Poisoning and Overdose Emergencies

Poisoning — core concepts

A poison is any substance that can harm the body, and a toxin is a poison produced by a living organism. Poisoning is most serious in three groups of patients: those who are already ill, the very young, and older adults. A poison reaches the body by one of four routes of entry. It can be ingested, inhaled, absorbed through unbroken skin, or injected through the skin by something that penetrates it.

Medical direction and poison control will want a particular set of facts, so gather them while you work. Find out exactly what the substance was, since the spelling matters and the container itself is worth bringing along when it is safe to do so; when the exposure happened; how much was taken; what has already been done for the patient; the patient's estimated weight, which is critical for pediatric dosing; and the effects the patient is showing now.

Activated charcoal

Activated charcoal works by adsorption: the poison binds to the surface of the charcoal rather than being taken up by the body. That makes it a way of preventing or reducing absorption, not an antidote, and it does nothing about poison that has already reached the bloodstream. It is used only rarely today, for specific overdoses, and always under medical direction, usually in consultation with poison control.

Several contraindications rule it out. Do not give activated charcoal to a patient who cannot swallow, who has an altered mental status, or who has ingested an acid or an alkali, and do not give it to a patient who is coughing violently, because of the risk of aspiration. Never force it on a patient who is refusing it.

Antidotes

Genuine antidotes are rare. Most of the treatment of poisoning consists of preventing further absorption and supporting the patient, not of giving a drug that undoes the poison. Naloxone is one of the exceptions: it reverses the central nervous system (CNS) and respiratory depression caused by opioids, and it has no effect at all in a patient who has taken no narcotic.

Acetaminophen poisoning deserves separate attention because its timing is deceptive. The toxic effects are delayed as the liver is progressively overwhelmed over a period of hours, and the antidote, N-acetylcysteine, works best when it is started within 8 to 10 hours of ingestion, becoming steadily less effective after that. The early symptoms, from about 4 to 12 hours, are deceptively mild: nausea and loss of appetite. Right upper quadrant (RUQ) pain and jaundice do not appear until 1 to 2 days later, by which point the best window for treatment has passed. For that reason, always suspect that acetaminophen may be involved in any overdose.

Inhaled poisons — carbon monoxide & smoke

Carbon monoxide (CO) is the most common inhaled poison. It is odorless, colorless and tasteless, and it prevents red blood cells from carrying oxygen normally. Its early signs are deceptively flu-like, with headache, dizziness and nausea, so the poisoning is easy to mistake for an ordinary illness. Pulse oximetry is no help and is actively misleading, because the readings it gives are falsely high; give oxygen regardless of a reassuring SpO2 whenever CO is suspected. The cherry-red skin of the older textbooks is a myth and is not typically seen.

Smoke inhalation combines thermal burns with chemical and irritant poisoning. The signs that the airway has been injured are coughing, a smoky or chemical odor to the breath, carbon residue in the mouth or nose, and singed nasal hairs. Give oxygen even when the SpO2 reads 100 percent, since carboxyhemoglobin reads the same as oxyhemoglobin on a standard pulse oximeter.

One inhalation hazard is directed at the rescuer as much as the patient. In a so-called detergent suicide, hydrogen sulfide gas is generated inside a small enclosed space, often a car, with the windows and doors taped shut and warning signs posted. Do not enter; call the appropriate hazmat team.

Absorbed & injected poisons

A poison that can be absorbed through the patient's skin can be absorbed through yours, which means decontamination may have to come before any contact, and a contaminated patient must never be brought into your ambulance untreated. Brush a dry powder off the skin. Irrigate a liquid, and anything in the eyes, with clean water for at least 20 minutes. Never attempt to neutralize an acid or an alkali with vinegar or baking soda: the reaction produces heat and damages the tissue further.

Poison control centers are available 24 hours a day, 7 days a week, anywhere in the country, at 1-800-222-1222.

Alcohol abuse

Never let an assumption of intoxication cost a patient the medical care he or she needs. Diabetes, epilepsy, head injury, high fever and hypoxia can all mimic intoxication, and each of them must be ruled out rather than assumed away. A patient can also be both things at once: intoxicated and having a myocardial infarction (MI), or intoxicated and hypoglycemic.

Withdrawal from alcohol is itself dangerous. It can produce seizures or delirium tremens (DTs), with sweating, trembling, anxiety and hallucinations, and untreated it can be fatal, so every patient with seizures or the DTs must be transported promptly. Remember as well that a patient under the influence of alcohol cannot make an informed refusal of care.

Substance abuse — five categories

Abused substances fall into five categories. The table below gives the effect each category produces and the drugs most often seen in it.

Table 25.1Substance abuse — five categories

The opioid category produces the most recognizable overdose. The classic opioid triad is a coma or depressed level of consciousness (LOC), pinpoint pupils and respiratory depression. Fentanyl mixed into heroin causes overdoses that are far more potent and far more rapid than heroin alone.

Signs by category & care

Each category has a field picture of its own, and recognizing it tells you what to expect next:

• Uppers: excitement, an increased pulse and rate of breathing, dilated pupils and sweating.
• Downers: a sluggish patient with poor coordination and a low pulse and rate of breathing.
• Opioids: a decreased pulse, a decreased rate and depth of breathing, pinpoint pupils, and a patient who is very sleepy.
• Hallucinogens: a fast pulse, dilated pupils, and a patient who sees or hears things that are not there.
• Volatile chemicals: a dazed patient, possibly in a coma, with swollen membranes in the nose and mouth.

The care is much the same whatever the substance. Begin with scene safety, watching for needles and weapons, and take Standard Precautions. Carry out the primary assessment and provide basic life support (BLS), supporting oxygenation and ventilation as the patient needs. If the patient is in respiratory failure and your protocol allows it, give naloxone intranasally. Perform a full physical exam and look for track marks, bearing in mind that their absence does not rule out injection drug use. Then transport, contact medical direction, and watch for seizures and vomiting on the way.

Many patients who have taken drugs seem calm at first and then turn violent, so stay alert throughout the call. Protect yourself from the substance as well as from the patient: many hallucinogens are absorbed through skin and mucous membranes, and you should never touch or taste any suspected illicit substance.