Impaired Tissue Perfusion Research Articles

Identifying risk factors for missed compartment syndrome in patients with tibia shaft fractures: An analysis of the national trauma data bank.

Acute compartment syndrome (CS) is a common complication of tibia shaft fractures (TSFs), and occurs when the pressure inside a myofascial compartment rises and impairs tissue perfusion. If treatment is delayed due to a missed diagnosis, amputation or permanent loss of function can result. This study aims to determine the incidence, clinical associations, and risk factors for missed CS following surgical stabilization of tibia shaft fractures (TSFs) using data from the National Trauma Data Bank (NTDB). NTDB data files from 2007 to 2016 were accessed to collect information on patients undergoing surgical fixation of TSFs. Patients with an Injury Severity Score (ISS) > 15 or inferred Gustilo-Anderson IIIB/IIIC fractures were excluded to create a more homogenous sample of lower-grade TSFs. Compartment syndrome that was originally missed leading to late intervention was the main outcome under investigation. Bivariate tests were used to assess the relationships between missed CS and the preoperative variables. If a variable and a complication had an association with a P≤0.2, it was included in a multivariate logistic regression model. A total of 184,612 patients met our inclusion criteria, and 1,269 patients (0.76%) had a missed CS diagnosis. Bivariate analysis demonstrated that male gender had a significant positive association with a missed CS diagnosis, while older age had a significant negative association (odds ratio [OR]=2.17, 0.99; P < 0.001). Multivariate analysis revealed that male gender was the most significant independent risk factor for a missed diagnosis of compartment syndrome (OR=1.84, P < 0.00001), followed by alcoholism, penetrating trauma, and smoking (OR=1.51, 1.46, 1.43; P < 0.02). The only significant protective factor was open fracture (OR=0.70, P < 0.0001). Our research identified several significant risk factors for missed CS after TSF, as well as positive and negative associations. Male gender, age, and lifestyle choices such as alcohol use and smoking conferred increased risks. These variables may assist physicians in identifying at-risk patients who may benefit from increased monitoring, and potentially prevent the high morbidity associated with this condition.

Impact on Abdominal Skin Perfusion following Abdominoplasty.

Background:Wound healing problems following abdominoplasty may be a result of impaired tissue perfusion. This study evaluated the impact a standard abdominoplasty may have on abdominal skin perfusion.Methods:A standard abdominoplasty was performed in 16 patients. Dynamic infrared thermography (DIRT) using a mild and a stronger cold challenge was performed pre-, intra-, and postoperatively on day 1, 2, and in week 6. The abdomen was divided into Huger’s vascular zones. A two-tailed t test was used to evaluate differences in mean temperature between zones. Statistical significance was defined as P < 0.05.Results:Two patients suffered wound healing problems. Abdominal skin perfusion showed a hyperaemic state on day 1, day 2, and week 6, postoperatively. Hotspots in zones I and II had all disappeared at the end of surgery and on day 1, except in the cranial part of zone I. Hotspots reappeared in zones I and II during day 2. A statistically significant difference between zones I and II was seen on day 1 and 2, with zone II being cooler. This difference had disappeared in week 6 for the mild cold challenge but not for the stronger cold challenge.Conclusions:A standard abdominoplasty has a significant impact on abdominal skin perfusion. The skin perfusion is a dynamic process with a gradual improvement over time. The strongest effect was seen in zone II near the lower transverse incision line, where skin perfusion was the least. Such may contribute to impaired wound healing at this site.

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass.

Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L. We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6). Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv. Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.

Inside Cover

AbstractBiophotonics technologies allow obtaining clinically important diagnostic information about pathological changes that occur in diabetes mellitus, including impaired tissue perfusion and oxygen saturation, structural and functional changes. A review presents the current state‐of‐the‐art in biophotonics technologies and their transfer to clinical use to identify the complications of diabetes mellitus, such as retinopathy, nephropathy, neuropathy, and cardiovascular disease as well as the methods used in the evaluation of foot ulceration and wound healing processes. Further details can be found in the article by Elena Zharkikh, Viktor Dremin, Evgeny Zherebtsov, Andrey Dunaev, and Igor Meglinski (e202000203).image

Inodilators in septic shock: should these be used?

