Intestinal Tissue Oxygenation Research Articles

Disruption of intestinal oxygen balance in acute colitis alters the gut microbiome

ABSTRACT The juxtaposition of well-oxygenated intestinal colonic tissue with an anerobic luminal environment supports a fundamentally important relationship that is altered in the setting of intestinal injury, a process likely to be relevant to diseases such as inflammatory bowel disease. Herein, using two-color phosphorometry to non-invasively quantify both intestinal tissue and luminal oxygenation in real time, we show that intestinal injury induced by DSS colitis reduces intestinal tissue oxygenation in a spatially defined manner and increases the flux of oxygen from the tissue into the gut lumen. By characterizing the composition of the microbiome in both DSS colitis-affected gut and in a bioreactor containing a stable human fecal community exposed to microaerobic conditions, we provide evidence that the increased flux of oxygen into the gut lumen augments glycan degrading bacterial taxa rich in glycoside hydrolases which are known to inhabit gut mucosal surface. Continued disruption of the intestinal mucus barrier through such a mechanism may play a role in the perpetuation of the intestinal inflammatory process.

Photoacoustic imaging for non-invasive assessment of biomarkers of intestinal injury in experimental necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is an often-lethal disease of the premature infant intestinal tract, exacerbated by significant diagnostic difficulties. In NEC, the intestine exhibits hypoperfusion and dysmotility, contributing to disease pathogenesis. However, these features cannot be accurately and quantitively assessed with current imaging modalities. We have previously demonstrated the ability of photoacoustic imaging (PAI) to non-invasively assess intestinal tissue oxygenation and motility in a healthy neonatal rat model. In this first-in-disease application, we evaluated NEC using PAI to assess intestinal health biomarkers in an experimental model of NEC. NEC was induced in neonatal rats from birth to 4-days. Healthy breastfed (BF) and NEC rat pups were imaged at 2- and 4-days. Intestinal tissue oxygen saturation was measured with PAI, and NEC pups showed significant decreases at 2- and 4-days. Ultrasound and PAI cine recordings were used to capture intestinal peristalsis and contrast agent transit within the intestine. Intestinal motility, assessed using computational intestinal deformation analysis, demonstrated significant reductions in both early and established NEC. NEC damage was confirmed with histology and dysmotility was confirmed by small intestinal transit assay. This preclinical study presents PAI as an emerging diagnostic imaging modality for intestinal disease assessment in premature infants. Necrotizing enterocolitis (NEC) is a devastating intestinal disease affecting premature infants with significant mortality. NEC presents significant clinical diagnostic difficulties, with limited diagnostic confidence complicating timely and effective interventional efforts. This study is an important foundational first-in-disease preclinical study that establishes the utility for PAI to detect changes in intestinal tissue oxygenation and intestinal motility with NEC disease induction and progression. This study demonstrates the feasibility and exceptional promise for the use of PAI to non-invasively assess oxygenation and motility in the healthy and diseased infant intestine.

Application of near-infrared spectroscopy in the early identification of neonatal gastrointestinal diseases

Necrotizing enterocolitis (NEC) is one of the most common gastrointestinal diseases in neonatal intensive care units, characterized by rapid progression and a high mortality rate. Local intestinal ischemia and hypoxia are significant contributors to NEC. Feeding intolerance (FI), which refers to a range of gastrointestinal manifestations arising from the inability to tolerate enteral nutrition, is one of the most common clinical issues in neonates, and preventing and treating FI is crucial for improving neonatal survival rates. Near-infrared spectroscopy is a clinical tool that can be used at the bedside to monitor regional oxygen saturation. It is non-invasive, reliable, and sustainable, and its feasibility and safety in assessing intestinal blood circulation have been validated. Early identification of intestinal ischemia and differentiation of FI from precursor symptoms of NEC, as well as predicting the occurrence of NEC, are extremely important for reducing intestinal injury and adverse long-term outcomes. In recent years, there has been new research progress related to the monitoring of intestinal tissue oxygen saturation and cerebral oxygen saturation for the early identification of FI and precursor symptoms of NEC, and this article provides a review of these developments.

