Anesthesia and analgesia
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Anesthesia and analgesia · Jul 2002
Case ReportsTemporary bilateral blindness after acute lidocaine toxicity.
This case report describes an uncommon complication (blindness) occurring after an inadvertent overdosage of a frequently used local anesthetic (lidocaine) during a regional anesthetic procedure. The discussion focuses on the suspected pathophysiology of the blindness.
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Anesthesia and analgesia · Jul 2002
Comparative StudyE-cylinder-powered mechanical ventilation may adversely impact anesthetic management and efficiency.
Anesthesiologists often administer care outside the operating room. These locations may depend on gas cylinders for their oxygen source more than the operating suites supplied by dedicated central pipelines. Using full E-cylinders, we determined the oxygen consumption of two often used, pneumatically driven anesthesia ventilators to answer three questions: How much time is available when mechanically ventilating patients in the setting of absent or malfunctioning central oxygen pipeline? How much oxygen is used by the ventilator to drive the bellows? How does changing the inspiratory to expiratory ratio and the inspiratory flow (Narkomed ventilator only) influence oxygen use? At a ventilation of 5 L/min, we found that mechanical ventilation consumes between 59% and 85% of the available oxygen in an E-cylinder to drive the ventilator at fresh gas flows ranging from 1 to 10 L/min. The time span until the low oxygen alarm sounded ranged from 38 to 99 min. Alteration of the inspiratory flow but not the inspiratory to expiratory ratio had a significant impact. Clinicians must recognize that mechanical ventilation using E-cylinders rapidly depletes this sole oxygen source and could jeopardize patient safety. Conversely, manual or spontaneous ventilation with low fresh gas flows minimizes oxygen depletion. ⋯ The time available to ventilate patients with an E-cylinder tank as the sole oxygen source was found to be as short as 38 min. Clinicians must recognize that mechanical ventilation using oxygen cylinders rapidly depletes oxygen and could jeopardize patient safety.
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Anesthesia and analgesia · Jul 2002
Comparative Study Clinical TrialSensitivity to vecuronium in seropositive and seronegative patients with myasthenia gravis.
Patients with myasthenia gravis (MG) are hypersensitive to nondepolarizing neuromuscular blocking drugs. Although antibodies to the acetylcholine receptor (AChR) often are observed in MG patients, 10% to 30% of patients do not show an anti-AChR antibody. Little is known about differences in sensitivity to nondepolarizing neuromuscular blocking drugs between MG patients with and without anti-AChR antibody. Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative MG patients and in non-MG patients (n = 8 each). During anesthesia with sevoflurane (2.5%) and nitrous oxide (60%) in oxygen, neuromuscular transmission was monitored by measuring the twitch tension of the adductor pollicis muscle with supramaximal stimulation. After baseline measurements, 10 microg/kg IV dose increments of vecuronium were administered sequentially until blockade exceeded 90%. The degree of blockade and onset time after the initial 10 microg/kg of vecuronium were assessed, and doses required to exceed 90% blockade were recorded. In addition, effective doses of 50% and 95% for vecuronium were calculated from a single data point. Both types of MG patients showed increased sensitivity to vecuronium compared with non-MG patients. ⋯ Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative myasthenia gravis (MG) patients and in non-MG patients. They were, indeed, both equally sensitive to vecuronium.
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Anesthesia and analgesia · Jul 2002
Case ReportsShy-Drager syndrome and severe unexplained intraoperative hypotension responsive to vasopressin.
We describe the first case of Shy-Drager syndrome diagnosed on the basis of intraoperative hemodynamic changes. The initial hypertension in the supine position followed by severe hypotension after hydralazine administration, ultimately responsive to vasopressin, led to a diagnosis of Shy-Drager syndrome. We suggest that vasopressin may be the drug of choice in patients with Shy-Drager syndrome with refractory hypotension.
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Anesthesia and analgesia · Jul 2002
The dose-related efficacy of diltiazem for enhancing diaphragmatic fatigability in dogs.
Nicardipine, a calcium channel blockade, enhances the production of diaphragmatic fatigue. We studied the dose-related effects of diltiazem, another calcium channel blockade, on diaphragmatic fatigability in dogs. Animals were divided into three groups of eight each. In each group, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. During this fatigue-producing period, Group I received no study drug, Group II was infused with diltiazem 0.1 mg. kg(-1). h(-1), and Group III was infused with diltiazem 0.5 mg. kg(-1). h(-1). We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). After the fatigue-producing period, in Group I, Pdi at low-frequency (20-Hz) stimulation decreased from baseline values (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. In Groups II and III, with an infusion of diltiazem, Pdi at both stimuli decreased from baseline values (P < 0.05). The decrease in Pdi to each stimulus was more in Group III than in Group II (P < 0.05). We conclude that diltiazem causes a dose-related augmentation of fatigability in the diaphragm of dogs. ⋯ Diaphragmatic muscle fatigue is implicated as a cause of respiratory failure. Diltiazem, a calcium channel blockade, enhances diaphragmatic fatigability in dogs in a dose-related manner.