Tissue Oxygen Consumption Research Articles

Simple Method for Improving the Sensitivity of Functional Near-Infrared Spectroscopy: A Simulation and Phantom Study

A novel method for canceling the skin blood flow in functional near-infrared spectroscopy is proposed to improve the accuracy of measurement of oxygen consumption in brain tissue. We use two approaches for applying cancellation signals. The sharing aperture approach uses cancellation signals detected at apertures for irradiating light, and the additional aperture approach uses the cancellation signals detected at the midpoint between the irradiation and detection apertures in the conventional measurement. We apply these methods using an equilateral-triangular probe arrangement. The cancellation signals for the additional aperture approach are detected at the triangle's center and this configuration reduces the number of probes. The characteristics of the cancellation signals are examined by simulation analysis and experiments with a phantom. The effect of the present approach is confirmed with a simple phantom study.

Здатність до деформації мембран еритроцитів у щурів різного віку при гіпоксії

Using modern ("laser tweezers", low ionic strength Liss, definition of microviscosity of erythrocyte membranes by fluorescence probe pyrene) and classical methods of investigation the osmotic resistance of red blood cells and protein membrane of red blood cells, the authors have esteblisheshed that deformation of the red blood cells in hemic hypoxia varies depending on the animals' age. The maximum capacity of red blood cells to deform was detected in rats of prepubertal period (40.2%). In the group of old rats this parameter reached the minimum level (19.7%). Age changes in erythrocyte membranes during hypoxia are manifested in an increase in the viscosity of the lipid bilayer (microviscosity index reduced in old rats compared with young adult animals by 69.5%) and an increase in the percentage of skeletal protein spectrin (by 53.0%). These changes determine the reduction in deformation capacity of red blood cells. The relationship between the age-related changes of erythrocyte membrane deformation and the state of regional microcirculation has been determined. In old rats a perfusion volume is reduced by 43.8%, the fractional volume of red blood cells passing per unit time through microvessels reduced by 59.3%, the proportion of oxygen consumption in tissues decreased by 6.6% and the perfusion of oxygen saturation decreased by 50.0%.

The effects of brief ischemia and reperfusion on interstitial PO2 in the rat spinotrapezius muscle

The involvement of oxygen in reactive hyperemia following brief periods of local flow arrest was investigated by measuring PO2 under conditions of different ischemic durations of 5, 15, 30, 60, and 300 sec. Spinotrapezius muscles of anesthetized male Sprague‐Dawley rats were used; the muscle was covered with a gas barrier film to isolate it from atmospheric oxygen. Well perfused sites were chosen with one or more arterioles and a capillary network. Phosphorescence quenching microscopy was used to measure interstitial PO2 with a topically applied phosphorescent probe. Localized ischemia was produced by rapidly inflating an airbag over the muscle; reperfusion was initiated by deflating the bag. Baseline PO2 varied between 52 and 60 mmHg. During ischemia, PO2 dropped to 45 mmHg for 5 s ischemia down to 3 mmHg for >;30 s ischemia. Maximum PO2 during the reperfusion phase ranged from 52 to 71 mmHg. The time required for PO2 recovery to baseline ranged from 9 (5 s ischemia) to 122 sec (300 s ischemia). These data exhibited a positive correlation between ischemic duration and the time for PO2 recovery, as well as to the maximum PO2 reached during reperfusion. The data will be used to establish a relationship between ischemic duration and tissue oxygen consumption (VO2) during reperfusion.Support: NHLBI grant HL18292

Стан і способи фармакологічної корекції киснезалежних процесів у тканинах пародонта при тривалому іммобілізаційному стресі

