Abstract
IntroductionSeptic shock is characterized by altered tissue perfusion associated with persistent arterial hypotension. Vasopressor therapy is generally required to restore organ perfusion but the optimal mean arterial pressure (MAP) that should be targeted is uncertain. The aim of this study was to assess the effects of increasing MAP using norepinephrine (NE) on hemodynamic and metabolic variables and on microvascular reactivity in patients with septic shock.MethodsThis was a single center, prospective, interventional study conducted in the medico-surgical intensive care unit of a university hospital. Thirteen patients in septic shock for less than 48 hours who required NE administration were included. NE doses were adjusted to obtain MAPs of 65, 75, 85 and (back to) 65 mmHg. In addition to hemodynamic and metabolic variables, we measured thenar muscle oxygen saturation (StO2), using near infrared spectroscopy (NIRS), with serial vaso-occlusive tests (VOTs) on the upper arm. We also evaluated the sublingual microcirculation using sidestream dark field (SDF) imaging in 6 of the patients.ResultsIncreasing NE dose was associated with an increase in cardiac output (from 6.1 to 6.7 l/min, P<0.05) and mixed venous oxygen saturation (SvO2, from 70.6 to 75.9%, P<0.05). Oxygen consumption (VO2) remained stable, but blood lactate levels decreased. There was a significant increase in the ascending slope of StO2 (from 111 to 177%/min, P<0.05) after VOTs. SDF imaging showed an increase in perfused vessel density (PVD, from 11.0 to 13.2 n/mm, P<0.05) and in microvascular flow index (MFI, from 2.4 to 2.9, P<0.05).ConclusionsIn this series of patients with septic shock, increasing MAP above 65 mmHg with NE was associated with increased cardiac output, improved microvascular function, and decreased blood lactate concentrations. The microvascular response varied among patients suggesting that individualization of blood pressure targets may be warranted.
Highlights
Septic shock is characterized by altered tissue perfusion associated with persistent arterial hypotension
Jhanji and colleagues [11] showed that increasing mean arterial pressure (MAP) from 60 to 70, 80, and 90 mm Hg by increasing the NE dose could increase oxygen delivery (DO2) and cutaneous microvascular flow; the authors found no significant effect on the microcirculation when using sidestream dark field (SDF) imaging techniques
The mean baseline central venous pressure (CVP) was 12 mm Hg, cardiac index was 3.6 L/minutem2, mixed venous oxygen saturation (SvO2) was 70%, and ΔPP was less than 13% (Table 2)
Summary
Septic shock is characterized by altered tissue perfusion associated with persistent arterial hypotension. Septic shock is characterized by an alteration in tissue perfusion associated with persistent arterial hypotension - generally defined as a systolic arterial pressure of less than 90 mm Hg [1] - despite adequate fluid resuscitation [2]. This leads to organ dysfunction and even death in around 50% of cases [3]. Using the same SDF imaging techniques and a similar protocol with MAP at 65, 75, and 85 mm Hg, Dubin and colleagues [12] reported no change in the sublingual microcirculation All of these data suggest that considerable interpatient variability can occur and that the optimal MAP level remains unclear
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