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Inotropes in Cardiac Surgery. Basics. Cardiac Cycle. Phase 1 - Atrial Contraction Phase 2 - Isovolumetric Contraction Phase 3 - Rapid Ejection Phase 4 - Reduced Ejection Phase 5 - Isovolumetric Relaxation Phase 6 - Rapid Filling Phase 7 - Reduced Filling. Sympathetic / Parasympathetic.
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Cardiac Cycle • Phase 1 - Atrial Contraction • Phase 2 - Isovolumetric Contraction • Phase 3 - Rapid Ejection • Phase 4 - Reduced Ejection • Phase 5 - Isovolumetric Relaxation • Phase 6 - Rapid Filling • Phase 7 - Reduced Filling
BEFORE INOTROPES • Fluid • Bolus • Legs up • Rhythm • ECG, SR, slow, fast, paced on ventricle, ST’s, ectopics • Tamponade • CVP, BE, UO, temp, CXR, echo • Bleeding • Drains, CXR, Hb • Pneumothorax • CXR, examine, vent alarms • Fight Ventilator • Paralyse, sedate or extubate
Which Inotrope • Ohms Law • V=I x R • BP=CO x SVR • Simple terms • Low or high cardiac output, what is the PA pressure
Inotropes • Atropine • Ca2+ • Dopamine • Dopexamine • Dobutamine • Adrenaline • Noradrenaline • Isoprenaline • Enoximone • Aminophylline • Vasopressin • Methylene blue • NO
Atropine • Antimuscurinic ie causes tachycardia • Some pateints have muscurinic receptors on ventricle as well ie inotropic • Increases HR • CO=SV x HR
Ca2+ • Inotrope and vasoconstrictor • Short acting • Beware radial artery patients • Warn patient if awake
Dopamine • Acts on dopamine receptors on heart and kidney • Causes a tachycardia (CO=SV x HR) • Increases urine output in some patients • Less metabolic side effects compared with adrenaline • Beware patients with tachycardia (give k+, Mg2+)
Dopexamine • Tachycardia • Increase splanchnic and renal blood flow • VASODILATOR • Beware • Vasodilated patients
Dobutamine • Like dopamine • Has less effect on pulmonary artery pressure good for mitral valve patients
Adrenaline • Excellent inotrope but dirty • Increased heart rate and inotropy (ß1-adrenoceptor mediated) • Vasoconstriction in most systemic arteries and veins (postjunctional a 1 and a 2 adrenoceptors) • Vasodilation in muscle and liver vasculatures at low concentrations (b2-adrenoceptor); vasoconstriction at high concentrations (a1-adrenoceptor mediated)
Noradrenaline • Vasoconstrictor • Increased heart rate and increased inotropy (ß1-adrenoceptor mediated) • Vasoconstriction occurs in most systemic arteries and veins (postjunctional a 1 and a 2 adrenoceptors) • Ask can I wake patient up to avoid Norad • Must have a good cardiac output
Isoprenaline • Causes tachycardia and vasodilatation • Good in patients with high PA pressures • Beware vasodilated patients
Enoximone Phosphodiesterase Inhibitor Good in patients with high PA pressure “2nd line when adrenaline having no effect “receptor dissociation”
Aminophylline • Phosphodiesterase inhibitor • Main effect on lung compared to heart • Good in patients who have hypoxic vasoconstriction “short fat little smoker with poor urine output”
Vassopresin • 2nd line vasoconstrictor • Most powerful available • Associated with organ ischaemia
Methylene blue • Whatever the mechanism the final step of vasodilatation is NO • Methylene blue inhibits NO synthesis
What else • IABP • LVAD • RVAD • BVAD