Block 4: Intro to Clinical Toxicology
Terms
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- Accidental poisonings account for what percentage of poisonings each year?
- 90%
- What portion of the population is most often accidentally poisoned?
- Children
- If 90% of poisoning are accidental, what percentage is intentional?
- 10%
- What portions of the population make up the intentional poisonings?
- adolescents and adults
- 95% of poisonings in children involve how many substances?
- One substance
- TRUE or FALSE: all adult poisonings are mixed ingestions.
- FALSE-- 50% of adult poisonings are mixed
- About what percentage of poisoning deaths are intentional?
- About 50%
- Those lethal intentional poisonings occur most often in what portion of the population?
- Adolescents
- These two classes of substances are the most commonly ingested substances.
-
1)Household cleaning substances
2)OTC analgesics - These two types of drugs are most commonly involved in fatal ingestions
-
1)antidepressants
2)analgesic drugs - Which two types of poisonings are frequently misdiagnosed (Hint: we're talking situational)?
-
1)occupational
2)enviromental - TRUE or FALSE: only primary care and ER physicians deal with poisonings
- FALSE: docs in many specialties encounter poisonings
- TRUE or FALSE: understanding a general approach to the poisoned pt can improve clinical outsome significantly.
- TRUE
- Name the six steps in the general approach to the poisoned pt.
-
1)pt stabilization
2)rapid pt eval
3)prevent reabsorption of toxic agent
4)enhance elimination of toxic agent
5)use specific antidote (where available)
6)supportive care - This type of assessment/therapy is paramount in initial phases of management
- Basic Life Support (BLS)
- Pts w/depressed levels of consciousness, including coma, get these four drugs
-
1)naloxone
2)D50
3)thiamine
4)oxygen - TRUE or FALSE: drug-induced seizures are easily controlled
- FALSE
- What two aspects of respiration must be carefully assessed in the pt?
-
1)ventilation
2)oxygenation - TRUE or FALSE: the history in drug overdose is quite reliable and your best source of info
- FALSE: it's quite unreliable; seek ancillary info
- TRUE or FALSE: the physical exam is extremely important for gathering key data.
- TRUE!
- HTN and tachycardia on PE may point to this illicit drug as cause of OD
- Cocaine
- Hyperpnea and elevated temp suggest this as a cause of OD
- Salicylate poisoning
- Anticholinergic poisoning may cause your skin to become *what* and *what*?
- Warm and Dry
- This physical finding may suggest methemoglobinemia or hypoxia.
- Cyanosis
- Needle tracks in a comatose pt may suggest what type of overdose?
- Narcotic overdose
- Miosis may be see with what two types of agonists?
- Opiate and Cholinergic agonists
- Mydriasis may be seen with what two types of agents?
- Sympathomimetic or Anticholinergic agents
- Combined vertical and horizontal nystagmus are seen with OD on what drug?
- PCP
- A bitter almond smell on the pt's breath points to *what* as the cause of poisoning?
- Cyanide
- Chemical burns visible in the oral cavity suggest what?
- Ingestion of caustic substances (drano, anyone?)
- Tachycardia and an unexpected S3 gallop suggest heart failure from what what type of OD?
- OD on negative inotropic agents (Ca2+ channel- or beta-blocking drugs)
- Narcotic, antimuscarinic and sedative poisonings cause what type of bowel sounds?
- hypoactive bowel sounds
- Organophosphate and theophylline poisoning cause what type of bowel sounds?
- hyperactive bowel sounds
- Toxic or metabolic encephalopathy are suggested by neuro findings in what type of distribution?
- Symmetric distribution
- Increased muscle tone is seen when you OD on what type of drug?
- Sympathomimetic drugs
- Tremor, seizures and brisk reflexes are seen when pts OD on these two drugs
- Lithium and theophylline
- Ataxia, dysarthria and nystagmus are seen if you overdose on these three drugs.
-
1)ethanol
2)phenytoin
3)sedative hypnotics - What are the four main toxic syndromes?
-
1)cholinergic
2)anticholinergic
3)narcotic
4)sympathomimetic - Mild hypotension, bradycardia, hypoventilation, lethargy and miosis suggest which toxic syndrome?
- Narcotic syndrome
- TRUE or FALSE: you should delay tx while waiting for the labs on your poisoned pt; you don't want to treat something that's not there!.
- FALSE!
- Name 7 drugs for which there is rapid, direct quantitation (pnemonic: I SALTED)
-
1)Iron
2)Salicylate
3)Acetominophen
4)Lithium
5)Theophylline
6)Ethanol
7)Digoxin - Serum bicarb less than what concentration indicates metabolic acidosis?
- 18 meq/L
- How do you confirm metabolic acidosis?
- Measure arterial pH
- What is the formula for the anion gap?
- AG = [(Na)-(HCO3)+(Cl)]
- What is the normal value for the anion gap?
- 12 plus or minus 2
- Break down the causes for metabolic acidosis given by the pneumonic AT MUD PILES
-
1)Alcohol
2)Toluene
3)Methanol
4)Uremia
5)Diabetic Ketoacidosis
6)Paraldehyde
7)Iron/Isoniazid
8)Lactic Acid
9)Ethylene Glycol
10)Salicylate - Drug-induced pulmonary edema or drug-induced lung injury may cause what finding on arterial blood gas?
