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Year 4 - Toxicology > Lecture 3 - General Methods for Treatment of ODs > Flashcards

Lecture 3 - General Methods for Treatment of ODs Flashcards

1
Q

List some ways that we can prevent absorption

A

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

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2
Q

Use syrup of ____ for emesis

A

Ipecac

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3
Q

What dose of Ipecac for emesis?

A

7% (10-30 mL)

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4
Q

What are some CI to Ipecac for emesis?

A

drowsiness, coma, convulsions, no gag reflex, corrosive/caustic agents

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5
Q

What are some complications to Ipecac for emesis?

A
  • aspiration pneumonitis
  • bleedings
  • GI tract rupture
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6
Q

gastric lavage

A

stomach pumping

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7
Q

When is gastric lavage indicated?

A

only when you’re sure there’s still drug in the stomach that can be pumped out

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8
Q

What are some CI to gastric lavage?

A
  • corrosive/caustic agents

- petroleum distillate

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9
Q

gastric lavage - must protect ______

A

airways

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10
Q

What are some complications of gastric lavage?

A
  • cardiac arrhythmias
  • low pO2
  • laryngospasm
  • pharyngeal injury
  • esophageal or gastric perforation
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11
Q

Gastric Lavage Technique:

______ diameter tube possible

A

largest

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12
Q

Gastric Lavage Technique:

Position of patient

A

supine on left-side, with head down below level of stomach

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13
Q

Gastric Lavage Technique:

Airway should be protected with ?

A

a cuffed endotracheal tube

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14
Q

Gastric Lavage Technique:

Why do you save the aspirate?

A

for analysis to see what the cause is

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15
Q

Gastric Lavage Technique:

Describe the rest

A
  • 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)
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16
Q

Describe activated charcoal

  • how it works
  • what it does
A
  • 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
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17
Q

What are activated charcoal indications?

A

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
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18
Q

Why are corrosive agents not an indication for activated charcoal ?

A

corrosive agents are very ionized

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19
Q

contraindications to activated charcoal?

A
  • ingestion of caustic substances

- presence of ileum or bowel obstruction

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20
Q

what does caustic substance mean?

A

caustic or corrosive substances cause tissue damage through a chemical reaction

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21
Q

What are complications of activated charcoal?

A
  • 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)
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22
Q

How is activated charcoal administered?

A

orally or by gastric tube

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23
Q

Dose of activated charcoal for adults

A

30-100 g as a slurry in water (usually 20-30 g charcoal in 240 mL water)

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24
Q

Dose of activated charcoal for children

A

<10 years: 1-2 g/kg

10-12 years: 15-20 grams

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25
Q

Some formulations of activated charcoal contain sorbitol. What is it’s purpose?

A

sweetener but also a cathartic (will accelerate defecation)

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26
Q

MDAC

A

multiple-dose activated charcoal

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27
Q

MDAC may help prevent _____ of drug in the GIT

A

reabsorption

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28
Q

MAD increases ____ of drugs excreted with the feces

A

clearance

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29
Q

Describe gastrointestinal dialysis

A

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.

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30
Q

Dosing of MDAC in adults

A

25 g/2h

50g/4-6h

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31
Q

Dosing of MDAC in children

A

1-2 g/kg dose q2-4h

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32
Q

What is MDAC efficacious for?

A

analgesics, antiarrhythmics, benzos, BB, TCA, NSAID, etc.

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33
Q

2 types of Catharsis

A

1) whole-bowel irrigation

2) cathartics

34
Q

What are some indications for whole-bowel irrigation indications?

A
  • ingestion of iron or zinc salts
  • ingestion of sustained release medications
  • ingestion of drug packets “body packers”
  • ingestion of “crack” virals “body suffers”
35
Q

What are some CI to whole-bowel irrigation?

A
  • uncooperative patients
  • presence of ileum or GI obstruction
  • GI bleeding or perforation
36
Q

What are some complications to whole-bowel irrigation?

A
  • abdominal cramping
  • vomiting
  • profuse diarrhea
  • hyperchloremia - essential to monitor electrolytes
37
Q

Describe the technique of whole-bowel irrigation

A

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)

38
Q

Dose for whole-bowel irrigation for those > 5 years old

A

Colyte, 1-2 L/h, orally or via gastric tube

39
Q

Dose for whole-bowel irrigation for those < 5 years old

A

150-500 mL/h

40
Q

Describe cathartics (increase defecation)

A
  • 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
41
Q

List 3 cathartics

A

1) Sorbitol
2) Magnesium citrate
3) Magnesium or sodium sulfate

*doses on slide 20

42
Q

Describe dilution

A
  • 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
43
Q

How can we enhance elimination?

