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

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Effect of Increasing Blood Pressure With Noradrenaline on the Microcirculation of Patients With Septic Shock and Previous Arterial Hypertension

OBJECTIVES

To assess whether an increase in mean arterial pressure in patients with septic shock and previous systemic arterial hypertension changes microcirculatory and systemic hemodynamic variables compared with patients without arterial hypertension (control).

DESIGN

Prospective, nonblinded, interventional study.

SETTING

Three ICUs in two teaching hospitals.

PATIENTS

After informed consent, we included patients older than 18 years with septic shock for at least 6 hours, sedated, and under mechanical ventilation. We paired patients with and without arterial hypertension by age.

INTERVENTIONS

After obtaining systemic and microcirculation baseline hemodynamic variables (time 0), we increased noradrenaline dose to elevate mean arterial pressure up to 85-90 mm Hg before collecting a new set of measurements (time 1).

MEASUREMENTS AND MAIN RESULTS

We included 40 patients (20 in each group). There was no significant difference in age between the groups. After the rise in mean arterial pressure, there was a significant increase in cardiac index and a slight but significant reduction in lactate in both groups. We observed a significant improvement in the proportion of perfused vessels (control: 57.2 ± 14% to 66 ± 14.8%; arterial hypertension: 61.4 ± 12.3% to 70.8 ± 7.1%; groups: p = 0.29; T0 and T1: p < 0.001; group and time interaction: p = 0.85); perfused vessels density (control: 15.6 ± 4 mm/mm to 18.6 ± 4.5 mm/mm; arterial hypertension: 16.4 ± 3.5 mm/mm to 19.1 ± 3 mm/mm; groups: p = 0.51; T0 and T1: p < 0.001; group and time interaction: p = 0.70), and microcirculatory flow index (control: 2.1 ± 0.6 to 2.4 ± 0.6; arterial hypertension: 2.1 ± 0.5 to 2.6 ± 0.2; groups: p = 0.71; T0 and T1: p = 0.002; group and time interaction: p = 0.45) in both groups.

CONCLUSIONS

Increasing mean arterial pressure with noradrenaline in septic shock patients improves density and flow in small vessels of sublingual microcirculation. However, this improvement occurs both in patients with previous arterial hypertension and in those without arterial hypertension.

Hepatic Perfusion Alterations in Septic Shock Patients: Impact of Early Goal-directed Therapy

BACKGROUND

Early goal-directed therapy (EGDT) has become an important therapeutic management in early salvage stage of septic shock. However, splenic organs possibly remained hypoperfused and hypoxic despite fluid resuscitation. This study aimed to evaluate the effect of EGDT on hepatic perfusion in septic shock patients.

METHODS

A prospective observational study was carried out in early septic shock patients who were admitted to Intensive Care Unit within 24 h after onset and who met all four elements of the EGDT criteria after treatment with the standard EGDT procedure within 6 h between December 1, 2012 and November 30, 2013. The hemodynamic data were recorded, and oxygen metabolism and hepatic functions were monitored. An indocyanine green clearance test was applied to detect the hepatic perfusion. The patients' characteristics were compared before treatment (T0), immediately after EGDT (T1), and 24 h after EGDT (T2). This study is registered at ClinicalTrials.org, NCT02060773.

RESULTS

Twenty-one patients were included in the study; however, the hepatic perfusion data were not included in the analysis for two patients; therefore, 19 patients were eligible for the study. Hemodynamics data, as monitored by pulse-indicator continuous cardiac output, were obtained from 16 patients. There were no significant differences in indocyanine green plasma disappearance rate (ICG-PDR) and 15-min retention rate (R15) at T0 (11.9 ± 5.0%/min and 20.0 ± 13.2%), T1 (11.4 ± 5.1%/min and 23.6 ± 14.9%), and T2 (11.0 ± 4.5%/min and 23.7 ± 15.3%) (all P > 0.05). Both of the alterations of ICG-PDR and R15 showed no differences at T0, T1, and T2 in the patients of different subgroups that achieved different resuscitation goal numbers when elected (P > 0.05).

CONCLUSION

There were no hepatic perfusion improvements after EGDT in the early phase of patients with septic shock.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02060773 (https://clinicaltrials.gov/ct2/show/NCT02060773).

Challenges in Sepsis Care: New Sepsis Definitions and Fluid Resuscitation Beyond the Central Venous Pressure

There are two important recent changes in sepsis care. The first key change is the 2016 Sepsis-3 definitions from the recent consensus workgroup with new sepsis and septic shock definitions. Useful tools for assessing patients that have a greater risk of mortality include Sequential Organ Failure Assessment (SOFA) in intensive care units and quick SOFA outside intensive care units. The second change involves management of fluid resuscitation and measures of volume responsiveness. Measures such as blood pressure and central venous pressure are not reliable. Fluid challenges and responsiveness should be based on stroke volume change of greater than 10%.

