不同通气状态对神经外科手术病人胃粘膜pH的影响  

Influence of alveolar ventilation changes on gastric intramucosal pH in neurosurgical patients

作　　者：曹晓莹[1] 梁伟民[1] 谢致[1] 王倩[2] 

机构地区：[1]复旦大学附属华山医院麻醉科,上海市200040 [2]复旦大学附属华山医院临床流行病教研室,上海市200040

出　　处：《中华麻醉学杂志》2003年第7期500-503,共4页Chinese Journal of Anesthesiology

摘　　要：目的 评估临床不同的肺通气状态对胃张力测定变量的影响。方法 16例ASAⅠ～Ⅱ级的神经外科择期手术病人,全麻诱导插管后行机械通气。以潮气量(V_T)7ml/kg为基础值,逐步增加潮气量至10ml/kg,然后即刻恢复7ml/kg。在不同通气状态持续1h时点T_1(V_T=7ml/kg)、T_2(V_T=8ml/kg)、T_3(V_T=9ml/kg)、T_4(V_T=10ml/kg)、T_5(V_T=7ml/kg),分别采集血液动力学指标、胃粘膜内CO_2分压(PgCO_2)、呼气未CO_2分压(P_(ET)CO_2)和动脉血气指标,并计算胃粘膜内pH(pHi)、PgCO_2-PaCO_2间隙(PCO_2gap)和动脉血pH(pHa)-pHi间隙(pHgsp)。结果 在高通气期间(T_2～T_4):PgCO_2显著下降,pHi显著增高(P<0.01),而PCO_2gap无明显变化(P>0.05),血液动力学指标亦无显著变化。在低通气期(T_5):PgCO_2显著升高(P<0.01),pHi显著下降(P<0.01),伴随着MAP的显著增加(P<0.05),PCO_2gap下降(P<0.05)。PgCO_2与PaCO_2有非常显著的相关性,r=0.8616(P<0.01)。结论PgCO_2随PaCO_2平行变化,使计算出的pHi非常依赖于肺通气的变化,而PCO_2gap在过度通气期间不受通气变化的影响,更能反映内脏灌注的确切变化。Objective To assess the influence of changes in alveolar ventilation on gastro-intestinal perfusion measured via a nasogastric tonometer.Methods Sixteen ASA Ⅰ - Ⅱ patients ( 7 male, 9 female) aged 15-67 yr, undergoing elective intracranial operation were included in this study. The patients were premedicated with oral ranitidine 150 mg and intramuscular phenobarbital 0.1 g and atropine 0.5 mg. Anesthesia was induced with midazolam 1-2 mg, fentanyl 2 μg· kg-1 , propofol 1.5-2.0 mg · kg-1 and vecuronium 0.1 mg · kg-1 , and maintained with 0.5%-2.0% isoflurane inhalation and intermittent iv boluses of fentanyl and vecuronium. The patients were intubated and mechanically ventilated after induction of anesthesia. The ventilatory settings were : RR 10 bpm; FGF 1 L· min-1; I: E = 1:2; the initial VT was 7 ml· kg-1 (T1 ) which was gradually increased to 8 ml ·kg-1(T2), 9ml·kg-1(T3) and 10 ml·kg-1 (T4) and then returned to 7 ml · kg-1 again. Each VT was maintained for 1 h. A nasogastric tonometer (Tonocap, Datex-Ohmeda, Finland) was inserted into stomach and automatically measured gastric intramucosal CO2 tension (PgCO2) every 10 min. Radial artery was cannulated for direct MAP monitoring and blood sampling. Blood gas analysis was performed every hour at various VT levels. Gastric-to-arterial pH gap and gastric-to-arterial PCO2 gap [P(g-a)CO2] were calculated.Results PgCO2 decreased during T2_4 (hyperventilation phase) (P<0.01) and pHi increased (P<0.01), but P(g-a)CO2 remained unchanged. Hemodynamic parameters were also unchanged. At T5 (VT = 7 ml · kg-1 ) PgCO2 increased (P < 0.01), pHi decreased (P < 0.01) and P(g-a)CO2 decreased (P < 0.05) as compared with those at T4. There was a significant linear relationship (r - 0.8616, P < 0.01) between PaCO2 and PgCO2. Conclusion The linear relationship between PaCO2 and PgCO2 renders the pHi very dependent on the level of alveolar ventilation. In contrast P(g-a)CO2 is not affected during hyperventilation and can reflect the changes in gastro-intestinal perfusion

关 键 词：神经外科手术 通气状态 胃张力测定 二氧化碳分压 胃粘膜PH值 

分 类 号：R614[医药卫生—麻醉学]