Measuring tissue oxygen saturation in the orad intestinal segment during equine colic surgery may aid in predicting the occurrence of postoperative ileus.

To assess the histological injury and intestinal microperfusion measured by laser Doppler flowmetry and spectrophotometry (LDFS) of the small intestine orad to a strangulation during colic surgery. Horses with naturally occurring small intestinal strangulations undergoing colic surgery were included. In this prospective clinical trial, intestinal tissue oxygen saturation (tSO2) and tissue blood flow (tBF) were measured by LDFS orad to the strangulation following release of the strangulation (n = 18). The number of horses with postoperative reflux (POR) and the cases that survived until discharge were compared between groups using Fisher's exact test (P < .05). Intestinal biopsies were taken in cases that underwent intestinal resection or intraoperative euthanasia (n = 28). Measurements were compared between injured and noninjured segments with a Mann-Whitney U or t test. The tSO2 and tBF of the orad intestine were lower than previously reported in healthy horses. Horses with low tSO2 of < 35% were significantly more likely to suffer from POR (6/6 cases) compared to cases with tSO2 > 69% (1/6). The number of horses that survived were not statistically different between these groups (2/6 and 6/6). All horses with mucosal injury developed POR (6/6), which was significantly more likely compared to horses without mucosal injury (3/13). No significant difference in tSO2 or tBF could be found between the segments with and without histological injury. The results suggest that measuring tSO2 in the orad segment during colic surgery may aid in predicting postoperative issues.

Biomarkers in the Severity of Necrotizing Enterocolitis in Preterm Infants: A Pilot Study.

The occurrence of necrotizing enterocolitis (NEC) is a common and severe disease of the digestive system in neonates. This study aims to assess the value of the intestinal tissue oxygen saturation (rintSO2) combined with the levels of procalcitonin (PCT) and mean platelet volume (MPV) in predicting the severity of NEC in preterm infants. This experiment was a retrospective cohort study conducted in the Department of Pediatrics, Hongqi Hospital Affiliated to Mudanjiang Medical University between January 2017 and July 2022. Premature neonates with NEC were enrolled and divided into mild-moderate NEC group and severe NEC group according to Bell's stage. The general information data, rintSO2 and blood parameters such as the white blood cell (WBC) count, platelet count (PLT), PCT, MPV, red blood cell distribution width (RDW), hemoglobin (Hb), C-reactive protein (CRP) were compared between the two groups. A total of 122 patients were enrolled, including 79 mild-moderate NEC and 43 severe NEC. The rintSO2 was lower in severe group than in mild-moderate group (P = 0.042), the PCT and MPV were both higher in severe group than in mild-moderate group (P = 0.048, P = 0.049). The results of logistic regression suggested that the rintSO2 (OR = 1.491, P = 0.003), PCT (OR = 3.071, P = 0.001) and MPV (OR = 4.027, P = 0.015) were independent predictive factors for severity of NEC. The area under the curve (AUC) of the rintSO2 combined with PCT and MPV showed good diagnostic ability in the severity of NEC. The rintSO2 combined with PCT and MPV may be considered as the early biomarkers in the severity of NEC and could help us to diagnose the case early with early treatment with better prognosis.

Comment on: Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Comment on: Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Author response to: Comment on: Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Author response to: Comment on: Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Cerebral and intestinal oxygen saturation of different volumes of red blood cell transfusion in preterm infants