A
  • diuresis
  • peritoneal dialysis
  • MDAC
  • hemodialysis
  • hemoperfusion
  • hemofiltration
  • plasmapheresis and exchange transfusion
44
Q

Indications for enhancement of elimination

A
  • 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
45
Q

Diuresis is a manipulation of ___

A

pH

46
Q

What is the objective of diuresis?

A

Objective is to increase renal clearance

47
Q

When will diuresis work?

A

Only if poison or its active metabolites are excreted in urine

48
Q

Diuresis is based on what concept?

A

ion trapping

49
Q

Describe alkaline diuresis

A

give NaHCO3 IV to increase urinary pH to 7-8

-increases renal excretion of salicylate, isoniazid, and phenobarbital

50
Q

Describe acid diuresis

A

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

51
Q

What is forced diuresis?

A

Volume expansion with sodium-containing solutions (valid if glomerular filtration is an important determinant of excretion)

52
Q

What are risks of forced diuresis?

A

Volume overload manifested by pulmonary and cerebral edema

53
Q

Give an example of a drug for forced diuresis

A

furosemide, 10-40mg IV

54
Q

What must you monitor in forced diuresis??

A

electrolytes, fluid balance, acid-base balance, and response to diuretic

55
Q

Risks of giving furosemide?

A

metabolic acidosis and hypokalemia

56
Q

What type of compounds can peritoneal dialysis enhance the elimination of?

Give examples

A
  • water soluble
  • low MW (< 500 daltons)
  • low protein binding
  • low Vd

ex. alcohols, lithium, salicylates and theophylline

57
Q

Problem with peritoneal dialysis?

A

too slow!

rarely used

58
Q

Describe the thought process behind MDAC (“gastrointestinal dialysis”)

A

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”

59
Q

When is MDAC (“gastrointestinal dialysis”) effective?

A

In overdoses of phenobarbital, theophylline, and valproic acid

60
Q

peritoneal dialysis uses a _____ membrane

A

physiologic

61
Q

hemodialysis uses a ______ membrane

A

semipermeable

62
Q

What is required when doing hemodialysis ?

A

anticoagulation with heparin is required

63
Q

in poisoned patients, how long is HD usually performed for?

A

for 4-8 hours

64
Q

When is hemodialysis indicated?

A
  • 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)
65
Q

What are complications of hemodialysis?

A
  • clotting and leaking of blood from around connections (thrombosis, bleeding)
  • embolus (rare)
  • hypotension
  • convulsions
  • arrhythmias
  • infections
66
Q

Describe charcoal hemoperfusion

A
  • 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
67
Q

complications of charcoal hemoperfusion?

A

Similar to that of hemodialysis:

  • clotting and leaking of blood from around connections (thrombosis or bleeding)
  • embolus (rare)
  • hypotension
  • convulsions
  • arrhythmias
  • infections
68
Q

what is hemofiltration?

A
  • 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
69
Q

What are some advantages of hemofiltration?

A
  • 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)
70
Q

What are some disadvantages of hemofiltration?

A
  • 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
71
Q

look at charts on page 36-37

A

okay

72
Q

What is plasmapheresis and exchange transfusion used to eliminate?

A

used to eliminate molecules with large molecular weights (MW > 15,000 Dalatons, ex. immunoglobulins)

73
Q

What do plasmapheresis and exchange transfusion remove?

A

plasma proteins

benefit of removing protein-bound molecules, digoxin-digoxin antibodies complexes, thyroxine

74
Q

Risks with plasmapheresis and exchange transfusion?

A

infections and allergic reactions (replacement of plasma)

75
Q

plasmapheresis and exchange transfusion:

-cheap or expensive

A

obvs expensive man

76
Q

plasmapheresis and exchange transfusion:

which one is ok in small infants or neonates

A

exchange transfusion

77
Q

Define plasmapheresis

A

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.

78
Q

Define exchange transfusion

A

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.

79
Q

How does “lipids rescue” work?

A

inject liposomes into system, lipophilic compounds will be sequestered and the toxicity will decrease because they will be trapped in liposome

80
Q

What drugs is “lipids rescue” shown to be effective for?

A
  • local anesthetics (lidocaine, bupivacaine)
  • TCA
  • calcium channel blockers

Year 4 - Toxicology (24 decks)

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