Paul Keating

Cerebral tissue oxygen saturation and extraction in preterm infants before and after blood transfusion

Objective Preterm infants often need red blood cell (RBC) transfusions. The aim of this study was to determine whether haemoglobin levels before transfusion were associated with regional cerebral tissue oxygen saturation (rcSO2) and fractional tissue oxygen extraction (FTOE) and whether RBC transfusions were associated with rcSO2 and FTOE during the 24-h period thereafter. Design Prospective observational cohort study. Setting Third level neonatal intensive care unit. Patients Thirty-three preterm infants (gestational age 25–34 weeks, birth weight 605–2080 g) were included. Interventions None. Main Outcome Measures RcSO2 was measured during a 1-h period, before, 1 h after and 24 h after a 15 ml/kg RBC transfusion in 3 h. Using rcSO2 and transcutaneous arterial oxygen saturation (tcSaO2) values, FTOE was calculated: FTOE=(tcSaO2−rcSO2)/tcSaO2. Results Forty-seven RBC transfusions were given. RcSO2 and FTOE correlated strongly with haemoglobin before transfusion (r=0.414 and r=−0.462, respectively, p<0.005). TcSaO2 did not correlate with haemoglobin before transfusion. 24 h after transfusion, rcSO2 increased from a weighted mean of 61% to 72% and FTOE decreased from a weighted mean of 0.34 to 0.23. The decrease in FTOE was strongest in the group with haemoglobin below 6.0 mmol/l (97 g/l). The decrease in FTOE was already present 1 h after transfusion and remained unchanged at 24 h after transfusion. Conclusion Following RBC transfusion, cerebral tissue oxygen saturation increases and FTOE decreases. The data suggest that cerebral oxygenation in preterm infants may be at risk when haemoglobin decreases under 6 mmol/l (97 g/l).

Cerebral Oxygenation in Preterm Infants With Germinal Matrix-Intraventricular Hemorrhages

Background and Purpose— Preterm infants are at risk of developing germinal matrix hemorrhages–intraventricular hemorrhages (GMH-IVH). Disturbances in cerebral perfusion are associated with GMH-IVH. Regional cerebral tissue oxygen saturation (rcSO2), measured with near-infrared spectroscopy, and fractional tissue oxygen extraction (FTOE) were calculated to obtain an indication of cerebral perfusion. Our objective was to determine whether rcSO2 and FTOE were associated with GMH-IVH in preterm infants. Methods— This case–control study included 17 preterm infants with Grade I to III GMH-IVH or periventricular hemorrhagic infarction (median gestational age, 29.4 weeks; range, 25.4 to 31.9 weeks; birth weight, 1260 g; range, 850 to 1840 g). Seventeen preterm infants without GMH-IVH, matched for gestational age and birth weight, served as control subjects (gestational age, 29.9 weeks; range, 26.0 to 31.6 weeks; birth weight, 1310 g; range, 730 to 1975 g). RcSO2 and transcutaneous arterial oxygen saturation were measured during 2 hours on Days 1 to 5, 8, and 15 after birth. FTOE was calculated as FTOE=(transcutaneous arterial oxygen saturation−rcSO2)/transcutaneous arterial oxygen saturation. Results— Multilevel analyses showed that rcSO2 was lower and FTOE higher in infants with GMH-IVH on Days 1, 2, 3, 4, 5, 8, and 15. The largest difference occurred on Day 5 with rcSO2 median 64% in infants with GMH-IVH versus 77% in control subjects and FTOE median 0.30 versus 0.17. RcSO2 and FTOE were not affected by the grade of GMH-IVH. Conclusions— Preterm infants with GMH-IVH had lower rcSO2 and higher FTOE during the first 2 weeks after birth irrespective of the grade of GMH-IVH. This suggests that cerebral perfusion is decreased persistently for 2 weeks in infants with GMH-IVH, even in the presence of mild hemorrhages.

Cerebral oxygen saturation and extraction in preterm infants with transient periventricular echodensities.

