Impact of microcirculatory video quality on the evaluation of sublingual microcirculation in critically ill patients

Microcirculation-guided resuscitation in sepsis: the next frontier?

Microcirculatory dysfunction plays a key role in the pathogenesis of tissue dysoxia and organ failure in sepsis. Sublingual videomicroscopy techniques enable the real-time non-invasive assessment of microvascular blood flow. Alterations in sublingual microvascular perfusion were detected during sepsis and are associated with poor outcome. More importantly, sublingual videomicroscopy allowed to explore the effects of commonly applied resuscitative treatments in septic shock, such as fluids, vasopressors and inotropes, and showed that the optimization of macro-hemodynamic parameters may not be accompanied by an improvement in microvascular perfusion. This loss of "hemodynamic coherence," i.e., the concordance between the response of the macrocirculation and the microcirculation, advocates for the integration of microvascular monitoring in the management of septic patients. Nonetheless, important barriers remain for a widespread use of sublingual videomicroscopy in the clinical practice. In this review, we discuss the actual limitations of this technique and future developments that may allow an easier and faster evaluation of the microcirculation at the bedside, and propose a role for sublingual microvascular monitoring in guiding and titrating resuscitative therapies in sepsis.

Optical Coherence Tomography Angiography of the Intestine: How to Prevent Motion Artifacts in Open and Laparoscopic Surgery?

(1) Introduction. The problem that limits the intraoperative use of OCTA for the intestinal circulation diagnostics is the low informative value of OCTA images containing too many motion artifacts. The aim of this study is to evaluate the efficiency and safety of the developed unit for the prevention of the appearance of motion artifacts in the OCTA images of the intestine in both open and laparoscopic surgery in the experiment; (2) Methods. A high-speed spectral-domain multimodal optical coherence tomograph (IAP RAS, Russia) operating at a wavelength of 1310 nm with a spectral width of 100 μm and a power of 2 mW was used. The developed unit was tested in two groups of experimental animals—on minipigs (group I, n = 10, open abdomen) and on rabbits (group II, n = 10, laparoscopy). Acute mesenteric ischemia was modeled and then 1 h later the small intestine underwent OCTA evaluation. A total of 400 OCTA images of the intact and ischemic small intestine were obtained and analyzed. The quality of the obtained OCTA images was evaluated based on the score proposed in 2020 by the group of Magnin M. (3) Results. Without stabilization, OCTA images of the intestine tissues were informative only in 32–44% of cases in open surgery and in 14–22% of cases in laparoscopic surgery. A vacuum bowel stabilizer with a pressure deficit of 22–25 mm Hg significantly reduced the number of motion artifacts. As a result, the proportion of informative OCTA images in open surgery increased up to 86.5% (Χ2 = 200.2, p = 0.001), and in laparoscopy up to 60% (Χ2 = 148.3, p = 0.001). (4) Conclusions. The used vacuum tissue stabilizer enabled a significant increase in the proportion of informative OCTA images by significantly reducing the motion artifacts.

The Reproducibility of the Point of Care Microcirculation (POEM) Score When Used to Assess Critically Ill Patients: A Multicenter Prospective Observational Study

BACKGROUND

The current standard of analyzing microcirculatory video microscopy is time-consuming and occurs away from the patient, limiting its clinical utility. Point-of-care assessment with incident dark field (IDF) microscopy, however, may offer greater clinical applicability. We aimed to determine the reproducibility of the Point of Care Microcirculation (POEM) tool when used at the bedside in critically ill patients.

METHODS

A multinational, multicenter, prospective observational study of adult intubated patients was undertaken during a 9-month period in Germany, the United Kingdom, and the United States. A user recorded a batch of four standardized video clips from each patient, calculated a POEM score and recorded the time for image acquisition. A second user blinded to the first repeated this process. Patients with video clips of poor quality were excluded. At a later date, the two users again blinded themselves to reassess both their own clips and those of the other user. Basic demographic information was recorded. Intrauser reliability (an individual user rescoring the same batch of videos after blinding), interuser reliability (a second user rescoring the other user's video batch after blinding), and test-retest reliability (two users individually capturing videos and recording POEM scores) were assessed using a linearly weighted kappa statistic for ordinal data.

RESULTS

Sixty-five patients were included in the final analysis. Observer agreement was substantial for all tests. Intrauser agreement was 0.73 (0.95 CI 0.64-0.81), interuser agreement 0.71 (0.95 CI 0.63-0.79), and test-retest agreement 0.75 (0.95 CI 0.65-0.86). Average time to record videos and assess POEM scores 7:34 ± 3:37 minutes.

