Regional Tissue Oxygenation Research Articles

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support.

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO2) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO2. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO2 from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO2 from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO2 increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO2 from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

Assessment of Mesenteric Tissue Saturation, Oxygen Saturation, and Heart Rate Pre- and Post-Blood Transfusion in Very Low-Birth-Weight Infants Using Abdominal Site Near-Infrared Spectroscopy.

Preterm infants often receive blood transfusions during hospitalization. Although transfusions are intended to enhance oxygen delivery, previous studies found decreases in tissue and mesenteric oxygen saturation during and after blood transfusions without changes in vital signs and hemoglobin oxygen saturation. To study the effect of blood transfusions on regional mesenteric tissue oxygen saturation (rSO2), hemoglobin saturation of oxygen (SpO2), and heart rate (HR) in premature infants. A prospective, observational, nonrandomized study using a repeated-measures design was done to evaluate changes in physiologic variables (HR, SpO2, rSO2) before, during, and after a blood transfusion in premature infants. A convenience sample of 30 infants with a mean gestational age of 25.5 (2.1) weeks was recruited. Repeated-measures analysis of variance found no significant differences in HR (P = .06) and SpO2 (P = .55) over time. However, significant differences occurred in rSO2 over the 3 time periods (P < .001). The rSO2 increased during the transfusion from 40.3% to 41.5%, but decreased to 34.9% in the posttransfusion period. Pairwise comparisons revealed statistically significant mean rSO2 differences between pretransfusion and posttransfusion (P < .001), and during transfusion to posttransfusion (P < .001) periods. This study supports previous findings of perfusion changes during blood transfusions in preterm infants. Measuring mesenteric tissue oxygenation during blood transfusion in very low-birth-weight infants can potentially add another physiologic parameter to guide further clinical assessment and interventions during transfusions.

NIRS-based cerebrovascular regulation assessment: exercise and cerebrovascular reactivity.

Alterations to cerebral blood flow (CBF) have been implicated in diverse neurological conditions. Near-infrared spectroscopy (NIRS)-measured regional cerebral tissue oxygen saturation ([Formula: see text]) provides an estimate of oxygenation of interrogated cerebral volume useful in identifying variations in oxygen supply to cerebral tissue and in monitoring cerebrovascular function. [Formula: see text]-inhalation-based hypercapnic breathing challenges were used to simulate CBF dysregulation, utilizing NIRS to monitor the CBF autoregulatory response. A breathing circuit was designed to administer [Formula: see text]-compressed air mixtures and assess CBF regulatory responses to hypercapnia in 26 healthy young adults. One to three hypercapnic challenges of 5 or 10min duration were delivered to each subject while continuously monitoring [Formula: see text], partial pressure of end tidal [Formula: see text] ([Formula: see text]), and vital signs. Change in [Formula: see text] ([Formula: see text]) during [Formula: see text] inhalation positively correlated to [Formula: see text] ([Formula: see text]). Grouping subjects into three exercise factor levels (h/week), (1)0, (2)[Formula: see text] and [Formula: see text], and (3)[Formula: see text] showed significantly greater [Formula: see text] responses to [Formula: see text] challenges for level 3 subjects but similar [Formula: see text] responses for the three groups. Exercising greater than 10h/week may produce a higher resting cerebrovascular reactivity (CVR) to [Formula: see text] inhalation. Establishing baseline values of [Formula: see text] and CVR to [Formula: see text] may aid in early detection of CBF changes.

Response time of indirectly accessed gas exchange depends on measurement method.

