Poisoned Patient

Toxicodynamics Toxicodynamics is a term used to denote the injurious effects of toxins, ie, their pharmacodynamics. A knowledge of toxicodynamics can be useful in the diagnosis and management of poisoning. For example, hypertension and tachycardia are typically seen in overdoses with amphetamines, cocaine, and antimuscarinic drugs. Hypotension with bradycardia occurs with overdoses of calcium channel blockers, beta-blockers, and sedative-hypnotics. Hypotension with tachycardia occurs with tricyclic antidepressants, phenothiazines, and theophylline. Hyperthermia is most frequently a result of overdose of drugs with antimuscarinic actions, the salicylates, or sympathomimetics. Hypothermia is more likely to occur with toxic doses of ethanol and other CNS depressants. Increased respiratory rate is often a feature of 

Management of the poisoned patient consists of maintenance of vital functions, identification of the toxic substance, decontamination procedures, enhancement of elimination, and, in a few instances, the use of a specific antidote. 

Osmolar gap The osmolar gap is the difference between the measured osmolarity (measured by the freezing point depression method) and the predicted osmolarity  

This gap is normally zero. A significant gap is produced by high serum concentrations of intoxicants of low molecular weight such as ethanol, methanol, and ethylene glycol. 

Antimuscarinic dmgs (atropine, some antidepressarts and antihistaminics, jimsonweed, etc) Delirium, hallucinations, seizures, coma, tachycardia, hypertension, hyperthermia, mydriasis, decreased bowel sounds, urinary retention Control hyperthenaia physostigmine may be helpful, but not for tricyclic overdose 

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Czeizel AE. 1994. Phenotypic and cytogenetic studies in self-poisoned patients. Mutat Res 313 175-181. 

Pond, S.M., S.C. Johnston, D.D. Schoof, E.C. Hampson, M. Bowles, D.M. Wright, and JJ. Petrie. 1987. Repeated hemoperfusion and continuous arteriovenous hemofiltration in a paraquat poisoned patient. Clin. Toxicol. 25 305-316. 

An almond-like smell in the breath of a poisoned patient can warn a physician that the individual may be suffering from cyanide poisoning. Approximately 60-70% of the population can detect the bitter almond odor of hydrogen cyanide. The odor threshold for those sensitive to the odor is estimated to be 1-5 ppm in the air. However, even at high toxic concentrations up to 20% of all individuals are genetically unable to smell hydrogen cyanide (Snodgrass 1996). Some effects of cyanide that can also be used to monitor exposure are discussed in Section 2.5.2. 

Biological oxidation of methanol and ethanol in the body produces the corresponding aldehyde followed by the acid. At times the alcoholics, by mistake, drink ethanol, mixed with methanol also called denatured alcohol. In the body, methanol is oxidised first to methanal and then to methanoic acid, which may cause blindness and death. A methanol poisoned patient is treated by giving intravenous infusions of diluted ethanol. The enz5mie responsible for oxidation of aldehyde (HCHO) to acid is swamped allowing time for kidneys to excrete methanol. 

All new developments have a flip side. The availability of slow-release theophylline has produced new problems for toxicologists. In overdose theophylline is potentially lethal. When a poisoned patient arrives at hospital, a plasma concentration is measured and, for most drugs, it can reasonably be assumed that the absorptive phase would be nearing completion (or can be shortened by gastric aspiration or giving charcoal by mouth). No such... 

It is important to know the differences between pharmacokinetics and toxicokinetics as the understanding of these differences will guide the physician in managing the poisoned patient. 

In many countries around the world, poison information centres are established to address the concerns of the general public as well as the needs of health professionals in managing a poisoned patient. Historically, the poison centres arose from the need to provide information on the diagnosis and treatment of poisoning cases. In the United States, for... 

Care of the patient s airway, respiratory support, and treatment of cardiovascular abnormalities are all part of the early support that may be required. The needs for these situations are common to all medical emergencies, though in the poisoned patient, potential interactions between therapy and suspected poison(s) must be considered. 