ObjectivesThe purpose of this study was to investigate and compare the effects of 20 ml/kg and 15 ml/kg red blood cell transfusion (RBCT) on cerebral and intestinal tissue oxygenation, the number of administered transfusions, and neonatal complications in premature infants with anemia. MethodsThis prospective, randomized, partially blinded observational study investigated anemic neonates of gestational age < 32 weeks (Registration ID: ChiCTR 1,900,026,672). The infants were randomly assigned to receive 15 or 20 ml/kg red blood cell transfusion. Cerebral and intestinal tissue oxygen saturation (cer rSO2 and int rSO2) were collected 2 h before transfusion, 2, 4, 6, 12, 24, and 48 h after the beginning of transfusion by Near-infrared spectroscopy (NIRS). We also collected vital signs including heart rate (HR), peripheral oxygen saturation (SpO2), and mean arterial blood pressure (MABP) 2 h before infusion, 2 h, and 6 h after the beginning of transfusion. Then we analyzed and compared regional oxygen saturation(rSO2), fractional tissue oxygen extraction (FTOE), and other outcome readouts (blood transfusion numbers, changes in hematocrit and hemoglobin, hospitalization days, HR, SpO2, MABP, and complications) between the two groups. The intraindividual comparisons of the above readouts before transfusion and those after transfusion were also evaluated within each group. Result73 newborns received 20 ml/kg (large volume group) and 78 newborns received 15 ml/kg transfusion (small volume group). There was no significant difference in cer rSO2, int rSO2, Cerebral fractional tissue oxygen extraction (cFTOE), and intestinal fractional tissue oxygen extraction (iFTOE) between the two groups. rSO2, MABP, and SpO2 increased; HR, cFTOE, and iFTOE decreased following transfusion in both groups. The transfusion number of the large volume group is significantly less than that of the small volume group (1.9 ± 0.3 vs. 2.6 ± 0.9, p < 0.01) and hospitalization days were also less than those in the low volume group (44.3 ± 8.2 vs. 47.6 ± 9.8, p < 0.05). The increases in hematocrit and hemoglobin were higher in the large volume group than those in small volume (hematocrit increment (%),10.7 ± 4.2 vs. 10.1 ± 5.9, p = 0.015; Hb concentration after blood transfusion (g/L) 132.3 ± 11.1 vs. 127.4 ± 15.4, p = 0.028). ConclusionAfter the transfusion, cer rSO2 and int rSO2 increased significantly, FTOE decreased and vital signs improved in both the 15 ml/kg and 20 ml/kg groups, and these changes were not significantly different between the two groups. However, the larger group showed a more pronounced increase in hematocrit and hemoglobin, a reduction in the total number of transfusions, and a shorter duration of hospitalization after transfusion in preterm infants without increasing complications.

Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Non-invasive measurement of intestinal tissue oxygen saturation for evaluation of reconstructed blood flow in rectal cancer surgery: HiSCO-09 study.

Photoacoustic Imaging as a Novel Non-invasive Biomarker to Assess Intestinal Tissue Oxygenation and Motility in Neonatal Rats

BackgroundWithin the premature infant intestine, oxygenation and motility play key physiological roles in healthy development and disease such as necrotizing enterocolitis. To date, there are limited techniques to reliably assess these physiological functions that are also clinically feasible for critically ill infants. To address this clinical need, we hypothesized that photoacoustic imaging (PAI) can provide non-invasive assessment of intestinal tissue oxygenation and motility to characterize intestinal physiology and health. MethodsUltrasound and photoacoustic images were acquired in 2-day and 4-day old neonatal rats. For PAI assessment of intestinal tissue oxygenation, an inspired gas challenge was performed using hypoxic, normoxic, and hyperoxic inspired oxygen (FiO2). For intestinal motility, oral administration of ICG contrast agent was used to compare control animals to an experimental model of loperamide-induced intestinal motility inhibition. ResultsPAI demonstrated progressive increases in oxygen saturation (sO2) as FiO2 increased, while the pattern of oxygen localization remained relatively consistent in both 2-day and 4-day old neonatal rats. Analysis of intraluminal ICG contrast enhanced PAI images yielded a map of the motility index in control and loperamide treated rats. From PAI analysis, loperamide significantly inhibited intestinal motility, with a 32.6% decrease in intestinal motility index scores in 4-day old rats. ConclusionThese data establish the feasibility and application of PAI to non-invasively and quantitatively measure intestinal tissue oxygenation and motility. This proof-of-concept study is an important first step in developing and optimizing photoacoustic imaging to provide valuable insight into intestinal health and disease to improve the care of premature infants.