Noninvasive techniques are routinely used for assessment of tissue effects of lung ventilation. However, comprehensive studies of the response time of the methods are scarce. The aim of this study was to compare the response time of noninvasive methods for monitoring of gas exchange to sudden changes in the composition of the inspired gas. A prospective experimental study with 16 healthy volunteers was conducted. A ventilation circuit was designed that enabled a fast change in the composition of the inspiratory gas mixture while allowing spontaneous breathing. The volunteers inhaled a hypoxic mixture, then a hypercapnic mixture, a hyperoxic mixture and finally a 0.3% CO mixture. The parameters with the fastest response to the sudden change of O2 in inhaled gas were peripheral capillary oxygen saturation (SpO2) and regional tissue oxygenation (rSO2). Transcutaneous oxygen partial pressure (tcpO2) had almost the same time of reaction, but its time of relaxation was 2-3 times longer. End-tidal carbon dioxide (EtCO2) response time to change of CO2 concentration in inhaled gas was less than half in comparison with transcutaneous carbon dioxide partial pressure (tcpCO2). All the examined parameters and devices reacted adequately to changes in gas concentration in the inspiratory gas mixture.

The Impact of Integrated Evaluation of Hemodynamics on Management of Preterm Infants with Late-Onset Compromised Systemic Circulation.

Objectives To study the impact of integrated evaluation of hemodynamics (IEH), using targeted neonatal echocardiography (TNE), cerebral regional tissue oxygenation (crRTO), and fractional oxygen extraction (FOE), using near-infrared spectroscopy (NIRS) on the management of infants with late-onset compromised systemic circulation (LCSC), and evaluation of the hemodynamic characteristics. Study Design Retrospective cohort study comparing infants with LCSC who underwent IEH (April 2014 to May 2016) with an earlier EPOCH who did not undergo IEH (January 2012 to March 2014). The primary outcome was the time to recovery. Results Total 43 infants were included; 18 infants underwent IEH with a median (IQR) 2 (1-3) assessments per infant. The time to recovery was shorter in IEH group with a median (IQR) 28 hours (15-62) compared with non-IEH group 96 hours (30-160). Autoregulation was compromised in 50%, and systemic vascular resistance (SVR) was low in 67%. Conclusion IEH was associated with shorter time to recovery in infants with LCSC.

Use of near-infrared spectroscopy (NIRS) in cerebral tissue oxygenation monitoring in neonates

Near-infrared spectroscopy (NIRS) is a technology capable of non-invasive, continuous measuring of regional tissue oxygen saturation (StO2). StO2 represents a state of hemodynamic stability, which is influenced by many factors. Extensive research has been done in the field of measuring StO2 of various organs. The current clinical availability of several NIRS-based devices reflects an important development in prevention, detection and correction of discrepancy in oxygen delivery to the brain and vital organs. Managing cerebral ischemia remains a significant issue in the neonatal intensive care units (NICU). Cerebral tissue oxygenation (cStO2) and cerebral fractional tissue extraction (cFTOE) are reported in a large number of clinical studies. This review provides a summary of the concept of function, current variability of NIRS-based devices used in neonatology, clinical applications in continuous cStO2 monitoring, limitations, disadvantages, and the potential of current technology.

Near-infrared spectroscopy as a predictor of clinical deterioration: a case report of two infants with duct-dependent congenital heart disease

BackgroundSome infants with congenital heart disease are at risk of in-hospital cardiac arrest. To better foresee cardiac arrest in infants with congenital heart disease, it might be useful to continuously assess end-organ perfusion. Near-infrared spectroscopy is a non-invasive method to continuously assess multisite regional tissue oxygen saturation.Case presentationWe report on two infants with duct-dependent congenital heart disease who demonstrated a gradual change in cerebral and/or renal tissue oxygen saturation before cardiopulmonary resuscitation was required. In both cases, other clinical parameters such as heart rate, arterial oxygen saturation and blood pressure did not indicate that deterioration was imminent.ConclusionsThese two cases demonstrate that near-infrared spectroscopy might contribute to detecting a deteriorating clinical condition and might therefore be helpful in averting cardiopulmonary collapse and need for resuscitation in infants with congenital heart disease.

