Effect of intravenous S-ketamine on the MAC of sevoflurane: a randomised, placebo-controlled, double-blinded clinical trial.

BACKGROUND: Ketamine is routinely used in operating theatres, emergency departments, ICUs, and even outpatient units. Despite the widespread use of ketamine, only basic aspects of its interactions with inhalation anaesthetic agents are known, and formal testing of interactions in humans is lacking. The minimum alveolar concentration (MAC) of inhalation anaesthetics is used to guide the depth of anaesthesia, and several drugs are known to influence the MAC. The aim of this study was to investigate whether intravenous application of ketamine influences the MAC of sevoflurane in humans. METHODS: Adult patients undergoing elective surgery were included in this randomised, double-blinded, placebo-controlled study. Patients were assigned to one of three groups, each of which received a bolus of placebo, 0.5 mg kg-1S-ketamine, or 1 mg kg-1S-ketamine followed by an infusion of the same amount per hour after inhalation induction with sevoflurane was performed. The response to skin incision (movement vs non-movement) was recorded. The MAC of sevoflurane was assessed using an up-and-down titration method. RESULTS: Sixty patients aged 30-65 yr were included. Each group consisted of 20 patients. The MAC of sevoflurane was higher in the placebo group (2.1 (sd 0.1) %) than in the low-dose ketamine group (0.9 (0.1)%, P<0.01) and the high-dose ketamine group (0.5 (0.1)%, P<0.01). In addition, the MAC of sevoflurane was higher in the low-dose ketamine group compared with the high-dose ketamine group (P<0.01). CONCLUSIONS: The administration of S-ketamine significantly and dose-dependently reduced the MAC of sevoflurane in humans. CLINICAL TRIAL NUMBER: EudraCT ref. no. 2012-001908-38.

Intravenous lidocaine increases the depth of anaesthesia of propofol for skin incision--a randomised controlled trial.

BACKGROUND: The anaesthetic potency of intravenous propofol is quantified by its Cp50 value, which is defined as the plasma concentration required to prevent movement response in 50% of patients to surgical stimuli. We hypothesised that, in addition to propofol anaesthesia, an intravenous bolus of lidocaine 1.5 mg/kg will decrease the Cp50 value of propofol during anaesthesia. METHODS: We enrolled 54 elective surgical patients undergoing propofol-based anaesthesia, and randomised them to either lidocaine 1.5 mg/kg, lidocaine 0.5 mg/kg or placebo (NaCl 0.9%) 3 min before skin incision. The propofol Cp50 value was then calculated using the 'up-and-down' method of Dixon and Massey. RESULTS: There was no significant reduction in propofol requirements after the administration of 0.5 mg/kg lidocaine from 8.5 µg/ml [confidence interval (CI) 6.0-11.625] to 8.25 µg/ml (CI 6.75-9.76); however, a bolus of 1.5 mg/kg lidocaine decreased the Cp50 value of propofol by 42% from 8.5 µg/ml (CI 6.0-11.625) to 4.92 µg/ml (CI 4.5-5.78) (P < 0.05). CONCLUSION: An intravenous bolus injection of 1.5 mg/kg lidocaine 2% caused a significant reduction of the propofol Cp50 value.

In vivo / in vitro Correlation of Pharmacokinetics of Gentamicin, Vancomycin, Teicoplanin and Doripenem in a Bovine Blood Hemodialysis Model.

Background: Elimination of a drug during renal replacement therapy is not only dependent on flow rates, molecular size and protein binding, but is often influenced by difficult to predict drug membrane interactions. In vitro models allow for extensive profiling of drug clearance using a wide array of hemofilters and flow rates. We present a bovine blood based in vitro pharmacokinetic model for intermittent renal replacement therapy. Methods: Four different drugs were analyzed: gentamicin, doripenem, vancomicin and teicoplanin. The investigated drug was added to a bovine blood reservoir connected to a hemodialysis circuit. In total seven hemofilter models were analyzed using commonly employed flow rates. Pre-filter, post-filter and dialysate samples were drawn, plasmaseparated and analyzed using turbidimetric assays or HPLC. Protein binding of doripenem and vancomycin was measured in bovine plasma and compared to previously published values for human plasma. Results: Clearance values were heavily impacted by choice of membrane material and surface as well as by dialysis parameters such as blood flow rate. Gentamicin clearance ranged from a minimum of 90.12 ml/min in a Baxter CAHP-170 diacetate hemofilter up to a maximum of 187.90 ml/min in a Fresenius medical company Fx80 polysulfone model (blood flow rate 400 ml/min, dialysate flow rate 800 ml/min). Clearance of Gentamicin vs Vancomicin over the F80s hemofilter model using the same flow rates was 137.62 mL vs 103.25 ml/min. Doripenem clearance with the Fx80 was 141.25 ml/min. Conclusion: Clearance values corresponded very well to previously published data from clinical pharmacokinetic trials. In conjunction with in silico pharmacometric models. This model will allow precise dosing recommendations without the need of large scale clinical trials.

