Hiroshi Iha

The effect of gamma-aminobutyric acid (GABA) receptor drugs on morphine-induced spastic paraparesis after a noninjurious interval of spinal cord ischemia in rats.

We have previously demonstrated that intrathecal morphine given after a noninjurious interval of spinal cord ischemia induced transient spastic paraparesis in a rodent model. However, the mechanism of this paraparesis is unknown. We hypothesized that morphine inhibits &ggr;-aminobutyric acid (GABA)ergic interneurons that control the tonus of spinal cord &agr;-motoneurons and that inhibition of spinal cord interneurons may cause spastic paraparesis. In this study, we investigate interactions between morphine and GABAergic agonists or antagonists on motor function after spinal cord ischemia and then clarified the mechanism of the spastic paraparesis induced by intrathecal morphine. Spinal cord ischemia was induced by aortic occlusion lasting 6 min. We first determined whether intrathecally administered GABA agonists (muscimol or baclofen) improve the spastic paraparesis in this model. GABA agonists did not improve the paraparesis. Next, we examined the effect of GABA antagonists (bicuculline or 5-aminovaleric acid) and determined the interaction between morphine and GABA antagonists. In an isobolographic analysis, the 50% effective dose decreased below the theoretical additive line, indicating a synergistic interaction between morphine and GABA antagonists. These results indicate that the spastic paraparesis induced by intrathecal morphine may be mediated in part by GABA receptors.

Appropriate method of administration of propofol, fentanyl, and ketamine for patient-controlled sedation and analgesia during extracorporeal shock-wave lithotripsy

AbstractPurpose. The aim of this study was to identify the appropriate method for administering propofol, fentanyl, and ketamine (PFK) for patient-controlled sedation and analgesia (PCSA) during extracorporeal shock-wave lithotripsy (ESWL). Methods. Twenty-one unpremedicated patients were randomly assigned to three groups that received different drug administration regimens. (group 1: low loading dose and high demand bolus, group 2: high loading dose and demand bolus, group 3: high loading dose and low demand bolus). Results. The patients in all groups were hemodynamically stable during ESWL. Oxygen desaturation was recognized in all groups, but was avoided by 2 l·min−1 of oxygen supply via a nasal prong. The total administration dose of the drugs was significantly higher (P < 0.05) in group 2 than in groups 1 and 3. The median level of sedation was the same, but the episodes of oversedation were not recognized in group 3 (P < 0.05). A significant difference in the frequency of episodes of oversedation was found between groups 2 and 3 (P < 0.05). The results were good or excellent for almost all patients, and were assessed as fair by only one patient in group 2. Conclusion. We concluded that the method used for group 3 is the most appropriate for administering PFK for PCSA during ESWL.

A comparison between low-flow leak test and oxygen flush leak test

AbstractPurpose. The clinical efficacy of two methods of preanesthetic leak test,namely the oxygen flush leak test (OFLT) and the low-flow leak test (LFLT), was compared regarding their ability to detect leakage in the anesthesia circuit and their accuracy. Methods. Examinees comprised 16 staff anesthesiologists and 7 physicians undergoing anesthesia training at our institution. They performed the two leak tests on anesthesia machines with some intentional leaks (0.1–1.0 l·min−1). The leakage detection rates (LDR) were analyzed by the χ2-test. The ability to detect leaks was measured by recording how many leaks were detected by 50% (LDR50) and 95% (LDR95) of the examinees. Results. The LDRs in the two tests were significantly different (χ2- analysis, P < 0.0001). Both LDR50 and LDR95 for the LFLT (0.23 and 0.41 l·min−1, respectively) were smaller than the values for the OFLT (0.37 and 0.82 l·min−1, respectively). The sensitivity and specificity of the LFLT (0.97 and 0.84, respectively) were higher than those of the OFLT (0.78 and 0.80, respectively). Conclusion. The LFLT was found to be superior to the OFLT regarding leak detection and reliability. We therefore recommend the LFLT for preanesthetic leak testing.

Gastric tube guide-equipped laryngeal mask airway.

tube (soft portion) and a small endotracheal tube (hard portion). The soft portion is attached to the dorsal surface of the mask portion of the LMA with a mild curved line, and the hard portion is attached to the side surface of the tube portion of the LMA. This attachment design assures the least contact resistance to the patient’s oral surface and the least disturbance when the G-LMA is handled.