Effects of changes in arterial pressure on organ perfusion during septic shock

Microcirculatory dysfunction in sepsis: pathophysiology, clinical monitoring, and potential therapies

Abnormal microvascular perfusion, including decreased functional capillary density and increased blood flow heterogeneity, is observed in early stages of the systemic inflammatory response to infection and appears to have prognostic significance in human sepsis. It is known that improvements in systemic hemodynamics are weakly correlated with the correction of microcirculatory parameters, despite an appropriate treatment of macrohemodynamic abnormalities. Furthermore, conventional hemodynamic monitoring systems available in clinical practice fail to detect microcirculatory parameter changes and responses to treatments, as they do not evaluate intrinsic events that occur in the microcirculation. Fortunately, some bedside diagnostic methods and therapeutic options are specifically directed to the assessment and treatment of microcirculatory changes. In the present review we discuss fundamental aspects of septic microcirculatory abnormalities, including pathophysiology, clinical monitoring, and potential therapies.

The association between lactate, mean arterial pressure, central venous oxygen saturation and peripheral temperature and mortality in severe sepsis: a retrospective cohort analysis

Background

During resuscitation in severe sepsis and septic shock, several goals are set. However, usually not all goals are equally met. The aim of this study is to determine the relative importance of the different goals, such as mean arterial pressure (MAP), lactate, central venous oxygen saturation (ScvO₂) and central to forefoot temperature (delta-T), and how they relate to intensive care unit (ICU) and hospital mortality.

Methods

In a retrospective cohort study in a 20-bed mixed medical and surgical ICU of a teaching hospital we studied consecutive critically ill patients who were admitted for confirmed infection and severe sepsis or septic shock between 2008 and 2014. All validated MAP, lactate levels, ScvO₂ and delta-T for the first 24 hours of ICU treatment were extracted from a clinical database. Logistic regression analyses were performed on validated measurements in the first hour after admission and on mean values over 24 hours. Patients were categorized by MAP (24-hour mean below or above 65 mmHg) and lactate (24-hour mean below or above 2 mmol/l) for Cox regression analysis.

Results

From 837 patients, 821 were eligible for analysis. All had MAP and lactate measurements. The delta-T was available in 812 (99 %) and ScvO₂ was available for 193 out of these patients (23.5 %). Admission lactate (p < 0.001) and admission MAP (p < 0.001) were independent predictors of ICU and hospital mortality. The 24-hour mean values for lactate, MAP and delta-T were all independent predictors of ICU mortality. Hospital mortality was independently predicted by the 24-hour mean lactate (odds ratio (OR) 1.34, 95 % confidence interval (CI) 1.30–1.40, p = 0.001) mean MAP (OR 0.96, 95 % CI 0.95–0.97, p = 0.001) and mean delta-T (OR 1.09, 95 % CI 1.06–1.12, p = 0.001). Patients with a 24-hour mean lactate below 2 mmol/l and a 24-hour mean MAP above 65 mmHg had the best survival, followed by patients with a low lactate and a low MAP.

Conclusions

Admission MAP and lactate independently predicted ICU and hospital mortality. The 24-hour mean lactate, mean MAP and mean delta-T independently predicted hospital mortality. A Cox regression analysis showed that 24-hour mean lactate above 2 mmol/l is the strongest predictor for ICU mortality.

Endothelial and Microcirculatory Function and Dysfunction in Sepsis

The microcirculation is a series of arterioles, capillaries, and venules that performs essential functions of oxygen and nutrient delivery, customized to the unique physiologic needs of the supplied organ. The homeostatic microcirculatory response to infection can become harmful if overactive and/or dysregulated. Pathologic microcirculatory dysfunction can be directly visualized by intravital microscopy or indirectly measured via detection of circulating biomarkers. Although several treatments have been shown to protect the microcirculation during sepsis, they have not improved patient outcomes when applied indiscriminately. Future outcomes-oriented studies are needed to test sepsis therapeutics when personalized to a patient's microcirculatory dysfunction.

Microcirculatory disorders during septic shock

PURPOSE OF REVIEW

Despite the progress made over the past 20 years in the treatment of septic shock, mortality remains high. Microcirculatory disorders raise considerable interest aiming to improve the understanding of the physiopathology of septic shock and its management.

RECENT FINDINGS

Numerous experimental and clinical studies have gradually focused on the analysis of microcirculatory blood flow and identified alterations in small vessels. These microcirculatory abnormalities appear early, are heterogeneous, and are directly linked to organ failure, as well as the patient's prognosis. These anomalies vary from one patient to the other, and their evolution during resuscitation cannot be predicted by the isolated analysis of global hemodynamic parameters such as blood pressure or heart rate.

SUMMARY

Microcirculatory disorders appear at a central place of the physiopathology and are highly associated with the patient prognosis; it therefore seems important to develop and integrate parameters reflecting tissue perfusion in the management of septic shock.

[Critically ill pediatric hemato-oncology patient: What we do is what we should do?]

OBJECTIVE

Primary objective, to describe the management and monitorization of critically ill pediatric hemato-oncology patient (CIPHO) in the Spanish pediatric intensive care units (PICU). Secondary objective, through a literature review, to identify possible areas of improvement.

