Sudden, unexpected cardiac or unexplained death in England: a national survey.

BACKGROUND: Post-mortem examinations of adults who were apparently healthy but died suddenly and unexpectedly sometimes reveal no morphological abnormalities to explain their deaths. The frequency of such unexplained deaths in relation to other causes of sudden cardiac death is not known. AIM: To estimate the frequency of sudden unexpected cardiac or unexplained death in England. DESIGN: Prospective survey using a stratified random sample of 83 of the 132 H.M. Coroner's jurisdictions in England. METHODS: Consecutive White Caucasians, aged 16-64 years, with no medical history of cardiac disease, seen alive within 12 h of death, on whom autopsy found either a cardiac or no identifiable cause of death, were included. The coroner's officer sent a copy of the post-mortem report and a completed case registration form to the investigators, with tissue samples. RESULTS: Sixty-seven (81%) coroners participated, each maintaining prospective surveillance for 4 months. Of 692 ascertained cases, case registration forms were received for 650 (94%), post-mortem reports for 682 (99%), blood samples for 569 (82%), myocardial slices for 517 (75%) and whole hearts for 47 (7%). In cases with myocardial tissue, death was ascribed to ischaemic heart disease in 465 (82.4%). In 43.1% the ischaemia was acute, in 19.1% there was myocardial scarring but no acute ischaemia, and 20.2% had coronary atheroma only. Death was due to left ventricular hypertrophy in 32 (5.7%), to other cardiac causes in 30 (5.3%) and in 23 (4.1%) there was no clear cause. Those with cardiac causes were 81% male, median ages 55.9 (male) and 56.6 (female) years. The 23 unexplained deaths were 57% female, median ages 40.5 (male) and 54.9 (female) years. The estimated annual frequency of sudden unexpected death due to cardiac or unidentified causes, in English adults of employment age, was 11/100,000 (3481 annual deaths). DISCUSSION: In 4.1% of sudden unexpected deaths under 65 years, no cause was found. Until it becomes accepted practice to identify these cases by a name, such as Sudden Adult Death Syndrome (SADS), it will not be possible to study their aetiology systematically.

Catechol-O-methyltransferase (COMT)-mediated metabolism of catechol estrogens: comparison of wild-type and variant COMT isoforms.

The oxidative metabolism of 17beta-estradiol (E2) and estrone (E1) to catechol estrogens (2-OHE2, 4-OHE2, 2-OHE1, and 4-OHE1) and estrogen quinones has been postulated to be a factor in mammary carcinogenesis. Catechol-O-methyltransferase (COMT) catalyzes the methylation of catechol estrogens to methoxy estrogens, which simultaneously lowers the potential for DNA damage and increases the concentration of 2-methoxyestradiol (2-MeOE2), an antiproliferative metabolite. We expressed two recombinant forms of COMT, the wild-type (108Val) and a common variant (108Met), to determine whether their catalytic efficiencies differ with respect to catechol estrogen inactivation. The His-tagged proteins were purified by nickel-nitrilo-triacetic acid chromatography and analyzed by electrophoresis and Western immunoblot. COMT activity was assessed by determining the methylation of 2-OHE2, 4-OHE2, 2-OHE1, and 4-OHE1, using gas chromatography/mass spectrometry for quantitation of the respective methoxy products. In the case of 2-OHE2 and 2-OHE1, methylation occurred at 2-OH and 3-OH groups, resulting in the formation of 2-MeOE2 and 2-OH-3-MeOE2, and 2-MeOE1 and 2-OH-3-MeOE1, respectively. In contrast, in the case of 4-OHE2 and 4-OHE1, methylation occurred only at the 4-OH group, yielding 4-MeOE2 and 4-MeOE1, respectively. Individual and competition experiments revealed the following order of product formation: 4-MeOE2 > 4-MeOE1 >> 2-MeOE2 > 2-MeOE1 > 2-OH-3-MeOE1 > 2-OH-3-MeOE2. The variant isoform differed from wild-type COMT by being thermolabile, leading to 2-3-fold lower levels of product formation. MCF-7 breast cancer cells with the variant COMT 108Met/Met genotype also displayed 2-3-fold lower catalytic activity than ZR-75 breast cancer cells with the wild-type COMT 108Val/Val genotype. Thus, inherited alterations in COMT catalytic activity are associated with significant differences in catechol estrogen and methoxy estrogen levels and, thereby, may contribute to interindividual differences in breast cancer risk associated with estrogen-mediated carcinogenicity.

