Effect Of Different Pulmonary Blood Flow On Inhalational Anesthesia By Sevoflurane For Children With Congenital Heart Disease

Object:1.Pulmonary blood flow is known to influence the pharmacodynamics of volatile anesthetics.This study assessed the efficacy and safety of induction with high concentration sevoflurane and of nasotracheal intubation without a muscle relaxant in infants with increased or decreased pulmonary blood flow and undergoing congenital cardiac surgery.2.The validation of pediatric bispectral index (BIS) sensor when monitoring the sedation of children with different age receving sevoflurane anesthesia was also explored in this research.Methods:1.With ethical committee approved and informed consent,55infants aged2-12months, weighing4.7-10kg, and scheduled for congenital cardiac surgery were enrolled. Subjects were divided into those with increased (IPBF group, n=29) and decreased (DPBF group, n=26) pulmonary blood flow on the bases of chest X-ray findings and intracardiac shunt as revealed by echocardiography. All infants received inhalational induction with8%sevoflurane in100%oxygen at a total fresh gas flow rate of6L/min. Nasotracheal intubation was performed4min after induction. Sevoflurane vaporization was decreased to4%for placement of a peripheral intravenous line and invasive hemodynamic monitors.5min later, sedatives and muscle relaxant were administered and the vaporizer was adjusted to2%for maintenance of anesthesia. During induction, the time to loss of lash and pain reflexes (TL and TP)were observed and Bispectral index system (BIS) scores, circulatory parameters, satisfactory and successful intubation ratios, adverse reactions, and complications of intubation were recorded.2.60children aged from2months to3years old, weighing4.7-16kg scheduled for congenital cardiac surgery were enrolled. They were divided into three age groups:Group A:<6months (n=20); Group B:7-12months (n=20) and Group C:1-3years old (n=20). All the children received the same sevoflurane induction proposal with method1, and the first intubation without muscle relaxant was all successful. Tracheal intubation was performed through nasal route for children weighing less than10kg, and the others use oral routes. The BIS changes were recorded at TL, Tp and8other time points during induction, and they were before anesthesia induction (To),1min,2min,3min and4min after induction (T1-T4) and the moment after tracheal intubation (T5), lmin,3min and5min after intubation (T6-8). The minimum value of BIS before intubation was also observed, and the time point was recorded as Tnadir.Results:1. Times to loss of lash and pain reflexes were longer for the DPBF group (P<0.05). Satisfactory intubation ratios were93.1%and61.5%for the IPBF and DPBF groups, respectively (P<0.05). Successful intubation ratios were96.6%and76.9%for the IPBF and DPBF groups, respectively (P<0.05). Following sevoflurane inhalation, blood pressures decreased significantly in the IPBF group but remained stable in the DPBF group. BIS scores declined to similar stable values, and a "nadir BIS " was recorded in both groups. No obvious adverse reactions or complications of intubation were noted perioperatively.2. At T2, the BIS score in Group A were significantly higher than that in Group B (P<0.05). At T0-1, T3-8, there were no significant difference in BIS score between three groups (P>0.05). Following sevoflurane inhalation, BIS scores first declined to a "nadir BIS" and then increased to similar stable values in three groups. The BIS score at TL were higher than Tp and T1-8in each age group (P<0.05). In Group B, the BIS at Tp were less then that at T1,3.4(P<0.05), but showed no difference with that at T2,5-8(P>0.05). In Group A and C, however, there were no difference between BIS score at TP and that at T1-8(P>0.05).Conclusion:1.Our study demonstrates that induction with high concentration sevoflurane, although faster for infants with IPBF, is safe for infants with either IPBF or DPBF. However, nasotracheal intubation without a muscle relaxant after induction with high concentration sevoflurane is less successful and less satisfactory for infants with DPBF, and therefore, this technique should be used with caution in these infants.2.This study also indicates that the BIS score changes similarly in children with different age stage(<6months,7-12months and1-3years old) after receiving sevoflurane inhalational anesthesia. The good corelation between BIS score and the depth of sedation were found in these children. The pediatric BIS sensor could be applied in children scheduled for cardiac surgeries to evaluate the sedation status.