Effect of blood pressure elevation on cerebral oxygen desaturation in the beach chair position

ObjectiveThe beach chair position (BCP) during shoulder arthroscopy is a known risk factor for cerebral ischemia. We retrospectively investigated whether maintaining the arterial blood pressure (ABP) prevented the decrease in the regional cerebral tissue oxygen saturation (rSO2). MethodsWe analyzed 20 consecutive patients who underwent elective shoulder surgery in the BCP under general anesthesia. The bilateral rSO2 was monitored continuously throughout the procedure with the help of near-infrared spectroscopy (INVOS 5100 Cerebral Oximeter, Somanetics Corporation, Troy, MI, USA). Anesthesiologists maintained patient blood pressure while they were in the BCP, which was measured using an ABP transducer placed at the level of the external auditory meatus. We compared rSO2 measured in the supine position and in the BCP. ResultsMeasurement of cortex level mean ABP (mABP) values in the BCP were >50 mmHg and over 60% higher than those noted for the supine position in most patients. Although all bilateral rSO2 values in the BCP were significantly lower than those in the supine position, the reductions was <20%. Further, 35% (7 of 20) patients that were part of the study experienced cerebral desaturation events at any given point during the procedure. None of the patients experienced clinical postoperative neurological complications. ConclusionsAlthough cortex level mABP in the BCP was >50 mmHg, a decrease was recorded in the rSO2 values. This rSO2 decrease was proportional to the reduction in the cortex level mABP induced by a postural change to the BCP. Therefore, despite appropriate blood pressure management, shoulder surgery in the BCP might involve certain risks for patients with cerebrovascular diseases.

Tissue oxygen saturation levels from fetus to neonate.

Oxygen saturation during the term of delivery to the first cry, when fetal circulation dynamically changes, has not yet been examined. The aim of this study was therefore to determine whether the continuous measurement of regional tissue oxygen saturation (rSO2 ) from crowning until 5 min after delivery is possible using fetal tissue oximetry with a sensor attached to the examiner's finger. Oxygen saturation levels in fetal cranial tissue between the second stage of delivery to crowning and up to 5 min after delivery were measured using fetal tissue oximetry with a sensor attached to the examiner's finger. Thirty-five deliveries were examined, and oxygen saturation was measured in seven infants from delivery of the head until 5 min after birth. Umbilical cord blood gas was measured in all cases. This clinical test was performed under the permission of the Ethics Committee of Hamamatsu University School of Medicine. Average tissue oxygen saturation in the second stage of delivery and at 5 min after delivery were 50.3 ± 16.3% and 56.8 ± 8.46%, respectively. In cases of continuous measurement, average rSO2 for crowning, immediately after delivery, and the first cry was 32.7 ± 9.5%, 30.0 ± 6.6%, and 31.6 ± 5.5%, respectively. We herein successfully measured oxygen saturation levels in fetal cranial tissue during crowning, delivery of the head, the first cry, and 5 min after delivery using fetal tissue oximetry with a sensor attached to the examiner's finger.

Quantifying cerebral hypoxia by near-infrared spectroscopy tissue oximetry: the role of arterial-to-venous blood volume ratio.

Tissue oxygenation estimated by near-infrared spectroscopy (NIRS) is a volume-weighted mean of the arterial and venous hemoglobin oxygenation. In vivo validation assumes a fixed arterial-to-venous volume-ratio (AV-ratio). Regulatory cerebro-vascular mechanisms may change the AV-ratio. We used hypotension to investigate the influence of blood volume distribution on cerebral NIRS in a newborn piglet model. Hypotension was induced gradually by inflating a balloon-catheter in the inferior vena cava and the regional tissue oxygenation from NIRS ( rStO 2 , NIRS ) was then compared to a reference ( rStO 2 , COX ) calculated from superior sagittal sinus and aortic blood sample co-oximetry with a fixed AV-ratio. Apparent changes in the AV-ratio and cerebral blood volume (CBV) were also calculated. The mean arterial blood pressure (MABP) range was 14 to 82 mmHg. PaCO 2 and SaO 2 were stable during measurements. rStO 2 , NIRS mirrored only 25% (95% Cl: 21% to 28%, p < 0.001 ) of changes in rStO 2 , COX . Calculated AV-ratio increased with decreasing MABP (slope: ? 0.007 · mmHg ? 1

Does metabolic alkalosis influence cerebral oxygenation in infantile hypertrophic pyloric stenosis?

