Shared Flashcard Set

Details

C2-42 Toxicology of Overdose
blahhhhhh
18
Biology
Professional
12/04/2010

Additional Biology Flashcards

 


 

Cards

Term




Steps in the Clinical Treatment of Drug Overdose

Definition

Patient stabilization
Clinical evaluation.
Prevention of drug absorption.
Enhancement of drug elimination.
Administration of antidote (when applicable).
Supportive care.

Term




Stabilization

Definition

Establishment of airway
O2 if needed
Maintenance of circulation (volume replacement).
Administer lactated Ringer or isotonic sodium chloride solution for volume expansion at 10-20 cc/kg/h until a 1-1.5-cc/kg/h urine flow is established.
Correction of fluid deficits and enhancement of excretion and elimination

Term




Utility of Nomograms:

Definition

Useful in predicting clinical outcome and devising treatment regimens.
Only apply to one single, acute dose.  Does not apply to chronic dosing.  Also not terribly useful for time-release formulations.
For acetaminophen, plasma samples should be taken at least 4 h following the dose to ensure peak plasma concentration has been reached.

Term




Differential Diagnosis

Definition

Important in evaluating poisoning when immediate, specific clinical tests are not available.
Can themselves be used for rough diagnosis.
Ex.) Metabolic acidosis with anion gap > 12:
Limited number of culprits.
Ex.) Elevated osmol gap (> 10 mOsm) suggests the presence of another osmotically active substance.

Term




Anion Gap:

Definition

Elevated anion-gap acidosis is usually caused by an increase

in the presence of unmeasured acid ions, for example, formate

(for methanol poisoning).  The difference gives the number of

unmeasured ions.

Definition of metabolic acidosis:  Disturbance of the body’s

acid-base balance.  

Term

 

 

 

Osmol Gap:

Definition

Measured serum osmolarity (mOsm) – calculated

serum osmolality.

Where serum osmolality =

 

2 X [Na] meq/L  +  [Glucose] mg/dL  +  [BUN] mg/dL

                18                                        2.8

Osmolarity is measured by serum freezing point

 depression.

 • Definition of osmolarity: number of osmotically

 active particles/L of solution.  Basically, it’s the

 number of dissolved particles. 

Term




Differential Diagnosis by Acidosis or Elevated Anion Gap 

Definition

Alcohol (ethanol ketoacidosis)
Toluene
Methanol
Uremia
Diabetic ketoacidosis
Paraldehyde
Iron
Lactic acid
Ethylene glycol
Salicylate

Term




Methods of Treatment

Definition

-Inhibition of

 Absorption


-Enhancement of

   Elimination


-Antidotes

Term




Methods of Treatment I:
Prevention of Further Absorption

Definition

- Gastric Lavage

 

-Induction of Emesis

 

- Activated Charcoal

Term




Activated charcoal, continued.

Definition

Use has increased over the last 20 years.
Charcoal slurry is administered by orogastric tube.
Adsorbs organics.
Charcoal is “activated” by superheated steam – increases number of pores.
Does not adsorb small polar compounds like ethanol or ethylene glycol (antifreeze) very well.
Many treatment centers are beginning to favor its use over emesis and gastric lavage following a large number of clinical trials showing its superiority.

Term




Methods of Treatment II.
Enhancement of Elimination

Definition

Alkalinization of the urine
Hemodialysis
Hemoperfusion
Serial oral activated charcoal

Term




Urinary Alkalinization:

Definition

Enhances the elimination of weak acids (such as aspirin).
Increases the pH of urinary filtrate (so that it is ionized) to prevent reabsorption by the tubules.
Ion trapping:  Trapping the agent in the filtrate by forcing the majority of the compound to exist in its ionized form.  Ions are not reabsorbed and are instead excreted.
Accomplished by adding sterile sodium bicarbonate with 5% dextrose for IV administration and titrating the urine up to pH 7.5 or 8.
PCP overdose is one of the rare cases where acidification is useful.  Acidification can lead to acid-base and electrolyte disturbances that induce acute renal failure.

Term




Hemodialysis

Definition

Removal of a toxic substance by equilibration with dialysate across a semipermeable membrane.
To be effective, toxicant must be water-soluble and of low molecular weight.
Must exhibit low protein binding and volume of distribution.

CANT GET DIGOXIN BECAUSE IT IS NOT CIRCULATED IN BLOOD

 

Term




Hemoperfusion

Definition

Blood is pumped through a perfusion cartridge filled with charcoal or resin.
Criteria for efficient hemoperfusion:
Efficient adsorption to charcoal
Lipid soluble and/or high MW.
Protein binding does not interfere.
Risk:  hypocalcemia, thrombocytopenia, leukopenia.

Term




MDAC – Multiple Dose Activated Charcoal

Definition

Serial administration (every 2 – 4 h) of activated charcoal.
Increases systemic clearance
Increases nonrenal clearance
Blocks enteroheptic circulation
Serves as a sink in the gut for toxin

Toxins that favor MDAC
Significant enterohepatic circulation and bioactivation.
Prolonged plasma half-life
Small Vd
Small amount of protein binding
pKa that maximizes transport across cell membranes
Sustained release tablets

 

Term

 

 

 

Antidote Treatment: Methanol

Definition

Main component of some windshield wiper fluids
Clinical signs:  Elevated anion gap and osmol gap.
Treatment:  IV sodium bicarbonate and hemodialysis.
Methanol is bioactivated:

Methanol                   formaldehyde                  formic

               acid

Agents which inhibit ADH (4-methylpyrazole) or saturate the enzyme (sterile solutions of ethanol) are used as therapies.  Note:  4-MP (also referred to as fomepizole) and ethanol infusion can also be used to treat ethylene glycol poisoning.

Term

 

 

 

Treatment of Metabolic Acidosis

Definition

Treat the metabolic acidosis.
Inhibit metabolism using ethanol or fomepizole.
Fomepizole, an inhibitor of ADH, does not induce CNS depression or hypoglycemia, and plasma levels are easier to maintain than ethanol.
Hemodialysis.

Term




Antidote Treatment for Acetaminophen

 

Definition

Clinical presentation is confusing. Difficult to estimate time of ingestion.
Waiting for clinical symptoms is an inadequate strategy.  Presentation of symptoms may be delayed.
By comparison to the nomogram, plasma APAP concentration can help determine whether N-acetylcysteine (NAC) therapy is required.
Support therapy:  activated charcoal and gastric lavage (for very recent ingestion).

Supporting users have an ad free experience!