Septic shock involves a complex interaction between abnormal vasodilation, relative and/or absolute hypovolemia, myocardial dysfunction, and altered blood flow distribution to the tissues. Fluid administration, vasopressor support and inotropes, represent fundamental pieces of quantitative resuscitation protocols directed to assist the restoration of impaired tissue perfusion during septic shock. Indeed, current recommendations on sepsis management include the use of inotropes in the case of myocardial dysfunction, as suggested by a low cardiac output, increased filling pressures, or persisting signals of tissue hypoperfusion despite an adequate correction of intravascular volume and mean arterial pressure by fluid administration and vasopressor support. Evidence supporting the use of inotropes in sepsis and septic shock is mainly based on physiological studies. Most of them suggest a beneficial effect of inotropes on macro hemodynamics especially when sepsis coexists with myocardial dysfunction; others, however, have demonstrated variable results on regional splanchnic circulation, while others suggest favorable effects on microvascular distribution independently of its impact on cardiac output. Conversely, impact of inodilators on clinical outcomes in this context has been more controversial. Use of dobutamine has not been consistently related with more favorable clinical results, while systematic administration of levosimendan in sepsis do not prevent the development of multiorgan dysfunction, even in patients with evidence of myocardial dysfunction. Nevertheless, a recent metanalysis of clinical studies suggests that cardiovascular support regimens based on inodilators in sepsis and septic shock could provide some beneficial effect on mortality, while other one corroborated such effect on mortality specially in patients with proved lower cardiac output. Thus, using or not inotropes during sepsis and septic shock remains as controversy matter that deserves more research efforts.

Identifying Risk Factors for Pressure Injury in Adult Critical Care Patients.

Critically ill patients have a variety of unique risk factors for pressure injury. Identification of these risk factors is essential to prevent pressure injury in this population. To identify factors predicting the development of pressure injury in critical care patients using a large data set from the PhysioNet MIMIC-III (Medical Information Mart for Intensive Care) clinical database. Data for 1460 patients were extracted from the database. Variables that were significant in bivariate analyses were used in a final logistic regression model. A final set of significant variables from the logistic regression was used to develop a decision tree model. In regression analysis, cardiovascular disease, peripheral vascular disease, pneumonia or influenza, cardiovascular surgery, hemodialysis, norepinephrine administration, hypotension, septic shock, moderate to severe malnutrition, sex, age, and Braden Scale score on admission to the intensive care unit were all predictive of pressure injury. Decision tree analysis revealed that patients who received norepinephrine, were older than 65 years, had a length of stay of 10 days or less, and had a Braden Scale score of 15 or less had a 63.6% risk of pressure injury. Determining pressure injury risk in critically ill patients is complex and challenging. One common pathophysiological factor is impaired tissue oxygenation and perfusion, which may be nonmodifiable. Improved risk quantification is needed and may be realized in the near future by leveraging the clinical information available in the electronic medical record through the power of predictive analytics.

Acute Effects of Transcatheter Aortic Valve Replacement on Central Aortic Hemodynamics in Patients With Severe Aortic Stenosis.

Severe aortic stenosis induces abnormalities in central aortic pressure, with consequent impaired organ and tissue perfusion. Relief of aortic stenosis by transcatheter aortic valve replacement (TAVR) is associated with both a short- and long-term hypertensive response. Counterintuitively, patients who are long-term normotensive post-TAVR have a worsened prognosis compared with patients with hypertension, yet the underlying mechanisms are not understood. We investigated immediate changes in invasively measured left ventricular and central aortic pressure post-TAVR in patients with severe aortic stenosis using aortic reservoir pressure, wave intensity analysis, and indices of aortic function. Fifty-four patients (mean age 83.6±6.2 years, 50.0% female) undergoing TAVR were included. We performed reservoir pressure and wave intensity analysis on invasively acquired pressure waveforms from the ascending aorta and left ventricle immediately pre- and post-TAVR. Following TAVR, there were increases in systolic, diastolic, mean, and pulse aortic pressures (all P<0.05). Post-TAVR reservoir pressure was unchanged (54.5±12.4 versus 56.6±14.0 mm Hg, P=0.30) whereas excess pressure increased 47% (29.0±10.9 versus 42.6±15.5 mm Hg, P<0.001). Wave intensity analysis (arbitrary units, au) demonstrated increased forward compression wave (64.9±35.5 versus 124.4±58.9, ×103 au, P<0.001), backward compression wave (11.6±5.5 versus 14.4±6.9, ×103 au, P=0.01) and forward expansion wave energies (43.2±27.3 versus 82.8±53.1, ×103 au, P<0.001). Subendocardial viability ratio improved with aortic function effectively unchanged post-TAVR. Increased central aortic pressure following TAVR relates to increased transmitted power and energy to the proximal aorta with increased excess pressure but unchanged reservoir pressure. These changes provide a potential mechanism for the improved prognosis associated with relative hypertension post-TAVR.

