Warters R D, Allen S J, Davis K L, Geissler H J, Bischoff I, Mutschler E, Mehlhorn U
Center for Microvascular and Lymphatic Studies, Department of Anesthesiology, University of Texas-Houston Medical School, 77030, USA.
Ann Thorac Surg. 1998 Apr;65(4):961-6. doi: 10.1016/s0003-4975(97)01420-3.
As an alternative to cardioplegic arrest, cardiac surgical conditions have been produced using beta-blocker-induced minimal myocardial contraction (MMC) during cardiopulmonary bypass. The technique of MMC involves the use of high-dose intravenous esmolol to suppress myocardial chronotropy and inotropy sufficiently to produce cardiac surgical conditions. The purpose of this study was to compare conventional crystalloid cardioplegic arrest with MMC in terms of ischemia avoidance, myocardial edema formation, and cardiac function.
Twelve dogs were placed on cardiopulmonary bypass. Six dogs were subjected to crystalloid cardioplegic arrest for 2 hours. Surgical conditions were produced in the other 6 dogs for 2 hours using intravenous esmolol without aortic clamping or cardioplegia. Arterial and coronary sinus lactate concentrations were determined as a gauge of myocardial ischemia. Myocardial water content was determined using microgravimetry and preload recruitable stroke work was determined using sonomicrometry and micromanometry.
Significant lactate washout was demonstrated after cardioplegic arrest but not after MMC. Myocardial water content was significantly less during and after MMC compared with cardioplegic arrest (p < 0.05). Preload recruitable stroke work was decreased compared with baseline values in both groups (p < 0.05).
In contrast to a previous study that involved 1 hour of MMC, in this study, ventricular function was decreased to the same extent as with cardioplegic arrest after 2 hours of MMC. This was attributed to the accumulation of ASL-8123, the primary metabolite of esmolol, which possesses beta-antagonist properties. Although postbypass ventricular function is similar in both groups, MMC appears to be superior in terms of ischemia avoidance and myocardial edema formation.
作为心脏停搏的替代方法，在体外循环期间使用β受体阻滞剂诱导的最小心肌收缩（MMC）来创造心脏手术条件。MMC技术涉及使用高剂量静脉注射艾司洛尔来充分抑制心肌变时性和变力性，以创造心脏手术条件。本研究的目的是在避免缺血、心肌水肿形成和心脏功能方面，将传统的晶体心脏停搏与MMC进行比较。
将12只狗置于体外循环。6只狗接受晶体心脏停搏2小时。另外6只狗在不进行主动脉钳夹或心脏停搏的情况下，使用静脉注射艾司洛尔创造手术条件2小时。测定动脉和冠状窦乳酸浓度作为心肌缺血的指标。使用微量重力法测定心肌含水量，使用超声心动图和微测压法测定预负荷可募集的每搏功。
心脏停搏后显示出显著的乳酸清除，但MMC后未显示。与心脏停搏相比，MMC期间及之后心肌含水量显著更低（p < 0.05）。两组的预负荷可募集每搏功均较基线值降低（p < 0.05）。
与之前涉及1小时MMC的研究不同，在本研究中，MMC 2小时后心室功能降低的程度与心脏停搏相同。这归因于艾司洛尔的主要代谢产物ASL-8123的蓄积，其具有β受体拮抗特性。虽然两组体外循环后的心室功能相似，但MMC在避免缺血和心肌水肿形成方面似乎更具优势。
