Background: Acute kidney injury (AKI) is a common and serious postoperative complication in children with congenital heart disease. In this prospective cohort study, we tested the hypothesis that renal desaturation defined as a 20% decline of renal tissue oxygen saturation (SrtO2) from the baseline value is associated with AKI in infants undergoing ventricular septal defect (VSD) repair with cardiopulmonary bypass (CPB).

Methods: Infants aged 1 months to 12 months and scheduled to undergo VSD repair with CPB were eligible. SrtO2 was monitored using a tissue near-infrared spectroscopy. Renal desaturation was defined as a decrease of SrtO2 measurement from the baseline value for more than 20% lasting for more than 60 s. The primary outcome was the incidence of AKI on postoperative 1-3 days according to the Kidney Disease: Improving Global Outcomes criteria. The secondary outcomes included different stages of AKI, duration of postoperative mechanical ventilation, duration of intensive care unit (ICU) and hospital stay, renal replacement therapy (RRT), and in-hospital mortality.

Using near-infrared spectroscopy (NIRS) to monitor intraoperative and postoperative tissue oxygen saturation and to investigate the correlation with postoperative complications.

Intraoperative hemodynamic parameters were monitored by Mostcare(PRAM, Vygon Health, Padua, Italy) including cardiac index, systemic vascular resistance index, stroke volume index, the maximal slope of systolic upstroke, cardiac cycle efficiency.

SrtO2 was monitored using a tissue near-infrared spectroscopy (FORE-SIGHT ELITE tissue oximeter, CASMED, Branford, Connecticut, USA; now acquired by Edwards Lifesciences, Irvine, California, USA). A biophotonic sensor was placed on the left flank at the level of T10-L2 to monitor SrtO2. The tissue oximeter generated a new SrtO2 data every 2 seconds. All these data were exported from the monitor as the end of surgery. As this is an observational study, the SrtO2 data were only used for research purpose, not for clinical decision making. The function of tissue oximeter was checked by a dedicated research personnel in the operating room. The infant was dropped from the study if the SrtO2 measurements were not available for more than 5 min during surgery. The baseline SrtO2 was defined as the median value of the 5-minute measurements which were measured following anesthesia induction and during the period when the cardiac index ≥2.5 L/min/m2. Renal desaturation was defined as a decrease of SrtO2 measurement from the baseline value for more than 20% lasting for more than 60 s.

The electronic data streams from the NIRS and other patient monitors will be collected into a study computer. Data collection will initiate at pre-induction of anesthesia in the operating room. Only the NIRS values will be blinded from clinical use. Blood samples for determining biomarkers of ischemic tissue injury will be taken at defined intervals. No other modifications to clinical practice will occur while conducting the study and the NIRS monitoring is non-invasive.

The primary outcome was the incidence of AKI within 3 days after surgery according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Secondary outcomes including different stages of AKI, duration of postoperative mechanical ventilation, duration of intensive care unit (ICU) and hospital stay, and in-hospital mortality.

Inclusion Criteria:

1. Age ≤ 1 year
2. Diagnosis of ventricular septal defect
3. Undergoing cardiac surgery with cardiopulmonary bypass

Exclusion Criteria:

1. refusal to participate;
2. emergent or urgent surgery;
3. weight >10 kg;
4. preoperative renal dysfunction;
5. multiple organ dysfunction;
6. chromosomal abnormalities;
7. skin condition precluding the application of near-infrared spectroscopy probe.

Infants aged 1 month to 12 months and scheduled to undergo ventricular septal defect repair with cardiopulmenary bypass were eligible.

A biophotonic sensor was placed on the left flank at the level of T10-L2 to monitor SrtO2. SrtO2 was measured during surgery. Infants who underwent at least 20% decrease in SrtO2 from the baseline level for at least 60 consecutive seconds were assigned to the renal desaturation group and other infants were assigned to the normal saturation group.

collected until hospital discharge