Noradrenaline and the kidney: friends or foes?

Abstract

Septic shock, systemic inflammation and pharmacological vasodilatation are often complicated by systemic hypotension, despite aggressive fluid resuscitation and an increased cardiac output. If the physician wishes to restore arterial pressure (>80-85 mmHg), with the aim of sustaining organ perfusion pressure, the administration of systemic vasopressor agents, such as noradrenaline, becomes necessary. Because noradrenaline induces vasoconstriction in many vascular beds (visibly in the skin), however, it may decrease renal and visceral blood flow, impairing visceral organ function. This unproven fear has stopped clinicians from using noradrenaline more widely. In vasodilated states, unlike in normal circulatory conditions, however, noradrenaline may actually improve visceral organ blood flow. Animal studies show that the increased organ perfusion pressures achieved with noradrenaline improve the glomerular filtration rate and renal blood flow. There are no controlled human data to define the effects of noradrenaline on the kidney, but many patient series show a positive effect on glomerular filtration rate and urine output. There is no reason to fear the use of noradrenaline. If it is used to support a vasodilated circulation with a normal or increased cardiac output, it is likely to be the kidney's friend not its foe.

Figure 1

The relationship between perfusion pressure and organ flow for the kidney and heart under the pathophysiologic conditions of hypertrophy or renovascular disease. Coronary perfusion pressure = diastolic arterial pressure – left ventricular end diastolic pressure. Renal perfusion pressure = mean arterial pressure – tissue pressure.

Figure 2

Histogram illustrating the effect of different doses (0–0.4 μg/kg/minute) of noradrenaline on mean arterial pressure (MAP), renal blood flow (RBF), renal vascular resistance (RVR) and glomerular filtration rate (GFR) in the dog. Both MAP and GFR are significantly increased by noradrenaline at clinically relevant doses. ^*P < 0.01; ^**P < 0.05. Published with permission from The Journal of Physiology [18].

Figure 3

The blood pressure effect of high-dose dopamine (25 μg/kg/minute) compared to noradrenaline (up to 1.5 μg/kg/minute) in patients with hypotensive hyperdynamic septic shock. Noradrenaline is clearly superior in restoring mean arterial pressure to normotensive levels. For all measurements, P < 0.0001.

Figure 4

The comparative effects of high-dose dopamine and noradrenaline on urine output in patients with hyperdynamic hypotensive septic shock and oliguria. Noradrenaline is clearly superior in restoring urine output. For all measurements, P < 0.0001.