MATERIAL AND METHODS

Observational transversal descriptive study. An anonymous web-based survey was sent to 324 Spanish pediatric intensivists from April 2011 to May 2011. None of them were pediatric residents.

RESULTS

The survey was answered by 105 intensivists, 59/105 always agreed their treatment with the oncologist. In case of hemodynamic instability, non-invasive blood pressure monitoring is always done by 85/105 and almost always optimized by intra-arterial measuring (85/105) and central venous pressure (70/105). If respiratory failure the use of non-invasive ventilation (NIPPV) is always (36/105) or frequently (60/105) established prior to conventional mechanical ventilation. To replace or withdraw non-invasive ventilation only 44/96 of the respondents to this question use a clinical protocol. Before the instauration of conventional mechanical ventilation the oncological prognosis is considered by 72/105. In case of acute oliguric renal failure the renal replacement techniques are widely used (74/105). The withdrawal of sustaining life support is frequently discussed (75/103) and agreed with the oncologist (91/103) and caregivers (81/103).

CONCLUSIONS

In our study, despite there is not a defined standard-of-care, the respondents showed similar therapeutics and monitorization choices. The use of NIPPV as first respiratory assistance is extended. Prospective, observational and multicenter studies should be developed to establish the results of this management in this population.

Early goal-directed resuscitation of patients with septic shock: current evidence and future directions

Severe sepsis and septic shock are among the leading causes of mortality in the intensive care unit. Over a decade ago, early goal-directed therapy (EGDT) emerged as a novel approach for reducing sepsis mortality and was incorporated into guidelines published by the international Surviving Sepsis Campaign. In addition to requiring early detection of sepsis and prompt initiation of antibiotics, the EGDT protocol requires invasive patient monitoring to guide resuscitation with intravenous fluids, vasopressors, red cell transfusions, and inotropes. The effect of these measures on patient outcomes, however, remains controversial. Recently, three large randomized trials were undertaken to re-examine the effect of EGDT on morbidity and mortality: the ProCESS trial in the United States, the ARISE trial in Australia and New Zealand, and the ProMISe trial in England. These trials showed that EGDT did not significantly decrease mortality in patients with septic shock compared with usual care. In particular, whereas early administration of antibiotics appeared to increase survival, tailoring resuscitation to static measurements of central venous pressure and central venous oxygen saturation did not confer survival benefit to most patients. In the following review, we examine these findings as well as other evidence from recent randomized trials of goal-directed resuscitation. We also discuss future areas of research and emerging paradigms in sepsis trials.

Effects of ketanserin on microcirculatory alterations in septic shock: An open-label pilot study

INTRODUCTION

Microcirculatory alterations in sepsis are associated with increased morbidity and mortality. These alterations occur despite macrohemodynamic resuscitation. Alternative pro-microcirculatory strategies, including vasodilatory drugs, have been suggested to improve capillary blood flow. Ketanserin, a serotonin receptor antagonist, is an attractive candidate because of its vasodilatory, antithrombotic, and anti-inflammatory effects.

METHODS

This is an open-label pilot study on the effect of ketanserin administration on microcirculatory alterations in septic shock, defined as microvascular flow index (MFI)≤2.5 after a strict macrohemodynamic resuscitation protocol. Sidestream dark-field imaging was applied to assess the microcirculation. A stepwise incremental dose regiment was applied until an MFI>2.9, the primary end point, was reached.

RESULTS

Ten patients (Acute Physiology and Chronic Health Evaluation IV scores of 115 [100-136]) were included. Baseline MFI was 1.71 (1.31-2.32) and was significantly increasing to 2.96 (2.54-3.00; P=.021) during the ketanserin infusion. The total ketanserin dose was 0.09 (0.08-0.13) mg/kg per patient in 60 (30-60) minutes. In 3 patients (30%), the ketanserin infusion was discontinued due to refractory hypotension.

CONCLUSION

An improvement in microcirculatory perfusion was observed during ketanserin administration in patients with septic shock after macrohemodynamic resuscitation. This finding needs further exploration in a placebo-controlled setting.

Current concepts on hemodynamic support and therapy in septic shock

Severe sepsis and septic shock represent a major healthcare challenge. Much of the improvement in mortality associated with septic shock is related to early recognition combined with timely fluid resuscitation and adequate antibiotics administration. The main goals of septic shock resuscitation include intravascular replenishment, maintenance of adequate perfusion pressure and oxygen delivery to tissues. To achieve those goals, fluid responsiveness evaluation and complementary interventions - i.e. vasopressors, inotropes and blood transfusion - may be necessary. This article is a literature review of the available evidence on the initial hemodynamic support of the septic shock patients presenting to the emergency room or to the intensive care unit and the main interventions available to reach those targets, focusing on fluid and vasopressor therapy, blood transfusion and inotrope administration.

Arterial blood pressure targets in septic shock: is it time to move to an individualized approach?

Xu and colleagues evaluated the impact of increasing mean arterial blood pressure levels through norepinephrine administration on systemic hemodynamics, tissue perfusion, and sublingual microcirculation of septic shock patients with chronic hypertension. The authors concluded that, although increasing arterial blood pressure improved sublingual microcirculation parameters, no concomitant improvement in systemic tissue perfusion indicators was found. Here, we discuss why resuscitation targets may need to be individualized, taking into account the patient’s baseline condition, and present directions for future research in this field.

