substance toxicity

Question 1

what precipitates lithium toxicity?

Answer 1

• dehydration
• renal failure
• diuretics (especially thiazides), ACEi/ARBs, NSAIDs and metronidazole.

Question 2

features of lithium toxicity?

Answer 2

coarse tremor (a fine tremor is seen in therapeutic levels)
hyperreflexia
acute confusion
polyuria
seizure
coma

Question 3

mx of lithium toxicity?
mild/moderate

Answer 3

IV fluids with isotonic saline, until euvolemic, then typically twice maintenance rate
monitor serum sodium closely (every 4 hours with serial lithium concentrations) if there is a concern about lithium-induced nephrogenic diabetes insipidus

Question 4

mx of lithium toxicity?
severe

Answer 4

haemodialysis

Question 5

what may trigger therophylline toxicity?

Answer 5

theophylline is metabolised by the cytochromes P450 enzymes located in the liver
acute illness and certain medications (e.g. ciprofloxacin, erythromycin) may inhibit these enzymes

Question 6

features of theophylline toxicity?

Answer 6

vomiting
agitation
dilated pupils
tachycardia
hyperglycaemia
hypokalaemia

Question 7

mx of theophylline toxicity?

Answer 7

antiemetics (e.g. ondansetron) should also be given
IV crystalloid for hypotension
correct hypokalaemia
benzodiazepines for seizures
IV beta-blockers for SVTs

definitive treatment is with haemodialysis

Question 8

features of digoxin toxicity?

Answer 8

generally unwell, lethargy, nausea & vomiting, anorexia, confusion, yellow-green vision
arrhythmias (e.g. AV block, bradycardia)
gynaecomastia

Question 9

key precipitating factor for digoxin toxicity?

Answer 9

hypokalaemia

Question 10

mx for digoxin toxicity?

Answer 10

Digibind
correct arrhythmias
monitor potassium

Question 11

MOA of digoxin?

Answer 11

Inhibits the Na+/K+ ATPase pump

Question 12

when should digoxin levels be measured?

Answer 12

If toxicity is suspected, digoxin concentrations should be measured within 8 to 12 hours of the last dose

Question 13

how do you prevent contrast-induced nephropathy?

Answer 13

IV 0.9% saline pre and post procedure

Question 14

what is the most common endocrine disorder developing as a result of chronic lithium toxicity?

Answer 14

hypothyroidism

Question 15

name an anti arrhythmic med which should be used with caution with digoxin?

Answer 15

Amiodarone may cause precipitation of digoxin toxicity - if starting amiodarone on a patient taking digoxin the dose should be reduced

Question 16

what antihypertensive is safe tp give someone taking lithium?

Answer 16

amlodipine

Question 17

what is the blood gas picture in salicylate overdose?

Answer 17

Early stimulation of the respiratory centre leads to a respiratory alkalosis whilst later the direct acid effects of salicylates (combined with acute renal failure) may lead to an acidosis. In children metabolic acidosis tends to predominate.

Question 18

features of salicylate overdose?

Answer 18

hyperventilation (centrally stimulates respiration)
tinnitus
lethargy
sweating, pyrexia*
nausea/vomiting
hyperglycaemia and hypoglycaemia
seizures
coma

Question 19

treatment of salicylate overdose?

Answer 19

general (ABC, charcoal)
urinary alkalinization with intravenous sodium bicarbonate - enhances elimination of aspirin in the urine
haemodialysis

Question 20

indications for haemodialysis in salicylate overdose?

Answer 20

serum concentration > 700mg/L
metabolic acidosis resistant to treatment
acute renal failure
pulmonary oedema
seizures
coma