Measurement of the liver tissue oxygenation by near-infrared spectroscopy

Comparing liver and lower abdomen near-infrared spectroscopy in preterm infants

BACKGROUND

Near-infrared spectroscopy (NIRS) is being increasingly used to investigate regional oxygenation (rSO₂) and perfusion in areas such as the abdomen in preterm infants prone to feeding intolerance. Lower abdominal rSO₂ values are extremely variable, high sensitivity and currently low specificity tools. The liver, a solid organ, could provide a more reliable site for splanchnic oxygenation and perfusion monitoring.

AIMS

Compare liver and lower abdomen rSO₂ values in stable preterm infants in response to feeding.

STUDY DESIGN

We prospectively evaluated the correlation between rSO₂ over the liver and lower abdomen in 16 preterm infants born between 28 and 32 weeks' gestational age using 48 h of continuous NIRS data.

OUTCOME MEASURES

Mean liver and lower abdomen rSO₂ values.

RESULTS

The overall mean liver rSO₂ were higher than the overall mean lower abdomen values, 78.4 ± 7.1 vs. 65.1 ± 24.9 respectively. Time series analysis showed a mean maximum cross correlation between the liver and lower abdomen of 0.28 (SD ± 0.03; p < 0.001); the liver signal lagged the lower abdomen by an average of 5.4 s (SD ± 1.2 s, Range 0-16 s). Mixed models analysis showed that during bolus feeding, liver values increased 10 to 30 min after the start of feeding (p < 0.01) while lower abdomen increased from 20 to 60 min after the start of feeding (p < 0.05) and liver values were less variable than lower abdomen values.

CONCLUSION

Liver rSO₂ appears to be a more stable surrogate for splanchnic oxygenation and perfusion than lower abdomen rSO₂.

Optical percutaneous needle biopsy of the liver: a pilot animal and clinical study

This paper presents the results of the experiments which were performed using the optical biopsy system specially developed for in vivo tissue classification during the percutaneous needle biopsy (PNB) of the liver. The proposed system includes an optical probe of small diameter acceptable for use in the PNB of the liver. The results of the feasibility studies and actual tests on laboratory mice with inoculated hepatocellular carcinoma and in clinical conditions on patients with liver tumors are presented and discussed. Monte Carlo simulations were carried out to assess the diagnostic volume and to trace the sensing depth. Fluorescence and diffuse reflectance spectroscopy measurements were used to monitor metabolic and morphological changes in tissues. The tissue oxygen saturation was evaluated using a recently developed approach to neural network fitting of diffuse reflectance spectra. The Support Vector Machine Classification was applied to identify intact liver and tumor tissues. Analysis of the obtained results shows the high sensitivity and specificity of the proposed multimodal method. This approach allows to obtain information before the tissue sample is taken, which makes it possible to significantly reduce the number of false-negative biopsies.

Changes to hepatic tissue oxygenation, abdominal perfusion and its association with enteral feeding with liberal transfusion threshold in anaemic preterm infants: A prospective cohort study

BACKGROUND AND OBJECTIVES

In anaemic preterm infants who receive packed red blood cell (PRBC) transfusions, changes to mesenteric tissue oxygenation and perfusion have been reported using a restrictive haemoglobin (Hb)-based threshold. We aimed to investigate changes to hepatic tissue oxygenation and abdominal blood flow after PRBC transfusion and its association with enteral feeding using a liberal Hb threshold (as shown inTable1). [Table: see text] MATERIAL AND METHODS: We prospectively studied a cohort of preterm infants born at < 32 weeks' gestation who received at least one PRBC transfusion and monitored them immediately before (Time 1), immediately after (Time 2) and 24 hours after transfusion (Time 3). Data obtained included physiological parameters, the hepatic tissue oxygenation index and pulsed Doppler ultrasound measurements in the abdominal arterial circulation. Additionally, the effects of withholding enteral feeds were investigated.

