Norimasa Seo

Use of the Pentax-AWS in 293 patients with difficult airways.

Background:Several case reports have shown that the Pentax-AWS® (Hoya Corporation, Tokyo, Japan), a new video laryngoscope, is useful in patients with difficult airways. Methods:We assessed the effectiveness of the Pentax-AWS® in two groups. Group 1 included 270 patients in whom direct laryngoscopy using a Macintosh laryngoscope had been difficult. Group 2 included 23 patients with predicted difficult intubation and difficult mask ventilation without previous use of the Macintosh laryngoscope. Results:In group 1, the view of the glottis with the Macintosh laryngoscope was Cormack and Lehane grade 2 in 14 patients, grade 3 in 208 patients, and grade 4 in 48 patients. In 256 patients in whom the grade was 3 or 4 with the Macintosh laryngoscope, the view with the Pentax-AWS® was either grade 1 or 2 in 255 patients (99.6%; 95% confidence intervals 97.8–100%). Tracheal intubation was successful with the Pentax-AWS® in 268 of 270 patients (99.3%; 95% confidence interval 97.4–100%), and it failed (after two attempts) in two patients. In group 2, tracheal intubation was successful in 22 of 23 patients, and it failed in one patient. The reasons for failed intubation using the Pentax-AWS® were failure to position the blade toward the glottic side of the epiglottis, inability to maneuver the endotracheal tube away from the arytenoids and into the trachea, and bleeding and swelling of the oropharynx. Conclusion:The success rate of tracheal intubation using the Pentax-AWS® was high in patients with difficult laryngoscopy with a Macintosh laryngoscope and in patients with predicted difficult intubation.

Effect of N -methyl-d-aspartate Receptor ε1Subunit Gene Disruption of the Action of General Anesthetic Drugs in Mice

Background:Recent molecular strategies demonstrated that the N-methyl-d-aspartate (NMDA) receptor is a major target site of anesthetic agents. In a previous article, the authors showed that knocking out the NMDA receptor &egr;1 subunit gene markedly reduced the hypnotic effect of ketamine in mice. In the current study, the authors examined the in vivo contribution of the NMDA receptor &egr;1 subunit to the action of other anesthetic drugs. Methods:The authors determined the anesthetic effects of nitrous oxide on sevoflurane potency in NMDA receptor &egr;1 subunit knockout mice compared with those in wild-type mice. They then tested the hypnotic effect of &ggr;-aminobutyric acid–mediated agents, such as propofol, pentobarbital, diazepam, and midazolam, in knockout mice and wild-type mice. Results:The anesthetic action of sevoflurane itself was unaffected by the abrogation of the NMDA receptor &egr;1 subunit. Adding nitrous oxide reduced the required concentration of sevoflurane to induce anesthesia in wild-type mice, whereas this sparing effect was diminished in knockout mice. Furthermore, propofol, pentobarbital, diazepam, and midazolam also had markedly attenuated effects in knockout mice. Conclusions:Although it has been demonstrated that knocking out the expression of receptors may induce changes in the composition of the subunits, the network circuitry, or both, the current findings show consistently that the NMDA receptor &egr;1 subunit mediates nitrous oxide but not sevoflurane anesthesia. Furthermore, the attenuated anesthetic impact of propofol, pentobarbital, diazepam, and midazolam as well as ketamine in knockout mice suggests that the NMDA receptor &egr;1 subunit could be indirectly involved in the hypnotic action of these drugs in vivo.

Tracheal intubation by non-anesthesia residents using the Pentax-AWS airway scope and Macintosh laryngoscope

STUDY OBJECTIVE To evaluate the performance of the Pentax-AWS airway scope for tracheal intubation compared with the Macintosh laryngoscope by non-anesthesia residents. DESIGN Prospective, randomized, cohort study. SETTING University-affiliated hospital. PATIENTS 520 patients who underwent tracheal intubation for general anesthesia. INTERVENTIONS 48 non-anesthesia residents performed tracheal intubation using either the Pentax-AWS or the Macintosh laryngoscope. MEASUREMENTS Time to complete tracheal intubation, number of attempts until successful intubation, and number of intubations of the esophagus were recorded. RESULTS Time to secure the airway (sec; mean +/- SD) was shorter with the Pentax-AWS than with the Macintosh laryngoscope (44 +/- 19 vs. 71 +/- 44 sec; P < 0.001). Of the 264 tracheal intubations with the Pentax-AWS, 239 (91%) were completed within 60 seconds, while only 148 (58%) of the 256 tracheal intubations performed with the Macintosh laryngoscope were completed within the same period. The rate of successful intubations on the first attempt was higher with the Pentax-AWS than the Macintosh laryngoscope (P < 0.001). No esophageal intubation was experienced with the Pentax-AWS approach, while 18 occurred with the Macintosh laryngoscope (P < 0.001). CONCLUSION The Pentax-AWS appears to require less operator skill than the Macintosh laryngoscope. Use of the Pentax-AWS may reduce the time to secure the airway and the incidence of failed tracheal intubation by non-anesthesia residents.

