| Anesthesia is one of the key factors influencing lung gas exchangefunction during perioperative period. Atelectasis, which is caused by thedysfunction of respiratory muscles that lead to reduction in functionalresidual volume and gas re-absorption, has been determined to be one of theleading causes in the gas exchange disorder during general anesthesia. In1963, based on experimental and clinical researches, Bendixen et al. putforwarded the hypothesis termed “atelectasis during anesthesia”.Subsequent researches demonstrated that90%of the patients whounderwent general anesthesia tended to develop atelectasis. Pure oxygenventilation during general anesthesia in patients undergoing cardiopulmonary bypass operation leads to a rapid gas absorption, whichresults in early expiratory small airway closure and distal alveolar collapse,contributing to the development of atelectasis, while O2mixed with airventilation is an inhibitor to atelectasis, and for that, pure oxygenventilation has been far less used in general anesthesia of common diseases.As for the patients with congenital heart disease, however, pure oxygenventilation is still used in many hospitals in the patients with fulminatinganoxia such as cyanosis, intracardial shunt and the mixture of systemic andpulmonary circulation etc., while pure oxygen ventilation-inducedatelectasis is often neglected. Is pure oxygen ventilation beneficial orharmful in comparison with O2mixed with air ventilation before CPB then?Is it advisable to completely substitute pure oxygen ventilation with O2mixed with air ventilation during the anesthesia of infant congenital heartdisease surgery? How is the relationship between fractional concentration ofinspired O2（FiO2） and O2saturation of arterial blood and the effect of FiO2on relevant therapy and prognosis? There is still lack of studies in thisregard.Positive end expiratory pressure （PEEP） is one of the traditional modesof assisted ventilation. Some researches reported that recruited lung wouldcollapse again after pure PEEP therapy, while long-term PEEP could impairthe return of blood to heart, leading to a significant V/Q mismatch.Therefore, some researchers believed that pure PEEP application is not areliable way to prevent atelectasis. In this research, we firstly observed theeffects of varying FiO2on gas exchange in children with congenital heart disease during perioperative period, and based on the observation, weinvestigated whether PEEP/low FiO2combination could further improve thepulmonary gas exchange function in these patients.Part Ⅰ: Effects of varying FiO2on pulmonary gas exchangefunction in children with congenital heart disease during perioperativeperiod102patients undergoing cardiac surgical intervention for congenitalheart disease （non-cyanosis） were administered100%O2forpreoxygenation （three minutes） and ventilation by mask （two minutes）.Following intubation these patients were randomly divided into two groupsand ventilated either with50%O2in air （51cases） or100%O2（51cases）before cardiopulmonary bypass. Arterial blood gases were obtained foranalysis before preoxygenation,30min following intubation, entering ICU,after extubation30min and three days post-operation. Subsequently thedata of pH, PaO2, PaCO2and PaO2/FiO2ratio etc. were analyzed. PaO2value in entering ICU and after extubation30min were significantlyimproved in50%O2group than in100%O2group. PaO2/FiO2ratio in50%O2group were more significantly improved at the time points of afterintubation30min, in entering ICU and after extubation30min, comparedwith the100%O2group. The PaCO2value of50%O2group at the timepoint of entering ICU was significantly lower than that of100%O2group.Mechanical ventilation time, ICU staying time and hospitalization time in50%O2group were significantly shortened compared with100%O2group.Part Ⅱ: Effects of PEEP/low FiO2combination on pulmonary gas exchange function in children with congenital heart disease duringperioperative period96patients undergoing cardiac surgical intervention for congenitalheart disease （non-cyanosis） were administered100%O2forpreoxygenation （three minutes） and ventilation by mask （two minutes）.Following intubation these patients were randomly divided into two groupsand ventilated either with50%O2in air （48cases） or100%O2（48cases）before cardiopulmonary bypass. After cardiopulmonary bypass, all thepatients were ventilated with a PEEP of6cmH2O with50%O2. Arterialblood gases were obtained for analysis before preoxygenation,30minfollowing intubation, entering ICU, after extubation30min and three dayspost-operation. Subsequently the data of pH, PaO2, PaCO2and PaO2/FiO2ratio etc. were analyzed. PaO2value in entering ICU and after extubation30min were significantly improved in50%O2+PEEP group than in100%O2+PEEP group, while in comparison with50%O2group, the PaO2value of50%O2+PEEP group in entering ICU was significantly improved.PaO2/FiO2ratio in50%O2+PEEP group were more significantly improvedat the time points of after intubation30min, in entering ICU, afterextubation30min and one day post-operation compared with the100%O2+PEEP group, while in comparison with50%O2group, the PaO2/FiO2ratioof50%O2+PEEP group in entering ICU was significantly improved. ThePaCO2value of50%O2+PEEP group at the time points of after intubation30min, in entering ICU and after extubation30min was significantly lowerthan that of100%O2+PEEP group.Mechanical ventilation time, ICU staying time and hospitalization time in50%O2+PEEP group weresignificantly shortened compared with100%O2+PEEP group, but therewere no statistic significance revealed in comparison with50%O2group.Taken together, in this study, we revealed that in the general anesthesiaof children with congenital heart disease （non-cyanosis）, ventilation oflungs with50%O2significantly improved the pulmonary gas exchangefunction compared with that of100%O2, and in combination with PEEP,the low FiO2ventilation further improved the pulmonary gas exchangefunction in these patients. |
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