Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Clinical TrialThe combination of epinephrine and isoproterenol as a simulated epidural test dose in isoflurane-anesthetized adults.
During isoflurane anesthesia, an epinephrine-containing test dose produces unreliable heart rate (HR) responses with a high incidence of hypertension, whereas an isoproterenol-containing test dose results in a high incidence of hypotension. We designed this study to determine whether different combination doses of epinephrine and isoproterenol produce reliable HR changes without overt fluctuations of systolic blood pressure (SBP). Seventy-five healthy patients were anesthetized with 1% end-tidal isoflurane after endotracheal intubation and randomized to one of five groups (n = 15 each) according to the combination dose given i.v.: epinephrine 15 microg, epinephrine 15 microg + isoproterenol 1.5 microg, epinephrine 7.5 microg + isoproterenol 3 microg, isoproterenol 3 microg, and saline. HR and SBP were measured at 20-s intervals for 4 min after injection. Based on the conventional HR criterion (positive if > or = 20 bpm increase), the epinephrine 15 microg + isoproterenol 1.5 microg, the epinephrine 7.5 microg + isoproterenol 3 microg, and the isoproterenol 3 microg groups yielded 100% sensitivities, specificities, and positive and negative predictive values, whereas all groups yielded 100% efficacy according to the modified HR criterion (positive if > or = 10 bpm increase). Four (27%) and three patients (20%) in the epinephrine 15 microg and the epinephrine 15 microg + isoproterenol 1.5 microg groups, respectively, developed systolic hypertension (SBP > or = 180 mm Hg), whereas four (27%) patients in the isoproterenol 3 microg group developed systolic hypotension (SBP < or = 80% of the preinjection value). We conclude that epinephrine 7.5 microg + isoproterenol 3 microg provides the most reliable HR changes with the least SBP fluctuations. ⋯ To test whether an epidural catheter may be in a blood vessel, various vasoactive drugs are administered during general anesthesia. The authors found that the combination of epinephrine 7.5 microg and isoproterenol 3 microg produced the most reliable heart rate changes with minimal blood pressure fluctuations.
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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
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.
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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
Unplanned tracheal extubation outside the operating room: a quality improvement audit of hemodynamic and tracheal airway complications associated with emergency tracheal reintubation.
The incidence of hemodynamic and airway complications associated with tracheal reintubation after an unplanned extubation has not been established. Patients whose tracheas were emergently intubated outside the operating room were reviewed over a 27-mo period via a quality improvement vehicle to evaluate hemodynamic and airway complications. Data from a subset of patients (n = 57) who underwent tracheal reintubation after unplanned (self-) extubation were collected for analysis. Of the reintubations, 93% took place within 2 h of self-extubation. Of the patients, 72% had hemodynamic alterations and/or airway-related complications, including hypotension (35%), tachycardia (30%), hypertension (14%), multiple laryngoscopic attempts (22%), difficult laryngoscopy (16%), difficult intubations (14%), hypoxemia (14%), and esophageal intubation (14%). In addition, one surgical airway and one case of "cannot ventilate, cannot intubate" leading to cardiac arrest and death were recorded. These findings suggest that patients requiring reintubation will likely do so soon after self-extubation and that reintubation can be fraught with significant hemodynamic and airway complications. Less than one third of patients undergo a mishap-free reintubation. Strategies to decrease the self-extubation rate in the intensive care unit are needed to improve patient safety and to lessen the potential impact of emergency airway management. ⋯ Self-extubation by patients requiring mechanical ventilation can be life-threatening, and replacing the breathing tube often leads to hemodynamic and airway complications. Using this quality improvement audit, 57 self-extubating patients and the complications associated with replacing the breathing tube, which are numerous and can lead to significant morbidity and mortality, were analyzed.