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THE POISONED OR OVERDOSED PATIENT

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Title: THE POISONED OR OVERDOSED PATIENT


1
THE POISONED OR OVERDOSED PATIENT
  • Poisonings and drug overdoses can cause quick
    physical and mental changes in a person.
  • Bystanders usually are the ones who must initiate
    care and call a poison control center or
    emergency number.
  • Commonly observed poisonings or drug overdoses
    are caused by (but certainly not limited to)
    acetaminophen, amphetamines, benzodiazepines,
    carbon monoxide, cocaine, opiates, salicylates,
    and tricyclic antidepressants.

2
Poisoning
  • The most common routes of exposure in poisoning
    are inhalation, ingestion, and injection.
  • Toxic chemical reactions compromise
    cardiovascular, respiratory, central nervous,
    hepatic, gastrointestinal (GI), and renal
    systems.
  • Most exposures to toxic fumes ????? occur in the
    home.
  • Poisoning may result from the improper mixing of
    household cleaning products or malfunctioning
    household appliances that release carbon
    monoxide.
  • Burning wood, gas, oil, coal, or kerosene also
    produces carbon monoxide.
  • Carbon monoxide gas is colorless, odorless,
    tasteless, and nonirritating, which makes it
    especially dangerous.

3
  • The ingestion of poisons and toxins occurs in
    various settings and in different age groups.
  • Poisoning in the home usually occurs when
    children ingest household cleaners or medicines.
  • Improper storage of these items contributes to
    such accidents.
  • Plants, pesticides, and paint products are also
    potential household poisons.
  • Because of mental or visual impairment,
    illiteracy, or a language barrier, older adults
    may ingest incorrect amounts of medications.
  • In addition, poisoning may occur in the health
    care environment when medications are
    administered improperly.

4
  • Similarly, poisoning can also occur in the health
    care
  • environment when a medication normally given
    only by the subcutaneous or intramuscular route
    is given intravenously, or when the incorrect
    medication is injected.
  • Poisoning by injection can also occur in the
    setting of substance abuse, as when a heroin
    addict inadvertently (without knowledge or
    intention) injects bleach (usually chlorine, used
    to whiten pulp) or too much heroin.

5
Substance Abuse and Overdose
  • Admission of most poisoned patients to a critical
    care unit is for an intentional or suspected
    suicidal overdose.
  • As part of their histories, these patients
    frequently have mental illness, substance abuse
    problems, or both.
  • Often, withdrawal symptoms and syndromes
    complicate the assessment of potential
    toxidromes.
  • A toxidrome is a group of signs and symptoms
    (syndrome) associated with overdose or exposure
    to a particular category of drugs and toxins.

6
  • Commonly abused substances are nicotine, alcohol,
    heroin, marijuana, narcotic analgesics,
    amphetamines, benzodiazepines, and cocaine.
  • Some children and adolescents turn to common
    household substances because they are readily
    available.
  • People who attempt to manage stress through
    substance abuse require a comprehensive treatment
    program to address their coping and adaptation
    problems.

7
ASSESSMENT
  • A health care facilitys systematic approach to
    the assessment of the poisoned or overdosed
    patient includes performing triage, obtaining the
    patients history, performing a physical
    examination, and conducting laboratory studies.

8
  • Triage (A process for sorting injured people into
    groups based on their need for or likely benefit
    from immediate medical treatment).
  • Although some type of triage usually is performed
    at the scene or by an emergency response team,
    triage is always the first step performed in the
    emergency department.

9
  • Two essential questions to be considered in the
    triage evaluation are
  • 1. Is the patients life in immediate danger?
  • 2. Is the patients life in potential danger?
  • If the patients life is in immediate danger, the
    goals of immediate treatment are patient
    stabilization and evaluation and management of
    airway, breathing, and circulation (ABCs).

10
  • History
  • A history of the patients exposure provides a
    framework for managing the poisoning or overdose.
  • Key points include identifying the drug(s) or
    toxin(s), the time and duration of the exposure,
    first aid treatment given before arrival at the
    hospital, allergies, and any underlying disease
    processes or related injuries.
  • This information may be obtained from the
    patient, family members, friends, rescuers, or
    bystanders.
  • In some cases, family or police may need to
    search the patients home for clues.
  • Clothing and personal effects may supply
    additional
  • information.

