Clarithromycin-induced ventricular tachycardia

Clarithromycin is a relatively new macrolide antibiotic that offers twice-daily dosing. It differs from erythromycin only in the methylation of the hydroxyl group at position 6. Although the side-effect profile of erythromycin is established, including gastroenteritis and interactions with other drugs subject to hepatic mixed-function oxidase metabolism, experience with the newer macrolides is still being recorded. Cardiotoxicity has been demonstrated after both intravenous and oral administration of erythromycin but has never been reported with the newer macrolides. We report a case of ventricular dysrhythmias that occurred after six therapeutic doses of clarithromycin. The dysrhythmias resolved after discontinuation of the drug.

Pretreatment prediction of the chemotherapeutic response of human glioma cell cultures using nuclear magnetic resonance spectroscopy and artificial neural networks

Both tumor metabolism and its response to cytotoxic drugs are intrinsic properties of tumor cells. It is therefore likely that there is a relationship between the two properties, however subtle and complex, wherein the metabolic characteristics of tumor cells can reflect the inherent response (resistance or sensitivity) of these cells to cytotoxic drugs. We used artificial neural network analysis to show that it is possible to distinguish, prior to treatment, between drug-resistant and drug-sensitive human glioma cell cultures from their metabolic profiles, as given by high-resolution proton nuclear magnetic resonance spectra of the cell extracts, and to predict their cellular response to the chemotherapeutic drug 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in vitro. The results suggest that neural network analysis of tumor nuclear magnetic resonance spectra has potential as a prognostic tool for determining treatment of gliomas, ultimately noninvasively, and may be used to provide information about the metabolic pathways involved in drug response that may be helpful in developing novel treatments for these tumors.

Acute bilineage leukemia after chronic myelogenous leukemia

Blastic transformation of chronic myelogenous leukemia may involve any hematopoietic lineage, including that of lymphocytes. In a minority of cases, the blasts express characteristics of both myeloid and lymphoid cells (biphenotypic) or comprise two separate populations of myeloid and lymphoid cells (bilineage leukemia). In a coordinated effort, we used a sequence of morphologic, cytochemical, immunocytochemical, and molecular biological studies to identify a case of bilineage blastic transformation of CML with a predominance of lymphoid blasts. The patient was treated for ALL and responded. The case presented illustrates the need for greater flexibility by the physician and laboratory to determine the specific diagnostic requirements for patients with hematologic malignancy with unusual phenotypic characteristics.

Ethylene glycol poisoning: case report of a record-high level and a review

Ethylene glycol is commonly found in automobile antifreeze and a variety of other commercial products. Ingestion of ethylene glycol, either accidentally or in a suicide attempt, is characterized by severe acidosis, calcium oxalate crystal formation and deposition, and a wide variety of end organ effects that may be fatal. We present a case of a patient who ingested a massive amount of ethylene glycol in a suicide attempt and yet survived with minimal sequelae. A comprehensive review of the literature on the pathology and pathophysiology of ethylene glycol toxicity on each organ system is provided, along with information on diagnosis and current treatment recommendations.

Postnatal development of membrane properties and delta oscillations in thalamocortical neurons of the cat dorsal lateral geniculate nucleus

The development of membrane properties, firing patterns, and delta oscillations in neurons of the cat dorsal lateral geniculate nucleus (dLGN) was investigated in vitro during the first 7 postnatal weeks. Compared with adult neurons, the resting membrane potential was more depolarized at postnatal days 1-9 (P1-P9), the input resistance was higher at P1-P7, and action potentials had a higher threshold and a smaller amplitude at P1-P3 and a longer duration at P1-P9. At P1-P3 trains longer than 200 msec were rarely observed, and trains with more than three action potentials were only present in 41% of the neurons, whereas at P1-P7 the normalized slope of the instantaneous frequencies at the first five interspike intervals was smaller than in the adult. A long-lasting (up to 6 sec) afterhyperpolarization followed a short train of action potentials in 88 and 30% of neurons at P1-P3 and P30-P32, respectively, but it was rarely observed in the adult. The low-threshold Ca2+ potential could evoke a burst of action potentials since P1. However, at P1-P7 the number of action potentials per burst was smaller (range, one to five), and at P1-P9 their maximum instantaneous frequency was lower (<190 Hz) than in the adult (range, six to eight, and 344 Hz, respectively). No delta oscillations were observed until P17, and their frequency (0.36 Hz) was lower than that in the adult (1.8 Hz). The percentage of neurons displaying delta oscillations and their frequency reached adult values by the end of the seventh postnatal week, i.e., well after the maturation of the membrane properties and firing patterns (second postnatal week). In conclusion, the maturation of the electrophysiological properties of thalamocortical neurons in the cat dLGN is completed later than the retinogeniculate axon segregation (Shatz CJ, 1983), and the immaturity of the oscillatory, and not of the burst-firing, activity is a limiting factor in the development of delta waves.

