Acute Poisoning:

April 15, 2006

We live in a world of toxins and potential toxins, and thus we are often just a misstep away from a toxic exposure and its consequences. Even that which is meant to cure can kill. All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy; exposure to the wrong dose of a medication (whether accidental or not) remains a common form of toxic exposure.

Poisons have been a threat to the health and well-being of humankind for millennia. The word toxin is derived from the ancient Greek word toxikon, meaning "poison into which arrowheads are dipped" (in reference to Hercules' use of arrows dipped in the venom of the Hydra to slay the centaur Nessus).

Over the ages, poisons have played a considerable role in human affairs. Whether speaking of Socrates and his cup of hemlock, of those condemned to the "penalty of the peach" (administration of peach pits that contain amygdalin, which is metabolized to cyanide), or of the gas chamber (sulfuric acid mixed with sodium cyanide pellets in an enclosed area), poisons have been employed over the ages as an effective means of execution.

The use of toxins in a less than judicial role litters the course of human history as well. Arsenic, referred to as the poudre de succession (the powder of succession), helped ambitious princes secure thrones. Poisoning as a means of political gain is even evident in the recent dioxin poisoning of Victor Ushenko, the newly elected president of Ukraine. Poisons have also been employed throughout history as weapons of war and terror. Hannibal's sailors catapulted pots full of venomous snakes onto the decks of the opposing fleet. Members of the Aum Shinrikyo cult killed fellow countrymen after releasing sarin gas in a Matsumoto neighborhood and on Tokyo subway trains in 1994 and 1995, respectively. And certainly in the post-9/11 environment, chemicals employed as weapons of mass destruction and terror remain a concern of the ongoing national security debate.

But to focus solely on the more deceitful aspects of poisons is to miss the broader scope of their influence in the lives of our patients. We live in a world of toxins and potential toxins, and thus we are often just a misstep away from a toxic exposure and its consequences. Even that which is meant to cure can kill. As Paracelsus, the 16th-century German-Swiss physician and alchemist, said, all substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy. The truth in his words echoes today: exposure to the wrong dose of a medication (whether accidental or not) remains a common form of toxic exposure.

Medications are only one example of potential toxins in the home. Household cleaners and other chemicals are common sources of intentional and unintentional poisoning. Chemicals used to improve our lives or environment--such as herbicides, pesticides, fertilizers, and hydrocarbon fuels used in agriculture or industry--are potentially harmful if improperly used.

From the massive toxic gas release from Mount Vesuvius in ad 79 to the release of methyl isocyanate gas in one of the greatest civilian toxic disasters in modern history in Bhopal, India, in 1984, natural or industrial toxic releases remain a potential threat to health.1-4 Given the ubiquitous nature of potential poisons, exposure to a toxin should be included in the differential diagnosis of patients with unexplained illnesses or unusual presentations.

EPIDEMIOLOGY

The American Association of Poison Control Centers--whose 62 participating poison centers service the population of the 50 states and the District of Columbia--has compiled poisoning data since 1983 and created the Toxic Exposure Surveillance System (TESS). According to the TESS 2004 annual report, US poison centers reported a total of 2,438,644 human exposure cases. Sixty-five percent of reported exposures were in children; of those pediatric exposures, 51.3% of all exposures occurred in children younger than 6 years. Patients younger than 13 years were predominantly male. However, this gender predominance was reversed in teenagers and adults.

Most toxic exposures were unintentional (84.1%) and involved a single toxic substance (91.4%). Most exposures occurred at the patient's residence or another residence (89.7% and 3%, respectively). Ingestions (76.8%) were by far the most common route of exposure; dermal exposure and inhalation ranked second and third (7.5% and 5.9%, respectively).

Most patients were treated at the site of exposure and received only poison center support. Some were treated and subsequently released from a health care facility (11.6%). Only 6.8% were admitted to a health care facility for further examination and treatment.5

THE STARTING POINT: A GOOD HISTORY

You will have taken the first step in correctly diagnosing a toxicologic illness or injury by entertaining that possibility in your differential diagnosis. A good history--one that concentrates on uncovering possible toxic exposure--provides you with the means to zero in on the offending agent or agents and focus your physical examination.

Start with the usual: question the patient and/or others involved in the patient's care to develop a complete understanding of the constellation of acute complaints. Ask specifically about any temporal associations with these complaints. The goal is to establish a timeline of your patient's complaints.

Next, determine whether anyone else in the patient's family, coworkers, or other regular contacts is experiencing the same or similar symptoms.

