Peripheral Muscle Near-Infrared Spectroscopy in Neonates: Ready for Clinical Use? A Systematic Qualitative Review of the Literature

Assessment of Autoregulation of the Cerebral Circulation during Acute Lung Injury in a Neonatal Porcine Model

In neonates with acute lung injury (ALI), targeting lower oxygenation saturations is suggested to limit oxygen toxicity while maintaining vital organ function. Although thresholds for cerebral autoregulation are studied for the management of premature infants, the impact of hypoxia on hemodynamics, tissue oxygen consumption and extraction is not well understood in term infants with ALI. We examined hemodynamics, cerebral autoregulation and fractional oxygen extraction, as measured by near-infrared spectroscopy (NIRS) and blood gases, in a neonatal porcine oleic acid injury model of moderate ALI. We hypothesized that in ALI animals, cerebral oxygen extraction would be increased to a greater degree than kidney or gut oxygen extraction as indicative of the brain's adaptive efforts to increase cerebral oxygen extraction at the expense of splanchnic end organs. Fifteen anesthetized, ventilated 5-day-old neonatal piglets were divided into moderate lung injury by treatment with oleic acid or control (sham injection). The degree of lung injury was quantified at baseline and after establishment of ALI by blood gases, ventilation parameters and calculated oxygenation deficit, hemodynamic indices by echocardiography and lung injury score by ultrasound. PaCO2 was maintained constant during ventilation. Cerebral, renal and gut oxygenation was determined by NIRS during stepwise decreases in inspired oxygen from 50% to 21%, correlated with PaO2 and PvO2; changes in fractional oxygen extraction (ΔFOE) were calculated from NIRS and from regional blood gas samples. The proportion of cerebral autoregulation impairment attributable to blood pressure, and to hypoxemia, was calculated from autoregulation nomograms. ALI manifested as hypoxemia with increasing intrapulmonary shunt fraction, decreased lung compliance and increased resistance, and marked increase in lung ultrasound score. Brain, gut and renal NIRS, obtained from probes placed over the anterior skull, central abdomen and flank, respectively, correlated with concurrent SVC (brain) or IVC (gut, renal) PvO2 and SvO2. Cerebral autoregulation was impaired after ALI as a function of blood pressure at all FiO2 steps, but predominantly by hypoxemia at FiO2 < 40%. Cerebral ΔFOE was higher in ALI animals at all FiO2 steps. We conclude that in an animal model of neonatal ALI, cerebrovascular blood flow regulation is primarily dependent on oxygenation. There is not a defined oxygenation threshold below which cerebral autoregulation is impaired in ALI. Cerebral oxygen extraction is enhanced in ALI, reflecting compensation for exhausted cerebral autoregulation due to the degree of hypoxemia and/or hypotension, thereby protecting against tissue hypoxia.

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.

Near-Infrared Spectroscopy to Guide and Understand Effects of Red Blood Cell Transfusion

This review is a summary of available evidence regarding the use of near-infrared spectroscopy (NIRS) to help better guide and understand the effects of red blood cell (RBC) transfusion in neonatal patients. We review recent literature demonstrating the changes that take place in regional tissue oxygen saturation (rSO2) resulting from RBC transfusion. We also discuss in detail if any correlation exists between rSO2 and hemoglobin values in neonates. Finally, we review studies that have evaluated the use of NIRS as a transfusion guide during neonatal intensive care.

Evaluation of inter-rater and test-retest reliability for near-infrared spectroscopy reactive hyperemia measures

BACKGROUND

Near-infrared spectroscopy (NIRS) is a non-invasive tool used to measure blood flow in peripheral tissues. More information on inter-rater agreement and test-retest reliability of NIRS-based reperfusion assessments is needed.

PURPOSE

To assess inter-rater agreement for NIRS based data analysis, and evaluate the measurement's reliability across days.