11
  • Physical Examination
  • A quick but thorough physical examination is
    essential.
  • Preliminary examination results lead to the
    in-depth evaluation and serial assessment of
    affected systems (actual or anticipated).
  • As noted previously, a toxidrome is a group of
    signs and symptoms associated with overdose or
    exposure to a particular category of drugs and
    toxins.
  • Recognizing the presence of a toxidrome may help
    identify the toxin(s) or drug(s) to which the
    patent was exposed, and the crucial body systems
    that may be involved.

12
  • Laboratory Studies
  • Relevant clinical laboratory data are vital to
    the assessment of the poisoned or overdosed
    patient.
  • Tests that provide clues to the agent(s) taken by
    the patient include electrolytes, hepatic
    function, urinalysis, electrocardiography, and
    serum osmolality tests.
  • A serum level measurement of acetaminophen is
    obtained in all patients who have overdosed
    because acetaminophen is a component of many
    prescription and over-the-counter preparations.

13
  • In the event of an acetaminophen overdose, the
  • result of the level is plotted against the time
    since ingestion on the Rumack-Matthew nomogram.
  • Serum level measurements are also available for
    carbamazepine, iron, ethanol, lithium, aspirin,
    and valproic acid and may be obtained if these
    agents are suspected in an overdose.

14
  • MANAGEMENT
  • Management of the poisoned or overdosed patient
    seeks
  • to prevent absorption of and further exposure to
    the agent.
  • After triage to determine the status of the
    patients airway, breathing, and circulation, the
    patient must be stabilized.
  • Treatment begins with first aid at the scene and
    continues in the emergency department and often
    the intensive care unit (ICU).
  • Advanced general management involves further
    steps to prevent absorption and enhance
    elimination of the agent.
  • For instance, antidotes, antivenins (the
    treatment of venomous bites or stings) or
    antitoxins may be administered.

15
  • The health care team must further support vital
    functions and monitor and treat multisystem
    effects.
  • Patient and family teaching to prevent future
    exposures is another part of the nurses
    management strategy.

16
  • Examples of Nursing Diagnoses
  • and Collaborative Problems for the Poisoned
  • or Overdosed Patient

17
Examples of Nursing Diagnosesand Collaborative
Problems for the Poisonedor Overdosed Patient
  • Poisoning
  • Ineffective Breathing Pattern
  • Impaired Gas Exchange
  • Ineffective Tissue Perfusion
  • Fluid Volume Imbalance, Risk for
  • Impaired Thought Processes
  • Violence, Risk for (to self or others)
  • Self-Esteem Disturbance
  • Ineffective Individual/Family Coping
  • Injury, Risk for
  • Ineffective Role Performance
  • Acidosis/Alkalosis, Risk for
  • Atelectasis
  • Hypoxemia
  • Dysrhythmias
  • Hypovolemia
  • Electrolyte Imbalances

18
  • Stabilization
  • Stabilization of patients includes performing the
    steps
  • summarized in Box 56-2, which are also discussed
    in the
  • following list
  • Airway Nasotracheal or endotracheal intubation
    may be necessary to adequately maintain and
    protec the patients airway.
  • Breathing Mechanical ventilation may be
    necessary to support the patient.
  • Many drugs and toxins, such as heroin, depress
    the respiratory drive.
  • Patients therefore may require ventilator
    assistance until the drugs or toxins are
    eliminated from the body.

19
  • Circulation Complications range from shock
    caused
  • by fluid loss to fluid overload, and are often
    related to
  • the patients hydration status and the ability
    of the cardiovascular system to adjust to drug-
    or toxin-induced
  • changes.
  • For example, rattlesnake envenomations often
    cause third-spacing of fluid into the area of the
    bite, leading to intravascular hypovolemia.
  • As a consequence, the patient develops
    hypotension, which usually responds to aggressive
    intravenous (IV) fluid therapy.
  • Some toxic drug ingestions impair myocardial
    contractility, and fluid overload may result
    because of the hearts inability to pump
    effectively.