Value of near-infrared spectroscopy in monitoring intestinal tissue oxygen saturation in preterm infants with hemodynamically significant patent ductus arteriosus: a prospective research.

To study the change in regional oxygen saturation (rSO2) of intestinal tissue in preterm infants with hemodynamically significant patent ductus arteriosus (hsPDA) by near-infrared spectroscopy, and the clinical significance of the change in intestinal oxygen level in preterm infants with hsPDA. The preterm infants with patent ductus arteriosus (PDA) who had gestational age <32 weeks and/or birth weight <1 500 g were prospectively enrolled, who were admitted to the Department of Neonatology, Shenzhen Longgang Central Hospital from October 2017 to October 2020.According to the diagnostic criteria for hsPDA, the preterm infants with patent ductus arteriosus (PDA) were divided into two groups: hsPDA and non-hsPDA. According to closure of the ductus arteriosus after oral administration of ibuprofen, the preterm infants in the hsPDA group were subdivided into two groups: hsPDA closure and hsPDA non-closure. Hemodynamic parameters were measured at diagnosis of PDA and after treatment, and the level of intestinal tissue rSO2 was monitored continuously to analyze its change. A total of 241 preterm infants with PDA were enrolled, with 55 infants (22.8%) in the hsPDA group and 186 infants (77.2%) in the non-hsPDA group. There were 36 infants (65%) in the hsPDA closure group and 19 infants (35%) in the hsPDA non-closure group. Compared with the non-hsPDA group, the hsPDA group had a significantly higher left atrial diameter/aortic root diameter ratio and significantly lower left ventricular ejection fraction and fractional shortening (P<0.05). At each time point within 6 hours after diagnosis (1, 2, 4, and 6 hours), the hsPDA group had significantly lower intestinal tissue rSO2 than the non-hsPDA group (P<0.05), and intestinal tissue rSO2 gradually decreased over time in the hsPDA group (P<0.05), with the lowest level of 0.448±0.014 at 6 hours. Compared with the hsPDA non-closure group, the hsPDA closure group had a significantly lower left atrial diameter/aortic root diameter ratio and significantly higher left ventricular ejection fraction and fractional shortening (P<0.05). At each time point within 48-96 hours after treatment (48, 72, and 96 hours), the hsPDA closure group had significantly higher intestinal tissue rSO2 than the hsPDA non-closure group (P<0.05), and intestinal tissue rSO2 gradually increased since 24 hours after treatment in the hsPDA closure group (P<0.05), with the highest level of 0.578±0.031 at 96 hours. hsPDA has an impact on intestinal tissue oxygenation in preterm infants, and continuous monitoring of intestinal tissue rSO2 by near-infrared spectroscopy can help to guide the clinical management of hsPDA in preterm infants.

In Response.

