Splanchnic tissue oxygenation, but not brain tissue oxygenation, increases after feeds in stable preterm neonates tolerating full bolus orogastric feeding

Neonatal somatic oxygenation and perfusion assessment using near-infrared spectroscopy : Part of the series on near-infrared spectroscopy by the European Society of Paediatric Research Special Interest Group "Near-Infrared Spectroscopy"

In this narrative review, we summarize the current knowledge and applications of somatic near-infrared spectroscopy (NIRS), with a focus on intestinal, renal, limb, and multi-site applications in neonates. Assessing somatic oxygenation at various body locations in neonates may aid in the understanding of underlying pathophysiology of organ injury. Considering cerebral autoregulation may be active to protect the brain during systemic circulatory failure, peripheral somatic oxygenation may potentially provide an early indication of neonatal cardiovascular failure and ultimate hypoxemic injury to vital organs including the brain. Certain intestinal oxygenation patterns appear to be associated with the onset and course of necrotizing enterocolitis, whereas impaired renal oxygenation may indicate the onset of acute kidney injury after various types of hypoxic events. Peripheral muscle oxygenation measured at a limb may be particularly effective in the early prediction of shock in neonates. Using multi-site NIRS may complement current approaches and clinical investigations to alert for neonatal tissue hypoxemia, and potentially even guide management. However, somatic NIRS has its inherent limitations in regard to accuracy. Interpretation of organ-specific values can also be challenging. Last, currently there are limited prospective intervention studies, and clinical benefits need to be examined further, after the clarification of critical threshold-values. IMPACT: The assessment of somatic oxygenation using NIRS may contribute to the prediction of specific diseases in hemodynamically challenged neonates. Furthermore, it may give early warning signs for impending cardiovascular failure, and impaired cerebral circulation and oxygenation. We present a comprehensive overview of the literature on applications of NIRS to various somatic areas, with a focus on its potential clinical applicability, including future research directions. This paper will enable prospective standardized studies, and multicenter collaboration to obtain statistical power, likely to advance the field.

Nutrition of the preterm infant with persistent ductus arteriosus: existing evidence and practical implications

The persistence of a patent ductus arteriosus (PDA) is a common condition in preterm infants with a prevalence inversely proportional to gestational age. PDA is associated with mild-to-severe gastrointestinal complications such as feeding intolerance, gastrointestinal perforation, and necrotizing enterocolitis, which represent a major challenge for the nutritional management in preterm infants. In this context, the Section on Nutrition, Gastroenterology and Metabolism and the Circulation Section of the European Society for Pediatric Research have joined forces to review the current knowledge on nutritional issues related to PDA in preterm infants. The aim of the narrative review is to discuss the clinical implications for nutritional practice. Because there is little literature on postnatal nutrition and PDA in preterm infants, further research with well-designed studies on this topic is urgently needed. Guidelines should also be developed to clearly define the implementation and course of enteral nutrition and the target nutritional intake before, during, and after pharmacologic or surgical treatment of PDA, when indicated. IMPACT: Persistent ductus arteriosus (PDA) is associated with gastrointestinal complications such as feeding intolerance, gastrointestinal perforation, and necrotizing enterocolitis, which pose a major challenge to the nutritional management of preterm infants. In PDA infants, fluid restriction may lead to inadequate nutrient intake, which may negatively affect postnatal growth and long-term health. The presence of PDA does not appear to significantly affect mesenteric blood flow and splanchnic oxygenation after enteral feedings. Initiation or maintenance of enteral nutrition can be recommended in infants with PDA.

The effect of drip versus intermittent feeding on splanchnic oxygenation in preterm infants with intrauterine growth restriction: a prospective randomized trial

The main purpose of this study was to evaluate the impact of drip versus intermittent feeding on splanchnic oxygenation in preterm infants with intrauterine growth restriction. The second objective was to assess the relationship between fetal splanchnic circulation parameters and splanchnic oxygenation during the first week of life. A single-center, prospective, randomized study with 51 fetuses/infants was conducted. Fetal Doppler measurements including umbilical artery, middle cerebral artery, and superior mesenteric artery (SMA) were recorded in IUGR fetuses. After preterm delivery, the infants were randomly assigned to one of two feeding modalities: drip (3-h continuous) or intermittent (bolus in 10 min). Continuous regional splanchnic saturation (rSO₂S) monitoring was carried out during the first week of life, simultaneously with continuous oxygen arterial saturation (SaO₂) monitoring, and the infants' fractional oxygen extractions (FOE) were calculated. These parameters were evaluated as means on a daily basis for the first week of life, as well as pre-prandial and post-prandial measurements on the seventh day. Fetal Doppler flow velocimetry disturbances were present in 72.5% of the study cohort. The drip (26 infants) and intermittent (25 infants) groups were similar in demographic and clinical characteristics, as well as the prevalence of feeding intolerance and necrotizing enterocolitis. During the first week of life, there was no difference in daily mean rSO₂S and FOE values between the drip and intermittent groups, whereas unfed infants had mostly lower rSO₂S values. Pre-prandial and post-prandial rSO₂S values remained stable in both groups. Also, no association was detected between fetal splanchnic circulation parameters and neonatal splanchnic oxygenation. RSO₂S values were strongly correlated to gestational age and birth weight. During the whole week, except for the first 2 days, infants with umbilical catheters had significantly lower rSO₂S values than infants without.  Conclusion: Our data suggest that the key factor in splanchnic oxygenation is feeding, not the feeding modality. In addition, the umbilical vein catheter had a negative impact on splanchnic oxygenation.  Clinical Trial Registration: The Effect of Neonatal Feeding Modalities on Splanchnic Oxygenation, NCT05513495,  https://clinicaltrials.gov/ct2/results cond=&term=NCT05513495&cntry=TR&state=&city=&dist= . Retrospectively registered, date of registration: August 2022. What is Known: • It is known that preterm infants with IUGR are at increased risk of hypoxic-ischemic intestinal damage and impaired splanchnic oxygenation. What is New: • The key factor in splanchnic oxygenation of preterm infants with IUGR is feeding, not the feeding modality (drip or intermittent). • In addition, the umbilical vein catheter had a negative impact on splanchnic oxygenation.

Cerebral and splanchnic near-infrared spectroscopic dataset in premature newborns receiving packed red blood cell transfusion

This article presents the near-infrared spectroscopy (NIRS) dataset of cerebral (StO₂c) and splanchnic (StO₂s) oxygenation in 29 stable premature infants admitted to a tertiary neonatal intensive care unit who received elective packed red blood cell transfusion (PRBCT) to treat anemia of prematurity. StO₂c and StO₂s data were prospectively recorded continuously from at least 4 hours before the beginning of PRBCT until 24 hours after its completion, using a 4-wavelength near-infrared spectroscopy (NIRS) monitor (FORE-SIGHT® absolute cerebral oximeter, CASMED, Branford, Connecticut, 06405 USA). StO₂ data were downloaded as an analog output at a sampling rate of 1000Hz and aligned along the time axis in LabChart reader format (.adicht files) using a PowerLab data acquisition system [1] (PowerLab®, ADInstruments, Sydney, Australia). The .adicht files were then converted into .mat file format using a Python script (Python^TM version 3.7.3 [2]) and resampled at 1Hz for faster processing. Data that could not be physiologically explained (e.g., the absence of variability, [3] a 30% step change in StO₂ between two subsequent data points for StO₂[4]), as well as the data during the period of 'cares' were presumed to be artefactual and were replaced with 'NaN' or 'Not a Number' which is recognised by Matlab [5] (MATLAB 9.3, The MathWorks, Inc., Massachusetts, United States) and ignored for all subsequent processing while maintaining the correct time point of the StO₂ signals. The data were then exported into Microsoft Excel format. The splanchnic cerebral oxygenation ratio (SCOR) was calculated as the ratio of StO₂s/StO₂c. A 4-hour mean pre-transfusion values (StO₂s 0, StO₂c 0, SCOR 0) and post-transfusion hourly mean values (1-28) were determined. Secondary data were derived from a Mixed Models for Repeated Measures (MMRM) analysis with the time point fitted as a fixed effect and the infant fitted as a random effect. The MMRM was used to perform paired comparisons between pre-transfusion and each of the post-baseline values. This article only provides the NIRS data. The secondary data and demography can be found in the article "Splanchnic-Cerebral Oxygenation Ratio associated with Packed Red Blood Cell Transfusion in preterm infants", published in Transfusion Medicine. [6] The data will be of use to researchers in neonatology, transfusion medicine, and physiology to understand changes in cerebral and splanchnic oxygenation associated with PRBCT. Data collection, processing, and analysis can be remodelled in larger multicentric randomised controlled studies to evaluate the effect of transfusion and feeding on transfusion-associated necrotising enterocolitis. The data are also helpful to explore the autoregulatory behaviour of the brain and gut when the oxygen content of blood is increased by administering PRBCT.