Influence of prolonged immobilization (6 h strict horizontal position of rats in the tight containers daily for 2 weeks) on oxygen tension, oxygen consumption, pro-/antioxidant balance, and energetic metabolism of soft and hard periodontal tissues has been investigated. It was established that prolonged immobilization stress resulted in marked decrease in the gum tissue PO2 (36%) and in the bone tissue oxygen consumption rate (46%) compared to control. It was also determined that prolonged stress led to a reduction in the gum mitochondrial respiration rate. The latter was more expressed in case of the NAD-dependent substrate oxidation than of the FAD- dependent one. It was determined that the prolonged stress results in intensification of peroxide processes and depletion of antioxidant protection of soft tissues of periodontum. It was found that Thiotriazolin and Actovegin have modified and diminished stress-induced disorders in the soft and hard periodontal tissues oxygen homeostasis under prolonged immobilization stress.

Effect of postmortem time on the metmyoglobin reductase activity, oxygen consumption, and colour stability of different lamb muscles

The aim of this research was to characterize the lamb M. longissimus dorsi (LD), M. semitendinosus (ST), and M. psoas major (PM) muscles for differences in instrumental colour, tissue oxygen consumption rate (OCR), mitochondrial respiration control ratio (RCR), metmyoglobin reductase activity (MRA), and the relative proportions of myoglobin (Mb) redox forms. LD, ST, and PM muscles were stored for 6 days at 4 °C. Changes in the instrumental colour (CIE L*-value, a*-value, b*-value, Chroma-value, and Hue-value), OCR, RCR, MRA, and relative proportions of Mb redox forms during storage were evaluated. LD revealed the lowest MetMb accumulation and highest colour stability. Muscles with higher colour stability had lower levels of OCR, higher MRA, and less MetMb accumulation. Colour stability and MRA for the lamb muscles were LD > ST > PM. The correlation coefficients among the main parameters were also investigated in this research. The correlation coefficients between a*-value and OxyMb within the same muscle were highly significant (r = 0.951, 0.974, 0.828; P < 0.05). MRA of the muscles was negatively correlated (r = −0.810, −0.942, −0.971, P < 0.05) with the relative percentage of MetMb. The results of the present study suggested that OCR, RCR and MRA contribute to variation in colour stability of different lamb muscles.

Thyroid Hormones Correlate with Basal Metabolic Rate but Not Field Metabolic Rate in a Wild Bird Species

Thyroid hormones (TH) are known to stimulate in vitro oxygen consumption of tissues in mammals and birds. Hence, in many laboratory studies a positive relationship between TH concentrations and basal metabolic rate (BMR) has been demonstrated whereas evidence from species in the wild is scarce. Even though basal and field metabolic rates (FMR) are often thought to be intrinsically linked it is still unknown whether a relationship between TH and FMR exists. Here we determine the relationship between the primary thyroid hormone triiodothyronine (T3) with both BMR and FMR in a wild bird species, the black-legged kittiwake (Rissa tridactyla). As predicted we found a strong and positive relationship between plasma concentrations of T3 and both BMR and mass-independent BMR with coefficients of determination ranging from 0.36 to 0.60. In contrast there was no association of T3 levels with either whole-body or mass-independent FMR (R2 = 0.06 and 0.02, respectively). In accordance with in vitro studies our data suggests that TH play an important role in modulating BMR and may serve as a proxy for basal metabolism in wild birds. However, the lack of a relationship between TH and FMR indicates that levels of physical activity in kittiwakes are largely independent of TH concentrations and support recent studies that cast doubt on a direct linkage between BMR and FMR.

Do we age faster in absence of gravity?

Do we age faster in absence of gravity?