We thank Weenink et al1 for their comments about our Open Mind article.2 We agree with their remarks and conclusion that it should be avoided that patients are exposed to 1.0 inspiratory oxygen fraction (Fio2) during anesthesia. While Weenink et al1 refers to the quantity of Fio2 in the intraoperative phase, our article and the statements made in it exclusively focused on the extubation period, which we felt is not covered in the literature so far. Clearly, improving oxygen therapy in acute-illness (IOTA) meta-analysis does not cover exactly the perioperative patient population. However, at least in tertiary (university) hospitals, a substantial number of patients during anesthesia are critically ill (American Society of Anesthesiologists [ASA] physical status ≥4) and are thus likely to resemble the IOTA population. We are convinced that focusing on evidence gathered (only) in surgical patients—as suggested by Weenink et al1—is not suitable to generate high-quality information about the effects of hyperoxia. Negative effects of hyperoxia rarely occur in healthy myocardium but in predamaged tissue—preferably in connection with coronary artery disease—as shown by our group.3 Likewise, the way oxygen is delivered to the patient could play a role in the assessment of hyperoxia and its effects. We cautiously expressed this fact2 in connection with the study of de Jonge3: while in their meta-analysis perioperative hyperoxia applied via tracheal intubation showed a positive effect on surgical site infections (SSI), in anesthetized patients with spontaneous ventilation, no such effect was seen, underlining a lack of convincing beneficial effect. We read with great interest the study of hemodiluted pigs—mentioned by Weenink et al1—where ischemic electrocardiogram (ECG) changes recover after administration of 1.0 Fio2. Our explanation is that a healthy pig with hemodilution has another reaction when exposed to high oxygen concentrations (eg, via a higher flow reserve) than a pig with stenotic coronary arteries, as demonstrated in the study by Guensch et al.4 There might be a considerable variation in response to hyperoxia, as another study with hemodiluted pigs showed improved intestinal tissue oxygenation but no improvement in portal venous base excess and lactate levels with high Fio2. While absence of harm of high perioperative Fio2 in the study of Mattishent is an important finding, other investigators as Staehr-Rye et al5 found increased respiratory complications with higher oxygen levels. Even in the absence of harm, we do believe that our interventions should be guided by clear indication and not by the absence of contraindication. The indication for perioperative oxygen therapy is prevention of hypoxia. If oxygen proves effective against SSIs, this indication has to be extended. However, available data are conflicting yet—the meta-analysis of de Jonge3 shows benefit, while a Cochrane systematic review of Wetterslev et al6 does not show benefit. What to believe now? Above considerations and the strong precautions against high oxygen levels in emergency medicine lead us to our opinion that, rather than producing ubiquitous hyperoxia, perioperative oxygen therapy needs to be tailored to the individual patient’s need. Daniel Gerber, MDDominik P. Guensch, MDGabor Erdoes, MD, PhDDepartment of Anesthesiology and Pain MedicineInselspital, Bern University HospitalUniversity of BernBern, Switzerland[email protected]

Predicting intestinal recovery after necrotizing enterocolitis in preterm infants.

Intestinal recovery after NEC is difficult to predict in individuals. We evaluated whether several biomarkers predict intestinal recovery after NEC in preterm infants. We measured intestinal tissue oxygen saturation (rintSO2) and collected urinary intestinal-fatty acidbinding protein (I-FABPu) levels 0-24 h and 24-48 h after NEC onset, and before and after the first re-feed. We assessed intestinal recovery in two ways: time to full enteral feeding (FEFt; below or equal/above group's median) and development of post-NEC complications (recurrent NEC/post-NEC stricture). We determined whether the rintSO2, its range, and I-FABPu differed between groups. We included 27 preterm infants who survived NEC (Bell's stage ≥ 2). Median FEFt was 14 [IQR: 12-23] days. Biomarkers only predicted intestinal recovery after the first re-feed. Mean rintSO2 ≥ 53% combined with mean rintSO2range ≥ 50% predicted FEFt < 14 days with OR 16.7 (CI: 2.3-122.2). The rintSO2range was smaller (33% vs. 51%, p < 0.01) and I-FABPu was higher (92.4 vs. 25.5 ng/mL, p = 0.03) in case of post-NEC stricture, but not different in case of recurrent NEC, compared with infants without complications. The rintSO2, its range, and I-FABPu after the first re-feed after NEC predicted intestinal recovery. These biomarkers have potential value in individualizing feeding regimens after NEC.

Early cerebral and intestinal oxygenation in the risk assessment of necrotizing enterocolitis in preterm infants.

