A computerized scoring system to improve assessment of heparin-induced thrombocytopenia risk

Essentials Current risk scores for heparin-induced thrombocytopenia (HIT) are not computer-friendly. We compared a new computerized risk score with the 4Ts score in a large healthcare system. The computerized risk score agrees with the 4Ts score 85% of the time. The new score could potentially improve HIT diagnosis via incorporation into decision support. SUMMARY: Background (HIT) is an immune-mediated adverse drug event associated with life-threatening thrombotic complications. The 4Ts score is widely used to estimate the risk for HIT and guide diagnostic testing, but it is not easily amenable to computerized clinical decision support (CDS) implementation. Objectives Our main objective was to develop an HIT computerized risk (HIT-CR) scoring system that provides platelet count surveillance for timing and degree of thrombocytopenia to identify those for whom diagnostic testing should be considered. Our secondary objective was to evaluate clinical management and subsequent outcomes in those identified as being at risk for HIT. Methods We retrospectively analyzed data from a stratified sample of 150 inpatients treated with heparin to compare the performance of the HIT-CR scoring system with that of a clinically calculated 4Ts score. We took a 4Ts score of ≥ 4 as the gold standard to determine whether HIT diagnostic testing should be performed. Results The best cutoff point of the HIT-CR score was a score of 3, which yielded 85% raw agreement with the 4Ts score and a kappa of 0.69 (95% confidence interval 0.57-0.81). Ninety per cent of patients with 4Ts score of ≥ 4 failed to undergo conventionally recommended diagnostic testing; 38% of these experienced persistent, unexplained thrombocytopenia, and 4% suffered life-threatening thrombotic complications suggestive of undiagnosed HIT. Conclusion The HIT-CR scoring system is practical for computerized CDS, agrees well with the 4Ts score, and should be prospectively evaluated for its ability to identify patients who should be tested for HIT.

Clinical effectiveness of a Bayesian algorithm for the diagnosis and management of heparin-induced thrombocytopenia

Essentials We previously published a diagnostic algorithm for heparin-induced thrombocytopenia (HIT). In this study, we validated the algorithm in an independent large healthcare system. The accuracy was 98%, sensitivity 82% and specificity 99%. The algorithm has potential to improve accuracy and efficiency in the diagnosis of HIT.

SUMMARY

Background Heparin-induced thrombocytopenia (HIT) is a life-threatening drug reaction caused by antiplatelet factor 4/heparin (anti-PF4/H) antibodies. Commercial tests to detect these antibodies have suboptimal operating characteristics. We previously developed a diagnostic algorithm for HIT that incorporated 'four Ts' (4Ts) scoring and a stratified interpretation of an anti-PF4/H enzyme-linked immunosorbent assay (ELISA) and yielded a discriminant accuracy of 0.97 (95% confidence interval [CI], 0.93-1.00). Objectives The purpose of this study was to validate the algorithm in an independent patient population and quantitate effects that algorithm adherence could have on clinical care. Methods A retrospective cohort comprised patients who had undergone anti-PF4/H ELISA and serotonin release assay (SRA) testing in our healthcare system from 2010 to 2014. We determined the algorithm recommendation for each patient, compared recommendations with the clinical care received, and enumerated consequences of discrepancies. Operating characteristics were calculated for algorithm recommendations using SRA as the reference standard. Results Analysis was performed on 181 patients, 10 of whom were ruled in for HIT. The algorithm accurately stratified 98% of patients (95% CI, 95-99%), ruling out HIT in 158, ruling in HIT in 10 and recommending an SRA in 13 patients. Algorithm adherence would have obviated 165 SRAs and prevented 30 courses of unnecessary antithrombotic therapy for HIT. Diagnostic sensitivity was 0.82 (95% CI, 0.48-0.98), specificity 0.99 (95% CI, 0.97-1.00), PPV 0.90 (95% CI, 0.56-0.99) and NPV 0.99 (95% CI, 0.96-1.00). Conclusions An algorithm incorporating 4Ts scoring and a stratified interpretation of the anti-PF4/H ELISA has good operating characteristics and the potential to improve management of suspected HIT patients.

Effect of Glycol Ethers on Plasma Osmolality

1 Glycol ethers and their alkoxyacetic acid metabolites produce a linear increase in plasma osmolality with increasing plasma concentration.

2 This change in osmolality may be too small to be clinically useful at concentrations expected in cases of acute human glycol ether poisoning.

Outcomes following abuse of methanol-containing carburetor cleaners

INTRODUCTION

Carbureter cleaners may contain methanol and are abused via inhalation. Toxicity resulting from the methanol component of these products is poorly described.

METHODS

We conducted a retrospective poison center chart review over a four-year period (3/98-3/02) of outcomes following methanol-containing carbureter cleaners (MCC) exposure. Inclusion criteria were: (1) use of MCC, (2) evaluation in health care facility (HCF), (3) no known co-ingestion exposure and (4) at least 12 hour follow-up.

RESULTS

33 cases were reviewed with 11 cases excluded because of significant co-ingestions. Of the remaining 22 cases the mean age was 17 [range: 14-41] years old with 90% of cases between 14 and 17 years old. Six women and 16 men were in the study. Six of 22 cases had acidosis (serum bicarbonate < or =22 mmol/L or pH < or =7.35), 100% of patients had neurological symptoms (ataxia, etc.) and 14/22 had vomiting on presentation. Three patients received treatment with ethanol (1) and fomepizole (2). All others received intravenous fluids (15) or no treatment (4). Mean serum methanol concentration was 28mg/dl [range: 0-341 with 17/22 developing acidosis. Serum methanol was obtained at a mean of 3.5 hours [range 1-7 hours] post use. All metabolic disturbances resolved within 24 hours except in one patient (41 years old) in which her disturbances resolved within 72 hours. No patient developed visual disturbances or neurological sequealae.

