Initial management of ingestions of toxic substances

Toxicological Emergencies

Poisoning, drug overdose, and adverse drug effects continue to be a common encounter, especially in the intensive care unit (ICU). Patients are often critically ill or have a potential to rapidly deteriorate and warrant ICU admission. Adults suffering from overdoses rarely give a complete and accurate description of the quantity or type of medications ingested. In most adult cases, multiple substances are involved. A tentative diagnosis in most overdose and poisoning cases can be made by physical examination and simple laboratory tests (electrolyte panel, creatinine, serum osmolarity, urinalysis, etc). Supportive care, with particular attention to airway management, oxygenation, and circulation, is the mainstay of treatment. Basic treatment principles include limiting the amount of toxin absorbed, enhancing the elimination of ingested toxin, and preventing the conversion of non-toxic compounds to toxic metabolites. Drugs or poisons, where specific antidotes or effective therapies exist (especially acetaminophen, salicylates, methanol, ethylene glycol, and digitalis), should be aggressively sought and treated after initial stabilization has been accomplished. For those drugs or poisons where specific quantitative tests are available, levels should be obtained before treatment and may be repeated as clinically indicated.

A Nanoantidote Alleviates Glioblastoma Chemotoxicity without Efficacy Compromise

Cancer patients suffer from the toxicity of chemotherapy. Antidote, given as a remedy limiting poison, is an effective way to counteract toxicity. However, few antidotes abrogate chemotoxicity without compromising the therapeutic efficacy. Herein, a rationally designed nanoantidote can neutralize chemo-agents in normal cells but not enter tumors and thus would not interfere with the efficacy of tumor treatment. The nanoantidote, consisting of a dendrimer core wrapped by reductive cysteine, captures Temozolomide (TMZ, the glioblastoma standard chemotherapy). Meanwhile, thanks to the blood-brain barrier (BBB) and the size of the nanoantidote, the nanoantidote cannot enter glioblastoma. In murine models, the nanoantidote distributes in normal tissues without crossing the BBB, so it markedly reduces the chemotoxicity of TMZ and retains the original TMZ therapeutic efficacy. With most nanotechnologies focusing on antitumor treatment, this detoxicating strategy demonstrates a nanoplatform to reduce chemotoxicity using physiology barriers and introduces a new approach to nanomedicine for cancer chemotherapy.

Converting Red Blood Cells to Efficient Microreactors for Blood Detoxification

A simple method to convert red blood cells (RBCs) into efficient microreactors is reported. Triton X-100 is employed at finely tuned concentrations to render RBCs highly permeable to substrates, while low concentrations of glutaraldehyde are used to stabilize cells. The ability for blood detoxification of these microreactors is demonstrated.

Emergency care and managing toxicoses in the exotic animal patient

The poisoned exotic veterinary patient remains a significant challenge to the clinician. A patient presenting with the history of exposure to a toxin or poison should be considered to have a potentially life-threatening problem. This article details the ABCs of emergency medicine including fluid therapy and discusses the principles of neurologic management. The last part of the article provides the clinician with guidelines for decontamination and critical care management of some of the more common toxicoses in exotic animals.

The approach to the patient with an unknown overdose

Toxic overdose can present with various clinical signs and symptoms. These may be the only clues to diagnosis when the cause of toxicity is unknown at the time of initial assessment. The prognosis and clinical course of recovery of a patient poisoned by a specific agent depends largely on the quality of care delivered within the first few hours in the emergency setting. Usually the drug or toxin can be quickly identified by a careful history, a directed physical examination, and commonly available laboratory tests. Once the patient has been stabilized, the physician must consider how to minimize the bioavailability of toxin not yet absorbed, which antidotes (if any) to administer, and if other measures to enhance elimination are necessary.

