Failure of blood cardioplegia to protect myocardium at lower temperatures.
Failure of blood cardioplegia to protect myocardium at lower temperatures.
复制标题
血液停跳液在较低温度下无法保护心肌。
作者：
G. J. Magovern;John T. Flaherty;Vincent L. GoTT;Bernadine H. Bulkley;Timothy J. Gardner
为了评估温度的影响，对输注温度为 20 摄氏度、10 摄氏度和 4 摄氏度的含氧血液和晶体心脏停搏液 (CP) 进行了比较。每个 CP 中的钾含量为 25 mEq/l。有六个研究组，每组有七颗犬心脏，所有心脏均在20℃、10℃或4℃下进行90分钟的整体缺血，然后进行45分钟的常温再灌注。缺血期间，每 30 分钟给予血液或晶体 CP。每次输注时，使用质谱法记录心肌氧张力的任何变化，并计算耗氧量（MVO2）。通过使用心室内球囊测量等容压来评估所有心脏缺血前后的左心室（LV）功能。注射 20 摄氏度血液 CP 导致心肌内氧分压 (PO2) 平均增加 7 毫米汞柱。在10°C或4°C时，血CP输注不会导致心肌内PO2显着增加，而使用晶体CP时，心肌内PO2在三种输注温度下均不会增加。每次血液 CP 注射的平均 MVO2（表示为 ml O2/100 g LV 湿重）对于 20 摄氏度血液为 16.5 +/- 0.8，对于 10 摄氏度血液为 4.1 +/- 0.3，对于 4 摄氏度血液为 3.5 +/- 0.4（p 小于 0.001，20 摄氏度血液与 10 摄氏度和 4 摄氏度血液相比）。每次晶体 CP 注射的 MVO2 对于 20 摄氏度 CP 为 0.9 +/- 0.1，对于 10 摄氏度 CP 为 0.8 +/- 0.1，对于 4 摄氏度 CP 为 0.7 +/- 0.1。再灌注 45 分钟后形成的压力恢复（以缺血前控制的百分比表示）为 76.0 +/- 3.4% 或 20 摄氏度血液 CP，10 摄氏度血液 CP 为 65.6 +/- 2.3%，4 摄氏度血液 CP 为 54.0 +/- 2.7%（p 小于 0.05，20 摄氏度血液 CP 与 10 摄氏度和4°C 血液 CP）。形成压力的恢复（也表示为缺血前控制的百分比）对于 20 摄氏度晶体 CP 为 56.6 +/- 1.4%，对于 10 摄氏度晶体 CP 为 72.9 +/- 3.0%，对于 4 摄氏度晶体 CP 为 72.0 +/- 2.3%（p 小于 0.05，20 摄氏度晶体 CP 与 10 摄氏度和 4 摄氏度晶体 CP）。这些数据表明，在 20 摄氏度下输注时，血液 CP 最为有效。使用 10 摄氏度的血液 CP 增强了心肌冷却，但没有额外的好处，可能是因为氧气输送很少。 4°C 时的血液 CP 导致左心室功能的保存明显较差。尽管用晶体 CP 治疗的心脏不使用氧气，但在 4 摄氏度或 10 摄氏度下输注的晶体 CP 与 20 摄氏度的血液 CP 一样有效。
To assess the effect of temperature, oxygenated blood and crystalloid cardioplegic solutions (CPs) at infusion temperatures of 20 degrees C, 10 degrees C and 4 degrees C were compared. The amount of potassium in each CP was 25 mEq/l. There were six study groups with seven canine hearts in each group, all of which were subjected to 90 minutes of global ischemia at 20 degrees C, 10 degrees C or 4 degrees C, followed by 45 minutes of normothermic reperfusion. During ischemia, either blood or crystalloid CP was given every 30 minutes. With each infusion, any change in myocardial oxygen tension was recorded using mass spectrometry, and oxygen consumption (MVO2) was calculated. Left ventricular (LV) function was assessed before and after ischemia in all hearts by measuring isovolumic developed pressure using an intraventricular balloon. Injection of 20 degrees C blood CP resulted in a mean increase in intramyocardial oxygen tension (PO2) of 7 mm Hg. At 10 degrees C or 4 degrees C, blood CP infusions did not cause a significant increase in intramyocardial PO2, while with crystalloid CP, intramyocardial PO2 did not increase at any of the three infusion temperatures. The mean MVO2 with each blood CP injection, expressed as ml O2/100 g LV wet weight, was 16.5 +/- 0.8 for 20 degrees C blood, 4.1 +/- 0.3 for 10 degrees C blood and 3.5 +/- 0.4 for 4 degrees C blood (p less than 0.001, 20 degrees C blood vs 10 degrees C and 4 degrees C blood). MVO2 with each crystalloid CP injection was 0.9 +/- 0.1 for 20 degrees C CP, 0.8 +/- 0.1 for 10 degrees C CP, and 0.7 +/- 0.1 for 4 degrees C CP. Recovery of developed pressure after 45 minutes of reperfusion, expressed as a percentage of preischemic control, was 76.0 +/- 3.4% or 20 degrees C blood CP, 65.6 +/- 2.3% for 10 degrees C blood CP, and 54.0 +/- 2.7% for 4 degrees C blood CP (p less than 0.05, 20 degrees C blood CP vs 10 degrees C and 4 degrees C blood CP). Recovery of developed pressure, also expressed as a percentage of preischemic control, was 56.6 +/- 1.4% for 20 degrees C crystalloid CP, 72.9 +/- 3.0% for 10 degrees C crystalloid CP, and 72.0 +/- 2.3% for 4 degrees C crystalloid CP (p less than 0.05, 20 degrees C crystalloid CP vs 10 degrees C and 4 degrees C crystalloid CP). These data show that blood CP is most effective when infused at 20 degrees C. The use of 10 degrees C blood CP enhanced myocardial cooling, but was of no additional benefit, presumably because there was little oxygen delivery. Blood CP at 4 degrees C resulted in significantly poorer preservation of LV function. Crystalloid CP infused at either 4 degrees C or 10 degrees C was as effective as 20 degrees C blood CP, despite the absence of oxygen use by hearts treated with crystalloid CP.