Predicting necrotizing enterocolitis (NEC) might help in preventing its devastating consequences. We aimed to investigate whether early cerebral and intestinal tissue oxygen saturation (rSO2) and fractional tissue oxygen extraction (FTOE) predict the onset of NEC. Prospective observational case-control study. Infants with gestational age (GA) <32 weeks were included. For every NEC case we matched two controls based on GA, birth weight (BW), and a patent ductus arteriosus. Cerebral oxygenation and intestinal oxygenation were prospectively monitored two-hours daily during the first five days after birth and once a week thereafter until five weeks after birth or until NEC developed. We used Kaplan-Meier analyses to determine the ability of near-infrared spectroscopy (NIRS) measurements, including their variability, to predict the development of NEC. We included ten infants (median (range) GA 27.1 (24.6-29.4) weeks, BW 903 (560-1630) grams) who developed NEC at median postnatal day 13 (range: 4-43 days), and 20 matched controls. Infants with cerebral rSO2 <70% within the first 48 h after birth developed NEC significantly more often than infants with cerebral rSO2 ≥70% (odds ratio 9.00 (95% CI 1.33-61.14). Intestinal FTOE was higher in infants who developed NEC compared to controls during the last NIRS measurement at median 2 days (range: 1-7) before NEC onset (median 0.65 vs. 0.44). Cerebral oxygenation monitoring early after birth might be valuable in the risk assessment of NEC development. Additionally, our results suggest that intestinal oxygenation is impaired before the onset of clinical NEC.

Red Blood Cell Transfusions Affect Intestinal and Cerebral Oxygenation Differently in Preterm Infants with and without Subsequent Necrotizing Enterocolitis.

To assess intestinal and cerebral oxygenation during and after red blood cell (RBC) transfusions in preterms with or without subsequent transfusion-associated necrotizing enterocolitis (TANEC). In preterms of < 32 weeks' gestational age, we measured intestinal and cerebral regional tissue oxygen saturation (rintSO2, rcSO2) and their variabilities using near-infrared spectroscopy during and after transfusions. We compared eight infants who developed TANEC 6 to 48 hours after RBC transfusions with 16 controls. In TANEC infants, rcSO2 was lower during and after RBC transfusions than in controls, median (interquartile range) 55% (50-62) versus 72% (65-75), p < 0.01. There were no differences regarding rintSO2. Individual rintSO2 and rcSO2 ranges were smaller after transfusions in TANEC infants, 28% (9-36) versus 49% (40-65), p < 0.01, and 17% (14-33) versus 36% (26-57), p = 0.01, as was short-term rintSO2 variability. For each 10% higher rcSO2, the risk of developing TANEC decreased (odds ratio 0.09; 95% confidence interval 0.01-0.63). The smaller the rintSO2 range after transfusion, the higher the risk of developing TANEC. In preterm infants lower rcSO2, but not rintSO2, values during and after RBC transfusions are associated with TANEC. Lower rintSO2 and rcSO2 variabilities after RBC transfusions may represent a diminished capacity for vascular adaptation, possibly leading to TANEC.

Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion

BackgroundAim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO2) was reduced by reducing inspiratory oxygen fraction in steps of 5%. In part B hypovolemia was induced by controlled arterial exsanguination via roller pump (rate: 38 ml/kg/h). Mean arterial blood pressure (MAP), heart rate, pulmonary artery pressure, arterial and central venous blood gases and cardiac output were measured, cardiac index (CI) was calculated. Intestinal microperfusion and oxygenation were measured using laser Doppler flowmetry and white-light spectrophotometry. Surface probes were placed via median laparotomy on the stomach, jejunum and colon.ResultsPart A: Reduction in arterial oxygenation resulted in a sigmoid decrease in central venous oxygen partial pressure. At SaO2 < 80% no further decrease in central venous oxygen partial pressure occurred. Intestinal oxygenation remained unchanged until SaO2 of 80% and then decreased. Heart rate and pulmonary artery pressure increased significantly during hypoxemia. Part B: Progressive reduction in circulating blood volume resulted in a linear decrease in MAP and CI. Intestinal perfusion was preserved until blood loss resulted in MAP and CI lower 51 ± 5 mmHg and 40 ± 3 mL/kg/min, respectively, and then decreased rapidly.ConclusionsUnder isoflurane, intestinal tissue oxygenation remained at baseline when arterial oxygenation exceeded 80% and intestinal perfusion remained at baseline when MAP exceeded 51 mmHg and CI exceeded 40 mL/kg/min in this group of horses.Trial registry number33.14-42,502-04-14/1547.

