Monitoring of enzymes during chromatographic separations.

An on-line enzyme assay is presented based on flow injection techniques combined with fluorimetric detection. It allows to monitor NAD-dependent oxidoreductases during the purification of microbial crude extracts or partially purified enzymes by fast protein liquid chromatography (FPLC) in a near real-time mode. The arrangement is simple and can be easily integrated in the chromatographic system avoiding dead volumes. A high measuring frequency (up to 180 samples h-1) and a short response time (10-30 s) are achieved. The method has a low limit of detection (approximately 0.01 U ml-1), and a good reproducibility (1-4%), the injected sample volume is only 2 microliters.     

Changes in resting neural connectivity during propofol sedation

Background

The default mode network consists of a set of functionally connected brain regions (posterior cingulate, medial prefrontal cortex and bilateral parietal cortex) maximally active in functional imaging studies under “no task” conditions. It has been argued that the posterior cingulate is important in consciousness/awareness, but previous investigations of resting interactions between the posterior cingulate cortex and other brain regions during sedation and anesthesia have produced inconsistent results.

Methodology/Principal Findings

We examined the connectivity of the posterior cingulate at different levels of consciousness. “No task” fMRI (BOLD) data were collected from healthy volunteers while awake and at low and moderate levels of sedation, induced by the anesthetic agent propofol. Our data show that connectivity of the posterior cingulate changes during sedation to include areas that are not traditionally considered to be part of the default mode network, such as the motor/somatosensory cortices, the anterior thalamic nuclei, and the reticular activating system.

Conclusions/Significance

This neuroanatomical signature resembles that of non-REM sleep, and may be evidence for a system that reduces its discriminable states and switches into more stereotypic patterns of firing under sedation.     

Comparison of midazolam and diazepam for sedation during plastic surgery

A randomized double-blind study was designed to compare midazolam, a rapid-acting water-soluble benzodiazepine, with diazepam for sedation when administered as an adjuvant to ketamine during local anesthesia. In the preliminary dose-ranging study, midazolam (0.05 to 0.15 mg/kg IV) was found to produce a spectrum of central nervous system activity (e.g., sedation, amnesia) that was similar to diazepam (0.1 to 0.3 mg/kg IV). However, the slope of midazolam's dose-response curve for sedation appeared to be steeper (i.e., a narrower therapeutic dosage range). In a comparative evaluation of their relative sedative-amnestic properties and recovery characteristics, the median effective doses of the two benzodiazepines were compared. Midazolam (0.1 mg/kg IV) was found to produce more profound sedation and amnesia than diazepam (0.2 mg/kg IV). Midazolam was associated with significantly less pain on injection and a lower incidence of postoperative venoirritation. Overall patient acceptance was higher with midazolam compared to diazepam. Finally, recovery characteristics were similar for the two benzodiazepines in our outpatient setting.     

Low-dose propofol infusion for sedation during local anesthesia

The safety and efficacy of lose-dose propofol for sedation were investigated on 90 consenting patients who had undergone surgical procedures with local anesthesia. After being premedicated with intravenous midazolam 0.05 mg.kg(-1), all patients were randomly divided into two groups and received intravenously either a loading dose of propofol 0.8 mg.kg(-1) followed by a continuous infusion of propofol 30 microg.kg(-1)min(-1) (propofol group) or an equivalent volume of saline (placebo group) during operation. Study groups were compared with respect to the level of sedation, hemodynamic variables, oxygen saturation, and the incidence of intraoperative side effects. In addition, the discharge time and the satisfaction of both patients and surgeons with this sedative technique were assessed. Propofol reduced patients' discomfort and lowered their arterial pressure and heart rate during the infiltration of local anesthetics. It also promoted an adequate level of sedation without clinically significant oxygen desaturation in the intraoperative period. Surgeons and patients in the propofol group showed a higher level of satisfaction than those in the placebo group. There was no significant difference between the two groups with regard to the incidence of adverse effects and the discharge time. In conclusion, it was found that the use of low-dose propofol infusion was a safe and effective sedative technique for local anesthesia.     

Clinical evaluation of combination of dexmedetomidine and midazolam vs. dexmedetomidine alone for sedation during spinal anesthesia

BackgroundDexmedetomidine is a useful sedative agent for spinal anesthesia. However, it has been reported to decreases heart rate in a dose-dependent manner. In the present study, we compared the bolus dose of midazolam and bolus loaded dexmedetomidine over 10 min to determine additional sedation methods.MethodsA total of 100 patients who were classified as American Society of Anesthesiologists physical status I–II undergoing spinal anesthesia were randomly divided into two groups. In the combination of midazolam and dexmedetomidine group (group MD), 10 min after bolus loading of 0.05 mg/kg midazolam, 0.5 μg/kg/h dexmedetomidine was infused. In the dexmedetomidine group (group D), 1 μg/kg bolus dose of dexmedetomidine was infused over 10 min, and then 0.5 μg/kg/h dexmedetomidine was infused continuously.ResultsAt 10 min, the sedation depth of the two groups was approximately the same. In both groups, the bispectral index (BIS) was within the optimal range of 55–80 and the Ramsay Sedation Scale score was within the optimal range of 3–5. Both patient and surgeon satisfaction with sedation did not differ between groups. At 10 min, heart rate (beats/min) was significantly lower (P < .01) in group D and mean blood pressure (mm Hg) was significantly lower (P < .01) in group MD. The prevalence of bradycardia (P = .714), hypotension (P = .089), and hypoxia (P = .495) did not differ statistically between the two groups.ConclusionsMidazolam bolus and dexmedetomidine continuous infusion may be a useful additional sedation method for patients who have severe bradycardia.     

Gastrointestinal endoscopy: some perspectives.

Remarkable technological advances of fibreoptic endoscopy in the past two decades have produced important improvements in diagnosis and treatment of gastrointestinal and hepatobiliary disorders. These advances must be kept in perspective; continuing, critical assessment of their contribution to the management of patients is desirable. Endoscopy can have adverse effects on the total performance of departments of gastroenterology, on gastroenterology as a discipline, and even on the status of the medical profession in the community. Gastroenterologists need to show proficiency of performance and integrity of practice. Control may be achieved by certification delineation of privileges, peer review, public accountability, and realistic financial returns for procedures. Records of a department of gastroenterology indicate that some control may be achieved by insistence on a consultation before decision on endoscopy. This may be a desirable alternative to endoscopy on demand. Undue emphasis on technology runs some risk of destroying the proper practice of consultant medicine.