METHODS

On three separate days (average days between visits 1 and 3: 19.4 ± 6.9 days), participants' (N = 15 males, 22 ± 2 yr.) post-occlusion reactive hyperemia (PORH) was measured in the left gastrocnemius muscle using Continuous-Wave NIRS (CW-NIRS). A blood pressure cuff was placed proximal to the knee and inflated to occlude lower leg blood flow for 5 min. The following CW-NIRS parameters were selected: (1) percent saturation in HbO₂ (StO₂%) at baseline; (2) the O₂Hb range used to normalize the NIRS signal; (3) the time for the O₂Hb signal to reach 50 % peak post-occlusion hyperemia (T_1/2), and (4) the post peak hyperemic O₂Hb recovery slope (O₂REC-SLP). Absolute agreement between the two analysts was calculated using two-way random effects Intraclass Correlation Coefficients (ICC_2,1). Consistency between analysts and across days was calculated using two-way mixed models (ICC_3,1). Mean and 95 % confidence intervals (CI) of ICCs are reported. Coefficient of variation (CV) and standard error of the measurement (SEM) are reported.

RESULTS

The ICC_2,1 data indicated "adequate" to "excellent" absolute agreement between the two NIRS analysts. ICC_2,3 data indicated "adequate" to "good" reliability across visits. The CV and SEM for rater 1 and rater 2 across visit were StO₂ (CV: 3.79 % ± 2.71 % and 4.50 % ± 2.37 %; SEM: 3.42 and 3.82), O₂Hb range (CV: 10.50 ± 5.93 and 12.79 ± 12.41; SEM: 3.26 and 4.71), T_1/2 (CV: 11.15 % ± 5.52 % and 10.96 % ± 4.50; SEM: 1.22 and 1.11), and O₂REC-SLP (CV: 19.49 % ± 9.99 % and 18.45 % ± 9.48 %; SEM: 0.04 and 0.04).

CONCLUSION

It is concluded that NIRS parameters assessed show adequate reliability between analysts and across three visits. It is recommended, when feasible and because of the absence of 100 % reliability, that investigators employ more than one rater for scoring at least a portion of the data across each trial in a study's control condition in order to have the ability to estimate the magnitude of error attributable to imperfect reliability.

Newer indications for neuromonitoring in critically ill neonates

Continuous neuromonitoring in the neonatal intensive care unit allows for bedside assessment of brain oxygenation and perfusion as well as cerebral function and seizure identification. Near-infrared spectroscopy (NIRS) reflects the balance between oxygen delivery and consumption, and use of multisite monitoring of regional oxygenation provides organ-specific assessment of perfusion. With understanding of the underlying principles of NIRS as well as the physiologic factors which impact oxygenation and perfusion of the brain, kidneys and bowel, changes in neonatal physiology can be more easily recognized by bedside providers, allowing for appropriate, targeted interventions. Amplitude-integrated electroencephalography (aEEG) allows continuous bedside evaluation of cerebral background activity patterns indicative of the level of cerebral function as well as identification of seizure activity. Normal background patterns are reassuring while abnormal background patterns indicate abnormal brain function. Combining brain monitoring information together with continuous vital sign monitoring (blood pressure, pulse oximetry, heart rate and temperature) at the bedside may be described as multi-modality monitoring and facilitates understanding of physiology. We describe 10 cases in critically ill neonates that demonstrate how comprehensive multimodal monitoring provided greater recognition of the hemodynamic status and its impact on cerebral oxygenation and cerebral function thereby informing treatment decisions. We anticipate that there are numerous other uses of NIRS as well as NIRS in conjunction with aEEG which are yet to be reported.

pFOE or pFTOE as an Early Marker for Impaired Peripheral Microcirculation in Neonates

Background: Peripheral-muscle-fractional-oxygen-extraction (pFOE) and peripheral-muscle-fractional-tissue-oxygen-extraction (pFTOE) are often equated, since both parameters are measured with near-infrared-spectroscopy (NIRS) and estimate oxygen extraction in the tissue. The aim was to investigate the comparability of both parameters and their potential regarding detection of impaired microcirculation. Methods: Term and preterm neonates with NIRS measurements of upper (UE) and lower extremities (LE) were included. pFOE was calculated out of peripheral-muscle-mixed-venous-saturation (pSvO₂), measured with NIRS and venous occlusion, and arterial oxygen saturation (SpO₂). pFTOE was calculated out of peripheral-muscle-tissue-oxygen-saturation and SpO₂. Both parameters were compared using Wilcoxon-Signed-Rank-test and Bland–Altman plots. Results: 341 NIRS measurements were included. pFOE was significantly higher than pFTOE in both locations. Bland–Altman plots revealed limited comparability, especially with increasing oxygen extraction with higher values of pFOE compared to pFTOE. Conclusion: The higher pFOE compared to pFTOE suggests a higher potential of pFOE to detect impaired microcirculation, especially when oxygen extraction is elevated.

