Distribution of the gamma-aminobutyric acid(A) receptor complex alpha 5 subunit in chick brain. An immunocytochemical and autoradiographic study

This work reports the distribution of the gamma-aminobutyric acid(A) (GABA(A)) receptor complex alpha5 subunit in the chick using an antibody raised against this subunit in the rat, an immunoprecipitation study and a comparative autoradiographic study using [(3)H]flunitrazepam in the presence of 1 microM zolpidem, which is considered to bind only to those areas presenting the alpha5 subunit. The specificity of the antibody for the chick GABA(A) receptor complex alpha5 subunit is supported by the similar bands obtained by Western blotting from rat and chick, the immunoprecipitation study and the general agreement in the distribution and pattern of labelling of this antibody in both species. The immunocytochemical and autoradiographic distributions in both the chick and rat are compared and some areas with disagreement between these distributions are discussed. The general conclusion is that the alpha5 subunit of the GABA(A) complex receptor seems to have been conserved along evolution.

Identification of benzodiazepine binding site residues in the gamma2 subunit of the gamma-aminobutyric acid(A) receptor

gamma-Aminobutyric acid(A) receptor gamma-subunits are important for benzodiazepine (BZD) binding and modulation of the gamma-aminobutyric acid-mediated Cl(-) current. Previously, by using gamma2/alpha1 chimeric subunits, we identified two domains of the gamma2-subunit, Lys-41-Trp-82 and Arg-114-Asp-161, that are, in conjunction, necessary and sufficient for high-affinity BZD binding. In this study, we generated additional gamma2/alpha1 chimeric subunits and gamma2 point mutants to identify specific residues within the gamma2 Lys-41-Trp-82 region that contribute to BZD binding. Mutant gamma2 and gamma2/alpha1 chimeric subunits were expressed with wild-type alpha1 and beta2 subunits in HEK 293 cells, and the binding of several BZDs was measured. We present evidence that the gamma2 region Met-57-Ile-62 is important for flunitrazepam binding and that, in particular, gamma2 Met-57 and gamma2 Tyr-58 are essential determinants for conferring high-affinity binding. Furthermore, we identify an additional residue, gamma2 Ala-79, that not only is important for high-affinity binding by flunitrazepam (a strong positive modulator) but also plays a crucial role in the binding of the imidazobenzodiazepines Ro15-1788 (a zero modulator) and Ro15-4513 (a weak negative modulator) in the BZD binding pocket. Results from site-directed mutagenesis of gamma2 Ala-79 suggest that this residue may be part of a microdomain within the BZD binding site that is important for binding imidazobenzodiazepines. This separation of drug-specific microdomains for competitive BZD ligands lends insight into the structural determinants governing the divergent effects of these compounds.

[Dependence on psychotropic drugs and substitution treatment: recent trends. The OPPIDUM study of the Centers for Evaluation and Information on Drug Dependence (CEIP), October 1997]

The aim of this study was to identify the latest trends in psychotropic drug use and the effect of the increase of maintenance treatments for serious opioid addiction. The results are based on data from OPPIDUM, an annual survey primarily concerned with the consumption of licit and illicit drugs. The study involved 1066 drug addicts recruited during the month of October 1997 from 38 French health centres connected with the Centres for Evaluation and Information on Drug Addiction (CEIP). The most frequently reported drugs were benzodiazepines (n = 323), some of which, especially flunitrazepam (Rohypnol, n = 123), are extremely addictive. The data showed a slight decrease in heroin consumption as well as a marked increase in the use of maintenance treatments. The association between benzodiazepines and buprenorphine (Subutex) should consequently be studied, whether buprenorphine is being used illicitly or prescribed as a maintenance treatment.

Prevalence, patterns, and correlates of voluntary flunitrazepam Use

OBJECTIVE

To determine prevalence, patterns, and correlates of voluntary flunitrazepam use in a sample of sexually active adolescent and young adult women 14 to 26 years of age.

DESIGN

Cross-sectional survey.

SETTING

University-based ambulatory reproductive health clinics.

PATIENTS OR OTHER PARTICIPANTS

There were 904 women self-identified as white, African-American, or Mexican-American.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

Lifetime, frequency, patterns, and physical effects of flunitrazepam use.