Ropivacaine Decreases Tissue Oxygen Saturation Following Peripheral Nerve Block in Children

Background: Local anesthetics can cause vasoconstriction and disrupt neuronal impulses, reducing regional blood flow and increasing tissue oxygen consumption. This could alter regional oxygen supply and demand. Because microcirculation modifies during development and oxygen consumption kinetics differ between children and adults, we aimed to assess effects of ropivacaine Peripheral Nerve Block (PNB) on regional tissue saturation in children and young adults using Near-Infrared Spectroscopy (NIRS). Methods: Following Institutional Review Board approval and informed consent, 20 patients undergoing PNB for various orthopedic surgeries were studied. NIRS sensors were placed on the operative limb, contralateral limb, and forehead. Tissue saturations (rSO2) were recorded at baseline and every 5 minutes for 60 minutes following ropivacaine PNB. Mean rSO2 was assessed with repeated measures ANOVA. Correlation of tissue rSO2 with cerebral oximetry was calculated and significance determined with student’s t-test. Results: In all patients, blocked limb rSO2 decreased significantly compared to control limb 20 minutes after injection and remained lower. Control limb rSO2 and cerebral oximetry did not change over time. Non-blocked limb rSO2 demonstrated weak but significant correlation with cerebral oximetry while blocked limb rSO2 showed no correlation. Mean change in blocked limb rSO2 from baseline was significantly negative compared to a net positive mean change in the non-blocked limb. Conclusions: Decreased rSO2 following PNB suggests reduced local blood flow due to vasoconstriction, increased tissue oxygen consumption, or both. Changes in rSO2 provide an opportunity to develop NIRS as a non-invasive tool to identify successful PNB. Local anesthetic-induced decline in rSO2 could have implications in operative settings with ischemia or low-flow.

Leukocytes influence peripheral tissue oxygenation and perfusion in neonates

Background. Leukocyte counts may influence peripheral (micro) circulation due to changes in rheology. The aim of this study was to investigate a possible association between leukocyte counts and peripheral tissue oxygenation/perfusion measured with near infrared spectroscopy (NIRS) in term and preterm neonates.Methods. In this observational study we included term and preterm neonates within the first 2 months of life, in whom perip-heral tissue NIRS measurements were performed and blood samples (leukocytes and C reactive protein (CRP)) taken to investigate clinical signs of infection. Tissue-oxygenation index (TOI), fractional oxygen extraction (FTEO), oxygen delivery&nbsp;(DO2), oxygen consumption (VO2) and vascular resistance (VR) were measured by NIRS and venous occlusion method. TOI, FTOE, DO2, VO2 and VR were correlated to leukocyte counts on the same day and maximal CRP levels within 24 hours (CRP max).Results. In 180 infants, with a mean gestational age of 35.5±3.3 weeks, leukocyte counts were 16546± 8830/􀀁l (median 14830; range 1790 to 67840) and CRP max was 8.0± 19.0 mg/l (median 0.0; range 0.0 to 110.0mg/l).TOI was 71.1±5.5%, FTOE 28.5±6.1%, DO2 46.7±19.7, VO2 12.5±4.4 and VR 11.7±6.4.Leukocyte counts correlated negatively (r= -0.21; p= 0.005) with TOI and positively (r=0.17; p=0.029) with VR. Correlations with CRP max did not reach significance.Conclusion. We demonstrated that peripheral tissue oxygen consumption decreases and vascular resistance increases with increasing leukocyte counts.

Abstract P3-06-27: Dynamic tomographic optical breast imaging (TOBI) to monitor response to neoadjuvant therapy in breast cancer