Peripheral fractional oxygen extraction measured with near-infrared spectroscopy in neonates-A systematic qualitative review

BACKGROUND

Peripheral fractional oxygen extraction (pFOE) measured with near-infrared spectroscopy (NIRS) in combination with venous occlusion is of increasing interest in term and preterm neonates.

OBJECTIVE

The aim was to perform a systematic qualitative review of literature on the clinical use of pFOE in term and preterm neonates and on the changes in pFOE values over time.

METHODS

A systematic search of PubMed, Embase and Medline was performed using following terms: newborn, infant, neonate, preterm, term, near-infrared spectroscopy, NIRS, oximetry, spectroscopy, tissue, muscle, peripheral, arm, calf, pFOE, OE, oxygen extraction, fractional oxygen extraction, peripheral perfusion and peripheral oxygenation. Additional articles were identified by manual search of cited references. Only studies in human neonates were included.

RESULTS

Nineteen studies were identified describing pFOE measured with NIRS in combination with venous occlusion. Nine studies described pFOE measured on the forearm and calf at different time points after birth, both in stable preterm and term neonates without medical/respiratory support or any pathological findings. Nine studies described pFOE measured at different time points in sick preterm and term neonates presenting with signs of infection/inflammation, anemia, arterial hypotension, patent ductus arteriosus, asphyxia or prenatal tobacco exposure. One study described pFOE both, in neonates with and without pathological findings.

CONCLUSION

This systematic review demonstrates that pFOE may provide additional insight into peripheral perfusion and oxygenation, as well as into disturbances of microcirculation caused by centralization in preterm and term neonates with different pathological findings.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021249235].

Fetal Hemoglobin and Tissue Oxygenation Measured With Near-Infrared Spectroscopy-A Systematic Qualitative Review

Fetal hemoglobin (HbF) is a principal oxygen carrier in the blood of preterm and term neonates. Compared to adult hemoglobin, it has a significantly higher affinity for oxygen and its oxyhemoglobin dissociation curve (ODC) is left-shifted accordingly. Tissue oxygenation measured with near-infrared spectroscopy (NIRS) during neonatal intensive care is directly affected by hemoglobin concentration. We performed a systematic qualitative review regarding the impact of HbF on tissue oxygenation monitoring by NIRS. The PubMed/Medline, EMBASE, Cochrane library and CINAHL databases were searched from inception to May 2021 for studies relating to HbF and NIRS in preterm and term neonates in the first days and weeks after birth. Out of 1,429 eligible records, four observational studies were included. Three studies found no effect of HbF on cerebral tissue oxygenation. One peripheral NIRS study found a positive correlation between HbF and peripheral fractional oxygen extraction (FOE). Currently available limited data suggest that FHbF could affect peripheral muscle FOE, but seems not to affect cerebral oxygenation in preterm neonates. More studies are needed to draw a final conclusion on this matter, especially concerning the oxygenation changes driven by adult RBC transfusions.

Evolution of Muscular Oxygenation during a Walking Test in Preterm Children

OBJECTIVE

To explore measures of peripheral muscular oxygenation, coupled to gait characteristics, between preterm and full-term children during a 6-minute walking test (6MWT).

STUDY DESIGN

Prepubescent children performed a 6MWT. During the test, changes in muscular oxyhemoglobin, deoxyhemoglobin, and total hemoglobin were measured with Near-infrared spectroscopy technology, positioned on subjects' calves. Gait variables were monitored with the OptoGait system.

RESULTS

Forty-five children (33 full-term children and 12 preterm children, mean age, 4.9 ± 0.7 and 4.6 ± 0.9 years, respectively) participated in this study. Statistical analysis highlighted a decreased walking performance for preterm children, with significantly lower walking distance (P < .05) than children born full-term (405.1 ± 91.8 m vs 461.0 ± 73.3 m respectively; -9%). A concomitant increase of oxygen extraction (over the time course of Variation of desoxyhemoglobin) was observed from the third minute of the test (P < .05). No statistically significant difference was found for other near-infrared spectroscopy measures. Finally, the analysis of gait variables highlighted a group effect for walking speed (P < .05) and stride length (P < .01).