Estrogen increases endothelial carbon monoxide, heme oxygenase 2, and carbon monoxide-derived cGMP by a receptor-mediated system.

Carbon monoxide, a gaseous activator of soluble guanylyl cyclase formed by a subtype of the enzyme heme oxygenase designated heme oxygenase-2 in vascular endothelium, has been found to dilate blood vessels independently from nitric oxide. Because of the parallels between nitric oxide and carbon monoxide, we speculated that estrogen might affect carbon monoxide production in vascular endothelium. Endothelial cells of human origin (umbilical vein and uterine artery) were incubated for 4 or 24 h with 10(-12)-10(-6) M 17beta-estradiol. 17beta-Estradiol, at a concentration such as that attained during the ovulatory phase of the menstrual cycle (10(-10) M), administrated for 4 h led to a 2-fold increase in intracellular carbon monoxide production and heme oxygenase-2 protein levels (P < 0.05). A reporter assay, measuring the formation of cGMP as the direct product of carbon monoxide-induced activation of soluble guanylyl cyclase in endothelial cells, also revealed a 56% increase in cellular cGMP after treatment with 10(-10) M E2 17beta-estradiol (P < 0.05). By contrast, higher 17beta-estradiol concentrations had no significant respective effects due to nitric oxide synthase inhibition of carbon monoxide release. This 17beta-estradiol effect appeared to be ER dependent, as preincubation with tamoxifen (10(-6) M) blocked the stimulatory effect of 17beta-estradiol in each instance. Our preliminary data indicate a potential role for carbon monoxide as a biological messenger molecule in estrogen-mediated regulation of vascular tone.

Suicide by antidepressant intoxication identified at autopsy in Vienna from 1991-1997: the favourable consequences of the increasing use of SSRIs.

In the area of Vienna, any person dying under questionable circumstances is examined at the Institute of Forensic Medicine, where the cause of death is determined by means of autopsy and chemical analysis. Our study on fatal intoxications was performed in the period between 1991 and 1997, when selective serotonin reuptake inhibitors (SSRIs) were establishing themselves on the market, reaching the top of prescription statistics. Tricyclic antidepressants (TCAs) were involved in 30 single- and 127 multiple-substance intoxications, with amitriptyline and doxepin being the most frequently used drugs. SSRIs were involved in five multiple-substance intoxications. The f-value, which refers to the number of deaths per million defined daily doses prescribed, was found to be significantly (P

Different fatal toxicity of neuroleptics identified by autopsy.

Autopsies and toxicological analyses at the Institute of Forensic Medicine revealed 85 fatal intoxications with neuroleptics in Vienna from 1991 to 1997. A total of 17 cases were linked to a single neuroleptic (NL) alone, while 68 deaths were attributed to a combination of NLs with other drugs. The most frequently detected agent was prothipendyl (n=41). During the study period the number of defined daily doses of high-potency NLs prescribed increased significantly (P< or =0.001) due to increased prescribing of new atypical antipsychotics. The quantity of intermediate- and low-potency NLs dispensed remained stable. The most frequently prescribed NL was haloperidol. The relative toxicities of different NLs were calculated by dividing the number of deaths caused by this NL into the number of defined daily doses prescribed in the observation period (f-value). Single-substance intoxications and multiple-substance intoxications were distinguished. The highest f-values were associated with low-potency NLs, especially with prothipendyl, chlorprothixene and levomepromazine. Low f-values were found for the group of high-potency NLs, including flupentixol, fluphenazine, haloperidol and pimozide, as well as olanzapine. Compared to the f-values for all NLs prescribed, f-values for low-potency NLs were shown to be significantly higher concerning single-substance intoxications (P< or = 0.05) and multiple-substance intoxications (P < or = 0.001), while f-values for high-potency NLs were significantly lower (P< or = 0.05 and P< or = 0.001). We are not aware of the psychiatric diagnoses in our post-mortem sample. However, the present results indicate that careless use of low-potent NLs should be avoided in patients with a potential risk of accidental or suicidal overdose.

