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.

1

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 أبخرة 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. 2

• 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.

3

• Similarly, poisoning can also occur in the health careenvironment 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.

4

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.

5

• 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.

6

ASSESSMENT

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

7

• 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.

8

• Two essential questions to be considered in the triage evaluation are:

1. Is the patient’s life in immediate danger?2. Is the patient’s life in potential danger?

• If the patient’s life is in immediate danger, the goals of immediate treatment are patient stabilization and evaluation and management of airway, breathing, and circulation (ABCs).

9

• History

• A history of the patient’s 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 patient’s home for clues.

• Clothing and personal effects may supply additional information.

10

• 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. 11

• 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.

12

• In the event of an acetaminophen overdose, theresult 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.

13

• 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 patient’s 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.

14

• 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 nurse’s management strategy.

15

Examples of Nursing Diagnoses

• and Collaborative Problems for the Poisoned

• or Overdosed Patient

16

Examples of Nursing Diagnosesand Collaborative Problems for the Poisoned

or 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

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• 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 patient’s 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.

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• Circulation: Complications range from shock causedby fluid loss to fluid overload, and are often related tothe patient’s hydration status and the ability of the cardiovascular system to adjust to drug- or toxin-inducedchanges.

• 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 heart’s inability to pump effectively.

19

• 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

20

• 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

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• In these cases, continuous cardiac monitoring and 12-lead electrocardiograms help detect cardiotoxic effects.

• ■ Acid–base 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.

22

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

23

• Mentation: Many factors can affect the patient’s 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.

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• 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.

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• 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.

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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.

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• Vital signs and temperature:

• The critical or potentially critical patient’s vital signs and temperature are measured frequently to track changes indicating additional problems.

28

• 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.

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• OCULAR EXPOSURE• Many substances can accidentally splash into the eyes.

• When this happens, the eyes must be flushed to removethe 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. 30

• 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 المخصص the patient should then wash ,الوقتthe area gently with soap and water and rinse thoroughly.

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• 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.

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• 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 Hof 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.

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• 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.

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• 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 bediluted when they are accompanied by seizures, depressedmental status, or loss of the gag reflex.

• Again, neutralization is not used because of the risk of thermal burn.

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• Gastrointestinal Decontamination

• Gastric lavage, adsorbents *is the adhesion of molecules of gas, liquid, or dissolved solids to a surface. cathartics, and whole-bowel ,الممتزات )irrigation are used to prevent absorption of, and forestall إحباط 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.

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• 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.

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• 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 leftlateral 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.

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• 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.

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• 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.

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• 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 الفخاخ, the drug or toxin to its large surface area and prevents absorption from the GI tract.

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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

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ADSORBENTS• Activated charcoal is a fine, black powder that is

given as a slurry الطين 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.

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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.

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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.

45

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.

46

• 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 patient’s 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.

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• 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.

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• Enhanced Elimination of the Drug or Toxin• The pharmacological and kinetic characteristics of a

drugor toxin greatly influence the severity and length of the clinical course in the acutely poisoned or overdosed patient.

• The absorption rate, body distribution, metabolism, andelimination 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 charcoal2. Alteration of urine pH3. Hemodialysis4. Hemoperfusion5. Chelation6. Hyperbaric oxygenation (HBO) therapy

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• 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.

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• ALTERATION OF URINE pH• Alkalinizing the patient’s 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 becauseof low drug clearance and the risk of complications such as rhabdomyolysis.

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• 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.

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• 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.

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• 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.

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• HEMOPERFUSION• Hemoperfusion removes drugs and toxins from the

patient’s blood by pumping the blood through a cartridgeof 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

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• 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 chelator–metal complex make chelation a complicated procedure.

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• 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.

57

• 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 causesfewer reactions in humans.

• Antivenin (Lactrodectus mactans;equine) 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 patient’s progress and direct medical and nursing management.

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■Diagnostic tools include the following: Electrocardiography: Electrocardiography can provideevidence of drugs causing arrhythmias or conductiondelays (e.g., tricyclic antidepressants).

■Radiology: Many substances are radiopaque, or canbe visualized using a contrast-enhanced computedtomography (CT) scan (e.g., heavy metals, buttonbatteries, some modified-release tablets or capsules,aspirin concretions, cocaine or heroin containers).

Chest radiographs provide evidence of aspirationand pulmonary edema. 64

• Electrolytes, ABGs, and other laboratory tests: Acute poisoning can cause an imbalance in a patient’s electrolyte levels, including sodium, potassium, chloride, carbon dioxide content, magnesium, and calcium.

• Signs of inadequate ventilation or oxygenation includecyanosis, tachycardia, hypoventilation, intercostalmuscle retractions, and altered mental status.

• Such signs should be evaluated by pulse oximetry andABG measurements.

• Seriously poisoned patients require routine screening

of electrolytes, ABGs, creatinine, and glucose; complete blood count; and urinalysis. 65

• Anion gap: The anion gap is a simple, cost-effectivetool that uses common serum measurements, such assodium, chloride, and bicarbonate, to help evaluatethe 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.

66

• The normal value for the anion gap is approximately8 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 anelevated 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).

68

• 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.

69

• 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 ساعي ,or mailed to a larger laboratory الخدماتand 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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