Toxicology | poisoning and over-dosage

Poisoning is an adverse effect from a chemical that has been taken in excessive amounts. The body is able to tolerate and, in some cases, detoxify a certain dose of a chemical; however, once a critical threshold is exceeded, toxicity results. Poisoning can produce minor local effects that can be treated readily in the outpatient setting or systemic life-threatening effects that require intensive medical intervention.

Poisoning is an adverse effect from a chemical that has been taken in excessive amounts

This spectrum of toxicity is typical for many chemicals with which humans come in contact. Virtually any chemical can become a poison when taken in sufficient quantity, but the potency of some compounds leads to serious toxicity with small quantities

Poisoning by chemicals includes exposure to drugs, industrial chemicals, household products, plants, venomous animals, and agrochemicals. This chapter describes some examples of this spectrum of toxicity, outlines means to recognize poisoning risk, and presents principles of treatment.

Epidemiology

Each year poisonings account for approximately 37,000 deaths and at least 1.7 million emergency department visits in the United States. Males have a nearly two-fold higher incidence of death than do females and 15% of adult poisoning deaths are attributed to suicide. Approximately 0.2% of poisoning deaths involve children younger than 5 years. Of emergency department visits, typically 31% involve illicit drugs only, 28% involve pharmaceuticals only, 13% involve illicit drugs with alcohol, and 10% involve alcohol with pharmaceuticals. Approximately 40% of emergency department visits for poisoning involve abuse of prescription and nonprescription drugs with one half of these patients taking multiple drugs.

The number and rates of poisoning deaths from all circumstances have been increasing steadily, with a 90% overall increase from 1999 to 2006, representing 37,286 deaths in 2006. This increasing mortality trend has placed poisoning as the second leading cause of injury death overall and the leading cause of injury death of people 35 to 54 years of age. Poisoning deaths were most frequently due to drugs. The number of deaths from opioid analgesics has nearly tripled from 1999 to 2006 and opioids were involved in nearly 40% of all poisoning deaths in 2006.

Several databases in the United States provide different levels of insight into and documentation of the poisoning problem. Poisonings documented by U.S. poison centers are compiled in the annual report of the American Association of Poison Control Centers’ National Poison Data System (AAPCCNPDS). Although it represents the largest database on poisoning, it is not complete because it relies on individuals voluntarily contacting a poison control center.

The AAPCC-NPDS dataset captures approximately 5% of the annual number of deaths from poisoning tabulated in death certificates. Despite this shortcoming, AAPCC-NPDS provides valuable insight into the characteristics and frequency of poisonings. In the 2007 AAPCC-NPDS summary, 2,482,041 poisoning exposures were reported by 61 participating poison centers that served the entire United States. 5 Children younger than 6 years accounted for 51% of cases. The home was the site of exposure in 93% of the cases, and a single substance was involved in 91% of cases. An acute exposure accounted for 91% of cases, 83% of which were unintentional or accidental exposures. Only 13% were intentional. Fatalities accounted for 1,239 (0.05%) cases, of which 3% were children younger than 6 years.

Economic impacts of poisoning

Poisoning accounted for a total lifetime cost of $12.6 billion annually in 2003 dollars. Estimates of the lifetime cost of injury include related healthcare costs and lost lifetime earnings of the victim; however, they do not include the costs of suffering, reduced productivity of caregivers, or legal costs. The definition of poisoning for this economic estimate excluded poisoning from alcohol and illicit drugs.

Poison prevention strategies

The number of poisoning deaths in children has declined dramatically over the past four decades, due, in part, to the implementation of several poison prevention approaches. These include the Poison Prevention Packaging Act (PPPA) of 1970, the evolution of regional poison control centers, the application of prompt first aid measures, improvements in overall critical care, development of less toxic product formulations, better clarity in the packaging and labeling of products, and public education on the risks and prevention of poisoning.

Although all these factors play a role in minimizing poisoning dangers, particularly in children, the PPPA has perhaps had the most significant influence. The intent of the PPPA was to develop packaging that is difficult for children younger than 5 years to open or to obtain harmful amounts within a reasonable period of time. However, the packaging was not to be difficult for normal adults to use properly. Safety packaging is required for a number of products and product categories

Child-resistant containers are not totally childproof and may be opened by children, which can result in poisoning. Despite the success of child-resistant containers, many adults disable the hardware or simply use no safety cap, thus placing children at risk. Fatigue of the packaging materials can occur, which underscores the need for new prescription ware for refills, as required in the PPPA.

Poison prevention requires constant vigilance because of new generations of families in which parents and grandparents must be educated on poisoning risks and prevention strategies. New products and changes in product formulations present different poisoning dangers and must be studied to provide optimal management. Strategies to prevent poisonings should consider the various psychosocial circumstances of poisoning, prioritize risk groups and behaviors, and customize an intervention for specific situations.

Treatment of poisoned patients

First Aid

The presence of adequate airway, breathing, and circulation should be assessed, and cardiopulmonary resuscitation should be started if needed. The most important step in preventing a minor exposure from progressing to a serious intoxication is early decontamination of the poison. Basic poisoning first aid and decontamination measures should be instituted immediately at the scene of the poisoning. If there is any question about the potential severity of the poison exposure, a poison control center should be consulted immediately (1-800-222-1222). While awaiting transport, placing the patient on the left side may afford easier clearance of the airway if emesis occurs and may slow absorption of drug from the gastrointestinal tract.

