Ionotrops 3

mechanism of ction inotropes

1. ionotropEs Dr. Mohammed Minnathullah

2. Vasoactive drugs Vasopressors Ionotropes Increase the force of contraction of myocardial muscle Positive ionotropism Stimulates smooth muscle contraction of the capillaries & arteries Vasoconstriction Rise in Mean Blood Pressure Improved tissue perfusion and oxygenation

3. VASOPRESSORS ↑MAP = CO x ↑SVR ~ 1 ↓r 4 HR x SV PRELOAD CONTRACTILITY AFTERLOAD NORADRENALINE VASOPRESSIN

4. IONOTROPES ↑MAP = ↑ CO xSVR ~ 1 r 4 HR x ↑ SV PRELOAD ↑ CONTRACTILITY AFTERLOAD DOPAMINE DOBUTAMINE ADRENALINE

5. RECEPTOR LOCATION ACTION on stimulation  1 &  2 Vascular smooth muscle Myocardium Increase systemic & pulmonary vascular resistance Increase contractility Decrease rate  1 Myocardium + ve Ionotropism + ve Chronotropism  2 Bronchi Blood vessels Bronchodilation Vasodilation

6. b 1 adrenergic receptors function through G s to stimulate the effector adenylylcyclase to produce the 2 nd messenger cyclic AMP  Ca 2+

7. Medication SVR HR PCW MAP Dopamine ↓ ↑ ↑ ↑ ↑ ↓ ↑ ↓ ↑ Dobutamine ↓ ↑ ↑ ↑ ↓ ↓ ↔ ↑ Epinephrine ↓ ↑ ↑ ↑ ↓ ↑ ↑ Milrinone / Inamrinone ↓ ↓ ↑ ↓ ↓ Isoproterenol ↓ ↓ ↑ ↑ ↑ ↑ ↓ ↓ ↑ Norepinephrine ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ Phenylephrine ↑ ↑ ↔ ↑ ↑ ↑ Vasopressin ↑ ↑ ↔ ↑ ↑ ↑ ↑ Nesiritide ↓ ↔ ↓ ↓ ↓

8. α 1 and α 2 stimulation result in increased systemic and pulmonary vascular resistance . Cardiac a 1 -receptors increase contractility and decrease the heart rate Β 1 stimulation results in increased contractility ( inotropy ), heart rate ( chronotropy ), and conduction ( dromotropy ) Β 2 stimulation results in peripheral vasodilation and bronchodilation

9. Inotropes with vasoconstrictive ( α ) properties can be combined with vasodilators to improve contractility while avoiding an increase in SVR (e.g., norepinephrine with nitoprusside ) Inotropes with vasodilator properties can be combined with α -agonists to maintain SVR (e.g. milirinone with neosynephrine or norepinephrine ) Catecholamines can be combined with the PDE inhibitors to provide synergistic inotropic effects while achieving pulmonary and systemic vasodilation (e.g., epinephrine with milrinone )

10. Thank You!