Monitoring microcirculation.

The clinical relevance of microcirculation and its bedside observation started gaining importance in the 1990s since the introduction of hand-held video microscopes. From then, this technology has been continuously developed, and its clinical relevance has been established in more than 400 studies. In this paper, we review the different types of video microscopes, their application techniques, the microcirculation of different organ systems, the analysis methods, and the software and scoring systems. The main focus of this review will be on the state-of-art technique, CytoCam-incident dark-field imaging, and the most recent technological and technical updates concerning microcirculation monitoring.

The response of the microcirculation to mechanical support of the heart in critical illness.

Critical illness associated with cardiac pump failure results in reduced tissue perfusion in all organs and occurs in various conditions such as sepsis, cardiogenic shock, and heart failure. Mechanical circulatory support (MCS) devices can be used to maintain organ perfusion in patients with cardiogenic shock and decompensated chronic heart failure. However, correction of global hemodynamic parameters by MCS does not always cause a parallel improvement in microcirculatory perfusion and oxygenation of the organ systems, a condition referred to as a loss of hemodynamic coherence between macro- and microcirculation (MC). In this paper, we review the literature describing hemodynamic coherence or loss occurring during MCS of the heart. By using Embase, Medline Cochrane, Web of Science, and Google Scholar, we analyzed the literature on the response of MC and macrocirculation to MCS of the heart in critical illness. The characteristics of patients, MCS devices, and micro- and macrocirculatory parameters were very heterogenic. Short-term MCS studies (78%) described the effects of intra-aortic balloon pumps (IABPs) on the MC and macrocirculation. Improvement in MC, observed by handheld microscopy (orthogonal polarization spectral (OPS), sidestream dark-field (SDF), and Cytocam IDF imaging) in line with restored macrocirculation was found in 44% and 40% of the studies of short- and long-term MCS, respectively. In only 6 of 14 studies, hemodynamic coherence was described. It is concluded that more studies using direct visualization of the MC in short- and long-term MCS by handheld microscopy are needed, preferably randomized controlled studies, to identify the presence and clinical significance of hemodynamic coherence. It is anticipated that these further studies can enable to better identify patients who will benefit from treatment by mechanical heart support to ensure adequate organ perfusion.

Microcirculatory assessment of patients under VA-ECMO.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an effective technique for providing emergency mechanical circulatory support for patients with cardiogenic shock. VA-ECMO enables a rapid restoration of global systemic organ perfusion, but it has not been found to always show a parallel improvement in the microcirculation. We hypothesized in this study that the response of the microcirculation to the initiation of VA-ECMO might identify patients with increased chances of intensive care unit (ICU) survival. METHODS: Twenty-four patients were included in this study. Sublingual microcirculation measurements were performed using the CytoCam-IDF (incident dark field) imaging device. Microcirculatory measurements were performed at baseline, after VA-ECMO insertion (T1), 48-72 h after initiation of VA-ECMO (T2), 5-6 days after (T3), 9-10 days after (T4), and within 24 h of VA-ECMO removal. RESULTS: Of the 24 patients included in the study population, 15 survived and 9 died while on VA-ECMO. There was no significant difference between the systemic global hemodynamic variables at initiation of VA-ECMO between the survivors and non-survivors. There was, however, a significant difference in the microcirculatory parameters of both small and large vessels at all time points between the survivors and non-survivors. Perfused vessel density (PVD) at baseline (survivor versus non-survivor, 19.21 versus 13.78 mm/mm2, p = 0.001) was able to predict ICU survival on initiation of VA-ECMO; the area under the receiver operating characteristic curve (ROC) was 0.908 (95 % confidence interval 0.772-1.0). CONCLUSION: PVD of the sublingual microcirculation at initiation of VA-ECMO can be used to predict ICU mortality in patients with cardiogenic shock.

Monitoring microcirculation in critical illness.