CONCLUSIONS

Significant toxicity following inhalation of MCC was rare with symptoms improving without aggressive care (dialysis, alcohol dehydrogenase blockade).

A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment for crotaline snakebite in the United States

BACKGROUND

Current therapy for crotaline snakebite includes antivenin (Crotalidae) polyvalent, an antivenom with numerous adverse effects. We compared the efficacy and safety of 2 dosing regimens with a new antivenom, Crotalinae polyvalent immune Fab (Fab AV).

METHODS

A single dose of Fab AV alone (as-needed [PRN] group) was compared with an initial dose plus repeated treatments during 18 hours (scheduled group) in a multicenter randomized trial. The study included patients with minimal or moderate envenomation by a crotaline snake within the preceding 6 hours, aged 10 years or older, in whom worsening of the envenomation syndrome was observed before Fab AV treatment. After treatment with Fab AV to achieve initial control, patients were randomized to the scheduled or PRN treatment group. Scheduled group patients received additional doses of Fab AV every 6 hours for 3 doses. The PRN group received no planned additional doses of antivenom.

RESULTS

The mean severity score of the 31 patients decreased from 4.35 to 2.39 points (P<.001); there was no difference between scheduled and PRN groups. No patient in the scheduled group received unplanned Fab AV doses, but 8 of 16 patients in the PRN group received unplanned doses (P =.002). Acute reactions occurred in 6 patients (19%), and serum sickness occurred in 6 (23%) of 26 patients who returned for follow-up.

CONCLUSIONS

In the first randomized trial of antivenom in the United States, Fab AV effectively terminated venom effects. Since the unplanned use of Fab AV in the PRN group was common, the treatment regimen may require more than 1 initial dose.

Intravenous pyridoxine-induced metabolic acidosis

STUDY OBJECTIVE

Pyridoxine hydrochloride, the antidote for isonicotinic acid hydrazide (INH)--induced seizures, is available in solution at a concentration of 100 mg/mL at a pH of less than 3. Pyridoxine is often infused rapidly in large doses for INH-induced seizures. Effects of pyridoxine infusion on base deficit in amounts given for INH poisoning have not been studied in human subjects. We hypothesized that this infusion would result in transient worsening of acidosis.

METHODS

We conducted a randomized, controlled crossover trial in human volunteers. Five healthy volunteers (mean age, 35 years; range, 29 to 43 years) were randomized to receive intravenous placebo (50 mL of normal saline solution) or 5 g of pyridoxine (50 mL) over 5 minutes. A peripheral intravenous catheter was established in each arm, and a heparinized venous blood sample was obtained for base deficit at baseline and 3, 6, 10, 20, and 30 minutes after infusion. After at least a 1-week washout period, the volunteers were assigned to the alternate arms of the experiments, thus acting as their own control subjects. Data were analyzed by using the 2-tailed paired t test, controlling for multiple comparisons.

RESULTS

No difference was noted between groups at baseline. A statistically significant increased base deficit was noted after the pyridoxine infusion versus control at 3 to 20 minutes but not at 30 minutes (P =.1). Maximal mean increase in base deficit (2.74 mEq/L) was noted at 3 minutes.

CONCLUSION

A transient increase in base deficit occurs after the infusion of 5 g of pyridoxine in normal volunteers.

Diagnostic use of physicians' detection of urine fluorescence in a simulated ingestion of sodium fluorescein-containing antifreeze

STUDY OBJECTIVE

We sought to assess physicians' ability to accurately determine the presence or absence of sodium fluorescein (SF) in urine at a concentration corresponding to that present after ingestion of a toxic amount of commercial automotive antifreeze.

METHODS

We studied 2 different urine specimen evaluation formats--one presenting isolated specimens, and the other presenting specimens grouped for comparison--to determine whether the visual clues afforded by grouped comparison aided the accuracy of the evaluation. On each study day, 3 urine specimens (1 control specimen obtained before SF administration and 2 specimens obtained after SF administration) were obtained from each of 9 or 10 volunteers. Each of these 27 or 30 urine specimens were presented sequentially and in random order to 2 emergency physicians during separate evaluation time periods. Each physician was asked to classify each specimen as fluorescent or nonfluorescent (sequential format). After a rest period, each physician, again separately, was asked to look at the same 27 or 30 urine specimens, this time all together in a test tube rack so that grouped comparisons were possible. The physicians again classified each sample as either fluorescent or nonfluorescent (grouped format). We assessed sensitivity, specificity, and accuracy of the evaluation by each presentation format (sequential or grouped).

RESULTS

Mean examiner sensitivity, specificity, and accuracy for detecting the presence of SF in urine using the sequential presentation format were 35%, 75%, and 48%, respectively, whereas the same test performance indices were 42%, 66%, and 50%, respectively, when the grouped format was used.

CONCLUSION

Wood's lamp determination of urine fluorescence is of limited diagnostic utility in the detection of SF ingestion in an amount equivalent to toxic ingestion of some ethylene glycol--containing automotive antifreeze products.

Crack cocaine ingestion with prolonged toxicity requiring electrical pacing

CASE REPORT

We report a 38-year-old man who experienced prolonged toxicity lasting over 16 hours from the time of ingestion of 1/4 ounce of crack cocaine. His illness included status epilepticus, wide and narrow complex bradyarrhythmias, ventricular arrhythmias, and delayed hyperthermia. His bradyarrhythmias were refractory to medicinal intervention and responsive to application of an external pacemaker. The patient recovered to his baseline state over the ensuing 48 hours.