BackgroundThis pilot study focuses on regional tissue oxygenation (rSO2) in patients with infantile hypertrophic pyloric stenosis in a perioperative setting. To investigate the influence of enhanced metabolic alkalosis (MA) on cerebral (c-rSO2) and renal (r-rSO2) tissue oxygenation, two-site near-infrared spectroscopy (NIRS) technology was applied. Materials and methodsPerioperative c-rSO2, r-rSO2, capillary blood gases, and electrolytes from 12 infants were retrospectively compared before and after correction of MA at admission (T1), before surgery (T2), and after surgery (T3). ResultsCorrection of MA was associated with an alteration of cerebral oxygenation without affecting renal oxygenation. When compared to T1, 5-min mean (± standard deviation) c-rSO2 increased after correction of MA at T2 (72.74 ± 4.60% versus 77.89 ± 5.84%; P = 0.058), reaching significance at T3 (80.79 ± 5.29%; P = 0.003). Furthermore, relative 30-min c-rSO2 values at first 3 h of metabolic compensation were significantly lowered compared with postsurgical states at 16 and 24 h. Cerebral oxygenation was positively correlated with levels of sodium (r = 0.37; P = 0.03) and inversely correlated with levels of bicarbonate (r = −0.34; P = 0.05) and base excess (r = −0.36; P = 0.04). Analysis of preoperative and postoperative cerebral and renal hypoxic burden yielded no differences. However, a negative correlation (r = −0.40; P = 0.03) regarding hematocrite and mean r-rSO2, indirectly indicative of an increased renal blood flow under hemodilution, was obtained. ConclusionsNIRS seems suitable for the detection of a transiently impaired cerebral oxygenation under state of pronounced MA in infants with infantile hypertrophic pyloric stenosis. Correction of MA led to normalization of c-rSO2. NIRS technology constitutes a promising tool for optimizing perioperative management, especially in the context of a possible diminished neurodevelopmental outcome after pyloromyotomy.

Severe hypercapnia causes reversible depression of aEEG background activity in neonates: an observational study

IntroductionElevated carbon dioxide (CO2) blood levels have a depressant effect on the central nervous system and can lead to coma in adults. Less is known about the effect of CO2...

The impact of integrated evaluation of hemodynamics using targeted neonatal echocardiography with indices of tissue oxygenation: a new approach.

To study the impact of integrated evaluation of hemodynamics (IEH) using targeted neonatal echocardiography, together with regional tissue oxygenation, fractional oxygen extraction using near-infrared spectroscopy on the management of infants with compromised hemodynamics. Retrospective cohort comparison of two groups of infants with compromised hemodynamics. EPOCH 1: did not undergo IEH (January 2012 to March 2014); EPOCH 2: underwent IEH (April 2014 to December 2015). The primary outcome was the time to recovery. In all, 340 infants were included; 158 underwent IEH with a median (IQR) of 2 (1 to 3) evaluations per infant. Reasons for assessment included PDA (60%), compromised systemic circulation (14%) and clinically suspected pulmonary hypertension (22%). The time to recovery was shorter in IEH group in patients with compromised systemic circulation median (IQR), 32 h (24 to 63) compared with none IEH group 71 h (36 to 96), pulmonary hypertension 63 h (14.2 to 102) in IEH group compared with 68 h (24 to 240) in none IEH group, there were fewer PDA-related complications in preterm infants with PDA in IEH group. IEH was associated with shorter time to clinical recovery in infants with compromised hemodynamics.

Brain Multimodality Monitoring: A New Tool in Neurocritical Care of Comatose Patients.

