The administration of norepinephrine in patients receiving cyclopropane and halothane anaesthesia may increase cardiac irritability and may lead to arrhythmia. If pressor drug is needed during the usage of general anesthetic drugs, it is recommended to give a drug with minimal effect of cardiac stimulation eg, methoxamine or phenylephrine. If arrythmia occurs, β-adrenergic blocking agents eg, propranolol, should be given. It should be considered that digitalis also can increase sensitivity of myocardium to the effect of sympathomimetic drugs. The same type of cardiac arrhythmias may result from the use of norepinephrine in patients with severe hypoxia or hypercarbia. Norepinephrine should be used with extreme caution in patients receiving monoamine oxidase inhibitors (MAOIs) or antidepressants of the triptyline or imipramine types, because severe, prolonged hypertension may result.
The administration of furosemide or other diuretics may reduce the ability of artery to give response to pressor agents eg, norepinephrine.