RESULTS

We monitored 50 PRBC transfusion episodes in 40 preterm infants, in whom the mean gestational age was 26.72 weeks (±1.6 weeks) and the mean birth weight was 855.25 g (±190.7 g). We observed significant changes to pulsed Doppler measurements in abdominal arterial circulation (coeliac artery mean peak systolic velocity Time 2 [75.08 cm/sec] versus Time 3 [71.13 cm/sec]; mean end-diastolic velocity Time 2 [15.71 cm/sec] versus Time 3 [13.76 cm/sec]; mean resistive index Time 2 0.78 versus Time 3 0.80, right renal artery mean peak systolic velocity Time 1 58.28 cm/sec versus Time 2 50.97 cm/sec, left renal artery mean peak systolic velocity Time 1 49.20 cm/sec versus Time 2 45.40 cm/sec), but not to hepatic tissue oxygenation after PRBC transfusion (Time 1 mean 53.66 [SD, 13.34]; Time 2 mean 54.93 [SD, 9.3]; Time 3 mean 55.64 [SD, 12.86]). There were no changes to hepatic tissue oxygenation or mesenteric blood flow from withholding enteral feeds during PRBC transfusion. There were no local adverse effects from hepatic tissue oxygenation monitoring.

CONCLUSION

In mildly anaemic preterm infants, when allowing a liberal Hb threshold-based trigger for PRBC transfusion, changes in abdominal arterial circulation were present, but not in hepatic tissue oxygenation. Withholding enteral feeds during PRBC transfusion had no impact on hepatic tissue oxygenation or mesenteric flows.

Measurement of gut oxygenation in the neonatal population using near-infrared spectroscopy: a clinical tool?

CONTEXT

Near-infrared spectroscopy (NIRS) is a non-invasive bedside monitor of tissue oxygenation that may be a useful clinical tool in monitoring of gut oxygenation in newborn infants.

OBJECTIVE

To systematically review literature to determine whether NIRS is a reliable tool to monitor gut oxygenation on neonatal units.

DATA SOURCES

PubMed and Embase databases were searched using the terms 'neonate', 'preterm infants', 'NIRS' and 'gut oxygenation' (2001-2018).

STUDY SELECTION

Studies were included if they met inclusion criteria (clinical trial, observational studies, neonatal population, articles in English and reviewing regional gut oxygen saturations) and exclusion criteria (not evaluating abdominal NIRS or regional oxygen saturations).

DATA EXTRACTION

Two authors independently searched PubMed and Embase using the predefined terms, appraised study quality and extracted from 30 studies the study design and outcome data.

LIMITATIONS

Potential for publication bias, majority of studies were prospective cohort studies and small sample sizes.

RESULTS

Thirty studies were reviewed assessing the validity of abdominal NIRS and potential application in neonates. Studies reviewed assessed abdominal NIRS in different settings including normal neonates, bolus and continuous feeding, during feed intolerance, necrotising enterocolitis and transfusion with packed red cells. Several observational studies demonstrated how NIRS could be used in clinical practice.

CONCLUSIONS

NIRS may prove to be a useful bedside tool on the neonatal unit, working alongside current clinical tools in the monitoring of newborn infants (preterm and term) and inform clinical management. We recommend further studies including randomised controlled trials looking at specific measurements and cut-offs for abdominal NIRS for use in further clinical practice.

Portal vein clamping alone confers protection against hepatic ischemia-reperfusion injury via preserving hepatocyte function in cirrhotic rats

BACKGROUND

Chronic liver diseases always increase the risk of liver failure after hepatectomy. We aimed to explore the protective effect of portal vein clamping without hepatic artery blood control (PVC) on a cirrhotic rat liver that underwent ischemia and reperfusion.

METHODS

Carbon tetrachloride-induced cirrhotic rats were randomly assigned to four groups as follows: cirrhotic control, PVC, portal triad clamping (PTC), and intermittent portal triad clamping (IC). After 45 min of portal vascular clamping, hepatic injury and liver function were investigated by assessing the 7-d survival rate, liver blood loss, serum alanine aminotransferase, liver tissue malondialdehyde, liver tissue adenosine triphosphate, indocyanine green retention rate, and morphology changes of the rat liver.

RESULTS

The 7-d survival rates in the PVC and IC groups were much higher than in the PTC group. The PVC group had more liver blood loss during the hepatectomy than the PTC group, but had much less than the cirrhotic control group (P < 0.01). In addition, there were no differences between the IC group and PVC group. The PVC rats had a significantly higher adenosine triphosphate level in the liver tissue and a markedly lower indocyanine green retention rate than the PTC and IC rats (P < 0.05). At 1, 6, and 24 h after reperfusion, the alanine aminotransferase and malondialdehyde levels in the PTC group were much higher than those in the PVC and IC groups (P < 0.05). Based on the histopathologic analysis, hepatic injury in the PVC and IC groups were similar but less prominent than in the PTC group.