Rattlesnake envenomations: unusual case presentations

Rattlesnake envenomations are common in some areas of the United States. Although fatal rattlesnake envenomations are rare and usually preventable, morbidity may be significant. Patients may present with localized edema, hypotension, coagulopathy, or thrombocytopenia. Patients with progressive swelling or severe coagulopathy are typically treated with Crotalidae polyvalent antivenin. We present a series of 4 patients with unusual complications of rattlesnake envenomation to illustrate the wide spectrum of disease that may be encountered. These case presentations include anaphylaxis to rattlesnake venom, an acute airway emergency, progressive and marked edema with a large pleural fluid collection, and death.

Combined ingestion and subcutaneous injection of elemental mercury

A 40-year-old man with a history of schizophrenia and inflammatory soft tissue lesions after self-injection of elemental mercury presented to the Emergency Department. Multiple skin abscesses associated with fever required operative debridement. An incidental finding of oral mercury ingestion was followed clinically and did not result in complications. Exposure to elemental mercury through injection or ingestion is an uncommon event, but one the Emergency Physician may encounter. Subcutaneous mercury injection should be managed with local wound debridement, whereas ingestions are rarely of clinical significance.

Hypertonic sodium bicarbonate is effective in the acute management of verapamil toxicity in a swine model

STUDY OBJECTIVE

This study was conducted to determine whether hypertonic sodium bicarbonate would improve the hypotension associated with severe verapamil toxicity compared with volume expansion.

METHODS

The study design used a nonblinded acute animal preparation. Twenty-four anesthetized and instrumented swine were poisoned with verapamil delivered at a rate of 1 mg/kg per hour for 10 minutes followed by incremental increases of 1 mg/kg per hour every 10 minutes until the endpoint of a mean arterial blood pressure of 45% of baseline was achieved. Animals alternately received either 4 mEq/kg of hypertonic sodium bicarbonate intravenously over 4 minutes or similar volumes of 0.6% sodium chloride in 10% mannitol (control). The main outcome parameter followed was mean arterial pressure. In addition, physiologic parameters including cardiac output, heart rate, pH, PCO (2), PO (2), plasma ionized calcium, sodium, and potassium were monitored.

RESULTS

Verapamil toxicity, as defined by a mean arterial pressure of 45% of baseline, was produced in all animals following an average verapamil infusion dose of 0.6+/-0.12 mg/kg. This dose produced an average plasma verapamil concentration of 728.1+/-155.4 microgram/L, with no significant difference between groups. Swine treated with hypertonic sodium bicarbonate experienced a significant increase in mean arterial pressure (>50%) and cardiac output (>30%) over the first 20 minutes that slowly equilibrated with the control group over the remainder of the experiment. As expected, plasma sodium concentrations were elevated significantly in the sodium bicarbonate group while plasma potassium concentrations were decreased significantly. Finally, there was a significant decrease in plasma ionized calcium concentration in the sodium bicarbonate-treated group compared with controls.

CONCLUSION

Hypertonic sodium bicarbonate reversed the hypotension and cardiac output depression of severe verapamil toxicity in a swine model.

Failure of intravenous N-acetylcysteine to reduce methemoglobin produced by sodium nitrite in human volunteers: A randomized controlled trial

STUDY OBJECTIVE

To determine whether intravenous N -acetylcysteine (NAC) produces a clinically significant decline in sodium nitrite-induced methemoglobinemia in human volunteers.

METHODS

We conducted a randomized, control crossover trial with each subject serving as his own control. Methemoglobinemia was induced with intravenous sodium nitrite (4 mg/kg) administered over 10 minutes starting at time 0. At time 30 minutes, subjects were randomly assigned to treatment with intravenous NAC for 100 minutes (150 mg/kg over 1 hour followed by 14 mg/kg per hour for 40 minutes) or administration of an equal volume of 5% dextrose in water. Each subject received the alternative treatment after an interval of at least 1 week. Blood methemoglobin concentrations were measured by multiwavelength co-oximetry at time 0, 15, 30, 50, 70, 90, 110, and 130 minutes. Area under the methemoglobin concentration-time curve (AUC) between 30 and 130 minutes was compared between groups using a 2-tailed, paired t test.

RESULTS

There were no statistically significant differences in the control and treatment groups with respect to baseline hemoglobin or methemoglobin concentrations, as well as nitrite-induced methemoglobin concentrations at the initiation of treatment (0.85+/-0.06 g/dL, 0.88+/-0.04 g/dL; mean+/-SEM; P =.31). Mean AUC for the control group (77.1+/-5.7 g x min/dL) was significantly lower than the mean AUC for the treatment group (84.5+/-4.7 g x min/dL); P =.01).

CONCLUSION

Intravenous NAC failed to enhance methemoglobin reduction in this model.