Successful treatment of crotalid-induced neurotoxicity with a new polyspecific crotalid Fab antivenom

STUDY OBJECTIVE

To report the effectiveness of a new polyvalent crotalid antivenom on neurotoxicity associated with North American rattlesnake envenomation. Two syndromes of crotalid-induced neurotoxicity have been reported. In severe envenomation by Crotalus scutulatus scutulatus (Mojave rattlesnake), weakness and fasciculations of various muscle groups, including those innervated by cranial nerves, may develop. Occasionally respiratory insufficiency develops. The second neurotoxic effects is myokymia, a type of fasciculation most frequently reported after bites by Crotalus horridus horridus (timber rattlesnake) and Crotalus atrox (Western diamondback rattlesnake). Conventional polyvalent antivenom is often ineffective in the treatment of venom-induced neurotoxicity.

METHODS

We report a case series of three patients envenomated by North American rattlesnakes, one of which was identified as C scutulatus scutulatus. All three patients experienced neurotoxicity with weakness, paresthesias, and dramatic fasciculations, along with other signs and symptoms of crotalid venom poisoning.

RESULTS

The administration of new polyspecific crotalid antivenom made of ovine Fab was successful in immediately and completely reversing neurotoxicity in each of these patients.

CONCLUSION

We report the use of a new antivenom for North American crotalid envenomation that seems to have efficacy in reversing neurotoxicity associated with these bites.

Association of rattlesnake bite location with severity of clinical manifestations

STUDY OBJECTIVE

To examine an association between bite location in cases of North American crotalid envenomation and the severity of clinical manifestations.

METHODS

We conducted a retrospective review of prospectively collected data for an experimental trial of crotalid antivenom. Our subjects were otherwise healthy individuals with minimal to moderate North American crotalid envenomation. We compared the severity of envenomation for patients with digit bites distal to the proximal interphalangeal joint and bites more proximal using a previously developed and validated snakebite severity score.

RESULTS

Thirteen subjects were classified as having distal bites and 24 as having proximal bites. At baseline (before antivenom administration), the distal group had a mean severity score of 2.9 +/- 1.1, whereas the proximal group had a mean severity score of 5.0 +/- 2.2 (P = .0024). Patients in the proximal group tended to demonstrate a more rapid initial decline in severity score after receiving antivenom than did the distal group.

CONCLUSION

In minimal to moderate North America crotalid envenomation, patients who sustained bites on distal aspects the digits tended to experience less severe clinical manifestations of envenomation. It is possible that an isolated bite to the distal aspect of a finger is an early marker of minimal envenomation.

Silent GABAA synapses during flurazepam withdrawal are region-specific in the hippocampal formation

