Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialPeripheral antihyperalgesic effect of morphine to heat, but not mechanical, stimulation in healthy volunteers after ultraviolet-B irradiation.
The objective of this study was to evaluate direct peripheral analgesic effects of morphine using a peripheral model of hyperalgesia and the technique of IV regional anesthesia (IVRA), thus allowing the differentiation between central and peripheral mechanisms of action. Two spots on the ventral sides of both forearms in 12 volunteers were irradiated with ultraviolet (UV)-B to induce thermal and mechanical hyperalgesia. One day after the induction of the inflammatory reaction, 40 mL of morphine hydrochloride 0.01% was administered via IVRA. Calibrated heat and phasic mechanical stimuli were applied to differentially determine impairments of tactile and nociceptive perception. Touch and phasic mechanical stimuli of noxious intensity to normal skin did not reveal altered responsiveness caused by morphine. In contrast, the administration of morphine significantly increased heat pain thresholds in the UV-B-pretreated skin areas. The peripheral antihyperalgesic effects of morphine were demonstrated only in inflamed skin areas. Direct central analgesic effects were ruled out by the lack of measurable plasma concentrations of morphine and its metabolites. Morphine 0.01% significantly diminished thermal, but not mechanical, hyperalgesia by a peripheral mode of action, which suggests inhibition of effector pathways leading to heat, but not mechanical, sensitization. ⋯ The peripheral analgesic effects of morphine were studied using modified IV regional anesthesia. When administered 1 day after the induction of dermal inflammation, morphine 0.01% diminished heat, but not primary mechanical, hyperalgesia. Therefore, suppression of mechanical hyperalgesia seen in previous studies could be predominantly due to inhibition of secondary (central) mechanical hyperalgesia.
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialCost analysis of target-controlled infusion-based anesthesia compared with standard anesthesia regimens.
With the development of new computer-assisted target-controlled infusion (TCI) systems and the availability of short-acting anesthetics, total IV anesthesia (TIVA) has become increasingly popular. The aim of this study was to compare costs of TCI-based anesthesia with two standard anesthesia regimens. Sixty patients undergoing elective laparoscopic cholecystectomy were randomly divided into three groups. Group 1 (TIVA/TCI) received TIVA using a propofol-based TCI system and continuous administration of remifentanil; Group 2 (isoflurane) underwent inhaled anesthesia with isoflurane, fentanyl, and N2O; Group 3 (standard propofol) received fentanyl and N2O and a continuous infusion of propofol using a standard delivery system. Maintenance doses for anesthetics were adjusted according to the patient's need. Isoflurane consumption was measured by weighing the vaporizer by using a precision weighing machine. Duration of surgery and of anesthesia was similar in the three groups. Time from stopping administration of anesthetics until tracheal extubation (6+/-2 min) and stay in the postanesthesia care unit (PACU; 70+/-12 min) were shorter in Group 1 than in the Groups 2 (15+/-3 and 87+/-13 min, respectively) and 3 (10+/-4 and 81+/-14 min, respectively) (P < 0.05). Episodes of postoperative nausea and vomiting in the PACU and on the surgical ward were less common in Group 1 than in the other two groups. Intraoperative costs were higher in Group 1 ($62.19/patient; $0.55/min of anesthesia) than in Groups 2 ($16.97/patient; $0.13/min of anesthesia) and 3 ($34.68/patient; $0.32/min of anesthesia). Cost for discarded anesthetic drugs accounted for almost 18% of total intraoperative costs in Group 1. We conclude that TIVA/TCI anesthesia using propofol/remifentanil was associated with the highest intraoperative costs but the fewest postoperative side effects. An overall cost-effectiveness analysis of new anesthetic regimens must balance the direct cost of anesthetics and beneficial effects leading to improved patients' comfort. ⋯ In today's climate of cost-consciousness, careful economic evaluation of new anesthetic regimens is necessary. A target-controlled infusion (TCI)-based total IV anesthesia (TIVA) regimen using propofol and remifentanil was compared with a standard propofol anesthesia regimen and an inhaled anesthetic technique using isoflurane. Target-controlled infusion/total IV anesthesia was associated with the largest intraoperative costs but allowed the most rapid recovery from anesthesia, was associated with fewest postoperative side effects, and permitted earlier discharge from the postanesthesia care unit.
