tailieunhanh - Perioperative Critical Care Cardiology - part 7

Dobutamine sản xuất tăng co bóp cơ tim phụ thuộc vào liều lượng và các hiệu ứng chronotropic bằng cách kích thích thụ thể β1-adrenergic với một sự gia tăng tiếp theo trong nội bào adenosine monophosphate vòng | 168 G. Gemes Dobutamine Dobutamine produces dose-dependent inotropic and chronotropic effects by stimulation of p1-adrenergic receptors with a subsequent increase in intracellular cyclic adenosine monophosphate cAMP . While the short-term use of this substance is effective in improving hemodynamic parameters the longer-term use has been associated with tolerance partial loss of hemodynamic effects myocardial ischemia and increased mortality 20 . Dobutamine is indicated when there is evidence of peripheral hypoperfusion with or without congestion or pulmonary edema refractory to diuretics and vasodilators at optimal doses. In patients receiving p-adrenoceptor antagonist therapy dobutamine doses frequently have to be increased to restore its inotropic effect. Combinations of dobutamine with PDE inhibitors or levosi-mendan have been shown to have additive effects. Phosphodiesterase Inhibitors PDE inhibitors which include milrinone and enoximone increase intracellular cAMP by preventing cAMP degradation. This effect is independent of p1-adrenergic stimulation and is therefore still effective when downregulation of these receptors has occurred. PDE inhibitors however increase cytosolic calcium levels and therefore ultimately also increase myocardial oxygen demand and the incidence of arrhythmias 21 particularly in the presence of concomitant ischemia 22 . These detrimental side effects of treatment with catecholamines and PDE inhibitors are well known and have been associated with a possible negative influence on mortality. Particularly in the setting of AHF caused by myocardial ischemia the therapeutic concept of increasing myocardial contractility by increasing cytosolic calcium by stimulating the same intracellular cascade may therefore be challenged. Levosimendan Sensitization of cardiac myofilaments to calcium without further increasing intracellular calcium concentrations and myocardial oxygen demand 23 has recently evolved as an attractive .

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