Neonatal pulmonary hypertension--urea-cycle intermediates, nitric oxide production, and carbamoyl-phosphate synthetase function.

BACKGROUND: Endogenous production of nitric oxide is vital for the decrease in pulmonary vascular resistance that normally occurs after birth. The precursor of nitric oxide is arginine, a urea-cycle intermediate. We hypothesized that low concentrations of arginine would correlate with the presence of persistent pulmonary hypertension in newborns and that the supply of this precursor would be affected by a functional polymorphism (the substitution of asparagine for threonine at position 1405 [T1405N]) in carbamoyl-phosphate synthetase, which controls the rate-limiting step of the urea cycle. METHODS: Plasma concentrations of amino acids and genotypes of the carbamoyl-phosphate synthetase variants were determined in 65 near-term neonates with respiratory distress. Plasma nitric oxide metabolites were measured in a subgroup of 10 patients. The results in infants with pulmonary hypertension, as assessed by echocardiography, were compared with those in infants without pulmonary hypertension. The frequencies of the carbamoyl-phosphate synthetase genotypes in the study population were assessed for Hardy-Weinberg equilibrium. RESULTS: As compared with infants without pulmonary hypertension, infants with pulmonary hypertension had lower mean (+/-SD) plasma concentrations of arginine (20.2+/-8.8 vs. 39.8+/-17.0 micromol per liter, P<0.001) and nitric oxide metabolites (18.8+/-12.7 vs. 47.2+/-11.2 micromol per liter, P=0.05). As compared with the general population, the infants in the study had a significantly skewed distribution of the genotypes for the carbamoyl-phosphate synthetase variants at position 1405 (P<0.005). None of the infants with pulmonary hypertension were homozygous for the T1405N polymorphism. CONCLUSIONS: Infants with persistent pulmonary hypertension have low plasma concentrations of arginine and nitric oxide metabolites. The simultaneous presence of diminished concentrations of precursors and breakdown products suggests that inadequate production of nitric oxide is involved in the pathogenesis of neonatal pulmonary hypertension. Our preliminary observations suggest that the genetically predetermined capacity of the urea cycle--in particular, the efficiency of carbamoyl-phosphate synthetase--may contribute to the availability of precursors for nitric oxide synthesis.

Cytochrome P450 1B1 (CYP1B1) pharmacogenetics: association of polymorphisms with functional differences in estrogen hydroxylation activity.

Activation of 17beta-estradiol (E2) through the formation of catechol estrogen metabolites, 2-OH-E2 and 4-OH-E2, and the C-16alpha hydroxylation product, 16alpha-OH-E2, has been postulated to be a factor in mammary carcinogenesis. Cytochrome P450 1B1 (CYP1B1) exceeds other P450 enzymes in both estrogen hydroxylation activity and expression level in breast tissue. To determine whether inherited variants of CYP1B1 differ from wild-type CYP1B1 in estrogen hydroxylase activity, we expressed recombinant wild-type and five polymorphic variants of CYP1B1: variant 1 (codon 48Arg-->Gly), variant 2 (codon 119Ala-->Ser), variant 3 (codon 432Val-->Leu), variant 4 (codon453Asn-->Ser), variant 5 (48Gly, 119Ser, 432Leu, 453Ser). The His-tagged proteins were purified by nickel-nitrilotriacetic acid (Ni-NTA) chromatography and analyzed by electrophoresis and spectrophotometry. We performed assays of E2 hydroxylation activity and quantitated production of 2-OH-E2, 4-OH-E2, and 16alpha-OH-E2 by gas chromatography/mass spectrometry. Wild-type CYP1B1 formed 4-OH-E2 as main product (Km, 40+/-8 microM; k(cat) 4.4+/-0.4, min(-1); k(cat)/Km, 110 mM(-1) min(-1)), followed by 2-OH-E2 (Km, 34+/-4 microM; k(cat), 1.9+/-0.1 min(-1); k(cat)/Km, 55 mM(-1)min(-1)) and 16alpha-OH-E2 (Km, 39+/-5.7 microM; k(cat), 0.30+/-0.02 min(-1); k(cat)/Km, 7.6 mM(-1)min(-1)). The CYP1B1 variants also formed 4-OH-E2 as the main product but displayed 2.4- to 3.4-fold higher catalytic efficiencies k(cat)/Km than the wild-type enzyme, ranging from 270 mM(-1)min(-1) for variant 4, to 370 mM(-1)min(-1) for variant 2. The variant enzymes also exceeded wild-type CYP1B1 with respect to 2- and 16alpha-hydroxylation activity. Thus, inherited alterations in CYP1B1 estrogen hydroxylation activity may be associated with significant changes in estrogen metabolism and, thereby, may possibly explain interindividual differences in breast cancer risk associated with estrogen-mediated carcinogenicity.