Neurocritical care patients are at risk of developing secondary brain injury from inflammation, ischemia, and edema that follows the primary insult. Recognizing clinical deterioration due to secondary injury is frequently challenging in comatose patients. Multimodality monitoring (MMM) encompasses various tools to monitor cerebral metabolism, perfusion, and oxygenation aimed at detecting these changes to help modify therapies before irreversible injury sets in. These tools include intracranial pressure (ICP) monitors, transcranial Doppler (TCD), Hemedex™ (thermal diffusion probe used to measure regional cerebral blood flow), microdialysis catheter (used to measure cerebral metabolism), Licox™ (probe used to measure regional brain tissue oxygen tension), and continuous electroencephalography. Although further research is needed to demonstrate their impact on improving clinical outcomes, their contribution to illuminate the black box of the brain in comatose patients is indisputable. In this review, we further elaborate on commonly used MMM parameters, tools used to measure them, and the indications for monitoring per current consensus guidelines.

Regional tissue oximetry reflects changes in arterial flow in porcine chronic heart failure treated with venoarterial extracorporeal membrane oxygenation.

Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in treatment of decompensated heart failure. Our aim was to investigate its effects on regional perfusion and tissue oxygenation with respect to extracorporeal blood flow (EBF). In five swine, decompensated low-output chronic heart failure was induced by long-term rapid ventricular pacing. Subsequently, VA ECMO was introduced and left ventricular (LV) volume, aortic blood pressure, regional arterial flow and tissue oxygenation were continuously recorded at different levels of EBF. With increasing EBF from minimal to 5 l/min, mean arterial pressure increased from 47+/-22 to 84+/-12 mm Hg (P<0.001) and arterial blood flow increased in carotid artery from 211+/-72 to 479+/-58 ml/min (P<0.01) and in subclavian artery from 103+/-49 to 296+/-54 ml/min (P<0.001). Corresponding brain and brachial tissue oxygenation increased promptly from 57+/-6 to 74+/-3 % and from 37+/-6 to 77+/-6 %, respectively (both P<0.01). Presented results confirm that VA ECMO is a capable form of heart support. Regional arterial flow and tissue oxygenation suggest that partial circulatory support may be sufficient to supply brain and peripheral tissue by oxygen.

Chronic Transfusion Therapy in Sickle Cell Disease - Effect on Macrovascular Function, Microvascular Function, and Tissue Oxygenation Decreases the Potential for Ischemia

