Lecture 3 - General Methods for Treatment of ODs Flashcards
List some ways that we can prevent absorption
1) Gastric emptying
- Emesis (vomiting)
- Gastric lavage (stomach pumping)
2) Adsorption
- activated charcoal
* administered within 1 hour after ingestion
3) Catharsis
- accelerates defecation
- can cause problems with electrolyte/fluid balance
4) Dilution
Use syrup of ____ for emesis
Ipecac
What dose of Ipecac for emesis?
7% (10-30 mL)
What are some CI to Ipecac for emesis?
drowsiness, coma, convulsions, no gag reflex, corrosive/caustic agents
What are some complications to Ipecac for emesis?
- aspiration pneumonitis
- bleedings
- GI tract rupture
gastric lavage
stomach pumping
When is gastric lavage indicated?
only when you’re sure there’s still drug in the stomach that can be pumped out
What are some CI to gastric lavage?
- corrosive/caustic agents
- petroleum distillate
gastric lavage - must protect ______
airways
What are some complications of gastric lavage?
- cardiac arrhythmias
- low pO2
- laryngospasm
- pharyngeal injury
- esophageal or gastric perforation
Gastric Lavage Technique:
______ diameter tube possible
largest
Gastric Lavage Technique:
Position of patient
supine on left-side, with head down below level of stomach
Gastric Lavage Technique:
Airway should be protected with ?
a cuffed endotracheal tube
Gastric Lavage Technique:
Why do you save the aspirate?
for analysis to see what the cause is
Gastric Lavage Technique:
Describe the rest
- Instill aliquots of warm water or normal saline (max 250 mL), followed by draining
- repeat over 20-30 min, till gastric aspirate is clear
- activated charcoal slurry may be instilled before lavage tube is removed
- can be administered orally if patient is conscious, however, it tastes really bad (not very palatable)
Describe activated charcoal
- how it works
- what it does
- pyrloysis - oxidizing agents
- hydrogen bonding, dipole and Van der Waal’s forces
- large surface
- decreases systemic absorption of poisons
- binds poisons that have left the stomach
What are activated charcoal indications?
Indicated for nearly all poisonings except:
- corrosive ingestions (acids, alkalis)
- boric acid
- arsenic
- cyanide
- DDT
- methanol
- ethanol
- ethylene
- glycol
- Fe
- F
- heavy metals
- I, Li, K
- petroleum distillates
- tobramycin
Why are corrosive agents not an indication for activated charcoal ?
corrosive agents are very ionized
contraindications to activated charcoal?
- ingestion of caustic substances
- presence of ileum or bowel obstruction
what does caustic substance mean?
caustic or corrosive substances cause tissue damage through a chemical reaction
What are complications of activated charcoal?
- vomiting
- aspiration pneumonitis
- constipation
- GI obstruction
- charcoal empyema (occurs if there is perforation of the intestine, the activated charcoal gets into peritoneal cavity and can cause infection)
How is activated charcoal administered?
orally or by gastric tube
Dose of activated charcoal for adults
30-100 g as a slurry in water (usually 20-30 g charcoal in 240 mL water)
Dose of activated charcoal for children
<10 years: 1-2 g/kg
10-12 years: 15-20 grams
Some formulations of activated charcoal contain sorbitol. What is it’s purpose?
sweetener but also a cathartic (will accelerate defecation)
MDAC
multiple-dose activated charcoal
MDAC may help prevent _____ of drug in the GIT
reabsorption
MAD increases ____ of drugs excreted with the feces
clearance
Describe gastrointestinal dialysis
Create a concentration gradient because activated charcoal conc is higher outside of the membrane, gets pulled in due to gradient
You keep administering the activated charcoal, ensures that there is a marked serum to GI lumen concentration gradient.
Dosing of MDAC in adults
25 g/2h
50g/4-6h
Dosing of MDAC in children
1-2 g/kg dose q2-4h
What is MDAC efficacious for?
analgesics, antiarrhythmics, benzos, BB, TCA, NSAID, etc.