Clinical Effect of Shenfu Injection in Patients with Septic Shock: A Meta-Analysis and Systematic Review

Purpose. To conduct a meta-analysis evaluating the efficacy of Shenfu injection for treating patients with septic shock when compared with conventional therapy. Methods. Eight databases including Pubmed, EMBASE, Cochrane Library, ISI Web of Science, CNKI, Wanfang, VIP, and CBM were searched up to October 2014. Randomized controlled trials assessing the efficacy of Shenfu injection were identified. Mean arterial pressure, heart rate, lactate, and mortality were included as outcome measurements. Results. We analyzed data from 12 randomized controlled trials involving 904 participants. Compared with conventional therapy, Shenfu injection could further increase the mean arterial pressure at 1 hour (SMD 0.38; 95% CI, 0.01–0.74) and 6 hours (SMD 0.82; 95% CI, 0.03–1.61). Shenfu injection could further normalize heart rate at 6 hours (SMD −0.90; 95% CI, −1.47–0.33) and clear serum lactate at 6 hours (SMD −0.51; 95% CI, −0.70–0.32) and 24 hours (SMD, 0.52; 95% CI, −0.77–0.26). As the endpoint of mortality was not unified, it was not meta-analyzed. Conclusions. Based on the findings in present review, Shenfu injection is more effective than conventional therapy in increasing mean arterial pressure, normalizing heart rate, clearing serum lactate, and reducing mortality. These results should be confirmed in higher level clinical trials in the future.

Assessment of Fluid Balance and the Approach to Fluid Therapy in the Perioperative Patient

Perioperative patients can be highly dynamic and have various metabolic, physiologic, and organ system derangements that necessitate smart monitoring strategies and careful fluid therapy. The interplay between changing patient status, therapeutic interventions, and patient response makes effective monitoring crucial to successful treatment. Monitoring the perioperative patient and an approach to fluid therapy are discussed in this text.

Effects of early hemodynamic resuscitation on left ventricular performance and microcirculatory function during endotoxic shock

Background

Microcirculation and macrohemodynamics are severely compromised during septic shock. However, the relationship between these two compartments needs to be further investigated. We hypothesized that early resuscitation restores left ventricular (LV) performance and microcirculatory function but fails to prevent metabolic disorders. We studied the effects of an early resuscitation protocol (ERP) on LV pressure/volume loops-derived parameters, sublingual microcirculation, and metabolic alterations during endotoxic shock.

Methods

Twenty-five pigs were randomized into three groups: LPS group: Escherichia coli lipopolysaccharide (LPS); ERP group: LPS + ERP based on volume expansion, dobutamine, and noradrenaline infusion; Sham group. LV pressure/volume-derived parameters, systemic hemodynamics, sublingual microcirculation, and metabolic profile were assessed at baseline and after completing the resuscitation protocol.

Results

LPS significantly decreased LV end-diastolic volume, myocardial contractility, stroke work, and cardiac index (CI). Early resuscitation preserved preload, and myocardial contractility, increased CI and heart rate (p < .05). LPS severely diminished sublingual microvascular flow index (MFI), perfused vascular density (PVD), and the proportion of perfused vessels (PPV), while increased the heterogeneity flow index (HFI) (p < .05). Despite MFI was relatively preserved, MVD, PVD, and HFI were significantly impaired after resuscitation (p < .05). The macro- and microcirculatory changes were associated with increased lactic acidosis and mixed venous O₂ saturation when compared to baseline values (p < .05). The scatter plot between mean arterial pressure (MAP) and MFI showed a biphasic relationship, suggesting that the values were within the limits of microvascular autoregulation when MAP was above 71 ± 6 mm Hg (R² = 0.63).

Conclusions

Early hemodynamic resuscitation was effective to restore macrohemodynamia and myocardial contractility. Despite MAP and MFI were relatively preserved, the persistent microvascular dysfunction could explain metabolic disorders. The relationship between micro- and systemic hemodynamia and their impact on cellular function and metabolism needs to be further studied during endotoxic shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-015-0049-y) contains supplementary material, which is available to authorized users.

A high mean arterial pressure target is associated with improved microcirculation in septic shock patients with previous hypertension: a prospective open label study

Introduction

The effect of mean arterial pressure titration to a higher level on microcirculation in septic shock patients with previous hypertension remains unknown. Our goal is to assess the effect of mean arterial pressure titration to a higher level on microcirculation in hypertensive septic shock patients.

Methods

This is a single-center, open-label study. Hypertensive patients with septic shock for less than 24 hours after adequate fluid resuscitation and requiring norepinephrine to maintain a mean arterial pressure of 65 mmHg were enrolled. Mean arterial pressure was then titrated by norepinephrine from 65 mmHg to the normal level of the patient. In addition to hemodynamic variables, sublingual microcirculation was evaluated by sidestream dark field imaging.