Abdominal Near Infrared Spectroscopy can be reliably used to measure splanchnic oxygenation changes in preterm infants

OBJECTIVE

Near-infrared spectroscopy (NIRS) allows assessment of regional tissue oxygen delivery and extraction. There are doubts regarding reliability of gut NIRS measurements. This study assesses reliability of NIRS for monitoring gut oxygenation.

STUDY DESIGN

Splanchnic tissue haemoglobin index (sTHI), tissue oxygenation index (sTOI) and fractional tissue oxygen extraction (sFTOE) changes during blood transfusion were measured using NIRS and compared to stable control infants. Infants were grouped into 3 chronological age groups: 1-7, 8-28 and ≥29 days of life.

RESULTS

sTHI, sTOI significantly increased, and sFTOE reduced following blood transfusion in all age group infants (n = 59), with no changes seen in control infants (n = 12). Baseline characteristics including gestational age and feed volumes did not differ between groups.

CONCLUSION

Gut perfusion measured by NIRS improved in infants who received blood transfusion, a change not seen in the control group, thus suggesting NIRS is a reliable method to measure splanchnic tissue oxygenation.

Splanchnic-cerebral oxygenation ratio associated with packed red blood cell transfusion in preterm infants

BACKGROUND

Splanchnic-cerebral oxygenation ratio (SCOR), the ratio of splanchnic tissue oxygen (StO₂ s) to simultaneously measured cerebral tissue oxygen (StO₂ c), has been described as a surrogate to detect impaired splanchnic oxygenation associated with hypoperfusion status such as necrotizing enterocolitis. This concept is based on the presumption that any change in SCOR indicates a corresponding change in splanchnic tissue oxygenation as the numerator, whereas cerebral tissue oxygenation as the denominator remains stable. However, it is questionable to utilise this concept to detect splanchnic oxygenation changes in the context of packed red blood cell transfusion (PRBCT).

AIM

The current study examines the contribution of both cerebral and splanchnic oxygenation components to PRBCT-associated SCOR changes in preterm infants.

DESIGN

Prospective cohort study.

SETTING

Neonatal intensive care.

PATIENTS

Hemodynamically stable infants: Gestation <32 weeks; birth weight <1500 g; postmenstrual age <37 weeks: tolerating ≥120 ml/kg/day feed volume.

INTERVENTIONS

PRBCT at 15 ml/kg, over 4 h.

MAIN OUTCOME MEASURES

Transfusion-associated changes were determined by performing mixed models for repeated measures analysis between the 4-h mean pre-transfusion values (SCOR 0, StO₂ s 0, and StO₂ c 0) and the post-transfusion hourly mean values for the next 28 h (SCOR 1-28, StO₂ s 1-28, and StO₂ c 1-28). Dunnett's method was used to adjust for the multiplicity of the p value.

RESULTS

Of 30 enrolled infants 14 [46.7%] male; median [IQR] birth weight, 923 [655-1064] g; gestation, 26.4 [25.5-28.1] weeks; enrolment weight, 1549 [1113-1882] g; and postmenstrual age, 33.6 [32.4-35.0] weeks, one infant was excluded because of corrupted NIRS data. With the commencement of PRBCT, SCOR demonstrated a downward trend throughout the study period. This drift was associated with an increasing StO₂ c trend, while StO₂ s remained unchanged throughout the study period.

CONCLUSIONS AND RELEVANCE

PRBCT-associated SCOR decrease suggests improvement in cerebral oxygenation rather than worsening splanchnic oxygenation. Our study underlines that it is necessary to determine individual components of SCOR, namely cerebral and splanchnic StO₂ to understand SCOR changes in the context of PRBCT.

Hierarchical improvement of regional tissue oxygenation after packed red blood cell transfusion

Background

It is well established that counter-regulation to hypoxia follows a hierarchical pattern, with brain-sparing in preference to peripheral tissues. In contrast, it is unknown if the same hierarchical sequence applies to recovery from hypoxia after correction of anemia with packed red blood cell transfusion (PRBCT).

Objective

To understand the chronology of cerebral and splanchnic tissue oxygenation resulting after correction of anemia by PRBCT in preterm infants using near-infrared spectroscopy (NIRS).

Design

Prospective cohort study.

Setting

Neonatal intensive care.

Patients included

Haemodynamically stable infants: <32 weeks gestation, <37weeks postmenstrual age, <1500 grams birth weight; and ≥120 mL/kg/day feeds tolerated.

Intervention

PRBCT at 15 mL/Kg over 4 hours.

Main outcome measures

Transfusion-associated changes were determined by comparing the 4-hour mean pre-transfusion cerebral and splanchnic fractional tissue oxygen extraction (FTOEc0; FTOEs0) with hourly means during (FTOEc1-4; FTOEs1-4) and for 24 hours after PRBCT completion (FTOEc5-28; FTOEs5-28).

Results

Of 30 enrolled infants, 14[46.7%] male; median[IQR] birth weight, 923[655–1064]g; gestation, 26.4[25.5–28.1]weeks; enrolment weight, 1549[1113–1882]g; and postmenstrual age, 33.6[32.4–35]weeks, 1 infant was excluded because of corrupted NIRS data. FTOEc significantly decreased during and for 24 hours after PRBCT (p < 0.001), indicating prompt improvement in cerebral oxygenation. In contrast, FTOEs showed no significant changes during and after PRBCT (p>0.05), indicating failure of improvement in splanchnic oxygenation.

Conclusion

Improvement in regional oxygenation after PRBCT follows the same hierarchical pattern with a prompt improvement of cerebral but not splanchnic tissue oxygenation. We hypothesise that this hierarchical recovery may indicate continued splanchnic hypoxia in the immediate post-transfusion period and vulnerability to transfusion-associated necrotizing enterocolitis (TANEC). Our study provides a possible mechanistic underpinning for TANEC and warrants future randomised controlled studies to stratify its prevention.

Regional Splanchnic Oxygenation during Continuous versus Bolus Feeding among Stable Preterm Infants

Introduction: There is no agreement regarding the best method for tube-feeding preterm infants. Few studies, to date, have evaluated the influence of different methods of enteral feeding on intestinal oxygenation. The use of near-infrared spectroscopy (NIRS) has permitted the noninvasive measurement of splanchnic regional oxygenation (rSO₂S) in different clinical conditions. The aim of this prospective, single-center study was to compare rSO₂S during continuous versus bolus feeding among stable preterm infants. Methods: Twenty-one preterm infants, less than 32 weeks gestation and appropriate for gestational age, were enrolled. All infants were clinically stable and on full tube feedings. Each infant received a bolus feeding initially (20 min duration), and after 3 h, a continuous feeding (5 h duration). Infants were evaluated 30 min before and 30 min after the bolus and continuous feedings. The regional splanchnic saturation (rSO₂S) was measured using near-infrared spectroscopy (NIRS) technology and systemic saturation was measured with pulse oximetry. From these measurements, we calculated the splanchnic fractional oxygen extraction ratio (FOES) for each of the four intervals. Results: rSO₂S decreased after continuous vs. bolus feeding (p = 0.025), while there was a trend toward decreased SaO₂ after bolus feeding (p = 0.055). The FOES, which reflects intestinal oxygen extraction, was not affected by the feeding mode (p = 0.129). Discussion/Conclusion: Continuous vs. bolus feeding decreases rSO₂S but does not affect oxygen extraction by intestinal tissue; after bolus feeding there was a trend towards decreased systemic saturation.

Regional tissue oxygenation and conventional indicators of red blood cell transfusion in anaemic preterm infants

BACKGROUND

It is unresolved whether low haemoglobin (Hb) and symptoms of anaemia reflect oxygen delivery-consumption imbalances (fractional tissue oxygen extraction [FTOE]). Here, we test whether pre-transfusion Hb and symptoms of anaemia correlate with pre-transfusion cerebral and splanchnic FTOE.