Endocrine effects of organophosphate antidotal therapy

To determine the endocrine effects of the treatment of organophosphate poisoning, this prospective study was conducted in a university-based emergency department among patients with a history and clinical findings compatible with those of organophosphate poisoning. Thyrotrophin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), progesterone (PRG), adrenocorticotropic hormone (ACTH), cortisol, and testosterone (TST) levels were analyzed before and after treatment with atropine and pralidoxime. The Wilcoxon's sign rank sum (nonparametric) test was used to compare dependent variables before and after treatment. A total of 44 patients (19 male; mean age: 28.5 +/- 12.6 y) were enrolled in the study. Patients were hospitalized for 5.4 +/- 1.3 days. Posttreatment ACTH, cortisol, PRL, FT3, FSH, and PRG levels were significantly lower than pretreatment levels (P < .05). The decrease in TSH, LH, and TST levels did not reach statistical significance, while FT4 levels increased following the treatment (P < .05). Six patients were diagnosed on admission with sick euthyroid syndrome, and 11 patients who were euthyroid on admission developed sick euthyroid syndrome following treatment. ACTH, cortisol, PRL, FT3, FT4, FSH, and PRG levels are affected by acute organophosphate poisoning. The change in hormone levels may result from the effects of neurotransmitters, from the direct effect of the toxic agent, or from stress associated with events leading to the poisoning incident.

Single‐Dose Activated Charcoal‐Backup and Reassess

Single-dose activated charcoal (SDAC) is frequently administered to poisoned patients. The assumption is that toxin absorption is prevented and that toxicity (as defined by morbidity and mortality) of the poisoning is decreased. Yet there is no evidence that SDAC improves outcome. Risks of this procedure have not been determined. The reported adverse events following SDAC administration are reviewed and risk:benefit ratio for this procedure is discussed.

Diagnostic data in clinical toxicology--should we use a Bayesian approach?

A number of toxidromes (toxicology syndromes) have been described for various poisonings and are promoted as a means of reaching a diagnosis in patients presenting with unknown poisonings. Many are based entirely on deductive reasoning from the known pharmacological effects of these drugs rather than on documented clinical experience. In this paper, we used our database, where we have recorded clinical signs on presentation in unselected poisonings to explore how clinical signs actually alter the odds of ingestion of different poisons. Many signs substantially altered the list of drugs likely to have been ingested. We found that the most important factor determining whether an unconscious patient had ingested a particular drug was how frequently that drug was taken generally (i.e., the a priori probability), rather than the presence of any particular physical sign. It also follows that our (or anyone else's) intuitive or deductive approach to diagnosis, derived from experience, will not necessarily be very useful at another place where predominantly different drugs are involved in poisoning. Our data were used to derive odds ratios as a measure of the strength of association of physical signs or investigations with ingested poisons. These can be used to develop simple diagnostic algorithms orflow charts to identify the most likely drugs ingested, or using more complicated programming, could also be used to calculate the precise probability of different drug-ingestion using Bayes' Theorem. The usefulness (i.e., external validity) of clinical research from other centers can also be determined.

Extracorporeal therapies for acute intoxications

Intoxications frequently perturb acid-base and electrolyte status, intravascular volume, and renal function. In selected cases, extracorporeal techniques effectively restore homeostasis and augment intoxicant removal. The use of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, is a new and effective treatment for patients exposed to toxic alcohols. In this section, practical approaches to commonly encountered intoxicants and the use of extracorporeal techniques are critically reviewed.

Parasuicidal poisoning treated in a Greek medical ward: epidemiology and clinical experience

OBJECTIVE

To study the epidemiology of acute poisoning patients presenting to an acute medical service ward in a Greek hospital between January 1998 and December 2000.

DESIGN

Prospective case series.

RESULTS

A total of 273 patients with self-poisoning were included in the study. This represented 3.8% of the overall admissions to the unit. The mean age of patients was 33, the most frequent age group being that aged 20-30 years (36.2% of total) with a male-to-female ratio of 1:1.97. Sixty per cent of patients was admitted within 4 h. Those from urban areas comprised 76.2% and 23.8% from rural areas. The most frequently ingested agents were psychopharmaceuticals (37.4%) and analgesics/anti-rheumatics (32.6%). Pesticides (7.7% of total) were most frequently used by patients coming from rural areas (32.3% of patients from rural areas). Alcohol was included in the overdose in 8.4%. Of the patients, 16.2% had a previous history of overdose. In this case series, psychiatric assessment suggested that 52% of the patients had a formal psychotic diagnosis, 21% had personality disorder and 27% had taken an overdose in response to stress. The most frequently documented precipitating factors were family problems and disputes (37%). Unusually, the seasonal distribution in these patients suggested a peak in summer (37.5% of presentations) with lower numbers in spring (30.2%), autumn (17.7%) and winter (14.6%). Of the patients, 23.7% presented in July. A total of 73.5% of patients was conscious, 16.4% was somnolent, 4.5% was in precoma and 5.6% was in coma (GCS <8). Patients who received antidotal therapy comprised 17.9%. Evidence of hepatic dysfunction was observed in 8.9% of patients and renal dysfunction in 3.6%. Extracorporeal techniques for drug removal (hemodialysis and hemoperfusion) were used in 2.2% of patients. Intensive care therapy was required in 11.4% of patients. The mean overall hospitalization time was 3.3 days. The mortality rate was 2.9%.

