Cerebral oxygen saturation and tissue hemoglobin concentration as predictive markers of early postoperative outcomes after pediatric cardiac surgery.

BACKGROUND: Near-infrared spectroscopy (NIRS) provides an assessment of cerebral oxygenation and tissue hemoglobin concentration. AIM: The aim of this study was to investigate whether the cerebral oxygenation and hemoglobin concentration measured with NIRS could predict outcomes after pediatric cardiac surgery. METHOD: We conducted a retrospective observational study in 399 patients who underwent pediatric cardiac surgery. Associations were determined between postoperative outcome and preoperative and postoperative cerebral tissue oxygenation index (TOI), postoperative normalized tissue hemoglobin index (nTHI), concentration changes in oxygenated hemoglobin (Δ[HbO2 ]) and deoxygenated hemoglobin (Δ[HHb]). RESULTS: Thirty-nine children had major postoperative morbidity and 12 died. Using Spearman's correlation analysis, postoperative lower TOI and higher Δ[HHb] were associated with longer stays in the Intensive Care Unit (ICU) (r = -0.48, P < 0.001, r = 0.31, P < 0.001, respectively) and longer duration of intubation (r = -0.48, P < 0.001, r = 0.31, P < 0.001, respectively) and higher probability of death determined by the Risk Adjusted Classification for Congenital Heart Surgery (RACHS-1) (r = -0.39, P < 0.001, r = 0.23, P < 0.001, respectively). In multivariate regression analysis, postoperative TOI was independently associated with major morbidity and mortality and Δ[HHb] was independently associated with major morbidity. In receiver operating characteristic analysis, postoperative TOI and Δ[HHb] predicted major morbidity (Area under the curve [AUC] = 0.72, 0.68, respectively) and mortality (AUC = 0.81, 0.69, respectively). CONCLUSION: Lower TOI or higher [HHb] at the end of surgery and higher RACHS-1 category predicted worse outcomes.

A pilot study to determine whether visually evoked hemodynamic responses are preserved in children during inhalational anesthesia.

BACKGROUND: Anesthetic depth is an important parameter to monitor during surgery, yet remains difficult to quantify, particularly in young children where developmental changes influence the electroencephalogram. A more fundamental physiological response to stimulation is the increase in cerebral blood flow secondary to increased metabolic demand, referred to as flow-metabolism coupling (FMC) and measurable using near-infrared spectroscopy (NIRS). Little is known about the effect of anesthesia on FMC; therefore, we studied visually evoked hemodynamic responses (VEHRs) using NIRS in children undergoing general anesthesia for minor surgical procedures. METHOD: We recruited 23 children (aged 2-5 years), undergoing surgery requiring general anesthesia. VEHRs were measured for 30 min using NIRS, including 5 min of baseline recording after anesthetic induction. Parameters recorded using NIRS included the concentrations of oxygenated (oxy), deoxygenated (deoxy), and total hemoglobin (Hb), which were separated into epochs for evoked response analysis after filtration of motion artifact and baseline drift. Goodness-of-fit statistics and classification rules were used to determine the existence of evoked responses, and a modified Gaussian equation was used to model each evoked response. RESULTS: Near-infrared spectroscopy data were recorded in 20/23 children, of whom nine showed a VEHR. No responses were seen in the baseline control data. When examining the relationship between VEHR and anesthetic agents, we noted that for 8/10 patients in whom preoperative or intraoperative fentanyl were administered and VEHRs were absent. CONCLUSION: We have shown that VEHRs can be detected using NIRS in some anesthetized children. Administration of fentanyl was associated with an absence of VEHRs. The mechanism underlying this association is unclear.

Integrated Oxygenator FX05.

In recent years, there has been a trend to incorporate arterial filters into cardiopulmonary bypass (CPB) oxygenators. The FX oxygenators are the first examples of integrating a filter around the fibers of the oxygenator. To assess the efficacy of the FX05 oxygenator, in comparison with our existing CPB setup (RX05 oxygenator + arterial filter), we randomly assigned 40 patients undergoing CPB, with calculated flows <1.5 L/min, to FX05 or RX05 + arterial filter (19 FX and 21 RX). Embolic load was assessed using the emboli detection and classification quantifier, with sensors placed prefilter and postfilter/oxygenator at identical distances for both devices. A total of 6,270 FX readings and 6,183 RX readings were obtained. Because of the extremely skewed nature of the data, the prefilter embolic volumes were divided into deciles, and each decile was analyzed separately. Our results show that the devices perform similarly; both filter out a high percentage of the prefilter embolic load. Our data support that in the clinical setting, the FX05 is as effective at removing emboli as the RX05 with an arterial filter (CXAF02) which, in conjunction with the prime volume reduction and circuit simplification, has warranted our conversion to the FX series of oxygenators.