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
Modeling the effect of progressive endotracheal tube occlusion on tidal volume in pressure-control mode.
A recognized hazard of prolonged endotracheal intubation is progressive airway occlusion resulting from deposition of secretions on the inner surface of the endotracheal tube (ETT). When volume-controlled ventilation is used, progressive ETT occlusion may be detected by monitoring the difference between peak and plateau airway pressures. In pressure-controlled modes, however, inspiratory airway pressures are preset and thus cannot act as a warning indicator. Instead, changes in delivered tidal volumes may aid the diagnosis of ETT occlusion. To determine whether tidal volume monitoring effectively detects progressive ETT occlusion, we mathematically modeled the response of a ventilator operating in pressure-controlled mode to increasing airway resistance. To corroborate our model, we then bench-tested the Siemens 300 and Puritan-Bennett 7200 ventilators by using a test lung and a series of ETTs ranging in size from 9.0 to 3.5 mm inner diameter to simulate progressive occlusion. We found that when pressure-controlled mode was used, progressive ETT occlusion did not reduce delivered tidal volumes until occlusion was nearly complete. We conclude that prolonged use of pressure-controlled mode may allow significant ETT obstruction to build up undetected, risking complete ETT occlusion and complicating the perioperative care of patients ventilated with this mode. ⋯ Although increasing airway pressures during volume-controlled ventilation allow early recognition of endotracheal tube (ETT) obstruction, airway pressures with pressure-controlled ventilation are fixed. We found during tests of two intensive care unit ventilators that although ETT obstruction reduces delivered tidal volumes during pressure-controlled ventilation, reductions do not occur until occlusion is advanced.
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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.
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In this research, we sought to test the hypothesis that the AccuTouch Flexible Bronchoscopy Simulator (Simulator) is an effective way to teach clinicians the psychomotor skills necessary to use the fiberoptic bronchoscope as an instrument for intubating the trachea of a pediatric patient. Pediatric residents with no prior experience in fiberoptic bronchoscopy were studied. Residents performed fiberoptic intubation on children undergoing general anesthesia. Tapes of these intubations were analyzed for: time to visualization of the carina, and number and time that the bronchoscope tip hit the mucosa. Residents were then trained on the Simulator. Performance of fiberoptic intubation on a subsequent child was compared. Training on the Simulator was the only instruction that the residents received between the two cases. A control group of residents performed two consecutive intubations without training on the Simulator between cases. Residents studied an average of 17 cases, and spent 39 min on the Simulator. Performance was markedly improved after the Simulator. Time to completion of successful intubation with a bronchoscope was reduced from 5.15 to 0.88 min (P < 0.001). The number of times that the tip of the bronchoscope hit the mucosa was reduced from 21.4 to 3.0 (P < 0.001). The amount of time that the resident spent viewing the mucosa decreased from 2.24 to 0.19 min (P < 0.001). The percent of time viewing the channel of the airway increased from 58.5% to 80.4% (P = 0.004). This bronchoscopy simulator was very effective in teaching residents the psychomotor skills necessary for fiberoptic intubation. Significant improvement was seen in time to completion of endotracheal intubation, as well as other performance indicators. ⋯ This research showed that the AccuTouch Bronchoscopy Simulator is an effective way to teach the psychomotor skills necessary to intubate the trachea of patients using a fiberoptic bronchoscope. The residents that practiced on the Simulator dramatically improved their skills compared with a control group of residents.