Whole-cell patch-clamp recordings were made from CA1 pyramidal and dentate gyrus granule cells (GCs) in hippocampal slices to assess the effects of withdrawal from chronic flurazepam (FRZ) treatment on the function of synaptic GABAA receptors. In slices from control rats, acute perfusion of FRZ (30 microM) increased the monoexponential decay time constant of miniature IPSCs (mIPSCs) in CA1 and GCs (from 3.4 +/- 0.6 to 7.6 +/- 2.1 msec and from 4.2 +/- 0. 6 to 7.1 +/- 1.8 msec, respectively) but did not change their mean conductance, 10-90% rise time, or frequency of occurrence. Withdrawal (2-5 d) from chronic in vivo FRZ treatment (40-110 mg/kg per day, per os) resulted in a dramatic loss of mIPSCs in CA1 neurons. On day 5 of withdrawal, no mIPSCs could be recorded in 40% of CA1 pyramidal cells. In the remaining 60% of the neurons, mIPSCs had a reduced mean conductance (from 0.78 +/- 0.12 nS in vehicle-treated controls to 0.31 +/- 0.05 nS) and a diminished frequency of occurrence (from 20.7 +/- 7.9 to 4.1 +/- 0.6 Hz). We have estimated that >80% of GABAA synapses on CA1 pyramidal cells had become silent, whereas at still-active synapses the number of functional GABAA receptor channels decreased by 60%. This reduction rapidly reverted to control levels on day 6 of withdrawal. FRZ withdrawal did not alter mIPSC properties in GCs. Our results are consistent with the hypothesis that chronic benzodiazepine treatment leads to a reduced number of functional synaptic GABAA receptors in a region-specific manner that may stem from differences in the subunit composition of synaptic GABAA receptors.

Body habitus and coronary heart disease in men. A review with reference to methods of body habitus assessment

Table 1 is a synopsis of the major findings from an extensive literature on the association between human body habitus and coronary heart disease. Whilst some studies have used quite sophisticated laboratory procedures to quantify body fat most have relied upon anthropometric measurements to determine some component of body habitus. Of these, body weight and height are the simplest measurements and are, therefore, well-suited to large-scale prospective studies. Height and weight are highly reproducible measurements, although in the short term, weight can have considerable physiological variation associated with gastric emptying and state of hydration. Less reliable measurements than height and weight are skinfolds and body circumferences, both of which have been used extensively in cross-sectional and prospective analyses. For skinfolds, both the inter and intra-observer variability is affected by the measurement technique, location of the skinfold site, the skinfold caliper used and skinfold compressibility. As measurement error has been shown to be a function of skinfold thickness, accurate and repeatable skinfold measurements are particularly difficult to make in the obese. In these subjects, it is not always possible to locate a specific anatomical bony landmark or to pull a parallel skinfold away from the underlying tissue. Furthermore, in the extremely obese it is sometimes possible for a skinfold to be thicker than the jaws of the currently available commercial calipers. Alternately, body circumferences are obtainable in all subjects and have greater reproducibility than skinfolds. They are, therefore, the preferred method in obese subjects. However, there is considerable work to be done to establish their association with body fatness. The evidence examined in this review suggests that body weight is a poor predictor of coronary heart disease. Some studies have reported no difference in the body weight of coronary heart disease patients compared to subjects free of the disease, others found the body weight of subjects with coronary heart disease to be slightly greater, and one found the body weight of cardiac patients to be less than controls. Height, however, is associated with coronary heart disease in prospective studies with long-term and shorter-term follow-up periods and case-control designs. Fetal, infant and childhood under-nutrition may link shorter adult height and susceptibility to cardiovascular disease. Many researchers have studied the relationship between overweight and coronary heart disease by using a surrogate measurement of body fatness such as relative weight or a weight-for-height index. In general, results produced by these studies suggest weight-for-height indices, particularly the often used body mass index, are not strong predictors of coronary heart disease. Indeed case-control designs have consistently failed to show a relationship between body mass index and coronary heart disease. Inconsistent results from prospective studies, however, are difficult to interpret. To further confuse the situation, the body mass index has been examined in relation to different coronary heart disease end-points and adjusted for different confounding variables. Explaining the inconsistent results on the basis of length of follow-up is also not straightforward. When follow-up periods exceed 20 years, and sample size is small, however, this closer association has not been found, even with a long follow-up period. Whilst some studies have found no association after 15, 13 and 12 years others have reported a relationship after 8.5, 10, 12, 10 and 7 years. The 22 year follow-up evidence from the Framingham Study shows the strongest 'independent' association between body mass index and coronary heart disease. (ABSTRACT TRUNCATED)

Metabolic studies of human primitive neuroectodermal tumour cells by proton nuclear magnetic resonance spectroscopy