Tracheal intubation by non-anaesthetist physicians using the Airway Scope.

Objective: To evaluate the performance of the Airway Scope for tracheal intubation by non-anaesthetist physicians. Methods: Under supervision by staff anaesthetists, non-anaesthesia residents performed tracheal intubation using either the Airway Scope (n = 100) or Macintosh laryngoscope (n = 100). The time required for airway instrumentation and the success rate at first attempt were investigated. Results: The time to secure the airway was shorter with the Airway Scope than with the Macintosh laryngoscope (p<0.001). The success rate at first attempt was higher with the Airway Scope than with the Macintosh laryngoscope (p<0.001). Conclusion: The Airway Scope may reduce the time to secure the airway and the incidence of failed tracheal intubation in novice laryngoscopists.

The dosing-time dependent effects of intravenous hypnotics in mice

Chronobiology, which focuses on the biological rhythms that occur in the organization of living organisms, has been studied for several decades. Chronopharmacology, however, has received little attention until recently. We examined the hypnotic duration of intraperitoneally administered ketamine, pentobarbital, propofol, midazolam, and ethanol, to test whether they have obvious dosing-time dependent effects. Male C57BL/6 mice, which showed clear circadian rhythms of water-intake under a strict 12-h lighting cycle, were used. All tested drugs had significantly longer episodes of loss of righting reflex when administered at 22:00 (early active phase) than at 10:00 (early inactive phase). This dosing-time dependent hypnotic duration did not depend on the contents and activities of cytochrome P450 enzymes in the liver. These findings might be of clinical benefit in deciding the administration time and doses of anesthetics.

Vasopressin may be useful in the treatment of systemic anaphylaxis in rabbits.

Recent studies demonstrate that vasopressin is useful when treating hemorrhagic and septic shock. The effect of vasopressin on systemic anaphylaxis has not been investigated except in clinical case reports. Vasopressin increases blood pressure because of vasoconstriction through the V1 receptor. Thus, we evaluated the effect of vasopressin on circulatory depression and bronchoconstriction provoked by systemic anaphylaxis and survival rates in rabbits. In the first set of experiments, 15 nonsensitized rabbits received normal saline (control) and vasopressin at 0.8 or 0.08 U/kg. In the second set, 40 sensitized rabbits received horse serum to induce anaphylaxis, and then received the same drugs as in the first set. In the first set, mean arterial pressure (MAP) in vasopressin groups increased by 18% to 24% compared with the control. Vasopressin at 0.8 U/kg decreased MAP insignificantly before the increases of MAP occurred. In the second set, vasopressin at 0.08 U/kg improved the survival rate. At 45 min after antigen challenge, 69% of the rabbits that received vasopressin at 0.08 U/kg were alive, whereas 29% of the control rabbits and 23% of the rabbits that received vasopressin at 0.8 U/kg were alive. Vasopressin increased MAP by 36% to 109% compared with the control within 5 min, however, at 2 min, vasopressin at 0.8 U/kg had no effect on MAP. Pulmonary dynamics were similar. In conclusion, vasopressin at 0.08 U/kg improved survival rates and severe hypotension provoked by systemic anaphylaxis, suggesting that this agent may be useful in the treatment of systemic anaphylaxis.