Results

Nineteen patients were enrolled in the study. Increasing mean arterial pressure from 65 mmHg to normal levels was associated with increased central venous pressure (from 11 ± 4 to 13 ± 4 mmHg, P = 0.002), cardiac output (from 5.4 ± 1.4 to 6.4 ± 2.1 l/minute, P = 0.001), and central venous oxygen saturation (from 81 ± 7 to 83 ± 7%, P = 0.001). There were significant increases in small perfused vessel density (from 10.96 ± 2.98 to 11.99 ± 2.55 vessels/mm², P = 0.009), proportion of small perfused vessels (from 85 ± 18 to 92 ± 14%, P = 0.002), and small microvascular flow index (from 2.45 ± 0.61 to 2.80 ± 0.68, P = 0.009) when compared with a mean arterial pressure of 65 mmHg.

Conclusions

Increasing mean arterial pressure from 65 mmHg to normal levels is associated with improved microcirculation in hypertensive septic shock patients.

Trial registration

Clinicaltrials.gov: NCT01443494; registered 28 September 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0866-0) contains supplementary material, which is available to authorized users.

Optimizing mean arterial pressure in septic shock: a critical reappraisal of the literature

Guidelines recommend that a mean arterial pressure (MAP) value greater than 65 mm Hg should be the initial blood pressure target in septic shock, but what evidence is there to support this statement? We searched Pubmed and Google Scholar by using the key words 'arterial pressure', 'septic shock', and 'norepinephrine' and retrieved human studies published between 1 January 2000 and 31 July 2014. We identified seven comparative studies: two randomized clinical trials and five observational studies. The results of the literature review suggest that a MAP target of 65 mm Hg is usually sufficient in patients with septic shock. However, a MAP of around 75 to 85 mm Hg may reduce the development of acute kidney injury in patients with chronic arterial hypertension. Because of the high prevalence of chronic arterial hypertension in patients who develop septic shock, this finding is of considerable importance. Future studies should assess interactions between time, fluid volumes administered, and doses of vasopressors.

Exploration of skin perfusion in cirrhotic patients with septic shock

BACKGROUND & AIMS

Skin perfusion alterations are early and strong predictors of death in patients with septic shock. Cirrhosis is associated with systemic vasodilation and increases mortality from septic shock. We aimed at assessing whether the mottling score and tissue oxygen saturation (StO2) could be used as early predictors of death in cirrhotic patients with septic shock.

METHODS

This observational study included cirrhotic patients with septic shock. Each 6 h during the first 24 h, we collected data reflecting macrocirculation (mean arterial pressure, heart rate, central venous pressure, and cardiac output) and organ perfusion (arterial lactate, urinary output, ScvO2, mottling score, thenar, and knee StO2). Data of 75 non-cirrhotic patients with previously reported septic shock were used as control.

RESULTS

42 cirrhotic patients were included. Mortality at day 14 was 71%. At H6, parameters reflecting macrocirculation were not associated with mortality, whereas higher arterial lactate and mottling score were associated with death. Mottling score was the strongest predictor of mortality (sensitivity=0.63, specificity=1, OR=42.4 (2.3-785.9)). At H6, knee StO2 decreased in non-survivors and predicted death (sensitivity=0.45, specificity=1). In comparison with control, mottling kinetic was different in cirrhotic patients (delayed mottling appearance in non-survivors, earlier mottling disappearance in survivors). Knee StO2 and skin perfusion, assessed by laser-Doppler, were higher in cirrhotic patients.

CONCLUSIONS

Mottling score and knee StO2 at H6 were very specific predictors of death in patients with cirrhosis and septic shock. Their sensitivity was lower in cirrhotic patients due to delayed mottling appearance and higher knee StO2 related to higher skin perfusion.

Incidence and impact of skin mottling over the knee and its duration on outcome in critically ill patients

PURPOSE

Skin mottling is frequent and can be associated with an increased mortality rate in ICU patients with septic shock. Its overall incidence in ICU and its impact on outcome is unknown. We aimed to assess the incidence of skin mottling over the knee among all critically ill patients admitted in ICU and its role on their outcome.

METHODS

An observational study over a 1-year period in a 15-bed medical ICU of a teaching hospital. Skin mottling over the knee was prospectively and qualitatively assessed by trained nurses.

RESULTS

Incidence of skin mottling was 29% (230 of 791 patients) in overall, and 49% (32 of 65 patients) in the subset of patients admitted for septic shock. Skin mottling was present on the day on admission in 65% of patients and persisted more than 6 h in 59% of cases. In-ICU mortality was 8% in patients without mottling, 30% in patients with short skin mottling and 40% in patients with persistent skin mottling (p < 0.01 between all groups). In the overall population, skin mottling over the knee was associated with in-ICU mortality independently from SAPS II (aOR 3.29 [95% CI, 2.08-5.19], p < 0.0001). Among patients with skin mottling over the knee, persistence of skin mottling remained associated with increased in-ICU mortality independently of organ dysfunctions at the mottling onset (OR 2.77 [95% CI, 1.34-5.72], p = 0.004).

CONCLUSIONS

Skin mottling is frequent in the general population of patients admitted in ICU. Occurrence and persistence of skin mottling are independently associated with in-ICU mortality.