Well-characterized cell lines established from primitive neuroectodermal tumours (PNETs) were examined by proton nuclear magnetic resonance (1H-NMR) spectroscopy and chromatographic analysis of perchloric acid extracts, following amplification in cell culture. A characteristic 1H-NMR spectroscopic metabolite pattern was found for medulloblastoma cell lines, which clearly discriminates these cells from PNETs of other locations in the central nervous system (CNS), on the basis of their N-acetyl aspartate (NAA) and aspartate expression. Medulloblastoma cell lines were heterogeneous in respect of their metabolite expression, possibly owing to the heterogeneity in their differentiation along lineages of the CNS. All PNET spectra displayed similar features, including decreased NAA and creatine peaks and increased signals from choline compounds (Cho) compared with normal cerebellum. The expression of NAA by the medulloblastoma lines was in the opposite order to the extent of neuronal differentiation, which may indicate their origin from a progenitor cell with the phenotype of an oligodendrocyte-type-2 astrocyte cell.

Autoradiographic imaging of cerebral ischaemia using a combination of blood flow and hypoxic markers in an animal model

Current routine clinical techniques, including angiography and perfusional single-photon emission tomography, can be used to indicate problems in cerebral vascular supply and areas of cerebral hypoperfusion following a stroke, but cannot distinguish between ischaemic core and penumbra. In order to image specifically the penumbra, a method or indicator should be able to define areas with reduced blood flow, and a degree of metabolic compromise. In this context, the tissue could be regarded as hypoxic rather than ischaemic, and we have therefore chosen to investigate the potential of radio-labelled hypoxic markers in the study of ischaemia. In order to combine a hypoxic marker with a blood flow marker we used technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) and iodine-125 iodoazomycin arabinoside (125I-IAZA), during cerebral ischaemia in the rat middle cerebral artery occlusion model. 99mTc-HMPAO and 125I-IAZA were injected simultaneously 2 h following occlusion of the middle cerebral artery, and 5 h before decapitation. Paired autoradiograms were produced and compared. Three distinct patterns emerged from the autoradiograms: slightly decreased perfusion with no uptake of the hypoxic marker indicating an area of misery perfusion; moderately decreased perfusion with concomitant uptake of iodoazomycin arabinoside, a region of hypoxia; and severely decreased perfusion with no retention of the hypoxic tracer. In conclusion, we present a new use for an imaging agent in the investigation of cerebral hypoxia. This agent, IAZA together with HMPAO, provides a means of separating the penumbra into regions of misery perfusion and hypoxia. The potential impact of this may be important in the clinical investigation of stroke.

Refining the level for anticipated hepatotoxicity in acetaminophen poisoning

Treatment of an acetaminophen overdose with N-acetyl cysteine usually is based on the position of the 4-h acetaminophen (APAP) level on the Rumack-Matthew nomogram; however, there is disagreement on the level at which clinically relevant hepatotoxicity occurs. A retrospective review of all acute adult formulation APAP exposures reported to our poison center between 1986 and 1993 was performed and cases corresponding to the "possible risk or toxicity" range on the nomogram were identified. Our current poison center protocol for APAP poisoning does not recommend treatment with N-acetylcysteine (NAC) in low-risk patients if the 4-h serum APAP level or the extrapolated equivalent falls within the possible toxicity range on the nomogram. Seventeen cases met the inclusion criteria for the study and received no NAC; six additional patients met inclusion criteria but received one or two doses of NAC before therapy was discontinued. No patients in either group demonstrated clinical evidence of hepatotoxicity. This pilot study suggests that patients with no risk factors and APAP levels in the "possible risk" range may not require NAC therapy.

Immortalization and transformation are associated with specific alterations in choline metabolism

Analysis of transformed, immortalized, and primary rat Schwann cells by high-resolution proton nuclear magnetic resonance spectroscopy reveals that immortalization of Schwann cells (by SV40 large T antigen) induced a decrease in sn-glycero-3-phosphocholine (GPCho), whereas H-ras alone, which is known to cause growth arrest in these cells, induced a marked increase in GPCho and a decrease in phosphocholine (PCho). An increase of PCho was found only in cells fully transformed by both oncogenes together. Moreover, we examined 11 human tumor cell lines, all of which expressed a PCho:GPCho ratio similar to that of fully transformed rat Schwann cells. Importantly, neither the absolute levels of PCho nor the ratio of PCho:GPCho were correlated with the rate of cell division across a range of normal (primary cultures) and transformed cells. Thus, raised PCho:GPCho ratios may serve as an indicator of multiple oncogenic lesions and malignancy in noninvasive tumor investigations.

