Anesthesia and analgesia
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Anesthesia and analgesia · Oct 2005
Can electroencephalographic analysis be used to determine sedation levels in critically ill patients?
Prolonged use of sedative drugs frequently leads to oversedation of intensive care patients. Clinical assessment scales are not reliable in deeply sedated patients. Parameters obtained from spectral and bispectral analysis of electroencephalogram (EEG) records have been combined to create an index (BIS) to monitor anesthesia depth. The role of such parameters in monitoring the depth of the sedation in intensive care unit (ICU) patients has yet to be determined. We designed the present prospective study to redefine and calculate available spectral and bispectral parameters from raw EEG records and estimate their clinical relevance for the diagnosis of under- or oversedation levels in ICU patients. Forty adult patients receiving continuous midazolam and morphine sedation were included. We obtained 167 clinical evaluations of sedation level using Ramsay and COMFORT scales along with an EEG record of 300 s. Six spectral parameters-relative power of 4 frequency bands (beta, alpha, Theta, and delta), 95th percentile of the power spectrum (SEF95), and 50th percentile of the power spectrum (SEF50) and four bispectral parameters, real triple product, bispectrum (Bispectrum), bicoherence, and ratio 10-were calculated. The relevance of each of these parameters and combinations in predicting too light (Ramsay 1 and 2) or deep (Ramsay 5 and 6) sedation levels was assessed. These calculations were performed before and after exclusion of the agitated patients, whose COMFORT 4 score was above 2. The most relevant parameters for predicting levels of deep sedation (Ramsay 5 and 6) were ratio 10 (area under the curve = 0.763; 95% confidence interval, 0.679-0.833) and SEF95 (area under the curve = 0.687; 95% confidence interval, 0.597-0.767). The most relevant parameters for predicting light levels of sedation (Ramsay 1 and 2) were also ratio 10 (area under the curve = 0.829; 95% confidence interval, 0.695-0.917) and SEF95 (area under the curve = 0.798; 95% confidence interval, 0.650-0.898). There is a modest improvement in relevance of their linear combination in predicting sedation level. Results were similar after exclusion of agitated patients. We conclude that various calculated EEG descriptive parameters exhibited large interindividual variability. There was a strong correlation between EEG spectral and bispectral parameters. Bispectral analysis slightly improves the predictive power of simple spectral analysis in distinguishing too light or deep sedation levels in ICU patients. ⋯ Spectral edge frequency 95 and Ratio 10 are the most relevant electroencephalogram (EEG) indexes for monitoring the level of sedation in intensive care unit patients but calculated EEG values exhibited large interindividual variability. Bispectral analysis of EEG provides a slight improvement over simple spectral analysis.
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Anesthesia and analgesia · Oct 2005
Randomized Controlled Trial Comparative Study Clinical TrialPain on injection of lipid-free propofol and propofol emulsion containing medium-chain triglyceride: a comparative study.
Pain on injection of propofol continues to be a problem for anesthesiologists. A lipid-free formulation of propofol and a propofol emulsion containing medium-chain triglyceride have become available in the Indian market. We performed this study to assess the pain on injection of propofol emulsion containing medium-chain triglyceride as the lipid carrier and lipid-free propofol formulation. One-hundred-thirty adult patients were randomly assigned to one of two groups: Group I received propofol emulsion containing medium-chain triglyceride and Group II received lipid-free propofol. One fourth of the total calculated induction dose was injected over 5 s in the largest vein on the dorsum of a hand. Pain was assessed using verbal response and behavioral signs. Both formulations caused pain on injection. However, the lipid-free propofol solution produced frequent (89%) and severe pain on injection compared with the emulsion containing medium-chain triglyceride (40%). ⋯ Pain on injection of two formulations of propofol was compared. A lipid-free formulation produced more pain on injection as compared with the emulsion containing medium-chain triglyceride.
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Anesthesia and analgesia · Oct 2005
Optimal end-tidal sevoflurane concentration for the removal of the laryngeal mask airway in anesthetized adults.
Sevoflurane provides smooth and rapid emergence from anesthesia and can be used when the removal of a laryngeal mask airway (LMA) is required in anesthetized patients. We sought to determine the optimal end-tidal concentrations of sevoflurane required for the removal of LMA in anesthetized adults. We studied 35 adults, aged 22-64 years old with an ASA physical status I or II, who were undergoing perineal surgery. General anesthesia was induced with thiopental, and the LMA was then inserted. Anesthesia was maintained with sevoflurane, oxygen, and air. After the surgery, the target concentration was maintained for at least 10 min, and then the LMA was removed. Each target concentration at the time of removal was predetermined by the Dixon up-down method (with 0.1% as a step size) starting at 1.7% end-tidal concentration of sevoflurane. The LMA removal was considered successful when there was no coughing, clenching of teeth, or gross purposeful movements during or within 1 min after removal and also if there was no breath holding, laryngospasm, or desaturation after removal. The end-tidal concentration of sevoflurane to achieve successful LMA removal in 50% of adults was 0.99% +/- 0.09% (mean +/- SD) and in 95% of adults was 1.18% (95% confidence limits, 1.07%-1.79%). In conclusion, we have determined that LMA removal in 50% and 95% of anesthetized adults can be safely accomplished without coughing, moving, or any other airway complications at 0.99% and 1.18% end-tidal concentrations of sevoflurane. ⋯ Because the removal of the laryngeal mask airway (LMA) in the anesthetized state is required in some clinical situations, we sought to determine the end-tidal concentration of sevoflurane to safely remove the LMA in anesthetized adults.