Lecture 13: Poisoning due to Cardiovascular Drugs Flashcards
What is the therapeutic role of Beta-blockers (3)
- Competitively inhibits catecholamines at Beta1 receptors on heart
- Slows heart rate
- Reduces myocardial contractility
What is a negative chronotropic effect
slowing of heart rate
What is a negative ionotropic effect
reduction of myocardial contractility
What are Beta-blockers used in the treatment of (3)
- hypertension
- angina
- tachyarrhythmias
What is a tachyarrythmia?
abnormal fast heart rate due to electrical problems with the heart
Beta-blocker poisoning features (3)
- bradycardia
- hypotension
- cardiorespiratory arrest
What is bradycardia
slow heart rate with pulse less than 50 beats per minute
What is hypotension
systolic pressure below 100mmHg
What effects whether Beta-blockers can cross the BBB and cause CNS effects
how lipophillic the drug is
CNS effects due to Beta-blockers (4)
- drowsiness
- coma
- convulsions and seizures
- delirium and hallucinations
Beta-blocker poisoning management (3)
- symptomatic and supportive care
- reducing absorption
- glucagon
What is symptomatic and supportive care for Beta-blocker poisoning (3)
- A-B-C
- monitor pulse, BP and cardiac rhythm
- treat convulsions with diazepam
How do you reduce absorption of Beta-blockers
- AC if patient presents within 1 hour of potentially life-threatening OD
How is glucagon used as a specific treatment for Beta-blocker poisoning
- increases intracellular cAMP which mediates a beta-stimulant effect on the heart
- glucagon to the heart bypasses the blocked Beta-receptor
- gets around negative ionotropic and chronotropic effect
What 3 types of cells do calcium channel blockers block the inward passage of calcium through voltage gated channels
- Myocardial cells
- Cardia conducting cells
- Vascular smooth muscle cells in arteries
What 3 effects do calcium channel blockers have
- Reduction in contraction
- Reduction in heart rate
- Vasodilation
Features of calcium channel blocker poisoning (4)
- negative inotropic effect
- negative chronotropic effect
- vasodilation
- confusion
Specific measures for calcium channel blocker poisoning
- IV calcium salts
- Beta-stimulating inotropes
- glucagon
- high does insulin/ dextrose
- IV lipid solution
How does IV lipid solution overcome calcium channel blocker poisoning
- calcium channel blockers are lipophilic
- adding large amount of lipid solution to patient will pull lipophilic calcium channel blocker away from target calcium cells
What does digoxin do
- causes hyperkalaemia by inhibiting Na+/K+ ATPase
Therapeutic effects of digoxin (2)
- positive inotropic effect
- negative chronotropic effect
What is digoxin used in treatment of (2)
- Atrial arrhythmia
- heart failure
Cardiac features of digoxin poisoning (4)
- sinus bradycardia
- Atrio-ventricular block
- Atrial/ ventricular arrhythmias
- cardiac arrest