Pharmacotherapy Update on the Use of Vasopressors and Inotropes in the Intensive Care Unit

This paper summarizes the pharmacologic properties of vasoactive medications used in the treatment of shock, including the inotropes and vasopressors. The clinical application of these therapies is discussed and recent studies describing their use and associated outcomes are also reported. Comprehension of hemodynamic principles and adrenergic and non-adrenergic receptor mechanisms are salient to the appropriate therapeutic utility of vasoactive medications for shock. Vasoactive medications can be classified based on their direct effects on vascular tone (vasoconstriction or vasodilation) and on the heart (presence or absence of positive inotropic effects). This classification highlights key similarities and differences with respect to pharmacology and hemodynamic effects. Vasopressors include pure vasoconstrictors (phenylephrine and vasopressin) and inoconstrictors (dopamine, norepinephrine, and epinephrine). Each of these medications acts as vasopressors to increase mean arterial pressure by augmenting vascular tone. Inotropes include inodilators (dobutamine and milrinone) and the aforementioned inoconstrictors. These medications act as inotropes by enhancing cardiac output through enhanced contractility. The inodilators also reduce afterload from systemic vasodilation. The relative hemodynamic effect of each agent varies depending on the dose administered, but is particularly apparent with dopamine. Recent large-scale clinical trials have evaluated vasopressors and determined that norepinephrine may be preferred as a first-line therapy for a broad range of shock states, most notably septic shock. Consequently, careful selection of vasoactive medications based on desired pharmacologic effects that are matched to the patient's underlying pathophysiology of shock may optimize hemodynamics while reducing the potential for adverse effects.

Monitoring the microcirculation in critically ill patients

Alterations in microvascular perfusion have been identified in critically ill patients, especially in sepsis but also in cardiogenic shock, after cardiac arrest, and in high-risk surgery patients. These alterations seem to be implicated in the development of organ dysfunction and are associated with outcome. Even though microvascular perfusion can sometimes be homogenously decreased as in acute hemorrhage or in non-resuscitated cardiogenic shock, heterogeneity of perfusion is observed in sepsis and in resuscitated hemorrhagic/cardiogenic shock. Heterogeneity of perfusion has major implications for monitoring, as many techniques cannot detect microcirculatory alterations when heterogeneity of flow is present in significant amount. Indeed, devices such as laser Doppler or O2 electrodes and near-infrared spectroscopy have a relatively large sampling volume and measurements are affected by the highest values in the field. Using these techniques during a vascular occlusion test may help to characterize microvascular reactivity; however, microvascular reactivity sometimes fails to represent actual microvascular perfusion. Videomicroscopic techniques can nowadays be applied at bedside but are still restricted to some selected patients (quiet or sedated patients). Tissue PCO2 is an elegant alternative but is not yet broadly used. In this manuscript, we discuss the main advantages and limitations of the techniques available for bedside evaluation of the microcirculation in critically ill patients.

Increasing mean arterial blood pressure and heart rate with catecholaminergic drugs does not improve the microcirculation in children with congenital diaphragmatic hernia: a prospective cohort study

OBJECTIVE

To study whether dopamine, norepinephrine, and epinephrine improve not only mean arterial blood pressure and heart rate but also microcirculatory perfusion in children with congenital diaphragmatic hernia.

DESIGN

Prospective observational cohort study from November 2009 to July 2012.

SETTING

ICU of a level III university children's hospital.

PATIENTS

Twenty-eight consecutive congenital diaphragmatic hernia newborns of whom seven did not receive any catecholaminergic support and 21 received dopamine as the drug of first choice. Fourteen of the latter also received either norepinephrine or epinephrine in addition to dopamine. Twenty-eight healthy neonates, matched for gestational age, postnatal age, and gender, served as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data were obtained before and after dopamine start and before and after norepinephrine or epinephrine start in case it was given. For the congenital diaphragmatic hernia without catecholaminergic support, data were obtained at admission days 1 and 2 and for the controls on day 1 of life. The buccal microcirculation was studied using Sidestream Dark Field imaging. Also macrocirculatory, respiratory, and biochemical variables were collected. Mean arterial blood pressure had improved after dopamine start, whereas the microcirculation had not. After the start of either norepinephrine or epinephrine, both blood pressure and heart rate had increased. However, the microcirculation failed to improve again. The microcirculation in the healthy controls was better than that in the congenital diaphragmatic hernia patients with catecholaminergic support. After cutoff values for abnormal microcirculation had been defined, abnormal microcirculation after dopamine start predicted the need for additional catecholaminergic support (area under the curve, 0.74-0.88; sensitivity, 77-77%; specificity, 69-77%). Likewise, microcirculatory impairment was associated with the need for extracorporeal membrane oxygenation.

CONCLUSIONS

Catecholaminergic drug support with dopamine, norepinephrine, and/or epinephrine improved macrocirculatory function but did not improve the microcirculation in neonates with congenital diaphragmatic hernia. The microcirculation was not only impaired but it also predicted poor outcome.

Association between static and dynamic thenar near-infrared spectroscopy and mortality in patients with sepsis: a systematic review and meta-analysis

BACKGROUND

Oxygen delivery and consumption disturbances are frequently seen with critically illness, potentially leading to pathologic changes in tissue oxygenation (StO2). Near-infrared spectroscopy (NIRS) is a potentially useful method to monitor StO2, but the role of NIRS in prognostication of septic patients is uncertain. The aim of this study was to systematically review the literature and evaluate static and dynamic NIRS in patients with sepsis.