CONCLUSIONS

Point-of-care assessment of the microcirculation using IDF video microscopy and POEM scoring appears to be both a feasible and reproducible approach to microcirculatory assessment. Testing of the score in critically ill patients showed substantial agreement within and between investigators, but further studies should validate its utility as a tool to guide shock resuscitation.

Evaluation of microcirculation by Sidestream Dark Field imaging: Impact of hemodynamic status on the occurrence of pressure artifacts - A pilot study

OBJECTIVE

The aims of the study were to evaluate the influence of hemodynamic status on pressure artifacts and the impact of pressure artifacts on microcirculatory flow.

METHODS

Sublingual microcirculation was assessed using a Sidestream Dark Field handheld imaging device in 7 anesthetized piglets, submitted to pharmacologically-induced blood pressure variations. For each video, a pressure score of 0, 1, or 10 was assigned for the category "pressure artifacts" of the "microcirculation image quality score". Videos with a pressure score of 0 and 1 were considered as "passing videos". The videos with a score of 10 were considered as "failing videos". Multivariate logistic regression models and multivariate linear mixed models with individual random effects were used.

RESULTS

As blood pressure decreased, the probability of obtaining a "failing video" increased (P = 0.0008). Pressure scores of 10 influenced significantly the perfused De Backer score (small and all vessels), the proportion of perfused vessels (small and all vessels), the microvascular flow index and the heterogeneity index. Pressure scores of 1 influenced significantly the parameters above-mentioned, except the perfused De Backer score for all vessels.

CONCLUSION

The probability of obtaining pressure artifacts during recording of microcirculation videos was higher when the arterial pressure was low. The presence of acceptable pressure artifacts also influenced microcirculation analysis.

IgM-enriched immunoglobulins (Pentaglobin) may improve the microcirculation in sepsis: a pilot randomized trial

BACKGROUND

Polyclonal or IgM-enriched immunoglobulins may be beneficial during sepsis as an adjuvant immunomodulatory therapy. We aimed to test whether the infusion of IgM-enriched immunoglobulins improves microvascular perfusion during sepsis.

METHODS

Single-centre, randomized, double-blind, placebo-controlled phase II trial including adult patients with a diagnosis of sepsis or septic shock for less than 24 h. Patients received an intravenous infusion of 250 mg/kg (5 mL/kg) per day of IgM-enriched immunoglobulins (Pentaglobin, n = 10) for 72 h or placebo (NaCl 0.9%, n = 9). At baseline and after 24 and 72 h of infusion, the sublingual microcirculation was assessed with Incident Dark Field videomicroscopy. Thenar near-infrared spectroscopy (NIRS) was applied with a vascular occlusion test to assess tissue oxygenation and microvascular reactivity. Levels of interleukin (IL) 1-beta, IL-6, IL-8, IL-10 and tumour necrosis factor alpha were measured in the serum.

RESULTS

The perfused vessel density (PVD) for small vessels (diameter < 20 micron) increased in the Pentaglobin group (from 21.7 ± 4.7 to 25.5 ± 5.1 mm/mm²) and decreased in the placebo group (from 25 ± 5.8 to 20.7 ± 4.1 mm/mm², p for interaction < 0.001, two-way analysis of variance). The absolute between-group difference at 72 h was 4.77 (standard error 2.34), p = 0.140. The microvascular flow index for small vessels increased at 24 h in the Pentaglobin group (from 2.68 [2.38-2.78] to 2.93 [2.82-3], p < 0.01) and decreased at 72 h in the placebo group (from 2.83 [2.60-2.97] to 2.67 [2.48-2.73], p < 0.05). Changes in general parameters, cytokines and NIRS-derived parameters were similar between the two groups, except for IL-6 and IL-10 that significantly decreased at 72 h only in the Pentaglobin group.

CONCLUSIONS

A 72-h infusion of IgM-enriched immunoglobulins (Pentaglobin) in patients with sepsis or septic shock may be associated with an increase in sublingual microvascular perfusion. Further studies are needed to confirm our findings. Trial registration NCT02655133, www.ClinicalTrials.gov, date of registration 7th January 2016, https://www.clinicaltrials.gov/ct2/show/NCT02655133.