CONCLUSIONS

Although both PVC and IC can confer protection against hepatic ischemic-reperfusion injury in cirrhotic rats, the PVC method is more efficient in preserving the energy and function of hepatocytes than the IC method, suggesting better prognosis after hepatectomy.

Abdominal near-infrared spectroscopy measurements are lower in preterm infants at risk for necrotizing enterocolitis

OBJECTIVE

Near-infrared spectroscopy is a noninvasive method of measuring local tissue oxygenation (StO2). Abdominal StO2 measurements in preterm piglets are directly correlated with changes in intestinal blood flow and markedly reduced by necrotizing enterocolitis. The objectives of this study were to use near-infrared spectroscopy to establish normal values for abdominal StO2 in preterm infants and test whether these values are reduced in infants who develop necrotizing enterocolitis.

DESIGN

We conducted a 2-year prospective cohort study where we prospectively measured abdominal StO2 in preterm infants, to establish reference values for preterm infants, and compared the near-infrared spectroscopy values with preterm infants in the cohort that developed necrotizing enterocolitis.

SETTING

Two neonatal ICUs: one at Texas Children's Hospital and the other at Ben Taub General Hospital in Houston, TX.

PATIENTS

We enrolled 100 preterm infants (< 32 weeks' gestation and < 1,500 g birth weight) between January 2007 and November 2008.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Eight neonates with incomplete data were excluded. Mean abdominal StO2 in normal preterm infants (n = 78) during the first week of life was significantly higher than in those who later developed necrotizing enterocolitis (n = 14) (77.3% ± 14.4% vs 70.7% ± 19.1%, respectively, p = 0.002). An StO2 less than or equal to 56% identified preterm infants progressing to necrotizing enterocolitis with 86% sensitivity, 64% specificity, 96% negative predictive value, and 30% positive predictive value. Using logistic regression, StO2 less than or equal to 56% was independently associated with a significantly increased risk of necrotizing enterocolitis (odds ratio, 14.1; p = 0.01). Furthermore, infants with necrotizing enterocolitis demonstrated significantly more variation in StO2 both during and after feeding in the first 2 weeks of life.

CONCLUSIONS

This study establishes normal values for abdominal StO2 in preterm infants and demonstrates decreased values and increased variability in those with necrotizing enterocolitis. Abdominal near-infrared spectroscopy monitoring of preterm infants may be a useful tool for early diagnosis and guiding treatment of necrotizing enterocolitis.

Quantification of mucosa oxygenation using three discrete spectral bands of visible light

Quantification of the mucosa oxygenation levels during Endoscopic imaging provides useful physiological/diagnostic information. In this work a method for non-contact quantification of the oxygen saturation index during Endoscopic imaging using three discrete spectral-band in the blue, the green, and the red parts of the spectrum (RGB bands) has been investigated. The oxygen saturation index (TOI_rgb) was calculated from the three discrete RGB spectral bands using diffusion approximation modeling and least-square analysis. A parametric study performed to identify the optimum band width for each of the three spectral bands. The quantification algorithm was applied to in vivo images of the endobronchial mucosa to calculate (TOI_rgb) from selected areas within the image view. The results were compared to that obtained from the full visible spectral (470-700 nm, 10 nm) measurements. The analysis showed that a band width of at least 20 nm in the blue and the green is required to obtain best results. The results showed that the method provides accurate estimation of the oxygenation levels with about 90% accuracy compared to that obtained using the full spectra. The results suggest the potential of quantifying the oxygen saturation levels from the three narrow RGB spectral bands/images.

Detection and evaluation of initial cartilage pathology in man: A comparison between MRT, arthroscopy and near-infrared spectroscopy (NIR) in their relation to initial knee pain

BACKGROUND AND AIMS

MRI and arthroscopy are important methods in the evaluation of cartilage pathology. But frequently initial changes of cartilage in combination with chronic knee pain cannot be detected by employing these two methods. Better diagnostic tools for the detection of the early stages of osteoarthritis (OA) are required. The objective of this study was to show that near-infrared spectroscopy (NIRS) can be incorporated into routine arthroscopy to improve detection and assessment of the initial cartilage pathology. Furthermore correlations between findings in MRI, arthroscopy and NIRS in patients with initial symptoms of OA have studied.

