The Effect of ATP-sensitive Potassium Channel on R-PIA Induced Mechanical Antiallodynia in a Peripheral Neuropathic Rat / 대한통증학회지

BACKGROUND: Nerve ligation injury may produce mechanical allodynia, but this can be reversed after an intrathecal administration of adenosine analogues. In many animal and human studies, ATP-sensitive potassium channel blockers have been known to reverse the antinociceptive effect of various drugs. This study was performed to evaluate the mechanical antiallodynic effects of spinal R-PIA (Adenosine A1 receptor agonist) and the reversal of these effects due to pretreatment with glibenclamide (ATP-sensitive potassium channel blocker). Thus, the relationship between the antiallodynic effects of R-PIA and ATP-sensitive potassium channel were investigated in a neuropathic model. METHODS: Male Sprague Dawley rats were prepared by tightly ligating the left lumbar 5th and 6th spinal nerves and implantation of a chronic lumbar intrathecal catheter for drug administration. The mechanical allodynia was measured by applying von Frey filaments ipsilateral to the lesioned hind paw. And the thresholds for paw withdrawal assessed. In study 1, either R-PIA (0.5, 1 and 2microgram) or saline were administered intrathecally for the examination of the antiallodynic effect of R-PIA. In study 2, glibenclamide (2, 5, 10 and 20 nM) was administered intrathecally 5 min prior to an R-PIA injection for investigation of the reversal of the antiallodynic effects of R-PIA. RESULTS: The antiallodynic effect of R-PIA was produced in a dose dependent manner. In study 1, the paw withdrawal threshold was significantly increased with 2microgram R-PIA (P < 0.05). In study 2, the paw withdrawal threshold with 2microgram R-PIA was significantly decreased almost dose dependently by intrathecal pretreatment of 5, 10 and 20 nM glibenclamide (P < 0.05). CONCLUSIONS: These results demonstrated that an intrathecal injection of ATP-sensitive potassium channel blockers prior to an intrathecal injection of adenosine A1 receptors agonist had an antagonistic effect on R-PIA induced antiallodynia. The results suggest that the mechanism of mechanical antiallodynia, as induced by an intrathecal injection of R-PIA, may involve the ATP-sensitive potassium channel at both the spinal and supraspinal level in a rat nerve ligation injury model.

The Effect of Increased FIO2 before Removal of the Laryngeal Mask Airway on Postanesthetic Arterial Partial Oxygen Pressure / 대한마취과학회지

BACKGROUND: The administration of 100% oxygen at the end of general anesthesia before tracheal extubation has been shown to worsen postanesthetic pulmonary gas exchange. Because the laryngeal mask airway (LMA) and the endotracheal tube (ETT) are very different, it remains uncertain whether emergence on oxygen has the same results on lung function as ETT. Therefore, the aim of this study was to evaluate whether the use of 100% oxygen before LMA removal worsens gas exchange after inhalation or total intravenous general anesthesia. METHODS: Eighty ASA physical status I-II patients scheduled for elective surgery of the extremities were randomly assigned to receive either sevoflurane or propofol during general anesthesia with LMA. At the end of surgery, patients were randomized to an inspiratory fraction of oxygen of 0.3 in sevoflurane (n = 20), of 0.3 propofol (n = 20) or of 1.0 in sevoflurane (n = 20) or of 1.0 in propofol (n = 20) during emergence from anesthesia and LMA removal. Postoperative blood gas measurements were taken immediately and 60 min after arrival in the recovery room. RESULTS: No significant differences in PaO2 (propofol groups: 87.5 +/- 14.4 vs 88.5 +/- 10.5 mmHg, sevoflurane groups: 86.7 +/- 11.3 vs 90.7 +/- 9.9 mmHg) or alveolar - arterial oxygen tension difference (AaDO2) were found between the two groups at 30 min after LMA removal (propofol groups: 12.0 +/- 12.4 vs 10.3 +/- 8.3 mmHg, sevoflurane groups: 8.6 +/- 7.1 vs 7.1 +/- 9.4 mmHg). No differences were observed between the sevoflurane and propofol groups when FIO2 levels were similar. CONCLUSIONS: Breathing 100% oxygen during emergence from general anesthesia does not worsen postanesthetic pulmonary gas exchange when an LMA is used.