METHODS

This prospective cohort study was carried out between Sept 1, 2014 and Nov 30, 2016 at Nepean Hospital, Sydney, Australia. The study enroled haemodynamically stable preterm infants: gestation <32 weeks; birth weight <1500 gs; postmenstrual age <37weeks, who received 15 mL/kg packed red blood cell transfusion (PRBCT) based on low Hb and symptoms of anaemia. FTOE was determined using simultaneous monitoring of near-infrared spectroscopy and pulse oximetry for 4 h before PRBCT.

FINDINGS

The study enroled 29 infants born with a median gestation of 26.4 weeks (IQR 25.4-28.1), birth weight 922 g (655-1064), at postmenstrual age 33.6 weeks (31.7-34.9), and weight 1487 g (1110-1785). There was no significant correlation between Hb (median 97 g/L, IQR 87-100) and cerebral FTOE (r=-0.12, 95% CI -0.47 to 0.27; p = 0.54, n = 29) as well as splanchnic FTOE (r=-0.09, 95% CI -0.45 to 0.29; p = 0.64, n = 29). Median cerebral FTOE (p = 0.67) and splanchnic FTOE (p = 0.53) did not differ between symptomatic and asymptomatic groups.

INTERPRETATION

Our preliminary findings suggest that pre-transfusion Hb and symptoms of anaemia might not accurately reflect oxygen delivery-consumption imbalances in both the brain and the gut. A lack of correlation with cerebral FTOE might be presumed to be due to the brain-sparing effect. However, the lack of correlation with splanchnic FTOE is more concerning. Hence, these results warrant larger studies incorporating FTOE along with the conventional criteria in the transfusion algorithm.

FUNDING

The study was funded (for the purchase of NIRS sensors) by the Australian Women and Children's Research Foundation.

Role of Near-infrared Spectroscopy in the Diagnosis and Assessment of Necrotizing Enterocolitis

Near-infrared spectroscopy (NIRS) is a noninvasive, bedside diagnostic tool that could assist in the early diagnosis of necrotizing enterocolitis (NEC) in preterm neonates. NIRS is a safe and effective clinical tool in the neonatal intensive care unit to detect abnormal alterations in tissue perfusion and oxygenation. In addition, NIRS could also detect the complications of NEC, such as bowel necrosis and perforation. NEC is the most common gastrointestinal complication associated with preterm birth and critically ill infants. It is observed in 6-10% of preterm neonates, weighing below 1500 g, leading to considerable morbidity, mortality, and healthcare cost burden. The mortality rate ranges from 20 to 30%, highest in NEC infants undergoing surgery. NIRS is a promising diagnostic modality that could facilitate the early diagnosis of NEC and early detection of complications alone or with the imaging modalities.

Effects of Caffeine on Splanchnic Oxygenation in Preterm Infants

OBJECTIVE

The aim of this study is to assess the effects of administering 20 mg/kg loading dose of caffeine citrate intravenously on splanchnic oxygenation in preterm infants.

STUDY DESIGN

The infants with a gestational age (GA) of <34 weeks who were administered with a 20 mg/kg intravenous loading dose of caffeine citrate within 48 hours after birth were investigated prospectively. Regional splanchnic oxygen saturation (rsSO₂) and splanchnic fractional tissue oxygen extraction rate (sFTOE) were measured using near-infrared spectroscopy before caffeine infusion, immediately after caffeine infusion and 1, 2, 3, 4, and 6 hours (h) after dose completion; postdose values were compared with predose values.

RESULTS

A total of 41 infants with a mean GA of 29.2 ± 1.6 weeks and birth weight of 1,315 ± 257 g as well as postnatal age of 32.2 ± 10.8 hours were included in the study. rsSO₂ significantly reduced from 63.1 to 57.5% immediately after caffeine infusion, 55.1% after 1 hour, and 55.2% after 2 hours with partial recovery at 3-hour postdose. sFTOE increased correspondingly.

CONCLUSION

Caffeine reduces splanchnic oxygenation and increases splanchnic oxygen extraction for at least 2 hours with partial recovery to predose levels at 3-hour postdose.

Effects of Pneumoperitoneum on Splanchnic Oxygenation during Abdominal Laparoscopic Surgery in Paediatric Patients: A prospective, Observational Study

Objective

Pneumoperitoneum can cause disruption in splanchnic perfusion. This study aims to investigate effects of pneumoperitoneum on splanchnic oxygenation during abdominal laparoscopic surgery in paediatric patients with NIRS (Near-Infrared Spectroscopy).

Material and methods

A total of 45 patients between 1 and 4 years of age with ASA physical status I–II and scheduled to undergo abdominal laparoscopic surgery under general anaesthesia were enrolled in this prospective, observational surgery. No premedication was used. Standard monitoring and regional splanchnic saturation (rSPcO₂), regional cerebral oxygen saturation (rScO₂) with NIRS were established before anaesthesia. Anaesthesia was induced with an inhalational agent and maintained with an oxygen/air mixture and sevoflurane. Peripheral oxygen saturation (SPO₂), rSPcO₂, rScO₂, heart rate (HR), mean arterial pressure (MAP), end tidal CO₂ (Et-CO₂), and insufflation pressure (IP) were continuously monitored during administration of anaesthesia and recorded. After intubation (baseline T0); before CO₂ insufflation induced pneumoperitoneum (PP) (T1); CO₂ PP insufflation (T2); 5 minutes after PP insufflation (T3); 10 minutes after PP insufflation (T4); 15 minutes after PP insufflation (T5); 20 minutes after PP insufflation (T6); 30 minutes after PP insufflation (T7), 60 minutes after PP insufflation (T8), and after desufflation (T9). Bradycardia and hypotension were recorded. Paracetamol IV 10 mg kg⁻¹ was applied for post-operative analgesia. p<0.05 wasconsidered significant.

Results

HR, rScO₂, and rSPcO₂ decreased at all measured time intervals when compared to T0 (p<0.01) MAP decreased at T1 compared to T0 (p<0.001). Et-CO₂ increased at T3-T4-T5-T6 compared to T0 (p<0.001).

Conclusion

We found that pneumoperitoneum reduced splanchnic oxygenation during laparoscopic abdominal surgery in paediatric patients, which was measured using NIRS.

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.

Abnormal Splanchnic Regional Saturations in a Preterm Infant That Developed Necrotizing Enterocolitis Following a Red Blood Cell Transfusion

BACKGROUND

Necrotizing enterocolitis (NEC) has been associated with red blood cell (RBC) transfusions in preterm infants. Near-infrared spectroscopy (NIRS) can be used to noninvasively monitor regional oxygen saturations (rSO2).

CLINICAL FINDINGS

This former 28-week female premature infant, 29 days old, received an RBC transfusion due to increased apneic spells and a hematocrit of 27%. Within 24 hours she developed abdominal distension and passed a bloody stool (Bell's stage 2 NEC on abdominal x-ray). She completed 7 days of antibiotics and nothing-by-mouth status and was discharged home on room air and oral feedings on day of life 70.

PRIMARY DIAGNOSIS

We describe the presentation of NEC following a RBC transfusion in a preterm infant monitored with cerebral and splanchnic NIRS.

INTERVENTIONS

Mean rSO2 (cerebral and splanchnic) measurements were continuously recorded and calculated in 30-minute periods at baseline (prior to packed RBC transfusion), every hour during the RBC transfusion, and every 3 hours for the following 48 hours.

OUTCOMES

In this infant, average baseline splanchnic rSO2 was low at 46.5%, and increased during transfusion to 65%. However, following the RBC transfusion and an enteral feeding, splanchnic rSO2 dramatically decreased to 26%, and remained low until the time of NEC diagnosis.

PRACTICE RECOMMENDATIONS

To develop awareness of the increased risk for NEC in premature infants with significant anemia that receive packed RBC transfusions. With further studies and education, NIRS could be a valuable tool for the nurses and medical team to identify these at-risk neonates.

Association of Bolus Feeding With Splanchnic and Cerebral Oxygen Utilization Efficiency Among Premature Infants With Anemia and After Blood Transfusion

IMPORTANCE

The pathogenesis of transfusion-associated necrotizing enterocolitis remains elusive. Splanchnic hypoperfusion associated with packed red blood cell transfusion (PRBCT) and feeding has been implicated, but studies of splanchnic tissue oxygenation with respect to feeding plus PRBCT are lacking.