Regional and developmental variations in metabolite concentration in the rat brain and eye: a study using 1H NMR spectroscopy and high performance liquid chromatography

Regional and developmental changes in metabolite concentrations were measured by 1H NMR spectroscopy and HPLC of perchloric acid extracts from rat brain and eye. The highest concentrations of N-acetylaspartate were found in grey matter as opposed to white matter with concentration increasing with age from neonate to adult, while the related compound N-acetylaspartylglutamate was highest in adult optic nerve. Creatine and choline-containing compounds were present in all regions throughout development, with higher levels of creatine found in grey matter compared to other regions. Choline-containing compounds were present at the highest concentrations in the eye at all ages examined, and tended to decrease in concentration to minimum values in adulthood in all regions. The presence of hypotaurine in corpus callosum and optic nerve was consistent with the metabolic profiles of O-2A progenitor cells and oligodendrocytes, which are cells composing these tissues. The neurotransmitters glutamate and GABA reached their highest concentrations in the olfactory bulb (higher than in adult cortex).

A genome-wide search for human non-insulin-dependent (type 2) diabetes genes reveals a major susceptibility locus on chromosome 2

Non-insulin-dependent (type 2) diabetes mellitus (NIDDM) is a common disorder of middle-aged individuals characterized by high blood glucose levels which, if untreated, can cause serious medical complications and lead to early death. Genetic factors play an important role in determining susceptibility to this disorder. However, the number of genes involved, their chromosomal location and the magnitude of their effect on NIDDM susceptibility are unknown. We have screened the human genome for susceptibility genes for NIDDM using non-and quasi-parametric linkage analysis methods in a group of Mexican American affected sib pairs. One marker, D2S125, showed significant evidence of linkage to NIDDM and appears to be a major factor affecting the development of diabetes mellitus in Mexican Americans. We propose that this locus be designated NIDDM1.

Prehospital use of activated charcoal: a pilot study

Activated charcoal (AC) is most effective when administered soon after the ingestion of certain substances. Delays are recognized to occur at times in the administration of AC after arrival of poisoned patients in the emergency department (ED). In addition, it has been recognized that these delays may be avoided if AC administration is begun in selected patients by paramedics while en route to the ED. We present a pilot study evaluating the administration of AC to poisoned patients in the ambulance prior to arrival in the ED. We performed a retrospective review of Emergency Medical System (EMS) run sheets and ED records of poisoned patients during a 6-month period from two area hospitals. Cases were identified that met criteria for the prehospital administration of AC. Cases were divided into two groups: those who received prehospital AC, and those who did not. Groups were compared for ambulance transport time, time from first paramedic contact to AC administration, and whether AC was tolerated by the patient. A total of 14 patients received prehospital AC (group 1). This group was compared to 22 cases that would have qualified under County protocol to receive prehospital AC, but for whatever reason did not (group 2). Group 2 patients all received AC after arriving in the ED. Average ambulance transport times did not statistically differ among groups. The average time from first encounter with paramedics to administration of AC was 5.0 minutes when AC administration was given in the ambulance as compared to 51.4 minutes when delayed until arrival in the ED. Tolerance was similar among the groups. The time to initiate AC administration may be significantly shortened when begun by prehospital personnel. All EMS should consider including AC in protocols addressing the prehospital management of certain poisoned patients.

A model for quantification of perfusion in pulsed labelling techniques

A model for quantification of perfusion in pulsed labelling techniques is described, based on solving the modified Bloch equation including the effects of flow. The model is designed to fit experimental data acquired in two separate measurements (inversion and control, or selective and non-selective inversions) for different inversion times using a biexponential. Although the signal contrast is 50% less than the continuous labelling technique, it seems more appropriate for human studies because of its lower power deposition, shorter transit time and the use of an interleaved acquisition. The importance is shown of including in the model the difference in relaxation time between blood and tissue. Neglecting this difference can lead to an overestimation of flow, which can be as big as 100% in white matter and 20% in grey matter.