Medication history

  • Obtain a list of the patient's medications, both prescription and over-the-counter.

  • What vitamins or nutritional supplements does the patient take?

  • Does the patient take any herbal or nontraditional remedies?

  • Do not stop with the patient's medications: who else's medications are reasonably available to the patient in his or her home environment?

  • Could the patient be ingesting (inadvertently or intentionally) a family member's medications, supplements, or remedies?

Diet history

  • Does the patient consume any unusual foods that might have a toxic effect, either acutely or of a more cumulative nature?

  • Does the patient consume any natural or organic foodstuffs?

  • Is there any reason to suspect that the patient may be consuming any food that may be contaminated with herbicides, pesticides, or other toxic chemicals?

Residence history

  • What are the particulars of the patient's home? The age and type of structure can provide valuable clues about materials that might reasonably be found in that residence. For example, was the patient's home built before the 1978 US ban on lead in new paints? If so, the home has a greater likelihood of containing lead-based paints.6

  • What type of heating and cooling devices are used in the home?

  • Does the home have an old furnace in disrepair that potentially leaks carbon monoxide throughout the house?

  • What household chemicals are stored or used in the house or outlying structures?

  • Does the patient have access to these stored chemicals?

Water source history

  • Is the patient's home supplied by a city water system or by a separate, well-based system?

  • If the source is a large city water system, is there reason to suspect contamination--perhaps with hydrocarbons or other industrial chemicals?

  • If well water is the source, is there reason to suspect agricultural runoff, herbicides, or pesticides as possible contamination?

Work history

  • What is the nature of the patient's employment, and how long has he been employed at that job?

  • What material(s) does the patient handle during his daily work?

  • Are there any materials or procedures that require specific safety precautions or equipment?

  • Does the patient operate in any confined or poorly ventilated spaces throughout the day?

  • Is there any ongoing, or has there been any recent, construction or repairs to the work environment?

  • Are there centers of agriculture or industry nearby?

Hobbies

  • Does the patient engage in any hobbies or leisure activities that might present an increased risk of toxic exposure? (For example, does the patient use an acetylene torch in a poorly ventilated toolshed to strip paint from wood furniture and materials pursuant to his hobby of refinishing antiques?)

Our patients lead interesting and complex lives. When you suspect a possible toxic cause for their presenting complaints, you must try to develop a comprehensive picture of the world in which they live. A thorough and detailed history that explores all potential sources of toxic exposures is perhaps the most important element of making an accurate diagnosis of poisoning.

THE PHYSICAL EXAMINATION

A head-to-toe examination should be performed on every patient who presents with multiple acute complaints--especially those that are vague or nonfocal. Focus on vital signs and organ systems often affected by potential toxins in an effort to assess your patient for a toxicologic syndrome, or "toxidrome" (listed in the Table).

  • Look at your patient globally. Does he appear acutely ill or uncomfortable? Does the general appearance fit with your review of vital signs? Is he especially warm or cool?

  • Do the vital signs represent a pattern consistent with any common toxidrome (anticholinergic, sympathomimetic, or other)?

  • Dermatologic findings (including mucous membranes): Is the patient dry or diaphoretic? Flushed or pale? Is he cyanotic? Are there any rashes or discrete lesions evident? Is the patient salivating? Lacrimating? Is rhinorrhea present?

  • Neurologic findings: Is there altered mental status, nystagmus, or myoclonus? Is there hyper- or hyporeflexia?

  • Ophthalmologic signs: Is there miosis or mydriasis? Are the pupils equal, round, and reactive to light?

  • GI signs: Are bowel sounds hyperactive or reduced? Is there evidence of incontinence?

  • Genitourinary signs: Can you palpate the bladder (consistent with urinary retention)? Is there evidence of incontinence?

Table - Manifestations of common toxidromes

IntoxicantsMental statusHeart rateBlood pressureRespiration rate

Anticholinergic agents*AlteredIncreasedVariableVariable

Cholinergic agentsAlteredVariableVariableIncreased or unchanged

Adrenergic agonistsStimulatedIncreasedIncreasedIncreased

Sedative-hypnotics (including ethanol)DepressedDecreasedDecreasedDecreased

Withdrawal from sedative-hypnotic agents(including ethanol)AlteredIncreasedIncreasedIncreased

OpioidsDepressedDecreasedDecreasedDecreased

Withdrawal from opioidsNormalIncreasedIncreasedUnchanged

(Table Continued)    
 
IntoxicantsTemperatureDiaphoresisPeristalsisPupil size

Anticholinergic agents*IncreasedDecreasedDecreasedIncreased