Complete Atrioventricular Nodal Block in Patient Undergoing Left Vagus Nerve Stimulation: A case report / 대한마취과학회지

There are virtually no cognitive and systemic side-effects associated with vagus nerve stimulation (VNS), which makes it a valuable treatment modality for patients with a poor tolerance to antiepileptic drugs. The safety of VNS therapy have been established in clinical studies, but there are few reports on the cardiac side effect associated with the intraoperative lead testing for implantation of the device for VNS. We report a patient with refractory epilepsy who experienced a complete atrioventricular block intraoperatively as a result of inadvertently high current intensity during the initial testing for implantation of a left vagus nerve stimulator.

Effects of Inhaled Nitric Oxide on Respiratory System Mechanics in Cats with Methacholine-induced Bronchoconstriction / 대한마취과학회지

BACKGROUND: Nitric oxide (NO) is a selective pulmonary vasodilator, and inhaled NO has bronchodilatory action due to their relaxation effect on conducting airway smooth muscle. The aim of this study was to evaluate the effects of inhaled NO on respiratory system mechanics in cats. METHODS: Nineteen cats were divided into 3 groups according to the doses of NO administered; group C (control, n=7), group 20 (20 ppm of NO, n=7), and group 40 (40 ppm of NO, n=5). After measuring the baseline value, methacholine chloride 25 microgram/kg/min was infused to induce bronchoconstriction. Inhalation of NO was started for each group 15 minutes after methacholine infusion. Pressure, volume, and flow rate were monitored with Bicore CP100 pulmonary monitor and the data were transferred to a personal computer and analyzed by a processing software. Respiratory system, airway and tissue viscoelastic resistances, and dynamic and static compliances were calculated. RESULTS: Methacholine infusion increased both airway and tissue resistances. Fifteen minutes after inhaling NO, airway resistances for NO 20 ppm and 40 ppm decreased to 65.8+/-8.5% and 62.2+/-8.9% of the control value (p<0.05). The values of tissue resistances for NO 20 ppm and 40 ppm decreased to 72.4+/-10.8% and 78.2+/-10.5% of the control value respectively (p<0.05). And thirty minutes after inhaling NO, there were also decreases of airway and tissue viscoelastic resistances in both groups but had no differences compared with fifteen minutes' values. There were no significant differences between the NO 20 ppm and 40 ppm in the values of airway and tissue viscoelastic resistances. CONCLUSION: Inhaled NO of 20 ppm and 40 ppm decreased both airway and tissue viscoelastic resistances and airway resistance was decreased more markedly than tissue resistance. There were no significant differences between 20 ppm and 40 ppm of NO in respiratory system mechanics in cats.

Respiratory Mechanics of Young and Elderly under Enflurane Anesthesia / 대한마취과학회지

BACKGREOUND: The aim of this study was to compare the respiratory mechanics between young and elderly during enflurane anesthesia using flow-interruption technique. METHODS: Fourteen patients were divided into 2 groups; for young aged group (Group Y)(24.9 4.9 years) and old aged group (Group O)(73.4 5.6 years). After anesthetic induction, endotracheal intubation was performed with Univent tube, and then tracheal pressure was measured at the distal end of the tube. 1.5 vol% of enflurane and 0.15 mg/kg of vecuronium were administered to maintain anesthesia. IMV (intermittent mandatory ventilation) was applied with Siemens Servo 900C ventilator and anesthetic gases were supplied via low pressure inlet of the ventilator. Tidal volume (10 ml/kg) was fixed during measurements for each patient. After stabilization of vital signs, respiratory parameters were measured before surgery. End-inspiratory occlusion was applied at least 3 seconds. Pressure, flow and volume were monitored and recorded with Bicore CP100 pulmonary monitor. The data were transfered to a PC and analyzed by a processing software. Total respiratory (Rrs), airway (Raw) and tissue (Rve) resistances, and dynamic (Cdyn) and static (Csta) compliances were calculated. Mann-Whitney U test was used for statistical analysis. RESULTS: There were no statistically significant differences for the Cdyn and Csta values between the two groups. But the values of Rrs, Raw and Rve were higher in the Group O than the Group Y. CONCLUSION: During enflurane anesthesia, the values of Rrs, Raw and Rve were higher in the Group O than the Group Y. To elucidate the exact causes of the above results, further studies are needed.