BACKGROUND: Sickle cell disease is an inheritable hemoglobinopathy that causes increased red blood cell (RBC) stiffness due to hemoglobin polymerization at low oxygen tension. This leads to microcirculatory occlusion as well as chronic hemolysis and chronic inflammation, resulting in a diffuse vasculopathy of bothmacrovascular and microvascular beds. Chronic transfusion therapy is used for both primary and secondary prevention of ischemic stroke, amacrovascular complication; however, there is limited knowledge of its effect on microvascular function.OBJECTIVE: To determine the effects of chronic transfusion therapy on microvascular function and tissue oxygenation.DESIGN/METHODS: We utilized a forearm, arterial and venous occlusion model, commonly used for flow-mediated dilation of the brachial artery, to simultaneously assess post occlusive reactive hyperemia (PORH) in the microcirculation and post hyperemic change in tissue oxygenation. PORH was measured using laser Doppler flowmetry placed over the third finger, proximal to the nailbed. Regional tissue oxygenation (rSO2) was measured using near infrared spectroscopy (NIRS) placed on the dorsal surface of the hand. FMD was measured using a linear ultrasound probe. Transfused patients were measured before and after a single transfusion. Kruskal-Wallis was used to test between group differences. Multivariate linear regression was used to model predictors of vascular function.RESULTS: We enrolled 18 control (CTL) patients, 75 non-transfused (NTR) SCD patients, and 26 chronically transfused (TR) SCD patients. Consistent with our previously published data, FMD was improved but not normalized by chronic transfusion and it was predicted by ln[plasma hgb], age and sex. PORH was reduced in both SCD patient groups when compared to the control group while resting flow by laser Doppler was elevated in both SCD groups (figure 1). PORH was also inversely related to resting flow, suggesting that basal conditions in the microcirculation are significant predictors of their response to forearm occlusion. Percent change in rSO2 was not different between the three groups. Lower baseline rSO2 was inversely associated with percent rSO2 increase following hyperemia; and, the baseline rSO2 was significantly decreased in the non-transfused SCD patients but normalized in the transfused SCD patients (Figure 2). Resting hypoxia was best predicted by RBC deformability in the non-transfused patients, even after correction for hemoglobin level, whereas resting hemoglobin levels predicted hypoxia in the transfused and healthy patients.DISCUSSION: With the goal to better understand the mechanism by which transfusion therapy decreases the risk of stroke, we tested the response to arterial and venous occlusion, simultaneously, at three different functional levels of the vascular system: 1.Conduit artery, 2.Pre-capillary arteriolar and capillary, 3.Tissue oxygen exchange. We confirm our previous findings that conduit vessel dysfunction is highly dependent on free hemoglobin, which is consistent with the hemolysis paradigm as a mechanism for sickle cell vasculopathy. This study extends our model to the microcirculation. Resting microcirculatory flow is increased in both transfused and non-transfused SCD patients; and while the resting rSO2 is near normal in the transfused SCD patients it is significantly lower in the non-transfused subjects. This creates the potential for severe hypoxia in the setting of a limited ability to augment flow through the microcirculation during periods of high demand, as in PORH. If there is also decreased conduit vessel reactivity upstream this creates the scenario over which large areas of tissue may rapidly become ischemic. This is a novel system, with simultaneous measurements in multiple vascular beds, allowing us to evaluate supply-demand matching.CONCLUSIONS: Chronic transfusion therapy improves both brachial artery endothelial function and regional tissue oxygenation but it does not significantly improve microcirculatory function, which may be near its maximal flow at rest. Hemoglobin determines resting tissue saturation in healthy and transfused SCD patients, but high shear RBC deformability determines rSO2 in non-transfused SCD patients. [Display omitted] [Display omitted] DisclosuresWood:World Care Clinical: Consultancy; Vifor: Consultancy; AMAG: Consultancy; Ionis Pharmaceuticals: Consultancy; Biomed Informatics: Consultancy; World Care Clinical: Consultancy; Ionis Pharmaceuticals: Consultancy; Apopharma: Consultancy; Vifor: Consultancy; Apopharma: Consultancy; AMAG: Consultancy; Biomed Informatics: Consultancy; Celgene: Consultancy; Celgene: Consultancy.

Measurement of brain tissue oxygen saturation in term infants using a new portable near-infrared spectroscopy device.

A small oximeter with the probe attached to the examiner's finger has been developed. The aim of this study was to determine the feasibility of measuring regional oxygenation of the brain tissue using this device in healthy term infants immediately after birth. We conducted a prospective observational study. Using a new near-infrared spectroscopy (NIRS) device, we measured changes in regional cerebral tissue oxygen saturation (crSO2 ) during the first 10 min of life in 32 healthy term infants after delivery. Arterial oxygen saturation (SpO2 ) was also simultaneously measured. Median crSO2 increased from 43% (1 min after birth) to 49% (4 min after birth); thereafter, no significant changes were observed. Median SpO2 increased constantly from min 3 to min 7, from 77% to 92% and did not change significantly after 8 min. A stable oxygen saturation signal was measured in 59% of infants (crSO2 ) and in 0% of infants (SpO2 ) at 1 min, and in 97% (crSO2 ) and in 78% (SpO2 ) at 3 min. During the transition after birth, crSO2 can be more easily and quickly measured in healthy newborn infants using the novel NIRS device than SpO2 .

