Immediate Norepinephrine in Endotoxic Shock: Effects on Regional and Microcirculatory Flow.

OBJECTIVES: To investigate the effects of immediate start of norepinephrine versus initial fluid loading followed by norepinephrine on macro hemodynamics, regional splanchnic and intestinal microcirculatory flows in endotoxic shock. DESIGN: Animal experimental study. SETTING: University translational research laboratory. SUBJECTS: Fifteen Landrace pigs. INTERVENTIONS: Shock was induced by escalating dose of lipopolysaccharide. Animals were allocated to immediate start of norepinephrine (i-NE) ( n = 6) versus mandatory 1-hour fluid loading (30 mL/kg) followed by norepinephrine (i-FL) ( n = 6). Once mean arterial pressure greater than or equal to 75 mm Hg was, respectively, achieved, successive mini-fluid boluses of 4 mL/kg of Ringer Lactate were given whenever: a) arterial lactate greater than 2.0 mmol/L or decrease less than 10% per 30 min and b) fluid responsiveness was judged to be positive. Three additional animals were used as controls (Sham) ( n = 3). Time × group interactions were evaluated by repeated-measures analysis of variance. MEASUREMENTS AND MAIN RESULTS: Hypotension was significantly shorter in i-NE group (7.5 min [5.5-22.0 min] vs 49.3 min [29.5-60.0 min]; p < 0.001). Regional mesenteric and microcirculatory flows at jejunal mucosa and serosa were significantly higher in i-NE group at 4 and 6 hours after initiation of therapy ( p = 0.011, p = 0.032, and p = 0.017, respectively). Misdistribution of intestinal microcirculatory blood flow at the onset of shock was significantly reversed in i-NE group ( p < 0.001), which agreed with dynamic changes in mesenteric-lactate levels ( p = 0.01) and venous-to-arterial carbon dioxide differences ( p = 0.001). Animals allocated to i-NE showed significantly higher global end-diastolic volumes ( p = 0.015) and required significantly less resuscitation fluids ( p < 0.001) and lower doses of norepinephrine ( p = 0.001) at the end of the experiment. Pulmonary vascular permeability and extravascular lung water indexes were significantly lower in i-NE group ( p = 0.021 and p = 0.004, respectively). CONCLUSIONS: In endotoxemic shock, immediate start of norepinephrine significantly improved regional splanchnic and intestinal microcirculatory flows when compared with mandatory fixed-dose fluid loading preceding norepinephrine. Immediate norepinephrine strategy was related with less resuscitation fluids and lower vasopressor doses at the end of the experiment.

Diastolic shock index and clinical outcomes in patients with septic shock.

BACKGROUND: Loss of vascular tone is a key pathophysiological feature of septic shock. Combination of gradual diastolic hypotension and tachycardia could reflect more serious vasodilatory conditions. We sought to evaluate the relationships between heart rate (HR) to diastolic arterial pressure (DAP) ratios and clinical outcomes during early phases of septic shock. METHODS: Diastolic shock index (DSI) was defined as the ratio between HR and DAP. DSI calculated just before starting vasopressors (Pre-VPs/DSI) in a preliminary cohort of 337 patients with septic shock (January 2015 to February 2017) and at vasopressor start (VPs/DSI) in 424 patients with septic shock included in a recent randomized controlled trial (ANDROMEDA-SHOCK; March 2017 to April 2018) was partitioned into five quantiles to estimate the relative risks (RR) of death with respect to the mean risk of each population (assumed to be 1). Matched HR and DAP subsamples were created to evaluate the effect of the individual components of the DSI on RRs. In addition, time-course of DSI and interaction between DSI and vasopressor dose (DSI*NE.dose) were compared between survivors and non-survivors from both populations, while ROC curves were used to identify variables predicting mortality. Finally, as exploratory observation, effect of early start of vasopressors was evaluated at each Pre-VPs/DSI quintile from the preliminary cohort. RESULTS: Risk of death progressively increased at gradual increments of Pre-VPs/DSI or VPs/DSI (One-way ANOVA, p < 0.001). Progressive DAP decrease or HR increase was associated with higher mortality risks only when DSI concomitantly increased. Areas under the ROC curve for Pre-VPs/DSI, SOFA and initial lactate were similar, while mean arterial pressure and systolic shock index showed poor performances to predict mortality. Time-course of DSI and DSI*NE.dose was significantly higher in non-survivors from both populations (repeated-measures ANOVA, p < 0.001). Very early start of vasopressors exhibited an apparent benefit at higher Pre-VPs/DSI quintile. CONCLUSIONS: DSI at pre-vasopressor and vasopressor start points might represent a very early identifier of patients at high risk of death. Isolated DAP or HR values do not clearly identify such risk. Usefulness of DSI to trigger or to direct therapeutic interventions in early resuscitation of septic shock need to be addressed in future studies.

Effects of very early start of norepinephrine in patients with septic shock: a propensity score-based analysis.

BACKGROUND: Optimal timing for the start of vasopressors (VP) in septic shock has not been widely studied since it is assumed that fluids must be administered in advance. We sought to evaluate whether a very early start of VP, even without completing the initial fluid loading, might impact clinical outcomes in septic shock. METHODS: A total of 337 patients with sepsis requiring VP support for at least 6 h were initially selected from a prospectively collected database in a 90-bed mixed-ICU during a 24-month period. They were classified into very-early (VE-VPs) or delayed vasopressor start (D-VPs) categories according to whether norepinephrine was initiated or not within/before the next hour of the first resuscitative fluid load. Then, VE-VPs (n = 93) patients were 1:1 propensity matched to D-VPs (n = 93) based on age; source of admission (emergency room, general wards, intensive care unit); chronic and acute comorbidities; and lactate, heart rate, systolic, and diastolic pressure at vasopressor start. A risk-adjusted Cox proportional hazard model was fitted to assess the association between VE-VPs and day 28 mortality. Finally, a sensitivity analysis was performed also including those patients requiring VP support for less than 6 h. RESULTS: Patients subjected to VE-VPs received significantly less resuscitation fluids at vasopressor starting (0[0-510] vs. 1500[650-2300] mL, p < 0.001) and during the first 8 h of resuscitation (1100[500-1900] vs. 2600[1600-3800] mL, p < 0.001), with no significant increase in acute renal failure and/or renal replacement therapy requirements. VE-VPs was related with significant lower net fluid balances 8 and 24 h after VPs. VE-VPs was also associated with a significant reduction in the risk of death compared to D-VPs (HR 0.31, CI95% 0.17-0.57, p < 0.001) at day 28. Such association was maintained after including patients receiving vasopressors for < 6 h. CONCLUSION: A very early start of vasopressor support seems to be safe, might limit the amount of fluids to resuscitate septic shock, and could lead to better clinical outcomes.