CONCLUSIONS

Premature children showed decreased walking performance and greater change in peripheral muscular oxygen extraction, associated with slower walking speed and stride length. This may point to a muscular maladjustment and reduced functional capacities for children born preterm. These phenomena could be responsible for greater muscular fatigue.

Evaluation of the rectal-interdigital temperature gradient as a diagnostic marker of shock in dogs

OBJECTIVE

To evaluate the difference in the rectal-interdigital temperature gradient (RITG) between dogs that were presented to an emergency room with clinical signs of shock compared to those without signs of shock, and if this gradient can be used as a diagnostic marker for shock.

DESIGN

Prospective, single center, observational study conducted from 2014 to 2015.

SETTING

University veterinary teaching hospital.

ANIMALS

Twenty dogs with a clinical diagnosis of shock and 60 dogs without a clinical diagnosis of shock (controls).

MEASUREMENTS AND MAIN RESULTS

Upon presentation to the emergency room and prior to intervention, measurements of rectal temperature, interdigital temperature, ambient temperature, systemic markers of perfusion (capillary refill time [CRT], heart rate [HR], respiratory rate [RR], Doppler blood pressure [DBP], and venous plasma lactate concentration), and venous blood gas analytes were recorded. Dogs were initially determined to be in shock by the attending clinician, and post hoc inclusion criteria were applied. Shock was defined as abnormalities in ≥3 of the 6 following criteria: HR > 120/min, RR > 40/min, CRT > 2 seconds, rectal temperature <37.8°C (100.0°F), venous plasma lactate concentration >2.5 mmol/L, or DBP < 90 mm Hg. Animals with circulatory shock had a significantly increased RITG. An increased RITG was also correlated with individual perfusion parameters including prolonged CRT (ρ = .353, P = 0.0013), tachycardia (ρ = .3485, P = 0.0015), decreased DBP (ρ = -0.6162, P = 0.0003), and shock index (ρ = 0.6168, P = 0.0003). Receiver operator curve analysis indicated a RITG cutoff point of 11.6°F had 90% specificity for the diagnosis of shock (area under the curve = 0.7604).

CONCLUSIONS

The RITG in this study was associated with a diagnosis of shock and therefore may serve as a diagnostic marker of circulatory shock. Future studies with larger sample sizes to validate the use of temperature gradients and other peripheral perfusion abnormalities as diagnostic and monitoring tools are warranted.

Changes in peripheral muscle oxygenation measured with near-infrared spectroscopy in preterm neonates within the first 24 h after birth

BACKGROUND

Near-infrared spectroscopy (NIRS) combined with venous occlusions enables peripheral-muscle oxygenation and perfusion monitoring.

OBJECTIVE

The aim of the present exploratory observational study was to evaluate peripheral-muscle oxygenation and perfusion during the first 24 h after birth in stable preterm neonates.

APPROACH

Secondary outcome parameters of prospective observational studies were analysed. Preterm neonates with peripheral-muscle NIRS measurements combined with venous occlusion on the first day after birth were included. Neonates without circulatory support and without signs of infection/inflammation were included. Neonates were stratified in four groups according to their measurement time-point (6 h-periods) and matched 2:1 for gestational age ±1 week. For each group haemoglobin flow (Hbflow), oxygen-delivery (DO2), oxygen-consumption (VO2), fractional-oxygen-extraction (FOE), tissue-oxygenation-index (TOI) and mixed-venous-oxygenation (SvO2) were calculated. Neonates with measurements during the first 6-hour time period were compared to neonates with measurements of the following time periods.

MAIN RESULTS

40 preterm neonates (gestational age (median(IQR)): 33.5(32.5-34.1)weeks) measured during the first 6 h period after birth were compared to 20 preterm neonates measured in each of the following 6 h periods (period two: 33.7(33.1-34.3)weeks; period three: 34.1(33.2-34.6)weeks; period four: 33.8(32.6-34.6)weeks). Hbflow, DO2 and SvO2 were significantly higher in the second and third 6 h time period compared to the first 6 h period. VO2 did not change significantly during the first day after birth. FOE was significantly lower in the second, third and fourth time period compared to the first 6 h period. TOI showed a non-significant trend towards higher values in the third period compared to the first 6 h period.