RESULTS

Lifetime use was reported by 5.9% (n = 53) of subjects, with frequency of use ranging from 1 to 40 times. Flunitrazepam was taken most often with alcohol (74%), and 49% took this substance with other illicit drugs. Logistic regression analyses controlling for age and race/ethnicity found that users were significantly more likely than were nonusers to report lifetime use of marijuana (odds ratio [OR] = 3.6) or LSD (OR = 5.2), having a peer or partner who used flunitrazepam (OR = 21.7), pressure to use flunitrazepam when out with friends (OR = 2.7), and a mother who had at least a high school education (OR = 2.6). Finally, 10% of voluntary users reported experiencing subsequent physical or sexual victimization.

CONCLUSIONS

Voluntary use of flunitrazepam is becoming a health concern to sexually active young women who reside in the southwestern United States. Young women who have used LSD or marijuana in the past or who have a peer or partner who used this drug appear to be at the greatest risk.

Abuse liability of flunitrazepam among methadone-maintained patients

Abuse liability and acute subjective and psychomotor effects of flunitrazepam were assessed in ten methadone-maintained males with history of benzodiazepine and alcohol use, who voluntarily participated in a double-blind, controlled, cross-over, randomized clinical trial. There were six experimental sessions in which a single oral dose of flunitrazepam 1, 2, and 4 mg; triazolam 0.5 and 0.75 mg; and placebo was given. Evaluations included physiological measures; psychomotor performance tasks (simple reaction time, Digit Symbol Substitution Test, balance task, Maddox-wing device); and self-administered subjective effects questionnaires [Addiction Research Center Inventory (ARCI), Profile of Mood States (POMS), a series of visual analog scales (VAS)]. All drugs but flunitrazepam 1 mg caused an impairment of psychomotor tasks. Effects were more evident with the highest doses of both drugs. Only flunitrazepam 4 mg produced a significant decrease in balance time. Triazolam 0.75 mg induced increases in sedation measured by ARCI-PCAG, depression in POMS, and VAS-drowsiness scores. Flunitrazepam 4mg caused euphoria-related effects as measured by increases in ARCI-MBG and "high" scores in the VAS. Our findings of flunitrazepam-induced euphoria in methadone-maintained subjects together with epidemiological evidence of flunitrazepam abuse by opioid dependents, suggest that it may be included in the group of benzodiazepines with a relatively high abuse potential.

Flunitrazepam and triazolam: a comparison of behavioral effects and abuse liability

The performance, observer-rated, and participant-rated effects of orally administered placebo, and two benzodiazepines, flunitrazepam (2, 4 and 8 mg/70 kg) and triazolam (0.25, 0.5 and 1 mg/70 kg), were compared in 14 sedative drug abusers using a double-blind crossover design. Both flunitrazepam and triazolam produced dose-related decrements in memory and psychomotor/cognitive performance, and increases in many participant- and observer-rated measures. Effects of flunitrazepam had an earlier onset and a longer duration than those of triazolam. Although there was evidence that the flunitrazepam doses selected for study were somewhat higher overall relative to the selected triazolam doses, analysis of the participant-rated measures collected 24 h after drug administration (next-day) suggests that flunitrazepam may have a greater abuse liability than triazolam when abuse liability is assessed 24 h after drug administration. The highest flunitrazepam dose produced effects that were significantly greater than those of the highest triazolam dose on next-day ratings of good effects, take again, and worth; all tested flunitrazepam doses produced effects greater than any triazolam dose on next-day ratings of liking and take again. The highest flunitrazepam dose, but no triazolam dose, significantly increased the maximum dollar value at which participants chose drug over money in a Drug versus Money Choice Procedure.

Rohypnol misuse in the United States

Rohypnol, a potent sedative-hypnotic drug prescribed extensively throughout the world, is illicit in the United States. Recently, this drug has gained popularity among United States youths as a cheap means of intoxication and subsequently has become the focus of numerous criminal investigations. College men are alleged to slip Rohypnol tablets into unsuspecting women's drinks and then sexually abuse their sedated victims. Although law enforcement agencies and drug policy groups consider Rohypnol to be an "imminent problem," little is actually known about patterns of misuse. Presented here is a brief overview of Rohypnol's contemporary appearance in the United States.

Determination of omeprazole in human plasma by high-performance liquid chromatography

A new method for the determination of omeprazole in human plasma was developed. Omeprazole was extracted from plasma with toluene-isoamylalcohol (95:5, v/v), the organic phase was evaporated, dissolved in the mobile phase and injected into a reversed-phase C18 column. Flunitrazepam was used as an internal standard. The mobile phase consisted of 47% methanol and 53% of 0.1 M dipotassium hydrogenphosphate, pH 7.8. The spectrophotometric detection was performed at 302 nm. Limit of quantitation was 9.7 ng/ml and the calibration curve was linear up to 1240 ng/ml.