20
  • In these cases, fluid balance needs to be
    carefully controlled.
  • Invasive monitoring (e.g., central venous
    pressure, pulmonary artery catheter, Foley
    catheter with urometer) and drug therapy may be
    necessary to prevent or minimize complications
    such as pulmonary edema

21
  • Cardiac function Many drugs and toxins cause
    cardiac conduction delays and arrhythmias.
  • The history of the drug(s) or toxin(s) involved
    may not be reliable or even known, especially
    when patients are found unconscious or have
    attempted suicide

22
  • In these cases, continuous cardiac monitoring and
    12-lead electrocardiograms help detect
    cardiotoxic effects.
  • Acidbase balance and electrolyte homeostasis
    Electrolyte abnormalities and metabolic acidosis
    frequently occur and may require serial
    measurements of electrolytes and arterial blood
    gases (ABGs), and other specific laboratory
    tests.
  • For example, serial measurements of
    electrolytes, ABGs, and salicylate levels are the
    means of evaluating aspirin toxicity.
  • Aspirin, in large ingestions, may form a solid
    mass in the gastrointestinal (GI) tract, called a
    concretion, instead of breaking apart and
    dissolving.

23
  • As a result, absorption is delayed, and
  • the development of toxic effects, such as
    hypokalemia, metabolic acidosis, and respiratory
    alkalosis, may not be observed for several hours.

24
  • Mentation Many factors can affect the patients
    mental status.
  • Hypoglycemia and hypoxemia are two that can be
    life-threatening but easily addressed by
    administering oxygen and IV dextrose until
    laboratory results are available.
  • Patients with chronic alcoholism also have a
    special risk called Wernicke-Korsakoff syndrome,
    which is characterized by ataxia and altered
    mentation.

25
  • Early IV or intramuscular administrationn of
    thiamine (vitamin B1) may prevent exacerbation of
    the syndrome.
  • Naloxone (Narcan) is a narcotic antagonist that
    reverses narcotic-induced central nervous system
    (CNS) and respiratory depression.
  • It is often initially given to comatose patients.
  • It must be given cautiously, however, because it
    can precipitate withdrawal in narcotic-dependent
    individuals, which may present as violent,
    agitated behavior, thus placing nurses and other
    health care providers in danger.
  • In the critical care unit it may be necessary to
    continue to administer boluses of naloxone to a
    patient because of its short duration of action
    compared with the duration of action of most
    opioids.

26
  • In such circumstances it may be necessary to give
    naloxone by continuous infusion.
  • Because it is often unclear why a patient is
    comatose, emergency response personnel may
    administer what is commonly referred to as a
    coma cocktail, consisting of D50, vitamin B1,
    and naloxone, at the scene.
  • These agents are well tolerated and have minimal
    toxicities.
  • Proceeding with this therapy at the scene
    addresses all three easily correctable
    possibilities (hypoglycemic, alcoholic, or
    narcotic coma) without wasting time waiting for
    laboratory results to become available.

27
  • Injuries associated with toxic exposure and
    underlying
  • disease processes
  • Any injuries associated with toxic exposure and
    other underlying disease processe identified
    during the initial physical examination are
    treated or monitored, or both.
  • For example, the street drug phencyclidine (PCP)
    may provoke violent, agitated, bizarre behavior,
    leading to trauma during the acute toxic phase.
  • For instance, the patient with pre-existing
    ischemic heart disease may not be able to
    tolerate the hypoxemia associated with carbon
    monoxide poisoning as well as a young, healthy
    patient.

28
  • Vital signs and temperature
  • The critical or potentially critical patients
    vital signs and temperature are measured
    frequently to track changes indicating additional
    problems.

29
  • Initial Decontamination
  • First aid may be given by a bystander, health
    care provider, or emergency response team, or in
    the emergency department.
  • The physicochemical properties of the agent and
    the amount, route, and exposure time help
    determine the type and extent of management
    required.
  • Decontamination methods for ocular, dermal,
    inhalation, and ingestion exposures follow.

30
  • OCULAR EXPOSURE
  • Many substances can accidentally splash into the
    eyes.
  • When this happens, the eyes must be flushed to
    remove
  • the agent.
  • Immediate irrigation with lukewarm water or
    normal saline is recommended.
  • Continuous flooding of the eyes with a large
    glass of water or low-pressure shower should be
    done for 15 minutes.
  • The patient should blink the eyes open and closed
    during the irrigation.
  • If necessary, the pH of the eyes can be tested.
    If the pH is abnormal, irrigation should continue
    until the pH normalizes.
  • An ophthalmologic examination is needed when
    ocular irritation or visual disturbance persists
    after irrigation.

