Increased reading speed for stories presented during general anesthesia.
BACKGROUND: In the absence of explicit memories such as the recall and recognition of intraoperative events, memory of auditory information played during general anesthesia has been demonstrated with several tests of implicit memory. In contrast to explicit memory, which requires conscious recollection, implicit memory does not require recollection of previous experiences and is evidenced by a priming effect on task performance. The authors evaluated the effect of a standardized anesthetic technique on implicit memory, first using a word stem completion task, and then a reading speed task in a subsequent study. METHODS: While undergoing lumbar disc surgery, 60 patients were exposed to auditory materials via headphones in two successive experiments. A balanced intravenous technique with propofol and alfentanil infusions and a nitrous oxide-oxygen mixture was used to maintain adequate anesthesia. In the first experiment, 30 patients were exposed randomly to one of the two lists of 34 repeated German nouns; in the second experiment, 30 patients were exposed to one of two tapes containing two short stories. Thirty control patients for each experiment heard the tapes without receiving anesthesia. All patients were tested for implicit memory 6-8 h later: A word stem completion task for the words and a reading speed task for the stories were used as measures of implicit memory. RESULTS: The control group completed the word stems significantly more often with the words that they had heard previously, but no such effect was found in the anesthetized group. However, both the control and patient groups showed a decreased reading time of about 40 ms per word for the previously presented stories compared with the new stories. The patients had no explicit memory of intraoperative events. CONCLUSIONS: Implicit memory was demonstrated after anesthesia by the reading speed task but not by the word stem completion task. Some methodologic aspects, such as using low frequency words or varying study and test modalities, may account for the negative results of the word stem completion task. Another explanation is that anesthesia with propofol, alfentanil, and nitrous oxide suppressed the word priming but not the reading speed measure of implicit memory. The reading speed paradigm seems to provide a stable and reliable measurement of implicit memory. (+info)
Dependence of explicit and implicit memory on hypnotic state in trauma patients.
BACKGROUND: It is still unclear whether memory of intraoperative events results entirely from moments of inadequate anesthesia. The current study was designed to determine whether the probability of memory declines with increasing depth of the hypnotic state. METHOD: A list of words was played via headphones during surgery to patients who had suffered acute trauma. Several commonly used indicators of anesthetic effect, including the bispectral index, were recorded during word presentation. First, these indicators served as predictors of the memory performance in a postoperative word stem completion test. Second, general memory performance observed in the first part was separated into explicit and implicit memory using the process dissociation procedure, and then two models of memory were compared: One model assumed that the probability of explicit and implicit memory decreases with increasing depth of hypnotic state (individual differences model), whereas the other assumed equal memory performance for all patients regardless of their level of hypnotic state. RESULTS: General memory performance declined with decreasing bispectral index values. None of the other indicators of hypnotic state were related to general memory performance. Memory was still significant at bispectral index levels between 60 and 40. A comparison of the two models of memory resulted in a better fit of the individual differences model, thus providing evidence of a dependence of explicit and implicit memory on the hypnotic state. Quantification of explicit and implicit memory revealed a significant implicit but no reliable explicit memory performance. CONCLUSIONS: This study clearly indicates that memory is related to the depth of hypnosis. The observed memory performance should be interpreted in terms of implicit memory. Auditory information processing occurred at bispectral index levels between 60 and 40. (+info)
Functional brain imaging during anesthesia in humans: effects of halothane on global and regional cerebral glucose metabolism.
BACKGROUND: Propofol and isoflurane anesthesia were studied previously with functional brain imaging in humans to begin identifying key brain areas involved with mediating anesthetic-induced unconsciousness. The authors describe an additional positron emission tomography study of halothane's in vivo cerebral metabolic effects. METHODS: Five male volunteers each underwent two positron emission tomography scans. One scan assessed awake-baseline metabolism, and the other scan assessed metabolism during halothane anesthesia titrated to the point of unresponsiveness (mean +/- SD, expired = 0.7+/-0.2%). Scans were obtained using a GE2048 scanner and the F-18 fluorodeoxyglucose technique. Regions of interest were analyzed for changes in both absolute and relative glucose metabolism. In addition, relative changes in metabolism were evaluated using statistical parametric mapping. RESULTS: Awake whole-brain metabolism averaged 6.3+/-1.2 mg x 100 g(-1) x min(-1) (mean +/- SD). Halothane reduced metabolism 40+/-9% to 3.7+/-0.6 mg x 100 g(-1) x min(-1) (P< or =0.005). Regional metabolism did not increase in any brain areas for any volunteer. The statistical parametric mapping analysis revealed significantly less relative metabolism in the basal forebrain, thalamus, limbic system, cerebellum, and occiput during halothane anesthesia. CONCLUSIONS: Halothane caused a global whole-brain metabolic reduction with significant shifts in regional metabolism. Comparisons with previous studies reveal similar absolute and relative metabolic effects for halothane and isoflurane. Propofol, however, was associated with larger absolute metabolic reductions, suppression of relative cortical metabolism more than either inhalational agent, and significantly less suppression of relative basal ganglia and midbrain metabolism. (+info)
Postoperative behavioral outcomes in children: effects of sedative premedication.