Photoaffinity labeling of peripheral benzodiazepine receptors in R-3327 Dunning prostatic tumors

Photoaffinity labeling of peripheral benzodiazepine receptors (PBZr) in mitochondrial and microsomal fractions from AT-1, H, and G Dunning R-3327 tumor sublines was performed using the photoaffinity ligand 3H-PK 14105. Subsequent sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis (PAGE) revealed specific labeling of a 17 kDa protein in the microsomal fractions from these tumors. In the mitochondrial fractions, however, two bands with the apparent molecular mass of 17 and 18 kDa in AT-1 and H tumors were identified, whereas only the 17 kDa band was present in G tumors. Using another ligand, 3H-flunitrazepam, to photoaffinity label PBZr, proteins with molecular masses of 17, 30, 42, and 48 kDa were identified. These data suggest the possibility of different subclasses of PBZrs in Dunning prostatic tumors.

Abuse of flunitrazepam (Rohypnol) and other benzodiazepines in Austin and south Texas

Flunitrazepam (Rohypnol) is a benzodiazepine sedative-hypnotic that has generated significant media attention in the United States because of its abuse and its association with "date rape." A field investigation was conducted in south Texas to ascertain the nature and consequences of the abuse of flunitrazepam. In semistructured interviews, 66 subjects identified as flunitrazepam users were asked about their use of alcohol and other drugs and their sexual behaviors. Many subjects identified the drugs they had used as "roches" and gave descriptions of tablets of other benzodiazepines that were not consistent with flunitrazepam. Almost all subjects used other drugs, primarily alcohol and marijuana. Adverse consequences included amnesia, discoordination, automobile accidents, sexual assault, and respiratory depression or arrest. A significant proportion of the subjects reported that continued use was unappealing to them. The abuse of sedative-hypnotics in southeast Texas involves several benzodiazepines and is not limited to flunitrazepam.

Mapping of GABAA receptor sites that are photoaffinity-labelled by [3H]flunitrazepam and [3H]Ro 15-4513

The GABAA receptor in brain membranes prepared from bovine cerebral cortex and cerebellum has been photoaffinity-labelled by the classical benzodiazepine agonist, [3H]flunitrazepam, or by the partial inverse agonist [3H]Ro 15-4513. Following solubilization and precipitation with trichloroacetic acid, the photoaffinity-labelled receptor preparations were subjected to specific chemical cleavage using hydroxylamine, a reagent which cleaves specifically at a relatively rare Asn-Gly bond. The resulting peptides were resolved by denaturing polyacrylamide gel electrophoresis and mapping of these peptides to the known amino acid sequences of the GABAA receptor subunits has localized the photoaffinity-labelling sites for these two ligands to distinct portions of the alpha subunits. It is shown that the site for [3H]flunitrazepam photoaffinity-labelling in the receptor populations of both the cerebral cortex and cerebellum occurs within residues 1-103 of the bovine alpha 1 subunit sequence (or within analogous segments of homologous alpha subunits). In contrast, the site of photoaffinity-labelling by [3H]Ro 15-4513 in the cerebral cortex and in the diazepam-sensitive GABAA receptor population of the cerebellum lies between residues 104 and the carboxy-terminus of the bovine alpha 1 or homologous alpha subunits. However, the [3H]Ro 15-4513 photoaffinity-labelling site for the diazepam-insensitive receptors of the cerebellum is shown to occur within residues 1-101 (alpha 6 subunit numbering). These results demonstrate that the photoaffinity-labelling sites for [3H]flunitrazepam and [3H]Ro 15-4513 on the GABAA receptor are localized to distinct domains of the alpha 1 subunit and that [3H]Ro 15-4513 photoaffinity labels a site on the alpha 6 subunit that is unique from its site of labelling on the alpha 1 subunit.

