesthetic on MLCP activity appear to differ.

Tracheal intubation with the AirwayScope™ videolaryngoscope using straight vs curved reinforced tubes

To the Editor, The AirwayScope (AWS-S100; IMI Co., LTD., Koshigaya Saitama, Japan) is proposed as an alternative to the classical Macintosh laryngoscope for tracheal intubation in patients with cervical spine instability and/or neck stiffness, because it offers a better laryngeal view with less cervical spine movement. Its introducer, the INTLOCK, gives the straight reinforced tube a downward orientation, whereas the curved tube points upwards. Therefore, intubation difficulties may be more frequent with the straight tube because of more likely impingement with the arytenoids (Fig. 1). We compared straight and curved reinforced endotracheal tubes in terms of intubation success rate, delay of intubation, incidence of impingement with the arytenoids, and postoperative sore throat and hoarseness. After obtaining approval from the Research Ethics Committee of Wakayama Medical University and written informed patient consent, 55 patients (45–84 yr) American Society of Anesthesiologists’ physical status I–III undergoing lumbar spine surgery had their tracheal intubation performed with an AWS using a tube size 7.5 for females (F) and 8.0 for males (M). Patients were assigned to the curved group (curved reinforced tube; Covidien, Mansfield, MA, USA), n = 25, M/F = 14/11, or to the straight group (straight reinforced tube; Fuji Systems Co., Bunkyo-ku, Tokyo, Japan), n = 30, M/F = 14/16. If intubation did not succeed at the first attempt, another insertion was allowed by adjusting the AWS direction upward. Twenty-four hours after surgery, severity of sore throat and hoarseness were graded. Sample size calculation was performed using the time from laryngeal view to intubation as the primary end point. Twenty-five patients were needed for an 89% power to detect changes of 4.8 sec at a significance level of 0.05; standard deviation (SD) = 5.2. Statistical analysis was performed using the Mann–Whitney U test or the v test. Patients in both groups had similar characteristics, including sex ratio, age, body mass index, Mallampati score, and duration of anesthesia. The intubation success rate was greater in the curved group than in the straight group (100% vs 83.3%, respectively; P \ 0.05). When failure of tracheal intubation occurred in the straight group, it was due to the arytenoid cartilages interfering with the tube advancement and not due to an inadequate view of the larynx. The time from laryngeal view to intubation lasted longer in the straight group than in the curved group (11.1 ± 5.2 sec vs 6.3 ± 4.7 sec, respectively; mean ± SD; P \ 0.05), whereas the time until the glottic view did not differ between groups (10.2 ± 7.0 sec vs 9.8 ± 5.9 sec, respectively). These results suggest that intubation delay in the straight group was not due to the inadequate laryngeal view. The number of insertion attempts was greater in the straight group than in the curved group (2.4 ± 1.4 attempts vs 1.2 ± 0.5 attempts, respectively; P \ 0.05), reflecting the need for more upward adjustments of the introducer tip T. Minonishi, MD H. Kinoshita, MD, PhD (&) K. Tange, MD Y. Hatano, MD, PhD Wakayama Medical University, Wakayama, Japan e-mail: hkinoshi@nike.eonet.ne.jp; hkinoshi@wakayama-med.ac.jp

Nasogastric tube insertion assisted with the AirwayScopeTM in a patient with cervical spine instability

To the Editor, It has been shown that the AirwayScope (AWS; IMI Co., LTD., Koshigaya, Saitama, Japan), which is a newly developed videolaryngoscope consisting of a built-in monitor, camera, and disposable introducer, INTLOCK, has a distinct advantage compared with the Macintosh laryngoscope when it is used in patients with cervical spine instability and/or restricted neck movement. The AirwayScope can also facilitate nasogastric tube insertion in patients with cervical spine instability. An 82-year-old male patient, who had a predicted difficult airway due to a C5 fracture dislocation and the use of the halo vest, was scheduled for surgical stabilization of a cervical spine fracture. Following application of routine monitors and preoxygenation with the halo vest in situ, anesthesia was induced with propofol 1 mg kg iv and butorphanol 10 lg kg iv, followed by vecuronium 0.1 mg kg iv. After bag-mask ventilation with a facemask using 3% sevoflurane in 100% oxygen at a fresh gas flow of 6 L min for 3 min, the patient’s trachea was intubated with a reinforced 8.0 mm endotracheal tube (Covidien, Mansfield, MA, USA) without difficulty, using the AirwayScope. After correct endotracheal tube position was confirmed, the airway was secured, and the AirwayScope was again inserted into the patient’s mouth to obtain views of both the pharyngeal and laryngeal areas. Thereafter, a lubricated 16 Fr. nasogastric tube (Terumo Co., Shibuya-ku, Tokyo, Japan) was inserted via the left nostril until it reached the pharyngeal area (Fig. 1). The gastric tube was inserted easily under indirect vision without use of Magill forceps or additional maneuvers (Fig. 1). We used the AirwayScope to facilitate nasogastric tube insertion in this patient, since other known maneuvers related to insertion, including forward displacement of the larynx, may cause compression of an unstable cervical spine. Consistent with our report, a previous study documented that another video laryngoscope, GlideScope, successfully supported nasogastric tube insertion in surgical patients. We propose that using the videolaryngoscope to facilitate a nasogastric tube insertion may be more critical in patients with cervical instability, and that this maneuver may be effective to detect points where tube insertion could be interrupted (arytenoids, cartilages, and piriform sinuses).

Transient phlebitis induced by a bolus injection of propofol

redness of his veins disappeared (Fig. 1b). After that, the course of the patient during and after anesthesia was uneventful, even though we repeatedly administered the same concentration of vecuronium in a bolus manner (1–2 mg i.v.) during the surgery. The delayed redness at these veins did not recur. The incidence of such transient phlebitis after injection of propofol has not been well known. To understand the Transient phlebitis induced by a bolus injection of propofol

Severity of obstructive sleep apnea syndrome may affect postoperative hypoxemia in morbidly obese patients.

To the Editor: Although Ahmad et al. describe negligible involvement of obstructive sleep apnea syndrome (OSAS) in patients with postoperative hypoxemia, they did not identify the criteria used for a diagnosis of OSAS. In addition, the non-OSAS group contained 2 patients whose apnea-hypopnea indices were greater than 10 events per hour and OSAS is currently considered significant at an apnea-hypopnea index greater than five events per hour. 4 More importantly, on the basis of sleep studies, one-third or more of the non-OSAS patients would be considered to have sleep apnea, which also tends to invalidate the rationale for group comparisons and the conclusions of Ahmad et al. regarding the supposed lack of OSAS influence on incidence of postoperative hypoxemia. Therefore, further studies are required before any conclusion regarding the role of OSAS in postoperative hypoxemia in morbidly obese patients can be drawn.

Operating table failure and suggested safety precautions

To the editor: The Jackson Spine Table has been introduced to facilitate spine surgery involving fusion and instrumentation [1]. A recent paper has documented a patient falling from a Jackson Table (MIZUHO OSI, Union City, CA, USA) during anesthesia when the indicator lights on the bed were lit, confi rming rotational locked status [2]. However, it has not been confi rmed whether one can intentionally rotate this table in the condition in which the 180° rotation lock indicator is illuminated. As shown in Fig. 1a, the addition of some weight (80 kg) at the right side was capable of producing rotation of Operating table failure and suggested safety precautions