Indices of Tissue Perfusion: Triggers of Targets of Resuscitation?

Circulatory shock is characterized by a decrease in oxygen delivery to the tissues associated with impairment in oxygen metabolism and tissue hypoxia. Clinical and biological signs of impaired tissue perfusion and tissue hypoxia are used as bedside to detect circulatory failure and trigger resuscitation procedures. The most popular signs of tissue hypoperfusion include mean arterial pressure, capillary refill time and mottling score, central venous oxygen saturation (ScvO2), veno-arterial difference in PCO2 (PvaCO2), microcirculation assessment, and lactate. Both the severity and duration of the alterations in any of these variables are associated with a poor outcome so that it sounds logical to trigger therapy based on these. Using these variables as target for therapy is much more complex. Some of the limits for using some of these variables as targets include an incertitude about the target to reach (should we aim at normalizing or improving the variable, and by how much?) and the time lag between resolution of impaired tissue perfusion/hypoxia and normalization of the variable. The ideal target variable should have a well-defined end point and a rapid response time. Interestingly, hemodynamic resuscitation targeting these variables gave variable results. In this review, we will discuss the interest and limitations of the above-mentioned indices of tissue perfusion and hypoxia as trigger as well as end point of resuscitation in critically ill patients.

Blockade of mini-TrpRS for treatment of diabetic foot syndrome

Diabetic foot syndrome demonstrates wound chronicity due to impaired tissue perfusion in lower limbs. Previous studies showed interferon-gamma (IFN-γ), a central inflammatory mediator in diabetic foot syndrome, to induce the truncated form of tryptophanyl-tRNA synthetase (mini-TrpRS) that has strong angiostatic properties. Recently we reported that mini-TrpRS signalling could be blocked in the presence of IFN-γ with D-tryptophan in vitro. Here we discuss the IFN-γ/mini-TrpRS axis in the pathology of diabetic foot syndrome and emerging therapeutic options.

PDA: Does it matter?

Management of persistent patent ductus arteriosus (PDA) continues to be a challenging issue. The attitude toward PDA has shifted in the opposite direction during the last 20 years, from advocating an aggressive and early closure toward a call for watchful observation. While persistent PDA may cause challenges in the medical management of preterm neonates secondary to volume overload, pulmonary edema or hemorrhage, hypotension, and impaired tissue perfusion, its contribution toward long-term neonatal morbidities including bronchopulmonary dysplasia (BPD), ROP, NEC, and NDI has not been substantiated. By advocating conservative management, it is clear now that the majority of the PDA cases show spontaneous closure and do not require treatment. However, there has not been agreement regarding what constitutes a hemodynamically significant PDA and when, if any, it should be targeted for treatment. With increasing concern regarding possible associated complications with PDA ligation, a new trend for transcatheter approach to PDA closure is expanding. In this review, we summarize current understanding of the pathophysiology, diagnosis, and management of PDA in preterm infants, and we make some recommendations regarding evidence-based approach.

TCT-138 The Immediate Physiological Impact of Transcatheter Aortic Valve Replacement on Central Aortic Pressure in Patients With Severe Aortic Stenosis

Severe aortic stenosis (AS) causes abnormalities in central aortic pressure leading to impaired organ and tissue perfusion. This can be treated using transcatheter aortic valve replacement (TAVR), which can cause short- and long-term hypertensive response. Patients who are normotensive post-TAVR

Using of peripheral near infrared spectroscopy during vascular occlusion test to assess the microcirculatory response during cardiopulmonary bypass in pediatric cardiac surgery

