CHAPTER 30. Toxicologic Emergencies
Reneé Semonin Holleran
Competencies
1. Identify the common sources of poisoning.
2. Describe the care of the poisoned patient during transport.
3. Name three antidotes for specific poisons.
Each year, more than 2 million human poison exposures are reported to the American Association of Poison Control Centers (AAPCC). The AAPCC compiles the Toxic Exposure Surveillance System (TESS), the largest database of information about toxic exposures in the United States. More than 90% of these exposures occur in the victim’s home. Others occur in locations such as the workplace, healthcare facilities, schools, and public areas. 5 More than half of the poisonings are found in children less than 6 years of age. Most poisonings continue to be unintentional. Intentional poisonings are generally related to suicide, misuse, and abuse. The age group with the most fatalities related to poisoning was the 20-year-old to 59-year-old age group. 5
The human environment contains natural and manufactured toxins from plants, animals, chemicals, drugs, and chemotherapeutic agents. A new phenomenon that has been increasing over the past few decades is the nonmedical use of prescriptive medications, which has led to an increase in poisonings from medications that include sedatives, tranquilizers, opioids, and stimulants. 15
Although multiple substances and various sources of toxins and poisons exist, only a limited number of antidotes are available. Table 30-1 lists most of the available antidotes that may be useful in the management of the poisoned patient.
| Toxin | Antidote |
|---|---|
| Opiates | Naloxone |
| Carbon monoxide | Oxygen |
| Cyanide | Amyl nitrate |
| Sodium nitrate | |
| Sodium thiosulfate | |
| Anticholinesterase | Atropine |
| Organophosphates | |
| Carbamates | |
| Methemoglobinemic agents | Methylene blue |
| Nitrates | |
| Chlorates | |
| Nitrobenzene | |
| Ethylene glycol | Ethanol |
| Acetaminophen | N-acetylcysteine |
| Heavy metals | BAL |
| Disodium edetate | |
| Penicillamine | |
| Iron | Deferoxamine |
| Anticholinergics | Physostigmine |
| Diphenhydramine | |
| Benzotropine | |
| Anticoagulants | |
| Coumadin | |
| Heparin | Vitamin K |
| Cardiac medications | Protamine |
| Beta-adrenergic blockers | |
| Calcium-channel blockers | Glucagon |
| Digoxin | Calcium |
| Tricyclic antidepressants | Digoxin Fab antibodies |
| Sodium bicarbonate |
The most important concept in the care of the patient who has been poisoned is supportive care. In addition to maintenance of the patient’s airway, breathing, and circulation, the exposure to the toxin must be quickly stopped to prevent further harm to the patient. Some toxins can cause injury to caregivers, so appropriate decontamination must be accomplished before transport. Safety must be the number one concern when transporting a potentially poisoned patient. 1,21
Maloney and Pakiela14 recently published a study that reviewed the air medical transport of patients with acute toxicologic emergencies. The three most common emergencies were carbon monoxide, acetaminophen, and antidepressant poisonings. The primary intervention provided by the transport team was endotracheal intubation. 14
The purpose of this chapter is to discuss the general management of the poisoned patient, identify the pathophysiology of selected drugs, and describe the care of the poisoned patient during transport.
INTENTIONAL AND UNINTENTIONAL POISONING
Ingestion of or exposure to a toxic substance may be either intentional or unintentional. Determination of why the patient has become poisoned is important because it could make a difference in the care of the patient. A patient who intentionally took a lethal amount of a drug should be considered a potential safety risk by the transport team. 1
Sources of unintentional exposure include therapeutic error (too much medication taken), bites and stings, environmental exposures, and food poisoning. Intentional poison exposures usually result from suicide attempts, abuse, and intentional misuse of medications.