31
  • DERMAL EXPOSURE
  • When dermal exposure occurs, the patient should
    flood the skin with lukewarm water for 15 to 30
    minutes.
  • Most companies that produce or use chemical
    agents have showers for this purpose.
  • The patient should remove any clothing that may
    have been contaminated.
  • After standing under running water for the
    allotted time ????? ??????, the patient should
    then wash the area gently with soap and water and
    rinse thoroughly.

32
  • Some toxins may require further decontamination.
    For example, three separate soap and water
    washings or showers are recommended to
    decontaminate organophosphate pesticides (e.g.,
    Malathion or Diazinon).
  • Protective clothing should be worn to reduce the
    risk for toxicity while handling contaminated
    clothing or assisting with skin decontamination.

33
  • Although it may seem logical to apply an acid to
    neutralize a base exposure and a base to
    neutralize an acid exposure, this can be quite
    dangerous.
  • Neutralization is the reaction between an acid
    and a base, in which the H of the acid and the
    OH- of the base react to produce H2O (water) and
    heat.
  • The heat produced by this reaction is significant
    enough to cause burns.
  • Therefore, neutralizing the skin after a dermal
    exposure is not recommended.

34
  • INHALATION EXPOSURE
  • A victim of an inhalation exposure should be
    moved to fresh air as quickly as possible.
  • The responder must also protect himself or
    herself from the airborne toxin.
  • Further evaluation is needed if the patient
    experiences respiratory irritation or shortness
    of breath.
  • Large-scale exposures or those that occur at the
    workplace may require consultation with a HAZMAT
    team, a group of individuals specially trained to
    manage exposures to hazardous materials.

35
  • INGESTION EXPOSURE
  • Milk or water dilutes ingested irritants such as
    bleach or
  • caustics such as drain cleaner.
  • After such an ingestion, adults should drink 8 oz
    of milk or water and children should drink 2 to 8
    oz (based on their size).
  • Further evaluation is necessary after dilution if
    there is mucosal irritation or burns.
  • Because of the risk of aspiration, ingestions
    should not be
  • diluted when they are accompanied by seizures,
    depressed
  • mental status, or loss of the gag reflex.
  • Again, neutralization is not used because of the
    risk of thermal burn.

36
  • Gastrointestinal Decontamination
  • Gastric lavage, adsorbents is the adhesion of
    molecules of gas, liquid, or dissolved solids to
    a surface.( ????????, cathartics, and whole-bowel
    irrigation are used to prevent absorption of, and
    forestall ????? toxicity from, almost all drugs
    and a variety of toxins.
  • The American Academy of Pediatrics no longer
    recommends the use of emetics (such as syrup of
    ipecac) for GI decontamination.

37
  • GASTRIC LAVAGE
  • Gastric lavage is a method of GI decontamination.
  • Fluid (usually normal saline) is introduced into
    the stomach through a large-bore orogastric tube
    and then drained in an attempt to reclaim part of
    the ingested agent before it is absorbed.
  • A small-bore nasogastric tube is ineffective for
    lavage because particulate matter such as tablets
    or capsules are too large to pass through the
    tube.
  • If airway protection is necessary, the patient
    should be intubated before lavage begins.

38
  • As noted, a large-bore orogastric tube (a 36 to
    40 French in adults and a 16 to 28 French in
    children) is used to evacuate particulate matter,
    including whole tablets and capsules.
  • For the lavage, the patient is positioned in the
    left
  • lateral decubitus position, with the head lower
    than the feet.
  • Before beginning, the tube should be coated with
    a jelly lubricant such as hydroxyethylcellulose.
  • The position of the tube must be confirmed after
    passing, either by aspirating and checking the pH
    of the aspirate, or by insufflation of air, while
    listening over the stomach.

39
  • The lavage is accomplished by attaching a funnel
    or syringe to the end of the tube and instilling
    aliquots of 150 to 200 mL (50 to100 mL in
    children) of 100F (38C) saline into the
    stomach.
  • Placing the funnel and tube below the patient
    allows the fluid to return by gravity.
  • This procedure is repeated until clear fluid
    returns or 2 L of fluid has been used.
  • The contents of the stomach can then be collected
    for drug or toxin identification.

40
  • Complications of gastric lavage include
    esophageal perforation, pulmonary aspiration,
    electrolyte imbalance, tension pneumothorax, and
    hypothermia (when cold lavage solutions are
    used).
  • Lavage is contraindicated in cases of ingestion
    of caustics or hydrocarbons with a high
    aspiration potential.
  • Because of the associated risks and the lack of
    clear evidence supporting its use, gastric lavage
    should be used only if the patient has ingested a
    life-threatening amount of a substance and the
    procedure is undertaken within an hour of the
    ingestion.