Introduction The microvascular dysfunction after cardiac surgery with cardiopulmonary bypass (CPB) and impaired tissue oxygen saturation (StO2) have been associated with adverse patient outcome.(1)Measuring StO2 using near-infrared spectroscopy (NIRS) with a reproducible vascular occlusion test (VOT) has shown to be a noninvasive method suitable for assesment of microcirculation(2). The aim of this study was to assess microcirculatory function with NIRS using the VOT during cardiac surgery with cardiopulmonary bypass in pediatric patients. Methods 63 pediatric cardiac patients undergoing cardiac surgery with CPB were prospectively investigated. For cardiac surgical patients, NIRS parameters during the VOT were assessed before anesthesia (T1), after anesthesia (T2), full flow CPB (T3), after CPB (T4) and sternum closure (T5).VOT is including baseline, ischemia, reperfusion and return to baseline. Results There was significant difference in occlusion slope (rate of oxygen consumption) between T1 and T5 (p = 0,001), T2 and T5 (p = 0,001), T4 and T5 (p = 0,001). Reperfusion slope (representing microcirculatory vasoactive response to hypoxia) was significantly different T1 and T2 (p = 0,004), T1 and T3 (p = 0,001), T1 and T4 (p = 0,006), T2 and T3 (p = 0,01), T2 and T5 (p = 0,03), T3 and T5 (p = 0,002), T4 and T5 (p = 0,04). Reperfusion time was significant differences T1 and T3 (p = 0,03), T2 and T3 (p = 0,0019, T2 and T4 (p = 0,004), T3 and T5 (p = 0,001), T4 and T5 (p = 0,003). Discussion Intraoperative monitoring of peripheral microvascular reactivity enables detection of alterations in microcirculatory function thereby may contribute to preventing impaired tissue perfusion(3). The combination of VOT with NIRS monitoring showed CPB induced microvascular dysfunction in pediatric cardiac surgery.

Red blood cell storage and adhesion to vascular endothelium under normal or stress conditions: An in vitro microfluidic study.

Observational studies have identified an association between duration of red blood cell (RBC) storage and adverse outcomes in trauma. Hemorrhagic shock (HS) leads to impaired tissue perfusion which is associated with endothelial cell glycocalyx (eGC) shedding. Adhesion of stored RBC to the vascular endothelium has been shown to lead to impaired perfusion in the microcirculation and contribute to organ failure and poor outcome. The role of either or both of the EC and RBC glycocalyx in this process is unknown and was studied in an in vitro model. Human umbilical vein endothelial cells were perfused in a microfluidic device with RBC solutions from fresh, less than 14-day or longer than 21-day storage. In some experiments, the HS microenvironment was simulated by hypoxia-reoxygenation (H/R) and epinephrine (Epi) in the perfusion experiments. Measurements obtained included endothelial cell (EC) and RBC glycocalyx and RBC adherence to human umbilical vein endothelial cell monolayers at variable shear rates. Endothelial cell glycocalyx and RBC glycocalyx dimensions were reduced by H/R and Epi and storage duration respectively. Red blood cell adherence to the endothelium was increased by H/R + Epi treatment and duration of RBC storage. Our data may help explain some of the remaining discrepancies regarding the impact of RBC storage duration on outcomes in the trauma population. Consideration of the integrity of the EC and RBC glycocalyx may guide future transfusion strategies in the trauma population. The microfluidic device system platform may offer a high throughput modality to study emerging therapies to mitigate adverse consequence of RBC storage duration on the perfused endothelium in the trauma setting.

Retinal Tissue Perfusion in Patients with Multiple Sclerosis

ABSTRACTPurpose: The goal of this work was to determine whether the retinal tissue perfusion (RTP) is impaired in patients with multiple sclerosis (MS).Methods: Seventy-four patients [66 relapsing-remitting MS (RRMS) and 8 clinically isolated syndrome (CIS)] and 74 age- and gender-matched healthy controls were recruited. RTP was calculated as the retinal blood flow (measured using retinal function imager) supplying the macular area divided by the corresponding tissue volume of the inner retina from the inner limiting membrane to the outer plexiform layer, as measured by ultrahigh-resolution optical coherence tomography.Results: The RTP in the MS group was 2.37 ± 0.59 nl/s/mm3 (mean ± standard deviation), which was significantly lower than the control group (4.06 ± 0.89 nl/s/mm3, P < .001), reflecting a decrease of 42%. The blood flow volume was 2.50 ± 0.50 nl/s in MS, which was 45% lower than in the control group (4.56 ± 0.91 nl/s, P < .001). In addition, the tissue volume of the inner retina was significantly lower than in the control group (P < .05). The RTP in patients with MS was significantly correlated with the retinal blood flow volume (r = 0.84, P < .001) and retinal tissue volume (r = −0.56, P < .001). However, the retinal blood flow in patients with MS was not related to the tissue volume (r = −0.06, P = .59).Conclusions: Impaired retinal tissue perfusion occurred in patients with MS, which could be developed as a possible biomarker in monitoring disease progression in MS.

Peripheral tissue oxygenation and the number of organs transplanted per donor.

