Toxicology 1: Systematic Approach
Caring for an acutely poisoned or overdosed patient requires a systematic approach. Because patients with toxicological emergencies can have a variety of clinical signs and symptoms, the physician managing these patients must be aware of a few classic telltale symptoms to make a rapid diagnosis. After an overdose, patients may have variable presentation ranging from being asymptomatic to being in cardiopulmonary arrest. Classic signs and symptoms for a specific drug or class of drugs are considered a toxidrome (or toxic syndrome). Examples of toxidromes include narcotic, stimulants or sympathomimetics, cholinergic, anticholinergic, sedative-hypnotic, and salicylate. By identifying the toxidrome the clinician may rapidly treat the patient with specific therapy, if available. A primary focus of the resuscitating team is rapid assessment of the patient’s ABCs. In addition, early administration of a specific antidote may be lifesaving and reduce morbidity. Thus, the initial approach should be ABCs and antidotal therapy. The poison center, available 24 hours a day at 1-800-222-1222, is a valuable resource in the assessment and treatment of the acutely poisoned patient.
Trauma must be considered in the unconscious patient where injuries may occur as a result of the altered mentation (falls, irrational acts). When evaluating patients presenting with trauma sustained in falls, motor vehicle crashes, or while operating dangerous machinery, consider a toxicological etiology.
After stabilizing the patient, perform a mini toxicology examination, focusing on level of consciousness, pupil size, reassessment of vital signs (including temperature), skin, abnormal motor activity, as well as any characteristic odors on the patient’s breath or clothing. Note whether the patient is somnolent, agitated, or hallucinating. Assess the vital signs for hyperthermia or hypothermia, hypertension or hypotension, tachycardia or bradycardia, tachypnea or dyspnea, and continuously monitor the oxygen saturation. Myoclonic jerking or seizure activity may be present and can assist in diagnosis and management. Abnormal color or skin changes, such as bullae, flushing, cyanosis, or rash may also be of value. Certain odors are easily detected (ethanol, isopropanol, garlic, marijuana, and hydrocarbons), but others may be difficult or the clinician may be unable to smell (bitter almonds, carrots).
Attempt to identify the drug ingested. Obtain a history from the paramedics, police, relatives, or friends. Medics should bring the pills or medications found at the scene (near the patient or in the house). If possible, determine the date the prescription was filled, number of pills prescribed, instructions on the pill bottle, and number of pills missing. Although counting pills is not totally reliable, this information may give the clinician a rough estimate of the number of pills ingested. The name of the medication is helpful when requesting assistance from the Poison Center (1-800-222-1222) or researching further information in poison references. The poison center may also help to identify unknown pills with markings.
In each case of poisoning, the risk to the patient verses the benefit of decontamination should be considered. Decontamination (if warranted) should begin as soon as possible.
Depending on the patient’s condition, decontamination should begin as soon as possible. This may be achieved by several means:
Syrup of Ipecac (SOI) should no longer be used as a home treatment or in the ED because of its risk-to-benefit ratio. Circumstances are rare in which ipecac-induced emesis is an appropriate or desired method of gastric decontamination. In addition, there are potentially significant contraindications, adverse effects, and related problems associated with SOI use.
Activated Charcoal (AC) is recommended when the patient arrives within 60 minutes of the ingestion. AC may be administered alone or given as multiple doses in certain cases. AC may be effective when given later than 60 minutes post-ingestion for drugs that cause delayed gastric emptying or form concretions. AC adsorbs many drugs, but there is limited (and sometimes no) adsorption of alcohols, metals, caustics, or hydrocarbons. Usual doses are 25 to 100 grams in adults and adolescents; (PEDS) 25 to 50 grams in children aged 1 to 12 years; and 1 g/kg in infants up to 1 year old. Routine use of a cathartic, such as sorbitol, with AC is not recommended. There is no evidence that cathartics reduce drug absorption, and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances, and (occasionally) hypotension.
Cathartics such as magnesium citrate or magnesium sulfate have not been shown to alter morbidity or mortality in overdose patients. Because cathartics cause rapid transit, there is some theoretical benefit to their use. This rapid transit decreases the probability of further absorption. Use of cathartics alone is not recommended.
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Gastric lavage (GL) is recommended when the patient has ingested a potentially lethal amount of a drug and presents within 60 minutes of the ingestion.† There are several devices on the market to accomplish GL. The Easi-Lav allows rapid (less than 2 to 3 minutes) lavage once all tubes are connected. For best results and a more effective lavage, place a large (34 to 40 French) orogastric tube, remembering to protect the airway. Once placement in the stomach is confirmed, the patient should be placed on his or her left side head down (with about 30° of Trendelenburg positioning). This positioning should cause the stomach to be more bowl-like and prevent passage of the ingested substance/pills into the small intestines once lavage fluid is administered. Instill 250 to 300 mL aliquots of warmed tap water in adults (PEDS: or 10 mL/kg of NS in children). Each aliquot should be allowed to gravity drain or be pumped into the reservoir bag. During GL, the left upper quadrant abdomen should be periodically massaged. The end-point of GL is clear effluent. Typically, after lavage, 50 to 100 grams of AC is given and left in the stomach.
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Whole Bowel Irrigation (WBI) with a polyethylene glycol balanced electrolyte solution (Colyte®, Golytely®) is particularly useful when there is significant risk to patients with use of sustained release or enteric-coated formulations, substances not adsorbed by AC (ie, iron, lithium), or in drug packers. The solution may be drunk orally but is best administered via an NG tube because of the large quantity. Doses are 2 liters initially followed by 1.5 to 2 liters/hour in adults, (PEDS) 1000 milliliters/hour in children 6- to 12-years-old, and 500 milliliters/hour in children 9- months to 6-years-old. Continue WBI until rectal effluent is clear and there is no radiographic evidence of toxin in the GI tract.
Once the patient has been stabilized and the gut has been decontaminated, in a severely symptomatic patient, it may be necessary to remove already absorbed substance. To enhance elimination of an absorbed substance, the clinician may initiate antidote therapy, hemodialysis, hemoperfusion, continuous arterial-venous hemoperfusion or hemofiltration, or simply manipulate urine or serum pH manipulation (usually by alkalinization).
Use of the Poison Center (1-800-222-1222)
Remember that additional information and overdose management may be obtained from the Poison Center (1-800-222-1222). Poison centers are valuable resources and are staffed with trained personnel to provide helpful treatment advice. Poison centers are excellent starting places when more information is needed about the toxicology of a particular drug or substance.
References
- J Toxicol Clin Toxicol 1997 vol 1.
- Poisindex ®—MICROMEDEX® Healthcare Series Vol 126.
- American Academy of Clinical Toxicology and European Association of Poisons Centres and Clinical Toxicologists. Position Paper: Ipecac Syrup. J Toxicol Clin Toxicol. 2004;42(2):133-143.