41
  • ADSORBENTS
  • An adsorbent is a solid substance that has the
    ability
  • to attract and hold another substance to its
    surface (to adsorb).
  • Activated charcoal is an effective nonspecific
    adsorbent of many drugs and toxins.
  • Activated charcoal adsorbs, or traps ??????, the
    drug or toxin to its large surface area and
    prevents absorption from the GI tract.

42
Drugs and Toxins Well Adsorbedby Activated
Charcoal
  • Acetaminophen
  • Amphetamines
  • Antihistamines
  • Aspirin
  • Barbiturates
  • Benzodiazepines
  • Beta blockers
  • Calcium channel blockers
  • Cocaine
  • Opioids
  • Phenytoin
  • Theophylline
  • Valproic acid
  • Drugs and Toxins Not Well Adsorbed
  • by Activated Charcoal
  • Acids
  • Alkalis
  • Alcohols
  • Iron
  • Lithium
  • Metals

43
ADSORBENTS
  • Activated charcoal is a fine, black powder that
    is given as a slurry ????? with water, either
    orally or by nasogastric or orogastric tube, as
    soon as possible after the ingestion.
  • Commercially available activated charcoal
    products may be mixed with 70 sorbitol to
    decrease grittiness (composed of or covered with
    relatively large particles, increase palatability
    (Acceptable to the taste) , and serve as a
    cathartic.
  • The usual dose that is given is one 50-g bottle.

44
ADSORBENTS
  • Administration of more than one dose is
    controversial, and usually limited to overdoses
    of large quantities of aspirin, and theophylline.
  • Activated charcoal is used cautiously in patients
    with diminished bowel sounds and is
    contraindicated in patients with bowel
    obstruction.

45
CATHARTICS
  • A cathartic is a substance that causes or
    promotes bowel movements.
  • The use of cathartics alone in the management of
    poisoning is not an acceptable means of G
    decontamination.
  • In theory, cathartics decrease the absorption of
    drugs and toxins by speeding their passage
    through the GI tract, thereby limiting their
    contact with mucosal surfaces.

46
CATHARTICS
  • Magnesium citrate or 70 sorbitol often is used.
  • Currently, however, there is no clinical evidence
    that shows that a cathartic can reduce the
    bioavailability of drugs or improve the outcome
    of poisoned patients.
  • Data regarding the effectiveness of mixing
    cathartics with activated charcoal are not yet
    available. Clearly, more research needs to be
    done in this area of clinical practice.

47
  • WHOLE-BOWEL IRRIGATION
  • The goal of whole-bowel irrigation is to give
    large volumes of a balanced electrolyte solution
    rapidly (1 to 2 L/hour) to flush the patients
    bowel mechanically without creating electrolyte
    disturbances.
  • Used as a bowel preparation for colonoscopy, it
    is also used as a GI decontamination procedure
    for patients who have ingested bags or vials of
    narcotics to avoid arrest, for drug smugglers who
    pack their GI tracts with narcotics (either
    orally or rectally), and for patients who have
    overdosed on modified-release pharmaceuticals.

48
  • Commercial products used in whole-bowel
    irrigation include GoLYTELY and Colyte.
  • Both products are dispensed (To prepare and give
    out ) as powders and are given after adding
    water.
  • Whole-bowel irrigation is contraindicated in the
    patient with bowel obstruction or perforation.

49
  • Enhanced Elimination of the Drug or Toxin
  • The pharmacological and kinetic characteristics
    of a drug
  • or toxin greatly influence the severity and
    length of the clinical course in the acutely
    poisoned or overdosed patient.
  • The absorption rate, body distribution,
    metabolism, and
  • elimination must be considered when choosing
    methods to eliminate the drug or toxin from the
    body.
  • There are six methods of enhanced elimination
  • 1. Multiple-dose activated charcoal
  • 2. Alteration of urine pH
  • 3. Hemodialysis
  • 4. Hemoperfusion
  • 5. Chelation
  • 6. Hyperbaric oxygenation (HBO) therapy

50
  • MULTIPLE-DOSE ACTIVATED CHARCOAL
  • Administering multiple doses of activated
    charcoal can result in greater adsorption of
    certain drugs such as aspirin, valproic acid, and
    theophylline.
  • Multiple-dose activated charcoal is given orally,
    by nasogastric tube, or by orogastric tube every
    2 to 6 hours.
  • Complications of multipledose activated charcoal
    include aspiration and bowel obstruction.