This used to be one of the most popular methods for gastric decontamination but should not be considered a routine procedure for all poisoned patients. 

Current evidence demonstrated no benefit for the use of gastric lavage in the management of acute poisoning patients and may increase the risk for iatrogenic complications. 

No clinical studies are at hand to study the effect of cathartic, with or without activated charcoal, in reducing the bioavailability of drugs of to improve the outcome of poisoned patients hence the routine use of cathartic with activated charcoal is not recommended in the clinical management of oral poisoning following drug overdoses. 

Hemoperfusion is like hemodialysis except that blood is circulated extracorporeally through a column with adsorbent material like resin or charcoal, which binds molecules electrostatically. The molecules likely to be removed are characterized as poorly dialyzable, lipid-soluble, protein bound. Among the indications for hemoperfusion in the management of poisoning include the presence of a poison in a patient with impairment of excretory system (i.e. damaged kidneys), intoxication of a drug known to produce delayed toxicity or metabolized to a more toxic metabolite (i.e. paraquat or methotrexate), deterioration of the clinical state of the poisoned patient despite conservative therapy (i.e. convulsions or cardiac arrhythmias following theophylline intoxication), or development of coma as a complication. 

Toxicology is an interesting medical discipline. The principles of management are prevention, toxicovig-ilance and careful assessment of the clinical features of the poisoned patient, and providing timely and appropriate therapy. In most cases, these are symptomatic and supportive measures, on top of decontamination, elimination of the poison, and provision of specific antidotes. 

Kulig K, Bar-Or D, Cantrill TV, Rosen P, Rumack BH. Management of acutely poisoned patients without gastric emptying. Ann Emerg Med 1984 14 562-67. 

Olson KR, Pentel PR, Kelley MT. Physical assessment and differential diagnosis of the poisoned patient. Med Toxicol Adverse Drng Exp 1987 2(1) 52-81. 

Acetaminophen (paracetamol) poisoning is common in Western countries and is increasing elsewhere. Single doses as low as 7.5 g in adults or 150 mg/kg in a child can cause severe toxicity. Very occasionally, lower doses cause harm. Mortality, from hepatic or occasionally renal failure, is related to blood concentration and the time between ingestion and the initiation of antidotal treatment. Even severely poisoned patients may be asymptomatic, although nausea and vomiting are fairly common. 

A higher proportion of salicylate is ionized in alkaline urine, and ionized salicylate is not reabsorbed. Urine can be made alkaline to pH 8-8.5 by giving sodium bicarbonate 100 mM in glucose 5% solution 1 litre at 100-200 ml/h. Overhydration can provoke pulmonary oedema, especially in seriously poisoned patients. 

Chapter 57 Heavy Metal Intoxication Chelators Chapter 58 Management of the Poisoned Patient... 

Basic and Clinical Pharmacology > Chapter 58. Management of the Poisoned Patient >... 

APPROACH TO THE POISONED PATIENT HOW DOES THE POISONED PATIENT DIE ... 

At this point, every patient with altered mental status should receive a challenge with concentrated dextrose, unless a rapid bedside blood glucose test demonstrates that the patient is not hypoglycemic. Adults are given 25 g (50 mL of 50% dextrose solution) intravenously, children 0.5 g/kg (2 mL/kg of 25% dextrose). Hypoglycemic patients may appear to be intoxicated, and there is no rapid and reliable way to distinguish them from poisoned patients. Alcoholic or malnourished patients should also receive 100 mg of thiamine intramuscularly or in the intravenous infusion solution at this time to prevent Wernicke s syndrome. 

Oral statements about the amount and even the type of drug ingested in toxic emergencies may be unreliable. Even so, family members, police, and fire department or paramedical personnel should be asked to describe the environment in which the toxic emergency occurred and should bring to the emergency department any syringes, empty bottles, household products, or over-the-counter medications in the immediate vicinity of the possibly poisoned patient. 

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