METHODS

This is a systematic review and meta-analysis of publications between 1966 and 2013. The MEDLINE and EMBASE databases were searched for studies on StO2 in patients with severe sepsis or septic shock. Meta-analysis was limited to studies about static and dynamic variables derived from NIRS in patients with sepsis. The association between StO2, reperfusion slope (Rres), occlusion slope, and maximum StO2 minus basal StO2 (ΔStO2) and prognosis in septic patients was evaluated.

RESULTS

The search identified 20 articles (962 participants; 717 with severe sepsis or septic shock, and 245 healthy controls). Compared with healthy controls, septic patients had lower levels of StO2 (78.27% [4.91%] vs. 82.02% [3.57%], p = 0.012), Rres (2.75% [0.63%] vs. 5.19% [2.86%] per second, p = 0.003), and ΔStO2 (7.86% [0.11%] vs. 12.53% [2.65%], p = 0.011). Survivors from sepsis presents higher levels of StO2 (81.68% [4.68%] vs. 74.54% [5.31%], p = 0.02) and Rres (3.37% [0.44%] vs. 2.16% [0.51%] per second, p = 0.016).

CONCLUSION

Septic patients have lower levels of StO2, Rres and ΔStO2, and survivors from sepsis present higher levels of StO2 and Rres compared with nonsurvivors.

LEVEL OF EVIDENCE

Systematic review/meta-analysis, level III.

Effects of terlipressin on microcirculation of small bowel mesentery in rats with endotoxic shock

BACKGROUND

Septic shock is still related to unacceptably high morbidity and mortality. Microcirculatory alteration has been demonstrated to be one important reason associated with this evolution. Vasoactive drugs are often used to restore adequate arterial pressure and tissue perfusion in septic shock. To define the roles of different drugs, the effects of terlipressin (TP) on the microcirculation of small bowel mesentery in rats with endotoxic shock were evaluated and compared with those of norepinephrine (NE).

METHODS

Twenty-five adult male Wistar rats were randomized to the control (n = 5), TP (n = 10), and NE (n = 10) groups. After endotoxic shock was induced by intravenous lipopolysaccharide administration for 30 min, rats in the NE and TP groups were infused with saline 5 mL/kg/h and simultaneously given NE 4 μg/kg/min or TP 8 μg/kg/h. The mean arterial pressure, heart rate, blood gas analysis, and microvascular blood flow images of small bowel mesentery were recorded.

RESULTS

After fluid resuscitation and vasopressor infusion, the mean arterial pressure was restored to the baseline values in the NE and TP groups. In the TP group, the heart rate was significantly lower compared with the NE group (P = 0.013). The proportion of perfused vessels and the microvascular flow index (MFI) were significantly increased; furthermore, the heterogeneity index of small vessels was markedly decreased in both the interventional groups with respect to the control group. Compared with the NE group, the MFI was significantly higher (P < 0.05) and the heterogeneity index was significantly lower (P < 0.05) in the TP group.

CONCLUSIONS

Both TP and NE improved hemodynamic and microcirculatory alterations in rats with endotoxic shock. Compared with NE, TP was more effective in promoting MFI and improving the heterogeneity of small bowel mesentery in rats.

Pathophysiology of microcirculatory dysfunction and the pathogenesis of septic shock

Multiple experimental and human trials have shown that microcirculatory alterations are frequent in sepsis. In this review, we discuss the various mechanisms that are potentially involved in their development and the implications of these alterations. Endothelial dysfunction, impaired inter-cell communication, altered glycocalyx, adhesion and rolling of white blood cells and platelets, and altered red blood cell deformability are the main mechanisms involved in the development of these alterations. Microcirculatory alterations increase the diffusion distance for oxygen and, due to the heterogeneity of microcirculatory perfusion in sepsis, may promote development of areas of tissue hypoxia in close vicinity to well-oxygenated zones. The severity of microvascular alterations is associated with organ dysfunction and mortality. At this stage, therapies to specifically target the microcirculation are still being investigated.

Elevated central venous pressure is associated with impairment of microcirculatory blood flow in sepsis: a hypothesis generating post hoc analysis

Background

Microcirculatory driving pressure is defined as the difference between post-arteriolar and venular pressure. In previous research, an absence of correlation between mean arterial blood pressure (MAP) and microcirculatory perfusion has been observed. However, the microcirculation may be considered as a low pressure compartment with capillary pressure closer to venous than to arterial pressure. From this perspective, it is conceivable that central venous pressure (CVP) plays a more important role in determination of capillary perfusion. We aimed to explore associations between CVP and microcirculatory perfusion.

Methods

We performed a post-hoc analysis of a prospective study in septic patients who were resuscitated according a strict non-CVP guided treatment protocol. Simultaneous measurements of hemodynamics and sublingual Sidestream Dark Field imaging were obtained 0 and 30 minutes after fulfillment of resuscitation goals. Data were examined for differences in microcirculatory variables for CVP ≤ or > 12 mmHg and its evolution over time, as well as for predictors of a microvascular flow index (MFI) < 2.6.