The word poisoning denotes a toxic exposure that can be intentional, unintentional, or unknown to the patient. A patient or family member may have misread a label, taken too much of a drug, or accidentally become poisoned. A child may climb up and get into a medicine cabinet, ingest a bottle of aspirin, and be unintentionally poisoned. Criminals do not often use poisonous substances as a method of injuring or killing. 20
An intentional overmedication or ingestion of a toxic substance is considered an overdose2,20,21,25 Poisoning generally occurs in the pediatric population. Patients who have overdosed or intentionally poisoned themselves are usually 12 years or older, although some cases suggest that children 5 years and older should be evaluated for intentional ingestion. 7,8
The distinction between accidental and intentional toxic exposure is important. If the patient is suicidal, the transport team should take additional precautions to ensure a safe environment for the crew and the patient during transport.
GENERAL MANAGEMENT OF THE POISONED PATIENT
The initial management of any poisoned patient includes establishment of a patent airway, ventilation, and maintenance of adequate circulation. The transport team should always ensure that whatever has poisoned the patient may not potentially cause harm to the team. Further evaluation consists of a detailed history about the event that led to the poisoning, a thorough physical examination, administration of antidotes as indicated, and transport to an appropriate healthcare facility for definitive care. The patient’s family should be a part of the initial care because they may be able to offer important information about the incident. The emotional support of the patient, particularly a patient who has attempted suicide, should be included in the planning of care.
Initial Management
Shannon and colleagues21 state that the initial approach to the management of a poisoned patient includes: stabilization; laboratory assessment; decontamination of the gastrointestinal tract, skin, or eyes; administration of an antidote if indicated; elimination enhancement of the toxin; and observation and disposition.
As with any other critically ill or injured patient, the ABCDEs (airway, breathing, circulation, disability, and exposure) take initial precedence. One exception in the case of the poisoned patient is the need to remove the victim from a toxic environment or toxic source before the ABCDEs can be assessed. If the patient has been sprayed with a toxic substance or the creature that caused envenomation is still in the immediate vicinity, the environment must be controlled and made safe before patient management so that the healthcare providers are not injured or poisoned.
Many toxins and poisons alter mental status and therefore may compromise the airway. Protection of the airway is particularly important if the toxin is to be removed via gastric lavage. During resuscitation, contamination of the rescuer with the toxic substance should always be avoided. Endotracheal or nasotracheal intubation is the preferred method of protecting the airway and preventing the possibility of aspiration.
Alterations in the patient’s circulatory status may be profound and life threatening. Intravenous access and appropriate fluid resuscitation should be initiated. Blood pressure may need to be supported with vasoactive agents.
Depending on the type of poison or toxic exposure, decontamination may be needed before the patient can be transported. Generally, decontamination of the patient can be accomplished with soap and water. However, some toxins require specific decontaminates. The transport team must know and follow appropriate procedures to protect both themselves and the patient. 12,19,20
Assessment
History
The history of the toxic exposure provides a vital method of identification of the type of substance responsible for the patient’s symptoms. Poisoning or an overdose should be suspected in the following types of patients: a psychiatric patient, a trauma victim, a comatose patient with an unknown cause of coma, a young person with a life-threatening arrhythmia of undetermined origin, a patient rescued from a fire, a child with unexplained lethargy, and any person with suspicious or unusual behavior. 10,25 The history should include the type of substance or suspected substance that was taken, the exposure route, the time of the exposure, and the size or dosage of the exposure.
The patient may be exposed to a toxin through a number of routes. These include:
▪ Ingestion
▪ Dermal or skin contact
▪ Inhalation
▪ Ocular exposure
▪ Bite or sting
▪ Parenteral
▪ Aspiration
If a thorough history cannot be obtained, the environment in which the patient was found should be explored for clues to the cause of the poisoning. The transport team should look for bottles, containers, drug paraphernalia, animals, or items that may provide additional information about a suspected or unknown toxic substance. These items should be transported with the patient. Identification of witnesses to the event can add more information concerning what may have caused the poisoning or toxic exposure. 10,20
Medical history, such as allergic reactions, previous surgeries, and past hospitalizations, should be noted. When possible, assessment of whether the patient has attempted suicide in the past is important.