Physiologic effects of anesthesia induced and maintained by intravenous administration of a climazolam-ketamine combination in ponies premedicated with acepromazine and xylazine.

OBJECTIVE: To examine the physiologic and pharmacokinetic effects of a technique of total intravenous anesthesia in ponies. ANIMALS: 6 healthy ponies. PROCEDURE: Ponies were premedicated with acepromazine (0.03 mg/kg of body weight, IV) and xylazine (1.0 mg/kg, IV). Two minutes later, anesthesia was induced with ketamine (2.0 mg/kg, IV) followed by climazolam (0.2 mg/kg, IV). Anesthesia was maintained for 120 minutes by an infusion of climazolam (0.4 mg/kg/h) and ketamine (6.0 mg/kg/h). Oxygen (5 L/min) was supplemented. 20 minutes after the infusion was stopped sarmazenil (0.04 mg/kg, IV) was administered. Cardiovascular and respiratory function measurements were taken before and after premedication, and during anesthesia. Plasma cortsol, ACTH, and catecholamine concentrations were used to assess adrenal and pituitary gland function Ketamine and climazolam kinetics were calculated, on the basis of plasma drug concentrations. RESULTS: There were no significant changes from pre-xylazine values in heart rate, respiratory rate, arterial blood pressure, cardiac index, systemic vascular resistance, or arterial PO2, PCO2, and pH. Plasma cortisol concentration decreased during anesthesia, but plasma ACTH and catecholamine concentrations did not change. Recovery was fairly smooth, but some excitement and ataxia were noted in 2 ponies. CONCLUSION: Ketamine-climazolan infusion appeared suitable for maintenance of anesthesia in ponies, although recovery was not ideal in 2 of 6 ponies.

Thyroxine replacement increases central 5-hydroxytryptamine activity and reduces depressive symptoms in hypothyroidism.

Hypothyroidism is associated with both reduced central 5-HT function and an increased incidence of depression. This study tested the hypothesis that the reduced 5-HT function returns to normal with thyroxine replacement therapy. Seven hypothyroid patients were tested before and after adequate thyroxine replacement. Cortisol and prolactin responses to d-fenfluramine, a centrally acting 5-HT-releasing agent, were used as an index of central (hypothalamic) 5-HT responsiveness. 5-HT-mediated cortisol responses were significantly higher after thyroxine replacement. Basal prolactin levels were reduced, but 5-HT-mediated prolactin responses were not significantly higher after treatment, perhaps due to the pre-treatment responses being elevated by the direct stimulatory effects of hypothyroidism itself on pituitary prolactin secretion. Depressive symptomatology improved with thyroxine. TSH levels were positively related to depressive symptomatology, and inversely to cortisol responses. Depressive symptomatology was inversely related to cortisol responses. These findings thus provide further support that central 5-HT neurotransmission is affected by hypothyroidism. They also suggest that the reduction in 5-HT responsiveness is reversible with thyroxine replacement therapy.

Systemic absorption and abuse liability of snorted flunitrazepam.