The lack of transplacental movement of the cyanide antidote thiosulfate in gravid ewes

A previous study reported that the co-infusion of IV sodium thiosulfate (STS) with sodium nitroprusside (SNP) to near-term gravid ewes prevented both maternal and fetal cyanide toxicity. We questioned whether maternally administered STS crossed the ovine placenta to enhance fetal transulfuration of cyanide, or whether the fetus was dependent on maternal detoxification of cyanide after diffusion of cyanide into the maternal circulation. Ten anesthetized, near-term gravid ewes underwent hysterotomies with delivery of fetal heads for venous catheterization. Five control ewes received IV isotonic sodium chloride solution, whereas five experimental ewes received IV STS (50 mg/kg over 15 min). Serial plasma thiosulfate concentrations in ewes and fetuses were measured over 135 min. Areas under the time-plasma thiosulfate concentration curves were calculated for experimental and control ewes at 2758+/-197 and 508+/-74 min x mg(-1) x L(-1), respectively (P < 0.008). Mean areas under the curve for experimental and control fetuses were 236+/-34 and 265+/-23 min x mg(-1) x L(-1), respectively (P > 0.5). Maternally administered STS may prevent fetal cyanide poisoning from SNP administration without relying on STS crossing the placenta into the fetal circulation. Fetal cyanide may cross down a concentration gradient from fetal to maternal circulation, to be transulfurated to thiocyanate in maternal tissues.

IMPLICATIONS

We evaluated the mechanism of action of sodium thiosulfide (STS) in sodium nitroprusside-induced cyanide toxicity in the ewe. Fetal cyanide poisoning is alleviated by maternal administration of STS, although this cyanide antidote apparently does not cross the placenta.

Incidence of immediate and delayed hypersensitivity to Centruroides antivenom

STUDY OBJECTIVE

To assess the incidence and course of immediate and delayed hypersensitivity to Centruroides antivenom.

METHODS

We performed a 12-month prospective observation study, with telephone follow-up, evaluating the incidence of anaphylaxis or anaphylactoid reactions and serum sickness after Centruroides antivenom administration. The setting for the study was a poison control center and tertiary care toxicology treatment center. Participants included all patients who received Centruroides antivenom, and no interventions were performed.

RESULTS

For immediate hypersensitivity reactions, 116 patients with grade III or IV envenomation received Centruroides antivenom; 77 of these patients were younger than 13 years. Three patients completed the infusion despite development of rash. A fourth patient with a history of atopy and asthma received epinephrine infusion and an inhaled beta-agonist for transient wheezing that quickly resolved; she was admitted for observation. Nine patients without hypersensitivity reactions were admitted for social reasons, for inappropriate sedation from drugs used before antivenom, or to rule out aspiration; all were discharged within 24 hours. The remaining 106 patients were discharged from the emergency department after resolution of symptoms. Thus 4 of 116 patients had immediate reactions. For patients with delayed reactions, 17 patients were lost to follow-up. Of 99 remaining patients, serum sickness developed in 61% (n=60), as defined by using liberal criteria. Serum sickness responded to oral steroids, antihistamines, or both; mean duration of symptoms with medication was 2.8 days.

CONCLUSION

Anaphylactic reactions are uncommon after Centruroides antivenom infusion. Self-limited serum sickness that is easily controlled with corticosteroids and antihistamines commonly follows the use of Centruroides antivenom.

Renal failure and corrosive airway and gastrointestinal injury after ingestion of diluted diquat solution

A 66-year-old man ingested 200 mL of Dexol Industries Weed and Grass Killer Concentrate (Torrance, CA), which contains 1.84% diquat dibromide, a herbicide structurally similar to paraquat. He remained asymptomatic for 8 hours, and then a sore throat and vomiting developed. Twenty hours after ingestion, esophagitis, mucositis, epiglottitis, and acute renal failure developed, from which he slowly recovered. This is the first report of systemic diquat toxicity from ingestion of a diluted diquat solution.

Effect of magnesium hydroxide on iron absorption following simulated mild iron overdose in human subjects

OBJECTIVE

To determine the effect of oral magnesium hydroxide [Mg(OH)2] on iron absorption after simulated iron overdose in human subjects.

METHODS

A randomized, controlled crossover study was conducted in healthy adult male human volunteers taking no medications. Subjects received an average of 5.0 mg/kg elemental iron orally followed 1 hour later by either oral administration of 4.5 g of Mg(OH)2 per g ingested elemental iron or no treatment. Serial serum specimens were obtained over the 12 hours following iron ingestion and stored at -60 degrees C until standard serum iron assay was performed. After a 2-week washout period, the subjects were enrolled in the alternative trial arm. Individual baseline diurnal variation in serum iron levels was determined over a 12-hour period on the day prior to each trial. Area under time-concentration curves (AUCs) were calculated, and the AUC due to experimental iron ingestion (deltaAUC) was determined by subtracting the baseline diurnal AUC from the experimental AUC for each subject.

RESULTS

Thirteen healthy adult male subjects were enrolled. Mean +/- SEM for deltaAUC due to experimental iron ingestion followed by treatment with Mg(OH)2, 78 +/- 23 micromol(hr)/L, was significantly less than that followed by no treatment, 144 +/- 33 micromol(hr)/L (p = 0.03 by signed rank test).

CONCLUSIONS

Magnesium hydroxide, administered 1 hour post-iron ingestion at an oral dose of 4.5 g per g elemental iron ingested, significantly reduced iron absorption during a 12-hour period following simulated mild iron overdose in healthy adult human volunteers.

Dexfenfluramine overdose

Dexfenfluramine (Redux), the dextro-rotatory (+) steroisomer of fenfluramine, was previously approved for the treatment of weight control in the United States. We report a case of acute dexfenfluramine ingestion characterized by coma, clonus, and respiratory failure.

Crotalid snake envenomation

Over 5000 Americans suffer from snake bites annually, and of these, nearly one quarter are from poisonous species. Although these cases are undeniably reported, death appears to occur in only a few cases each year, and often reflects delay in obtaining medical care. Two families of venomous snake indigenous to the United States account for most envenomations: Crotalidae (pit vipers or new world vipers) and Elapidae. This article focuses on the snakes of the Crotalidae family.