Prediction of gas chromatographic retention indices of a diverse set of toxicologically relevant compounds.

For a set of 846 organic compounds, relevant in forensic analytical chemistry, with highly diverse chemical structures, the gas chromatographic Kovats retention indices have been quantitatively modeled by using a large set of molecular descriptors generated by software Dragon. Best and very similar performances for prediction have been obtained by a partial least squares regression (PLS) model using all considered 529 descriptors, and a multiple linear regression (MLR) model using only 15 descriptors obtained by a stepwise feature selection. The standard deviations of the prediction errors (SEP), were estimated in four experiments with differently distributed training and prediction sets. For the best models SEP is about 80 retention index units, corresponding to 2.1-7.2% of the covered retention index interval of 1110-3870. The molecular properties known to be relevant for GC retention data, such as molecular size, branching and polar functional groups are well covered by the selected 15 descriptors. The developed models support the identification of substances in forensic analytical work by GC-MS in cases the retention data for candidate structures are not available.

Automatic screening in postmortem toxicology.

The systematic analysis of postmortem samples is one of the most challenging tasks in forensic toxicology. For determining cause of death, analysis of different tissues can be indispensable. Automation of these analyses would increase reproducibility and therefore lead to more reliable and comparable results. Recent developments in analytical toxicology and the availability of automation devices for various analytical stages, such as sampling, preliminary testing, sample extraction, chromatographic separation, identification, and data processing are examined and discussed. At present only parts of the analytical procedure have been automated-however, the goal should be the integration of these parts into a single, continuous process. Currently, only one "fully-automated" procedure for the comprehensive screening of blood and urine (excluding sample pretreatment, which remains separate) has been published. But it can be expected that automation of analytical procedures in forensic toxicology will indeed progress, even with regard to the very complex screening of postmortem samples.

Identification of the general unknown. Application of mass selective detectors in forensic toxicology.

One of the basic aims of forensic toxicology is the identification of previously unknown drugs and poisons. This is frequently achieved using the combination of gas chromatography and benchtop quadrupole or ion trap mass spectrometers. The influence of matrix loading on the mass spectral quality was tested, and it was found that a realistic amount of matrix changed the pattern of the spectra obtained by the ion trap mass spectrometer. Disturbed mass spectra led to unsuitable suggestions from the library search and thus rendered the identification of the "general unknown" more difficult. On the other hand, higher selectivity and lower detection limits favored the ion trap technology for target analysis because of the capability of MS-MS.

General unknown screening in postmortem tissue and blood samples: a semi-automatic solid-phase extraction using polystyrene resins followed by liquid-liquid extraction.

The identification of general unknown poisons in complex biological materials like postmortem blood and tissue is a great challenge for the forensic toxicologist. Therefore, a screening procedure utilizing a semi-automatic work-up with an ASPEC system was developed. A broad range of different compounds can be isolated by using non-selective and generally applicable organic polymeric sorbents such as OASIS HLB or Isolute 101. Because colloidal solutions were applied to these sorbents, the denaturation of proteins, which can result in an irreversible loss of significant compounds by adsorption and occlusion, could be avoided. Because of the process of micellar chromatography followed by liquid-liquid extraction of the crude extract, very clean fractions were obtained from such complex matrices as postmortem blood, liver, and brain samples. High recoveries (72-100%) and good day-to-day relative standard deviations (1-17%) could be achieved with both polymeric sorbents. The procedure paves the way for the identification of general unknown poisons in target organs and is therefore a useful tool in the field of forensic toxicology.

Drugs and driving in Vienna, Austria.

Drugs that affect the central nervous system are generally assumed to have the potential to impair driving ability. In a retrospective survey, police files and the results of toxicological urine analysis from drivers suspected of driving under the influence of drugs in Vienna from 1993 to 1996 were investigated. Decisive for police intervention was "unsafe driving" (swerving, hesitating, going too slowly, etc.), driving at high speed within the city limits, driving through red lights or stop signs, and driving at night without lights. In one-fifth of the cases drivers caused a traffic accident. Casting suspicion on driving under influence of drugs was mainly caused by impaired coordination of movements, bloodshot eyes, slurred speech, drowsiness, conspicuous behavior, and changed pupils. In the majority of the study population more than two symptoms were recorded by police. In 94% of the cases police suspicions could be confirmed by toxicological urine analysis.