PURPOSE OF REVIEW: Critical illness includes a wide range of conditions from sepsis to high-risk surgery. All these diseases are characterized by reduced tissue oxygenation. Macrohemodynamic parameters may be corrected by fluids and/or vasoactive compounds; however, the microcirculation and its tissues may be damaged and remain hypoperfused. An evaluation of microcirculation may enable more physiologically based approaches for understanding the pathogenesis, diagnosis, and treatment of critically ill patients. RECENT FINDINGS: Microcirculation plays a pivotal role in delivering oxygen to the cells and maintains tissue perfusion. Negative results of several studies, based on conventional hemodynamic resuscitation procedures to achieve organ perfusion and decrease morbidity and mortality following conditions of septic shock and other cardiovascular compromise, have highlighted the need to monitor microcirculation. The loss of hemodynamic coherence between the macrocirculation and microcirculation, wherein improvement of hemodynamic variables of the systemic circulation does not cause a parallel improvement of microcirculatory perfusion and oxygenation of the essential organ systems, may explain why these studies have failed. SUMMARY: Critical illness is usually accompanied by abnormalities in microcirculation and tissue hypoxia. Direct monitoring of sublingual microcirculation using hand-held microscopy may provide a more physiological approach. Evaluating the coherence between macrocirculation and microcirculation in response to therapy seems to be essential in evaluating the efficacy of therapeutic interventions.

The response of the microcirculation to cardiac surgery.

PURPOSE OF REVIEW: Cardiac surgery is associated with a wide range of microvascular derangements and with reduced tissue oxygenation. Although the macrohemodynamical targets during surgery may be achieved, the microcirculation may be damaged and remain dysfunctional. Direct observations of the microcirculation may enable more physiologically based approaches for diagnosis and treatment during cardiac surgery. RECENT FINDINGS: Microcirculation is the final destination of blood flow to the tissues for oxygen transport. Direct visualization of the microcirculation using hand-held microscopy can be considered the gold standard for tissue perfusion since the movement of single red blood cells can be observed and quantified. A new generation microcirculation-monitoring device is called CytoCam-Incident -Dark-Field imaging. This device has a high-resolution imaging sensor and shows approximately 30% more capillaries than the devices of the previous generations. On-pump and off-pump cardiac surgeries have induced different mechanism whose impact can be differentiated by observation of the sublingual microcirculation. Colloids may provide a better volume expansion and microcirculatory improvement than crystalloids although crytaloids may be more affective for hydration, and blood transfusions improves microcirculatory oxygenation by filling previously empty capillaries and reducing diffusion distances between oxygen carrying red blood cell and the parenchymal cells. SUMMARY: Direct visualization of the microcirculation using hand-held microscopy may provide the clinician the physiological feedback that is required for the early diagnosis and treatment of microcirculatory alterations during cardiac surgery. The coherence between the hemodynamic response of the macrocirculation and microcirculation during surgery seems to be essential.

Acute tuberculosis in the intensive care unit.

BACKGROUND/AIM: The aim of this study was to determine mortality rates and to evaluate clinical features of patients with active tuberculosis (TB) requiring intensive care unit (ICU) admission. MATERIALS AND METHODS: The medical records of active TB patients requiring ICU admission were retrospectively reviewed over a 5-year period. RESULTS: Sixteen patients with active TB admitted to the ICU were included in the study. Seven (43.8%) patients died in the ICU The cause of mortality was septic shock in 5 patients and respiratory failure in 2 patients. The Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores were higher in patients who died (P = 0.012 and 0.048, respectively). Six of the 8 immunosuppressed patients and 1 of the 8 nonimmunosuppressed patients died (P = 0.041). The median mechanical ventilation (MV) duration was longer in patients who died (11 (5-45) days) than in patients who survived (4.5 (3-7) days) (P = 0.036). Seven of the 8 patients with nosocomial infection and/or coinfection died, while all of the patients without additional infection survived (P = 0.01). CONCLUSION: Active TB patients admitted to the ICU had higher mortality rates, especially patients with immunosuppression, nosocomial infection, high APACHE II and SOFA scores, and patients receiving MV.