OBJECTIVE: Our aim was to determine regional cerebral tissue oxygen saturation and fractional tissue oxygen extraction in preterm infants with transient periventricular echodensities. We hypothesized that as a result of reduced cerebral perfusion, regional cerebral tissue oxygen saturation will be lower and fractional tissue oxygen extraction will be higher during the first days after birth. PATIENTS AND METHODS: This was a prospective, observational study of 49 preterm infants (gestational age median: 30.1 weeks [26.0–31.8 weeks]; birth weight median: 1220 g [615–2250 g]). We defined transient periventricular echodensities as echodensities that persisted for >7 days. Regional cerebral tissue oxygen saturation was measured on days 1–5, 8, and 15 after birth. Fractional tissue oxygen extraction was calculated as (transcutaneous arterial oxygen saturation − regional cerebral tissue oxygen saturation)/transcutaneous arterial oxygen saturation. RESULTS: Transient periventricular echodensities were found in 25 of 49 infants. During the first week we found no difference between the 2 groups for cerebral tissue oxygen saturation and fractional tissue oxygen extraction values. On day 15 after birth, cerebral tissue oxygen saturation was lower in preterm infants with transient periventricular echodensities (66%) compared with infants without echodensities (76%) (P = .003). Fractional tissue oxygen extraction in infants with transient periventricular echodensities (0.30) was higher than fractional tissue oxygen extraction in infants without transient periventricular echodensities (0.20) (P < .001). The differences could not be explained by confounding variables. CONCLUSIONS: Persistent transient periventricular echodensities may be associated with increased cerebral oxygen demand after the first week after birth, which is contrary to our hypothesis. Cerebral oxygenation may be involved in the recovery of perinatal white matter damage.

Effect of Indomethacin Infused over 30 Minutes on Cerebral Fractional Tissue Oxygen Extraction in Preterm Newborns with a Patent Ductus Arteriosus

Background: A significant patent ductus arteriosus (PDA) is a common finding in the first days of life and, if persistent, is associated with an increased morbidity and mortality in the preterm newborn. Objectives: Our aim was to investigate, using near-infrared spectroscopy, the effect of indomethacin on the fractional tissue (cerebral) oxygen extraction (FTcOE) in a group of preterm newborns undergoing medical treatment for a PDA. Methods: This is a prospective, observational study. A cohort of 18 preterm newborns (<32 weeks) undergoing treatment for a PDA with indomethacin were monitored continuously for mean arterial blood pressure, arterial oxygen saturation (SpO2) and regional cerebral oxygen saturation (rcSO2). Measurements were started 1 h before and continued for 4 h after the first indomethacin dose. A final measurement (1 h) was made within 24 h of completing the full course. FTcOE = [SpO2 – rcSO2]/SpO2 was then calculated. To analyze the data, we chose to average the measurements over 1-hour periods. Results: There was a significant increase in the FTcOE (0.06, 95% CI 0.04–0.09, p < 0.001) noticeable within the 1st hour after the start of indomethacin administration, which peaked in the 2nd hour (FTcOE increased by 0.08, 95% CI 0.04–0.11, p < 0.001) and lasted for the full 4-hour period measured. Conclusion: Indomethacin, infused over 30 min, significantly increased the FTcOE in the preterm newborn, the effect lasting at least 4 h. This may represent a protective response to the indomethacin-induced reduction in cerebral blood flow demonstrated by others and warrants further investigation.

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.

EFFECT OF INDOMETHACINE INFUSION RATE FOR PATENT DUCTUS ARTERIOSUS ON CEREBRAL OXYGENATION IN PRETERM INFANTS

Background: Indomethacine treatment for patent ductus arteriosus (PDA), might lead to vasoconstriction of cerebral blood vessels and under-perfusion of the brain. A lower infusion rate might prevent this. We aimed to determine the effect of two indomethacine infusion rates on fractional cerebral oxygen extraction (FTOE), which is indicative for cerebral blood flow. Methods: In preterms with PDA, we compared the effect of indomethacine infusion (0.2 mg/kg) in 30 versus 60 minutes, on cerebral oxygenation. Patients in both groups were matched for GA, BW, PDA closure, and postnatal age. 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 6 episodes of 1-h measurements: before, 1h-4h, and 12 hours after treatment, using Mann-Whitney-U-test. Results: Twenty infants (13 girls, median GA 27.0 weeks (range 25.3-28.7), BW 1007 gram (615- 1300), age 3.0 days (2-11)) were included, 10 in each group. No significant differences existed between the groups regarding GA, BW, age, effectiveness of indomethacine, need of surgery, and gender. The first hour after the start of treatment, we found an increase in FTOE of 0.04 in the 30 minutes-infusiongroup, compared to no change in FTOE in the 60-minutes-infusion group (p=.03). No significant differences were found at all other time-points. Conclusion: Higher infusion rate of indomethacine for PDA seems to decrease cerebral blood flow the first hour, compared to lower infusion rate, possibly due to indomethacine induced vasoconstriction. The clinical relevance of this difference needs to be Investigated.