Suicidal chloroquine poisoning: clinical course, autopsy findings, and chemical analysis.

Suicidal overdose of chloroquine is rare. We present a 14-year-old girl who was admitted to our Emergency Department after intentional ingestion of 7.5 g of chloroquine base followed by cardiac and respiratory arrest. Despite early mechanical ventilation, cardiac support, and treatment with high doses of diazepam, the patient died. Laboratory investigation indicated disseminated intravascular coagulation confirmed by petechial hemorrhages in the leptomeninges at autopsy, a finding that has not previously been described. Postmortem tissue analysis demonstrated early drug distribution to the medulla oblongata and cerebellum.

[Fatal methadone poisoning of a child]. / Tödliche Vergiftung eines Kindes mit Methadon.

The substance methadone is used for substitution therapy since the 1960s in the U.S. Mainly because of the endemic spread of HIV-1 infections among intravenous drug abusers methadone was made legally available through medical prescription in Austria in 1987. Legal authorities today also allow the patient to take home the necessary daily consumption for weekends or public holidays. The drug is distributed as a watery solution in tiny bottles, which are fitted with an ordinary screw cap. This kind of distribution may, however, have fatal consequences. This is demonstrated in the following case of accidental poisoning of an infant: A two-year-old girl whose parents were both participating in the substitution scheme was found dead in her bed in Vienna in 1997. Forensic autopsy revealed a methadone concentration in the liver tissue of 640 ng/g. The criminal investigation determined that the girl had opened a bottle of methadone solution and subsequently had taken the drug. Considering the circumstances of this accident, from the medical point of view safety devices for the screw caps of the methadone bottles should be required by law, in order to avoid future accidental poisoning.

Distribution of drugs of abuse within specific regions of the human brain.

Since concentration of drugs of abuse found in the brain better reflect drug concentration at their site of action, brain specimens are useful in the determination of the role of drugs of abuse in the cause of death. In order to allow for the routine use of brain specimens in this field, a comprehensive database with reliable reference values is needed and should include both post-mortem data for cases where drugs have been taken in therapeutic doses as well as for cases of overdose. In this study, a semi-automated extraction procedure, in combination with gas chromatography/mass spectrometry (GC-MS) using stable isotope internal standards was applied to yield reproducible, quantitative results which could be used to investigate the distribution patterns of drugs of abuse within specific regions of the brain, by analyzing several segments of both medulla oblongata and cerebellum. A homogenous distribution of unconjugated morphine, dihydrocodeine, and benzoylecgonine within the investigated segments of medulla oblongata or cerebellum could be found. However, when these two brain regions from the same case were compared to each other, significantly higher concentrations of unconjugated morphine, dihydrocodeine, and benzoylecgonine were found in the cerebellum than in the medulla oblongata.

Pharmacokinetic studies of the fragrance compound 1,8-cineol in humans during inhalation.

The present study was undertaken to investigate the pharmacokinetics of 1,8-cineol in human subjects during prolonged inhalation. The results showed that 1,8-cineol is well absorbed from breathing air, with a peak plasma concentration after approximately 18 min. The elimination of this fragrance compound from the blood is biphasic, with a mean distribution half-life of 6.7 min and an elimination half-life of 104.6 min.

Direct current auditory evoked potentials during wakefulness, anesthesia, and emergence from anesthesia.

Direct current auditory evoked potentials (DC-AEPs) are a sensitive indicator of depth of anesthesia in animals. However, they have never been investigated in humans. To assess the potential usefulness of DC-AEPs as an indicator of anesthesia in humans, we performed an explorative study in which DC-AEPs were recorded during propofol and methohexital anesthesia in humans. DC-AEPs were recorded via 22 scalp electrodes in 19 volunteers randomly assigned to receive either propofol or methohexital. DC-AEPs were evoked by binaurally presented 2-s, 60-dB, 800-Hz tones; measurements were taken during awake baseline, anesthesia, and emergence. Statistical analysis included analysis of variance and discriminant analysis of data acquired during these three conditions. About 500 ms after stimulus presentation, DC-AEPs could be observed. These potentials were present only during baseline and emergence-not during anesthesia. Statistically significant differences were found between baseline and anesthesia and between anesthesia and emergence. In conclusion, similar effects, as reported in animal studies of anesthetics on the DC-AEPs, could be observed in anesthetized humans. These results demonstrate that DC-AEPs are potentially useful in the assessment of cortical function during anesthesia and might qualify the method for monitoring anesthesia in humans.