METHODS

Patients (n=21, 12 women, 9 men, age: 15-59 years, mean 34.19 years) with knee pain lasting for at least half a year without any trauma of the knee in their history were interviewed (body weight, smoking behaviour) and clinically evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Also serum parameters (cholesterol, lipids) were analysed, conventional X-rays in three directions (evaluated according to Kellgren and Lawrence) and MRI (evaluation of cartilage damage according to the ICRS-score) were performed preoperatively in all patients. During subsequent arthroscopy cartilage damage was evaluated according to the ICRS-score. In addition the spectral reflection of cartilage was investigated in all knees using a special micro-glass-fiber probe in the near-infrared light region (spectral range between 1150 and 1475nm). To characterize relations between the investigated parameters the Spearman's rank correlation coefficient was used. Inter-observer variance was calculated employing the Cohens-Kappa-test.

RESULTS

MRI demonstrated a strong inter-observer variance with no significant correlations to other parameters. The same was observed for arthroscopic findings. Only NIRS showed significant correlations with three out of five KOOS subscores. Within the general parameters only smoking behaviour showed a significant correlation with two of the KOOS-scores. NIRS therefore seemed to be a sensitive diagnostic tool in detection of initial pathology in human cartilage. The additional necessary time for the spectroscopic investigation as part of the routine arthroscopy ranged between 3 and 7min (mean: 4min 18s).

CONCLUSION

Particularly for early-stage cartilage lesions (ICRS 0/I) MRI and arthroscopy have rather low predictive value. The inter-observer variance is very high (Cohens-Kappa<0.4). Correlations found between NIRS and KOOS suggest that NIRS potentially can be used for detection of initial cartilage pathology and may be helpful in the evaluation of the benefit of different medical or surgical interventions at early-stage of articular cartilage damage.

Use of the liver tissue oxygenation index as a noninvasive parameter of intestinal ischemia in rabbits

OBJECTIVE

The tissue oxygenation index (TOI), measured by spatially resolved spectroscopy (SRS), reflects the ratio between oxygenated and deoxygenated tissue hemoglobin. We investigated whether liver TOI is a noninvasive parameter for early detection of intestinal ischemia.

METHODS

In seven adult New Zealand rabbits the superior mesenteric artery (SMA) and vein were exposed by laparotomy. The SRS probe was attached at the skin above the liver to calculate the TOI. The bowel (SbO(2)) and peripheral (SpO(2)) oxygen saturation were continuously measured. The SMA was occluded, creating small bowel ischemia for 90 minutes. Then reperfusion was started for 1 hour. The median TOI and interquartile range (IQR) of the TOI were calculated. A paired Wilcoxon test was used to evaluate changes in the liver TOI and SpO(2) during ischemia and reperfusion.

RESULTS

The median TOI was 54.3% (IQR 8) at the start of ischemia, 54.9% (IQR 9) after 30 minutes, 51% (IQR 11) after 60 minutes, and 50.3% (IQR 10) after 90 minutes. The median TOI values were 46.3% (IQR 5) after 30 minutes of reperfusion and 41.2% (IQR 5) after 60 minutes. The decrease in TOI became significant (p < 0.05) after 90 minutes of ischemia. The SpO(2) was stable during the experiment.

DISCUSSION

A significant decrease in liver TOI was seen after 90 minutes of occlusion of the SMA and is likely to be the consequence of bowel ischemia. The further decrease after reperfusion might reflect reperfusion injury. Liver TOI may be a new tool for noninvasive early detection of intestinal ischemia and reperfusion. Further study is needed to confirm these findings.

Maturational pharmacokinetics of single intravenous bolus of propofol

BACKGROUND

Our aim was to document propofol pharmacokinetics in preterm and term neonates following a single intravenous bolus and compare these estimates with pharmacokinetics findings in toddlers and young children.

METHODS

Newly collected observations following intravenous bolus administration of propofol in preterm and term neonates (n = 9) were compared with earlier reported pharmacokinetic estimates in toddlers and young children. Data are reported by median and range. Mann-Whitney U-test or correlation was used to analyze differences in pharmacokinetic findings between neonates, toddlers and young children.