CONCLUSIONS

This study shows that the epidemiology of self-harm by overdose in Greece is significantly different in terms of the seasonal presentation from other parts of Europe. The agents ingested and other features are similar to northern Europe. Psychiatric diagnoses are more common in our group than in those reported from northern Europe.

Chemical Hazards and Poison Control for the Health Professional—Review of Select Principles and Exposures

Exposure to a wide variety of chemicals can pose significant hazards to patients, and present health care professionals with scenarios that require proper assessment and treatment. Knowing when a chemical exposure requires emergency medical attention is equally as important as knowing when such assistance is not necessary and that simple treatment measures performed at home will suffice. This current discussion is intended to highlight selected principles and clinical information pertaining to common chemical exposures, but not to replace the full spectrum of information that would be available to health care professionals (and the lay public) by contacting their nearest poison control center. There are several factors that should be considered when assessing the nature of and possible clinical outcomes (and medical needs) from patient exposure to chemicals. Identification of the chemical(s) involved, events leading up to the exposure, route of exposure (e.g., ingestion, dermal, inhalation, ocular), patient medical history and current symptoms, are just a few of the variables that must be ascertained before various treatment approaches can be undertaken.

Laboratory support for the poisoned patient

Poisoning often does not require toxicology laboratory analysis, though support is necessary from the departments of hematology and biochemistry. There are some compounds, such as paracetamol (acetaminophen), lithium, and methanol, for which quantitative or qualitative analysis is essential for effective patient management. Standard methods such as immunoassays, chromatography, and spectrophotometry have been extended by mass spectrometry and will be enhanced by nuclear magnetic resonance and by hyphenated techniques (e.g., LC-MS-MS). The new perspectives that can be gained with these techniques may greatly improve our knowledge of toxicokinetics and enable better patient management. Comatose patients and those with suspected brain death comprise a difficult group requiring comprehensive toxicologic screens. Although current immunoassay-chromatography methods are adequate, it is to be hoped that more comprehensive screens are achievable. The author has performed trials on TLC-FABMS-MS as a potential procedure and has obtained satisfactory preliminary results. This and other spectrometric-spectroscopic methods may be the techniques of the future for reference centers.

Near fatal anticholinergic intoxication after routine fundoscopy

We describe a case of severe anticholinergic intoxication following the topical instillation of tropicamide-containing eyedrops. Tropicamide is a short-acting atropine-like derivative and has been regarded as an effective and safe mydriatic. Half an hour after routine fundoscopy, a 62-year-old man experienced two generalized seizures with respiratory arrest and required intubation and mechanical ventilation. The patient was treated with physostigmine and made a full recovery.

Prehospital gastrointestinal decontamination of toxic ingestions: a missed opportunity

The purpose of this study was to determine if emergency medical services (EMS) providers routinely initiate field gastrointestinal decontamination of adult drug overdose patients transported to the emergency department (ED). A retrospective prehospital chart review was performed on adult patients identified as drug overdose who were transported by EMS. ED charts on patients transported to a university hospital were reviewed for follow-up data. Prehospital care records showed that gastrointestinal decontamination was initiated in only 6 of 361 (2%) patients, all of whom received ipecac. No patient received activated charcoal. The median transport time was 25 minutes (range, 5 to 66 minutes). Follow-up data on patients transported to the university hospital revealed that 30 of 43 (70%) patients who might have been suitable candidates for prehospital activated charcoal actually received activated charcoal in the ED. Median time to activated charcoal in the ED was 82 minutes (range, 32 to 329 min). Use of activated charcoal in the field appears to be deferred despite its known loss of efficacy over time. The failure to start activated charcoal in the field contributes to the delay in initiating activated charcoal therapy.