Abstract Background: Near-infrared optical measurements have been recently shown to offer a promising non-invasive way for monitoring breast neoadjuvant chemotherapy (NAC) and predicting outcome. In particular, snapshots of tissue oxy and deoxy-hemoglobin concentration as well as water and lipid content have been demonstrated to be sensitive to therapy-induced changes. In this study, we extend optical measurements to capture additional hemodynamic and metabolic biomarkers revealed by dynamically imaging breast tissue during fractional mammographic compression. Using our dynamic tomographic optical breast imaging (TOBI) system we evaluate the early prediction performance of this advanced technology. Methods: We are conducting a pilot feasibility study in female patients with unilateral locally advanced breast cancer undergoing standard-of-care NAC. Pre-treatment and day 7 post-treatment TOBI scans are obtained, with additional (optional) scans on day 1 of each subsequent chemotherapy cycle. Both breasts are compressed in turn to 4–8 lbs of force, and optical images are acquired once every 2 seconds over two minutes. Time-resolved oxy-(HbO), deoxy-(HbR), and total-(HbT) hemoglobin concentration and hemoglobin oxygen saturation (SO2) are calculated. The compression-induced rate of change of HbT correlates with changes in tissue blood volume indicative of biomechanical properties. The evolution of tissue SO2 is modeled to obtain an index of the ratio of oxygen metabolism to blood flow. Therapy induced changes are quantified, and comparisons between changes in responders vs. non-responders are performed (response is defined here as &amp;gt;50% reduction in the largest tumor diameter). Results: We have enrolled 20 patients so far, of which 90% (N = 18) completed both the day 0 and day 7 scans. 17 patients have undergone surgery at this point. We focused our initial analysis on 5 HER2+ patients, of which two were non-responders, and three were responders according to our criteria. Four patients received taxol+herceptin+lapatinib, while the other received taxol+lapatinib only. In this small subgroup, the non-responders had an average increase of 1% in total hemoglobin concentration (HbT) from day 0 to day 7, while the responders had an average 12% decrease in HbT, respectively. We also noted different trends in the evolution of the tissue oxygen consumption to blood flow ratio, which increased 32% in non-responders from day 0 to day 7, while decreasing 11% in responders. Conclusions: The large percentage of enrolled patients that completed both initial scans demonstrates the feasibility of using dynamic optical breast tomography for breast neoadjuvant chemotherapy monitoring. Results in a small cohort of 5 HER2+ patients suggested a decreasing trend in HbT for responders as observed by previous studies. We also report for the first time an increase in the metabolic ratio of oxygen consumption to blood flow in non-responders vs. a decrease in responders. These initial results of our on-going study suggest that dynamic TOBI can detect changes due to treatment and may have predictive value for the treatment outcome and supports further studies of this non-invasive and portable tool for chemotherapy monitoring. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-27.

Клиническая картина, диагностика, комплексное лечение диабетической полинейропатии

Distal symmetric sensory-motor diabetic polyneuropathy (DPN) – the most common variant of diabetic neuropathy, which is expressed by more than 50 % of patients with diabetes mellitus (DM) 1 and type 2. The pathogenesis of DPN is the damaging effect of chronic hyperglycemia. Based on this key trends in the pathogenetic treatment of DPN are the normal levels of blood glucose, improved tissue perfusion and oxygen consumption, improve the rheological properties of blood, to restore normal energy balance, reducing the severity of oxidative stress.

Adipose tissue oxygen tension

The present review aims to address the role of adipose tissue oxygen partial pressure (PO2) in the metabolic and endocrine derangements in conditions characterized by insulin resistance. The balance between adipose tissue oxygen supply and its metabolic rate seems to determine adipose tissue PO2. Studies in ob/ob and dietary-induced obese mice have provided evidence for adipose tissue hypoxia in obesity, which has been explained by insufficient adipose tissue angiogenesis during the massive and rapid weight gain in these animals. However, conflicting data have been reported in humans, showing both increased and decreased adipose tissue PO2 in obese compared with lean individuals. Both low and high adipose tissue PO2 may induce a proinflammatory phenotype in (pre)adipocytes, but most studies have been performed under rather extreme PO2 levels, not reflecting human adipose tissue physiology. Furthermore, adipose tissue PO2 may affect glucose and lipid metabolism as well as adipogenic differentiation, but many issues still need to be addressed. Adipose tissue hypoxia has been demonstrated in animal models of obesity, but findings in humans are controversial and require further investigation. Although adipose tissue PO2 seems to be involved in metabolic and endocrine derangements in human adipose tissue, future studies should investigate how low and high adipose tissue PO2 within the human physiological range (3-11% O2) relates to adipose tissue blood flow and oxygen consumption, cellular metabolic responses, and the inflammatory phenotype.

