Sussmane J B, Totapally B R, Hultquist K, Torbati D, Wolfsdorf J
Miami Children's Hospital, Division of Critical Care Medicine, Miami, FL, USA.
Crit Care Med. 2001 Oct;29(10):1972-8. doi: 10.1097/00003246-200110000-00020.
To evaluate hemodynamic stability and gas exchange in a neonatal animal model of pumpless arteriovenous extracorporeal membrane oxygenation (AV-ECMO) with extracorporeal shunt flow of up to 15% of cardiac output during variable ventilation and oxygenation.
Prospective study.
Research laboratory in a hospital.
Seven lambs (5.5 +/- 0.6 kg, mean +/- sd).
The lambs initially were anesthetized by 50 mg/kg ketamine intravenously. After tracheostomy, the lambs were mechanically ventilated and paralyzed by using 1 mg/kg vecuronium bromide followed by 0.1 mg.kg(-1).hr(-1). One femoral vein was cannulated with a pulmonary artery flotation catheter and used for cardiac output and pulmonary artery pressure measurements. A femoral artery was cannulated for measuring mean arterial blood pressure, measuring heart rate, and blood sampling for gas exchange analyses. Finally, the right internal jugular vein and carotid artery were cannulated and used for the AV-ECMO. Normothermia (38 +/- 0.5 degrees C), fluid balance (5 mL.kg(-1).hr(-1) normal saline), and anesthesia (5 mg.kg(-1).hr(-1), intravenous ketamine) were maintained. Ventilator settings were adjusted to establish a baseline Paco2 (25-35 mm Hg) at an Fio2 of 0.4. The AV-ECMO circuit was established by using a hollow fiber oxygenator, primed with maternal sheep blood (150-200 mL).
The physiologic effects of the AV-ECMO shunt were evaluated at 15, 25, and 40 mL.kg(-1).hr(-1) ECMO flow, corresponding roughly to 4%, 8%, and 15% of the cardiac output values. The baseline minute volume was maintained during stepwise increases in arteriovenous shunt. A significant increase in endogenous cardiac output occurred at arteriovenous shunt of 25 and 40 mL.kg(-1).hr(-1) (analysis of variance followed by Tukey-Kramer multiple comparisons test), which was attributed to a significant increase of 30% in the heart rate. Effective cardiac output (difference between the thermodilution value and the AV-ECMO flow rate) and mean arterial blood pressure were not significantly changed. CO2 removal, measured at 15% arteriovenous shunt, was significantly increased with decreasing ventilation to 25% and 50% of the baseline (analysis of variance and Tukey-Kramer test). Oxygenation through the membrane was measured after reducing inspired Fio2 from 0.4 to 0.21, 0.15, and 0.10 with 15% arteriovenous shunt and baseline minute ventilation. Oxygen delivery by the oxygenator was significantly increased at Fio2 of 0.10, providing a maximum of 19.5% of the total oxygen consumption at an arterial hemoglobin-oxygen saturation of 60%.
Healthy lambs are capable of maintaining effective cardiac output in the presence of moderate arteriovenous shunts (15%). AV-ECMO may provide efficient ventilatory support in the neonatal population with hypercapnia. The amount of oxygen delivery with AV-ECMO depends on arterial desaturation.
评估在可变通气和氧合期间，体外分流流量高达心输出量15%的无泵动静脉体外膜肺氧合（AV-ECMO）新生动物模型中的血流动力学稳定性和气体交换。
前瞻性研究。
医院的研究实验室。
7只羔羊（5.5±0.6千克，均值±标准差）。
羔羊最初通过静脉注射50毫克/千克氯胺酮进行麻醉。气管切开术后，羔羊使用1毫克/千克维库溴铵进行机械通气和麻痹，随后以0.1毫克·千克⁻¹·小时⁻¹的剂量持续给药。一根股静脉插入肺动脉漂浮导管，用于测量心输出量和肺动脉压力。一根股动脉插管用于测量平均动脉血压、心率，并采集血样进行气体交换分析。最后，右颈内静脉和颈动脉插管用于建立AV-ECMO。维持正常体温（38±0.5℃）、液体平衡（5毫升·千克⁻¹·小时⁻¹生理盐水）和麻醉（5毫克·千克⁻¹·小时⁻¹静脉注射氯胺酮）。调整呼吸机设置，在吸入氧分数为0.4时建立基线动脉血二氧化碳分压（Paco2，25 - 35毫米汞柱）。使用中空纤维氧合器建立AV-ECMO回路，并用母羊血液（150 - 200毫升）预充。
在ECMO流量为15、25和40毫升·千克⁻¹·小时⁻¹时评估AV-ECMO分流的生理效应，分别大致对应于心输出量值的4%、8%和15%。在动静脉分流逐步增加期间维持基线分钟通气量。在动静脉分流为25和40毫升·千克⁻¹·小时⁻¹时，内源性心输出量显著增加（方差分析后进行Tukey-Kramer多重比较检验），这归因于心率显著增加30%。有效心输出量（热稀释值与AV-ECMO流速之差）和平均动脉血压无显著变化。在动静脉分流为15%时测量的二氧化碳清除量，随着通气量降至基线的25%和50%而显著增加（方差分析和Tukey-Kramer检验）。在动静脉分流为15%且基线分钟通气量的情况下，将吸入氧分数从0.4降至0.21、0.15和0.10后测量通过膜的氧合情况。在吸入氧分数为0.10时，氧合器的氧输送显著增加，在动脉血红蛋白氧饱和度为60%时，提供的氧最多占总氧消耗的19.5%。
健康羔羊在存在中度动静脉分流（15%）的情况下能够维持有效心输出量。AV-ECMO可为患有高碳酸血症的新生儿群体提供有效的通气支持。AV-ECMO的氧输送量取决于动脉血氧饱和度降低情况。
