Cardio clinical Flashcards
(18 cards)
How do cardiac glycosides (cardenolides e.g. digoxin) cause toxicity?
Inhibit the Na/K pump which increases intracellular sodium. This is then exchanged for calcium instead. Excess intracellular calcium is bound by the sarcoplasmic reticulum and used to increase contractions
What clinical signs do you see with cardiac glycoside toxicity?
Arrhythmias
Also extracardiac signs - vomiting, anorexia, lethargy
How do you treat cardiac glycoside toxicity?
Can induce vomiting and give activated charcoal if not clinical
Intralipid and cholestyramine
FAB fragments
Treat arrhythmias
Monitor K+ and treat if hyperkalaemic
Apart from cardiac glycosides, what other toxins can inhibit the Na/K ATPase pump (name 5)?
- Foxgloves (digitalis purpurea)
- Fireflies - needs to eat 1 firefly/kg
- Lily of the valley (convallaria majalis)
- Toads (Bufo toads - rhinella and incilius)
- Oleander
How does albuterol cause cardiac toxicity?
Non-selective beta agonist - causes beta 2 stimulation and tachycardia
How do you treat albuterol toxicity?
Emesis and activated charcoal if not showing clinical signs
IV fluids
Non-selective beta blocker (propranolol) if tachycardic
What change on biochemistry might you see with albuterol toxicity?
Hypokalaemia due to shift of potassium intracellularly - supplement if <2.5 after treatment as may predispose further to ventricular arrhythmias
What plants contain grayanotoxins (name 3).
- Laurel plants (kalmia)
- Rhodedendrons
- Pieris
How do grayanotoxins cause cardiotoxicity?
Bind to sodium channels in cell membranes and increase their permeability = increased and prolonged depolarisation.
Therefore NEGATIVE chronotrope - bradycardia.
What clinical signs would you see with grayanotoxin ingestion?
Bradycardia - weakness, collapse, lethargy
If severe may cause sinus arrest
How do you treat grayanotoxin ingestion?
NB rarely eat enough to cause this.
Emesis and activated charcoal if not clinical.
Anti-arrhythmic Tx
How do imidazoline decongestants cause cardiac toxicity?
They are sympathomimetics - primarily act on alpha-adrenergic receptors
What are some clinical signs seen with imidazoline decongestant ingestion? How quickly do these occur?
Occur in 30mins-4h post ingestion
Bradycardia, lethargy/weakness, vomiting, coma
How do you treat imidazoline decongestant ingestion?
Antagonise alpha-2 with atipamezole/yohimbine
What can happen if you give oxygen supplementation to a patient with paraquat toxicity?
Increases oxidative injury to lungs
How does paraquat ingestion lead to pulmonary fibrosis?
Paraquat ingested and absorbed from GIT - actively transported to pneumocytes and accumulates here. Undergoes an NADPH dependent reaction here, then reacts with O2 to form a radical -> damages cell membranes and leads to cell death.
Lung then repairs by fibrosis
What clinical signs do you see in paraquat toxicosis?
Initially vomiting
Raised liver and kidney values in 48-72h
Concentrates in lung in 4-5d
Longterm pulmonary fibrosis - crackles, dyspnoea, wheezing
How do you treat paraquat toxicosis?
Emesis and AC initially
Haemodialysis = best prognosis
If PF - no Tx