OBJECTIVE

To investigate the oxygen utilization efficiency of preterm gut and brain challenged with bolus feeding during anemia and after transfusion using near-infrared spectroscopy.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study conducted from September 1, 2014, to November 30, 2016, at a tertiary neonatal intensive care unit included 25 hemodynamically stable infants with gestational age less than 32 weeks, birth weight less than 1500 g, and postmenstrual age younger than 37 weeks. Data analysis was performed from August 1, 2017, to October 31, 2018.

EXPOSURES

Infants received PRBCT (15 mL/kg for 4 hours) and at least 120 mL/kg daily of second hourly bolus feedings.

MAIN OUTCOMES AND MEASURES

Splanchnic fractional tissue oxygen extraction (FTOEs) and cerebral fractional tissue oxygen extraction (FTOEc) measures were made during 75-minute feeding cycles that comprised a 15-minute preprandial feeding phase (FP0) and 4 contiguous 15-minute postprandial feeding phases (FP1, FP2, FP3, and FP4; each 15 minutes long). The intraindividual comparisons of feeding-related changes were evaluated during the pretransfusion epoch (TE0: 4 hours before onset of transfusion) and 3 TEs after transfusion (TE1: first 8 hours after PRBCT completion; TE2: 9-16 hours after PRBCT completion; and TE3: 17-24 hours after PRBCT completion).

RESULTS

Of 25 enrolled infants (13 [52%] female; median birth weight, 949 g [interquartile range {IQR}, 780-1100 g]; median gestational age, 26.9 weeks [IQR, 25.9-28.6 weeks]; median enrollment weight, 1670 g [IQR, 1357-1937 g]; and median postmenstrual age, 34 weeks [IQR, 32.9-35 weeks]), 1 infant was excluded because of corrupted near-infrared spectroscopy data. No overall association was found between FTOEs and FPs in a multivariable repeated-measures model that accounted for transfusion epochs (primary analysis approach) (FP0: mean estimate, 11.64; 95% CI, 9.55-13.73; FP1: mean estimate, 12.02; 95% CI, 9.92-14.11; FP2: mean estimate, 12.77; 95% CI, 10.68-14.87; FP3: mean estimate, 12.54; 95% CI, 10.45-14.64; FP4: mean estimate, 12.98; 95% CI, 10.89-15.08; P = .16 for the FP association). However exploratory analyses of postprandial changes in FTOEs undertaken for each transfusion epoch separately found evidence of increased postprandial FTOEs during TE1 (mean [SD] FTOEs, 10.55 [5.5] at FP0 vs 13.21 [5.96] at FP4, P = .046). The primary and exploratory analyses found no association between FTOEc and feeding phases, suggesting that cerebral oxygenation may be protected.

CONCLUSIONS AND RELEVANCE

The findings suggest that enteral feeding may be associated with gut ischemia and potentially transfusion-associated necrotizing enterocolitis. The postprandial changes in FTOEs appear to warrant further investigation in larger randomized studies.

Influence of enteral feeding and anemia on tissue oxygen extraction after red blood cell transfusion in preterm infants

BACKGROUND

Understanding factors that impact tissue oxygen extraction may guide red blood cell (RBC) transfusion decision making in preterm infants. Our objective was to assess the influence of enteral feeding and anemia on cerebral and mesenteric oxygen saturation (Csat and Msat) and fractional tissue oxygen extraction (cFTOE and mFTOE) over the entire time course of RBC transfusion.

STUDY DESIGN AND METHODS

Preterm, very low-birth-weight infants receiving RBC transfusions at a single center were enrolled. Near-infrared spectroscopy sensors measured Csat and Msat levels from an hour before transfusion to 24 hours after. During this period, changes in Csat, Msat, cFTOE, and mFTOE were described, and their association with enteral feeding status and pretransfusion degree of anemia were assessed using generalized estimating equations.

RESULTS

RBC transfusion data from 31 preterm infants were included. Infants receiving enteral feeds exhibited lower pretransfusion Msat. Infants with pretransfusion hematocrit greater than 30% exhibited higher pretransfusion Csat and lower pretransfusion cFTOE. Such differences in baseline measurements persisted through 24 hours after transfusion. However, no statistically significant differences in oxygenation measures over time by enteral feeding or anemia status were identified.

CONCLUSION

Compared to NPO, enteral feeding was associated with lower Msat; anemia (hematocrit ≤30%) was associated with lower Csat and higher cFTOE. Over the time course of RBC transfusion, trajectories of Csat, Msat, cFTOE and mFTOE did not differ by enteral feeding or anemia status.

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.

To Feed or Not to Feed: A Critical Overview of Enteral Feeding Management and Gastrointestinal Complications in Preterm Neonates with a Patent Ductus Arteriosus

The management of enteral feeds in preterm infants with a hemodynamically significant patent ductus arteriosus (hs-PDA) is a major challenge for neonatologists due to the fear of gastrointestinal (GI) complications. This review aims to analyze the available evidence on the complex relation between the presence and management of PDA, enteral feeding practices, and GI outcomes in the preterm population. There is limited evidence, based on small and heterogeneous trials, that hs-PDA may affect the splanchnic hemodynamic response to enteral feeds. While the presence of PDA seems a risk factor for adverse GI outcomes, the benefits of feeding withholding during pharmacological PDA treatment are controversial. The lack of robust evidence in support of or against a timely feeding introduction or feeding withholding during pharmacological PDA closure in preterm neonates does not allow to draw any related recommendation. While waiting for further data, the feeding management of this population should be carefully evaluated and possibly individualized on the basis of the infants’ hemodynamic and clinical characteristics. Large, multicentric trials would help to better clarify the physiological mechanisms underlying the development of gut hypoperfusion, and to evaluate the impact of enteral feeds on splanchnic hemodynamics in relation to PDA features and treatment.

The effect of enteral bolus feeding on regional intestinal oxygen saturation in preterm infants is age-dependent: a longitudinal observational study

Background

The factors that determine the effect of enteral feeding on intestinal perfusion after preterm birth remain largely unknown. We aimed to determine the effect of enteral feeding on intestinal oxygen saturation (r_intSO₂) in preterm infants and evaluated whether this effect depended on postnatal age (PNA), postmenstrual age (PMA), and/or feeding volumes. We also evaluated whether changes in postprandial r_intSO₂ affected cerebral oxygen saturation (r_cSO₂).

Methods

In a longitudinal observational pilot study using near-infrared spectroscopy we measured r_intSO₂ and r_cSO₂ continuously for two hours on postnatal Days 2 to 5, 8, 15, 22, 29, and 36. We compared preprandial with postprandial values over time using multi-level analyses. To assess the effect of PNA, PMA, and feeding volumes, we performed Wilcoxon signed-rank tests or logistic regression analyses. To evaluate the effect on r_cSO₂, we also used logistic regression analyses.

Results

We included 29 infants: median (range) gestational age 28.1 weeks (25.1–30.7) and birth weight 1025 g (580–1495). On Day 5, r_intSO₂ values decreased postprandially: mean (SE) 44% (10) versus 35% (7), P = .01. On Day 29, r_intSO₂ values increased: 44% (11) versus 54% (7), P = .01. Infants with a PMA ≥ 32 weeks showed a r_intSO₂ increase after feeding (37% versus 51%, P = .04) whereas infants with a PMA < 32 weeks did not. Feeding volumes were associated with an increased postprandial r_intSO₂ (per 10 mL/kg: OR 1.63, 95% CI, 1.02–2.59). We did not find an effect on r_cSO₂ when r_intSO₂ increased postprandially.

Conclusions

Our study suggests that postprandial r_intSO₂ increases in preterm infants only from the fifth week after birth, particularly at PMA ≥ 32 weeks when greater volumes of enteral feeding are tolerated. We speculate that at young gestational and postmenstrual ages preterm infants are still unable to increase intestinal oxygen saturation after feeding, which might be essential to meet metabolic demands.

Trial registration

For this prospective longitudinal pilot study we derived patients from a larger observational cohort study: CALIFORNIA-Trial, Dutch Trial Registry NTR4153.