Potential time savings by prehospital administration of activated charcoal

OBJECTIVE

Activated charcoal (AC) has been proven useful in many toxic ingestions. Theoretically, administration of AC in the prehospital environment could save valuable time in the treatment of patients who have sustained potentially toxic oral ingestions. The purpose of this study was to determine the frequency of prehospital AC administration and to identify time savings that could potentially result from field AC administration.

METHODS

Adult patients with a chief complaint of toxic ingestion who had complete emergency medical services (EMS) and emergency department (ED) records and no medical treatment (gastric emptying, AC administration) prior to EMS arrival were eligible for inclusion. Data obtained from EMS and ED records included time of EMS departure from the scene, time of EMS arrival at the ED, and time of administration of AC in the ED. Since most EMS agencies in this system do not insert gastric tubes, patients requiring gastric tube placement for administration of AC were excluded.

RESULTS

Twenty-nine of 117 (24.8%) adult patients received oral AC with no other intervention. None of the 117 patients received AC in the prehospital setting. The EMS transport time for these patients ranged from 5 to 43 minutes (mean 16.2 +/- 9.7 minutes). The delay from ED arrival to AC administration ranged from 5 to 94 minutes (mean 48.8 +/- 24.1 minutes), and was more than 60 minutes for 14 (48.2%) of the patients. The total time interval from scene departure to ED AC administration ranged from 17 to 111 minutes (mean 65.0 +/- 25.9 minutes).

CONCLUSIONS

In a selected subset of patients who tolerate oral AC, prehospital administration of AC could result in earlier and potentially more efficacious AC therapy. Prospective study of the benefits and feasibility of prehospital AC administration is indicated.

Effect of activated charcoal on the pharmacokinetics of pholcodine, with special reference to delayed charcoal ingestion

We conducted a randomized study with four parallel groups to investigate the effect of single and multiple doses of activated charcoal on the absorption and elimination of pholcodine administered in a cough syrup. The first group received 100 mg of pholcodine on an empty stomach with water only (control); the second group took 25 g of activated charcoal immediately after pholcodine; the third group received 25 g of activated charcoal 2 h and the fourth group 5 h after ingestion of the 100-mg dose of pholcodine. In addition, the fourth group received multiple doses (10 g each) of charcoal every 12 h for 84 h. Blood samples were collected for 96 h and urine for 72 h. Pholcodine concentrations were measured by high-performance liquid chromatography. A significant reduction in absorption was found when charcoal was administered immediately after pholcodine; the AUC0-96h was reduced by 91% (p < 0.0005), the Cmax by 77% (p < 0.0005), and the amount of pholcodine excreted into urine by 85% (p < 0.0005). When charcoal was administered 2 h after pholcodine, the AUC0-96h was reduced by 26% (p = 0.002), the Cmax by 23% (p = NS), and the urinary excretion by 28% (p = 0.004). When administered 5 h after pholcodine, charcoal produced only a 17% reduction in the AUC0-96h (p = 0.06), but reduced the further absorption of pholcodine still present in the gastrointestinal tract at the time of charcoal administration, as measured by AUC5-96h (p = 0.006). Repeated administration of charcoal failed to accelerate the elimination of pholcodine. We conclude that activated charcoal is effective in preventing the absorption of pholcodine, and its administration can be beneficial even several hours after pholcodine ingestion.

Seizure resulting from a venlafaxine overdose

OBJECTIVE

To report a case of venlafaxine overdose.

CASE SUMMARY

A 40-year-old woman with major depression took an overdose of venlafaxine in an apparent suicide attempt. After the ingestion of 26 venlafaxine 50-mg tablets, the patient experienced a witnessed generalized seizure. She was admitted to the medical intensive care unit, venlafaxine was discontinued, and no further sequelae were seen.

DISCUSSION

To our knowledge, this is the first reported case of venlafaxine overdose that resulted in a generalized seizure. Based on nonoverdose pharmacokinetics and pharmacodynamics of venlafaxine and the potential risks of available interventions, no emergent therapy was instituted.

CONCLUSIONS

The venlafaxine overdose in our patient resulted in a single episode of generalized seizure but elicited no further sequelae.

Response to glucagon in imipramine overdose

A 25-year-old woman, severely hypotensive following a massive imipramine overdose, had an immediate and sustained rise in blood pressure following intravenous glucagon (10 mg bolus followed by an infusion of 10 mg over 6 h). The QRS interval on the electrocardiogram shortened from 129 to 89 msec. Glucagon should be considered in hypotension following tricyclic antidepressant overdose; it may also be antiarrhythmic.