Effects of dobutamine, dopamine, phenylephrine and noradrenaline on systemic haemodynamics and intestinal perfusion in isoflurane anaesthetised horses.

In the horse, effects of cardiovascular-active drugs on local perfusion of the gastrointestinal tract are poorly understood. To determine the effect of drugs commonly used to support blood pressure, on local intestinal blood flow and tissue oxygenation under isoflurane anaesthesia. In vivo randomised crossover experiment. Ten horses were anaesthetised with isoflurane. After 90 min of equilibration three doses (μg/kg bwt/min) of dobutamine (DOB 0.5/1/3), dopamine (DA 1/2/5), noradrenaline (NA 0.1/0.2/0.5) and phenylephrine (PHE 0.5/1/3) were infused for 15 min, in a randomised order, with a 45 min washout-period. Blood flow and tissue oxygenation (sO2 ) of jejunum, colon and stomach were measured using white light remission spectrophotometry and laser doppler flowmetry; heart rate (HR), mean arterial blood pressure (MAP), cardiac output (CO) were measured and systemic vascular resistance (SVR) calculated. Compared to baseline high dose dobutamine significantly increased CO, HR, MAP (P<0.001) and blood flow to the jejunum (+47 ± 26%, P = 0.001) and colon (+29 ± 15%, P<0.001) (mean ± s.d.). Dopamine (DA5) increased CO but decreased colonic blood flow (-39 ± 21% from baseline, P<0.001), as well as SVR and MAP compared to baseline (P<0.001). Noradrenaline had no significant influence on intestinal perfusion, but increased MAP and SVR from baseline (P<0.001). Phenylephrine (PHE3) caused a significant decrease in blood flow and sO2 , most profoundly at the colon compared to baseline (flow -44 ± 21%; sO2 -16 ± 3%, P<0.001), while MAP and SVR increased and CO and HR decreased (P<0.001). The measurement technique only allows for flow measurements in arbitrary units, which can limit comparability to other techniques. At the investigated doses dobutamine improved systemic and peripheral haemodynamics, while dopamine decreased MAP and peripheral perfusion. Noradrenaline increased MAP and SVR while peripheral blood flow was maintained, phenylephrine increased MAP, but reduced both local and systemic perfusion.

Blood transfusion in preterm infants improves intestinal tissue oxygenation without alteration in blood flow.

The objective of the study was to investigate the splanchnic blood flow velocity and oximetry response to blood transfusion in preterm infants according to postnatal age. Preterm infants receiving blood transfusion were recruited to three groups: 1-7 (group 1; n = 20), 8-28 (group 2; n = 21) and ≥29 days of life (group 3; n = 18). Superior mesenteric artery (SMA) peak systolic (PSV) and diastolic velocities were measured 30-60 min pre- and post-transfusion using Doppler ultrasound scan. Splanchnic tissue haemoglobin index (sTHI), tissue oxygenation index (sTOI) and fractional tissue oxygen extraction (sFTOE) were measured from 15-20 min before to post-transfusion using near-infrared spectroscopy. The mean pretransfusion Hb in group 1, 2 and 3 was 11, 10 and 9 g/dl, respectively. The mean (SD) pretransfusion SMA PSV in group 1, 2 and 3 was 0·63 (0·32), 0·81 (0·33) and 0·97 (0·40) m/s, respectively, and this did not change significantly following transfusion. The mean (SD) pretransfusion sTOI in group 1, 2 and 3 was 36·7 (19·3), 44·6 (10·4) and 41·3 (10·4)%, respectively. The sTHI and sTOI increased (P < 0·01), and sFTOE decreased (P < 0·01) following transfusion in all groups. On multivariate analysis, changes in SMA PSV and sTOI following blood transfusion were not associated with PDA, feeding, pretransfusion Hb and mean blood pressure. Pretransfusion baseline splanchnic tissue oximetry and blood flow velocity varied with postnatal age. Blood transfusion improved intestinal tissue oxygenation without altering mesenteric blood flow velocity irrespective of postnatal ages.