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Comparative Study Clinical TrialFiberoptic-guided airway exchange of the esophageal-tracheal Combitube in spontaneously breathing versus mechanically ventilated patients.
The aim of this study was to compare fiberoptic-guided airway exchange of the esophageal-tracheal Combitube (ETC, Kendall-Sheridan Catheter Corp., Argyle, NY) with an endotracheal tube in spontaneously breathing versus mechanically ventilated patients. Forty patients with Mallampati score III and IV scheduled for elective surgery were randomly allocated into two groups (n = 20 each): nonparalyzed, spontaneously breathing or paralyzed, mechanically ventilated patients. After anesthetic induction and insertion of the ETC, a fiberoptic bronchoscope threaded into an armored endotracheal tube was passed transnasally into the larynx. Endotracheal intubation was successful in 18 spontaneously breathing patients and in 15 patients during controlled ventilation. Successful airway exchange was completed in significantly less time (P < 0.05) in spontaneously breathing patients (9+/-3 min; mean +/- SD) than in mechanically ventilated patients (13+/-4 min). Both methods allowed for continuous airway control and maintenance of ventilation and oxygenation. The described method is a means of replacing the ETC with an endotracheal tube without interruption of airway control or ventilation. Replacing the ETC with an endotracheal tube using this method is more readily accomplished during spontaneous ventilation than during controlled ventilation. ⋯ We describe the replacement of the Combitube by an endotracheal tube by the aid of fiberoptic bronchoscopy and without interruption of airway control or ventilation. The performance of this technique was facilitated by spontaneous ventilation compared with mechanical ventilation.
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Anesthesia and analgesia · Jan 1999
Comparative Study Clinical TrialEvaluation of a new operating room ventilator with volume-controlled ventilation: the Ohmeda 7900.
Changes in fresh gas flow (FGF) during volume-controlled ventilation with the circle system have clinically important effects on the ventilatory variables of children. Current operating room ventilators allow a portion of the FGF to be added to the delivered tidal volume. The Ohmeda 7900 (Madison, WI) ventilator was designed to compensate for changes in FGF. We compared this ventilator with a standard ventilator, the Ohmeda 7000. Twenty patients (13-56 kg) undergoing dental or lower extremity surgery were studied. A side-by-side comparison of the two ventilators was performed using each patient as his or her own control. Beginning with the 7900 ventilator, FGF was set at 3.0 L/min, and the inspiratory to expiratory ratio was set at 1:2. Respiratory rate and tidal volume were adjusted to achieve an ETCO2 of 30-40 mm Hg. After a 10-min period of stabilization, inspired minute ventilation (VI), expired minute ventilation (VE), and ETCO2 were measured. FGF was then increased to 6.0 L/min, and the measurements were repeated after 10 min; FGF was then decreased to 1.5 L/min, and measurements were repeated after 10 min. The patient was then ventilated with an Ohmeda 7000 ventilator, and the sequence was repeated. The Ohmeda 7000 ventilator demonstrated significant changes in VI, VE, plateau pressure, and ETCO2, with changes in FGF (P = 0.0039-0.0001). The Ohmeda 7900 ventilator demonstrated compensation for changes in FGF; there were no significant changes in VI, VE, and ETCO2. We conclude that the Ohmeda 7900 ventilator provides stable ventilatory variables regardless of alterations in FGF (1.5-6.0 L/min). ⋯ In this study, we compared the effects of changing fresh gas flow on volume-controlled ventilation using two operating room ventilators (Ohmeda 7000 and Ohmeda 7900). The Ohmeda 7900, but not the Ohmeda 7000, provided stable ventilatory variables with fresh gas flows between 1.5 and 6.0 L/min.