[Fatal poisonings with antidepressive drugs and neuroleptics. Analysis of a correlation with prescriptions in Vienna 1991 to 1997]. / Letale Intoxikationen mit Antidepressiva und Neuroleptika. Analyse im Zusammenhang mit den Verordnungen in Wien von 1991 bis 1997.

As a result of the increasing use of selective serotonin reuptake inhibitors (SSRI), the number of antidepressants (AD) prescribed in Vienna doubled from 1991 to 1997. In the same period, autopsies and chemical analyses performed at the Institute of Forensic Medicine, University of Vienna, revealed a total of 164 fatal intoxications by means of AD. In this study, the number of fatal intoxications per million defined daily doses prescribed was determined and referred to as the fatal toxicity index (f-index). For both single- and multiple-substance intoxications, it proved to be significantly (p < 0.001) lower with SSRI than with tricyclic antidepressants (TCA). Single-substance intoxications (n = 30) were seen exclusively in TCA. Concerning neuroleptics (NL), the increase in prescriptions observed in the study period (plus 30%) was less pronounced, and they were found to be involved in 85 fatal intoxications. Also in NL, those of the tricyclic type (TCNL) showed a significantly (p < 0.001) higher f-index than other groups. Out of a total of 17 single-substance intoxications, 14 were caused by TCNL and none by butyrophenones or haloperidol. The present study demonstrates that the prescription of TCA or TCNL involves a relatively high risk of fatal intoxication.

Sudden, unexpected death of a young marathon runner as a result of bronchial malformation.

Deaths of young athletes are mainly caused by cardiac problems. Noncardiac deaths are infrequent and related to heat stress, drugs, sickle cell trait, and asthma. Herein, we report the case of a 28-year-old man, who collapsed during a marathon race, within sight of the finish line. Despite immediate resuscitation, he died shortly after hospitalization. Autopsy findings revealed neither unambiguous cardiac nor previously published noncardiac causes. Traumatic or drug-related death was excluded as well. We did find, however, focally hyperinflated pulmonary areas adjacent to atelectasis, interstitial emphysema, and mucosal infoldings of several bronchi. Histologically, two-thirds of medium-sized bronchi presented paucity of cartilages. Hence, the resulting flaccidity of the bronchial wall might cause bronchial obstruction, which we related to the genesis of this sudden and unexpected death.

Successful resuscitation of a verapamil-intoxicated patient with percutaneous cardiopulmonary bypass.

OBJECTIVE: To describe our experience with the use of percutaneous cardiopulmonary bypass as a therapy for cardiac arrest in an adult patient intoxicated with verapamil. DESIGN: Case report. SETTING: Emergency department of a university hospital. PATIENT: A patient with cardiac arrest after severe verapamil intoxication. INTERVENTIONS: Percutaneous cardiopulmonary bypass and theophylline therapy. CASE REPORT: A 41-yr-old white male had taken 4800-6400 mg of verapamil in a suicide attempt. On arrival of the ambulance physician, the patient was conscious with weak palpable pulses and was transported to a nearby hospital. The patient developed a pulseless electrical activity, and cardiopulmonary resuscitation was started. Despite all advanced life support efforts, the patient remained in cardiac arrest. Therefore, he was transferred under ongoing cardiopulmonary resuscitation to our department, where percutaneous cardiopulmonary bypass was initiated immediately (2.5 hrs after cardiac arrest). The first verapamil serum concentration obtained at admittance to our institution was 630 ng/mL. After several ineffective intravenous epinephrine applications, the administration of 0.48 g of theophylline as an intravenous bolus 6 hrs and 18 mins after cardiac arrest led to the return of spontaneous circulation. The patient remained stable and was transferred to an intensive care unit the same day. He woke up on the 12th day and was extubated on the 18th day. After transfer to a neuropsychiatric rehabilitation hospital, he recovered totally. CONCLUSION: In patients with cardiac arrest attributable to massive verapamil overdose, percutaneous extracorporeal cardiopulmonary bypass can provide adequate tissue perfusion and sufficient cerebral oxygen supply until the drug level is reduced and restoration of spontaneous circulation can be achieved.