Temporal lobe central benzodiazepine binding in unilateral mesial temporal lobe epilepsy

PET-demonstrated decreases in [11C]flumazenil binding occur in anterior mesial temporal structures on the side of epileptogenesis in unilateral mesial temporal lobe epilepsy. We performed quantitative autoradiography on anterior mesial and lateral temporal specimens from 11 subjects with unilateral mesial temporal lobe epilepsy and six neurologically normal controls to identify the predominant in vitro correlates of the decreased [11C]flumazenil binding. In anterior mesial temporal regions exhibiting the greatest neuronal cell loss, decreases in agonist and antagonist binding to type 1 and 2 (central) benzodiazepine binding sites were highly correlated with neuronal cell counts. Cell loss and decreased binding were particularly prominent in the lateral portion of hippocampal region CA1, adjacent to CA2. Lateral temporal central benzodiazepine binding was diffusely increased, achieving statistical significance in cortical laminae V and VI. These findings suggest that the predominant source of PET-demonstrated decreases in [11C]flumazenil binding in mesial temporal epilepsy is hippocampal sclerosis, rather than down-regulation of central benzodiazepine binding sites on surviving hippocampal neurons.

Comparison of two regional anesthetic techniques for knee arthroscopy

This study compares the efficacy of "3-in-1 block" versus femoral nerve block for knee arthroscopy. One-hundred patients had a 3-in-1 block; 180 patients had a femoral nerve block. The 3-in-1 block provided anesthesia in 75 patients; 20 patients needed supplementary local anesthesia. Five patients required a general anesthesia to complete the operation. The femoral nerve block was effective in 88 patients; 90 patients needed intravenous flunitrazepam and/or fentanyl; 2 patients needed general anesthesia. The 3-in-1 block provided more satisfactory muscle relaxation and a longer postoperative analgesia than femoral nerve block. No side effects were recorded in either group. Our results suggest that the 3-in-1 block is the most effective technique of regional anesthesia for knee arthroscopy.

Alterations in the brain GABAA/benzodiazepine receptor-chloride ionophore complex in a genetic model of paroxysmal dystonia: a quantitative autoradiographic analysis

Dystonia is a relatively common syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. The most frequent type of dystonia is idiopathic generalized dystonia, whose pathophysiology is largely unknown. In this respect, mutant animal strains with inborn dystonia may be helpful to elucidate the pathophysiological defects involved in idiopathic dystonia. The genetically dystonic (dtsz) hamster is an animal model of paroxysmal dystonia that displays attacks of generalized dystonia either spontaneously or in response to mild environmental stimuli. In the present study, a quantitative autoradiographic analysis of ligand binding to different sites of the GABAA/benzodiazepine receptor-chloride ionophore complex was carried out in 123 brain areas from genetically dystonic mutant hamsters and age-matched control hamsters. Animals were killed 2 weeks after their last dystonic attack. Analysis of the GABA-binding site of the receptor complex, using the ligand [3H]muscimol, and the benzodiazepine site labelled with [3H]flunitrazepam revealed no significant alterations in the binding of either ligand in any of the brain regions examined. In contrast, widespread changes were observed in binding densities of [35S]t-butylbicyclophosphorothionate ([35S]t-butylbicyclophosphorothionate), which labels the picrotoxinin site of the GABAA receptor-chloride ionophore complex. Significantly increased [35S]t-butylbicyclophosphorothionate binding was found in several parts of the thalamus, cortex, and hippocampus as well as in the red nucleus, the subthalamic nucleus, and the granular layer of the cerebellum. Since high-affinity [35S]TBPS binding is thought to represent the closed conformation of the GABA-gated chloride ionophore, increased TBPS binding would indicate an impaired GABAergic function. The study is consistent with the concept that dystonia is caused by impaired connections between the basal ganglia, the thalamus, and frontal association areas. The data on increased [35S]TBPS binding are the first evidence implicating alterations in the GABA-gated chloride ion channel function in a movement disorder, i.e. idiopathic generalized dystonia.

Ibotenic acid lesion of nucleus basalis magnocellularis differentially affects cholinergic, glutamatergic and GABAergic markers in cortical rat brain regions