Feeding during transfusion and the risk of necrotizing enterocolitis in preterm infants

OBJECTIVE

To evaluate the effect of withholding feeds during transfusion on transfusion associated acute gut injury (TRAGI).

STUDY DESIGN

Data were collected on 125 preterm infants before and after the practice of withholding feeds for 12-24 h during transfusion was instituted. Logistic regression was used to examine effects of withholding feeds on TRAGI rates.

RESULTS

A total of 19 (15%) infants developed NEC; 6/19 (32%) had TRAGI. Postnatal hydrocortisone use was associated with TRAGI (OR 8.97; 95% CI 1.17-68.46, p = 0.034). There was no difference in NEC rates (15.8 vs. 14.7%) and the proportions (22.2 vs. 40%) of TRAGI in the two time periods before and after instituting the standardized feeding regimen and practice of holding feeds during transfusion.

CONCLUSION

No significant decrease was noted in the rates of TRAGI after feeds were withheld during transfusion. Further studies are warranted to explore the relationship between feeds during transfusion and NEC.

Electrogastrography, Near-infrared Spectroscopy, and Acoustics to Measure Gastrointestinal Development in Preterm Babies

OBJECTIVES

The aim of the study was to obtain objective measures indicative of gastrointestinal maturity using 3 noninvasive technologies.

METHODS

Electrogastrography (EGG), abdominal near-infrared spectroscopy (NIRS), and bowel sound/acoustics (AC) monitoring were used simultaneously to obtain physiologic measures of the gastrointestinal system of 18 preterm and 5 term neonates who were tolerating enteral feedings. Measures of EGG slow wave voltage (EGG dominant power) and AC signal amplitude (AC dominant power) were obtained after spectral density analysis. Mean abdominal regional saturations (A-rSO2) were obtained directly from NIRS. The relationship of these 3 measures with postmenstrual age (PMA) was assessed.

RESULTS

The results of the 3 methods differed depending on whether the measurements were pre- or postprandial. Postprandial EGG dominant power increases with PMA (r = 0.67, P = 0.003), both pre- and postprandial abdominal NIRS mean regional saturation increase with PMA (r = 0.73, P < 0.001 and r = 0.55, P = 0.009), and postprandial AC dominant power (at 300-500 Hz) increases with PMA (r = -0.48, P = 0.025).

CONCLUSIONS

EGG, abdominal NIRS, and AC, whenever used simultaneously, can provide objective and synergistic measures that correlate with PMA. These findings may be helpful in the assessment of feeding readiness because they reveal quantitative measures suggestive of the developmental process of the gut.

Splanchnic NIRS monitoring in neonatal care: rationale, current applications and future perspectives

Near infrared spectroscopy (NIRS) provides a non-invasive, continuous monitoring of regional tissue oxygenation. NIRS assessment of neonatal splanchnic oxygenation (SrSO₂) has gained increasing interest over the last decade, as local hypoxia and ischemia underlie the most feared gut complications in neonates. Current literature provides encouraging evidence in support of SrSO₂ reliability in detecting mesenteric hemodynamic changes related to various physiological and pathological conditions in-term and preterm infants. Even so, while splanchnic NIRS monitoring looks promising for investigating gut physiopathology in research settings, further studies are needed to evaluate its feasibility as a routine monitoring tool in neonatal care and to investigate its potential role in clinical decision making. After a brief introduction to NIRS technical principles, this review aims to provide a complete overview of current neonatal applications for splanchnic NIRS monitoring, to discuss its possible limitations and to suggest future directions for research and clinical applications.

Feed-related Splanchnic Oxygenation in Preterm Infants With Abnormal Antenatal Doppler Developing Gut Complications

Preterm infants with antenatal absent or reversed end diastolic flow (AREDF) in umbilical arteries are at major risk for gastrointestinal (GI) complications, such as necrotizing enterocolitis, intestinal perforation and feeding intolerance. Near-infrared spectroscopy provides continuous monitoring of splanchnic oxygenation (SrSO2) and may represent a useful tool to predict GI outcomes in this high-risk population. This observational, pilot study assessed feed-related SrSO2 patterns at enteral feeding introduction and full enteral feeding (FEF) achievement in twenty AREDF infants with gestational age ≤34 weeks. Enrolled infants were divided into 2 groups according to the development versus lack of GI complications. Infants developing GI complications showed significantly lower SrSO2 and increased splanchnic oxygen extraction in response to enteral feeds at both enteral feeding introduction and FEF. The potential role of these findings in predicting GI complications in AREDF preterm infants seems promising and deserves further evaluation.

The effect of skin-to-skin care on cerebral oxygenation during nasogastric feeding of preterm infants

AIM

To describe cerebral oxygenation during gavage feeding of preterm infants during incubator and skin-to-skin care.

METHODS

Further analysis of data from two crossover studies comparing cerebral oxygenation, heart rate and oxygen saturation during skin-to-skin care with incubator care. Data were analysed in three epochs; 10 minutes prefeed, during-feed and 10 minutes postfeed. Measurements from infants fed during incubator care were compared with those obtained during skin-to-skin care.

RESULTS

In 39 infants [median (IQR) 27.8 (26.1-30.0) weeks' gestation], there was no difference in cerebral oxygenation between pre-, during- and postfeed. Heart rate increased by three beats per minute postfeed compared with during-feed. Twenty infants received two gavage feeds, one feed in the incubator and another during skin-to-skin care. There was no difference in cerebral oxygenation and heart rate; peripheral oxygen saturation decreased by 3% during feeding whilst skin-to-skin care compared with feeding in the incubator.

CONCLUSION

Cerebral oxygenation remained stable before, during and after gavage feeding in an incubator and during skin-to-skin care. The small decrease in oxygen saturation whilst receiving gavage feeding during skin-to-skin care is unlikely to be clinically important, providing reassurance that preterm infants maintain physiological stability during skin-to-skin care.

Near-infrared spectroscopy is a promising noninvasive technique for monitoring the effects of feeding regimens on the cerebral and splanchnic regions

AIM

The effects of different milk and, or, administration regimens on cerebro-splanchnic perfusion are still a matter of debate. We investigated the effects of the bolus administration of breast milk or formula on cerebro-splanchnic oximetry, function and perfusion, assessed by near-infrared spectroscopy (NIRS).

METHODS

This observational study of 30 infants fed with breast (n = 15) or formula (n = 15) milk, and matched for gestational age and birth weight, was carried out in the neonatal intensive care unit of the C Arrigo Children's Hospital, Alessandria, Italy, a tertiary-level referral centre, from October 2015 to December 2016. NIRS monitoring parameters, such as cerebral and splanchnic oximetry, fraction of tissue oxygen extraction and the cerebral-splanchnic ratio, were recorded before, during and after feeding.

RESULTS

Breast milk led to a significant increase in cerebro-splanchnic oximetry and tissue oxygen extraction (p < 0.001) during and after feeding, and the cerebro-splanchnic perfusion ratio was significantly higher (p < 0.001) in the breast than formula group.

CONCLUSION

Our study results suggest that breast milk was better tolerated than formula, requiring lower energy expenditure and lower cerebro-splanchnic haemodynamic redistribution. The findings could prompt investigations using NIRS as a promising noninvasive tool for cerebral and splanchnic longitudinal monitoring during neonatal feeding.

Anemia, red blood cell transfusions, and necrotizing enterocolitis

In the past 15 years, multiple clinical studies have identified a temporal association between red blood cell (RBC) transfusions and necrotizing enterocolitis (NEC). With some variability, most of these studies indicate that up to one-third of all cases of NEC involving very low-birth weight infants may occur within 24-48h after receiving a RBC transfusion. There is also evidence that the risk of such transfusion-associated NEC may be higher in infants transfused with the greatest severity of anemia. In this article, we summarize the clinical evidence pertaining to these issues; specifically, the contribution of RBC transfusions, and the contribution of severity of underlying anemia, to the pathogenesis of a type of NEC potentially termed, "transfusion/anemia-associated NEC."

Splanchnic-Cerebral Oxygenation Ratio Decreases during Enteral Feedings in Anemic Preterm Infants: Observations under Near-Infrared Spectroscopy

BACKGROUND

Anemia is common in premature infants. Due to risks with red blood cell transfusions, many anemic infants are not transfused. The implications of this pathophysiologic status, especially at times of increased metabolic demand (enteral feedings), is not well understood. Near-infrared spectroscopy (NIRS) allows for the noninvasive determination of regional oxygen saturations (rSO2) in tissues such as the brain and mesentery, giving insight into their oxygen sufficiency.

