Early postoperative changes in cerebral oxygen metabolism following neonatal cardiac surgery: Effects of surgical duration

Abstract

Objective The early postoperative period following neonatal cardiac surgery is a time of increased risk for brain injury, yet the mechanisms underlying this risk are unknown. To understand these risks more completely, we quantified changes in postoperative cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF), and cerebral blood flow (CBF) compared with preoperative levels by using noninvasive optical modalities. Methods Diffuse optical spectroscopy and diffuse correlation spectroscopy were used concurrently to derive cerebral blood flow and oxygen utilization postoperatively for 12 hours. Relative changes in CMRO2, OEF, and CBF were quantified with reference to preoperative data. A mixed-effect model was used to investigate the influence of total support time and deep hypothermic circulatory arrest duration on relative changes in CMRO2, OEF, and CBF. Results Relative changes in CMRO2, OEF, and CBF were assessed in 36 patients, 21 with single-ventricle defects and 15 with 2-ventricle defects. Among patients with single-ventricle lesions, deep hypothermic circulatory arrest duration did not affect relative changes in CMRO2, CBF, or OEF (P > .05). Among 2-ventricle patients, total support time was not a significant predictor of relative changes in CMRO2 or CBF (P > .05), although longer total support time was associated significantly with greater increases in relative change of postoperative OEF (P = .008). Conclusions Noninvasive diffuse optical techniques were used to quantify postoperative relative changes in CMRO2, CBF, and OEF for the first time in this observational pilot study. Pilot data suggest that surgical duration does not account for observed variability in the relative change in CMRO2, and that more comprehensive clinical studies using the new technology are feasible and warranted to elucidate these issues further.

Cerebral Oxygen Metabolism in Neonates with Congenital Heart Disease Quantified by MRI and Optics

“…The median (interquartile range) MRI-measured baseline OEF, S v O 2, CBF and CMRO 2 as well as DOS/DCS-measured baseline OEF, StO 2, BFI, CBV and CMRO 2i in the cohort are reported in Table 2 (StO 2 values in 14 babies from the present cohort were published previously in conjunction with a study evaluating postoperative changes in near-infrared spectroscopy parameters 16 ). Note substantial variation across subjects was observed among all measured resting-state variables.…”

“…The study protocol has been described previously 15,16 and the timeline is illustrated in Figure 1. Briefly, once the anesthetized and paralyzed patient was stabilized and baseline DOS measurements were made while obtaining vascular access, patients were brought to the MRI scanner where a second MRI-compatible, noninvasive optical probe was placed on the forehead for continuous DOS/ DCS monitoring.…”

“…These techniques are described in Durduran et al 21 and the specific protocol and measurement details for the present study is detailed in references 15,16 and in Appendix 1. In brief, frequency-domain DOS enables quantification of absolute regional (microvascular) cerebral oxy-and deoxy-hemoglobin concentration (HbO 2 and HbR, respectively, in mmol/L) using photon diffusion theory 21 From this information, total Hb concentra-…”

Non-invasive assessment of cerebral oxygen metabolism following surgery of congenital heart disease

“…Strong linear correlations were also present in a study comparing measurements based on DOS and DCS to magnetic resonance imaging measurements of blood flow and oxygen saturation in the superior sagittal sinus [30]. The new method was employed to evaluate postoperative relative cerebral blood flow, FTOE and CMRO 2 in comparison with preoperative levels [29,30].…”

“…Buckley et al [26][27][28][29] reported results obtained with a new optical method for determination of cerebral oxygen metabolism and regional cerebral blood using near infrared light. The measurements are based on diffuse optical spectroscopy (DOS) for quantification of cerebral tissue oxygen saturation and diffuse correlation spectroscopy (DCS) for monitoring cerebral blood flow.…”