Inotropes & Vasopressors Flashcards
What are inotropes?
Agents that increase myocardial contractility (inotropy).
E.g. adrenaline, dobutamine, isoprenaline, ephedrine
What are vasopressors?
Agents that cause vasoconstriction leading to increased systemic and/or pulmonary vascular resistance.
E.g. noradrenaline, vasopressin, metaraminol, vasopressin, methylene blue
What are inodilators?
Agents with inotropic effects that also cause vasodilation leading to decreased systemic and/or pulmonary vascular resistance (SVR, PVR).
E.g. milrinone, levosimendan
What is adrenaline?
A sympathomimetic amine with both alpha and beta adrenergic stimulating properties.
Beta > alpha
What are the 2 key indications for adrenaline?
1) anaphylaxis
2) cardiac arrest
ALS adrenaline dose in anaphylaxis?
0.5ml 1:1000 IM
ALS adrenaline dose in cardiac arrest?
10ml 1:10,000 IV
or
1ml of 1:1000 IV
Where is adrenaline produced from?
Adrenal medulla
What makes up the adrenal gland?
1) outer cortex
2) inner medulla
What 2 hormones is the outer adrenal cortex responsible for secreting?
Cortisol & aldosterone
What 2 hormones is the inner adrenal medulla responsible for secreting?
Adrenaline & noradrenaline
Action & effects of adrenaline?
Acts on both alpha and beta receptors:
1) Increases both heart rate and contractility (b1)
2) Acts on β 2 receptors in skeletal muscle vessels, causing vasodilation
3) Causes vasoconstriction in the skin & kidneys (causes a narrow pulse pressure)
4) Increases cardiac output and total peripheral resistance
5) inhibits insulin secretion by the pancreas (α adrenergic)
6) stimulates glucagon secretion in the pancreas (β adrenergic)
7) stimulates glycogenolysis in the liver and muscle (α adrenergic)
8) stimulates glycolysis in muscle (α adrenergic)
9) stimulates ACTH
10) stimulates lipolysis by adipose tissue (β adrenergic receptors)
What is phentolamine?
a non-selective alpha-adrenoceptor antagonist.
Indications for phentolamine?
1) reverse vasoconstrictive effects of adrenaline e.g. in digital ischaemia (think local anaesthetic)
2) hypertensive crisis e.g. interaction of MAOIs with tyramine foods, pheochromocytoma
Effect of adrenaline on the pancreas?
1) Inhibits insulin secretion (action on α adrenergic receptors)
2) Stimulates glucagon secretion (action on β adrenergic receptors)
Effect of adrenaline on blood glucose?
Raises blood glucose by:
1) inhibiting insulin
2) stimulating glucagon release
3) stimulates glycogenolysis in the liver and muscle
4) stimulates glycolysis in muscle
5) stimulates ACTH
6) stimulates lipolysis by adipose tissue
How does adrenaline affect ACTH?
Increases ACTH (which then increases cortisol)
How can adrenaline affect potassium?
Causes hypokalaemia
2 key indications for noradrenaline?
1) Acute hypotension
2) On-going treatment of acute hypotension
What is vasopressin?
An endogenous hormone with a direct antidiuretic effect on the kidney.
Also known as antidiuretic hormone (ADH).
Where is ADH made/released?
Made in the hypothalamus.
Released from the posterior pituitary.
Give 3 physiological changes that trigger ADH release
1) an increase in plasma osmolarity (detected by osmoreceptors in the hypothalamus)
2) a reduction in blood volume
3) an increase in the levels of angiotensin II
Role of ADH/vasopressin in dehydration?
ADH increases water reabsorption by binding to V2 receptors, subsequently anchoring water channels (aquaporins to the apical membrane of cells in the collecting duct and DCT of the kidney.
1) When someone becomes dehydrated, the osmolarity of the extracellular fluid increases
2) ADH released from posterior pituitary
3) Water is reabsorbed at an increased rate at the level of the kidney
4) This acts to increase the intravascular fluid volume.
5) This increases BP through an increase in venous pressure, thereby boosting venous return to the heart, and increasing cardiac output.
Role of ADH in haemorrhagic shock?
ADH also acts as a vasoconstrictor targeting V1 receptors on vascular smooth muscle at high concentrations.