51
  • ALTERATION OF URINE pH
  • Alkalinizing the patients urine enhances
    excretion of drugs that are weak acids by
    increasing the amount of ionized drug in the
    urine.
  • This form of enhanced elimination is also termed
    ion trapping.
  • The urine is alkalinized by administering a
    continuous IV infusion of one to three ampules of
    sodium bicarbonate per liter of fluid.
  • Urine alkalinization is frequently used in
    patients experiencing a salicylate overdose.
  • Complications of alkalinization include cerebral
    or pulmonary edema and electrolyte imbalances.
  • Urine acidification is no longer recommended
    because
  • of low drug clearance and the risk of
    complications such as rhabdomyolysis.

52
  • Rhabdomyolysis is the breakdown of muscle fibers
    resulting in the release of muscle fiber contents
    into the circulation.
  • Some of these are toxic to the kidney and
    frequently result in kidney damage.
  • Causes, incidence, and risk factors   
  • Myoglobin is an oxygen-binding protein pigment
    found in the skeletal muscle. When the skeletal
    muscle is damaged, the myoglobin is released into
    the bloodstream. It is filtered out of the
    bloodstream by the kidneys. Myoglobin may block
    the structures of the kidney, causing damage such
    as acute tubular necrosis or kidney failure.
  • Myoglobin breaks down into potentially toxic
    compounds, which will also cause kidney failure.
    Necrotic (dead tissue) skeletal muscle may cause
    massive fluid shifts from the bloodstream into
    the muscle, reducing the relative fluid volume of
    the body and leading to shock and reduced blood
    flow to the kidneys.
  • The disorder may be caused by any condition that
    results in damage to skeletal muscle, especially
    trauma.

53
  • HEMODIALYSIS
  • Hemodialysis is the process of altering the
    solute composition of blood by removing it from
    an artery, diffusing it across a semipermeable
    membrane (between the blood and a salt solution),
    then returning it into a vein.
  • It is used in moderate to severe intoxications to
    remove a drug or toxin rapidly when more
    conservative methods (e.g., gastric lavage,
    activated charcoal, antidotes) have failed or in
    patients with decreased renal function.
  • Hemodialysis requires consultation with a
    nephrologist and specially trained nurses to
    perform the procedure and monitor the patient.

54
  • Low molecular weight, low protein binding, and
    water solubility are factors that make a drug or
    toxin suitable for hemodialysis.
  • Drugs and toxins that may be removed by
    hemodialysis include ethylene glycol (commonly
    found in antifreeze), methanol, lithium,
    salicylates, and theophylline.

55
  • HEMOPERFUSION
  • Hemoperfusion removes drugs and toxins from the
    patients blood by pumping the blood through a
    cartridge
  • of adsorbent material, such as activated
    charcoal.
  • An advantage of hemoperfusion over hemodialysis
    is that the total surface area of the dialyzing
    membrane is much greater with the hemoperfusion
    cartridges.
  • As in hemodialysis, drugs that have high
    tissue-binding characteristics and a large volume
    distributed outside the circulation are not good
    candidates for hemoperfusion because little drug
    is found in the blood.
  • Although rarely used in the poisoned and
    overdosed population, hemoperfusion has been used
    successfully in patients experiencing a
    theophylline overdose

56
  • CHELATION
  • Chelation involves the use of binding agents to
    remove toxic levels of metals from the body, such
    as mercury, lead, iron, and arsenic.
  • Examples of chelating agents are dimercaprol (BAL
    in oil), calcium disodium edetate (EDTA),
    succimer (DMSA), and deferoxamine.
  • Concerns about the toxicity of the chelators
    their tissue distribution characteristics and
    the stability, distribution, and elimination of
    the chelatormetal complex make chelation a
    complicated procedure.

57
  • HYPERBARIC OXYGENATION THERAPY
  • In HBO therapy, oxygen is administered to a
    patient in an enclosed chamber at a pressure
    greater than the pressure at sea level (e.g., 1
    atmosphere absolute).
  • This therapy has been used in carbon monoxide and
    methylene chloride poisonings (methylene chloride
    is metabolized to carbon monoxide in the body).
  • The result is enhanced elimination of carbon
    monoxide The half-life of carbon monoxide in
    room air is 5 to 6 hours, in 100 oxygen it is 90
    minutes, and in an HBO chamber it is 20 minutes.