Microcirculatory Impairment Is Associated With Multiple Organ Dysfunction Following Traumatic Hemorrhagic Shock: The MICROSHOCK Study

OBJECTIVES

To assess the relationship between microcirculatory perfusion and multiple organ dysfunction syndrome in patients following traumatic hemorrhagic shock.

DESIGN

Multicenter prospective longitudinal observational study.

SETTING

Three U.K. major trauma centers.

PATIENTS

Fifty-eight intubated and ventilated patients with traumatic hemorrhagic shock.

INTERVENTIONS

Sublingual incident dark field microscopy was performed within 12 hours of ICU admission (D0) and repeated 24 and 48 hours later. Cardiac output was assessed using oesophageal Doppler. Multiple organ dysfunction syndrome was defined as Serial Organ Failure Assessment score greater than or equal to 6 at day 7 post injury.

MEASUREMENTS AND MAIN RESULTS

Data from 58 patients were analyzed. Patients had a mean age of 43 ± 19 years, Injury Severity Score of 29 ± 14, and initial lactate of 7.3 ± 6.1 mmol/L and received 6 U (interquartile range, 4-11 U) of packed RBCs during initial resuscitation. Compared with patients without multiple organ dysfunction syndrome at day 7, patients with multiple organ dysfunction syndrome had lower D0 perfused vessel density (11.2 ± 1.8 and 8.6 ± 1.8 mm/mm; p < 0.01) and microcirculatory flow index (2.8 [2.6-2.9] and 2.6 [2.2-2.8]; p < 0.01) but similar cardiac index (2.5 [± 0.6] and 2.1 [± 0.7] L/min//m; p = 0.11). Perfused vessel density demonstrated the best discrimination for predicting subsequent multiple organ dysfunction syndrome (area under curve 0.87 [0.76-0.99]) compared with highest recorded lactate (area under curve 0.69 [0.53-0.84]), cardiac index (area under curve 0.66 [0.49-0.83]) and lowest recorded systolic blood pressure (area under curve 0.54 [0.39-0.70]).

CONCLUSIONS

Microcirculatory hypoperfusion immediately following traumatic hemorrhagic shock and resuscitation is associated with increased multiple organ dysfunction syndrome. Microcirculatory variables are better prognostic indicators for the development of multiple organ dysfunction syndrome than more traditional indices. Microcirculatory perfusion is a potential endpoint of resuscitation following traumatic hemorrhagic shock.

Untreated Relative Hypotension Measured as Perfusion Pressure Deficit During Management of Shock and New-Onset Acute Kidney Injury-A Literature Review

Maintaining an optimal blood pressure (BP) during shock is a fundamental tenet of critical care. Optimal BP targets may be different for different patients. In current practice, too often, uniform BP targets are pursued which may result in inadvertently accepting a degree of untreated relative hypotension, i.e., the deficit between patients' usual premorbid basal BP and the achieved BP, during vasopressor support. Relative hypotension is a common but an under-recognized and an under-treated sign among patients with potential shock state. From a physiological perspective, any relative reduction in the net perfusion pressure across an organ (e.g., renal) vasculature has a potential to overwhelm autoregulatory mechanisms, which are already under stress during shock. Such perfusion pressure deficit may consequently impact organs' ability to function or recover from an injured state. This review discusses such pathophysiologic mechanisms in detail with a particular focus on the risk of new-onset acute kidney injury (AKI). To review current literature, databases of Medline, Embase, and Google scholar were searched to retrieve articles that either adjusted BP targets based on patients' premorbid BP levels or considered relative hypotension as an exposure endpoint and assessed its association with clinical outcomes among acutely ill patients. There were no randomized controlled trials. Only seven studies could be identified and these were reviewed in detail. These studies indicated a significant association between the degree of relative hypotension that was inadvertently accepted in real-world practice and new-onset organ dysfunction or subsequent AKI. However, this is not a high-quality evidence. Therefore, well-designed randomized controlled trials are needed to evaluate whether adoption of individualized BP targets, which are initially guided by patient's premorbid basal BP and then tailored according to clinical response, is superior to conventional BP targets for vasopressor therapy, particularly among patients with vasodilatory shock states.

Monitoring peripheral perfusion and microcirculation

PURPOSE OF REVIEW

Microcirculatory alterations play a major role in the pathogenesis of shock. Monitoring tissue perfusion might be a relevant goal for shock resuscitation. The goal of this review was to revise the evidence supporting the monitoring of peripheral perfusion and microcirculation as goals of resuscitation. For this purpose, we mainly focused on skin perfusion and sublingual microcirculation.

