28: Inotropic drugs and vasopressors Flashcards
Define shock
Shock is characterised by inadequate organ perfusion to meet oxygen demands of a tissue, leading to organ dysfunction
What are the four categories of shock? Give examples of each.
Hypovolemic - haemorrhage, dehydration
Cardiogenic - heart failure
Distributive - sepsis, anaphylaxis
Obstructive - cardiac tamponade, PE
What are the clinical features of shock?
- Unwell - ITU, HDU, central line, IV lines, urinary catheter, cardiac/O2 monitor
- Hypotension/hypovolemia
- LV impairment
- Changes in vascular resistance
- Poor renal/peripheral perfusion
- Confused/sedated
What are the goals of shock resuscitation?
- Restore blood pressure - ensure euvolemic
- Normalise systemic perfusion - inotropes, vasopressors
- Preserve organ function - renal perfusion
- Treat underlying cause - antibiotics, relieve tamponade
What is the rationale behind using inotropic agents in shock?
Inc CO improves global perfusion
What is the risk of using inotropic agents in shock?
Tachycardia and inc. myocardial O2 consumption can exacerbate myocardial ischaemia
What is the first choice vasopressor?
Norepinephrine
What is epinephrine used for?
Cardiac arrest and anaphylaxis
What kind of agonist is epinephrine?
Mixed alpha and beta
What kind of agonist is dobutamine
B1 agonist
What kind of agonst is dopamine?
Depends on dose
- Low: inc. renal blood flow
- Med: Beta effects
- High: alpha effects
Dopamine is the metabolic precursor of ____
Norepinephrine
What are the side effects of:
- alpha agonism
- alpha and beta agonism
Alpha - ischaemia
Alpha and beta - inc cardiac work, cardiac ischaemia, arrhythmias
What is the mechanism of phosphodiesterase inhibitors?
- Positive inotrope
- Prevent breakdown of cAMP leading to PK activation and inc. Ca flux
What are the side effects of phosphodiesterase inhibitors?
- Thrombocytopenia
- Hypotension
- Arrhythmias
- Mortality
What is the mechanism of Ca sensitisers? what is their use?
- Enhances troponin sensitivity to Ca
- Used in heart failure
What is digoxin used for?
Acute heart failure with fast atrial fibrillation
What is the mechanism of digoxin
- Inhibit Na/K/ATPase on cardiac myocyte, inc. Ca flux into cell
- Increase activity of vagus nerve at AV node
What is a predisposing factor to digoxin toxicity?
Hypokalemia
What are side effects of digoxin?
Cardiac
- Arrhythmias
- ECG changes
Non cardiac
- Nausea/vomiting/anorexia/diarrhoea
- Abdominal pains
- Fatigue
- Visual complaints
- Muscular weakness
- Dizziness
- Dreams
What are some drug interactions of digoxin
Ca channel blockers - verapamil, diltiazem
Anti arrhythmics - amiodarone, quinidine
Antibiotics - erythromycin, cyclosporin
What are the first and second line treatments for AF?
1st: beta blockers
second: diltiazem