Symptoms of Poisoning and Toxic Exposures
Certain symptoms without a clear cause may suggest poisoning or overdose. Severe poisoning symptoms include coma, cardiac arrhythmia, metabolic acidosis, seizures, and gastrointestinal (GI) disturbances. 1.2.3. and 4.10,20 Many disease states may mimic overdose and should be considered in the differential diagnoses. Head injuries, encephalitis, meningitis, metabolic disturbances, and psychiatric diseases are easily mistaken for poisoning.
Physical Examination
The physical examination of a poisoned patient should include assessment of general appearance and pulmonary, cardiovascular, abdominal, and neurologic systems. The information obtained from physical examination not only helps determine the source of the toxic substance but also provides baseline data to follow the effects of the toxic substance and the particular interventions that have been initiated.
Baseline assessment data are particularly important in the determination of any changes in the patient’s condition during transport. During transport, the toxic effects of the substance should be considered, as should the success or failure of initial treatments on the patient’s condition. 13
The physical appearance of the patient may give a clue to the type of poison or overdose the patient has taken. The presence of needle tracks, burns, bruises, lacerations, cutaneous bullae, erythema, petechiae, cyanosis, flushed skin, or bite marks may provide information to help diagnose the poison or toxic exposure. 4,8.9. and 10.20 Breath odors may suggest possible poisoning or help rule it out for another cause. For example, the smell of oil of wintergreen can indicate salicylate poisoning. Table 30-2 lists odors associated with certain poisonings. 8,20
| Odor | Possible Poison |
|---|---|
| Sweet | Placidyl |
| Acetone | |
| Chloroform | |
| Bitter almond | Cyanide |
| Pear | Chloral hydrate |
| Garlic | Arsenic |
| Wintergreen | Methylsalicylate |
Respiratory rate and pattern are also important assessment parameters. Auscultation of breath sounds is included in this assessment. Many toxins can cause respiratory arrest and impair the airway, with the potential for aspiration.
Assessment of the level of consciousness of the poisoned patient is secondary only to the patient’s respiratory (and cardiovascular) assessments and may reveal a spectrum of altered sensorium. Hyperactivity, psychosis, somnolence, or coma may be manifested. Generalized seizures have been reported in many different cases of poisoning or overdose. Level of consciousness, pupillary response, motor and sensory function, and vital signs should also be included in the assessment.
An assessment of the patient’s level of consciousness should go beyond orientation to person, place, and time. The patient’s interaction with the environment can yield useful information about the patient’s level of consciousness. Many drugs and toxic substances cause visual, auditory, or other sensory hallucinations and alter the patient’s personality.
Pupil size, shape, and reaction are parts of the neurologic assessment. Constricted or dilated pupils may indicate drug or treatment effects. Motor and sensory functions are usually assessed together and may vary from normal activity to no movement at all. Seizure activity is not an uncommon complication from toxins and should be appropriately documented and treated.
The presence or possibility of an altered mental status occurring during transport necessitates the use of appropriate safety measures. Restraints and, in some cases, chemical restraint may be warranted to ensure safe transport. 1,13
Cardiac monitoring should be performed and blood pressure and pulse quality frequently checked during transport. Hypotension, premature ventricular contractions, prolonged QT intervals, and a widened QRS complex are examples of some of the cardiac arrhythmia that may occur because of cardiac toxicity related to some poisonings.
Certain toxic substances cause GI disturbances such as nausea, vomiting, and severe abdominal pain. Iron, lithium, mercury, phosphorus, arsenic, mushrooms, organophosphates, and fluoride are examples of toxic substances that can cause GI disturbances. Phosphorus poisoning can cause luminescent vomit and flatus. 20 A gastric tube should be inserted before transport to prevent aspiration, especially if the patient has been given activated charcoal.
