Toxicologic and Environmental Emergencies

Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5–37.5ºC (97.7–99.5ºF). Although the reasons are unknown, it has been hypothesized that a narrow temperature range is maintained for the metabolic rate needed for the functioning and optimization of cellular processes. Regulation of the core temperature is one of the most critical functions of the nervous system and is achieved by physiologic and behavioral feedback and feed-forward mechanisms that are mainly regulated by the hypothalamus. Any change in body temperature or environmental temperature triggers responses that lead to the quick and efficient resetting of homeostasis.

Injuries due to cold weather are common among children and athletes who are involved in sports played in cold conditions. There are multiple cold-related injuries, with frostbite being the most common. Frostbite is a direct freezing injury to the peripheral tissues and occurs when the skin temperature drops below 0℃ (32°F). Common sites of frostbite include the nose, ears, fingers, and toes. Clinical signs include skin pallor, anesthesia, blistering, and tissue necrosis. The main treatment is rapid rewarming.

Hydrogen cyanide is an extremely poisonous, colorless, flammable liquid used in multiple industries and includes rubber, plastic, and household paints. Exposure to cyanide can occur via inhalation, dermal contact, or intestinal ingestion. Cyanide poisoning is a common complication of closed-space fires since cyanide is a byproduct of plastics combustion. Symptoms develop within seconds to minutes and involve cardiovascular, respiratory, and neurological changes. Management includes sodium thiosulfate, nitrites, and hydroxocobalamin. If not recognized and treated promptly, cyanide poisoning is frequently lethal.

A toxidrome is a group of clinical signs and symptoms associated with a toxic ingestion or exposure. There are 5 traditional toxidromes: anticholinergic, cholinergic, opioid, sympathomimetic, and sedative-hypnotic. Toxidromes often arise from ingestion of overdose amounts, accumulation of medications with resultant elevated serum levels, adverse drug reactions, or interactions between 2 or more medications. Rapid recognition of a toxidrome can help determine the specific poison or class of toxin that was ingested. On presentation of a suspected toxidrome, appropriate airway, breathing, and circulation assessment is initiated. Decontamination is performed, and the patient is stabilized. Diagnosis is accomplished with clinical findings based on medication and exposure history, vital signs, mental status, and physical examination. Testing generally includes toxicology and drug levels, electrolytes, and ECG. Management consists of supportive care and antidote administration if indicated.

Herbicides are chemical substances used to kill or control the growth of unwanted plants. Important herbicides that can affect humans include paraquat, Agent Orange, glyphosate, and organophosphates. Different types of herbicides result in different clinical manifestations and have various toxicity levels. Paraquat ingestion is associated with multiorgan damage within a few hours and is fatal in large amounts. In contrast, glyphosate typically has low toxicity, but if a significant volume is ingested, serious adverse effects occur. Organophosphates, which are broadly used as pesticides, produce a cholinergic toxidrome. Agent Orange, containing 2,3,7,8-tetrachlorodibenzo-p-dioxin, a human carcinogen, carries both short-term (e.g., chloracne, liver toxicity) and long-term (e.g., cancers) complications. Exposure can be dermal or via inhalation or ingestion. In general, early detection is important to prevent serious sequelae. Initial management consists of stabilizing the patient and decontamination. An antidote is given, if available. Treatment of herbicide poisoning revolves around supportive care that depends on the involved organ system.

An antidote is a substance that counteracts poisoning or toxicity. Substances that can cause poisoning include heavy metals (from occupation, treatments, or diet), alcohols, environmental toxins, and medications. An increase in the concentration of these substances to toxic levels can occur accidentally or intentionally, resulting in both acute and chronic presentations. Some substances can be detected using specific laboratory tests, whereas the detection of others relies on nonspecific findings. Thus, it is important to recognize substance poisoning by history, individual risk factors, and physical examination. Antidotes along with supportive care and monitoring are part of the management.

Acetaminophen is an over-the-counter nonopioid analgesic and antipyretic medication and the most commonly used analgesic worldwide. Despite the widespread use of acetaminophen, its mechanism of action is not entirely understood. However, acetaminophen is believed to exert its effects through indirect and reversible inhibition of cyclooxygenase (COX)-1 and COX-2. The effects are generally limited to the CNS. Acetaminophen is primarily metabolized by the liver; therefore, an overdose can lead to life-threatening hepatotoxicity. In adults, limiting the total acetaminophen dose (from all sources and routes) to < 4000 mg/day is highly recommended. Contraindications to acetaminophen use include hypersensitivity, severe hepatic impairment, or severe active hepatic disease.

Acetaminophen (APAP) is an over-the-counter nonopioid analgesic and antipyretic medication. Acetaminophen is the most commonly used analgesic worldwide. Acetaminophen overdose is also one of the most common causes of medication poisoning and death. Because APAP is primarily metabolized by the liver, overdose can lead to life threatening hepatotoxicity. In adults, limitation of total APAP dose (from all sources and routes) to < 4,000 mg per day is recommended. During evaluation, a thorough history and measurement of serum APAP are important, as the initial clinical stages of APAP overdose can be nonspecific. Management of overdose includes drug serum concentration, stabilization, decontamination, and administration of N-acetylcysteine (NAC). Use of NAC within 8 hours of ingestion is associated with good case outcomes. Without treatment, however, cases are at significant risk of severe hepatotoxicity and potentially death.

Heatstroke is an illness characterized as a core body temperature exceeding 40°C (104°F) with accompanying neurological symptoms including ataxia, seizures, and/or delirium. Heatstroke is usually due to the body’s inability to regulate its temperature when challenged with an elevated heat load. The illness can be classified as exertional or non-exertional. Management involves emergent stabilization, cooling, and supportive care. Early recognition and intervention are important to prevent complications or organ failure.

A burn is a type of injury to the skin and deeper tissues caused by exposure to heat, electricity, chemicals, friction, or radiation. Burns are classified according to their depth as superficial (1st-degree), partial-thickness (2nd-degree), full-thickness (3rd-degree), and 4th-degree burns. Management is greatly dependent on the extent of surface area affected and the depth of the burns. Management involves fluid resuscitation, adequate analgesia, and appropriate wound care with the goal of preventing opportunistic infection.

Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Certain populations may be more vulnerable to accidental hypothermia, including extremes of age, homeless, mentally ill, and alcohol and drug abusers. Evaluation should include assessment for associated trauma and contributing medical conditions. Management involves rewarming the patient by different methods based on the severity of the hypothermia.

The airway, breathing, and circulation, disability and exposure (ABCDE) assessment is the mainstay management approach used in managing critically ill patients. The ABCDEs are the essential 1st steps to perform in many situations including unresponsive patients, cardiac arrests, and critical medical or trauma patients. For the trauma patient, ABCDE is included in the primary survey, the initial evaluation, and management of injuries.

Drowning occurs due to respiratory impairment from submersion or immersion in a liquid medium. Aspiration of water leads to hypoxemia, which affects all organ systems, resulting in respiratory insufficiency and acute respiratory distress syndrome (ARDS), cardiac arrhythmias, and neuronal damage. The management of drowning focuses initially on ventilatory support followed by cardiopulmonary resuscitation. As drowning is most often preventable, prevention is the focus of most interventions.

Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. The most common symptoms include tachycardia, tachypnea, hypotension, altered mentation, and oliguria. Treatment measures vary depending on the suspected cause of shock and may include mechanical ventilation, IV crystalloids, vasopressors, and blood transfusion.