Cerebral Fractional Tissue Oxygen Extraction Research Articles

Cerebral tissue oxygenation index, cardiac output and superior vena cava flow in infants with birth weight less than 1250 grams in the first 48 hours of life

BackgroundNear-infrared spectroscopy is a non-invasive method of assessing cerebral oxygenation. Functional echocardiography is increasingly used by neonatologists in the assessment of cardiovascular function. AimsTo correlate cerebral tissue oxygenation index (cTOI) and cardiac output in infants less than 1250g at 6, 12, 24 and 48hours of age. Study designA prospective observational study. SubjectsNewborns with birth weight<1250g. Outcome measuresSerial assessments of superior vena cava (SVC) flow, right and left ventricular outputs, ductus arteriosus and cTOI were performed at 6, 12, 24 and 48hours of age. Clinical parameters, including mean blood pressure, mean airway pressure, blood gas parameters and oxygen saturations were recorded. Results22 neonates were enrolled following parental consent. The mean birth weight was 851g (SD±201), mean gestational age was 25.9weeks (SD±1.7). Mean SVC flow at 6hours of age was 56.8ml/kg/min and increased to 68.6ml/kg/min at 48hours of age. 9 infants (41%) had at least one measurement of low SVC flow (<41ml/kg/min) in the first 48hours. Mean cTOI was 65.2% at 6hours of age, 63.9% at 12hours of age, 68.8% at 24hours of age and 67.2% at 48hours of age. Cerebral fractional tissue oxygen extraction values were highest at 12hours (0.31±0.09). There was no correlation between SVC flow and cTOI values. ConclusionSVC flow, left and right ventricular output increased during first 48hours of life. cTOI decreased at 12hours of age with a concomitant increase in fractionated oxygen extraction. These changes reflect transitional changes in both cardiac and cerebral hemodynamics in extremely low gestational age newborns during the first 48hours.

Volume Expansion Does Not Alter Cerebral Tissue Oxygen Extraction in Preterm Infants with Clinical Signs of Poor Perfusion

Background: Preterm infants with signs of poor perfusion are often treated with volume expansion, although evidence regarding its effect on cerebral perfusion is lacking. Moreover, the effect is questionable in preterm infants with an adequate cerebrovascular autoregulation (CAR). A useful measure to assess perfusion is cerebral fractional tissue oxygen extraction (cFTOE). Objectives: To assess the effect of volume expansion on cFTOE in preterm infants with signs of poor perfusion. Methods: In this observational study, we assessed cFTOE using near-infrared spectroscopy in preterm infants with signs of poor perfusion before, during and 1 h after volume expansion treatment. Simultaneously, we measured mean arterial blood pressure (MABP). We tested the effect of volume expansion on both cFTOE and MABP, using multi-level analyses. We intended to define a subgroup that responded to volume expansion with an increase in blood pressure and a decrease in cFTOE, suggesting absent CAR. Results: In 14 preterm infants, with a median gestational age of 26.7 weeks (25.0-28.7 weeks) and a median birth weight of 836 g (615-1,290 g), we found a small increase in MABP during (1.4 ± 1.4 mm Hg, p = 0.003) and after (1.8 ± 1.7 mm Hg, p = 0.001) volume expansion, but no change in cFTOE during (-0.19 ± 0.1% p = 0.44) or after (-0.53 ± 0.1% p = 0.34) volume expansion. We were unable to define a subgroup lacking CAR. Conclusions: Cerebral perfusion, as assessed by cFTOE, does not improve in preterm infants with signs of poor perfusion following volume expansion. In these infants, either CAR is present or volume expansion is inadequate to affect cFTOE.