Results

In 70 patients with a mean APACHE II score of 21, 140 simultaneous measurements of CVP and sublingual microcirculation (vessels < 20 µmeter) were obtained. (MFI) and the percentage of perfused small vessels (PPV) were significantly lower in the ‘high’ CVP (> 12 mmHg) group as compared to patients in the ‘low’ CVP (≤12 mmHg) group (1.4 ± 0.9 vs. 1.9 ± 0.9, P = 0.006; and 88 ± 21% vs. 95 ± 8%, P = 0.006 respectively). Perfusion pressure (MAP–CVP) and cardiac output did not differ significantly between both CVP groups. From time point 0 to 30 minutes, a significant increase in MFI (from 1.6 ± 0.6 to 1.8 ± 0.9, P = 0.027) but not in PPV, was observed, while CVP and perfusion pressure significantly decreased in the same period. In a multivariate model CVP > 12 mmHg was the only significant predictor for a capillary MFI < 2.6 (Odds ratio 2.5 (95% confidence interval 1.1-5.8), P = 0.026).

Conclusion

We observed a significant association between a higher CVP and impairment of microcirculatory blood flow. Further research is needed to elaborate on our hypothesis generating findings that an elevated CVP may act as an outflow obstruction of organ perfusion.

Mean perfusion pressure deficit during the initial management of shock--an observational cohort study

PURPOSE

It is unclear if blood pressure targets for patients with shock should be adjusted to pre-morbid levels. We aimed to investigate mean deficit between the achieved mean perfusion pressure (MPP) in vasopressor-treated patients and their estimated basal (resting) MPP, and assess whether MPP deficit has any association with subsequent acute kidney injury (AKI).

MATERIALS AND METHODS

Fifty-one consecutive, non-trauma patients, aged ≥40 years, with ≥2 organ dysfunction and requiring vasopressor≥4 hours were observed at an academic intensive care unit. Mean MPP deficit [=%(basal MPP-achieved MPP)/basal MPP] and % time spent with >20% MPP deficit were assessed during initial 72 vasopressor hours (T0-T72) for each patient.

RESULTS

Achieved MPP was unrelated to basal MPP (P=.99). Mean MPP deficit was 18% (95% CI 15-21). Patients spent 48% (95% CI 39-57) time with >20% MPP deficit. Despite similar risk scores at T0, subsequent AKI (≥2 RIFLE class increase from T0) occurred more frequently in patients with higher (>median) MPP deficit compared to patients with lower MPP deficit (56% vs 28%; P=.045). Incidence of subsequent AKI was also higher among patients who spent greater % time with >20% MPP deficit (P=.04).

CONCLUSIONS

Achieved blood pressure during vasopressor therapy had no relationship to the pre-morbid basal level. This resulted in significant and varying degree of relative hypotension (MPP deficit), which could be a modifiable risk factor for AKI in patients with shock.

Microcirculatory alterations in patients with severe sepsis: impact of time of assessment and relationship with outcome

OBJECTIVES

Sepsis induces microvascular alterations that may play an important role in the development of organ dysfunction. However, the relationship of these alterations to systemic variables and outcome is still not well defined. We investigated which factors may influence microcirculatory alterations in patients with severe sepsis and whether these are independently associated with mortality.

DESIGN

Analysis of prospectively collected data from previously published studies by our group.

SETTING

A 36-bed, medicosurgical university hospital Department of Intensive Care.

PATIENTS

A total of 252 patients with severe sepsis in whom the sublingual microcirculation was visualized using orthogonal polarization spectral or sidestream darkfield imaging techniques.

MEASUREMENTS AND MAIN RESULTS

Microcirculatory measurements were obtained either early, within 24h of the onset of severe sepsis (n = 204), or later, after 48h (n = 48). When multiple measurements were obtained, only the first was considered. Although global hemodynamic variables were relatively preserved (mean arterial pressure 70 [65-77] mm Hg, cardiac index 3.3 [2.7-4.0] L/min.m, and SvO2 68.3 [62.8-74.7]%), microvascular variables were markedly altered (proportion of perfused small vessels 65 [50-74]%, microvascular flow index 2.15 [1.80-2.60], and heterogeneity of proportion of perfused small vessels 35 [20-50]%). Among microcirculatory variables, proportion of perfused small vessels was the strongest predictor of outcome (receiver operating characteristic curve area 0.818 [0.766-0.871], p < 0.001). Survival rates decreased markedly with severity of alterations in the proportion of perfused small vessels (70% and 75% in the two upper proportion of perfused small vessel quartiles compared with 3% and 44% in the two lower quartiles, p < 0.0001). Multivariable analysis identified proportion of perfused small vessels and sequential organ failure assessment score as independent predictors of outcome. Microcirculatory alterations were less severe in the later than in the earlier (proportion of perfused small vessels, 74 [57-82]% vs. 63 [48-71]%, p = 0.004) phase of sepsis. In multivariable analysis focused on the early period of sepsis, proportion of perfused small vessels and lactate were independent predictors of outcome.

CONCLUSIONS

Microcirculatory alterations are stronger predictors of outcome than global hemodynamic variables.

Increasing mean arterial blood pressure in sepsis: effects on fluid balance, vasopressor load and renal function

Introduction

The objective of this study was to evaluate the effects of two different mean arterial blood pressure (MAP) targets on needs for resuscitation, organ dysfunction, mitochondrial respiration and inflammatory response in a long-term model of fecal peritonitis.