Hypoxia inducible factor-1: its potential role in cerebral ischemia.

A divergence in the supply and consumption of oxygen in brain tissue initiates complex cycle of biochemical and molecular events resulting in neuronal death. To overcome such adverse situation, the tissue has to adopt some cellular mechanisms such as induction of various transcription factors, such as hypoxia inducible factor (HIF). It is a transcriptional regulator of oxygen homeostasis and key factor to generate the adaptive responses through upregulation of various target genes involved in the erythropoiesis, angiogenesis as well as glucose metabolism and transport. On the other hand, some studies do suggest that HIF also plays a detrimental role in ischemic reperfusion injury by inducing the pro apoptotic molecules, cytokines such as Nix, BNip3, and IL-20 which cause mitochondrial dysfunction leading to cell death. Hence, modulation of HIF-1 activity seems to provide an innovative therapeutic target to reduce the cellular damage, which arises from ischemic injury. Apart from traditional oxygen dependent HIF regulation, the focus has now shifted toward oxygen independent regulation in cell specific manner through reactive oxygen species involving hypoxia-associated factor, and heat shock protein 90, etc. Therefore, future development of such small molecule regulators for HIF-1 stability and signaling may prove useful to therapeutically target for enhancing recovery and repair in I/R injury.

Letter by Lecoultre and Tam Regarding Article, “Increased Adipose Tissue Oxygen Tension in Obese Compared With Lean Men Is Accompanied by Insulin Resistance, Impaired Adipose Tissue Capillarization, and Inflammation”

To the Editor: At odds with recent reports and reviews implicating adipose tissue (AT) hypoxia as a factor inducing AT dysfunction,1–4 Goossens et al5 published in Circulation a very elegant study suggesting that the impaired responsiveness of AT blood flow in obese patients is accompanied by reduced oxygen extraction and mitochondrial dysfunction leading to impaired tissue oxygen consumption. As a result, AT oxygen partial pressure is paradoxically higher in obese (≈67 mm Hg) versus lean (45 mm Hg) subjects, a condition referred as hyperoxic5 as opposed to normoxic. Interestingly, in both groups, Goossens et al reported wide ranges of Po2 (20–90 mm …

Mechanisms of blood flow and hypoxia production in rat 9L-epigastric tumors.

Classical descriptions of tumor physiology suggest two origins for tumor hypoxia; steady-state (diffusion-limited) hypoxia and cycling (perfusion-modulated) hypoxia. Both origins, primarily studied and characterized in murine models, predict relatively small, isolated foci or thin shells of hypoxic tissue interspersed with contrasting oxic tissue. These foci or shells would not be expected to scale with overall tumor size since the oxygen diffusion distance (determined by oxygen permeability and tissue oxygen consumption rate) is not known to vary dramatically from tumor to tumor. We have identified much larger (macroscopic) regions of hypoxia in rat gliosarcoma tumors and in larger human tumors (notably sarcomas and high-grade glial tumors), as indicated by biochemical binding of the hypoxia marker, EF5. Thus, we considered an alternative cause of tumor hypoxia related to a phenomenon first observed in window-chamber tumor models: namely longitudinal arteriole gradients. Although longitudinal arteriole gradients, as originally described, are also microscopic in nature, it is possible for them to scale with tumor size if tumor blood flow is organized in an appropriate manner. In this organization, inflowing blood would arise from relatively well-oxygenated sources and would branch and then coalesce to poorly-oxygenated outflowing blood over distances much larger than the length of conventional arterioles (multi-millimeter scale). This novel concept differs from the common characterization of tumor blood flow as disorganized and/or chaotic. The organization of blood flow to produce extended longitudinal gradients and macroscopic regional hypoxia has many important implications for the imaging, therapy and biological properties of tumors. Herein, we report the first experimental evidence for such blood flow, using rat 9L gliosarcoma tumors grown on the epigastric artery/vein pair.

