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Cerebral Oxygen Saturation in Children With Congenital Heart Disease and Chronic Hypoxemia
Barry D Kussman1, Peter C Laussen, Paul B Benni
1From the *Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts; †Department of Critical Care Medicine, Hospital for Sick Children, Toronto, Ontario, Canada; ‡CAS Medical Systems Inc, Branford, Connecticut; §Department of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; and ‖Department of Cardiothoracic Surgery, Stanford Medical Center, Palo Alto, California.
Insights
Children with congenital heart disease (CHD) and hypoxemia maintain normal cerebral oxygen saturation (ScO2) despite low hemoglobin (Hb). Reduced Hb can lower ScO2, potentially risking brain injury.
Area of Science:
- Biomedical Engineering
- Pediatric Cardiology
- Neuroscience
Background:
- Congenital heart disease (CHD) can cause hypoxemia, leading to increased hemoglobin (Hb) as a compensatory mechanism.
- Near-infrared spectroscopy (NIRS) monitors cerebral tissue oxygen saturation (ScO2), crucial for assessing oxygen delivery-consumption balance in children with CHD.
- Limited data exist on the relationship between ScO2, arterial oxygen saturation (SaO2), jugular bulb oxygen saturation (SjbO2), Hb, and cerebral oxygen extraction (COE) in pediatric CHD patients.
Purpose of the Study:
- To investigate the associations between NIRS-measured cerebral oxygen saturation (ScO2) and the difference between arterial and cerebral oxygen saturation (ΔSaO2-ScO2) with SaO2 and Hb in children with CHD.
- To verify the normal range of ScO2 in children diagnosed with CHD.
- To explore the interplay of these parameters in relation to cerebral oxygen extraction (COE).
Main Methods:
- A calibration and validation study using the FORE-SIGHT NIRS monitor was conducted on children undergoing cardiac catheterization for CHD.
- Simultaneous arterial and jugular bulb blood samples were collected for co-oximetry to determine reference ScO2 (REF CX) and estimate COE.
- Statistical analyses, including Pearson correlation and linear regression, were employed to examine relationships between oxygen saturation parameters and Hb, stratified by diagnostic group (acyanotic vs. cyanotic).
Main Results:
- In 57 of 65 children (88%), acceptable jugular bulb samples were obtained.
- ΔSaO2-SjbO2, ΔSaO2-ScO2, and ΔSaO2-REF CX showed positive correlations with SaO2 and negative correlations with Hb (P < .001).
- While ScO2 differed statistically between diagnostic groups (P = .002), cyanotic patients exhibited normal ScO2 values (69% ± 6%). COE estimates varied significantly between groups when calculated using saturation differences, but not when using oxygen content differences.
Conclusions:
- Children with compensated chronic hypoxemia due to CHD can maintain ScO2 within normal ranges.
- The inverse relationship between ΔSaO2-ScO2 and Hb suggests that reduced Hb levels, especially with decreased cardiac output, may lead to critically low ScO2, potentially indicating brain injury risk.
Background:
Increased hemoglobin (Hb) concentration accompanying hypoxemia is a compensatory response to maintain tissue oxygen delivery. Near infrared spectroscopy (NIRS) is used clinically to detect abnormalities in the balance of cerebral tissue oxygen delivery and consumption, including in children with congenital heart disease (CHD). Although NIRS-measured cerebral tissue O2 saturation (ScO2) correlates with arterial oxygen saturation (SaO2), jugular bulb O2 saturation (SjbO2), and Hb, little data exist on the interplay between these factors and cerebral O2 extraction (COE). This study investigated the associations of ScO2 and ΔSaO2-ScO2 with SaO2 and Hb and verified the normal range of ScO2 in children with CHD.
Methods:
Children undergoing cardiac catheterization for CHD were enrolled in a calibration and validation study of the FORE-SIGHT NIRS monitor. Two pairs of simultaneous arterial and jugular bulb samples were drawn for co-oximetry, calculation of a reference ScO2 (REF CX), and estimation of COE. Pearson correlation and linear regression were used to determine relationships between O2 saturation parameters and Hb. Data were also analyzed according to diagnostic group defined as acyanotic (SaO2 ≥ 90%) and cyanotic (SaO2 < 90%).
Results:
Of 65 children studied, acceptable jugular bulb samples (SjbO2 absolute difference between samples ≤10%) were obtained in 57 (88%). The ΔSaO2-SjbO2, ΔSaO2-ScO2, and ΔSaO2-REF CX were positively correlated with SaO2 and negatively correlated with Hb (all P < .001). Although by diagnostic group ScO2 differed statistically (P = .002), values in the cyanotic patients were within the range considered normal (69% ± 6%). COE estimated by the difference between arterial and jugular bulb O2 content (ΔCaO2-CjbO2, mL O2/100 mL) was not different for cyanotic and acyanotic patients (P = .10), but estimates using ΔSaO2-SjbO2, ΔSaO2-ScO2, or ΔSaO2-ScO2/SaO2 were significantly different between the cyanotic and acyanotic children (P < .001).
Conclusions:
Children with adequately compensated chronic hypoxemia appear to have ScO2 values within the normal range. The ΔSaO2-ScO2 is inversely related to Hb, with the implication that in the presence of reduced Hb, particularly if coupled with a decreased cardiac output, the ScO2 can fall to values associated with brain injury in laboratory studies.
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