Cerebral and Peripheral Regional Oxygen Saturation during Postnatal Transition in Preterm Neonates

To evaluate peripheral regional oxygen saturation (rpSO₂) and cerebral regional oxygen saturation (rcSO₂) during the immediate postnatal transition in late preterm infants with and without the need for respiratory support. This was a prospective observational study using near-infrared spectroscopy to evaluate changes in rpSO₂ and rcSO₂. These variables were measured during the first 15 minutes of life after elective cesarean delivery. Peripheral oxygen saturation (SpO₂) and heart rate were measured continuously by pulse oximetry, and cerebral fractional tissue oxygen extraction (cFTOE) was calculated. Two groups were compared based on their need for respiratory support: a respiratory support group and a normal transition group. Positive-pressure ventilation was delivered with a T-piece resuscitator, and oxygen was adjusted based on SpO₂ values. A Florian respiratory function monitor was used to record the ventilation variables. There were 21 infants in the normal transition group and 21 infants in the respiratory support group. Changes in heart rate over time were similar in the 2 groups. SpO₂, rcSO₂, and rpSO₂ values were consistently higher in the normal transition group. In the respiratory support group, cFTOE values remained significantly elevated for a longer period. This systematic analysis of rpSO₂, rcSO₂, and cFTOE in late preterm infants found significantly lower oxygen saturation values in infants who received respiratory support compared with a normal transition group. We hypothesize that the elevated cFTOE values in the respiratory support group represent compensation for lower oxygen delivery.

Near-Infrared Spectroscopy for Objectifying Cerebral Effects of Laser Acupuncture in Term and Preterm Neonates

Laser acupuncture (LA) becomes more and more relevant in neonates and infants. With near-infrared spectroscopy (NIRS), a continuous and noninvasive measurement of tissue oxygenation is possible. Aim was to investigate, whether the application of LA was associated with any changes in regional cerebral oxygen saturation (rcSO2) in term and preterm neonates. The study included 20 neonates (12 males, 8 females). The Large Intestine 4 acupuncture point (LI 4, Hegu) was stimulated by a microlaser needle (10 mW, 685 nm laser needle EG GmbH, Germany) for 5 minutes, bilaterally. All neonates underwent polygraphic recording during undisturbed daytime sleep, including heart rate (HR), peripheral oxygen saturation (SpO2), and measurement of nasal flow. Using NIRS, rcSO2 was measured continuously. Cerebral fractional tissue oxygen extraction (cFTOE) was calculated. We did not observe any significant changes in SpO2 and HR values during the whole observation period. However, there was a significant decrease in rcSO2 (P = 0.003) within postintervention period, accompanied by a significant increase in cFTOE (P = 0.010) in postintervention period.

Cerebral Oxygenation, Extraction, and Autoregulation in Very Preterm Infants Who Develop Peri-Intraventricular Hemorrhage

To test the hypothesis that near-infrared spectroscopy (NIRS)-determined patterns of regional cerebral oxygen saturation (rScO2), cerebral fractional tissue oxygen extraction (cFTOE), and autoregulatory ability can identify neonates at risk for developing peri-intraventricular hemorrhage (PIVH). This case-control study is a subanalysis of 30 neonates who developed PIVH >12 hours after admission as part of a lager prospective observational cohort study comprising 650 preterm neonates born at ≤32 weeks' gestational age. PIVH was diagnosed by cranial ultrasound, performed at least once daily. Mean arterial blood pressure (MABP), NIRS-determined rScO2, cFTOE, and MABP-rScO2 correlation were monitored from birth to 72 hours of age. Infants with PIVH received more inotropic drugs before being diagnosed with PIVH. Significantly more infants with severe PIVH needed treatment for patent ductus arteriosus. The MABP-rScO2 correlation was >0.5 significantly more often before mild/moderate PIVH and after severe PIVH compared with controls. rScO2 was higher and cFTOE lower in infants before severe PIVH. NIRS-monitored rScO2 and cFTOE suggest cerebral hyperperfusion in infants with severe PIVH. Moreover, MABP-rScO2 correlation indicates more blood pressure-passive brain perfusion in infants with PIVH. Continuous assessment of patterns of cerebral oxygenation and arterial blood pressure may identify those preterm infants at risk for severe PIVH and prompt consideration of preventive measures.