Ipecac Syrup

Ipecac syrup, a nonprescription drug, has been used in the United States for the past 50 years as a means to induce vomiting for treatment of ingested poisons. Despite its widespread use, concerns about its effectiveness and safety have been raised recently. An expert panel of North American and European toxicologists concluded that its routine use in the emergency department should be abandoned.

In 2003 the American Academy of Pediatrics issued a policy statement indicating that ipecac syrup was no longer to be used routinely to treat poisonings at home and that parents should discard any ipecac. 28 The key reason for the policy change was that research failed to show benefits in children who were treated with ipecac syrup. It likely will take several years for these recommendations to be adopted fully by parents and healthcare professionals, and rare exceptions may arise. In the 2007 AAPCC-NPDS report, 0.07% of 2.48 million cases received ipecac syrup, with or without poison center direction.

There are several contraindications to the use of ipecac syrup or any form of induced emesis, such as gagging. If the patient is without a gag reflex; is lethargic, comatose, or convulsing; or is expected to become unresponsive within the next 30 minutes, emesis should not be induced. If a fruitful emesis has occurred spontaneously shortly after ingestion, further emesis may not be necessary.

Ingestions of caustics, corrosives, ammonia, and bleach are definite contraindications to induced emesis. Ingestion of aliphatic hydrocarbons (e.g., gasoline, kerosene, and charcoal lighter fluid) typically does not require emesis. When the agent is definitely known to be nontoxic, induction of emesis is purposeless and potentially dangerous. The rapid onset of coma or seizures or the potential to exaggerate the toxic effects of the poison may preclude further the induction of emesis. Some examples include poisonings with diphenoxylate, propoxyphene, clonidine, tricyclic antidepressants, hypoglycemic agents, nicotine, strychnine, β -blocking agents, and calcium channel blockers. Debilitated, pregnant, and elderly patients may be further compromised by induction of emesis.

General Care

Supportive and symptomatic care is the mainstay of treatment of a poisoned patient. In the search for specific antidotes and methods to increase excretion of the drug, attention to vital signs and organ functions should not be neglected. Establishment of adequate oxygenation and maintenance of adequate circulation are the highest priorities. Other components of the acute supportive care plan include the management of seizures, arrhythmias, hypotension, acid-base balance, fluid status, electrolyte balance, and hypoglycemia. Placement of intravenous and urinary catheters is typical to ensure delivery of fluids and drugs when necessary and to monitor urine production, respectively.

Gastric Lavage

Gastric lavage involves the placement of an orogastric tube and washing out of the gastric contents through repetitive instillation and withdrawal of fluid. Gastric lavage may be considered only if a potentially toxic agent has been ingested within the past hour for most patients. If the patient is comatose or lacks a gag reflex, gastric lavage should be performed only after intubation with a cuffed or well-fitting endotracheal tube.

The largest orogastric tube that can be passed (external diameter at least 12 mm in adults and 8 mm in children) should be used to ensure adequate evacuation, especially of undissolved tablets. Lavage should be performed with warm (37°C–38°C) normal saline or tap water until the gastric return is clear; this usually requires 2 to 4 L or more of fluid. Relative contraindications for gastric lavage include ingestion of a corrosive or hydrocarbon agent. Complications of gastric lavage include aspiration pneumonitis, laryngospasm, and mechanical injury to the esophagus and stomach, hypothermia, and fluid and electrolyte imbalance.

Single-Dose Activated Charcoal

Reduction of toxin absorption can be achieved by administration of activated charcoal. It is a highly purified, adsorbent form of carbon that prevents gastrointestinal absorption of a drug by chemically binding (adsorbing) the drug to the charcoal surface. There are no toxin-related contraindications to its use, but it is generally ineffective for iron, lead, lithium, simple alcohols, and corrosives. It is not indicated for aliphatic hydrocarbons because of the increased risk for emesis and pulmonary aspiration. Activated charcoal is most effective when given within the first few hours after ingestion, ideally within the first hour.

Cathartics

Cathartics, such as magnesium citrate and sorbitol, were thought to decrease the rate of absorption by increasing gastrointestinal elimination of the poison and the poison-activated charcoal complex, but their value is unproven. Poisoned patients do not routinely require a cathartic, and it is rarely, if ever, given without concurrent activated charcoal administration. If used, a cathartic should be administered only once and only if bowel sounds are present. Infants, the elderly, and patients with renal failure should be given saline cathartics cautiously, if at all.

Whole-Bowel Irrigation

Polyethylene glycol electrolyte solutions, such as GoLYTELY and Colyte, are used routinely as whole-bowel irrigants prior to colonoscopy and bowel surgery. These solutions also can be used to decontaminate the gastrointestinal tract of ingested toxins. Large volumes of these osmotically balanced solutions are administered continuously through a nasogastric or duodenal tube for 4 to 12 hours or more. They quickly cause gastrointestinal evacuation and are continued until the rectal discharge is relatively clear.

Reference
Toxicology | poisoning and over-dosage Toxicology | poisoning and over-dosage Reviewed by gafacom on September 05, 2020 Rating: 5

No comments:

Powered by Blogger.