Current donor management practices target macrohaemodynamic parameters, but it is unclear if this leads to improvements in microvascular perfusion and tissue oxygenation; the latter may have more impact on organ status. In a recent preclinical study we determined that brain death impaired tissue perfusion and oxygen utilisation in swine while pharmacologic correction of these deficits improved organ function and reduced markers of tissue injury. As a first step in translating the preclinical findings, we conducted a prospective observational study to determine if there was an association between peripheral tissue oxygenation (measured by near-infrared spectroscopy) in deceased by neurological criteria human donors and the number of organs transplanted. In 60 donors, the mean time-weighted average of tissue oxygenation was 87.5% (standard deviation, SD, 5.2%) and the average number of organs transplanted was 3.5 (SD 2); there was a positive linear relationship between these two parameters. A 5% rise in tissue oxygenation was associated with an increase of 0.47 organs transplanted (95% confidence intervals 0.16 to 0.78) after adjusting for age (<i>P</i>=0.004). No such correlations were observed for the macrohaemodynamic or macro-oxygenation parameters (including arterial blood oxygenation). The results of this clinical trial are consistent with our preclinical work and support the postulate that targeting the microvasculature to improve tissue perfusion and tissue oxygen delivery in human donors has the potential to increase the quantity of organs suitable for transplant.

Noninvasive quantitative assessment of microcirculatory disorders of the upper extremities with 2D fluorescence optical imaging.

Quantitative Imaging of microcirculatory disorders is challenging. To investigate the feasibility of 2D Fluorescence Optical Imaging (FOI) for characterization and quantification of microcirculatory disorders in peripheral arterial occlusive disease (PAOD) of the upper extremity. 9 patients with various clinical presentations of PAOD of the upper extremity were included. Quantitative analysis of both hands was performed by assessing the fluorescence intensity of Indocyanine Green (ICG) dynamically over a time period of 360 seconds. Analysis of the signal intensity within multiple regions of both hands was calculated and time-dependent perfusion curves for each region of interest were plotted over time. Compared to the healthy, vascular non-impaired segments, pathological segments with an impaired tissue perfusion were identified through a decreased rate of early tissue enhancement (p = 0.02) and increased signal intensity of the optical perfusion agent per second (p < 0.001). The affected segments showed a decreased maximum signal intensity and a prolonged interval to reach the maximum signal intensity (time to peak). 2D FOI allows quantitative assessment of the peripheral microcirculation in various vascular pathophysiologies and is able to detect the impaired tissue perfusion in patients with vascular disorders of the upper extremity.

Can lactate levels be used as a marker of patent ductus arteriosus in preterm babies?

Serum lactate levels provide information on metabolic capacity at the cellular level. In addition, lactate reflects tissue perfusion and oxygenation status. The aim of this study was to determine the usefulness of high lactate levels as a marker in hemodynamically significant patent ductus arteriosus (hsPDA), which may lead to tissue perfusion defects. Preterm infants with gestational age ≤32weeks and birthweight ≤1500g were included. Lactate levels were determined at postnatal 48-72hours before echocardiographic evaluation. Eligible infants were divided into two groups as infants with and without hsPDA. Cut-off values for lactate were taken as lactate >4mmol/L, identified as a high lactate level. Infants were also divided into two groups according to lactate levels as group I: lactate levels >4mmol/L and group II: lactate levels ≤4mmol/L. Haemodynamic PDA and lactate levels were compared. A total of 119 patients with gestational age ≤32weeks and birthweight ≤1500g were included in the study. Fifty patients had echocardiographic hsPDA and 69 patients had no PDA. Twelve (24%) of the patients with hsPDA and 22 (31.9%) of the non-hsPDA patients had a lactate level of 4mmol/L (P=0.392). There was no correlation between hsPDA presence and lactate levels (P=0.35). High lactate levels are multifactorial and usually indicate impairment of tissue perfusion. There are a number of factors that can lead to impaired tissue perfusion in preterm infants. For the first time in this study, it was shown that lactate levels did not significantly increase in the presence of hemodynamically significant PDA. This may be due to the fact that peripheral tissue perfusion in the presence of hemodynamic PDA does not deteriorate enough to cause an increase in anaerobic metabolism.

