Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Comparative Study Clinical TrialBronchial mucus transport velocity in paralyzed anesthetized patients: a comparison of the laryngeal mask airway and cuffed tracheal tube.
We compared bronchial mucus transport velocity (BTV), an index of mucociliary clearance, between the laryngeal mask airway (LMA) and the tracheal tube (TT). Forty patients were studied during propofol anesthesia and muscle relaxation with rocuronium. BTV was measured 10 and 60 min after insertion of the airway device by fiberoptic observation of the movement of methylene blue dye injected onto the dorsal surface of the left main bronchus. BTV for the LMA was similar at 10 and 60 min (13.9 +/- 2.0 and 13.6 +/- 2.1 mm/min, respectively). BTV for the TT was significantly faster at 10 min that at 60 min (13.0 +/- 1.4 vs 6.9 +/- 1.2 mm/min, respectively; P < 0.00001). BTV was similar for both devices at 10 min (TT 13.0 +/- 1.4 mm/min versus LMA 13.9 +/- 2.0 mm/min), but was significantly faster for the LMA than for the TT at 60 min (LMA 13.6 +/- 2.1 mm/min versus TT 6.9 +/- 1.2 mm/min; P < 0.00001). We conclude that the LMA impedes mucociliary clearance less than the TT in anesthetized patients. This may have implications for reducing the risk of retention of secretions, atelectasis, and pulmonary infection. ⋯ This study compares bronchial mucus transport velocity, an index of mucociliary clearance, in anesthetized patients between two airway devices, the cuffed tracheal tube and the laryngeal mask airway. We have shown that the laryngeal mask airway impairs mucociliary clearance less than the tracheal tube. This may have implications for reducing the risk of retention of secretions, atelectasis, and pulmonary infection.
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Anesthesia and analgesia · Jun 1998
Comparative StudyTesting internal consistency and construct validity during evaluation of performance in a patient simulator.
The primary goal of this study was to test the items in a rating system developed to evaluate anesthesiologists' performance in a simulated patient environment. A secondary goal was to determine whether the test scores could discriminate between resident and staff anesthesiologists. Two 5-item clinical scenarios included patient evaluation and induction and maintenance of anesthesia. Rating scales were no response to the problem (score = 0), compensating intervention (score = 1), and corrective treatment (score = 2). Internal consistency was estimated using Cronbach's coefficient alpha. Scores between groups were compared using the Cochran-Mantel-Haenszel test. Subjects consisted of 8 anesthesiology residents and 17 university clinical faculty. The Cronbach's coefficient alpha was 0.27 for Scenario A and 0.28 for Scenario B. Two items in each scenario markedly decreased internal consistency. When these four items were eliminated, Cronbach's coefficient alpha for the remaining six items was 0.66. Faculty anesthesiologists scored higher than residents on all six items (P < 0.001). A patient simulator-based evaluation process with acceptable reliability was developed. ⋯ The reliability of anesthesia clinical performance in a patient simulation environment was assessed in this study. Of 10 items, 4 were poor in the evaluation process. When these items were removed, the reliability of the instrument improved to a level consistent with other studies. Because faculty scored higher than resident anesthesiologists, the instrument also showed discriminant validity.
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Anesthesia and analgesia · Jun 1998
Comparative StudyRapid development of tolerance to analgesia during remifentanil infusion in humans.
Studies in experimental animals have demonstrated a rapidly developing acute tolerance to the analgesic effect of opioids administered by continuous i.v. infusion. The aim of the present study was to determine whether acute tolerance plays an important role in the analgesic effect of remifentanil provided by i.v. infusion to humans. The analgesic effect of remifentanil, infused at a constant rate of 0.1 microg x kg(-1) x min(-1) for 4 h, was evaluated by measuring pain tolerance with thermal (2 degrees C water) and mechanical (pressure) noxious stimulations in 13 paid volunteers. The constant-rate infusion of remifentanil resulted in a threefold increase in pain tolerance with both tests. After reaching its maximum in 60-90 min, the analgesic effect of remifentanil began to decline despite the constant-rate infusion, and after 3 h of infusion, it was only one fourth of the peak value. A comparative rate in the development of acute tolerance measured in terms of time to 50% recovery during infusion was 129 +/- 27 min (mean +/- SD) with the cold water test and 138 +/- 39 min with the pressure test. We conclude that the development of tolerance should be included in the calculations for target-controlled infusions. ⋯ Our study shows that tolerance to analgesia during remifentanil infusion is profound and develops very rapidly. The administration of opioids during anesthesia based on target-controlled infusions should include corrections for the development of tolerance.
