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.

59

• 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.

60

• 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.

61

• 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.

62

• 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

63

• 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.

67

• 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.

68

• 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.

70

• 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.

71

• 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

72

• 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.

73

• 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.

74

• 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.

75

• 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.

76

• 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.