- Hypoxia
- Respiratory depression (which is common with any sedating toxin) can cause what finding on ABG?
- Hypercapnia
- These two findings on ABG can be primary respiratory or metabolic and are commonly found in poisoned pts
- Acidemia or alkalemia
- Certain toxic agents are osmotically active in plasma and can be inferred by determining what?
- the osmolar gap
- How do you calculate the calculated serum osmolarity?
- CSO = (2xNa)+(Glucose mg/dL / 18)+(BUN mg/dL / 2.8)
- How do you calculate the osmolar gap?
- OG = measured serum osmolarity - calculated serum osmolarity
- Normally, the osmolar gap is what value?
- Zero (<10 is still considered normal)
- Significant osmolar gaps are seen in poisoning with what four substances (hint: all the same type)?
-
1)methanol
2)ethanol
3)ethylene glycol
4)isopropranolol - Prolonged QRS duration suggests OD on what type of med?
- TCA
- Intact capsules of this mineral can be visualized on plain films of the abdomen.
- Iron
- This is the preferred emetic agent.
- Syrup of Ipecac
- What are the four contraindications for use of Syrup of Ipecac?
-
1)ingestion of corrosive substances
2)pt age < 6 mos
3)absent gag reflex
4)seizures - What is the most important consideration in the performance of gastric lavage?
- Protection of the airway
- When is gastric lavage most useful?
- Recent (within 1 hour) ingestion in which emesis cannot be performed
- What is the contraindication for gastric lavage?
- Ingestion of corrosive substances
- This is the recommended tx for practically all ingestions.
- Activated charcoal
- How do you dose activated charcoal?
- 1-2 gm/kg body weight
- A cathartic (like sorbitol or magnesium citrate) should be administered when in relation to giving the charcoal?
- Administered with or immediately after charcoal
- TRUE or FALSE: if a pt has had a dermal exposure, you should leave on all contaminated clothing to avoid spreading the substance.
- FALSE: contaminated clothing should be removed and properly secured
- How do you treat an eye exposure?
- Immediate copious irrigation with saline
- Ophthalmology consult is required in what two cases?
-
1)caustic exposure
2)complaints of double vision - Renal elimination of weak acids is greatly increased by alkalinizing urine (pH=8) by giving what?
- Sodium bicarb
- Alkalinizing the urine is particularly helpful when?
- Mild-to-moderate salicylate intoxication.
- Poisoning with toxins with high water solubility, low volume of distribution, low molecular weight (<500) and low protein binding can be treated how?
- Hemodialysis
- This detox technique is more effective than hemodialysis for lipid soluble, high-weight poisons with a low volume of distribution.
- Hemoperfusion
- What *is* hemodialysis?
- blood dialyzed extracorporeally through permeable membranes against electrolyte solutions
- What *is* hemoperfusion?
- blood filtered extra-corporeally through a cartridge containing activated charcoal or resin
- Hemoperfusion is used most commonly in intoxication with what drug?
- Theophylline
- This is a frequent adverse effect associated with hemoperfusion.
- Thrombocytopenia
- This method of poison removal is good for drugs that undergo enterohepatic circulation and a few that don't
- Serial oral activated charcoal
- How do you dose serial oral activated charcoal?
- 0.5 gm/Kg every 2-4 hours
- Serial oral activated charcoal is particularly good for poisoning with which three drugs?
-
1)theophylline
2)digitoxin
3)phenytoin - Which two procedures are only employed in severe poisonings of infants?
-
1)plasma exchange
2)exchange transfusion - Fab fragments to digoxin are the prototype in this antidote category
- Immunologic antidotes
- How do the Fab fragments work?
- They bind digoxin and the compound gets filtered by the kidney. This causes a marked reduction in toxicity followed by greatly increased elimination
- This type of antidote is used to treat pts intoxicated with lead, iron, arsenic, gold, copper and mercury.
- Chelator antidotes
- These agents exert pharmacologic actions which oppose those of the poison; also, agents that compete for receptors that mediate toxic actions
- Pharmacologic antidotes
- Give two examples of pharmacologic antidotes
-
1)atropine for organophosphate poisoning
2)isoproterenol for beta-blocker overdose - These agents provide substrates for detox of reactive intermediates or that compete for enzymes that create toxic metabolites
- Biochemical agents
- Name two biochemical antidotes
-
1)N-acetyl-L-cysteine
2)4-methylpyrazole for ethylene glycol - What is the final phase in the management of the poisoned pt?
- Supportive care and observation
- In the poisoned pt, special attention should be paid to what three aspects of ICU care?
-
1)ventilation
2)oxygenation
3)hemodynamics - TRUE or FALSE: cardiac monitoring and frequent lab assessments are done initially.
- TRUE
- You should anticipate what ICU complication in your poisoned pt?
- Aspiration pneumonia
- You should frequently reassess what in your poisoned pt in the ICU?
- fluid and electrolyte status
- TRUE or FALSE: formal psych eval is required for all pts who have attempted suicide before removing them from a one-to-one nursing setting.
- TRUE