Yoga in addition to standard care for patients with haematological malignancies

BACKGROUND

Haematological malignancies are malignant neoplasms of the myeloid or lymphatic cell lines including leukaemia, lymphoma and myeloma. In order to manage physical and psychological aspects of the disease and its treatment, complementary therapies like yoga are coming increasingly into focus. However, the effectiveness of yoga practice for people suffering from haematological malignancies remains unclear.

OBJECTIVES

To assess the effects of yoga practice in addition to standard cancer treatment for people with haematological malignancies.

SEARCH METHODS

Our search strategy included the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1950 to 4th February 2014), databases of ongoing trials (controlled-trials.com; clinicaltrials.gov), conference proceedings of the American Society of Clinical Oncology, the American Society of Hematology, the European Haematology Association, the European Congress for Integrative Medicine, and Global Advances in Health and Medicine. We handsearched references of these studies from identified trials and relevant review articles. Two review authors independently screened the search results.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of yoga in addition to standard care for haematological malignancies compared with standard care only. We did not restrict this to any specific style of yoga.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data for eligible studies and assessed the risk of bias according to predefined criteria. We evaluated distress, fatigue, anxiety, depression and quality of sleep. Further outcomes we planned to assess were health-related quality of life (HRQoL), overall survival (OS) and adverse events (AE), but data on these were not available.

MAIN RESULTS

Our search strategies led to 149 potentially relevant references, but only a single small study met our inclusion criteria. The included study was published as a full text article and investigated the feasibility and effect of Tibetan Yoga additional to standard care (N = 20; 1 person dropped out before attending any classes and no data were collected) compared to standard care only (N = 19). The study included people with all stages of Hodgkin and non-Hodgkin's lymphoma, with and without current cancer treatment. The mean age was 51 years.We judged the overall risk of bias as high as we found a high risk for performance, detection and attrition bias. Additionally, potential outcome reporting bias could not be completely ruled out. Following the recommendations of GRADE, we judged the overall quality of the body of evidence for all predefined outcomes as 'very low', due to the methodical limitations and the very small sample size.The influence of yoga on HRQoL and OS was not reported. There is no evidence that yoga in addition to standard care compared with standard care only can improve distress in people with haematological malignancies (mean difference (MD) -0.30, 95% confidence interval (CI) -5.55 to 4.95; P = 0.91). Similarly, there is no evidence of a difference between either group for fatigue (MD 0.00, 95% CI -0.94 to 0.94; P = 1.00), anxiety (MD 0.30, 95% CI -5.01 to 5.61; P = 0.91) or depression (MD -0.70, 95% CI -3.21 to 1.81; P = 0.58).There is very low quality evidence that yoga improves the overall quality of sleep (MD -2.30, 95% CI -3.78 to -0.82; P = 0.002). The yoga groups' total score for the Pittsburgh Sleep Quality Index (PSQI) was 5.8 (± 2.3 SD) and better than the total score (8.1 (± 2.4 SD)) of the control group. A PSQI total score of 0 to 5 indicates good sleep whereas PSQI total score 6 to 21 points towards significant sleep disturbances. The occurrence of AEs was not reported.

AUTHORS' CONCLUSIONS

The currently available data provide little information about the effectiveness of yoga interventions for people suffering from haematological malignancies. The finding that yoga may be beneficial for the patients' quality of sleep is based on a very small body of evidence. Therefore, the role of yoga as an additional therapy for haematological malignancies remains unclear. Further high-quality randomised controlled trials with larger numbers of participants are needed to make a definitive statement.

Impact of intravascular volume replacement and transfusion on outcome: where are we now?

Intravenous fluid administration is often required to counteract haemodynamic instability during emergency and elective surgeries, as well as in the intensive care unit. However, the best type and the amount of fluid required are controversial. A recent meta-analysis suggested that there is no difference among different types of colloids on outcome. Furthermore, colloids and crystalloids seem to be comparable in terms of efficiency in reverting haemodynamic instability, as well as morbidity and mortality. The interpretation of the results of different randomised controlled trials is somewhat difficult - the context must be always kept in mind. For example, results may differ in septic as compared to non-septic patient populations. Another important aspect concerns the effects on the macro- versus microcirculation. More recent studies emphasise that the microcirculation has to be taken into account when studying and interpreting the interaction between fluid therapy and the underlying disease. Nevertheless, the macrocirculation and clinical parameters have to be considered as well. Given that red blood cells remain the most important oxygen carriers, recent evidence regarding blood age may stimulate new studies according to the actual range for blood storage. Artificial oxygen carriers may play a role in specific situations, where the transfusion is indicated but the access to blood is problematic, but there is doubt that they may replace blood transfusion.

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.