OBJECTIVE

We tested the hypothesis that during enteral feedings very low birth weight (VLBW) infants with a hematocrit ≤28% will experience a decrease in splanchnic rSO2 and splanchnic-cerebral oxygenation ratio (SCOR).

METHODS

This prospective, observational, 2-centered study included VLBW infants receiving full enteral feedings with a hematocrit ≤28%. Cerebral and splanchnic rSO2 were monitored via NIRS for 24 h. Average values were calculated for periods immediately preceding, during, and after each feeding. SCOR was calculated from these values (rSO2 splanchnic/rSO2 cerebral), and data were analyzed using a linear mixed effect model.

RESULTS

Fifty neonates with a median gestational age of 28 weeks (range 23-32), a birth weight of 1,118 ± 284 g (mean ± SD), and a hematocrit of 26 ± 2% (mean ± SD) were studied. During feedings, SCOR decreased significantly from baseline (0.72 ± 0.17 to 0.69 ± 0.17, p = 0.043). With feedings, there was a trend of decreased splanchnic rSO2 (47 ± 11 to 45 ± 10, p = 0.057) and no change in cerebral rSO2 (66 ± 8 to 66 ± 7, p = 0.597).

CONCLUSIONS

VLBW infants with a hematocrit ≤28% had a decrease in SCOR and a trend towards decreased splanchnic rSO2 with enteral feedings.

Bolus feeding has no effect on cerebral hemodynamics, irrespective of gestational age

OBJECTIVE

By multichannel near-infrared spectroscopy, we studied if gestational age has any influence on preterm cerebral hemodynamics, during bolus feeding.

METHODS

Oxy-haemoglobin (HbO₂), as cerebral blood flow estimate, and the ratio between HbO₂ and total haemoglobin (HbO₂/HbTot), as cerebral oxygenation estimate, were assessed in 40 stable premature infants, during a 10 min bolus feeding.

RESULTS

We found no effect of any of the gestational ages studied (25-34 weeks) either on cerebral blood flow or on oxygenation, during a bolus feeding procedure.

CONCLUSIONS

Bolus feeding appears not to affect cerebral hemodynamics of uncritically preterm infants, irrespective of gestational age.

Impact of Continuous vs Bolus Feeding on Splanchnic Perfusion in Very Low Birth Weight Infants: A Randomized Trial

OBJECTIVE

To detect changes in splanchnic perfusion and oxygenation induced by 2 different feeding regimens in infants with intrauterine growth restriction (IUGR) and those without IUGR.

STUDY DESIGN

This was a randomized trial in 40 very low birth weight infants. When an enteral intake of 100 mL/kg/day was achieved, patients with IUGR and those without IUGR were randomized into 2 groups. Group A (n = 20) received a feed by bolus (in 10 minutes), then, after at least 3 hours, received the same amount of formula by continuous nutrition over 3 hours. Group B (n = 20) received a feed administered continuously over 3 hours, followed by a bolus administration (in 10 minutes) of the same amount of formula after at least 3 hours. On the day of randomization, intestinal and cerebral regional oximetry was measured via near-infrared spectroscopy and Doppler ultrasound (US) of the superior mesenteric artery was performed. Examinations were performed before the feed and at 30 minutes after the feed by bolus and before the feed, at 30 minutes after the start of the feed, and at 30 minutes after the end of the feed for the 3-hour continuous feed.

RESULTS

Superior mesenteric artery Doppler US showed significantly higher perfusion values after the bolus feeds than after the continuous feeds. Near-infrared spectroscopy values remained stable before and after feeds. Infants with IUGR and those without IUGR showed the same perfusion and oxygenation patterns.

CONCLUSION

According to our Doppler US results, bolus feeding is more effective than continuous feeding in increasing splanchnic perfusion.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01341236.

Review of splanchnic oximetry in clinical medicine

Global tissue perfusion and oxygenation are important indicators of physiologic function in humans. The monitoring of splanchnic oximetry through the use of near-infrared spectroscopy (NIRS) is an emerging method used to assess tissue oxygenation status. Splanchnic tissue oxygenation (SrSO2) is thought to be potentially of high value in critically ill patients because gastrointestinal organs can often be the first to suffer ischemic injury. During conditions of hypovolemia, cardiac dysfunction, or decreased oxygen-carrying capacity, blood flow is diverted toward vital organs, such as the brain and the heart at the expense of the splanchnic circulation. While monitoring SrSO2 has great potential benefit, there are limitations to the technology and techniques. SrSO2 has been found to have a relatively high degree of variability that can potentially make it difficult to interpret. In addition, because splanchnic organs only lie near the skin surface in children and infants, and energy from currently available sensors only penetrates a few centimeters deep, it can be difficult to use clinically in a noninvasive manner in adults. Research thus far is showing that splanchnic oximetry holds great promise in the ability to monitor patient oxygenation status and detect disease states in humans, especially in pediatric populations.

Mesenteric near-infrared spectroscopy and risk of gastrointestinal complications in infants undergoing surgery for congenital heart disease

We hypothesised that lower mesenteric near-infrared spectroscopy values would be associated with a greater incidence of gastrointestinal complications in children weighing <10 kg who were recovering from cardiac surgery. We evaluated mesenteric near-infrared spectroscopy, central venous oxygen saturation, and arterial blood gases for 48 hours post-operatively. Enteral feeding intake, gastrointestinal complications, and markers of organ dysfunction were monitored for 7 days. A total of 50 children, with median age of 16.7 (3.2-31.6) weeks, were studied. On admission, the average mesenteric near-infrared spectroscopy value was 71±18%, and the systemic oxygen saturation was 93±7.5%. Lower admission mesenteric near-infrared spectroscopy correlated with longer time to establish enteral feeds (r=-0.58, p<0.01) and shorter duration of feeds at 7 days (r=0.48, p<0.01). Children with gastrointestinal complications had significantly lower admission mesenteric near-infrared spectroscopy (58±18% versus 73±17%, p=0.01) and higher mesenteric arteriovenous difference of oxygen at admission [39 (23-47) % versus 19 (4-27) %, p=0.02]. Based on multiple logistic regression, admission mesenteric near-infrared spectroscopy was independently associated with gastrointestinal complications (Odds ratio, 0.95; 95% confidence interval, 0.93-0.97; p=0.03). Admission mesenteric near-infrared spectroscopy showed an area under the receiver operating characteristic curve of 0.76 to identify children who developed gastrointestinal complications, with a suggested cut-off value of 72% (78% sensitivity, 68% specificity). In this pilot study, we conclude that admission mesenteric near-infrared spectroscopy is associated with gastrointestinal complications and enteral feeding tolerance in children after cardiac surgery.

Relationship Between Near-Infrared Spectroscopy and Transabdominal Ultrasonography: Noninvasive Monitoring of Intestinal Function in Neonates

BACKGROUND

Near-infrared spectroscopy (NIRS) has the potential to continuously and noninvasively monitor intestinal function. This technology may be valuable because among neonates, intestinal maturity is highly variable and difficult to assess based solely on clinical signs. The aim of this study was to determine if there is an association between NIRS-based StO2 measurements and peristaltic activity assessed by transabdominal ultrasonography (US).

MATERIAL/METHODS

Nineteen neonates of gestational age >32 weeks were categorized according to "no/low" versus "normal/hyperactive" motility levels, based on blinded US scan results. StO2 was recorded every 2 s for 24 h, following the ultrasound recording. Differences between the resulting estimates of average StO2 (bias of fits) and goodness-of-fit (residuals) were evaluated.

RESULTS

Newborns with normal/hyperactive motility had higher mean StO2 than newborns with no/low motility (72.3±4.4 vs. 65.5±7.9, p<0.05, F=5.65). Residual errors were not significantly different between the 2 groups (p=0.213, F=0.213). A multivariate linear regression model using the means, residuals, and pairwise products of both, demonstrated more significant separation (0.47±0.26 vs. -0.24±0.33, p<0.01, F=27.4). A non-linear variant of the multivariate linear regression model demonstrated greatest separation (0.68±0.24 vs. -0.49±0.53, p<0.01, F=41.9).