Cerebral oxygen saturation during the first 72 h after birth in infants diagnosed prenatally with congenital heart disease

BackgroundEvidence suggests that hypoxic-ischemic brain injury in infants with congenital heart disease already occurs during early life. The aim of our study was, therefore, to assess the course of regional cerebral oxygen saturation (rcSO2) and fractional tissue oxygen extraction (FTOE) during the first 72h after birth in infants with prenatally diagnosed duct-dependent congenital heart disease. In addition, we identified clinical parameters that were associated with rcSO2. Materials and methodsWe included 56 infants with duct-dependent congenital heart disease. We measured arterial oxygen saturation (SpO2) and rcSO2 during the first 72h after birth. Simultaneously, we calculated FTOE. ResultsWe observed median rcSO2 values of approximately 60%, a decreasing FTOE from 0.34 on day 1 to 0.28 on day 3 and stable preductal SpO2 values around 90%. Several clinical variables were associated with rcSO2. In a multiple linear regression model only type of CHD and preductal SpO2 were significant predictors of rcSO2 during the first three days after birth. Infants with a duct-dependent pulmonary circulation had up to 12% lower rcSO2 values than infants with a duct-dependent systemic circulation. ConclusionWe demonstrated that, during the first three days after birth, cerebral oxygen saturation is low in infants with duct-dependent congenital heart disease. Furthermore, this study provides preoperative reference values of rcSO2 and FTOE in infants with duct-dependent CHD.

Assessment of the adequacy of oxygen delivery.

This article reviews the recent literature pertaining to assessment of the adequacy of oxygen delivery in critically ill patients with circulatory shock. The assessment of the adequacy of oxygen delivery has traditionally involved measurement of lactate, central (or mixed) venous oxygen saturation (ScvO2), and global hemodynamic markers such as mean arterial pressure and cardiac index. The search for noninvasive, reliable, and sensitive methods to detect derangements in oxygen delivery and utilization continues. Recent studies focus on near-infrared spectroscopy (NIRS) to assess regional tissue oxygenation, as well as bedside ultrasound techniques to assess the macrovascular hemodynamic factors in oxygen delivery. In this article, we review physiologic principles of global oxygen delivery, and discuss the bedside approach to assessing the adequacy of oxygen delivery in critically ill patients. Although there have been technological advances in the assessment of oxygen delivery, we revisit and emphasize the importance of a 'tried and true' method - the physical examination. Also potentially important in the evaluation of oxygen delivery is the utilization of biomarkers (e.g., lactate, ScvO2, NIRS). In complementary fashion, bedside ultrasound for hemodynamic assessment may augment the physical examination and biomarkers, and represents a potentially important adjunct for assessing the adequacy of oxygen delivery.

Foreword

To evaluate the feasibility and repeatability of applying blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in the feet to quantify regional dynamic changes in tissue oxygenation during proximal cuff occlusion and reactive hyperemia.Ten healthy male subjects underwent BOLD and T1-weighted imaging of the feet on two separate occasions, using a 3-T scanner. Dynamic changes in BOLD signal intensity were assessed before and during proximal cuff occlusion of the thigh and during reactive hyperemia, and BOLD time course data were evaluated for the time-to-half ischemic minimum, minimum ischemic value, peak hyperemic value, time-to-peak hyperemia, time-to-half peak hyperemia, and end value. T1-weighted images were used for segmentation of volumes of interest (VOI) in anatomical regions of the foot (heel, toes, dorsal foot, medial and lateral plantar foot). Repeatability of vascular responses was assessed for each foot VOI using semiautomated image registration and quantification of serial BOLD images.The heel VOI demonstrated a significantly higher peak hyperemic response, expressed as percent change from baseline BOLD signal intensity, compared with all other VOIs of the foot (heel, 7.4 ± 1.2%; toes, 5.6 ± 0.8%; dorsal foot, 5.7 ± 1.6%; medial plantar, 5.6 ± 1.7%; lateral plantar, 5.6 ± 1.5% [p < .05]). Additionally, the lateral plantar VOI had a significantly lower terminal signal intensity value (i.e., end value) when compared with all foot VOIs (p < .05). BOLD MRI was repeatable between visits in all foot VOIs, with no significant differences between study visits for any of the evaluated functional indices.BOLD MRI offers a repeatable technique for volumetric assessment of regional foot tissue oxygenation. Future application of BOLD imaging in the feet of patients with peripheral vascular disease may permit serial evaluation of regional tissue oxygenation and allow for improved assessment of therapeutic interventions targeting specific sites of the foot.