Changes in plasma total and ionized magnesium concentrations and factors affecting magnesium concentrations during cardiac surgery

The purpose of this study was to measure blood total and ionized magnesium concentrations ([TMg] and [Mg2+], respectively) and to investigate factors that might be affecting their changes during cardiac surgery using hypothermic cardiopulmonary bypass. Eight patients were examined. All the patients received diuretics and predeposited autologous blood during surgery. No drugs containing Mg2+ were administered. Nine blood samples and eight urine samples were collected from the pre-induction period to the end of surgery. Hematocrit, [TMg], [Mg2+], plasma concentrations of calcium ([Ca2+]), creatinine, parathyroid hormone (PTH), urinary concentrations of TMg, and creatinine were measured, and the fractional excretion of Mg (FEMg) was calculated. Both [TMg] and [Mg2+] decreased significantly in the prebypass period and remained significantly depressed thereafter. The ionized fraction of magnesium ([Mg2+]/[TMg]) was decreased during the postbypass period. Hematocrit decreased significantly from the prebypass period, and FEMg increased significantly after aortic cross-clamping. In conclusion, hemodilution and renal loss were main causes of hypomagnesemia, and citrate in predeposited autologous blood may contribute to the decrease in [Mg2+]/[TMg] in the postbypass period. These results suggest that magnesium supplementation under close monitoring of [Mg2+] should be required during cardiac surgery.

Mechanical effects of leg position on vertebral structures examined by magnetic resonance imaging

Background and Objectives Leg manipulation has been postulated to affect spinal curvature and position of the cauda equina within the dural sac. However, no evidence of such mechanical effects has been shown in living subjects. We used magnetic resonance imaging to evaluate the mechanical effects of leg position on these 2 parameters. Methods Sagittal and axial magnetic resonance images of the lumbosacral vertebral canal were obtained in 5 healthy, female volunteers with the subject in the supine position with knees straight, knees slightly flexed, and knees fully flexed. Results In the straight leg position, physiologic lumbar lordosis was evident in all subjects on midline sagittal slices, whereas lumbar lordosis disappeared in the fully flexed leg position. On the axial slices the cauda equina moved ventrally within the dural sac in all subjects in the fully flexed leg position. In 1 of the 5 subjects the cauda equina moved ventrally and also separated completely into right and left parts. Conclusions Our findings indicate that 2 potential factors, flattening of the lumbar lordosis and some added tension on the lumbosacral nerve roots, may contribute to postoperative back and leg aching after spinal anesthesia in the lithotomy position.

In vitro study of patient's and physician's radiation exposure in the performance of epiduroscopy.

Background and Objectives: Epiduroscopy is a minimally invasive diagnostic and therapeutic technique, useful in the management of patients with back and leg pain. However, the dose of radiation exposure by fluoroscopy during epiduroscopy is not known. The endpoint of our study was to evaluate the amount of radiation exposure for patients and health care workers during epiduroscopy. Methods: First, we measured the radiation dose during a 10‐minute fluoroscopy exposure in humanoid models, which substituted for the patient and the physician. Second, we measured the duration of fluoroscopy during our clinical epiduroscopy in 14 patients and observed for radiation injury in these patients. Results: In the humanoid models, the patient model skin exposure dose over a 10‐minute period was measured as 238 mGy. The physicians exposure dose for 10 minutes was measured as 0.67 mGy outside the lead apron and 0.0084 mGy inside the lead apron. For the clinical epiduroscopic procedures, the average duration of fluoroscopy was 9 minutes and 26 seconds. No skin injuries in the patients were observed at a 1‐month postprocedure assessment. Conclusions: The radiological dosages in the patient humanoid model were less than the threshold doses that could lead to organ injuries for 1 epiduroscopic procedure. However, care should be taken for cumulative exposures in repeated procedures.

Nasotracheal intubation using the Airtraq versus Macintosh laryngoscope: a manikin study.

The Airtraq laryngoscope is a new intubation device that provides a non-line-of-sight view of the glottis. We evaluated this device by comparing the ease of nasotracheal intubation on a manikin with the use of Airtraq versus the Macintosh laryngoscope with and without Magill forceps. Nasotracheal intubation on a manikin was performed by 20 anesthesiologists and 20 residents with the Airtraq or Macintosh laryngoscope. The mean (+/- SD) time required for nasotracheal intubation by the residents was significantly shorter with the Airtraq laryngoscope than with the Macintosh laryngoscope (16 +/- 7 sec vs 22 +/- 10 sec; P < .001), but no difference in intubation time was observed between Airtraq (15 +/- 11 sec) and Macintosh (13 +/- 6 sec) laryngoscopy by the anesthesiologists. The Magill forceps was used more frequently to facilitate intubation with the Macintosh laryngoscope than with the Airtraq laryngoscope in both groups of operators (P < .001). [corrected] The Airtraq laryngoscope scored better on the visual analog scale than did the Macintosh laryngoscope in both groups of operators (P < .05). The Airtraq laryngoscope offers potential advantages over standard direct laryngoscopy for nasotracheal intubation.