Benzodiazepine hypnotics are widely abused as part of a polydrug misuse culture. This study set out to investigate some pharmacokinetic and pharmacodynamic characteristics of a novel method of abuse, snorting, of flunitrazepam. Twenty healthy volunteers took part: three took 0.5 mg, three took 1 mg, three took 1.5 mg, six took 2 mg and five took placebo. Blood was sampled and ratings of mood, bodily symptoms, strength and liking of drug effect were completed pre- and at 5, 15, 30, 60, 90, 120 and 240 minutes and at 24 hours post-drug. It was found that flunitrazepam could be detected in venous blood 5 minutes after intake. As the dose increased, the peak plasma concentration was higher but also occurred progressively later, the levels reached being comparable to oral or intramuscular administration at 110 minutes. Subjects reported sedation but complained of few side-effects. They liked the drug effects and subjective ratings of strength were correlated with liking and with plasma drug levels.

Systemic paraphenylenediamine (PPD) poisoning: a case report and review.

A case of suicidal poisoning with paraphenylenediamine (PPD) is reported. The patient presented with typical features of severe oropharyngeal oedema and rhabdomyolysis. He suffered sudden cardiac death within 4 hours of admission despite full supportive treatment. The diagnosis was only established after his death. Systemic poisoning with paraphenylenediamine (PPD) is rare in western countries, and therefore a high degree of awareness and circumstantial evidence is required to make an early diagnosis. The classical and other less commonly reported features of this poisoning are discussed. There is no specific antidote available but some guidelines for management of such a case are reviewed.

Folinic acid and enhanced renal elimination in formic acid intoxication.

Ingestion of over 60 g of formic acid by an adult is potentially fatal. We report a case of a 36-year-old woman with a history of depression who ingested 110 g of formic acid. She survived a complicated intensive care hospitalization following usage of intravenous folinic acid, urinary alkalinization, intravenous furosemide and supportive care. We suggest a management protocol aimed at minimizing formate toxicity by enhancing hepatic formate degradation via the folinic acid 'one carbon pool' and by enhanced renal elimination of formate.

Accidental ingestion of 'Ecstasy' (3,4-methylenedioxymethylamphetamine).

There is no report of the effects of 'Ecstasy' (3,4-methylenedioxymethylamphetamine) poisoning in childhood. The case of a 13 month old boy who ingested one capsule of Ecstasy is reported. Neurological and cardiovascular side effects predominated, which responded well to treatment with a chlormethiazole infusion.

Toxicity and deaths from 3,4-methylenedioxymethamphetamine ("ecstasy")

The risk of adverse reactions to 3,4-methylenedioxymethamphetamine (MDMA), more commonly known as "ecstasy", is now widely known in both the USA and UK, but the patterns of illness remain varied. We report our experience during 1990 and 1991. There has been a recent increase in cases of severe toxicity following recreational misuse of small amounts of MDMA. Among 7 fatalities, the pattern of toxicity included fulminant hyperthermia, convulsions, disseminated intravascular coagulation, rhabdomyolysis, and acute renal failure. Until now, there have been few reports of this type of toxicity from MDMA, which may be related both to the potential of the drug to alter thermoregulation and to the circumstances of misuse. In addition, we have monitored 7 cases of hepatotoxicity and suspect that the frequency of this complication is increasing; a history of MDMA misuse should be sought in young people presenting with unexplained jaundice or hepatomegaly. We also describe 5 subjects involved in road traffic accidents in whom MDMA was identified. Misuse of MDMA can have severe acute toxic effects; few data are available concerning long-term morbidity, and this deserves close monitoring in future.

Noradrenaline uptake inhibition increases melatonin secretion, a measure of noradrenergic neurotransmission, in depressed patients.

Eight patients with endogenous depression who had received no antidepressant treatment for the previous year were treated with the noradrenaline (NA) uptake inhibitor, desipramine (DMI). Pre-treatment plasma melatonin concentrations were normal. After one day of DMI treatment plasma melatonin concentrations were increased but the response was impaired compared to normal subjects. The acute effect of DMI on plasma melatonin persisted after six weeks of treatment. These findings question the hypothesis that beta adrenoceptors are supersensitive in depression and that antidepressant drugs act by down-regulating these receptors.

Abolition of latent inhibition by a single 5 mg dose of d-amphetamine in man.