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Anesthesia and analgesia · Jun 1998
Comparative StudyThe pharmacokinetics of vecuronium in male and female patients.
To evaluate the effect of gender on the pharmacokinetics of vecuronium, we studied 30 patients (15 male and 15 female) undergoing elective plastic surgery with anticipated surgical blood loss of <300 mL under general anesthesia. General anesthesia was induced with thiopental 4-6 mg/kg and fentanyl 2-4 microg/kg and was maintained with 60% nitrous oxide in oxygen and an end-tidal concentration of 1.5%-2% enflurane. After a 2-min infusion of vecuronium 100 microg/kg, a modified fluorometric assay was used to determine the plasma concentrations of vecuronium for 5 h. The results showed that, compared with women, the plasma concentrations of vecuronium in men were significantly lower during the first 20 min and that the disposition kinetics of vecuronium can be best described mathematically by a three-compartment open model in the two groups. The volume of the central compartment and the volume of distribution at steady state were 39.6 +/- 8.6 and 164.8 +/- 29.3 mL/kg, respectively, in women. These values increased significantly to 54.4 +/- 14.4 and 201.4 +/- 75.8 mL/kg in men (P < 0.05). When the data were calculated on the basis of ideal body weight, the volume of distribution of vecuronium was also different between men and women (P < 0.05. The half-lives of fast distribution and distribution, the elimination half-life, mean residual time, area under the plasma-concentration curve, and plasma clearance were not different between the two groups. We conclude that the pharmacokinetics of vecuronium are significantly different between genders and that and men have the greater volume of distribution of vecuronium. ⋯ The authors found that, compared with women, men had lower plasma concentrations of vecuronium after the i.v. administration of vecuronium and a larger volume of distribution of vecuronium. The pharmacokinetic differences may be related to the differences in the sensitivity to vecuronium between genders.
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Anesthesia and analgesia · Jun 1998
A new and simple maneuver to position the left-sided double-lumen tube without the aid of fiberoptic bronchoscopy.
The double-lumen tube (DLT) is the mainstay of one-lung ventilation (OLV). We sought to determine whether this new intubation maneuver using an endobronchial cuff pressure could be substituted for verification by fiberoptic bronchoscope (FOB) in most conditions requiring left-sided DLT. Seventy-nine patients requiring video-assisted thoracoscopic surgery for pneumothorax or mediastinal mass, or open thoracotomy for lung or esophageal cancer were enrolled in this study. We used 35F (n = 23), 37F (n = 51), or 39F (n = 5) disposable polyvinyl chloride DLTs (Broncho-Cath; Mallinckrodt Medical Ltd., Athlone, Ireland), depending on the height and gender of the patients. The DLTs were inserted deeply until resistance was felt. At that time, the pilot of the endobronchial cuff was connected to the Control-Inflator (VBM Medizintechnik GmbH, Sulz am Neckar, Germany) via a three-way stopcock. The bronchial balloon was inflated with 1.0-2.0 mL of air through the stop-cock until approximately 30 cm H2O of cuff pressure was obtained. The DLT was slowly withdrawn until the pressure of the Control-Inflator decreased to approximately half the peak pressure during the initial phase of removal. At that time, the bronchial balloon was deflated, and the DLT was advanced approximately 1.0 cm (1.5 cm for the 39F DLT); using FOB, its position was checked by an independent observer not involved in positioning the DLTs. The ideal position was defined as that in which the carina was located at the same level with the middle 5 mm between the proximal margin of the endobronchial balloon and the circumferential black mark. In 50 patients the position was ideal, and in 27 patients it was not ideal but was within the margin of the safety. There were only two failures. We conclude that if a FOB is unavailable or inapplicable, this simple and new maneuver may be used as a substitute during the positioning of DLTs. ⋯ The correct position of the double-lumen tube is vital for one-lung ventilation, which has been confirmed with a fiberoptic bronchoscope. We devised a simple maneuver to position the double-lumen tube correctly without a fiberoptic bronchoscope.