一种在手术室中为高肺血流量患者降低吸入氧分数的简单方法。

Asakura Ayako, Miyashita Tetsuya, Fujimoto Junichi, Morimura Naoto, Kurahashi Kiyoyasu, Yamada Yoshitsugu

Department of Anesthesiology, Yokohama City University Hospital, Yokohama, Japan.

Paediatr Anaesth. 2007 Dec;17(12):1194-7. doi: 10.1111/j.1460-9592.2007.02317.x.

BACKGROUND

Low inspired oxygen acutely increases pulmonary vascular resistance and decreases pulmonary-systemic blood flow ratio. We present a simple method to lower inspired oxygen fraction (FIO2<0.21) without supplemental nitrogen, during mechanical ventilation by an anesthesia machine.

METHODS

After institutional approval, seven healthy adult volunteers and three infants (0-12 month old) scheduled for congenital heart surgery were enrolled in this study. All the infants were diagnosed with congestive heart failure because of high pulmonary blood flow and were thought to benefit from low FIO2. The volunteers performed spontaneous ventilation (fresh air flow rate=10 l.min(-1), tidal volume=600 ml, frequency=10 br.min(-1)). The infants were mechanically ventilated with air (fresh air flow rate=6 l.min(-1), tidal volume=10 ml.kg(-1), 15<frequency<30 br.min(-1) to adjust PaCO2 between 5.8 kPa and 6.5 kPa (45-50 mmHg), after induction of general anesthesia and tracheal intubation. The fresh gas flow rates were determined by the following formula. Fresh gas flow rate=(FIO2-FEO2) EVE/(0.21+FIO2-FEO2-target FIO2). We recorded FIO2 every 5 min for 30 min. When arterial oxygen saturation decreased >15%, fresh gas flow rates were increased to adjust FIO2 to 0.21.

RESULTS

In all of the seven volunteers and three infants target FIO2 was achieved in <10 min. FIO2 was kept at 0.18+/-0.01 (SD) by calculated fresh air flow rates. In one infant, SpO2 decreased >15% 20 min after lowering FIO2, we had to discontinue this study, and increase fresh gas flow to ventilate the infant with FIO2 0.21. In the other two infants, FIO2 was maintained throughout the study.

CONCLUSIONS

This simple and convenient method to decrease FIO2, has a utility in clinical situations, in which pulmonary vascular resistance is to be increased to improve systemic oxygen delivery in patients with high pulmonary blood flow during cardiac surgery.

背景

低吸入氧可急性增加肺血管阻力并降低肺循环与体循环血流比率。我们介绍一种在麻醉机进行机械通气期间不补充氮气而降低吸入氧分数（FIO2<0.21）的简单方法。

方法

经机构批准后，本研究纳入了7名健康成年志愿者和3名计划进行先天性心脏病手术的婴儿（0至12个月大）。所有婴儿均因肺血流量高而被诊断为充血性心力衰竭，并被认为可从低FIO2中获益。志愿者进行自主通气（新鲜气流速=10 l·min⁻¹，潮气量=600 ml，频率=10次·min⁻¹）。婴儿在全身麻醉诱导和气管插管后用空气进行机械通气（新鲜气流速=6 l·min⁻¹，潮气量=10 ml·kg⁻¹，15<频率<30次·min⁻¹，以将PaCO2调整在5.8 kPa至6.5 kPa（45至50 mmHg）之间）。新鲜气体流速由以下公式确定。新鲜气体流速=(FIO2 - FEO2)EVE/(0.21 + FIO2 - FEO2 -目标FIO2)。我们每5分钟记录一次FIO2，共记录30分钟。当动脉血氧饱和度下降>15%时，增加新鲜气体流速以将FIO2调整至0.21。

结果

在所有7名志愿者和3名婴儿中，均在<10分钟内达到目标FIO2。通过计算的新鲜气流速将FIO2维持在0.18±0.01（标准差）。在一名婴儿中，降低FIO2 20分钟后SpO2下降>15%，我们不得不中止本研究，并增加新鲜气体流速以使婴儿以FIO2 0.21进行通气。在另外两名婴儿中，整个研究期间FIO2均得以维持。