The performance of healthy volunteer subjects on an auditory latent inhibition (LI) paradigm was assessed following administration of a single oral dose of d-amphetamine or placebo. It was predicted that a low (5 mg), but not a high (10 mg), dose of d-amphetamine would disrupt LI. The prediction was supported with left ear presentation of the preexposed stimulus only. When the preexposed stimulus was presented to the right ear the predicted pattern of findings was not obtained. It is concluded that the dopaminergic system is involved in the mediation of LI in man and it is speculated that the interaction between amphetamine dose and ear of presentation of the preexposed stimulus may reflect normally occurring dopaminergic hemisphere asymmetry.

Predicting severity of tricyclic antidepressant overdose.

The measurement of plasma concentration, a prolonged QRS interval, and level of consciousness have all been recommended as useful indicators of toxicity following tricyclic antidepressant overdose. The aims of this study were firstly, to determine the relative prognostic value of each of these indicators and secondly, to assess when a patient can be discharged safely from the intensive care unit. Data were evaluated on 67 patients with tricyclic antidepressant overdose from four centers. Plasma tricyclic antidepressant concentrations were measured, coma grade was evaluated using the Matthew-Lawson Coma Scale and a ECG was obtained from 23 patients on admission. Complications such as convulsions, hypotension, arrhythmias, and need for intubation and ventilation were recorded. Thirty patients developed complications and no patient died. Coma grade was the best predictor of outcome. The development of serious complications is unlikely in patients whose level of consciousness is grade II or less and who are admitted to hospital more than 6 h after overdose. Plasma tricyclic antidepressant concentration was of no additional value in predicting toxic complications or deciding when the patient could leave the intensive care unit. Our study suggests that an alert and orientated patient with a QRS duration less than 100 ms is the best indicator for safe transfer to a medical or psychiatric ward.

Comparative effects of the diastereoisomers, quinine and quinidine in producing phenocopy debrisoquine poor metabolisers (PMs) in healthy volunteers.

1. A single oral dose (50 mg) of quinidine significantly increased the debrisoquine metabolic ratio in six healthy volunteers. For four of the volunteers the metabolic ratio changed to that typical of the poor metaboliser (PM) phenotype. 2. The effect of quinidine in producing debrisoquine oxidation "poor metaboliser" phenocopies persisted for at least 3 days but had disappeared by 1 week. 3. The debrisoquine metabolic ratios for the same six subjects were not significantly altered by the oral administration of quinine (200 or 400 mg), the diastereoisomer of quinidine. 4. The plasma pharmacokinetic parameters of both nortriptyline and desipramine in healthy volunteers were all changed to those more typical of the debrisoquine PM phenotype following the concomitant administration of quinidine (50 mg). 5. It is concluded that quinidine, but not its diastereoisomer quinine, is a potent selective inhibitor of the in vivo oxidation of debrisoquine and can produce an artifactual PM phenocopy in persons who are phenotypically extensive metaboliser (EM) phenotype status. The clinical implications of this observation are discussed.

Rapid measurement of basic drugs in blood applied to clinical and forensic toxicology.

A gas chromatographic method is presented to measure blood, serum or plasma concentrations of more than 40 basic drugs. The sensitivity is 0.05 mg/L or less, which represents medium-high therapeutic and overdose concentrations, and in many instances the major active metabolites are also quantified. The paper describes a single step extraction from basic solution into n-butyl acetate containing maprotiline internal standard. Disposable glass tubes are used, with direct chromatography of the upper organic layer. GLC analysis is conducted for 10 min isothermally on a packed column (3% SP2250) with nitrogen-phosphorus detection. The coefficient of variation (CV) of the assay is between 2% and 5%, and data on the reproducibility of retention times are presented.

Gas chromatographic measurement of cocaine in serum, plasma and whole blood.

A gas chromatographic method is presented to measure cocaine in serum, plasma or blood. To reduce the in-vitro chemical and enzymic hydrolysis of cocaine, samples should be collected into fluoride oxalate tubes, frozen immediately and stored at -20 degrees C until analysis. Extractions are carried out in disposable glass tubes immersed in an ice-bath. The method uses a single step extraction from a mildly basic solution into n-butyl acetate containing maprotiline internal standard. A portion of the upper organic layer is chromatographed for 5 min isothermally on a packed column (3% SP2250) with nitrogen-phosphorus detection. The coefficient of variation (CV) of the assay is below 6% at 0.1 mg/L and the limit of accurate measurement is 0.02 mg/L. A case of acute cocaine intoxication is described to illustrate the application of the method.