Proton nuclear magnetic resonance spectroscopy of lactate production in isolated rat liver during cold preservation

Lactate-edited 1H NMR difference spectra have been acquired from intact rat liver tissue following flushing and preservation in ice. A peak, initially at 1.26 ppm, was seen to increase in the liver tissue with preservation time. This peak was assigned to lactate, despite the fact that its chemical shift was initially shifted by approximately -0.1 ppm relative to an externally added standard. The assignment was based on the following: (a) the peak increased over a 24-h ischemic storage period; (b) it was coupled to a signal 2.78 +/- 0.02 ppm upfield; and (c) a parallel increase in lactate was noted in perchloric acid extracts of tissue from the same liver. An additional peak, assigned to alanine, was also observed during storage and was also shifted by approximately -0.1 ppm. Inclusion of dimethyl sulfoxide, which readily permeates liver tissue, demonstrated that this chemical shift alteration was a tissue-specific effect. These results demonstrate that 1H NMR spectroscopy of intact liver tissue during hypothermic ischemia is possible, though chemical shift assignments should be made with caution.

Proton nuclear magnetic resonance spectroscopy of primary cells derived from nervous tissue

Cell culture techniques, high-resolution in vitro 1H nuclear magnetic resonance (NMR) spectroscopy, and chromatographic analyses were used to compare the properties of purified cell populations derived from the PNS and cortical neurones. Cell cultures were immunocytochemically characterised with specific antibodies to ensure purity of the individual cultures. Spectra of perchoric acid extracts of cultured Schwann cells, perineural fibroblasts, dorsal root ganglion neurones, and cortical neurones displayed several common features. However, statistically significant differences were found by 1H NMR spectroscopy in most metabolites among the cell types studied. In addition, cells could be distinguished by the presence or absence of certain amino acids. For example, N-acetylaspartate was present in dorsal root ganglion neurones and cortical neurones, gamma-aminobutyric acid was present in large amounts in cortical neurones, and Schwann cell spectra displayed a large signal from glycine. These results extend our earlier findings that different cell types of the CNS exhibit highly characteristic metabolite profiles to now include the major cell types of the PNS. These latter cell types also exhibit characteristic metabolite compositions, such that even Schwann cells and oligodendrocyte type 2 astrocyte (O-2A) progenitor cells-precursors of the myelinating cells of the CNS and PNS, respectively-can be readily distinguished from each other.

Metabolic effects of cold storage on livers from euthermic and hibernating Columbian ground squirrels

The current study was undertaken to investigate energy metabolism during hypoxia in the cold in livers from euthermic and hibernating Columbian ground squirrels. We hypothesized that the hibernating Columbian ground squirrel would be able to maintain liver energetics for a considerably longer time than euthermic animals. Particular reference was made to the function of glycolysis, which is the only mechanism for energy production under hypothermic ischemia. The transition from aerobic to anaerobic metabolism was apparent in both euthermic and hibernating animals as lactate levels rose within 1-3 h; total lactate accumulation was 2.5 micromol/g in both groups. In euthermic squirrels, liver ATP and ADP decreased considerably over the first 3-h storage; values dropped by 55% and 34%, respectively. Conversely, as the drain on high energy phosphate pools progressed, there was an increase in low energy adenylate, AMP. Between 10 and 24 h of storage, increases in AMP accounted for approximately 25-30% of total ATP + ADP decrease. The remainder of the drop in adenylates was accounted for by considerable decreases in total adenylate (TA) contents; by 24 h TA contents had decreased by 2.0 micromol/g. Livers from hibernating squirrels exhibited similar patterns of adenylate change and were not significantly higher than their euthermic counterparts. With respect to regulatory control of glycolysis, livers from euthermic squirrels exhibited no regulatory control at phosphofructokinase (PFK) or pyruvate kinase (PK). Livers from hibernating animals, however, showed an activation at PFK by 10 h of cold storage; levels of hexose phosphates, glucose-6-phosphate + fructose 6-phosphate (G6P + F6P), dropped and fructose 1, 6-biphosphate (F1,6P2), increased. Changes in metabolite levels (phosphoenolpyruvate and pyruvate) associated with another key suspect regulatory enzyme, PK, indicated no role in regulatory control of glycolysis during the 24-h period. The apparent increase in PFK responsiveness to declining energy stores may be a futile activation since there was no accompanying increase in anaerobic end product, lactate, and no maintenance of energetics.

