Research Of Cerebral Oxygenation In Children With Tetralogy Of Fallot

Objective:To explore the effects of intracardiac shunts direction on cerebral tissue oxygenation index（TOI）in infants with congenital heart disease preoperative.To evaluate the effects of different mechanical ventilation modes on oxygenation and regional cerebral tissue oxygenation index in infants with tetralogy of Fallot（TOF）before cardiopulmonary bypass.Method:Part1 Sixty surgery children who were between 4 to 24 months old and were diagnosed with ventricular septal defect（VSD group）、tetralogy of Fallot（TOF group）and indirect inguinal hernia（control group）were recruited,20 cases in each group.The NIRS cerebral oximeter was used to monitor patients’cerebral oximetry.Two sensors were placed on the subject’s forehead bilaterally for continuous monitoring of cerebral oximetry.Pulse oxygen saturation（SpO₂）,noninvasive blood pressure,heart rate were also measured and recorded.TOI and fractional tissue oxygen extraction（FTOE）were compared among the three groups and multiple linear regression analysis was used to evaluate the relationship between TOI and these parameters.Part2 Fifty-two infants with TOF aged 4～24 months undergoing corrective surgery were grouped as hyperventilation group（H group）,conventional ventilation group（S group）and low tidal volume ventilation group（L group）.After anesthesia introduction,VCV ventilation was used in three groups,while inhaled oxygen concentration（Fi O₂）was set as 0.6.The End-tidal carbon dioxide partial pressure(P_ETCO₂)was maintained in a proper range by regulating the respiratory rate.H group with a tidal volume of 11 ml/kg to keep PaCO₂ at 30 mm Hg.S group with a tidal volume of 9 ml/kg to keep PaCO₂ at 30～45mm Hg.L group with a tidal volume of 7 ml/kg（Predicted body weight）to keep PaCO₂between 35～40 mm Hg.SpO₂、Sc O₂、P_ETCO₂、MAP、HR were recorded before anesthesia（T1）,immediately after intubation（T2）,mechanical ventilation15minutes（T3）,30minutes（T4）.Arterial blood samples were drawn for blood-gas analysis at T3 time points.And the results of blood gas analysis inculding pH、SaO₂、Pa O₂、HCT、PaCO was recorded for further analysis.Results:Part1 There was no significant difference in TOI between the VSD group and control group（P>0.05）.Both sides of TOI in TOF group were significantly lower than those in other two groups（均P<0.001）.In addition,FTOE in TOF group were significantly higher than that in VSD groups（P<0.05）.Multiple linear regression analysis showed that only SpO₂ was related to TOI in infant with congenital heart disease（r=0.607,P=0.000）.Part2 No significant differences were observed considering the changes of MAP,HR and SpO₂ at each time points among the three groups（P>0.05）.At T1,T2 time points,there was no significant differences of TOI among the three groups.At T3,T4 time points,TOI in hyperventilation group was lower compared with that in other two groups.The pH value and PaCO₂ were significantly different among the three groups.The H group had the highest pH value and the lowest PaCO₂.On the contrary,The L group had the lowest p H value and the highest PaCO₂.There were no significant differences of other blood gas analysis results.Conclusion:Part1 Congenital heart disease of different intracardiac shunts direction can affect TOI through systemic oxygenation.Infants with right-to-left shunt physiology have lower TOI and higher FTOE due to low systemic oxygenation.Part2 Compared with conventional ventilation,hyperventilation before cardiopulmonary bypass significantly reduced patient’s TOI and thereby increased the cerebral ischemia risk/,by which increased the risk of ischemia.Furthermore,small tidal volume ventilation does not affect TOF the patient’s oxygenation and TOI.However,PaCO₂ should be monitored closely to prevent the accumulation of PaCO₂.