Temperature-dependent feed requirements in farmed blue mussels (Mytilus edulisL.) estimated from soft tissue growth and oxygen consumption and ammonia-N excretion

Norwegian salmon production doubled from 0.43 million tons in 1999 to 0.86 million tons in 2009, with further growth expected. A considerable amount of the feed used is released into the surrounding waters as respiratory products, faeces and uneaten feed, and there is an increasing concern regarding the potentially negative impacts that this nutrient load may have. One of the major challenges for the sustainable development of salmon aquaculture is therefore to minimize waste discharges that may lead to degradation of the local marine environment. For this purpose, it has been suggested to cultivate extractive and filter feeding species, e.g. seaweed and mussels, close to fish farms in integrated multi-trophic aquaculture (IMTA), thereby contributing to a more ecologically balanced ecosystem approach in marine aquaculture.The primary objectives of this thesis were to investigate whether blue mussels (Mytilus edulis) can incorporate and utilize components of salmon fish feed and faeces particles for growth. The secondary objectives were to assess the ambient conditions for mussel cultivation in the coastal areas of Central Norway, and to test for the possibility of using land-based storage or creating non-toxic areas for storage of mussels at sea to meet a possible increase in mussel production from a development of IMTA in Norway. Mussels cleared salmon feed and faeces particles out of suspension with a high efficiency, suggesting that mussels can remove particulate wastes from salmon farming. In combination with a better growth for mussels fed salmon feed than faeces, a more pronounced incorporation of salmon feed compared to salmon faeces components in mussel tissues indicated that mussels will utilize salmon fish feed more efficiently than faeces particles in an integrated production with salmon.A one-year case study further revealed the incorporation of salmon fish feed in mussel tissues and five months with a higher soft tissue weight of mussels co-produced with salmon compared to control mussels, particularly during autumn and winter when phytoplankton concentrations were low, while control mussels demonstrated a higher soft tissue weight after peak phytoplankton levels in early summer. Mussels at the salmon farm showed a faster growth in length during the spring, while control mussels grew faster during the summer, thus resulting in equal growth rates for the fastest growing mussels co-produced with salmon and control mussels for the entire year. The results suggest that the combined production of mussels and salmon can be seen as a strategy to mitigate environmental effects of particulate nutrient wastes from salmon farming, and to maintain a higher soft tissue content of mussels during autumn and winter.Ambient Chl a concentrations in the coastal areas of Central Norway ranged bellow 2 μg L−1 after the spring bloom and were considered low. Food availability measured as suspended particulate matter (SPM) was, however, consistently above the threshold level of 4 mg L-1 for pseudo-faeces production in mussels of 1 g soft tissue dry matter, with an organic content of 32-44%, and did not appear to restrict mussel growth. SPM may therefore be an important food source to sustain mussel growth when phytoplankton concentrations are low.Temperature-dependent feed requirements were evident from significantly higher oxygen consumption and ammonia-N excretion rates at 14°C compared to 7°C at landbased storage conditions. Minimum feed requirements for the weight maintenance of mussels with 500 mg soft tissue dry matter is estimated at 240 and 570 μg C ind-1 h-1 at 7°C and 14°C, respectively. Mussels kept at land-based storage conditions maintained their soft tissue content and thus a high quality in early summer (May-June) while a significant decrease in soft tissue matter was evident among farmed mussels at sea in the same period. The results suggest that land-based storage can be used for obtaining a continuous mussel production in Norway independent of harvesting problems related to toxic algae blooms and extreme weather.Artificial upwelling in a stratified fjord resulted in an increased nutrient supply to euphotic waters and a correspondingly increase in phytoplankton biomass with a relative reduction of toxic algae. The increase in phytoplankton biomass was mainly represented by non-toxic dinoflagellates, and not diatoms, which was expected from an increased input of silicate from deep water. Nevertheless, the result is promising when it comes to creating controlled geographical areas with non-toxic food for storage of mussels and a continuous mussel production.

