Inotropic and vasopressor agents – The drugs mostused in the treatment of these patients are the sympathomimeticamines 30. They must be administered in thepresence of tissular hypoperfusion, after properly restoringthe intravascular volume.Norepinephrine must be the first-choice agent to beemployed whenever there is severe arterial hypotension(systemic systolic BP <70mmHg). Immediate reversion ofthese pressure levels is fundamental in the maintenance ofcoronary artery perfusion pressure, because of the interactionwith alpha and beta-adrenergic receptors. Its artery actionon beta-adrenergic receptors increases the myocardialcontractility and the velocity of conduction of the cardiacstimulus in the heart chronotropism. However, the alphaagonisteffect is predominant at the doses and for thepurpose norepinephrine is used for. Doses between 2 and15μg/kg/min cause peripheral vasoconstriction withsignificant increase in the total and regional systemic arterialresistance, with perfusion impairment of organs, such askidneys, bowel, lungs, skeletal muscles and skin. Reflexbradycardia may occur due to an increase in the meanpressure of the aorta and subsequent reduction in CO.In those situations where hypotension is not so significant,dobutamine is the agent of choice. This drug has theability to stimulate alpha-1 and beta-1 and 2 adrenergicreceptors. Its positive inotropic and chronotropic actions donot depend on endogenous release of norepinephrine likethose of dopamine. Dobutamine hemodynamic effects aredose-dependant. Doses up to 15μg/kg/min increase myocardialcontractility with no significant elevation of the heartrate, and also increase the diastolic coronary flow and thecollateral flow to ischemic areas 31,32.In general, there is reduction in the central venous andcapillary pulmonary pressures due to better heart performance,with no change, however, in pulmonary vascular resistance.Dobutamine doses higher than 30μg/kg/min mustbe avoided because they favor the appearance of ventriculararrhythmias, in addition to other undesirable side effects,such as the accentuated increase in myocardium oxygenconsumption. It should be stressed that dobutamine maypromote a reduction in peripheral arterial resistance andsystemic pressure through its interaction with vascularbeta-adrenergic receptors, which sometimes leads to itsassociation with other vasopressor drugs, such as norepinephrine.As previously mentioned, this drug must notbe prescribed to patients with severe arterial hypotension,particularly when one intends to adjust its dosage to pres
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