Noradrenaline , together with adrenaline, is a naturally occurring sympathetic neurotransmitter. When administered therapeutically, the drug exerts its principal effects at alpha1, alpha 2 and beta 1 receptors where it is both a potent inotrope and vasoconstrictor. The clinical effects of the drug are to increase contractility, blood pressure and afterload and to lower the pulse rate. The drug has enjoyed a resurgence in popularity in recent years when used in combination with a phosphodiesterase inhibitor or, in isolation, as therapy for 'Low Systemic Vascular Resistance Syndrome' following cardiopulmonary bypass. When used in the treatment of 'Low Systemic Vascular Resistance Syndrome', noradrenaline is less likely to precipitate lactic acidosis than adrenaline 5 .
Adrenaline is the second of the naturally occurring sympathetic neurotransmitters.
The clinical effects of the drug are to increase contractility, blood pressure, afterload and pulse rate. The drug is the most useful 'general purpose' sympathomimetic amine. They are also direct-acting venous and arterial vasodilators and for this reason are also classified as 'inodilators'. The vasodilatation of the PDEIs is especially marked in the pulmonary circulation and the drugs are particularly useful if reduction of PVR is required. Unlike the sympathomimetic agents, they tend not to increase myocardial VO2.