Effects of surgical repair of congenital diaphragmatic hernia on cerebral hemodynamics evaluated by near-infrared spectroscopy.

Background: Cardiorespiratory stabilization is recommended before surgical repair of congenital diaphragmatic hernia (CDH) because surgery may induce a transitory deterioration of chest compliance and gas exchange. It is not known if surgical intervention can affect cerebral circulation and oxygenation.

Aim: The aim of the study was to assess noninvasively, by near-infrared spectroscopy, the possible changes in cerebral hemodynamics and oxygenation associated with surgical repair of CDH.

Subjects: Twenty-five newborns with severe CDH (birth weight, 3057 +/- 354 g; gestational age, 37.8 +/- 1.8 weeks; male/female newborns, 15/10; left/right CDH, 19/6) were sedated, paralyzed, and mechanically ventilated by conventional gentle ventilation and surgically corrected at a median age of 2.7 days (min-max, 2-14 days) after cardiorespiratory stabilization.

Methods: Heart rate (HR [beats per minute]), preductal transcutaneous oxygen saturation (tcSaO2 [%]), carbon dioxide tension (tcPCO2 [Torr]), and mean arterial blood pressure (mm Hg) were continuously monitored. Inspired fractional oxygen concentration (FIO2) was adjusted to maintain and preductal tcSaO2 of greater than 80%, whereas the ventilator's settings were kept unchanged throughout the surgical procedure. Cerebral hemodynamics was assessed by near-infrared spectroscopy (NIRO 300, Hamamatsu Photonics, Japan), recording continuously and noninvasively the relative changes in concentration of oxygenated (DeltaO2Hb [micromol/L]), deoxygenated (DeltaHHb [micromol/L]), and total (DeltatHb [micromol/L]) hemoglobin; the tissue oxygenation index (TOI [%]) was also calculated (TOI = O2Hb/O2Hb + HHb). Total hemoglobin concentration is considered to be representative of cerebral blood volume. Arterial blood gases were also measured at the beginning (T1) and at the end of surgery (T2). For all measurements, results at T1 and at T2, as well as the differences between T1 and T2, have been expressed as means or medians and SDs or 95% confidence intervals or ranges. The differences between T1 and T2 were considered statistically significant for a P value of less than .05 by the Student t test for paired values.

Results: At T1, mean tcSaO2% was 94.1 % (SD, 4.6) with a FIO2 of 0.25 (SD, 0.1); at T2, to obtain similar values of tcSaO2 (93.4%; SD, 4.4), it was necessary to increase the FIO2 to 0.37 (SD, 0.14; P < .001). Mean HR at T1 was 149.5 beats per minute (SD, 9.1) and increased significantly (P < .05) at T2 (165.2 beats per minute; SD, 14.2). Mean arterial blood pressure was 54.7 mm Hg (SD, 7.7) at T1 and did not change appreciably at T2 (55.6 mm Hg; SD, 8.1). Moreover, tcPCO2 did not change significantly during the procedure (mean tcPCO2 = 49.9 Torr [SD, 12.8] at T1 and 57.3 mm Hg [SD, 17.9] at T2). O2Hb and tHb decreased (P < .001 and <.005) and HHb increased (P < .05) significantly during the surgical procedure (mean Delta [SD]: DeltaO2Hb= -10.9 micromol/L [9.7], DeltatHb = -7.5 micromol/L [11.7], and DeltaHHb = -3.5 micromol/L [6.8]). Mean TOI was 70% at T1 (normal values >60%) and decreased significantly at T2 (mean DeltaTOI = -6.1% [SD, 10.6]). In all infants, the greatest changes occurred when the viscera were positioned into the abdomen.

Conclusions: Notwithstanding the initial cardiorespiratory stabilization, surgical repair of CDH was associated with a rise in HR and oxygen requirement and a drop in cerebral tHb and O2Hb, suggesting a reduction in cerebral blood volume and oxygenation. These events were probably due to the combined effects of an increase in right to left shunting (as indicated by the increased oxygen requirement) and a decrease in venous return (possibly due to compression of the inferior vena cava by the viscera positioned into the abdomen). These preliminary results reinforce the importance of achieving a good cardiorespiratory stability before undertaking surgical correction of CDH to minimize the possible interference of the procedure with cerebral circulation and oxygenation.