Date post: | 19-Jan-2016 |
Category: |
Documents |
Upload: | avice-osborne |
View: | 223 times |
Download: | 0 times |
INOTROPES IN CARDIOTHORACIC SURGERY
Objectives
Introduction Classification of inotropes Postoperative myocardial dysfunction. Choice of inotrope Indications in specific settings
INTRODUCTION
What is inotrope?
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
Why inotropes?
Maintenance of adequate oxygen balance is one of the primary objectives when dealing with patients undergoing cardiac surgery.
Cardiac output is one of the major components of oxygen delivery .
Introduction (cont.)
Due to preoperative cardiac lesion and myocardial dysfunction secondary to the events related to cardiac surgery and cardio pulmonary bypass, circulatory support by pharmacological means is frequently required after surgery.
Introduction (cont.)
How do inotropes act?
Adrenergic receptors
α- receptors
α1α2
β-receptors
β1 β2
Introduction(cont.)
CLASSIFICATION OF INOTROPIC AGENTS
Classification of inotropic agentscAMP
dependent agents
adrenergic agonists
dopaminergic agonists :
phosphodiesterase III isoenzyme inhibitors:
cAMP independent
inotropic agentsNa+-K+-ATPase
inhibitors :
Potassium channels inhibitors
Agonists of β- adrenergic receptors
Calcium
Phenylephrine
Other new agents
Calcium Sensitizers
vasopressin
natriuretic brain peptide
Norepinephrine
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)
Epinephrine 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)
Dopamine
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)
Dobutamine
β 1-adrenergic agonist Had positive inotropic and
peripheral vasodilative properties.
As established dobutamine as a first line therapeutic choice in patients with decompensated HF.
Dose : 2.5-10 µg/kg/min
Phosphodiesterase (PDE) inhibitors 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.
Levosimendan It is one of calcium senstizers It act by increasing the sensitivity of
contractile apparatus (especially troponine-T) to intracellular calcium.
Proarrhythmic activity less common. Induce peripheral, pulmonary and coronary
vasodilatation, via ATP-sensitive potassium channels
Dose : is 6 to 12 µg/kg loading dose over 10 minutes followed by 0.05 to 0.2 µg/kg/min as a continuous infusion.
POSTOPERATIVE MYOCARDIAL DYSFUNCTION
Postoperative myocardial dysfunction
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 the systolic myocardial performance after heart surgery in patients undergoing cardiopulmonary bypass (CPB)
CHOICE OF INOTROPE
Choice of inotrope
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 several studies.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.
Ideal positive inotrope?!!
Enhance contractility without any significant increase in heart rate preload, afterload, and myocardial oxygen consumption.
Choice of inotropes(cont.)
Ideal positive inotrope?!!
Enhance the diastolic function
Choice of inotropes(cont.)
Ideal positive inotrope?!!
Maintain the diastolic coronary perfusion pressure and thus an adequate myocardial blood flow.
Choice of inotropes(cont.)
Ideal positive inotrope?!!
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.)
Now , what will you choose?
Dopamine
Dobutamine
Epinephrine
Norepinephrine
PDE inhibitor
s
Levosimendan
Indications in specific settings
Coronary artery bypass graft surgery:In most cases, no or only mild inotrope requirement.inotropes may be needed in case of preexisting ventricular dysfunction or in case of unsuccessful revascularization if the intra-aortic balloon pump alone is not enough.
emergency revascularization of acute myocardial infarction, dobutamine and PDE inhibitors.
off-pump coronary artery bypass graft surgery (dopamine, dobutamine)
Indications in specific settings(cont.)
Chronic heart failure :Combination therapy (i.e. a PDE inhibitor administered along with a beta-adrenergic inotrope, dobutamine or epinephrine) may therefore be the treatment of choice in these patients
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 and pulmonary vasodilation) and dopamine (to add further support whilst maintaining the systemic perfusion 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
Conclusion
Postoperative myocardial dysfunction is a major concern in the setting of cardiac surgery since it is extremely frequent and is related to a greater morbidity and mortality.
Inotropic drugs are nowadays an important therapeutic tools in the treatment of perioperative heart failure.
Good selection usually guide our outcome.
Any Question?