Noradrenaline: Effects in Septic Shock

Noradrenaline, also known internationally as Norepinephrine (INN), is an endogenous catecholamine produced in the adrenal medulla and postganglial neurons of the sympathetic nervous system. As a pharmaceutical active substance (brand names Arterenol, Sinora, and generic preparations), noradrenaline is well established in emergency and intensive care medicine. According to international guidelines (Surviving Sepsis Campaign), it is the first-line vasopressor in septic shock and is also used in cardiogenic shock, neurogenic hypotension, and severe therapy-refractory hypotension.

In clinical practice, noradrenaline is administered as a continuous infusion through a central venous catheter and titrated under close hemodynamic monitoring. The goal of therapy is not a specific peak blood pressure, but rather adequate organ perfusion, typically measured by mean arterial pressure (MAP) and supplementary markers such as lactate or urine output. Its use requires experienced physicians with intensive care expertise, as incorrect dosing or extravasation can cause severe complications.

Mechanism of Action

Noradrenaline preferentially binds to alpha 1 adreceptors on smooth vascular muscle, leading to pronounced arterial and venous vasoconstriction. This increases systemic vascular resistance and mean arterial pressure. Additionally, beta 1 adreceptors on the myocardium are moderately activated, which slightly increases cardiac contractility and supports cardiac output. Alpha 2 and beta 2 effects are comparatively minor.

Compared to dobutamine (predominantly beta 1) and adrenaline (alpha and beta), noradrenaline pursues a focused strategy: pressure increase through vasoconstriction, less tachycardia, lower arrhythmia risk. Compared to phenylephrine (pure alpha 1 agonist), the additional beta 1 effect ensures that stroke volume does not decrease as much. This combination is particularly favorable in septic shock because pronounced vasodilation is the primary issue and cardiac output is often already elevated compensatorily.

The half-life after intravenous administration is short, approximately two minutes. Therefore, noradrenaline must be administered as a continuous infusion. Elimination occurs rapidly through catechol O methyltransferase (COMT) and monoamine oxidase (MAO). If the infusion is abruptly stopped, blood pressure drops within minutes.

Uses

• Septic shock, first-line vasopressor after adequate fluid resuscitation according to Surviving Sepsis Campaign
• Cardiogenic shock, often combined with an inotrope such as dobutamine or milrinone
• Neurogenic shock following spinal cord injury, vasodilation due to loss of sympathetic tone
• Anaphylactic shock, supplementing adrenaline therapy in persistent hypotension
• Peripheral hypotension during anesthesia, especially with neuraxial anesthesia and sympatholytic effects of some anesthetics
• Postoperative therapy-refractory hypotension, individualized indication in intensive care

Noradrenaline does not replace adequate fluid administration and does not treat underlying causes. In hypovolemic shock, fluid or blood loss must first be corrected. Antibiotics in sepsis, reperfusion in cardiogenic shock, or glucocorticoids in refractory shock remain essential.

Dosage and Administration

Initial dose: typically 0.05 to 0.1 µg per kg body weight per minute via infusion pump with central venous access. Increase in 0.05 µg increments according to blood pressure target, frequently mean arterial pressure (MAP) of 65 mmHg, individually higher in pre-existing hypertension.

Dosing range: usually 0.05 to 1.0 µg per kg body weight per minute. Higher doses (above 0.5 µg per kg per minute) often indicate therapy escalation, such as additional vasopressors like vasopressin, glucocorticoids in septic shock (hydrocortisone), or reevaluation of the differential diagnosis.

Administration: preferably via central venous catheter, because extravasation into surrounding tissue can cause severe necrosis. In prehospital emergency, noradrenaline can be given diluted peripherally, preferably for short-term bridging only.

Reduction: after stabilization reduce in small steps (0.02 to 0.05 µg per kg per minute every 10 to 30 minutes). Sudden cessation can cause rebound hypotension.

Side Effects

Common: tachycardia, headache, anxiety, tremor, pallor, sweating, nausea.

Hemodynamically relevant: hypertension with end-organ stress in overdose, peripheral vasoconstriction with reduced perfusion to extremities, abdominal organs, and kidney at excessive doses. Mesenteric hypoperfusion in particular can lead to ischemia.

Cardiac effects: bradycardia as a reflex response to rapid pressure increase, supraventricular and ventricular arrhythmias, increased myocardial oxygen consumption.

Local complications: extravasation with tissue necrosis, therefore central venous administration with functioning catheter is essential. Phentolamine locally established as an antidote for extravasation.

Metabolic: hyperglycemia, increased lactate values, hypokalemia. These changes can complicate sepsis monitoring.

Interactions

• MAO inhibitors (tranylcypromine, moclobemid, selegiline) and tricyclic antidepressants: markedly enhanced effect of noradrenaline, hypertensive crisis possible. Dose adjustment and close monitoring required.
• Halogenated inhalational anesthetics (halothane, isoflurane, sevoflurane): myocardial sensitization with arrhythmia risk during catecholamine administration.
• Beta blockers: relative enhancement of alpha effect with pronounced vasoconstriction and bradycardia.
• Alpha blockers (phentolamine, doxazosin, tamsulosin): weakened pressure effect.
• Theophylline: increased arrhythmia risk with combination.
• Vasopressin, adrenaline, phenylephrine, dobutamine: additive or opposing hemodynamic effects, targeted intensive care management.

Special Instructions

Pregnancy: data limited. Use possible when vitally indicated, ideally in a center with obstetric and intensive care experience. Breastfeeding: not relevant because oral bioavailability is low and use is intravenous in emergency situations.

Children: use established in pediatric intensive care, weight-adjusted with individual titration.

Comorbidities: caution in coronary artery disease, severe hypertension, hyperthyroidism, pheochromocytoma, severe peripheral arterial disease. In these situations, indication and dose require particularly careful consideration.

Monitoring: continuous ECG monitoring, invasive arterial blood pressure measurement, regular lactate and acid-base checks, urine output monitoring. Often central venous oxygen saturation (ScvO2) as a marker of organ perfusion.

Light protection: noradrenaline is light-sensitive, infusion lines and syringes should be protected, discoloration toward brown indicates decomposition and loss of efficacy.

You Might Also Be Interested In

• Dobutamine, beta 1 inotrope in cardiogenic shock
• Vasopressin, V1 agonist as second vasopressor in septic shock
• Adenosine, short-acting antiarrhythmic in supraventricular tachycardia
• Glucagon, in severe hypoglycemia and beta blocker overdose
• Dexamethasone, glucocorticoid in refractory septic shock

Frequently Asked Questions

Sources

• Gelbe Liste, Noradrenaline active substance profile
• BfArM, Federal Institute for Drugs and Medical Devices
• AWMF, Guidelines on Sepsis and Septic Shock
• Surviving Sepsis Campaign, International Recommendations