Blood lactate increases with the progression of mitral valve disease in dogs

ABSTRACT: In dogs with congestive heart failure, the upregulated sympathetic tone causes vasoconstriction that impairs peripheral blood supply, therefore causing the accumulation of lactate. In this prospective cross-sectional study with a longitudinal component, blood lactate was quantified in 10 healthy and 34 myxomatous mitral valve disease (MMVD) dogs to investigate its potential use as a diagnostic and prognostic biomarker. While there were no differences in lactate concentration between control animals and stages B1 (3.31±0.62mmol/L) and B2 (3.32±0.46mmol/L) dogs, significant differences were found between healthy (2.50±0.69mmol/L) and both C (3.99±0.47mmol/L) and D (6.97±1.23mmol/L) animals. When a cut-off of 3.35mmol/L was used, lactate was able to distinguish dogs with normal and remodeled hearts with a sensitivity of 78.2% and specificity of 63.6%. Also, significant correlations existed between lactate and indicators of cardiac remodeling. Finally, animals with blood lactate &lt;3.5mmol/L carried a better prognosis when compared with dogs in which lactate was &gt;5.0mmol/L. Our results suggest that the progression of MMVD results in accumulation of lactate within the bloodstream, which is likely attributable to the impaired peripheral tissue perfusion. In MMVD dogs, blood lactate may be used as a surrogate for cardiac remodeling, and an increased concentration is associated with a worse prognosis regarding the time to evolve into congestive heart failure.

Transient hyperlactatemia during intravenous administration of glycerol: a prospective observational study

BackgroundIntravenous glycerol treatment, usually administered in the form of a 5% fructose solution, can be used to reduce intracranial pressure. The administered fructose theoretically influences blood lactate levels, although little is known regarding whether intravenous glycerol treatment causes transient hyperlactatemia. This study aimed to evaluate blood lactate levels in patients who received intravenous glycerol or mannitol.MethodsThis single-center prospective observational study was performed at a 14-bed general intensive care unit between August 2016 and January 2018. Patients were excluded if they were < 20 years old or had pre-existing hyperlactatemia (blood lactate > 2.0 mmol/L). The included patients received intravenous glycerol or mannitol to reduce intracranial pressure and provided blood samples for lactate testing before and after the drug infusion (before the infusion and after 15 min, 30 min, 45 min, 60 min, 90 min, 120 min, and 150 min).ResultsAmong the 33 included patients, 13 patients received 200 mL of glycerol over 30 min, 13 patients received 200 mL of glycerol over 60 min, and 7 patients received 300 mL of mannitol over 60 min. Both groups of patients who received glycerol had significantly higher lactate levels than the mannitol group (2.8 mmol/L vs. 2.2 mmol/L vs. 1.6 mmol/L, P < 0.0001), with the magnitude of the increase in lactate levels corresponding to the glycerol infusion time. There were no significant inter-group differences in cardiac index, stroke volume, or stroke volume variation. In the group that received the 30-min glycerol infusion, blood lactate levels did not return to the normal range until after 120 min.ConclusionsIntravenous administration of glycerol leads to higher blood lactate levels that persist for up to 120 min. Although hyperlactatemia is an essential indicator of sepsis and/or impaired tissue perfusion, physicians should be aware of this phenomenon when assessing the blood lactate levels.

Predicting retinal tissue oxygenation using an image-based theoretical model

Impaired oxygen delivery and tissue perfusion have been identified as significant factors that contribute to the loss of retinal ganglion cells in glaucoma patients. This study predicts retinal blood and tissue oxygenation using a theoretical model of the retinal vasculature based on confocal microscopy images of the mouse retina. These images reveal a complex and heterogeneous geometry of vessels that are distributed non-uniformly into multiple distinct retinal layers at varying depths. Predicting oxygen delivery and distribution in this irregular arrangement of retinal microvessels requires the use of an efficient theoretical model. The model employed in this work utilizes numerical methods based on a Green's function approach to simulate the spatial distribution of oxygen levels in a network of retinal blood vessels and the tissue surrounding them. Model simulations also predict the blood flow rates and pressures in each of the microvessels throughout the entire network. As expected, the model predicts that average vessel PO2 decreases as oxygen demand is increased. However, the standard deviation of PO2 in the vessels nearly doubles as oxygen demand is increased from 1 to 8 cm3 O2/100 cm3/min, indicating a very wide spread in the predicted PO2 levels, suggesting that average PO2 is not a sufficient indicator of oxygenation in a heterogeneous vascular network. Ultimately, the development of this mathematical model will help to elucidate the important factors associated with blood flow and metabolism that contribute to the vision loss characteristic of glaucoma.