Masui. The Japanese journal of anesthesiology
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We studied the neurotoxic effect of lidocaine at different concentrations on the desheathed rabbit vagus nerve by measuring the amplitudes of evoked compound action potentials and the histological changes of the nerve by means of the electron microscopy after incubation in lidocaine-Ringer's bicarbonate (RB) solution. The following results were obtained. 1) Minimum concentrations of lidocaine for producing complete conduction block (minimum blocking concentration, MBC) were 0.02% for A beta and A delta fibers, and 0.03% for C fibers. 2) Irreversible conduction blocks of compound action potentials were observed in relation with lidocaine concentrations and the duration of incubation: e.g. 0.5% for 2 hours incubation was equivalent to the block with 1% for 1 hour. 3) Degenerative change of axons was revealed morphologically in the preparations exposed to 2% or a higher concentration of lidocaine. 4) Risk ratio, which means a numerical value calculated as clinical concentration/irreversible concentration with 2 hr exposure, was similar to other local anesthetics except dibucaine HCl, which shows an higher risk ratio. However, it should be noted that lidocaine has an risk of producing irreversible changes in nerve fibers, when applied to the nervous tissue at higher concentrations for longer durations.
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Comparative Study
[Comparison of pulse dye densitometry and thermodilution method in cardiac output measurement].
We measured cardiac outputs at forty points from five patients by pulse dye densitometry and compared these with those measured by thermodilution method. We obtained a good correlation (y = 1.090 x = . 0.030, n = 40, 5 cases) and small mean bias (0.348 +/- 0.830 l.min-1, n = 40, 5 cases) between the two methods. We suggest that this method of cardiac output measurement by pulse dye densitometry is not invasive and may be more effective than that by thermodilution method.
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A delta wave, which had not been detected in the preoperative electrocardiogram (ECG), was observed just before induction of anesthesia in a 53-year-old male scheduled for partial pancreatectomy. His ECG, diagnosed as intermittent Wolff-Parkinson-White (WPW) conduction, varied markedly displaying different wide QRS complexes with a short PR interval, and then returned abruptly to normal during anesthesia. WPW syndrome belongs to the category of pre-excitation syndromes, which is characterized by the accelerated abnormal conduction to the ventricle and paroxysmal tachyarrhythmias caused by an accessory pathway. We should consider the influence of anesthesia-related agents on atrioventricular conduction, and aim at preventing and managing tachyarrhythmias caused by this syndrome.
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To assess the clinical performance of a new neuromuscular blockade monitor "PARAGRAPH", we studied adults and pediatric patients during general anesthesia. PARAGRAPH enables anesthesiologists to perform various types of assessment of neuromuscular blockade, including TOF, DBS and single twitch even with children. The most remarkable point is its capability for analysis and printing by personal computer. We conclude this device is portable and easy to use, as well as a clinically reliable neuromuscular blockade monitor.
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Case Reports
[Recovery from out-of-hospital cardiac arrest after mild hypothermia: report of two cases].
We report two patients with out-of-hospital cardiac arrest who recovered after hypothermia therapy. A 25-year-old man and a 16-year-old boy were transferred to our hospital after cardiopulmonary arrest due to idiopathic ventricular fibrillation and hypertrophic cardiomyopathy, respectively. We carried out hypothermia therapy using cooling blankets, and the patients were maintained at 32-33 degrees C for 96 and 36 h, respectively. ⋯ Their arrest times (no spontaneous circulation and no CPR) were 10 min and 8 min, and CPR times (no spontaneous circulation while CPR was being performed) were 24 min and 20 min, respectively. In cases where the duration of ischemia is prolonged, the prognosis is expected to be poor. Therefore, we believe that hypothermia therapy is beneficial for such patients.