RESULTS

Concentration-time profiles obtained were interpreted by two-stage analysis as a three compartment open model in nine neonates with a median weight of 2.51 (range 0.91-3.8) kg and a median postmenstrual age (PMA) of 36 (range 27-43) weeks. Median clearance (CL) was 13.6 (range 3.7-78.2) ml.min(-1).kg(-1) and median apparent volume of distribution at steady state (V(ss)) was 3.7 (1.33-7.96) l.kg(-1). Following allometric scaling and standardization to 70 kg, median CL was 442 (range 97-2184) ml.min(-1).70 kg(-1). Compared with earlier reported observations in toddlers and children, median clearance (kg.min(-1)) was significantly lower in neonates (P < 0.01) and these differences remained significant after allometric scaling (70 kg.min(-1)) while V(ss) (l.kg(-1)) was significantly lower in neonates (P < 0.01).

CONCLUSIONS

Propofol disposition is significantly different in neonates compared with toddlers and young children, reflecting both ontogeny and differences in body composition. Based on the reduced clearance of propofol, a longer recovery time is more likely to occur in neonates.

Evaluation of cartilage defects with near-infrared spectroscopy (NIR): an ex vivo study

Damaged cartilage undergoes complex changes in composition, histological structure, and mechanical properties. Near-infrared-spectroscopy (NIR spectroscopy) is an important method to measure changes in composition of complex composites. The present study was aimed at evaluating NIR spectroscopy as a means to quantitate tissue alterations in low grade cartilage defects. Fresh medial femoral condyles from female sheep were collected. Cartilage defects were graded according to the International Cartilage Repair Society (ICRS). Specimens were examined by a NIR spectroscopy device (spectral range of 1100-1700 nm). Absorption spectra were calculated from the reference and measurement spectra. As indicator for cartilage composition the ratio (absorption ratio, AR) of the two main absorption bands in this region was calculated. Mechanical stiffness was measured as Shore A. Water-, glycosaminoglycan-, and collagen content and histological grade (Mankin score) were determined. The NIR absorption in ICRS grade 1 defects (AR=2.1+/-0.1) was significantly higher than in intact cartilage (AR=1.5+/-0.1). ICRS grade 2 specimens tended to a higher NIR absorption. NIR absorption correlated significantly with Mankin score (R=0.896), water content (R=0.845), and mechanical stiffness (R=0.877). Initial cartilage degeneration correlates with changes in NIR absorption, indicating NIR spectroscopy to reflect complex structural changes in degenerated cartilage. The data suggest that NIR spectroscopy could be useful for in situ detection of early cartilage defects.

Correlation of transcutaneous hepatic near-infrared spectroscopy readings with liver surface readings and perfusion parameters in a piglet endotoxemic shock model

PURPOSE

To determine whether transcutaneous liver near-infrared spectrophotometry (NIRS) measurements correlate with NIRS measurements taken directly from the liver surface, and invasive blood flow measurements.

PROCEDURE

Laparotomy was performed in 12 Yorkshire piglets, and ultrasound blood flow probes were placed on the hepatic artery and portal vein. Intravascular catheters were inserted into the hepatic and portal veins for intermittent blood sampling, and a pulmonary artery catheter was inserted via the jugular vein for cardiac output measurements. NIRS optodes were placed on skin overlying the liver and directly across the right hepatic lobe. Endotoxemic shock was induced by continuous infusion of Escherichia coli lipopolysaccharide O55:B5. Pearson's correlations were calculated between the NIRS readings and the perfusion parameters.

FINDINGS

After endotoxemic shock induction, liver blood flow, and oxygen delivery decreased significantly. There were statistically significant correlations between the transcutaneous and liver-surface NIRS readings for oxyhemoglobin, deoxyhemoglobin, and cytochrome c oxidase concentrations. There were similar significant correlations of the transcutaneous oxyhemoglobin with both the mixed venous and hepatic vein saturation, and mixed venous and hepatic vein lactate.

CONCLUSIONS

Transcutaneous NIRS readings of the liver, in an endotoxemic shock model, correlate with NIRS readings taking directly from the liver surface, as well as with global and specific organ-perfusion parameters.