Volatile isoflurane sedation in cerebrovascular intensive care patients using AnaConDa®: effects on cerebral oxygenation, circulation, and pressure

The anesthetic-conserving device AnaConDa(®), a miniature vaporizer, allows volatile sedation in the intensive care unit (ICU). We investigated the effects of isoflurane sedation on cerebral and systemic physiology parameters in neuromonitored ICU stroke patients. Included in the study were 19 consecutive ventilated patients with intracerebral hemorrhage (12), subarachnoid hemorrhage (4), and ischemic stroke (3) who were switched from intravenous propofol or midazolam to inhalative isoflurane sedation for an average of 3.5 days. During the sedation transition, the following parameters were assessed: mean arterial pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), middle cerebral artery mean flow velocity (MFV) and cerebral fractional tissue oxygen extraction (FTOE), as well as systemic cardiopulmonary parameters and administered drugs. After the first hour, mean ICP showed an increase of 2.1 mmHg that was not clinically relevant. Likewise, MFV did not change. MAP and CPP, however, decreased by 6.5 and 6.3 mmHg, respectively. FTOE was reduced slightly from 0.24 to 0.21 (p = 0.03). Over an observation period of 12 h, ICP remained stable, while MAP and thus CPP showed distinct decreases (CPP: -10 mmHg at 6 h, p < 0.001; -7.5 mmHg at 12 h, p = 0.005, when compared to preswitch levels) despite a 1.5-fold increase in vasopressor administration. We suggest that that it is possible to reach sufficient sedation levels in cerebrovascular ICU patients by applying volatile isoflurane long-term without a relevant increase in ICP, if baseline ICP values are low or only moderately elevated. However, caution should be exercised in view of isoflurane's decreasing effect on MAP and CPP. Multimodal neuromonitoring is strongly recommended when applying this off-label sedation method.

109 Neonatal Cerebral Oxygenation is Associated with Neurodevelopmental Outcome of Preterm Infants at 2 to 3 Years of Age

Background and aimsDisturbed cerebral oxygenation during the neonatal period might pose preterm infants at risk for neurological deficits. Our aim was to determine whether regional cerebral tissue oxygen saturation (rcSO2)...

787 What is the Effect PDA and Its Medical Closure on Cerebral and Abdominal Tissue Oxygenation in Preterm Newborns?

Background and AimPatent ductus arteriosus (PDA) is a frequent problem in preterms known to have significant effects on organ perfusion. The aim of this study was to investigate the difference...

Umbilical Cord Milking Stabilizes Cerebral Oxygenation and Perfusion in Infants Born before 29 Weeks of Gestation

To investigate the effects of umbilical cord milking at birth on cerebral perfusion and systemic perfusion in very low birth weight (VLBW) infants. Cerebral tissue oxygenation index and cerebral fractional tissue oxygen extraction were monitored in 50 stable VLBW infants (gestational age <29 weeks, birth weight <1250 g), with 26 allocated to the milked group and 24 to the control group. We used near-infrared spectroscopy 3-6, 12, 18, 24, 36, 48, and 72 hours after birth. Left ventricular end-diastolic dimension, left ventricular ejection fraction, left ventricle (LV) Tei index (measurement of left ventricular systolic and diastolic function), left ventricular cardiac output, and superior vena cava flow were measured concurrently using echocardiography. There were no significant differences in gestational age and birth weight between the 2 groups. Hematocrit, left ventricular end-diastolic dimension, left ventricular cardiac output, and superior vena cava flow were higher in the milked group than in the control group, with improvement in the LV Tei index despite the absence of left ventricular ejection fraction changes within 24 hours after birth. Tissue oxygenation index increased and cerebral fractional tissue oxygen extraction decreased in the milked group within 24 hours after birth. Umbilical cord milking stabilized cerebral oxygenation and perfusion in VLBW infants by improving LV diastolic function by increasing LV preload.

Regional cerebral oxygen saturation in newborn infants in the first 15 min of life after vaginal delivery

The objective of this study was to evaluate regional oxygen saturation of the brain during immediate transition after birth, and to correlate it with pre-ductal arterial oxygen saturation in newborn infants. The prospective observational study including newborn infants in the first 15 min after spontaneous vaginal delivery and uncomplicated transitional period was undertaken. Regional cerebral oxygen saturation (rSO2brain) was measured using near-infrared spectroscopy. Arterial oxygen saturation (SpO2) and heart rate (HR) were measured on the right wrist by pulse oximetry. rSO2brain, SpO2 and HR measurements were started immediately after birth and were performed in the first 15 min of life. Cerebral fractional tissue oxygen extraction (FTOE) was calculated for each minute. Of 145 newborn infants, 16 were included and the gender allocation was 31 females (49.2%) and 32 males (50.8%). rSO2brain increased rapidly from 39% (2 min) to 69% (5 min), SpO2 increased from 72% (2 min) to 96% (14 min) and FTOE showed a significant decrease from minute 2 (0.47) until minute 4 (0.30) and an increase between 8 to 13 min. rSO2brain increased rapidly after vaginal delivery. Although SpO2 increased within the first 14 min after delivery, rSO2brain showed no further significant changes after 5 min. FTOE decreased in the first 4 min and reached standard values subsequently.