Poisoning by sodium channel blocking agents

Poisoning by drugs that block voltage-gated sodium channels produces intraventricular conduction defects, myocardial depression, bradycardia, and ventricular arrhythmias. Human and animal reports suggest that hypertonic sodium bicarbonate may be effective therapy for numerous agents possessing sodium channel blocking properties, including cocaine, quinidine, procainamide, flecainide, mexiletine, bupivacaine, and others.

Affinity-purified, mixed monospecific crotalid antivenom ovine Fab for the treatment of crotalid venom poisoning

SUBJECT OBJECTIVE

To test the efficacy and safety of a new antivenom, affinity-purified, mixed monospecific crotalid antivenom ovine Fab, in human subjects with minimal or moderate crotalid envenomation.

METHODS

We conducted a prospective multicenter clinical trial of 11 patients 10 years or older with progressive manifestations after mild to moderate crotalid snakebite. After giving their consent, subjects received four to eight vials of study drug and were then repeatedly examined over 48 hours and at 7 and 14 days after discharge. Each patient's clinical condition was evaluated serially with the use of a validated severity score, as well as on the basis of the investigator's assessment.

RESULTS

In all 11 subjects to the antivenom was judged by the investigator to have had a beneficial response. The severity score for each patient remained the same or decreased over the first 4 hours. However, two subjects demonstrated worsened condition 12 to 15 hours after antivenom administration. In no subject did an allergic reaction develop.

CONCLUSION

In this patient group, affinity-purified, mixed monospecific crotalid antivenom ovine Fab was associated with a halt of progressive crotalid venom poisoning. Initial safety data are promising but must be addressed further in subsequent studies.

Prevention of fetal and maternal cyanide toxicity from nitroprusside with coinfusion of sodium thiosulfate in gravid ewes

Coadministration of sodium thiosulfate with sodium nitroprusside (SNP) to children and adults prevents increases in cyanide concentrations during anesthesia or long-term SNP infusions. We wondered whether maternally administered sodium thiosulfate would prevent increases in fetal red cell cyanide concentrations in gravid ewes receiving SNP infusions. Under anesthesia, the fetal head was delivered through a lateral hysterotomy for catheterization of the jugular vein; the fetus was left in utero. Six control ewes near term received SNP at 25 micrograms.kg-1.min-1 for 4 h. Norepinephrine was used to maintain maternal mean arterial pressure at 80% baseline values. Six experimental ewes received the same treatment except that sodium thiosulfate was infused with SNP (1 g sodium thiosulfate per 100 mg SNP). Serial red cell cyanide concentrations in ewes and fetuses were followed. One control fetal death resulted from abruptio placenta, and this ewe and fetus were excluded from analysis. An additional control ewe and fetus died from apparent cyanide poisoning late during the course of the experiment. While control ewes and fetuses suffered progressive increases in red cell cyanide concentrations into the toxic range, experimental ewes and fetuses never developed toxic red cell cyanide levels (ewes P < .003, fetuses P < .004). These data, if applicable to humans, suggest that coadministration of sodium thiosulfate with SNP to pregnant women at doses currently in use for nonpregnant patients will prevent fetal, as well as maternal, cyanide toxicity.

Pool cue chalk: a source of environmental lead

Lead compounds are used as coloring agents for numerous products. Two cases of children with elevated blood lead concentrations encountered by the authors suggested that pool cue chalk may serve as a source of environmental lead. The objective of this study was to determine lead content of various brands and colors of pool cue chalk. Atomic absorption analyses were conducted of 23 different types of pool cue chalk for lead content. Three of 23 types of pool cue chalk contained more than 7000 ppm (mg/kg) lead: one manufacturer's green and tangerine chalk and another manufacturer's green chalk. It was concluded that some brands of pool cue chalk contain relatively large amounts of lead and could contribute to childhood lead poisoning.

The effect of hypertonic sodium bicarbonate on QRS duration in rats poisoned with chloroquine

OBJECTIVE

To determine efficacy of hypertonic sodium bicarbonate in narrowing QRS prolongation produced by chloroquine.

DESIGN

Randomized, controlled animal experiment using an accepted rat model of sodium channel blockade.

METHODS

Hypotension and widening of QRS complexes (lead II) of the ECG were produced in 16 rats by administration of a total of 87 mg/kg chloroquine intravenously over 20 minutes. Eight rats were treated with 6 mL/kg 1 M sodium bicarbonate intravenously over two minutes beginning ten minutes into the chloroquine infusion. Serial measurements of QRS duration and systolic blood pressure were obtained for 30 minutes.

RESULTS

QRS intervals narrowed more rapidly in animals receiving sodium bicarbonate (p = .045), although the difference in mean rate of narrowing between groups was modest at only .23 msec/min. Because of large variances, no statistically significant differences could be demonstrated in systolic blood pressure.

CONCLUSIONS

Hypertonic sodium bicarbonate partially reversed sodium channel blockade and resultant QRS interval prolongation produced by chloroquine in rats. These data should be interpreted with caution, given the need to extrapolate to humans and the modest effect of sodium bicarbonate on QRS narrowing.

Seizure after isolated fluoxetine overdose

Previous case reports of seizures following fluoxetine overdose have not adequately ruled out ingestion of other substances and have lacked documentation of increased serum drug levels. We present a case of seizure following fluoxetine overdose in a previously well patient with a clear history of sole ingestion. We ruled out the presence of other substances with comprehensive drug screening and documented increased serum levels of fluoxetine and its active metabolite.

