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Mechanistic effects of intraoperative blood flow-guided hemodynamic therapy remain poorly understood. Therefore, we aimed to determine the effects of a) maximizing stroke volume and b) maintaining preoperative resting cardiac index on oxygen delivery, oxygen consumption, and sublingual and abdominal microcirculatory tissue perfusion in major abdominal surgery patients. We randomized 76 patients to maximizing stroke volume, maintaining preoperative resting cardiac index, or routine care during and for the first 6 h after surgery. We measured oxygen delivery index, oxygen consumption index, sublingual microvascular flow index, and urethral perfusion index. At the end of surgery and 6 h after surgery, the median (25th percentile, 75th percentile) oxygen delivery index was higher in patients assigned to stroke volume maximization (460 (404, 556) ml/min/m2 and 503 (466, 595) ml/min/m2) or to preoperative cardiac index maintenance (507 (460, 664) ml/min/m2 and 516 (403, 604) ml/min/m2) than in patients assigned to routine care (403 (338, 517) ml/min/m2 and 390 (351, 510) ml/min/m2). There were no important differences in oxygen consumption index and sublingual microvascular flow index among the three groups. The intraoperative average urethral perfusion index was slightly higher in patients assigned to stroke volume maximization or to preoperative cardiac index maintenance than in patients assigned to routine care. In our trial, both maximizing stroke volume and maintaining preoperative resting cardiac index resulted in higher intraoperative and postoperative oxygen delivery index than routine care in major abdominal surgery patients. Large clinical trials are required to determine whether achieving higher perioperative oxygen delivery index translates into better outcomes. •There are various strategies for intraoperative blood flow-guided management.•Their effects on oxygen delivery and tissue perfusion are unclear.•Stroke volume maximization increased oxygen delivery.•Maintaining preoperative cardiac index increased oxygen delivery.•Both strategies increased abdominal microcirculatory tissue perfusion.

The objective of this study was to investigate the relationship between sublingual microcirculatory parameters and the severity of the disease in critically ill coronavirus disease 2019 (COVID-19) patients in the initial period of Intensive Care Unit (ICU) admission in a phase of the COVID-19 pandemic where patients were being treated with anti-inflammatory medication. In total, 35 critically ill COVID-19 patients were included. Twenty-one critically ill COVID-19 patients with a Sequential Organ Failure Assessment (SOFA) score below or equal to 7 were compared to 14 critically ill COVID-19 patients with a SOFA score exceeding 7. All patients received dexamethasone and tocilizumab at ICU admission. Microcirculatory measurements were performed within the first five days of ICU admission, preferably as soon as possible after admission. An increase in diffusive capacity of the microcirculation (total vessel density, functional capillary density, capillary hematocrit) and increased perfusion of the tissues by red blood cells was found in the critically ill COVID-19 patients with a SOFA score of 7–9 compared to the critically ill COVID-19 patients with a SOFA score ≤ 7. No such effects were found in the convective component of the microcirculation. These effects occurred in the presence of administration of anti-inflammatory medication.

COVID-19 is a systemic illness with widespread microcirculatory involvement. Nevertheless, reports about the characteristics of sublingual microcirculation in patients with COVID-19 are controversial. In fact, total vascular density has been described as decreased, normal, or increased. Our goal was to assess comprehensively the sublingual microcirculation in patients with COVID-19, comparing it with that of patients with non-COVID-19 ARDS and with healthy volunteers. This was a multicenter cross-sectional study. We included mechanically ventilated patients with ARDS secondary to either COVID-19 (n = 62) or non-COVID-19 ARDS (n = 20), from four intensive care units. We also studied healthy volunteers (n = 20). Sublingual microcirculation was assessed by videomicroscopy. Total vascular density was higher in COVID-19 ARDS than in the other groups (20.5 [18.4–21.7] vs. 17.6 [15.9–18.3] and 17.7 [16.6–19.4] mm/mm2, P < 0.001). Compared with non-COVID-19, COVID-19 group had less alterations in proportion of perfused vessels and microvascular flow index. A multivariate lineal analysis showed that total vascular density was independently associated with proportion of perfused vessels, SOFA score, base excess, and hematocrit. Patients with COVID-19 exhibited a distinctive pattern of sublingual microcirculation, mainly characterized by increased vascular density. This finding could be secondary to enhanced angiogenesis. •COVID-19 ARDS shows a unique phenotype of sublingual microcirculatory alterations.•It is characterized by increased vascular density with minor convective changes.•Non-COVID ARDS displays a different pattern despite similar arterial oxygenation.