CONCLUSIONS

This is the first study to demonstrate an association between NIRS-based StO2 measurements and peristaltic activity visualized by ultrasound imaging. NIRS may offer a continuous, noninvasive method to assess motility. This may have significant implications in premature infants at risk for feeding intolerance or necrotizing enterocolitis.

Effect of blood transfusion on intestinal blood flow and oxygenation in extremely preterm infants during first week of life

BACKGROUND

Extremely preterm infants receive frequent blood transfusions in the first week of life. The aim of this study was to measure the effect of blood transfusion on intestinal blood flow and oxygenation during the first week of life in extremely preterm infants.

STUDY DESIGN AND METHODS

Superior mesenteric artery (SMA) peak systolic velocity (PSV) and diastolic velocities were measured 30 to 60 minutes before and after transfusion. Splanchnic tissue hemoglobin index (sTHI), splanchnic tissue oxygenation index (sTOI), and splanchnic fractional tissue oxygen extraction (sFTOE) were measured continuously from 15 to 20 minutes before to after transfusion along with vital variables.

RESULTS

Twenty infants were studied (median gestational age, 26 weeks). Ten infants were partially fed (15-68 mL/kg/day). Heart rate and SaO2 remained unaltered; blood pressure increased significantly (p < 0.01) after transfusion. Mean SMA PSV (p = 0.63) and diastolic velocity (p = 0.65) remained unaltered. Mean pretransfusion SMA PSV was similar in partially fed (0.78 m/sec) compared to unfed infants (0.52 m/sec; p = 0.06) and the response to transfusion was not dissimilar. There was a significant increase in sTHI (mean difference, 32.3%; p < 0.01) and sTOI (14.6%; p = 0.03) and decrease in sFTOE (22.1%; p < 0.01) after transfusion. There was no significant difference in sTHI or sTOI between fed and unfed infants and their response to transfusion.

CONCLUSIONS

Blood transfusion increased blood pressure and intestinal tissue oxygenation but did not alter blood flow velocities. Partial feeding had no impact on intestinal blood flow and tissue oxygenation changes.

Variability in splanchnic tissue oxygenation during preterm red blood cell transfusion given for symptomatic anaemia may reveal a potential mechanism of transfusion-related acute gut injury

BACKGROUND

There is increasing evidence indicating an association between red blood cell (RBC) transfusions and necrotising enterocolitis (NEC) in preterm infants, especially late-onset NEC. This phenomenon is referred to as transfusion-related acute gut injury (TRAGI). One theory as to a pathophysiological mechanism is that transfusion may result in an ischemia-reperfusion injury to intestinal tissue. We tested the hypothesis that there is significantly greater variability during transfusion in splanchnic tissue oxygen saturation (SrSO2) than in cerebral tissue oxygen saturation (CrSO2).

MATERIALS AND METHODS

This was a prospective, observational study using near-infrared spectroscopy to monitor SrSO2 and CrSO2 in preterm neonates undergoing RBC transfusion for symptomatic anaemia. Mean, standard deviation, highest and lowest SrSO2 and CrSO2 values during each transfusion were determined. The greatest difference in SrSO2 and CrSO2 during each transfusion was calculated, along with the coefficient of variation.

RESULTS

We studied 37 subjects. Throughout all transfusions, the mean SrSO2 was 45.6% ±13.8 and the mean CrSO2 was 65.4% ±6.9 (p<0.001). The variability of SrSO2 was significantly greater than that of CrSO2. Averaging data from all subjects, the greatest difference in SrSO2 was 43.8% ±13.4 compared with 23.3% ±7.6 for CrSO2 (p<0.001). The mean coefficient of variation in all transfusions was 20.5% for SrSO2 and 6.0% for CrSO2 (p<0.001). Increasing post-conceptional age did not affect SrSO2 variability (R(2) =0.022; p=0.379), whereas CrSO2 variability during transfusion decreased with increasing post-conceptional age (R(2)=0.209; p=0.004).

DISCUSSION

In preterm infants, there is a large degree of tissue oxygenation variability in splanchnic tissue during RBC transfusion and this does not change with increasing maturity. We speculate that these findings, combined with lower average tissue oxygenation, may demonstrate susceptibility of the preterm gut to TRAGI.

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.

Feeding preterm infants during red blood cell transfusion is associated with a decline in postprandial mesenteric oxygenation

OBJECTIVE

To evaluate the mesenteric tissue oxygenation response in preterm infants fed and not fed during red blood cell (RBC) transfusions.

STUDY DESIGN

Prospective, observational comparison of mesenteric oxygenation using near-infrared spectroscopy in preterm infants (<33 weeks' at birth) who were fed or not fed during RBC transfusion. Tissue oxygenation means were examined up to 48 hours after each transfusion event.

RESULTS

Mean mesenteric regional oxygen saturation (rSO2) slopes during RBC transfusion of fed (n = 9) vs not fed (n = 8) infants ranged from -0.23 to +0.23 (mean 0.04) with no differences between groups (P = .480). However, following transfusions, postprandial mesenteric oxygenation means significantly declined in infants fed during transfusion compared with infants not fed during transfusion (P < .001). Infants fed during RBC transfusion had a mean 2.16 point decrease in rSO2 mesenteric oxygenation with each sequential feeding post-transfusion, whereas infants not fed during RBC transfusion increased their rSO2 postprandial mesenteric oxygenation by a mean of 2.09 points.

CONCLUSIONS

Mesenteric tissue oxygenation during RBC transfusion is not influenced by feeding status. However, infants fed during RBC transfusion had, for the next 15 hours, decreasing postprandial mesenteric tissue oxygenation patterns compared with infants not fed during RBC transfusion. Feeding during RBC transfusions may increase the risk for mesenteric ischemia and the development of transfusion-related necrotizing enterocolitis in preterm infants.

Bolus vs. continuous feeding: effects on splanchnic and cerebral tissue oxygenation in healthy preterm infants

BACKGROUND

Intermittent and continuous tube feeding modes are commonly used to feed preterm infants. However, there is no clear evidence regarding which method is better tolerated. We investigated the differences between bolus and continuous feeding in terms of cerebral and splanchnic oxygenation in healthy preterm infants.

METHODS

Thirty preterm infants underwent a simultaneous 6-h near-infrared-spectroscopy monitoring of cerebral and splanchnic oxygenation, during which they were fed twice through an orogastric tube: one meal was given as a 10-min bolus, and the other was given continuously over a period of 3 h. Oxygenation trends over time were evaluated and compared between bolus and continuous feeding modes.

RESULTS

Cerebral oxygenation did not change over time and did not differ between the two feeding techniques. Splanchnic oxygenation changed significantly over time and differed between the two feeding techniques, with a significant increase after bolus feeding and a remarkable reduction during continuous feeding.

CONCLUSION

Bolus and continuous feeding modes influence splanchnic oxygenation in healthy preterm infants differently. Further studies are needed to investigate possible underlying mechanisms and potential effects on feeding tolerance.

Abdominal near-infrared spectroscopy in preterm infants: a comparison of splanchnic oxygen saturation measurements at two abdominal locations

BACKGROUND

Splanchnic tissue oxygenation monitoring has been performed at both the liver and the infra-umbilical regions. It is unknown whether these measurements could be substituted one for the other when interpreting splanchnic oxygenation since they have not been measured simultaneously before.

AIMS

To evaluate the feasibility and safety of liver and infra-umbilical near-infrared spectroscopy (NIRS) monitoring in preterm infants with suspected necrotizing enterocolitis (NEC) and to assess the correlation and agreement between NIRS measurements performed simultaneously at the two abdominal locations.

STUDY DESIGN AND SUBJECTS

This study was part of a prospective observational cohort study. Preterm infants who were suspected of NEC or who had been diagnosed with NEC were included.

OUTCOME MEASURES

Liver oxygen saturation and infra-umbilical oxygen saturation were monitored simultaneously and continuously for 48h by NIRS.

RESULTS

NIRS monitoring was performed in 20 out of 24 infants for the entire 48-hour study period. No adverse effects were observed. Values of liver and infra-umbilical oxygen saturation correlated weakly (Spearman's rho=0.244, P<.001). On the Bland-Altman plot liver oxygen saturation was higher than infra-umbilical oxygen saturation (mean difference 6.6%, SD 22.5%).