Medical near Infrared Spectroscopy 35 Years after the Discovery

Optical methods using visible and near infrared (NIR) light are a powerful tool for understanding human health and improving disease detection and treatment. The medical applications of optical methods are very old but as optical technologies advance, old medical applications evolve and new ones emerge. The main advantages of the optical methods are: non-invasive, no side-effects, good temporal and spatial resolution, real-time functional information, cost effective and portable. Optical methods rely on different types of interactions between visible or NIR light and biological tissue to provide structural, biochemical, physiological and morphological information. There are two main tissue optical properties which characterise light–tissue interactions and determine therapeutic or diagnostic outcome: absorption coefficient and reduced scattering coefficient. The penetration depth of visible and NIR light in tissue ranges from microns to centimetres depending on wavelength, source/detector separation, light delivery/collection geometry etc. The major tissue absorbers include: haemoglobin, lipids, melanin, water and proteins. Oxygenated and de-oxygenated haemoglobin (O2Hb; HHb) preferentially absorb visible and NIR light of different wavelengths, as evidenced by the more reddish colour of oxygenated blood and the more bluish hue of deoxygenated blood. O2Hb and HHb have distinct spectra, therefore optical measurements can provide information on tissue oxygenation, oxygen consumption and blood haemodynamics. Absorption and/or fluorescence NIR spectroscopy is utilised in different techniques with different resolution and penetration depth, such as conventional microscopy, confocal/multi-photon microscopy, optical coherence tomography (OCT), photodynamic therapy, “in vivo” molecular imaging and medical diffuse NIR optical spectroscopy/imaging. The main applications of medical NIR diffuse optical spectroscopy/imaging are: pulse oximetry, brain/muscle oximetry, functional brain cortex mapping and optical mammography. NIR light was utilised for the first time in pulse oximetry by Takuo Aoyagi in 1972. Pulse oximetry, an extremely simplistic version of reflectance spectroscopy, measures continuously arterial O2Hb saturation in the index finger or in other vascular districts and is considered the most significant technological advance ever made in monitoring the safety of patients during anaesthesia and critical care. Another step in expanding the usefulness of using NIR light in the medical field is represented by the discovery of medical NIR diffuse spectroscopy. Frans Jobsis is considered the founder of “in vivo” medical NIR spectroscopy. In 1977, he reported that the relatively high degree of transparency of brain tissue in part of the NIR range (700–1000 nm; the “optical window”) enables real-time non-invasive detection of regional haemoglobin oxygenation using trans-illumination spectroscopy.1 Starting in 1992 the opportunity of measuring quantitatively, by different NIR spectroscopy techniques, regional O2Hb saturation by NIR oximetry made it possible to monitor brain/muscle reserve capacity following tissue oxygen M. Ferrari, K.H. Norris and M.G. Sowa, J. Near Infrared Spectrosc. 20, vii–ix (2012)

Microcirculation and Macrocirculation in Cardiac Surgical Patients

Background. The aim of our study was to investigate the relationship between microcirculatory alterations after open cardiac surgery, macrohemodynamics, and global indices of organ perfusion. Methods. Patients' microcirculation was assessed with near-infrared spectroscopy (NIRS) and the vascular occlusion technique (VOT). Results. 23 patients undergoing open cardiac surgery (11 male/12 female, median age 68 (range 28–82) years, EuroSCORE 6 (1–12)) were enrolled in the study. For pooled data, CI correlated with the tissue oxygen consumption rate as well as the reperfusion rate (r = 0.56, P < 0.001 and r = 0.58, P < 0.001, resp.). In addition, both total oxygen delivery (DO2, mL/min per m2) and total oxygen consumption (VO2, mL/min per m2) also correlated with the tissue oxygen consumption rate and the reperfusion rate. The tissue oxygen saturation of the thenar postoperatively correlated with the peak lactate levels during the six hour monitoring period (r = 0.50, P < 0.05). The tissue oxygen consumption rate (%/min) and the reperfusion rate (%/min), as derived from the VOT, were higher in survivors compared to nonsurvivors for pooled data [23 (4–54) versus 20 (8–38) P < 0.05] and [424 (27–1215) versus 197 (57–632) P < 0.01], respectively. Conclusion. Microcirculatory alterations after open cardiac surgery are related to macrohemodynamics and global indices of organ perfusion.