2 types of Catharsis
1) whole-bowel irrigation
2) cathartics
What are some indications for whole-bowel irrigation indications?
- ingestion of iron or zinc salts
- ingestion of sustained release medications
- ingestion of drug packets “body packers”
- ingestion of “crack” virals “body suffers”
What are some CI to whole-bowel irrigation?
- uncooperative patients
- presence of ileum or GI obstruction
- GI bleeding or perforation
What are some complications to whole-bowel irrigation?
- abdominal cramping
- vomiting
- profuse diarrhea
- hyperchloremia - essential to monitor electrolytes
Describe the technique of whole-bowel irrigation
Administer large volumes of isotonic, non absorbable polyethylene glycol/electrolyte solution over 40 min to several hours
Wait for rectal discharge that looks like the fluid administered (this can take 6-12 hours to appear)
Dose for whole-bowel irrigation for those > 5 years old
Colyte, 1-2 L/h, orally or via gastric tube
Dose for whole-bowel irrigation for those < 5 years old
150-500 mL/h
Describe cathartics (increase defecation)
- less violent
- used to move the poison or the poison/charcoal complex through the GI tract
- can help remove the poison and decrease absorption
- can help prevent the formation of concretions of drug or drug/charcoal complex
- same contraindications and complications as with whole-bowel irrigation
List 3 cathartics
1) Sorbitol
2) Magnesium citrate
3) Magnesium or sodium sulfate
*doses on slide 20
Describe dilution
- fluid administration (water or milk)
- first few minutes after ingestion
- value in some ingestions of corrosive agents
- CI in coma or convulsions
- protein in milk can help to absorb some of the compounds
- not very efficient
How can we enhance elimination?
- diuresis
- peritoneal dialysis
- MDAC
- hemodialysis
- hemoperfusion
- hemofiltration
- plasmapheresis and exchange transfusion
Indications for enhancement of elimination
- For patients who fail to respond adequately to full supportive care (intractable hypotension, HF, seizures, metabolic acidosis or dysrhythmias)
- For patients in whom the normal route of elimination of the toxin is impaired (renal or hepatic dysfunction, preexistent or caused by the overdose)
- For patients in whom the amount of toxin absorbed or the plasma concentration indicate high risk of morbidity or mortality
- For patients who have concurrent disease or are in an age group at particular risk (elderly, infants)
- For patients overdosed with a drug that is known to be successfully removed by such methods
Diuresis is a manipulation of ___
pH
What is the objective of diuresis?
Objective is to increase renal clearance
When will diuresis work?
Only if poison or its active metabolites are excreted in urine
Diuresis is based on what concept?
ion trapping
Describe alkaline diuresis
give NaHCO3 IV to increase urinary pH to 7-8
-increases renal excretion of salicylate, isoniazid, and phenobarbital
Describe acid diuresis
give NH4Cl IV to reduce urinary pH to 4.5-5.5
-claimed to work with weak bases such as amphetamines and phencyclidine; however no evidence of efficacy, systemic acidosis
What is forced diuresis?
Volume expansion with sodium-containing solutions (valid if glomerular filtration is an important determinant of excretion)
What are risks of forced diuresis?
Volume overload manifested by pulmonary and cerebral edema
Give an example of a drug for forced diuresis
furosemide, 10-40mg IV
What must you monitor in forced diuresis??
electrolytes, fluid balance, acid-base balance, and response to diuretic
Risks of giving furosemide?
metabolic acidosis and hypokalemia
What type of compounds can peritoneal dialysis enhance the elimination of?
Give examples
- water soluble
- low MW (< 500 daltons)
- low protein binding
- low Vd
ex. alcohols, lithium, salicylates and theophylline
Problem with peritoneal dialysis?
too slow!
rarely used
Describe the thought process behind MDAC (“gastrointestinal dialysis”)
you create a concentration gradient be depleting the GI tract of the drug, then it pulls the drug from intestine back into stomach
*enhances elimination but also reduces absorption
“Adsorption of the drug by the charcoal maintains a concentration gradient across the intestinal epithelium”
When is MDAC (“gastrointestinal dialysis”) effective?