The use of ondansetron in the treatment of nausea and vomiting associated with acetaminophen poisoning

BACKGROUND

Nausea and vomiting associated with poisoning can complicate treatment and in some cases delay potential antidote administration. Side effect such as lowering the seizure threshold may at times discourage the use of traditional phenothiazine and butyrophenone antiemetics.

METHODS

We performed a prospective, single arm, observational study examining the effectiveness of the 5HT3 receptor antagonist ondansetron in the management if nausea and vomiting associated with acetaminophen poisoning. Patients with a history or laboratory evidence of acetaminophen poisoning were eligible for inclusion in the study. Exclusion criteria included age less than 18 or greater than 65, use of other antiemetic therapy within the previous 12 hours, history of preexisting hepatic or hematologic disease, pregnancy, or significant ingestion of other substances. Upon meeting entry criteria, patients were administered 8 mg of intravenous ondansetron. Nausea was graded on a 100 mm scale with number of emetic episodes recorded before and after treatment.

RESULTS

Six patients were entered in the study. All patients had nausea and at least one emetic episode prior to ondansetron and prior to administration of N-acetylcysteine. All patients reported relief of nausea after ondansetron. The degree of nausea decreased by an average of 52% at 30 min and 88% at 60 min following ondansetron administration. No significant vital sign changes were recorded in any patient, and there were no complications related to therapy. Three patients were administered N-acetylcysteine, and all tolerated this therapy without vomiting after ondansetron.

CONCLUSIONS

Ondansetron appears to be a potentially useful adjunct in the management of nausea and vomiting associated with acetaminophen poisoning.

Bioenergetic recovery following ischemia in brain slices studied by 31P-NMR spectroscopy: differential age effect of depolarization mediated by endogenous nitric oxide

Proximate neurotoxic mechanisms during postischemic recovery may be influenced by stage of development and complicating factors such as cortical spreading depression or secondary brain insult. Using 31P nuclear magnetic resonance spectroscopy, we have monitored pH and cellular energy metabolites phosphocreatine (PCr) and ATP in the ex vivo rat cerebral cortex before, during, and after substrate and oxygen deprivation, which represents "in vitro ischemia." There were important developmental differences in resistance and response to an ischemic insult. Twenty-one-day-old (P21) rat cortical slices had no detectable beta-ATP or PCr at the end of a 20-min insult, while 7-day-old (P7) slices had 50 +/- 13.7% (mean +/- SD, n = 12) and 17 +/- 14.8% relative to preischemia levels, respectively. Postischemic depolarization resulted in age-dependent effects on PCr (p < 0.05): In the older tissue, depolarization significantly worsened the recovery of PCr, whereas in young tissue it ameliorated recovery. This amelioration could be prevented by inhibiting nitric oxide production with methylene blue (depolarization-methylene blue interaction, p < 0.05) and enhanced by administration of the nitric oxide donor glyceryl trinitrate (GTN; p < 0.01). However, in P21 tissue, GTN further exacerbated injury (age-GTN interaction, p < 0.01). Therefore, in this vascular-independent preparation, a neuronal or glial nitric oxide-dependent mechanism appears to confer improved postischemic bioenergetic recovery in the developing brain compared with the mature brain.

Hypermagnesemia following an acute ingestion of Epsom salt in a patient with normal renal function

CASE REPORT

Hypermagnesemia is a rare condition that commonly follows excessive therapeutic administration of magnesium sulfate to treat eclampsia of pregnancy. Signs and symptoms of this condition include extreme muscle weakness, loss of deep tendon reflexes, mental status depression, and cardiac dysrhythmias. Clinically significant hypermagnesemia following oral or rectal administration of magnesium containing products in patients with normal renal function is rare. We report a case of hypermagnesemia following massive Epsom salt ingestion that resulted in extreme musculoskeletal weakness and altered mentation.