Anesthesia and analgesia
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Anesthesia and analgesia · Mar 2003
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of airway responses during desflurane and sevoflurane administration via a laryngeal mask airway for maintenance of anesthesia.
Although sevoflurane is less pungent than desflurane at larger concentrations, neither anesthetic seems to irritate the airway when administered at the smaller concentrations often used during maintenance of anesthesia. Both anesthetics may be delivered effectively via a laryngeal mask airway, with minimal evidence of airway irritation.
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Anesthesia and analgesia · Mar 2003
Randomized Controlled Trial Comparative Study Clinical TrialSequential use of midazolam and propofol for long-term sedation in postoperative mechanically ventilated patients.
Acute withdrawal syndromes, including agitation and a long weaning time, are common adverse effects after long-term sedation with midazolam. We performed this study to determine whether the sequential use of midazolam and propofol could reduce adverse effects as compared with midazolam alone. We studied 26 patients receiving mechanical ventilation for three or more days after surgery. Patients were randomly assigned to two groups. In Group M, patients were sedated with midazolam alone. In Group M-P, midazolam was switched to propofol approximately 24 h before the expected stopping of sedation. The level of sedation was maintained at 4 or 5 on the Ramsay sedation scale. The sedation agitation scale was evaluated for 24 h after extubation. The recovery time from stopping of sedation to extubation was significantly shorter in Group M-P (1.3 +/- 0.4 h) compared with Group M (4.0 +/- 2.4 h). The incidence of agitation in Group M-P (8%) was significantly less frequent than that in Group M (54%). The results indicate that sequential use of midazolam and propofol for long-term sedation could reduce the incidence of agitation compared with midazolam alone. ⋯ Our study indicates that sequential use of midazolam and propofol could reduce the incidence of agitation compared with midazolam alone.
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Anesthesia and analgesia · Mar 2003
Clinical TrialChanges in consciousness, conceptual memory, and quantitative electroencephalographical measures during recovery from sevoflurane- and remifentanil-based anesthesia.
It is unclear whether opioid-induced changes in electroencephalogram (EEG) or auditory evoked potentials (AEPs) reliably correspond with consciousness. We examined the correlation between 1) the clinically assessed state of consciousness, 2) implicit and explicit memory (by use of word pairs), and 3) various measures of EEG and AEP-bispectral index (BIS), A-Line ARX AEP index, spectral entropy, and entropy of the singular value decomposition (SVDEN; a measure of the complexity of the EEG). We studied 21 women during a two-stage awakening (sevoflurane washout followed by remifentanil washout) after anesthesia for gynecological surgery. All were amnesic, and 19 were unresponsive to verbal command with remifentanil alone. In six patients, BIS decreased paradoxically as the remifentanil concentration decreased; this was caused by a low-amplitude EEG, which was misinterpreted by the Aspect algorithm as burst suppression. Most of the EEG/AEP variables were sensitive to the decrease in sevoflurane and the recovery of consciousness, but not to the effects of decreasing remifentanil concentrations. SVDEN was the only variable that demonstrated significant increases for both the sevoflurane and remifentanil washout phases. With the prediction probability statistic during remifentanil washout, SVDEN = 0.79, spectral entropy = 0.81, A-Line ARX AEP index = 0.63, and BIS = 0.58. Entropy measures appear to be worthy of further clinical evaluation in a larger series of patients. SVDEN may be a useful variable for assessing anesthetic and analgesic effects on the central nervous system. ⋯ During the recovery phase from a remifentanil-based anesthetic, the bispectral index is not reliably predictive of the depth of consciousness, because of suppression ratio artifacts. Entropy measures of the electroencephalogram show promise, but there is still no gold standard to estimate anesthetic depth.
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Anesthesia and analgesia · Mar 2003
Clinical TrialAn evaluation of the supraclavicular plumb-bob technique for brachial plexus block by magnetic resonance imaging.
Partly based on magnetic resonance imaging studies, the "plumb-bob" approach for brachial plexus block was designed to minimize the risk of pneumothorax. Nevertheless, the risk of pneumothorax has remained a concern. We analyzed magnetic resonance images from 10 volunteers to determine whether the risk of pneumothorax was decreased with this method. The recommended initial needle direction is anteroposterior through the junction between the lateral-most part of the sternocleidomastoid muscle and the superior edge of the clavicle. If the initial placement is not successful, the brachial plexus may be sought in sectors 20 degrees -30 degrees cephalad or caudad to the anteroposterior line in a sagittal plane through the insertion point. We found that the anteroposterior line reached the pleura in 6 of 10 volunteers without prior contact with the subclavian artery or the brachial plexus, but always with contact with the subclavian vein. To reach the middle of the brachial plexus, a mean cephalad redirection of the simulated needle by 21 degrees was required (range from 41 degrees cephalad to 15 degrees caudad in one case). We conclude that the risk of contacting the pleura and the subclavian vessels may be reduced by initially directing the needle 45 degrees cephalad instead of anteroposterior. If the brachial plexus is not contacted, the angle should be gradually reduced. ⋯ In magnetic resonance images of volunteers, simulated needle passes with the "plumb-bob" approach to the supraclavicular brachial plexus block were analyzed for precision and risk profile. To avoid needle contact with the lung, the subclavian vein, and the subclavian artery, our results suggest a change in the method's initial needle direction.
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Anesthesia and analgesia · Mar 2003
Randomized Controlled Trial Comparative Study Clinical TrialComparison of alpha-stat and pH-stat cardiopulmonary bypass in relation to jugular venous oxygen saturation and cerebral glucose-oxygen utilization.
Jugular venous oxygen saturation (SJVO(2)) reflects the balance between cerebral blood flow and metabolism. This study was designed to compare the effects of two different acid-base strategies on jugular venous desaturation (SJVO(2) <50%) and cerebral arteriovenous oxygen-glucose use. We performed a prospective, randomized study in 52 patients undergoing cardiopulmonary bypass (CPB) at 27 degrees C with either alpha-stat (n = 26) or pH-stat (n = 26) management. A retrograde internal jugular vein catheter was inserted, and blood samples were obtained at intervals during CPB. There were no differences in preoperative variables between the groups. SJVO(2) was significantly higher in the pH-stat group (at 30 min CPB: 86.2% +/- 6.1% versus 70.6% +/- 9.3%; P < 0.001). The differences in arteriovenous oxygen and glucose were smaller in the pH-stat group (at 30 min CPB: 1.9 +/- 0.82 mL/dL versus 3.98 +/- 1.12 mL/dL; P < 0.001; and 3.67 +/- 2.8 mL/dL versus 10.1 +/- 5.2 mL/dL; P < 0.001, respectively). All episodes of desaturation occurred during rewarming, and the difference in the incidence of desaturation between the two groups was not significant. All patients left the hospital in good condition. Compared with alpha-stat, the pH-stat strategy promotes an increase in SJVO(2) and a decrease in arteriovenous oxygen and arteriovenous glucose differences. These findings indicate an increased cerebral supply with pH-stat; however, this strategy does not eliminate jugular venous desaturation during CPB. ⋯ A prospective, randomized study in 52 patients during cardiopulmonary bypass revealed that pH-stat increased jugular venous oxygen saturation and decreased arteriovenous oxygen-glucose differences. There was no difference in the incidence of jugular venous desaturation. These findings suggest an increased cerebral blood flow with no protection against jugular venous desaturation during pH-stat.