inotropes in cardiothoracic surgery
TRANSCRIPT
Introduction Classification of inotropes Postoperative myocardial dysfunction. Choice of inotrope Indications in specific settings
An inotrope is an agent, which increases or decreases the force or energy of muscular contractions .
Positive inotropic agent enhances myocardial contractility so; cardiac output, the amount of blood ejected by the heart with each beat, will also increase.
Introduction
Maintenance of adequate oxygen balance is oneof the primary objectives when dealing withpatients undergoing cardiac surgery.
Cardiac output is one of the major components ofoxygen delivery .
Introduction (cont.)
Due to preoperative cardiac lesion and myocardialdysfunction secondary to the events related tocardiac surgery and cardio pulmonary bypass,circulatory support by pharmacological means isfrequently required after surgery.
Introduction (cont.)
Adrenergic receptors
α-receptors
α1 α2
β-receptors
β1 β2
Introduction(cont.)
Classification of inotropic agents
cAMP dependent agents
adrenergic agonists
dopaminergicagonists:
phosphodiesteraseIII isoenzyme
inhibitors:
cAMP independent inotropic agents
Na+-K+-ATPaseinhibitors:
Potassium channels inhibitors
Agonists of β-adrenergic receptors
Calcium
Phenylephrine
Other new agents
Calcium Sensitizers
vasopressin
natriuretic brain peptide
principal neurotransmitters in the sympathetic nervous system
potent α- adrenoceptor agonist strong vasoconstrictor
norepinephrine stimulates β1-adrenoceptors, increases both heart rate and contractility.
Norepinephrine does not affect β2-adrenoceptors.
Dose : 2-20µg/min(0.04-0.4 µg/kg/min)
Hormone secreted by the adrenal medulla Potent α- and β-adrenoceptor agonist. so a powerful vasoconstrictor, a positive
inotrope, and a positive chronotrope. But, diastolic blood pressure may decrease as a
result of vasodilation due to stimulation of β2-adrenoceptor effects.
Dose : 2-20µg/min(0.04-0.4 µg/kg/min)
An endogenous catecholamine Stimulates both adrenergic and dopaminergic
(D1 and D2) receptors. Low-dose infusion (<5 µg/kg/min) Intermediate doses (5-10 µg/kg/min) . Higher doses (>10 µg/kg/min)
β 1-adrenergic agonist Had positive inotropic and
peripheral vasodilativeproperties.
As established dobutamine as a first line therapeutic choice in patients with decompensatedHF.
Dose : 2.5-10 µg/kg/min
Inodilators postreceptor” mechanism of
action oral administration . Milrinone. Dose : 50 µg/kg over 10 min , then
0.375-0.75 µg/kg/min ,max.: 1.13 mg/kg/min.
It is one of calcium senstizers It act by increasing the sensitivity of contractile
apparatus (especially troponine-T) tointracellular calcium.
Proarrhythmic activity less common. Induce peripheral, pulmonary and coronary
vasodilatation, via ATP-sensitive potassiumchannels
Dose : is 6 to 12 µg/kg loading dose over 10minutes followed by 0.05 to 0.2 µg/kg/min asa continuous infusion.
Causes: aortic cross-clamping inadequate myocardial protection hypothermia with cardioplegia and topical iced
solutions surgical trauma activation of the complement cascade by CPB reperfusion injury premature or excessive titration of inotropic
agents
Recovery pattern of cardiac function: postoperative changes in thesystolic myocardial performance after heart surgery in patientsundergoing cardiopulmonary bypass (CPB)
Guided The expected need for inotropes clinical evidence of depressed
myocardial function Empirical drug choice and
titration, with careful hemodynamic monitoring
Table 2. Predictive factors of inotropic support, as highlighted by severalstudies.Low ejection fraction (< 45%)
History of congestive heart failure
Cardiomegaly
High LVEDP following ventriculogram
MI within 30 days of operation*
Older age (> 70 years)
Longer duration of aortic cross-clamping
Prolonged cardiopulmonary bypass*
Urgent operation
Re-operation*
Female gender*
Diabetes mellitus
LVEDP = left ventricular end-diastolic pressure; MI = myocardial infarction.
* statistical significance for coronary artery bypass surgery only.
Choice of inotropes(cont.)
Enhance the diastolic function
Choice of inotropes(cont.)
Maintain the diastolic coronary perfusion pressureand thus an adequate myocardial blood flow.
Choice of inotropes(cont.)
It finally should have rapid titration times and onset of action and a short half-life
Choice of inotropes(cont.)
Catecholamines are the mainstay of current inotropic treatment
they can be divided into more potent (epinephrine, isoproterenol,
noradrenaline) and milder (dopamine, dopexamine, dobutamine
Choice of inotropes(cont.)
Dopamine
Dobutamine
EpinephrineNorepinephrine
PDE inhibitors
Levosimendan
Coronary artery bypass graft surgery:In most cases, no or only mild inotroperequirement.inotropes may be needed in case of preexistingventricular dysfunction or in case of unsuccessfulrevascularization if the intra-aortic balloon pumpalone is not enough.
emergency revascularization of acutemyocardial infarction, dobutamine and PDEinhibitors.
off-pump coronary artery bypass graft surgery (dopamine, dobutamine)
Indications in specific settings(cont.)
Chronic heart failure :Combination therapy (i.e. a PDE inhibitoradministered along with a beta-adrenergicinotrope, dobutamine or epinephrine) maytherefore be the treatment of choice in thesepatients
Indications in specific settings(cont.)
Diastolic dysfunction :No inotropes at all (or inotropes with a better effect on ventricular relaxation, such as PDE inhibitors, if systolic dysfunction coexists)
Indications in specific settings(cont.)
valvular surgeryModerately severe aortic stenosis,
Inotropic support is rarely needed
Indications in specific settings(cont.)
Chronic aortic insufficiency
Requiring adequate preload and inotropes
Indications in specific settings(cont.)
Mitral stenosis, chronic mitral regurgitation
Treatment with inotropes is warranted.
Indications in specific settings(cont.)
Acute aortic and mitral regurgitation
require aggressive inotropic support even preoperatively
Indications in specific settings(cont.)
Tricuspid regurgitation
Inotropes are beneficial
Indications in specific settings(cont.)
Orthotopic cardiac transplantation:Routine inotropic support includes isoproterenol(to increase the automaticity, inotropism andpulmonary vasodilation) and dopamine (to addfurther support whilst maintaining the systemicperfusion pressures).
Indications in specific settings(cont.)
Right ventricular dysfunction: heart transplantation, lung transplantation pulmonary thromboendoarterectomy left ventricular assist device implantation, inadequate myocardial protection
Indications in specific settings(cont.)
Successful management
Right ventricular afterload
The contractile strength
maintenance of the aortic blood
pressure
pulmonary vasodilators
inotropes :• dobutamine, •isoproterenol,• epinephrine, •PDE inhibitors
vasoconstrictors
Conclusion
Postoperative myocardial dysfunction is amajor concern in the setting of cardiac surgerysince it is extremely frequent and is related to agreater morbidity and mortality.
Inotropic drugs are nowadays an importanttherapeutic tools in the treatment ofperioperative heart failure.
Good selection usually guide our outcome.