Cerebral Tissue Oxygen Extraction as an Additional Early Indicator of Fatal Circulatory Failure in Preterm Infants with Sepsis or NEC

Background: Current diagnostic possibilities are insufficient to detect low systemic blood flow in preterm infants. Near-infrared spectroscopy (NIRS) is a non-invasive method by which fractional cerebral tissue oxygen extraction (FTOEc), an indicator of cerebral perfusion, is calculated.Objective: To determine the prognostic value of FTOEc in addition to clinical signs of circulatory failure in the prediction of mortality in preterm infants with sepsis/NEC.Design/methods: Preterm infants with culture-proven sepsis or NEC were included. Mean values of FTOEc and a circulatory failure score (CFS) were calculated for each infant for every 12hr-period in the 36hrs following clinical presentation. The CFS was composed of five indicators of circulatory failure: tachycardia, hypotension, metabolic acidosis, raised serum lactate, and oliguria. It could range from 0-5 (no to all indicators present). The prognostic value of FTOEc as well as CFS for the prediction of mortality was determined using ROC-analyses and likelihood ratios (LR).Results: Twenty infants were included; eleven had sepsis, nine had NEC. Gestational age was 28.0 weeks median [range:25.0-35.0], birthweight 1155 grams [560-2690], postnatal age 15 days (0-72). Four infants died, all within 31hrs of clinical presentation. CFS≥2 was not a significant predictor of mortality at any timepoint. FTOEc≥0.37 was, with the highest predictive value after 24hrs (LR+:12.0 (95%CI 1.6-36)). The combination of FTOEc≥0.37 and CFS≥2 led to a better prediction of mortality in the first 12hrs after onset than both indicators separately.Conclusion: Adding FTOEc-monitoring to current diagnostic possibilities improves the early prediction of fatal circulatory failure in preterm infants with sepsis/NEC.

Cerebral Fractional Tissue Oxygen Extraction in Infants with Aortic Coarctation

Introduction: infants with aortic coarctation may have altered cerebral perfusion. With Near-infrared Spectroscopy (NIRS), cerebral tissue oxygen extraction (FTOE) is calculated. FTOE reflects cerebral perfusion. Objective: To determine the course of FTOE in the first 48 hours (hrs) of admission in infants with aortic coarctation and to relate this course to short-term outcome. Methods: We included all infants with aortic coarctation and circulatory failure admitted to the NICU of the UMCG in 2009-2010 in whom NIRS-monitoring was performed. Mean values of FTOE were calculated every 12hrs over 2hr-periods. Adverse outcome was defined as need for emergency surgery or death. Results: We included seven infants. Median gestational age was 37.3 weeks (range:31.7-39.6), birth weight: 3340 grams (1345-3910), postnatal age: 10 days (1-18), lactate at admission: 6.7 mmol/l (2.5-19.8). Two infants had an adverse outcome within 36hrs after admission; one needed emergency surgery, one died. infants with adverse outcome showed a high and continuously increasing FTOE over 36hrs while infants with favourable outcome showed a lower and stabilizing FTOE (Table). Conclusion: infants with aortic coarctation show a high FTOE during the first 48hrs of admission, which indicates compromised cerebral perfusion possibly due to circulatory failure. Increasing FTOE over the first 36hrs of admission might indicate adverse short-term outcome. [Course of FTOE in infants with aortic coarctation]

The Relationship Between Electrocerebral Activity and Cerebral Fractional Tissue Oxygen Extraction in Preterm Infants