The present study was undertaken to study the effect of reduced cortical cholinergic activity on gamma-aminobutyric acid (GABA)ergic and glutamatergic mechanisms in cholinoceptive cortical target regions which are assumed to play an important role for realizing cognitive functions. The densities of cortical muscarinic cholinergic receptor subtypes and corresponding receptor genes m1 through m4, N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) and kainate glutamate receptor subtypes as well as GABAA and benzodiazepine receptors were measured in rats 1 week after unilateral ibotenic acid lesion of the nucleus basalis magnocellularis (Nbm) applying quantitative receptor autoradiography and in situ hybridization. Ibotenic acid lesion resulted in a striking loss of acetylcholinesterase (AChE) staining in the lesioned Nbm which is associated with a 60% decrease in AChE staining and a 30% reduction in [3H]hemicholinium-3 binding in frontal and parietal cortical regions as well fore- and hindlimb areas ipsilateral to the lesion, being more prominent in the more rostral cortical regions. M1-muscarinic cholinergic receptor binding was not changed in any of the cortical regions studied 1 week after lesion. M2-muscarinic receptor binding levels are slightly increased in the parietal cortex only. The lesion-induced increase in parietal cortical M2-muscarinic receptor binding is complemented by an increase in the hybridization signal for the corresponding m4-mRNA transcript. In cortical regions displaying a reduced activity of AChE and decreased levels of high-affinity choline uptake sites due to forebrain cholinergic lesion, NMDA receptor binding was markedly reduced in comparison to the unlesioned brain side whereas AMPA and kainate binding has been significantly increased in these regions. Muscimol binding to GABAA receptors was increased in the rostral portions of frontal and parietal cortices as compared with the unlesioned brain side. Binding levels of benzodiazepine receptors were not affected by the lesion in any of the cortical regions studied. The differential changes in glutamate and GABA receptor subtypes following lesion might be regarded as the consequence of a cortical reorganization compensating for the reduced cholinergic presynaptic input. The data further suggest that presynaptic cortical cholinergic deficits might affect both glutamatergic and GABAergic functions with different intensity and different directions.

[Topographic changes in cerebral electric activity after premedication with flunitrazepam]

AIM

The effects on cerebral function of premedication with the benzodiazepine flunitrazepam and with morphine were studied on the evening of the preoperative day (2 mg flunitrazepam p.o.) and 90 minutes before induction of anaesthesia (2 mg flunitrazepam plus 15 mg morphine i.m.).

DESIGN

The EEG was analysed topographically (17 electrodes) and quantitatively.

RESULTS

As a typical effect of benzodiazepines, increases in electrical activity in the frequency band beta-1 of the power spectrum were observed, and could be demonstrated 10 minutes after oral application, mainly in the frontal and central parts of the cortex. Increases in the powerbands delta and theta indicated induction of sleep approximately 15-20 minutes after application and were not looked upon as an effect of the benzodiazepine exclusively. These increases were noticed first in the central, occipital and temporal areas and after 30 minutes in the frontal parts of the cortex. Flunitrazepam plus morphine showed qualitatively similar but quantitatively less pronounced results. Topographical differences were similar to the results of an application of flunitrazepam alone.

DISCUSSION

The results demonstrate the importance of a topographical as well as quantitative evaluation in studies on complex interactions of sedative or narcotic drugs and their clinical effects on cerebral function.

Motor signs of wakefulness during general anaesthesia with propofol, isoflurane and flunitrazepam/fentanyl and midlatency auditory evoked potentials

Auditory evoked potentials have been used as an indicator of awareness. In the present study we combined epidural analgesia with three techniques of general anaesthesia. Motor signs of intra-operative wakefulness were documented and assessed along with cardiovascular changes and with midlatency auditory evoked potentials. Thirty patients undergoing elective laparotomy were studied as follows: first continuous epidural analgesia was used in all patients to block painful sensation to the level of T5. Intravenous general anaesthesia was induced with propofol (2.5 mg.kg-1 b.w., group 1, n = 10), thiopentone (5 mg.kg-1 b.w., group 2, n = 10) or etomidate (0.2 mg.kg-1 b.w., group 3, n = 10) and maintained with a propofol (3-5 mg.kg-1, group 1), isoflurane (0.4-0.8 Vol%, group 2), flunitrazepam and fentanyl (0.005 mg.kg-1 b.w.) bolus injection every 20 to 30 s (group 3). Heart rate and arterial pressure were recorded continuously. Purposeful movements of the limbs, eye-opening or other movements as well as coughing were documented as motor signs of intra-operative wakefulness. Auditory evoked potentials were recorded in the awake state, after induction and during maintenance of general anaesthesia. Motor signs of intra-operative wakefulness occurred statistically significantly more often in the patients of the flunitrazepam/fentanyl group than in those of the propofol and isoflurane group. There was no correlation between wakefulness and cardiocirculatory parameters. In the awake patients midlatency auditory evoked potentials had high peak to peak amplitudes and a periodic waveform.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of sedation on otoacoustic emissions]