Methylene blue (MB) has been proposed as an adjunctive therapy in the early management of septic shock; however, its effects on microcirculatory function remain poorly understood. This study aimed to investigate whether MB infusion improves sublingual microcirculatory parameters in patients with septic shock. In this single-center, randomized controlled trial, participants were allocated in a 1:1 ratio to either the MB group or the control group. The MB group received an intravenous bolus of 2 mg/kg MB over 15 minutes, followed by a continuous infusion of 1 mg/kg MB diluted in 500 mL of 0.9% saline via a central venous catheter for 12 hours. The control group received an equivalent volume of saline. The primary endpoint was the change in sublingual microcirculation parameters from baseline to 24 hours, assessed using a repeated-measures mixed-effects model. Secondary endpoints included 28-day organ support-free days and 28-day mortality. Among the 72 randomized participants, 70.8% (n=51) were male, with a mean age of 68.6±13.5 years. Following MB treatment, the mean microvascular flow index (MFI) in the MB group was 2.78, compared to 2.51 in the control group. MMRM analysis demonstrated that MB significantly improved MFI (least squares mean difference [95% CI]: 0.21 [0.09, 0.33], P=0.001), with significant increases observed as early as 1 hour post-intervention (T1: 0.24 [0.06, 0.42], P=0.009), and this effect persisted up to 24 hours (T24: P=0.005). However, no significant differences were observed between the groups in 28-day mortality (25.0% [9/36] vs 41.7% [15/36], P=0.200) or organ support-free days (20.0 [1.0-22.0] vs 16.0 [1.3-22.0], P=0.910). Although MB improved sublingual microcirculatory parameters, these improvements did not translate into benefits in organ function or survival outcomes. chictr.org.cn ChiCTR 2400081549.

Several autopsy studies showed microthrombi in pulmonary circulation of severe COVID-19 patients. The major limitation of these investigations is that the autopsy provided static information. Some of these alterations could be secondary to the disseminated intravascular coagulation (DIC) observed as the final standard route to the multisystem organ failure exhibited in critically ill patients. We report preliminary results of an in vivo evaluation of sublingual microcirculation in thirteen patients with severe COVID-19 requiring mechanical ventilation. We observed multiple filling defects moving within the microvessels indicative of thrombi in most of the cases 11/13 (85%). This is the first imaging documentation of microvascular thrombosis in living severe COVID-19 patients since the beginning of the hospitalization. The clinical relevance of microvascular thrombosis in this disease requires further research.

Type 1 diabetes is commonly associated with microvascular complications. Sublingual microcirculation examination using sidestream dark-field (SDF) imaging can reflect the situation in visceral microcirculation. The main goals of this observational study were to assess the feasibility of SDF imaging in children with compensated type 1 diabetes, determine selected sublingual microcirculation parameters, and compare them with parameters obtained in healthy children. In total 30 children with stable type 1 diabetes without clinical or laboratory signs of microvascular complications were included in the study, 15 males and 15 females in three age categories. Three video clips were recorded using an SDF probe from different parts of the sublingual area and analyzed by software-aided offline analysis. Videoclips were successfully recorded in all children. Compared with healthy children, the De Backer score (DeBS) in females and total vessel density (TVD), small vessel density (SVD), perfused vessel density (PVD), and perfused SVD (PSVD) in both genders were significantly lower in children with T1D. There were no differences in TVD, SVD, PVD, PSVD, and DeBS between age or gender categories. DeBS correlated with ketonemia; otherwise, no significant relationship was observed between microcirculatory and other recorded parameters. Sublingual microcirculation examination using SDF imaging is feasible in children with type 1 diabetes. Alteration of sublingual microcirculatory parameters is detectable in children with type 1 diabetes before they show clinical or laboratory signs of any microvascular complication. ClinicalTrials.gov identifier: NCT05958264.