Impaired cerebral oxygen delivery may cause cerebral damage in preterm infants. At lower levels of cerebral perfusion and oxygen concentration, electrocerebral activity is disturbed. The balance between cerebral oxygen delivery and oxygen use can be measured by near-infrared spectroscopy (NIRS), and electrocerebral activity can be measured by amplitude-integrated EEG (aEEG). Our aim was to determine the relationship between regional cerebral tissue oxygen saturation (rcSO2), fractional tissue oxygen extraction (FTOE), and aEEG. We recorded longitudinal digital aEEG and rcSO2 prospectively in 46 preterm infants (mean GA 29.5 wk, SD 1.7) for 2 hr on the 1st to 5th, 8th, and 15th d after birth. We excluded infants with germinal matrix hemorrhage exceeding grade I and recordings of infants receiving inotropes. FTOE was calculated using transcutaneous arterial oxygen saturation (tcSaO2) and rcSO2 values: (tcSaO2 - rcSO2)/tcSaO2. aEEG was assessed by calculating the mean values of the 5th, 50th, and 95th centiles of the aEEG amplitudes. The aEEG amplitude centiles changed with increasing GA. FTOE and aEEG amplitude centiles increased significantly with postnatal age. More mature electrocerebral activity was accompanied by increased FTOE. FTOE also increased with increasing postnatal age and decreasing Hb levels.

Partial exchange transfusion results in increased cerebral oxygenation and faster peripheral microcirculation in newborns with polycythemia

The aim of this study was to assess cerebral and peripheral oxygenation, by using near infrared spectroscopy (NIRS) and microcirculation by using side stream dark field (SDF) imaging in newborns with polycythemia before and after partial exchange transfusion (PET) therapy to investigate treatment effect on tissue oxygenation and microcirculation. Polycythemic newborns with venous haematocrit (Htc) >70% or ≥65% with symptoms were included. NIRS measurements for cerebral and peripheral oxygenation and SDF recordings for microcirculatory flow assessment were obtained before and after PET. Fractional tissue oxygen extraction (FTOE) was calculated based on tissue oxygenation index and oxygen saturation. Wilcoxon test was used for statistical analysis. Fifteen newborns were included. Cerebral tissue oxygenation index, microvascular flow index and % of vessels with hyperdynamic flow increased after PET; median (range): 61.27 (51.36-61.87) versus 64.54 (54.1-74.38), 2.74 (2.46-3) versus 3.22 (2.64-3.75) and 0 (0-2.8) versus 3 (0-99.3), respectively. Whereas cerebral fractional tissue oxygen extraction (CFTOE), % of vessels with sluggish flow decreased after treatment; 0.36 (0.22-0.44) versus 0.31 (0.17-0.46), 1.4 (0-69) versus 0 (0-0.9), respectively. Peripheral oxygenation was unchanged. Partial exchange transfusion improves microcirculation in polycythemic newborns. Cerebral oxygenation increases and cFTOE decreases suggesting increased blood flow. Microvascular flow increases possibly representing reactive hyperperfusion after hemodilution. Whether these effects are beneficial require further research.

Prenatal tobacco exposure influences cerebral oxygenation in preterm infants

Aim Our aim was to determine the influence of prenatal tobacco exposure on regional cerebral tissue oxygen saturation (r cSO 2) and fractional tissue oxygen extraction (FTOE) in preterm infants. We hypothesized that as a result of vasoconstriction caused by prenatal tobacco exposure r cSO 2 would be lower and FTOE would be higher during the first days after birth in infants exposed to tobacco during pregnancy. Methods Sixty preterms were included in this prospective, observational cohort study (median gestational age 29.9 weeks, range 26.0–31.8, median birth weight 1248 g, range 615–2250). Fourteen infants had been exposed to tobacco during pregnancy. All mothers smoked more than five cigarettes a day till delivery. We measured r cSO 2 and transcutaneous arterial oxygen saturation (tcSaO 2) in all infants on days 1–5, 8, and 15. FTOE was calculated: FTOE = (tcSaO 2 − r cSO 2) / tcSaO 2. Results In preterm infants exposed to tobacco during pregnancy, r cSO 2 was lower during days 1, 2, and 8 after birth, median 73% versus 81%, 73% versus 80% and 71% versus 78% respectively. FTOE was higher during days 1 and 8 after birth, median 0.24 versus 0.15 and 0.26 versus 0.19 respectively. On the second day, FTOE tended to be higher, 0.18 versus 0.14. Conclusions During the first two days and day 8 after birth cerebral oxygen saturation is lower and oxygen extraction higher in preterm infants following prenatal tobacco exposure. Our data suggest that prenatal tobacco exposure may have an effect on cerebral oxygenation of the infant.