Effect of the cyanide antidote hydroxocobalamin on commonly ordered serum chemistry studies

STUDY HYPOTHESIS

Concentrated aqueous solutions of hydroxocobalamin (OHCob) are given intravenously for the treatment of cyanide poisoning. Because OHCob solutions are intensely red and have peak light absorptions at 352 nm and 525 nm, we investigated whether the presence of OHCob in serum would interfere with various automated, colorimetric chemistry measurements.

DESIGN

Selected serum chemistry colorimetric measurements were compared in seven patients, using their own serum as control, with serum containing OHCob at the following concentrations: 100 mg/L, 500 mg/L, and 1,000 mg/L. These concentrations are in the range achieved with therapeutic doses of OHCob when given for cyanide poisoning.

MEASUREMENTS AND MAIN RESULTS

Statistically significant alterations in serum values for aspartate aminotransferase, total bilirubin, creatinine, magnesium, and iron were seen in the presence of OHCob.

CONCLUSION

The presence of OHCob in serum interferes with several chemistry methodologies, and such interference should be anticipated when this antidote is used.

Clinical toxicology of ethylene glycol monoalkyl ethers

The glycol ethers constitute a family of organic solvents commonly found in industrial and household products. Because of their widespread availability and potential for serious toxicity, physicians should be aware of the clinical toxicology of these compounds. Until recently, knowledge of the toxic effects of glycol ethers has been derived from animal studies and a limited number of case reports and small case series. A growing body of data from epidemiological studies, controlled human studies, and studies using human tissue now allows for advancement in the understanding of the acute and chronic toxicity of these compounds. This review summarizes and evaluates human and pertinent animal literature on the clinical toxicology of glycol ethers, with a focus on the commonly encountered monoalkyl ethers of ethylene glycol. Management options for acute poisoning, as well as measures for the control of workplace exposures, are discussed.

Acute iron poisoning

Acute iron poisoning continues to be one of the most common and deadly poisonings seen by emergency physicians. There are many potential pitfalls in the assessment, diagnosis, and treatment of iron-poisoned patients. This article reviews the pathophysiology of acute iron poisoning and describes a comprehensive management plan that will enable emergency physicians to provide appropriate emergency care to patients ingesting iron preparations. This article also addresses the common problems encountered by clinicians who care for iron-poisoned patients once they are admitted to the hospital.

Transplacental transport of N-acetylcysteine in an ovine model

STUDY OBJECTIVE

Acetaminophen freely crosses the placenta, and acetaminophen ingestion is the most frequent intentional overdose in pregnancy. Although most patients do well after maternal treatment with the antidote N-acetylcysteine (NAC), fetal death with massive hepatic necrosis has occurred. It has never been shown whether NAC crosses the placenta to yield fetal plasma levels equal to those associated with hepatoprotective effects in human beings. Our study objective was to evaluate this in a widely accepted large animal model for maternal-fetal research. DESIGN AND TYPE OF PARTICIPANTS: A nonblinded experiment was performed using four domestic sheep at near-term gestation.

INTERVENTIONS

NAC 150 mg/kg IV was administered to the ewe over 15 minutes. After induction of anesthesia, the fetal head was delivered surgically and a neck vein cannulated for blood sampling. Maternal and fetal blood samples were obtained at the end of NAC infusion, at 30- and then at 60-minute intervals for four hours. Plasma NAC levels were determined by gas chromatography/mass spectroscopy (detection limit, 2 micrograms/mL; quantification limit, 5 micrograms/mL).

RESULTS

Maternal peak plasma NAC levels were 619, 631, 1,757, and 2,512, micrograms/mL, respectively, within 30 minutes of infusion. However, NAC was only minimally detectable in plasma of two fetal animals and transiently reached quantifiable levels in two others. None of the fetal animals attained serial plasma NAC levels that equalled those associated with therapeutic dosing or hepatoprotective effects in human beings.

CONCLUSION

Transplacental transport of NAC is clinically insignificant in a mammalian model resembling the human being. These findings suggest that the human fetal liver is not protected from acetaminophen toxicity by maternal NAC therapy.

Digoxin-specific Fab fragments in the treatment of oleander toxicity in a canine model

STUDY OBJECTIVE

To examine the efficacy of digoxin-specific Fab fragments (dsFab) in the treatment of experimentally induced Nerium oleander cardiac glycoside toxicity in a dog model.

DESIGN

A nonblined, placebo-controlled experiment.

SUBJECTS

Ten adult greyhound dogs of either sex divided into treatment and control groups of five dogs each.

INTERVENTIONS

A tincture of oleander was prepared and administered intravenously to each animal. After the onset of cardiotoxicity, the treatment group received 60 mg/kg dsFab IV.

MEASUREMENTS AND MAIN RESULTS

All dogs exhibited dysrhythmias meeting our criteria for cardiac glycoside cardiotoxicity within 27 minutes of beginning the infusion. Three of five control dogs had lethal dysrhythmias during the three-hour observation period. The remaining two control dogs exhibited dysrhythmias throughout the three-hour experiment. All five of the dsFab-treated dogs survived and converted to normal sinus rhythm within eight minutes of dsFab infusion. Three treatment animals reverted back to nonlethal and hemodynamically stable dysrhythmias after a mean of 107 minutes.

CONCLUSION

Large doses of dsFab are efficacious in the treatment of dysrhythmias in this canine model of N oleander cardiac glycoside poisoning.