Laboratory Studies
Many substances responsible for adverse reactions, intoxications, and poisoning are difficult to identify. Serum levels are not reflective of tissue concentration or receptor interactions; therefore, levels of specific toxins may be incongruous with clinical manifestations. 20
Laboratory evaluations such as complete blood count, electrolytes, whole blood glucose, liver function tests, and coagulation studies are frequently helpful. Many toxins are associated with leukocytosis or electrolyte alterations. An example is the hypokalemia associated with theophylline toxicity. Arterial blood gases are beneficial in determination of acidosis or alkalosis. Acidosis can be appreciated in tricyclic poisoning or late methanol or ethylene glycol poisoning, whereas alkalosis occurs in early salicylate intoxication. 8,20
The treatment of poisoning with some drugs such as acetaminophen and aspirin necessitates determination of baseline serum levels and a repeat of these levels 3 to 6 hours after ingestion. Levels of some drugs may have to be monitored for several days after ingestion to ensure that they have been eliminated. Any blood, gastric contents, and urine that have been obtained for toxic analysis should accompany the patient for transport.
Removal, Elimination, or Disruption of the Toxin
Ingestion, parenteral injection, ocular contamination, dermal exposure, inhalation, and envenomation are the major routes of intoxication. 19,20 The method of exposure must be established so that a method of removal or interruption can be chosen. Methods for reversal of the clinical effects of poisons include the use of antidotes, antivenin, supportive therapy, forced diuresis, charcoal, cathartics, whole bowel irrigation, hemoperfusion, and dialysis. 8,20 The most common method of removal is gastric lavage followed by administration of charcoal.
Ion-trapping diuresis is accomplished with alkalinization and acidification of the poisoned patient’s urine. For alkalinization of urine, sodium bicarbonate is added to intravenous (IV) solution, and fluids are administered to yield a urine pH of 7.5. The patient must be monitored closely for complications from fluid and electrolyte imbalances. 20
If the toxin has been inhaled, the individual should be removed from the source of the exposure. Administration of oxygen may be of use, particularly for the patient who has sustained carbon monoxide (CO) poisoning.
Contact poisons or toxins may enter the body through the skin, eyes, or mucous membranes. Removing the patient from the toxic environment, taking off the patient’s clothes, and cleansing the affected area are the most important steps in the initial removal of the poison or toxic substance. Use of the correct irrigation fluid or fluids is important to prevent further injury to the patient. Attention also must be given to the proper disposal of the contaminated fluid and materials to prevent poisoning of the healthcare providers and the surrounding environment.
Antivenin administration, hemoperfusion, and dialysis should all be performed under the direction of a trained toxicologist or other healthcare professional acquainted with each procedure. Administration of antivenin in the prehospital environment is not recommended because of the potential of severe complications that may not be effectively managed. 6,17,18
Supportive and Emotional Care of the Poisoned Patient
As noted previously, specific antidotes are limited compared with the numbers of the poisons and toxic substances disseminated in the environment. Frequently, supportive care directed at prevention of complications from the poison or toxic substance is the most that can be done for the patient. 20 Part of this supportive care may be the transport of the patient to a specific center with additional methods of care for the patient. Supportive care is based on the previous discussion of initial management, physical examination, and removal, elimination, or interruption of the toxic sequence.
The emotional care of the poisoned patient can be difficult. If the poisoning is intentional, the motive must be quickly discovered so that proper psychiatric and social care can be rendered. All procedures should be explained to the patient and a nonjudgmental attitude imparted when care is provided. If possible, the patient’s family should be given some time with the patient before transport.
Protection of the patient from complications and respect for the patient as a human are important components of the care of the poisoned patient. E.J. Daniels7 noted how insensitive nursing care can affect the poisoned patient:
“The curtains hadn’t been completely closed, and anyone and everyone walking by peered in, adding to my humiliation. I tried staring at everything but Brenda and the gaggy network of tubes in an attempt to keep my mind off the nauseating trauma. Alright. I have to put some medications down you. Try not to gag on it, because you really need it, keep this down. I’d never heard of any medicine that was pitch black! I felt like she had been flushing me out for hours. She hooked up a huge syringe to the end of the tube down inside of me. The thought of the tar going down my throat into my stomach was more repulsive than the gurgling sensation of lavage.”7
Safety Issues in the Transport of the Poisoned Patient
Safety is one of the most important issues to be addressed in the care of a poisoned patient during transport. Many intoxicants can cause hallucinations or violent behavior. Physical or chemical restraint to ensure safe transport should be a consideration when preparing the patient for transport.