51 Effect of Volume Expansion on Cerebral Blood Flow in Hypotensive Preterms

Background and aims: To ensure adequate perfusion of the brain, cerebral autoregulation limits cerebral blood flow (CBF) to a certain range. Preterm infants might lack autoregulation, and when hypotensive, be at risk for cerebral damage. Frequently used treatment for hypotension is volume expansion. We aimed to determine the effect of volume expansion (crystalloid) in hypotensive preterms on fractional cerebral tissue oxygen extraction (FTOE), a measure for CBF. Methods: Preterm infants with a mean arterial blood pressure (MABP) below their GA, who received volume expansion (15 ml/kg) within the first week of life, were included. Near-infrared spectroscopy was used to measure regional cerebral oxygen saturation (rcSO2). Transcutaneous arterial oxygen saturation (tcSaO2) was measured simultaneously. FTOE was calculated: (tcSaO2-rcSO2)/tcSaO2. We analyzed 2 episodes of 1h immediately before, and 2 hours after treatment, using Mann-Whitney-U-test. Results: Twelve measurements in 10 preterms (7 female, median GA 27.9 weeks (range 25.6-31.3), BW 1064 grams (676-1780), 1.7 days old (0.5-6.9), CRIB-score 4 (1-9)) were analyzed. MABP increased in 10 cases (median 29.5 to 32.0 mmHg), though not significantly (p=.21). FTOE did not change accordingly (median 0.26 to 0.24, p=1.0). Conclusions: Volume expansion tends to increase MABP but has no effect on FTOE. However, FTOE before volume expansion was always within the normal range. The question arises whether volume expansion is warranted in preterm infants in case of marginally low blood pressure. Due to the lack of effect on MABP and limited numbers investigated, no conclusion regarding cerebral autoregulation can be drawn.

221 Impact of Balloon Atrial Septostomy on Cerebral Oxygen Saturation and Oxygen Extraction in Neonates with Transposition of the Great Arteries

Background: Neonates with transposition of the great arteries (TGA) are at risk of hypoxic-ischemic brain-injury. Balloon atrial septostomy (BAS) improves mixing of oxygen-saturated and -desaturated blood. We determined the impact of BAS on regional cerebral tissue oxygen saturation (rcSO2) and fractional cerebral tissue oxygen extraction (FTOE) in neonates with TGA.Methods: Term neonates with TGA were included. RcSO2 was measured with near-infrared spectroscopy 2 hours (hrs) before, 2hrs after, and 24hrs after BAS for a two-hour period. Transcutaneous arterial oxygen saturation (tcSaO2) was measured simultaneously. FTOE was calculated: FTOE=(tcSaO2-rcSO2)/tcSaO2. In neonates who did not need BAS on clinical grounds, according to the attending cardiologist, tcSaO2 and rcSO2 were measured twice for a two-hour period: once within 24hrs after admission and once 24hrs later. Data were analysed by multi-level analysis and Mann-Whitney-U-test.Results: Nine neonates (median age: 1 day [range:0-18]) underwent BAS and four neonates (median age: 4 days [range:0-6]) did not. RcSO2 increased after BAS (from mean 37% to 49% to 64% [p=0.000]), as did tcSaO2 (from mean 68% to 81% to 84% [p=0.000]). FTOE decreased after BAS (from mean 0.46 to 0.40 to 0.25 [p=0.000]). Neonates who did not need BAS showed higher baseline rcSO2 and tcSaO2 compared to neonates who did (median 57% vs 35% [p=0.020] and 88% vs 77% [p=0.034], respectively). After BAS, there were no differences between both groups.Conclusion: In neonates with TGA in need of BAS, rcSO2 increased and FTOE decreased following BAS. This suggests improved cerebral oxygenation, which, possibly, protects against hypoxic-ischemic brain-injury.