RECENT FINDINGS

Although there are controversies about the reproducibility of capillary refill time in monitoring peripheral perfusion, it is a sound physiological variable and suitable for the ICU settings. In addition, observational studies showed its strong ability to predict outcome. Moreover, a preliminary study suggested that it might be a valuable goal for resuscitation. These results should be confirmed by the ongoing ANDROMEDA-SHOCK randomized controlled trial. On the other hand, the monitoring of sublingual microcirculation might also provide relevant physiological and prognostic information. On the contrary, methodological drawbacks mainly related to video assessment hamper its clinical implementation at the present time.

SUMMARY

Measurements of peripheral perfusion might be useful as goal of resuscitation. The results of the ANDROMEDA-SHOCK will clarify the role of skin perfusion as a guide for the treatment of shock. In contrast, the assessment of sublingual microcirculation mainly remains as a research tool.

Journal of Clinical Monitoring and Computing 2017/2018 end of year summary: monitoring-and provocation-of the microcirculation and tissue oxygenation

The microcirculation is the ultimate goal of hemodynamic optimization in the perioperative and critical care setting. In this fourth end-of-year summary of the Journal of Clinical Monitoring and Computing on this topic, we take a closer look at papers published in the last 2 years that focus on this important aspect. The majority of these papers investigated the use of either cerebral or peripheral tissue oxygen saturation, derived non-invasively using near infrared spectroscopy (NIRS). In some of these studies, the microcirculation was “provocated” by inducing short-term tissue hypoxia, allowing the assessment of functional microvascular reserve. Additionally, studies on technical differences between NIRS monitors are summarized, as well as studies investigating the feasibility of NIRS monitoring, mainly in the pediatric patient population. Last but not least, novel monitoring tools allow assessing oxygenation at a (sub)cellular level, and those papers incorporating these techniques are also reviewed here.

MicroDAIMON study: Microcirculatory DAIly MONitoring in critically ill patients: a prospective observational study

Background

Until now, the prognostic value of microcirculatory alterations in critically ill patients has been mainly evaluated in highly selected subgroups. Aim of this study is to monitor the microcirculation daily in mixed group of Intensive Care Unit (ICU)-patients and to establish the association between (the evolution of) microcirculatory alterations and outcome.

Methods

This is a prospective longitudinal observational single-centre study in adult patients admitted to a 12-bed ICU in an Italian teaching hospital. Sublingual microcirculation was evaluated daily, from admission to discharge/death, using Sidestream Dark Field imaging. Videos were analysed offline to assess flow and density variables. Laboratory and clinical data were recorded simultaneously. A priori, a Microvascular Flow Index (MFI) < 2.6 was defined as abnormal. A binary logistic regression analysis was performed to evaluate the association between microcirculatory variables and outcomes; a Kaplan–Meier survival curve was built. Outcomes were ICU and 90-day mortality.

Results

A total of 97 patients were included. An abnormal MFI was present on day 1 in 20.6%, and in 55.7% of cases during ICU admission. Patients with a baseline MFI < 2.6 had higher ICU, in-hospital and 90-day mortality (45 vs. 15.6%, p = 0.012; 55 vs. 28.6%, p = 0.035; 55 vs. 26%, p = 0.017, respectively). An independent association between baseline MFI < 2.6 and outcome was confirmed in a binary logistic analysis (odds ratio 4.594 [1.340–15.754], p = 0.015). A heart rate (HR) ≥ 90 bpm was an adjunctive predictor of mortality. However, a model with stepwise inclusion of mean arterial pressure < 65 mmHg, HR ≥ 90 bpm, lactate > 2 mmol/L and MFI < 2.6 did not detect significant differences in ICU mortality. In case an abnormal MFI was present on day 1, ICU mortality was significantly higher in comparison with patients with an abnormal MFI after day 1 (38 vs. 6%, p = 0.001), indicating a time-dependent significant difference in prognostic value.

Conclusions

In a general ICU population, an abnormal microcirculation at baseline is an independent predictor for mortality. In this setting, additional routine daily microcirculatory monitoring did not reveal extra prognostic information. Further research is needed to integrate microcirculatory monitoring in a set of commonly available hemodynamic variables.

Trial registration NCT 02649088, www.clinicaltrials.gov. Date of registration: 23 December 2015, retrospectively registered

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0411-9) contains supplementary material, which is available to authorized users.