58
  • Another use of HBO therapy is the treatment of
    diving sickness (the bends).
  • However, the small number of HBO chambers and
    lack of around-the-clock staffing limits the wide
    use of this therapy.
  • Complications of HBO therapy include
    pressure-related otalgia (ear pain), sinus pain,
    tooth pain, and tympanic membrane rupture.
  • Confinement (freedom of action) anxiety,
    convulsions, and tension pneumothorax also have
    been observed in patients receiving HBO therapy.

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  • Antagonists, Antitoxins, and Antivenins
  • In pharmacology, an antagonist is a substance
    that counteracts the action of another drug.
  • Although the general public often believes there
    is an antidote for every drug or toxin, the
    opposite is closer to the truth.
  • There are, in fact, very few antidotes.

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  • Antitoxins neutralize a toxin.
  • For instance, botulism(food poisoning from
    ingesting botulin)(potent bacterial toxin
    produced by the bacterium Clostridium botulinum
    that causes botulism can be used as a bioweapon)
    antitoxin trivalent (equine) is available through
    the Centers for Disease Control and Prevention to
    counteract the effects of botulism.

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  • Antivenins are antitoxins that neutralize the
    venom of the offending snake or spider.
  • There are several antitoxins each is active
    against a specific venom.
  • For example, antivenin Crotalidae polyvalent
    (equine) is active againstvenoms of the family
    Crotalidae, which are pit viper snakes native to
    North, Central, and South America. Because this
    agent is derived from horse serum (and therefore
    recognized as foreign by the human immune
    system), significant side effects such as
    anaphylactic or anaphylactoid reactions are
    common.

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  • Recently approved by the U.S. Food and Drug
    Administration (FDA) is Crotalidae polyvalent
    immune Fab (CroFab), a product that is produced
    using a purification process that removes the Fc
    fragment and leaves only the Fab fragments of the
    immunoglobulins.
  • Typically, this process results in a product that
    causes
  • fewer reactions in humans.
  • Antivenin (Lactrodectus mactansequine) is
    available for black widow spider bites as well as
    for envenomations by the eastern and Texas coral
    snake (Micrurus fulvius equine).
  • However, there are many venomous snakes and
    spiders for which no antivenin exists.
  • Envenomation from one of these species is treated
    with symptomatic and supportive care

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  • Continuous Patient Monitoring
  • Seriously poisoned or overdosed patients may
    require continued monitoring for hours or days
    after exposure.
  • Physical examination, the use of diagnostic
    tools, and careful assessment of clinical signs
    and symptoms provide information about the
    patients progress and direct medical and nursing
    management.

64
  • Diagnostic tools include the following
    Electrocardiography Electrocardiography can
    provide
  • evidence of drugs causing arrhythmias or
    conduction
  • delays (e.g., tricyclic antidepressants).
  • Radiology Many substances are radiopaque, or
    can
  • be visualized using a contrast-enhanced computed
  • tomography (CT) scan (e.g., heavy metals, button
  • batteries, some modified-release tablets or
    capsules,
  • aspirin concretions, cocaine or heroin
    containers).
  • Chest radiographs provide evidence of aspiration
  • and pulmonary edema.

65
  • Electrolytes, ABGs, and other laboratory tests
    Acute poisoning can cause an imbalance in a
    patients electrolyte levels, including sodium,
    potassium, chloride, carbon dioxide content,
    magnesium, and calcium.
  • Signs of inadequate ventilation or oxygenation
    include
  • cyanosis, tachycardia, hypoventilation,
    intercostal
  • muscle retractions, and altered mental status.
  • Such signs should be evaluated by pulse oximetry
    and
  • ABG measurements.
  • Seriously poisoned patients require routine
    screening of electrolytes, ABGs, creatinine, and
    glucose complete blood count and urinalysis.

66
  • Anion gap The anion gap is a simple,
    cost-effective
  • tool that uses common serum measurements, such
    as
  • sodium, chloride, and bicarbonate, to help
    evaluate
  • the poisoned patient for certain drugs or
    toxins.
  • The anion (A negatively charged ion) gap
    represents the difference between unmeasured
    anions and cations (An ion or group of ions
    having a positive charge ) in the blood.