CONCLUSIONS

Using NIRS as method for monitoring oxygen saturation simultaneously in both the liver and infra-umbilical regions is safe and feasible. Additionally, we demonstrated that values of liver and infra-umbilical oxygen saturation cannot be randomly substituted one for the other for the purpose of assessing splanchnic oxygenation.

Near-infrared spectroscopy: exposing the dark (venous) side of the circulation

The safety of anesthesia has improved greatly in the past three decades. Standard perioperative monitoring, including pulse oximetry, has practically eliminated unrecognized arterial hypoxia as a cause for perioperative injury. However, most anesthesia-related cardiac arrests in children are now cardiovascular in origin, and standard monitoring is unable to detect many circulatory abnormalities. Near-infrared spectroscopy provides noninvasive continuous access to the venous side of regional circulations that can approximate organ-specific and global measures to facilitate the detection of circulatory abnormalities and drive goal-directed interventions to reduce end-organ ischemic injury.

Continuous milk feeding versus intermittent bolus feeding in preterm infants

We aimed to assess the current knowledge on continuous versus intermittent bolus feeding in preterm infants. We found that existing evidence does not support the firm recommendation of one strategy among the many alternatives. However, although many areas remain to be investigated, it is probable that continuous feeding might be advantageous compared to intermittent feeding in favoring the faster establishment of full enteral feeding, and decreasing the risk of hypoxic-ischemic gut damage in preterm neonates in critical condition, especially SGA infants, by limiting their gastrointestinal oxygen requirement.

Transfusion-related necrotizing enterocolitis: a conceptual framework

Necrotizing enterocolitis (NEC) is a disease primarily of prematurity characterized by partial or entire gut necrosis and is associated with significant mortality and morbidity. Recent studies report that approximately 25% to 35% of very low-birth-weight infants less than 1500 g receiving packed red blood cell transfusions develop temporally associated NEC, known as transfusion-related NEC (TR-NEC). Although there are many known risk factors for NEC, this article focuses on 3 contributing factors: packed red blood cell transfusions, enteral feedings, and gastrointestinal immaturity. Previous data suggest that these factors may interact to affect neonatal intestinal tissue oxygenation, which may lead to tissue ischemia, resulting in intestinal injury. This article presents a conceptual framework that combines current theoretical perspectives for TR-NEC, and reviews previous research examining related variables and how their interaction may increase the risk for TR-NEC development. In addition, incorporation of the proposed framework to guide future research and nursing care in this area is discussed.

Near-infrared spectroscopy measurements of splanchnic tissue oxygenation during continuous versus intermittent feeding method in preterm infants

OBJECTIVES

The aim of the present study was to compare the effects of continuous and intermittent bolus milk feeding on splanchnic regional oxygenation (rSO₂S) in small-for-gestational age (SGA) and appropriate-for-gestational age (AGA) preterm infants.

METHODS

Infants with gestational age <32 weeks were prospectively studied by near-infrared spectroscopy. Each infant was given a milk bolus in ~10 minutes (intermittent feeding) followed after 3 hours by a 3-hour continuous feeding. rO₂S and splanchnic fractional oxygen extraction ratio (FOES [S = splanchnic]) were recorded 30 minutes before (T₀) and 30 minutes after the beginning of bolus feeding (T₁), 30 minutes before (T₂), at the end (T₃), and 30 minutes after the continuous feeding period (T₄).

RESULTS

rSO2S increased at T₁ in both AGA and SGA groups, whereas FOES did not vary during the study period. Moreover, we found that rSO2S was higher and FOES was lower at T₁ and T₃ in the AGA than in the SGA group.

CONCLUSIONS

Bolus milk feeding increases splanchnic oxygenation in both AGA and SGA infants, whereas continuous feeding does not. Splanchnic oxygenation is higher in AGA than in SGA infants both during bolus and continuous feeding. Continuous enteral feeding could help to limit the risk of hypoxic-ischemic gut damage in preterm infants in critical condition, especially in AGA infants.

Splanchnic-cerebral oxygenation ratio (SCOR) values in healthy term infants as measured by near-infrared spectroscopy (NIRS)

PURPOSE

The splanchnic-cerebral oxygenation ratio (SCOR) is a measurement comparing regional tissue oxygen saturation of splanchnic organs and brain tissue. SCOR has been previously proposed as a marker of clinical conditions associated with gut ischemia. Our goal was to determine SCOR values in healthy neonates in their first and second days of life.

METHODS

Prospective observational study measuring SCOR in term neonates in the nursery using near-infrared spectroscopy (NIRS).

RESULTS

Forty-five subjects with a mean gestational age of 39.4 ± 1.3 weeks were included. Mean SCOR on the first day was 0.90 ± 0.16 and 0.97 ± 0.16 on the second day, p = 0.02 (n = 45). No correlation was found between SCOR and gestational age; however, we did find a positive correlation between hour of life and SCOR values (r = 0.28, r(2) = 0.08, p < 0.01, two tails); SCOR appears to stabilize by 36 h.

CONCLUSIONS

Our findings demonstrate SCOR values in healthy neonates consistent with those previously theorized and help to validate it as a diagnostic measure. In addition, we have demonstrated that SCOR values may normally be lower in infants during their first days of life, and this information may be helpful to clinicians using NIRS as a diagnostic tool.

Global perfusion assessment and tissue oxygen saturation in preterm infants: where are we?

Near infrared spectroscopy (NIRS) monitoring is a new challenge for clinicians who deal with early detection of dangerous hypoperfusion in the brain, as well as in splanchnic and renal districts in critically ill preterm infants. Previous studies performed on infants and children with congenital heart disease, demonstrated the efficacy of this non-invasive method in managing hypoperfusive states pre, post and during cardiac surgery. Its use has improved post surgery outcome. NIRS monitoring has been used also to assess therapeutic intervention utility. Early identification of silent hypoperfusion has made NIRS use in preterm infants very interesting for neonatologists, especially where other techniques have failed. In this work, literature on this topic has been carefully examined, particularly the "two site NIRS" use in preterm infants, to evaluate how regional splanchnic oxygen saturation changes, both in physiological events, such as enteral feeding and in hemodynamic disorders, that occur in patients with significant patent ductus and in hypoperfusive states that lead to necrotizing enterocolitis.

Red blood cell transfusion-related necrotizing enterocolitis in very-low-birthweight infants: a near-infrared spectroscopy investigation

BACKGROUND

Recent evidence suggests that antecedent red blood cell (RBC) transfusions increase the risk for necrotizing enterocolitis (NEC), the most common gastrointestinal emergency encountered by very-low-birthweight (VLBW) infants. The underlying mechanism for this association is unknown. Altered oxygenation of the mesenteric vasculature during RBC transfusion has been hypothesized to contribute to NEC development and was investigated in this study.

STUDY DESIGN AND METHODS

Oxygenation patterns among four VLBW infants who developed transfusion-related NEC (TR-NEC) were compared to four VLBW infants with similar gestational age who were transfused but did not develop NEC (non-NEC). Cerebral and mesenteric patterns were recorded before, during, and 48 hours after RBC transfusion using near-infrared spectroscopy (NIRS) technology. Percentage change from mean baseline regional oxygen saturation values and cerebrosplanchnic oxygenation ratios were analyzed.

RESULTS

All TR-NEC infants (24-29 weeks' gestation; 705-1080 g) demonstrated greater variation in mesenteric oxygenation patterns surrounding transfusions than non-NEC infants (27.6-30 weeks' gestation; 980-1210 g). TR-NEC infants received larger mean volumes of total blood (27.75 ± 8.77 mL/kg) than non-NEC infants (15.25 ± 0.5 mL/kg).

CONCLUSION

Wide fluctuation and decreases in mesenteric oxygenation patterns are more pronounced in TR-NEC infants, especially before TR-NEC onset, compared to non-NEC infants. Greater total volume of infused blood was associated with TR-NEC in preterm infants. Using NIRS, larger prospective studies are needed to further evaluate potential risk factors for NEC in this high-risk population.

Newer monitoring techniques to determine the risk of necrotizing enterocolitis

Necrotizing enterocolitis affects up to 10% of neonates who are born weighing less than 1500 g. It has a high rate of morbidity and mortality, and predicting infants who will be affected has so far been unsuccessful. In this article, a number of new methods are discussed from the literature to determine if any currently available techniques may allow for the identification of patients who are at increased risk for developing this potentially lethal disease.