Noradrenaline: friend or foe?

Area of Science:

• Critical care medicine
• Cardiovascular physiology
• Pharmacology

Background:

• Systemic hypotension is common in septic shock, systemic inflammation, and vasodilated states, often persisting despite fluid resuscitation.
• Norepinephrine (NE) is a vasopressor used to increase arterial pressure, but concerns exist about its potential to impair renal and visceral blood flow.
• Vasodilated states may involve impaired peripheral vascular responsiveness, suggesting NE might have different effects than in normal circulatory conditions.

Purpose of the Study:

• To evaluate the effects of norepinephrine (NE) on organ perfusion, particularly renal and visceral blood flow, in patients with vasodilated states.
• To address the clinical fear that NE administration negatively impacts visceral organ function.
• To determine if NE can improve organ perfusion pressure and subsequent organ function in conditions like septic shock.

Main Methods:

• Review of animal studies demonstrating NE's positive effects on GFR and renal blood flow.
• Analysis of physiological data showing NE increases renal blood flow independent of pressure effects in endotoxin models.
• Examination of patient series and clinical experience in septic and cardiac patients receiving NE for vasodilatation.

Main Results:

• Animal data suggest NE improves GFR and renal blood flow by increasing perfusion pressure.
• Physiological analysis indicates NE can increase renal blood flow even after controlling for pressure effects.
• Clinical observations and patient series report positive effects of NE on GFR and urine output.
• Clinical experience shows NE positively impacts coronary blood flow in vasodilated patients.

Conclusions:

• Norepinephrine (NE) may improve visceral organ blood flow in vasodilated states by selectively increasing organ perfusion pressure.
• Concerns about NE impairing renal and visceral blood flow appear unfounded in vasodilated conditions.
• When used appropriately after adequate fluid resuscitation and with normal/increased cardiac output, NE is likely beneficial for organ perfusion.