Purpose Hemoglobin (Hb) transfusion thresholds are established in intensive care units. A restrictive transfusion threshold (Hb 70–75 g/l) is recommended in septic patients, and a liberal transfusion threshold (Hb 90 g/l) for cardiogenic shock. It is unclear whether these historically adopted transfusion thresholds meet the challenges of individual patients. Methods We evaluated microvascular flow index (MFI) and proportion of perfused vessels (PPV) in the sublingual microcirculation with CytoCam-IDF microscopy and near-infrared spectroscopy (NIRS). A study team-independent, treating intensivist assigned a total of 64 patients to 1 of 2 two transfusion thresholds, 43 patients to the Hb 75 g/l threshold and 21 patients to the Hb 90 g/l threshold, at a surgical intensive care unit. We performed microcirculatory measurements 1 h before and 1 h after transfusion of 1 unit of red blood cells. Results Microcirculatory flow variables correlated negatively with pre-transfusion flow variables (ΔMFI: ρ  = − 0.821, p  <  0.001; ΔPPV: ρ  = − 0.778, p  <  0.001). Patients with good initial microcirculation (cutoffs: MFI > 2.84, PPV > 88%) showed a deteriorated microcirculation after red blood cell transfusion. An impaired microcirculation improved after transfusion. At both transfusion thresholds, approximately one third of the patients showed an initially impaired microcirculation. In contrast, one third in every group had good microcirculation above the cutoff variables and did not profit from the transfusion. Conclusion The data suggest that the established transfusion thresholds and other hemodynamic variables do not reflect microcirculatory perfusion of patients. Blood transfusion at both thresholds 75 g/l and 90 g/l hemoglobin can either improve or harm the microcirculatory blood flow, questioning the concept of arbitrary transfusion thresholds.

Green light with a wavelength of 520 nm is commonly used in sidestream dark field (SDF) video microscopes for sublingual microcirculation assessment in clinical practice. However, blue light could obtain a clearer microcirculatory image due to a higher light absorption coefficient of hemoglobin. The aim of this study was to compare the sublingual microcirculatory image quality acquisition and related microcirculatory parameters between 520 nm green light and 415 nm blue light probes in the SDF device named MicroSee V100. Sublingual microcirculation films from twenty-one healthy volunteers were prospectively collected by blue light and green light probes, and only one video of each wavelength was recorded and analyzed in each volunteer. Moreover, 200 sublingual microcirculation films (100 by blue light probe and 100 by green light probe) of ICU patients were retrospectively scored for microcirculation image quality. Compared to green light, an increase in the perfused vessel density (paired t test, increased by 4.6 ± 4.7 mm/mm2, P < 0.0001) and total vessel density (paired t test, increased by 5.1 ± 4.6 mm/mm2, P < 0.0001) was observed by blue light in the healthy volunteers. The blue light probe had a significantly lower rate of unacceptable films than the green light probe in the 200 films of ICU patients (10/100 vs. 39/100, P < 0.0001). Blue light provides a higher microcirculatory vessel density and image quality than the existing SDF probe using green light.

To characterize the microvascular effects of a brief period of hyperoxia, in patients with septic shock and in healthy volunteers. In 20 patients with septic shock, we assessed systemic hemodynamics, sublingual microcirculation by SDF-videomicroscopy, and skin perfusion by capillary refill time (CRT), central-peripheral temperature (ΔT°), and perfusion index. Measurements were performed at baseline and after 5 min of inspired oxygen fraction of 1.00. Additionally, we studied 8 healthy volunteers, in whom hyperoxia was prolonged to 30 min. In septic patients, hyperoxia increased mean arterial pressure and systemic vascular resistance, but cardiac output remained unchanged. The only significant change in sublingual microcirculation was a decreased heterogeneity flow index (1.03 [1.01–1.07] vs 1.01 [0.34–1.05], P = .002). Perfused vascular density (13.1 [12.0–15.0] vs 14.0 [12.2–14.8] mm/mm2, P = .21) and the other sublingual microvascular variables were unmodified. CRT and ΔT° did not change but perfusion index slightly decreased. In healthy volunteers, sublingual microcirculation and skin perfusion were stable. Short-term hyperoxia induced systemic cardiovascular changes but was not associated with noticeable derangement in sublingual microcirculation and skin perfusion. Nevertheless, longer exposures to hyperoxia might have produced different results. •In septic shock, short-term hyperoxia increased systemic vascular resistance.•Sublingual microcirculation was unaffected by hyperoxia.•Concerning skin perfusion, only perfusion index was significantly decreased.•Since vascular resistance increased, ischemia might be present in other territories.•In volunteers, a longer hyperoxic exposure did not alter sublingual microcirculation.