Even though the measurement of transitory evoked otoacoustic emissions (TEOAE) is easy and without problems in babies, sedation might be necessary in children aged between 1 and 4 years. As only very little information is available on the influence of a sedation on the TEOAE, the present study was performed. 35 normal hearing patients who were treated with benzodiazepines as a premedication for an operation were included in the investigation. 15 patients received diazepam and 20 were given flunitrazepam in a dosage of 10 and 1 mg respectively. The TEOAE were measured using the ILO 88 system by Bray and Kemp 1 day before, 1 hour after and 3 days after drug intake. 10 additional subjects of whom measurements were taken at the same time intervals served as controls. No statistically significant changes could be detected before and after drug treatment in respect of amplitudes of the TEOAE and frequency of maximum amplitudes. Hence, we conclude that sedation as used in this study must be considered negligible when measuring TEOAE.

[Anesthesia with flunitrazepam/fentanyl and isoflurane/fentanyl. Unconscious perception and mid-latency auditory evoked potentials]

There is a high incidence of intraoperative awareness during cardiac surgery. Mid-latency auditory evoked potentials (MLAEP) reflect the primary cortical processing of auditory stimuli. In the present study, we investigated MLAEP and explicit and implicit memory for information presented during cardiac anaesthesia. PATIENTS AND METHODS. Institutional approval and informed consent was obtained in 30 patients scheduled for elective cardiac surgery. Anaesthesia was induced in group I (n = 10) with flunitrazepam/fentanyl (0.01 mg/kg) and maintained with flunitrazepam/fentanyl (1.2 mg/h). The patients in group II (n = 10) received etomidate (0.25 mg/kg) and fentanyl (0.005 mg/kg) for induction and isoflurane (0.6-1.2 vol%)/fentanyl (1.2 mg/h) for maintenance of general anaesthesia. Group III (n = 10) served as a control and patients were anaesthetized as in I or II. After sternotomy an audiotape that included an implicit memory task was presented to the patients in groups I and II. The story of Robinson Crusoe was told, and it was suggested to the patients that they remember Robinson Crusoe when asked what they associated with the word Friday 3-5 days postoperatively. Auditory evoked potentials were recorded awake and during general anaesthesia before and after the audiotape presentation on vertex (positive) and mastoids on both sides (negative). Auditory clicks were presented binaurally at 70 dBnHL at a rate of 9.3 Hz. Using the electrodiagnostic system Pathfinder I (Nicolet), 1000 successive stimulus responses were averaged over a 100 ms poststimulus interval and analyzed off-line. Latencies of the peak V, Na, Pa were measured. V belongs to the brainstem-generated potentials, which demonstrates that auditory stimuli were correctly transduced. Na, Pa are generated in the primary auditory cortex of the temporal lobe and are the electrophysiological correlate of the primary cortical processing of the auditory stimuli. RESULTS. None of the patients had an explicit memory of intraoperative events. Five patients in group I, one patient in group II, and no patients in group III showed implicit memory of the intraoperative tape message. They remembered Robinson Crusoe spontaneously when they were asked their associations with Friday. In the awake state AEP peak latencies were in the normal range. During general anaesthesia in group I, the peaks Na, Pa did not increase in latency or decrease in amplitude before and after the audiotape presentation. The primary cortical complex Na/Pa could be identified as in the awake state. In contrast, in group II Na, Pa showed a marked increase in latency and a decrease in amplitude or were completely suppressed. CONCLUSIONS. During general anaesthesia auditory information can be processed and remembered postoperatively by an implicit memory function, when the electrophysiological conditions of primary cortical stimuli processing is preserved. Implicit memory can be observed more often when high-dose opioid analgesia is combined with receptor-binding agents like the benzodiazepines than under non-specific anaesthetics like isoflurane. Non-specific anaesthetics seem to provide a more effective suppression of auditory stimuli processing than receptor-specific agents.

[Changes in the cerebral hemodynamics during Rohypnol anesthesia in neurosurgical patients]

Intracranial pressure, cerebral perfusion pressure, and intracerebral blood volume changes were observed in 43 patients with volumetric intracranial processes (intracranial hematomas, tumors) during general rohypnol anesthesia. Intracranial and cerebral perfusion pressures were found to correlate with intracerebral blood volume. Rohypnol anesthesia decreased intracranial pressure by 25% due to reduced arterial blood influx into the head, mechanisms responsible for autoregulation of cerebral circulation being intact.