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  • The normal value for the anion gap is
    approximately
  • 8 to 16 mEq/L.
  • An anion gap that exceeds the upper normal value
    can indicate metabolic acidosis caused by an
    accumulation of acids in the blood.
  • Drugs, toxins, or medical conditions that can
    produce an
  • elevated anion gap include iron, isoniazid
    (INH), lithium, lactate, carbon monoxide,
    cyanide,, methanol, metformin, ethanol, ethylene
    glycol, salicylates, hydrogen sulfide, ,diabetic
    ketoacidosis, uremia, seizures, and starvation.
  • Although these substances and processes can cause
    an elevated anion gap, a normal anion gap alone
    does not preclude (To make impossible) a toxic
    exposure.

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  • Anion gap is an 'artificial' and calculated
    measure that is representative of the unmeasured
    ions in plasma or serum (serum levels are used
    more often in clinical practice). The 'measured'
    cations are sodium (Na), Potassium (K), Calcium
    (Ca2) and Magnesium (Mg2). The 'unmeasured'
    cations include a few normally occurring serum
    proteins, and some pathological proteins (e.g.,
    paraproteins found in multiple myeloma).

69
  • Likewise, the 'measured' anions are chloride
    (Cl-), bicarbonate (HCO3-) and phosphate (PO3-),
    with the 'unmeasured' anions being sulphates and
    a number of serum proteins (predominantly
    albumin).
  • By convention (and for the sake of convenience)
    only Na, Cl- and HCO3- are used for calculation
    of the anion gap as noted above, especially in
    clinical settings.

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  • In normal health there are more unmeasured
    anions(compared to unmeasured cations) in the
    serum therefore, the anion gap is usually
    positive. The anion gap varies in response to
    changes in the concentrations of the
    above-mentioned serum components that contribute
    to the acid-base balance. Calculating the anion
    gap is clinically useful, as it helps in the
    differential diagnosis of a number of disease
    states.

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  • Osmolal gap The osmolal gap is the difference
    between the measured osmolality (using the
    freezing point depression method) and the
    calculated osmolality.
  • The calculated osmolality is derived using
    laboratory values for the major osmotically
    active substances in the serum, such as sodium,
    glucose, and blood urea nitrogen (BUN).
  • Like the anion gap, it is a simple,
    cost-effective tool for evaluating the poisoned
    patient for certain drugs or toxins

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  • Toxicology screens A toxicology screen is a
    laboratory analysis of a body fluid or tissue to
    identify drugs or toxins
  • .
  • Although saliva, spinal fluid, and hair may be
    analyzed, blood or urine samples are used more
    frequently.
  • The number and type of drugs assessed by
    toxicology screens vary.
  • Each screen tests for specific drugs or agents.
  • For example, drug abuse screens usually identif
    several common street or prescription drugs,
    whereas a coma panel detects common drugs that
    cause CNS depression.

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  • Comprehensive screens include many drugs (ranging
    from antidepressants to cardiac drugs to
    alcohols) and are more expensive.
  • A number of factors limit the role of toxicology
    screens in managing poisonings or overdoses.
  • The test sample must be collected while the drug
    or toxin is in the body fluid or tissue used for
    testing.
  • For example, cocaine is a rapidly metabolized
    drug however, its metabolite, benzoylecgonine,
    can be detected in the urine for several hours
    after cocaine use.

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  • Also, a toxicology screen with a negative result
    does not necessarily mean that no drug or toxin
    is present, but rather that none of the drugs or
    toxins for which a patient has been screened is
    present.
  • For example, gamma-hydroxybutyrate (GHB) is not
    included in toxicology screens because it is
    rapidly metabolized to small, unmeasurable
    molecules.
  • The sample must also be properly collected, and
    there must be a laboratory near enough to obtain
    results quickly.

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  • For many smaller, rural laboratories, these tests
    are taken by a courier service???? ??????? or
    mailed to a larger laboratory, and the results
    are not available for several days.
  • In these situations, the value of the test for
    managing the immediate overdose or poisoning
    needs to be considered.

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  • Patient Teaching
  • One of the interventions the nurse can perform in
    the emergency department or intensive care unit
    is preventive teaching.
  • All patients (and parents of pediatric patients)
    who have survived a toxic encounter should be
    taught how to prevent such an incident from
    recurring.
  • Parents of young children need information on
    child-proofing their home.
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