BACKGROUND: Although multiple studies document the effect of sedative premedication on preoperative anxiety in children, there is a paucity of data regarding its effect on postoperative behavioral outcomes. METHODS: After screening for recent stressful life events, children undergoing anesthesia and surgery were assigned randomly to receive either 0.5 mg/kg midazolam in 15 mg/kg acetaminophen orally (n = 43) or 15 mg/kg acetaminophen orally (n = 43). Using validated measures of anxiety, children were evaluated before and after administration of the intervention and during induction of anesthesia. On postoperative days 1, 2, 3, 7, and 14, the behavioral recovery of the children was assessed using the Post Hospitalization Behavior Questionnaire. RESULTS: The intervention group demonstrated significantly lower anxiety levels compared with the placebo group on separation to the operating room and during induction of anesthesia (F[1,77] = 3.95, P = 0.041). Using a multivariate logistic regression model, the authors found that the presence or absence of postoperative behavioral changes was dependent on the group assignment (R = 0.18, P = 0.0001) and days after operation (R = -0.20, P = 0.0001). Post hoc analysis demonstrated that during postoperative days 1-7, a significantly smaller number of children in the midazolam group manifested negative behavioral changes. At week 2 postoperatively, however, there were no significant differences between the midazolam and placebo groups. CONCLUSIONS: Children who are premedicated with midazolam before surgery have fewer negative behavioral changes during the first postoperative week. (+info)
Ballistic shock wave lithotripsy in an 18-year-old thoroughbred gelding.
Prolonged postoperative recuperation time and restricted exercise were circumvented by using ballistic shock wave lithotripsy to break up an 8-cm diameter vesical calculus and by flushing out the sand-like residue under epidural anesthesia with the horse standing. Recovery was uneventful. (+info)
Morbidity and cost-effectiveness analysis of outpatient analgesia versus general anaesthesia for testicular sperm extraction in men with azoospermia due to defects in spermatogenesis.
The outcome and costs of testicular sperm extraction under outpatient local analgesia or general anaesthesia were compared in men with non-obstructive azoospermia. Nineteen consecutive patients were allocated to receive general anaesthesia, while the subsequent 21 consecutive patients received outpatient analgesia in the form of i.v. midazolam sedation, lignocaine spray, scrotal infiltration with local anaesthetic and spermatic cord block. Blood pressure, pulse rate and respiratory rate were determined. Sedation and testicular pain were assessed by subjective scoring. Both groups showed haemodynamic stability with little alteration in blood pressure, pulse rate and oxygen saturation. Toxic symptoms of local anaesthetic were not encountered in the outpatient group. No relationship was found between testicular size and the duration of the operation. The median postoperative pain intensity, sedation scores and analgesic requirements were significantly less in the outpatient group (P < 0.05). These advantages led to a shorter recovery time (P < 0.0001), 3-fold cheaper care and greater patient satisfaction (P < 0.0001) in the outpatient group. (+info)
Propofol concentrations in follicular fluid during general anaesthesia for transvaginal oocyte retrieval.
Propofol (Diprivan) is an i.v. anaesthetic used for general anaesthesia. The purpose of this study was to measure the propofol concentration in arterial blood and follicular fluid in patients during transvaginal oocyte retrieval. After approval by the University Ethics Committee, 30 women participated in this prospective study. Following induction of anaesthesia with 0.5 mg alfentanil and 2 mg.kg-1 propofol i.v., a continuous infusion of propofol at 10 mg.kg-1.h-1 was used for maintenance of anaesthesia. Follicular fluid and arterial blood samples were aspirated simultaneously at fixed intervals during the surgical procedure and propofol assayed by high pressure liquid chromatography (HPLC). The mean follicular fluid concentration of propofol increased linearly with time from 0.10 +/- 0.02 microgram.ml-1 to 0.57 +/- 0.06 microgram.ml-1 and was strongly related to the cumulative dose of propofol administered. The absorption of propofol was time-dependent. There was no correlation between the concentration of propofol in the follicular fluid and the arterial blood concentration of the drug. In conclusion, a propofol-based anaesthetic technique resulted in significant concentrations of this agent in follicular fluid, related to the dose administered and to the duration of propofol administration. (+info)
Assessing introduction of spinal anaesthesia for obstetric procedures.
To assess the impact of introducing spinal anaesthesia for obstetric operative procedures on use of general anaesthesia and quality of regional anaesthesia in a unit with an established epidural service a retrospective analysis of routinely collected data on method of anaesthesia, efficacy, and complications was carried out. Data were collected from 1988 to 1991 on 1670 obstetric patients requiring an operative procedure. The introduction of spinal anaesthesia in 1989 significantly reduced the proportion of operative procedures performed under general anaesthesia, from 60% (234/390) in 1988 to 30% (124/414) in 1991. The decrease was most pronounced for manual removal of the placenta (88%, 48/55 v 9%, 3/34) and emergency caesarean section (67%, 129/193) v 38%, 87/229). Epidural anaesthesia decreased in use most significantly for elective caesarean section (65%, 77/118 v 3% 3/113; x2=139, p<0.0001). The incidence of severe pain and need for conversion to general anaesthesia was significantly less with spinal anaesthesia (0%, 0/207 v 3%, 5/156; p<0.05). Hypotension was not a problem, and the incidence of headache after spinal anaesthetic decreased over the period studied. Introducing spinal anaesthesia therefore reduced the need for general anaesthesia and improved the quality of regional anaesthesia. (+info)