Toxic effects of drugs used in the ICU. Nitroprusside, nitroglycerin, and angiotensin-converting enzyme inhibitors

Sodium nitroprusside causes cyanide poisoning at currently recommended infusion rates. Serum thiocyanate concentrations are of no value in detecting cyanide poisoning caused by nitroprusside. Methemoglobinemia in those patients receiving intravenous nitroglycerin may seriously impair oxygen delivery and is not always accompanied by cyanosis in anemic patients. Angiotensin-converting enzyme inhibitors are responsible for a plethora of adverse effects, including renal insufficiency, hypotension, angioedema, cough, and increased insulin sensitivity.

Lack of evidence for a percent saturation gap in cyanide poisoning

STUDY OBJECTIVES

To determine if toxic concentrations of cyanide in blood result in a difference between calculated and measured percent hemoglobin oxygen saturation (percent saturation gap).

DESIGN

An in vitro laboratory study.

SETTING

Hospital laboratory.

TYPE OF PARTICIPANTS

Arterial blood from five stable patients residing in a tertiary hospital ICU. Venous blood samples obtained from five healthy volunteers.

INTERVENTIONS

Two-mL aliquots from each blood sample were placed into four test tubes and mixed with phosphate buffer. Cyanide was added to three of the tubes so that the four tubes contained 0, 6, 12, and 25 mg/L cyanide.

MEASUREMENTS AND MAIN RESULTS

The percent saturation gap was calculated by subtracting the percent oxyhemoglobin measured on an oximeter from the percent saturation calculated by a blood gas analyzer. Using two-tailed, paired t tests, we could not demonstrate a difference in mean percent saturation gaps between arterial samples or venous samples with and without cyanide. All blood samples had a normal percent saturation gap (P greater than .99 by Fisher's exact test). We had greater than a 95% chance of demonstrating a difference in mean percent saturation gaps of only 0.46% in arterial blood and of 3.3% in venous blood if such a difference existed.

CONCLUSIONS

Our results, as well as a review of the literature, indicate that there are no data supporting the suggestion that a percent saturation gap should imply the diagnosis of poisoning by inorganic cyanide.

Refractory hypoglycemia secondary to topical salicylate intoxication

We describe a case of severe refractory hypoglycemia secondary to topical salicylate intoxication. A 72-year-old man with psoriasis and end-stage renal disease was treated with a topical cream containing 10% salicylic acid. The patient presented with encephalopathy and subsequently developed hypoglycemia refractory to infusions of large amounts of glucose. A serum salicylate concentration was elevated at 3.2 mmol/L. Emergent hemodialysis was accompanied by rapid lowering of serum salicylate concentration and resolution of refractory hypoglycemia. Salicylate is well absorbed across normal and diseased skin. Salicylate markedly impairs gluconeogenesis and increases glucose utilization, resulting in hypoglycemia. To our knowledge, this is the first article on hypoglycemia due to the application of topical salicylate.

Lovastatin use and muscle damage in healthy volunteers undergoing eccentric muscle exercise

We did a double-blind, placebo-controlled crossover study of 10 healthy young men taking no medications to determine if ingesting lovastatin is associated with more severe muscle damage after exercise. Five men in the first group took 40 mg of lovastatin daily for 30 days while those in the second group took an identical-appearing placebo. Each volunteer then walked downhill on a -14-degree incline on a treadmill at 3 km per hour for an hour. After a 2-week rest, the subjects were crossed over. Serial serum creatine kinase activity was measured immediately before and 8, 24, 48, 72, 120, and 144 hours after each treadmill session. With each subject serving as his own control, peak mean serum creatine kinase activity (/+- SEM) following treadmill after lovastatin therapy was similar to that following placebo (168.4 +/- 25.8 U per liter versus 146.7 +/- 14.7 U per liter, respectively [P = .9]). With an alpha value of .05, we had greater than a 99% chance of detecting a difference in the rise of serum creatine kinase activity of 200 U per liter between groups. Our data suggest that lovastatin is not an independent risk factor for developing exercise-induced muscle damage using this model of exercise in our study population.

Acute lead poisoning in nursing home and psychiatric patients from the ingestion of lead-based ceramic glazes

To our knowledge, acute inorganic lead poisoning from single ingestions of lead compounds has been only rarely reported. During a 14-month period, we were contacted regarding eight instances of acute ingestions of liquid lead-based ceramic glazes by mentally impaired residents of nursing homes or psychiatric facilities participating in ceramic arts programs. While some ingestions did not cause toxic effects, some patients developed acute lead poisoning characterized by abdominal pain, anemia, and basophilic stippling of red blood cells. In the blood of several patients, lead concentrations were far above normal (4 to 9.5 mumol/L). Urinary lead excretions were tremendously elevated during chelation therapy, with one patient excreting 535.9 mumol/L of lead during a 6-day period, the largest lead excretion ever reported in a patient suffering from acute lead poisoning, to our knowledge. All patients recovered following supportive care and appropriate use of chelating agents. Lead-based glazes are commonly found in nursing homes and psychiatric facilities. We suspect that acute or chronic lead poisoning from the ingestion(s) of lead-based ceramic glazes may be an unrecognized but not uncommon problem among such residents. We urge physicians to take ingestions of lead-based glazes seriously and to consider the diagnosis of lead poisoning in nursing home and psychiatric patients who have participated in ceramic crafts programs.

Marijuana

Marijuana remains a complex, poorly understood drug with many effects. Although its acute psychological effects are well described, data linking cannabis use to chronic psychiatric or social problems and decreased driving or workplace safety are much less clear. Current laboratory procedures have not yet been shown useful to demonstrate acute intoxication, so they remain screening instruments for those interested in detecting cannabis use for other reasons. Although both acute and chronic effects of marijuana use have been described, they appear to be less than other commonly abused substances, including tobacco and alcohol. The rare acute complications that present to the Emergency Department can be managed with conservative measures.