Midlatency auditory evoked potentials and explicit and implicit memory in patients undergoing cardiac surgery

BACKGROUND

A high incidence of intraoperative awareness during cardiac surgery has been reported. Midlatency auditory evoked potentials (MLAEP) have been used recently as an indicator of awareness. In the current study, memory for information presented during anesthesia was investigated using MLAEP as one experimental indicator in 45 patients scheduled for elective cardiac surgery.

METHODS

In all patients general anesthesia was maintained using high-dosage fentanyl (1.2 mg.h-1). In addition, the patients of group 1 (n = 10) received flunitrazepam (1.2 mg.h-1), the patients of group 2 (n = 10) isoflurane (0.6-1.2 vol%), and the patients of group 3 (n = 10) propofol (4-8 mg.kg-1.h-1). Group 4 (n = 15) served as a control, and those patients were assigned randomly to one of the anesthetic regimes. After sternotomy and before cardiopulmonary bypass, an audiotape, which included an implicit memory task, was presented to the patients of groups 1-3. Auditory evoked potentials were recorded while the patients were awake and during general anesthesia immediately before and after the audiotape presentation. Latencies of the brain stem peak V and the early cortical potentials Na and Pa were measured.

RESULTS

Three to 5 days postoperatively no patient had a clear explicit memory of intraoperative events. However, there were statistically significant differences in the incidence of implicit recall among the groups. Five patients in the flunitrazepam-fentanyl group, 1 patient in the isoflurane-fentanyl group, 1 patient in the propofol-fentanyl group, and no patient in the control group showed an implicit memory of the intraoperative tape message. In the awake state, MLAEP showed high peak-to-peak amplitudes and a periodic waveform. In the patients with implicit memory postoperatively, MLAEP continued to show this pattern during general anesthesia. The early cortical potentials Na and Pa did not increase in latency or decrease in amplitude before or after the audiotape presentation. In contrast, in the patients without implicit memory, MLAEP waveform was severely attenuated or abolished. Na and Pa showed marked increases in latencies and decreases in amplitudes or were completely suppressed. In 9 patients, including all patients (7 of 9) with implicit memory, Pa latency increased less than 12 ms, and 21 of 23 patients without implicit memory showed a Pa latency increase of greater than 12 ms during anesthesia and the audiotape presentation. Therefore, the Pa latency increase of greater or less than 12 ms may provide sensitivity of 100% and specificity of 77% in distinguishing patients with implicit memory from patients without implicit memory postoperatively.

CONCLUSIONS

When the early cortical potentials of MLAEP are preserved during general anesthesia, auditory information may be processed and remembered postoperatively by an implicit memory task.

Mid-latency auditory evoked potentials and circulatory response to loud sounds

We investigated in 60 patients scheduled for elective aorto-coronary bypass grafting if loud sounds by themselves can induce cardiovascular responses and if these could be related to mid-latency auditory evoked potentials (MLAEP). Anaesthesia was induced in group I (n = 20) with flunitrazepam-fentanyl 0.01 mg kg-1 and maintained with flunitrazepam-fentanyl 1.2 mg h-1. Patients in groups II (n = 20) and III (n = 20) received etomidate 0.25 mg kg-1 and fentanyl 0.005 mg kg-1 for induction and 0.6-1.2 vol% isoflurane and fentanyl 1.2 mg h-1, or propofol 4-8 mg kg-1 h-1 and fentanyl 1.2 mg h-1 for maintenance of general anaesthesia. After preparation of the sternum the operation was stopped for several minutes. Then, as a loud auditory stimulus, the sound of the running sternotomy saw was presented to the patients by putting the saw inverted on the sternum for several seconds. Heart rate (HR), arterial pressure (SAP), pulmonary capillary wedge pressure (PCWP), cardiac index, systemic vascular resistance and MLAEP were measured in the awake state, before and after presentation of the sound. Latencies of the peak V, Na, Pa, Nb and P1 were measured. In group I there were statistically significant increases in HR (63.5-70.2 beat min-1), SAP (123.9-146-5 mm Hg) and PCWP (9.2-11.7 mm Hg) after presentation of the sound. These haemodynamic changes were not observed in patients in groups II and III. In the awake state, AEP had high peak -to-peak amplitudes and a periodic waveform.(ABSTRACT TRUNCATED AT 250 WORDS)