In overdoses of phenobarbital, theophylline, and valproic acid
peritoneal dialysis uses a _____ membrane
physiologic
hemodialysis uses a ______ membrane
semipermeable
What is required when doing hemodialysis ?
anticoagulation with heparin is required
in poisoned patients, how long is HD usually performed for?
for 4-8 hours
When is hemodialysis indicated?
- poison is dialysable
- patient is deteriorating despite care
- severe electrolyte problems
- potentially lethal blood levels are present
- there is a risk from prolonged coma
- there is risk of renal failure
- specific poisonings (methanol, ethylene glycol, salicylate, theophylline, trichloroethanal, ethanol)
What are complications of hemodialysis?
- clotting and leaking of blood from around connections (thrombosis, bleeding)
- embolus (rare)
- hypotension
- convulsions
- arrhythmias
- infections
Describe charcoal hemoperfusion
- compounds adsorbed by activated charcoal
- cartidge containing a sorbent with very large surface area (no direct contact)
- cartidge changed as often as every 2-4 hours
- anticoagulation
- usually performed for 4-6 hours (flow rates of 250-400 mL/min)
- hemoperfusion is not limited by plasma protein binding
- carbamazepine, phenobarbital, phenytoin and theophylline
complications of charcoal hemoperfusion?
Similar to that of hemodialysis:
- clotting and leaking of blood from around connections (thrombosis or bleeding)
- embolus (rare)
- hypotension
- convulsions
- arrhythmias
- infections
what is hemofiltration?
- movement of plasma across a semipermeable membrane in response to hydrostatic pressure gradient
- no dialysate solution on the other side of the membrane
- smaller solutes are transported across the membrane following the water (bulk flow) while larger solutes, depending on permeability characteristics of the membrane, are excluded
What are some advantages of hemofiltration?
- continue therapy for 24 hours
- remove drugs like lithium and procainamide that distribute slowly from tissue binding sites and from the intracellular compartment
- ultrafiltrate flows of 100-600mL/min can be achieved (higher flow rates than hemodialysis)
What are some disadvantages of hemofiltration?
- rate of removal of drugs may not be sufficient to benefit the crucially ill patients
- complexity, experienced ICU staff is required for monitoring (4-6 hours)
- clearances achieved are significantly lower than those achieved with hemodialysis
look at charts on page 36-37
okay
What is plasmapheresis and exchange transfusion used to eliminate?
used to eliminate molecules with large molecular weights (MW > 15,000 Dalatons, ex. immunoglobulins)
What do plasmapheresis and exchange transfusion remove?
plasma proteins
benefit of removing protein-bound molecules, digoxin-digoxin antibodies complexes, thyroxine
Risks with plasmapheresis and exchange transfusion?
infections and allergic reactions (replacement of plasma)
plasmapheresis and exchange transfusion:
-cheap or expensive
obvs expensive man
plasmapheresis and exchange transfusion:
which one is ok in small infants or neonates
exchange transfusion
Define plasmapheresis
Plasmapheresis is a process that filters the blood and removes harmful antibodies. It is a procedure done similarly to dialysis; however, it specifically removes antibodies from the plasma portion of the blood.
Define exchange transfusion
Exchange transfusion is a potentially life-saving procedure that is done to counteract the effects of serious jaundice or changes in the blood due to diseases such as sickle cell anemia. The procedure involves slowly removing the person’s blood and replacing it with fresh donor blood or plasma.
How does “lipids rescue” work?
inject liposomes into system, lipophilic compounds will be sequestered and the toxicity will decrease because they will be trapped in liposome
What drugs is “lipids rescue” shown to be effective for?
- local anesthetics (lidocaine, bupivacaine)
- TCA
- calcium channel blockers