Methods

Twenty-four anesthetized and mechanically ventilated pigs were randomly assigned (n = 8/group) to a septic control group (septic-CG) without resuscitation until death or one of two groups with resuscitation performed after 12 hours of untreated sepsis for 48 hours, targeting MAP 50-60 mmHg (low-MAP) or 75-85 mmHg (high-MAP).

Results

MAP at the end of resuscitation was 56 ± 13 mmHg (mean ± SD) and 76 ± 17 mmHg respectively, for low-MAP and high-MAP groups. One animal each in high- and low-MAP groups, and all animals in septic-CG died (median survival time: 21.8 hours, inter-quartile range: 16.3-27.5 hours). Norepinephrine was administered to all animals of the high-MAP group (0.38 (0.21-0.56) mcg/kg/min), and to three animals of the low-MAP group (0.00 (0.00-0.25) mcg/kg/min; P = 0.009). The high-MAP group had a more positive fluid balance (3.3 ± 1.0 mL/kg/h vs. 2.3 ± 0.7 mL/kg/h; P = 0.001). Inflammatory markers, skeletal muscle ATP content and hemodynamics other than MAP did not differ between low- and high-MAP groups. The incidence of acute kidney injury (AKI) after 12 hours of untreated sepsis was, respectively for low- and high-MAP groups, 50% (4/8) and 38% (3/8), and in the end of the study 57% (4/7) and 0% (P = 0.026). In septic-CG, maximal isolated skeletal muscle mitochondrial Complex I, State 3 respiration increased from 1357 ± 149 pmol/s/mg to 1822 ± 385 pmol/s/mg, (P = 0.020). In high- and low-MAP groups, permeabilized skeletal muscle fibers Complex IV-state 3 respiration increased during resuscitation (P = 0.003).

Conclusions

The MAP targets during resuscitation did not alter the inflammatory response, nor affected skeletal muscle ATP content and mitochondrial respiration. While targeting a lower MAP was associated with increased incidence of AKI, targeting a higher MAP resulted in increased net positive fluid balance and vasopressor load during resuscitation. The long-term effects of different MAP targets need to be evaluated in further studies.

Initial emergency department diagnosis and management of adult patients with severe sepsis and septic shock

Severe sepsis is a medical emergency affecting up to 18 million individuals world wide, with an annual incidence of 750,000 in North America alone. Mortality ranges between 28-50% of those individuals stricken by severe sepsis. Sepsis is a time critical illness, requiring early identification and prompt intervention in order to improve outcomes. This observation has led to increased awareness and education in the field of Emergency Medicine; it has also led to the implementation of critical interventions early in the course of patient management, specifically Early-Goal Directed Therapy, and rapid administration of appropriate antimicrobials. This review begins with a brief summary of the pathophysiology of sepsis, and then addresses the fundamental clinical aspects of ED identification and resuscitation of the septic patient.

Near infrared spectroscopy (NIRS) of the thenar eminence in anesthesia and intensive care

Near infrared spectroscopy of the thenar eminence (NIRS_th) is a noninvasive bedside method for assessing tissue oxygenation. The NIRS probe emits light with several wavelengths in the 700- to 850-nm interval and measures the reflected light mainly from a predefined depth. Complex physical models then allow the measurement of the relative concentrations of oxy and deoxyhemoglobin, and thus tissue saturation (StO₂), as well as an approximation of the tissue hemoglobin, given as tissue hemoglobin index.

Here we review of current knowledge of the application of NIRS_th in anesthesia and intensive care.

We performed an analytical and descriptive review of the literature using the terms “near-infrared spectroscopy” combined with “anesthesia,” “anesthesiology,” “intensive care,” “critical care,” “sepsis,” “bleeding,” “hemorrhage,” “surgery,” and “trauma” with particular focus on all NIRS studies involving measurement at the thenar eminence.

We found that NIRS_th has been applied as clinical research tool to perform both static and dynamic assessment of StO₂. Specifically, a vascular occlusion test (VOT) with a pressure cuff can be used to provide a dynamic assessment of the tissue oxygenation response to ischemia. StO₂ changes during such induced ischemia-reperfusion yield information on oxygen consumption and microvasculatory reactivity. Some evidence suggests that StO₂ during VOT can detect fluid responsiveness during surgery. In hypovolemic shock, StO₂ can help to predict outcome, but not in septic shock. In contrast, NIRS parameters during VOT increase the diagnostic and prognostic accuracy in both hypovolemic and septic shock. Minimal data are available on static or dynamic StO₂ used to guide therapy.

Although the available data are promising, further studies are necessary before NIRS_th can become part of routine clinical practice.

Defining the adequate arterial pressure target during septic shock: not a 'micro' issue but the microcirculation can help

The Surviving Sepsis Campaign guidelines suggest targeting a mean arterial pressure of at least 65 mm Hg to maintain organ perfusion pressure during septic shock. However, the optimal mean arterial pressure can be higher in patients with a history of hypertension or other vascular comorbidities or in those with increased abdominal pressure. In a given individual, the adequate mean arterial pressure target can be difficult to define with the routine hemodynamic parameters (for example, cardiac output, central or mixed venous blood oxygen saturation, and urine output). Near-infrared spectroscopy and sidestream dark field imaging have emerged as promising technologies for monitoring the microcirculation at the bedside. These new methods could provide additional clues to help define the adequate blood pressure to target during the resuscitation phase of septic shock.