The effect of red blood cell transfusion on tissue oxygenation and microcirculation in severe septic patients.

BackgroundMicrocirculation plays a vital role in the development of multiple organ failure in severe sepsis. The effects of red blood cell (RBC) transfusions on these tissue oxygenation and microcirculation variables in early severe sepsis are not well defined.MethodsThis is a prospective, observational study of patients with severe sepsis requiring RBC transfusions of one to two units of non-leukoreduced RBCs for a hemoglobin < 7.0, or for a hemoglobin between 7.0 and 9.0 with lactic acidosis or central venous oxygen saturation < 70%. This study took place in a 54-bed, medical-surgical intensive care unit of a university-affiliated hospital. Thenar tissue oxygen saturation was measured by using a tissue spectrometer on 21 patients, and a vaso-occlusive test was performed before and 1 hour after transfusion. The sublingual microcirculation was assessed with a Sidestream Dark Field device concomitantly on 11 of them.ResultsRBC transfusion resulted in increase in hemoglobin (7.23 (± 0.87) to 8.75 (± 1.06) g/dl; p < 0.001). RBC transfusion did not globally affect near-infrared spectrometry (NIRS)-derived variables. However, percent change in muscle oxygen consumption was negatively correlated with baseline (r = - 0.679, p = 0.001). There was no statistically significant correlation between percent change in vascular reactivity and baseline (p = 0.275). There was a positive correlation between percent change in oxygen consumption and percent change in vascular reactivity (r = 0.442, p = 0.045). In the 11 patients, RBC transfusion did not globally affect NIRS-derived variables or SDF-derived variables. There was no statistically significant correlation between percent change in small vessel perfusion and baseline perfusion (r = -0.474, p = 0.141), between percent change in small vessel flow and baseline flow (r = -0.418, p = 0.201), or between percent change in small vessel perfusion and percent change in small vessel flow (r = 0.435, p = 0.182).ConclusionsIn a small sample population, muscle tissue oxygen consumption, microvascular reactivity and sublingual microcirculation were globally unaltered by RBC transfusion in severe septic patients. However, muscle oxygen consumption improved in patients with low baseline and deteriorated in patients with preserved baseline. Future research with larger samples is needed to further examine the association between RBC transfusion and outcomes of patients resuscitated early in severe sepsis, with an emphasis on elucidating the potential contribution of microvascular factors.

Lung oxidative metabolism after exposure to ambient particles

The aim of this work was to study the time course of the oxidative metabolism in mice lung after exposure to ambient particles (ROFA). Swiss mice were intranasally instilled with a ROFA suspension (0.20mg/kg). Animals were sacrificed 1 or 3h after the exposure. Eighty percentage of increased oxygen consumption was observed in tissue cubes after 1h of exposure. This observation was accompanied by an increased NADPH oxidase activity (40%) and mitochondrial oxygen consumption in state 3 (19%). NO production by lung homogenates was found to be increased by 43% after 3h of exposure. Phospholipid oxidation in lung homogenates showed a 29% increase after 1h of exposure, while a 30% increase in the carbonyl content was found only after 3h of exposure. Our data show the relative importance of different sources of reactive oxygen species (NADPH oxidase activity and mitochondrial respiration) to the increased tissue oxygen consumption, oxidative damage and antioxidant status observed in an acute model of ROFA particles exposure.