Both physical and chemical (i.e., medications) restraints provide a means of safe control of the patient for transport. Decreasing excessive stimulation during transport with ear protectors may also reduce the possibility of dangerous or threatening patient behavior during transport. If neuromuscular blocking agents are used, adequate analgesia and sedation must be provided during transport. 1
Summary
The care of the poisoned patient who needs transport begins with management of the patient’s airway and ventilation and maintenance of the cardiovascular system. Physical examination, including the patient’s general appearance; assessment of the neurologic, respiratory, cardiovascular, and gastrointestinal systems; removal, elimination, or interruption of the toxic sequence; and supportive and emotional care are other important components of care of the poisoned patient.
Preparation for the transport of the poisoned patient includes decontamination; sampling of the toxic substance; transfer of laboratory work such as blood, urine, or vomitus; and informing the family of the transport destination.
Box 30-1 summarizes the care for the poisoned patient. The care of the poisoned patient must be approached in an organized manner to provide supportive care and prevent complications.
BOX 30-1
Care of the Poisoned Patient by the Transport Team
1. Provide basic and advanced life support after ensuring that the environment is safe for the transport team.
2. Remove the patient from the toxic environment.
3. When indicated, decontaminate the patient by removing clothing and washing off toxin.
4. Administer appropriate antidote when indicated.
5. Assess respiratory, neurologic, and cardiovascular status frequently.
6. Document or obtain baseline data.
7. Ensure the patient and transport team’s safety in transport with the use of chemical or physical restraints. With use of chemical restraints, do not forget about analgesia and sedation.
8. Explain to the patient and family what is happening.
9. Transfer appropriate records and specimens.
10. Inform the patient’s family of the patient’s destination.
PHARMACOLOGIC PROPERTIES OF DRUGS
Therapeutic dose responses are affected by multiple variables including the rate of absorption, distribution, binding or localization in tissues, inactivation, and excretion. The rate of absorption is defined as the time needed for the chemotherapeutic agent to cross the enterovascular barriers and circulate in the cardiovascular system. Agents dissolved in solution are absorbed more rapidly than those in solid forms. Timed-release enteric-coated products are engineered to greatly decrease the absorption rate. Medications given in higher concentration are absorbed more rapidly.
Gastric pH may deactivate or precipitate a drug. Areas of increased vascularity, such as the vagina or rectum, tend to absorb agents more rapidly. Topical exposure or inhalation of poisons reaches toxic levels quickly because of the large surface areas exposed to the intoxicants.
Most drugs are administered orally. Sites of absorption include the oral mucous membranes, stomach, duodenum, and small intestine. Sublingual administration usually promotes quick dissolution and rapid absorption. Absorption in the stomach is a passive process mediated by dissolution and diffusion. The nonionized form of a dissolved medication passes the mucosal barriers and enters the vascular compartment. Most drugs are either weak bases or weak acids. Gastric pH affects both dissolution and diffusion. Weak acids, such as salicylates and barbiturates, are predominantly nonionized in a strongly acidic environment; therefore, they are readily absorbed. Weak bases are in an ionized form in the stomach and are poorly absorbed. The intestinal pH. is less acidic than the stomach pH (pH, 5.3). Weak bases are readily absorbed, but weak acids cross the mucosal barrier less readily. In addition, the gastric mucosa is a lipoid membrane, which absorbs lipid-soluble substances, such as alcohol, rapidly. Factors that change gastric emptying time also alter the rate of absorption of a drug. IV injection is the most immediate and consistent blood concentration for any drug. After injection, a redistribution phase may significantly decrease the blood level of the drug. Absorption of medication given subcutaneously or intramuscularly depends on the site of injection, the solubility of the drug, and the vascularity of the injection area.
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