SIGNIFICANCE

In preterm neonates Hbflow, DO2, SvO2 increased, FOE decreased and TOI showed a trend towards increase during the first day after birth, whereas VO2 did not change. Changes of peripheral-muscle oxygenation during the first day after birth in stable preterm neonates are different to already published changes thereafter.

Cerebral and peripheral tissue oxygenation in stable neonates: Absent influence of cardiac function

Aim

Cardiac function is a major factor for tissue perfusion and therefore may affect the tissue oxygen saturation. Aim was to analyse possible associations between cardiac function parameters and cerebral and peripheral tissue oxygenation in neonates on the first day after birth.

Methods

For the present study, we analysed secondary outcome parameters of a previously performed prospective single centre observational study. The prospective study was conducted at the Medical University of Graz, Austria between September 2011 and June 2013. We included preterm and term neonates who were admitted to the neonatal intensive care unit and in whom simultaneous near‐infrared spectroscopy measurements and echocardiography were obtained on the first day after birth. Cardiac function parameters were correlated to cerebral and peripheral tissue oxygen saturation and cerebral and peripheral fractional tissue oxygen extraction at the time of echocardiography.

Results

A total of 60 neonates of whom 47 were preterm and 13 were term (median gestational age: 34; IQR 33‐35 weeks, mean birth weight: 2276 ± 774 grams) were included. There were no statistically significant correlations between cardiac function parameters and regional tissue oxygenation parameters.

Conclusion

In the present study, we found no correlation between regional tissue oxygenation and parameters of cardiac function in cardio‐circulatory stable neonates on the first day after birth.

Cerebral and peripheral muscle oxygenation and perfusion: Course in moderate and late preterm neonates during the first day after birth

Aim

To investigate the ratio of cerebral tissue oxygenation index (cTOI) to peripheral muscle tissue oxygenation index (pTOI) measured by near-infrared spectroscopy (NIRS) in cardio-circulatory stable preterm neonates without signs of inflammation/infection on the first day after birth.

Methods

Observational study analysing secondary outcome parameters of the 'Avoiding Hypotension in Preterm Neonates (AHIP)' trial (ClinicalTrials.gov identifier: NCT01910467). Preterm neonates, who had cTOI and pTOI measurements during 24 h after birth, were included. In each neonate the mean of the cTOI/pTOI-ratio, cTOI, pTOI and routine monitoring parameters were calculated for each hour and for the 24-h measuring period. Courses of all measured parameters were analysed.

Results

Eighty-seven stable preterm neonates (33.1 [32.1-34.1] weeks of gestation) were included. The mean value over the 24-h measuring period for the cTOI/pTOI-ratio was 0.96 ± 0.02, for cTOI 70.1 ± 1.4 and for pTOI 73.4 ± 0.9. Routine monitoring parameters were in the normal ranges over 24 h. The courses of the cTOI/pTOI-ratio and cTOI showed significantly lower values from hour 5 to 15 compared to the first hours after birth. Heart rate decreased significantly over time, whereas mean arterial blood pressure increased significantly. pTOI, arterial oxygen saturation and body temperature showed no significant change over time.

Conclusion

We are the first to report on cTOI/pTOI-ratios for cardio-circulatory stable preterm neonates over a 24-h period after birth, showing significantly lower values from hour 5 to 15 compared to the first hours after birth.

Near-Infrared Spectroscopy in Adult Circulatory Shock: A Systematic Review

BACKGROUND

Circulatory shock affects every third patient in intensive care units and is associated with high mortality. Near-infrared spectroscopy (NIRS) could serve as a means for monitoring tissue perfusion in circulatory shock.

PURPOSE

To assess the evidence of NIRS monitoring in circulatory shock, we conducted a systematic review of the literature.

METHODS

The study protocol was registered in International Prospective Register of Systematic Reviews (PROSPERO). We searched PubMed, Ovid MEDLINE, Scopus, and EBM Reviews databases. The reference lists of included articles, last volumes of key journals, and NIRS monitor manufacturers' webpages were searched manually. Two reviewers independently selected included studies. The quality of studies was assessed. The qualitative synthesis was guided by 3 questions: First, does NIRS monitoring improve patient-centered outcomes in adult circulatory shock patient? Second, do NIRS-derived parameters predict patient-centered outcomes, such as mortality and organ dysfunction, and third, does NIRS monitoring give additional information to guide treatment decisions?