Quantitative analysis of mucosal oxygenation using ex vivo imaging of healthy and inflamed mammalian colon tissue.

Colonic inflammation is associated with decreased tissue oxygenation, significantly affecting gut homeostasis. However, the crosstalk between O2 consumption and supply in the inflamed tissue are not fully understood. Using a murine model of colitis, we analysed O2 in freshly prepared samples of healthy and inflamed colon tissue. We developed protocols for efficient ex vivo staining of mouse distal colon mucosa with a cell-penetrating O2 sensitive probe Pt-Glc and high-resolution imaging of O2 concentration in live tissue by confocal phosphorescence lifetime-imaging microscopy (PLIM). Microscopy analysis revealed that Pt-Glc stained mostly the top 50-60μm layer of the mucosa, with high phosphorescence intensity in epithelial cells. Measured O2 values in normal mouse tissue ranged between 5 and 35μM (4-28Torr), tending to decrease in the deeper tissue areas. Four-day treatment with dextran sulphate sodium (DSS) triggered colon inflammation, as evidenced by an increase in local IL6 and mKC mRNA levels, but did not affect the gross architecture of colonic epithelium. We further observed an increase in oxygenation, partial activation of hypoxia inducible factor (HIF) 1 signalling, and negative trends in pyruvate dehydrogenase activity and O2 consumption rate in the colitis mucosa, suggesting a decrease in mitochondrial respiration, which is known to be regulated via HIF-1 signalling and pyruvate oxidation rate. These results along with efficient staining with Pt-Glc of rat and human colonic mucosa reveal high potential of PLIM platform as a powerful tool for the high-resolution analysis of the intestinal tissue oxygenation in patients with inflammatory bowel disease and other pathologies, affecting tissue respiration.

Multisite Tissue Oxygenation Monitoring Indicates Organ-Specific Flow Distribution and Oxygen Delivery Related to Low Cardiac Output in Preterm Infants With Clinical Sepsis.

Cardiac output may be compromised in preterm infants with sepsis. Whether low cardiac output is associated with low tissue oxygen supply in these patients is unclear. The aim of the current study was to assess the association between cardiac output, assessed by echocardiography, and tissue oxygenation, measured with multisite near-infrared spectroscopy, in a cohort of preterm infants with clinical sepsis. Prospective observational cohort study. Level III neonatal ICU. Twenty-four preterm infants (gestational age < 32 wk) with clinical sepsis. None. Clinical and echocardiographic assessment of hemodynamics was performed within 48 hours of sepsis workup and repeated at least 24 hours later. We measured cerebral, renal, and intestinal tissue oxygen saturation using near-infrared spectroscopy during an hour of stable measurements directly preceding or following echocardiography and calculated fractional tissue oxygen extraction in each tissue. We determined Spearman correlation coefficients between fractional tissue oxygen extraction and right ventricular output corrected for patent foramen ovale flow, left ventricular output corrected for ductus arteriosus flow, and superior vena cava flow. Right ventricular output corrected for patent foramen ovale and left ventricular output corrected for ductus arteriosus flow both correlated significantly with intestinal fractional tissue oxygen extraction (ρ, -0.700; p = 0.036 and ρ, -0.604; p = 0.029, respectively). In contrast, no significant correlations were found between cardiac output measurements and cerebral and renal fractional tissue oxygen extraction, respectively. Changes in cardiac output measurements were not associated with observed changes in fractional tissue oxygen extraction values. Right ventricular output corrected for patent foramen ovale and left ventricular output corrected for ductus arteriosus flow, indicators of systemic blood flow in preterm infants with shunts, were negatively associated with intestinal fractional tissue oxygen extraction, but not with renal and cerebral fractional tissue oxygen extraction. These findings suggest that during low output states due to clinical sepsis intestinal perfusion is most at risk.