硬膜外阻滞对全麻单肺通气期间肺内分流和氧合的影响

The effect of epidural ropivacaine on arterial oxygenation and intrapulmonary shunt during one-lung ventilation

目的 本研究旨在通过比较全凭静脉麻醉和静脉复合胸部硬膜外麻醉时单肺通气期间肺内分流和动脉氧合的变化,探讨硬膜外麻醉对肺内分流和氧合的影响。方法24例因肺癌或食管癌需单肺通气开胸手术病人,根据麻醉方法的不同随机分为全凭静脉组（GA,n=12,异丙酚/芬太尼/维库溴铵麻醉）和静脉复合硬膜外组（GE,n=12,异丙酚/维库溴胺/胸部硬膜外0.5％罗哌卡因麻醉）。连续监测MAP,MPAP,CO,ECG,HR,SpO2。分别于清醒时、双肺通气30min、单肺通气5,15,30,和60 min、再次双肺通气30 min、抽取动脉、混合静脉血血样,测定血气和肺内分流率（Qs/Qt）。结果 单肺通气后,Qs/Qt进行性增加,至15～30min时达到高峰（分别为GA-33.4％和GE-32.4％）,GA组和GE组各时间点肺内分流差异无显著性。GA组和GE组单肺通气时PaO2较双肺通气明显下降,至 15～30 min时最低（分别为 165.1mm Hg和 168.7 mm Hg）,但两组各时间点PaO2差异无显著性。除GE组平均动脉压轻度降低外,两组心输出量和心率在整个试验中波动不明显。结论 胸部连续硬膜外阻滞不会影响静脉全麻单肺通气期间肺内分流和动脉氧合,可安全有效用于开胸手术。

Objective To determine the effect of of thoracic epidural block on arterial oxygenation and intrapulmonary shunt during one-lung ventilation(OLV).Methods Twenty-four ASA class I - Ⅱ patients undergoing prolonged periods of OLV during elective general thoracic surgery were divided into two groups: general anesthesia group(GA)(n=12) and general anesthesia + epidural block group(GE, n = 12). The patients were premedicated with only scopolamine 0.3mg. Radial artery was cannulated and Swan-Ganz catheter placed via right internal jugular vein under local anesthesia. Epidural block was performed at T7-8or T8-9 and a catheter was inserted and advanced in the epidural space cranially for 3.5-4 cm. General anesthesia was induced with propofol l.5mg·kg-1, fentanyl 3μg·kg-1 and vecuronium 0.1 mg·kg-1. Right or left-sided double-lumen endobronchial tube was placed blindly and the correct position was determined by a combination of unilateral clamping and unclamping and auscultation of the lungs. In GA group anesthesia was maintained with continuous infusion of propofol (150-200 μg·kg-1·min-1 ) and intermittent IV boluses of fentanyl and vecuronium. BIS was maintained at 45-50. In GE group anesthesia was maintained with infusion of propofol(80 - 120 μg·kg-1·min-1 ) and epidural block (a loading dose of 0.5% ropivacaine 7-9ml followed by epidural infusion of 0.5% ropivacaine 3-5 ml·h-1) .The patients were mechanically ventilated. VT = 8-10 ml·kg-1, FiO2 = 1, I: R = 1:1.5 and respiratory rate was adjusted to maintain PET CO2 at 35-45 mm Hg. During OLV the above parameters were maintained. ECG, HR, MAP, MPAP, CVP, continuous cardiac output, BIS and TOP were continuously monitored during operation. Blood samples were taken from radial artery and S-G catheter for blood gas analysis at following intervals: (1) during spontaneous breathing when the patients was a wake (baseline); (2) when the patient was placed in lateral position and the two lungs were being ventilated for 30 min(TLV 30 I) ; (3) 5,15, 30 and 60 minduring the course of OLV; (4) the two lungs were ventilated again for 30 min (TLV 30II) andQs/Qt was calculated. Results Venous admixture increased significantly after induction of anesthesia and during mechanical ventilation and increased further during OLV as compared with the baseline(P<0.01). PaO2 was significantly lower during OLV than that during TLV (P<0.01). But there was no significant difference in Qs/Qt, Co, PAP, MAP at each interval between the two groups. Conclusions Thoracic epidural block with 0.5% ropivacaine does not affect arterial oxygenation and Qs/Qt during OLV. Intravenous propofol infusion combined with epidural 0.5% ropivacaine infusion is a safe technique of anesthesia for general thoracic surgery.