MAIN RESULTS

Eighteen observational studies with 927 patients were included. Because of considerable clinical heterogeneity of the data, we were not able to perform a meta-analysis. Also, due to lack of randomized controlled trials, the first review question could not be answered. Based on the current review, baseline tissue oxygen saturation (StO2) however seems to predict mortality and identify patients with most severe forms of circulatory shock.

CONCLUSIONS

Near-infrared spectroscopy-derived StO2 can predict mortality in circulatory shock, but high-quality data on the impact of NIRS monitoring are lacking. Furthermore, the marked heterogeneity of the studies makes combining the results of individual studies difficult. Standardization of methodology and clinical randomized trials are needed before wider clinical use.

Avoiding Arterial Hypotension in Preterm Neonates (AHIP)-A Single Center Randomised Controlled Study Investigating Simultaneous Near Infrared Spectroscopy Measurements of Cerebral and Peripheral Regional Tissue Oxygenation and Dedicated Interventions

INTRODUCTION

Up to 50% of preterm infants admitted to intensive care units require cardiocirculatory support. The aim of the present study was to assess whether simultaneous monitoring of cerebral tissue oxygenation index (cTOI) and peripheral tissue oxygenation index (pTOI) using near-infrared spectroscopy (NIRS) in combination with dedicated intervention guidelines may help avoiding arterial hypotension and catecholamine administration in preterm neonates.

STUDY DESIGN

Preterm neonates <37 weeks of gestation were included in a single center randomized controlled study. Blood pressure was measured non-invasively or invasively. In the NIRS group, simultaneous cTOI and pTOI monitoring was used starting within 6 h after birth for 24 h to calculate changes in cTOI/pTOI ratio over time. Depending on these changes, interventions including echocardiography, administration of volume or patent ductus arteriosus treatment were performed. In the control group, only routine monitoring and treatment were performed and NIRS signals were not visible. The primary outcome was burden of hypotension within 48 h after initiation of NIRS monitoring.

RESULTS

49 preterm neonates were included in each group: NIRS group 33.1 (32.0-34.0) (median: 25-75 centile) weeks of gestation and control group 33.4 (32.3-34.3) weeks of gestation. In the NIRS group, echocardiography was performed in 17 preterm neonates due to NIRS measurements, whereby six neonates received further treatment. Percentage of neonates with any hypotensive episode during the 48-h observational period was 32.6% in the NIRS group and 44.9% in the control group (p = 0.214). Burden of hypotension (i.e., %mmHg of mean arterial pressure < gestational age) was 0.0 (0.0-2.1) mmHg h in the NIRS group and 0.4 (0.0-3.3) mmHg h in the control group (p = 0.313), with observed burden of hypotension being low in both groups. No severe adverse reactions were observed.

CONCLUSION

In preterm neonates using simultaneous peripheral and cerebral NIRS measurements for early detection of centralization followed by predefined interventions led to a non-significant reduction in burden of arterial hypotension.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier: NCT01910467.

How to assess hemodynamic status in very preterm newborns in the first week of life?

BACKGROUND

Assessing hemodynamic status in preterm newborns is an essential task, as many studies have shown increased morbidity when hemodynamic parameters are abnormal. Although oscillometric monitoring of arterial blood pressure (BP) is widely used due to its simplicity and lack of side effects, these values are not always correlated with microcirculation and oxygen delivery.

OBJECTIVES

This review focuses on different tools for the assessment of hemodynamic status in preterm newborns. These include the measurement of clinical (BP, capillary refill time and urinary output (UO)) or biological parameters (lactate analysis), functional echocardiography, and near-infrared spectroscopy (NIRS). We describe the concepts and techniques involved in these tools in detail, and examine the interest and limitations of each type of assessment.

CONCLUSIONS

This review highlights the complementarities between the different parameters used to assess hemodynamic status in preterm newborns during the first week of life. The analysis of arterial BP measured by oscillometric monitoring must take into account other clinical data, in particular capillary refill time and UO, and biological data such as lactate levels. Echocardiography improves noninvasive hemodynamic management in newborns but requires specific training. In contrast, NIRS may be useful in monitoring the clinical course of infants at risk of, or presenting with, hypotension. It holds the potential for early and noninvasive identification of silent hypoperfusion in critically ill preterm infants. However, more data are needed to confirm the usefulness of this promising tool in significantly changing the outcome of these infants.