318 Hypothermia; What Does it Do to Cerebral Oxygenation and Microcirculation?

Background: Hypothermia is becoming a commonly used treatment for newborns with hypoxic ischemic encephalopathy (HIE) with promising results. The cerebral metabolic effects have been studied extensively. However the acute effects on cerebral and peripheral oxygenation, fractional tissue oxygen extraction, and microcirculation still need further research.Methods: Newborns with HIE were cooled for 72 hours. Cerebral, peripheral oxygenation index were measured before, during and after hypothermia by near infrared spectroscopy (NIRS), microcirculation was assessed from axilla by sidestream dark field (SDF) imaging technique during and after hypothermia.Results: We present results of cerebral tissue oxygen index (cTOI) measured by (NIRS) from scalp, calculated cerebral fractional tissue oxygen extraction (cFTOE), microvascular flow index (MFI), % of vessels with sluggish flow measured by (SDF) technique in 5 newborns with HIE who underwent selective head cooling for 72 hours in figure.[Microcirculation and NIRS Data During Hypothermia]cTOI, cFTOE values were similar during hypo and normothermia, however microcirculation was much slower during hypothermia.Discussion: Selective head cooling causes minor effects on cerebral oxygenation measured by NIRS, however the repercussions of its effects on blood flow velocity in capillaries require further research.

345 Comparison of Cerebral Tissue Oxygenation Index and Cardiac Output in Infants with Birth Weight Less Than 1250 Grams

Background and aims: (1) To correlate cerebral tissue oxygenation index (cTOI) and cardiac output measurements in infants with birth weight less than 1250 g during first 48 hours of life. (2) To correlate these measurements with clinical parameters. Methods: A prospective observational study. Newborns with birth weight < 1250g were eligible for enrolment. Superior vena cava (SVC) flow, right and left ventricular outputs were measured. Patent ductus arteriosus was assessed and cTOI was measured. All measurements were done at 6, 12, 24 and 48 hours of age. Various clinical parameters (including mean blood pressure, mean airway pressure, pH, pO2, pCO2, O2 saturations) were also recorded.Results: 10 neonates were enrolled following parental consent. The mean birth weight was 767 g (SD±184), mean gestational age was 25.3 weeks (SD±1.4). Mean SVC flow at 6 hours of age was 59.6 ml/kg/min and increased to 76.2 ml/kg/min at 48 hours of age. Mean cTOI was 64.9% at 6 hours of age, 63.3% at 12 hours of age, 67.5% at 24 hours of age and 67.7% at 48 hours of age. Mean cerebral fractional tissue oxygen extraction (cFTOE) did not change significantly and was 0.28, 0.31, 0.28 and 0.27 at 6, 12, 24 and 48 hours respectively. There was no significant correlation between SVC flow and cTOI.Conclusion: Superior vena cava flow increased during first 48 hours of life. There was a slight increase in cTOI and no change in cFTOE. This may reflect increased cerebral metabolism during the first 48 hrs.

Changes in cerebral perfusion in extremely low birth weight infants during the first 72 hours after birth

Cerebral perfusion and its relation with systemic circulation in extremely LBW (ELBW) infants in the early neonatal period are not well understood. The cerebral tissue oxygenation index (TOI) and cerebral fractional tissue oxygen extraction (FTOE) were monitored in stable 16 ELBW infants (GA <29 wk) using near-infrared spectroscopy (NIRS) at 3-6, 12, 18, 24, 36, 48, and 72 h after birth. The left ventricular end-systolic wall stress (ESWS), left ventricular ejection fraction (LVEF), left ventricular cardiac output (LVCO), and superior vena cava (SVC) flow were also measured simultaneously using echocardiography. The ESWS increased till 18 h and then decreased; LVEF, LVCO, and SVC flow decreased till 12 h and increased thereafter. The TOI decreased till 12 h and correlated with SVC flow; FTOE increased until 12 h and then decreased. These changes in variables of NIRS and echocardiographic measurements contrasted to changes in mean arterial blood pressure (MABP), which showed trends of continuous and gradual increase after birth. We conclude that even stable ELBW infants undergo evident transitional changes in cerebral oxygenation and perfusion in the early postnatal period, which may reflect changes in cardiac function and cardiac output.