The effect of activated charcoal on the absorption and elimination of astemizole

1. The effect of activated charcoal on the absorption and elimination of astemizole and its metabolites was studied in healthy volunteers. 2. Subjects were divided into three groups containing seven subjects each. One group received 30 mg of astemizole with water only (control) and another group with 25 g of activated charcoal. The third group received multiple doses (12 g) of charcoal from 6 h onwards twice daily for 8 days. The concentrations of astemizole and its metabolites in plasma were measured by radioimmunoassay for 192 h. 3. Activated charcoal, administered immediately after astemizole ingestion, reduced the absorption of astemizole by 85% (P < 0.001). Multiple doses of activated charcoal, administered throughout the period of astemizole elimination, had no significant effect on the rate of elimination or the area under the curve from 0 to 192 h. 4. The absorption of astemizole from the gastrointestinal tract can be effectively prevented with activated charcoal. Because astemizole is rapidly absorbed, charcoal should be administered as soon as possible in acute astemizole poisoning. Multiple doses of charcoal do not seem to shorten the elimination half-life of astemizole.

Ondansetron for treating nausea and vomiting in the poisoned patient

OBJECTIVE

To describe the efficacy of ondansetron for the treatment of poisoning-associated vomiting in two patients following drug intoxication.

PATIENTS

Two self-poisoned adolescent patients.

INTERVENTION

Intravenous ondansetron.

RESULTS

Resolution of nausea and vomiting in both patients.

CONCLUSIONS

Ondansetron appears to be a very effective antiemetic drug for use in selected intoxicated patients.

Effect of hypertonic sodium bicarbonate in the treatment of moderate-to-severe cyclic antidepressant overdose

The objective of this study was to characterize the effect of intravenous hypertonic sodium bicarbonate (NaHCO3) administration in patients with moderate-to-severe cyclic antidepressant (CA) overdose. We reviewed charts of all 91 patients given the diagnosis of CA overdose in the University of California Los Angeles (UCLA) Emergency Medicine Center (EMC), who either died in the EMC or were admitted to the medical intensive care unit (MICU), and who received NaHCO3 in the EMC between 1980 and 1988. Twenty-four other patients with the same EMC diagnosis were admitted to the MICU during this period but did not receive NaHCO3. The response of blood pressure, electrocardiographic parameters, and mental status to serum alkalinization with NaHCO3 were evaluated. Major morbidity and mortality were recorded for all patients. Hypotension was corrected within 1 hour in 20 of 21 (96%) patients, QRS prolongation corrected in 39 of 49 (80%), and mental status improved in 40 of 85 (47%). There was one death, in a patient who was moribund on arrival to the EMC. No complications were attributable to the administration of NaHCO3. NaHCO3 seems to improve hypotension and normalize QRS duration rapidly in most patients treated, and improve mental status changes in almost one half. Serum alkalinization with NaHCO3, in conjunction with appropriate supportive care, seems to limit major morbidity and mortality effectively in patients with serious CA overdose.

Hyperthermia associated with 3,4-methylenedioxyethamphetamine ('Eve')

A patient was admitted with hyperthermia, muscle rigidity, rhabdomyolysis and disseminated intravascular coagulation. He was initially thought to have taken 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy'), but subsequent toxicology revealed the presence of 3,4-methylenedioxyethamphetamine (MDEA, 'Eve'), its sister drug, in his blood. Subsequent in vitro testing for malignant hyperthermia proved to be negative.

Principles of antibody therapy

The success of monoclonal antibodies in clinical practice is dependent on good design. Finding a suitable target is the most important part as other properties of the antibody can be altered by genetic engineering. Antibodies that target lymphocyte antigens offer less toxic immunosuppressive treatment than currently available drugs and the first monoclonal antibody approved for human use is an immunosuppressive agent for treating rejection of renal transplants. Human trails of monoclonal antibodies to treat septic shock have been done and antibodies are also being developed to target common pathogens such as herpes simplex virus. Although monoclonal antibodies against cancer have been much heralded, their success has been limited by the poor access to the inside of tumours. Treatment of blood cancers has been more successful and a human antibody against B cell malignancies is being clinically tested. As knowledge about natural immune responses and antibody engineering increases many more monoclonals are likely to feature in clinical practice.