An ovine model of maternal iron poisoning in pregnancy

An ovine model of maternal iron poisoning in pregnancy was used to examine the placental transport of deferoxamine and ferrioxamine and to follow maternal and fetal serum iron concentrations when maternal serum iron levels exceeded total iron-binding capacity. Ewes in the third stage of gestation underwent hysterotomy and delivery of the fetal head through an abdominal incision while under ketamine and halothane anesthesia. The fetal external jugular vein was catheterized for sampling of venous blood while the fetus remained in utero. Administration of deferoxamine mesylate or ferrioxamine mesylate IV to ewes was not accompanied by measurable deferoxamine or ferrioxamine in fetal blood. In a final experiment, four gravid ewes in a control group received 2 mg/kg maternal body wt iron IV over 60 minutes. An experimental group comprising another four ewes received similar doses of iron but then received 50 mg/kg deferoxamine mesylate IV over 15 minutes. Control and deferoxamine ewes reached similar peak maternal serum iron concentrations (2,479 +/- 266 and 2,121 +/- 343 micrograms/dL, respectively). The markedly elevated maternal serum iron concentrations were not accompanied by meaningful elevations in fetal serum iron levels over baseline values. Maternal deferoxamine infusion resulted in a more rapid fall in maternal serum iron concentrations but had no effect on fetal serum iron levels. The ovine fetus appears to be protected from elevated maternal serum iron concentrations in the last trimester of pregnancy. It could not be demonstrated that meaningful quantities of deferoxamine or ferrioxamine cross the placenta in the last trimester.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenytoin absorption in volunteers receiving selected enteral feedings

Phenytoin absorption is reportedly significantly altered in the presence of continuously administered enteral feedings, resulting in subtherapeutic serum phenytoin concentrations and loss of seizure control. We administered 500 mg of phenytoin as the suspension to five volunteers who were not receiving enteral feeding, again while they ingested protein hydrolysate enteral feedings hourly, and again during hourly ingestions of meat-base enteral feeding. Serum phenytoin concentrations, measured 3, 6, 9, 12, and 24 hours after phenytoin ingestion, were lowest with protein hydrolysate feedings. Mean serum phenytoin concentrations were consistently higher with the meat-base feeding than with the protein hydrolysate formula, although levels did not reach those of the control period. These data are in keeping with our previous observation that it is easier to attain therapeutic serum phenytoin concentrations in patients receiving a meat-base enteral feeding than in those receiving a protein hydrolysate formula.

The legitimacy of rattlesnake bites in central Arizona

Previous authors have classified poisonous snake bites as being legitimate or illegitimate, depending on whether the victim was taking unnecessary risks with a snake before being bitten. We reviewed medical records of 86 consecutive rattlesnake bite victims cared for at a single medical center to determine legitimacy of snake bites. A bite was considered illegitimate if, before being bitten, the victim recognized an encounter with a snake but did not attempt to move away from the snake. A legitimate bite was said to have occurred if a person was bitten before an encounter with a snake was recognized or was bitten while attempting to move away from a snake. The study group was made up of 75 male (87.2%) and 11 female (12.8%) victims. Seventy-four percent were 18 to 50 years old, and 15% had been bitten previously. Only 43.4% of all bites were considered legitimate, and pet (captive) snakes accounted for almost one third of all illegitimate bites. The ingestion of alcoholic beverages was associated with 56.5% of illegitimate bites versus 16.7% of legitimate bites (P less than .001). While 74.4% of bites were to upper extremities, only 27% of upper extremity bites were legitimate. All bites to the lower extremity were legitimate (P less than .001). Of 14 individuals bitten by pet snakes, all were men and 64.3% were under the influence of alcohol at the time of the bite.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial serum drug concentrations and prolonged anticholinergic toxicity after benztropine (Cogentin) overdose

A 38-year-old man overdosed on benztropine mesylate (Cogentin; Merck Sharpe & Dohme, West Point, PA) and developed anticholinergic poisoning syndrome, which lasted nine days. Serial serum benztropine concentrations were obtained during his hospitalization. Fluctuating benztropine levels suggested that his lengthy intoxication may have been secondary to prolonged, intermittent absorption rather than from slow plasma clearance. This is believed to be the first report of serial serum benztropine concentrations after overdose.

Pemoline-induced choreoathetosis and rhabdomyolysis

Pemoline is an indirectly acting sympathomimetic with actions similar to amphetamine and methylphenidate. While choreoathetosis is a well-recognised complication of acute or chronic amphetamine abuse, only 3 previous case reports have implicated pemoline in such a movement disorder. We report a 49-year-old man who developed severe choreoathetosis with rhabdomyolysis after markedly increasing his intake of pemoline. Abnormal movements responded to diazepam and completely resolved over 48 hours. He made a complete recovery with supportive care. This is only the second case of pemoline-induced choreoathetosis in an adult reported in the English literature, and the first case of rhabdomyolysis and myoglobinuria complicating choreoathetosis.

Successful treatment with antivenin of marked thrombocytopenia without significant coagulopathy following rattlesnake bite

We cared for two rattlesnake bite victims who developed platelet counts of 21,000/mm3 and 22,000/mm3. Both had only mild defibrination without evidence of intravascular clotting. In both cases, the administration of antivenin was followed promptly by a sustained rise in platelet counts.