Effect of four different anesthetic techniques on oxygenation and intrapulmonary shunt during prolonged one-lung ventilation
SUN Ying;FENG Yi;YANG Ba-xian Department of Anesthesiology, People's Hospital,Peking University, Beijing 100044, China
Objective To investigate the changes in oxygenation and intrapulmonary shunt during prolonged one-lung ventilation (OLV) and compare the effects of four different anesthetic techniques. Methods Forty ASAⅠ -Ⅱ patients (27 male, 13 female) aged 36-74 yr undergoing prolonged OLV during elective thoracic surgery were randomly allocated to one of four groups: (1) isoflurane (GI, n = 10); (2) isoflurane + epidural (GIE, n =10); (3) propofol (GP, n = 10); (4) propofol + epidural (GPE, n = 10). Radial artery was cannulated and Swan-Ganz catheter was placed via right internal jugular vein before induction of general anesthesia. In group 2 and 4 an epidural catheter was inserted at T_(7-8) or T_(8-9) and advanced 3 .5-4.0 cm in the epidural space cephalad. Epidural block was produced by a bolus of 0.5 % ropivacaine 7-9 ml followed by continuous infusion of 0. 5 % ropivacaine at 3-5 ml·h~(-1). Anesthesia was induced with propofol 1 .0-1. 5 mg·kg~(-1), fentanyl 3μg·kg~(-1) and vecuronium 0. 1 mg·kg~(-1). A left-sided double-lumen tube was inserted and correct position was confirmed. The patients were mechenically ventilated. The ventilation collditions were FiO_2 = 100 %, V_T = 8-10 ml·kg~(-1), I: E = 1: 5 and respiratory rate was adjusted to maintained P_(ET) CO_2 at 35-45 mm Hg during both two-lung ventilation (TLV) and OLV. Anesthesia was maintained with isoflurane inhalation in group 1 and 2 or continuous infusion of propofol in group 3 and 4 supplemented with intermittent i. v. boluses of fentanyl. MAP, HR, ECG, MPAP, CVP, continuous cardiac output (CCO), BIS and TOF were continuously monitored during anesthesia. BIS was maintained at 45-55. Arterial and pulmonary blood gases were analyzed before induction of anesthesia (T_1), 30 min after TLV was started (T_2 ), and 5, 15, 30, 60, 120 and 180 min after OLV was started (T_(3-8)) and 30 min after TLV was resumed (T_9 ). The Qs/Qt (shunt fraction) was calculated at T_(1-9) Results Qs/Qt was significantly increased after induction of general anesthesia and mechanical ventilation and increased further during OLV compared with the baseline value (T_1) in all four groups. The calculated Qs/Qt values were highest at 15 min (T_4) or 30 min (T_5) of OLV and remained high for 30-60 min and then gradually decreasing. During OLV QS/Qt was higher in group 1 than in the other three groups (P0.05). PaO_2 was significantly lower after OLV was started and reached the lowest level at T_(4-6)then was gradually increasing. There was no significant difference in PaO_2 at all time points among the four groups (P0.05). Cardiac output was significantly higher in group 1 and 2 than that in group 3 and 4 during OLV. Conclusion During prolonged OLV intrapulmonary shunt tends to decrease with increasing oxygenation with time, regardless of anesthetic techniques employed. Isoflurane inhalation is associated with a signifficant increase in shunt fraction. Combined general and epidural anesthesia may induce greater hemodynamic changes.
【CateGory Index】： R614