How should clear cardioplegia be administered? A method of rapid arrest with high flow and pressure.

Most of the currently described methods of administering cardioplegia appear to be less than optimal because of low flows utilized and slow cardiac arrest evolving over a period of several minutes. This may account for some reports of suboptimal protection, namely ventricular dysfunction and elevation of cardiac isoenzymes in the blood following operation. A method of pressurized injection of clear cardioplegic solution with immediate cardiac arrest (6 to 4.1 seconds) is described. The technique utilizes a 16 Fr. cannula under a driving pressure of 300 mm Hg, which gives an aortic root pressure of 80 to 105 mm Hg (mean 98 mm Hg). Monitoring of serum glutamic oxaloacetic transaminase (SGOT), creatine kinase (CK) MB, and lactate dehydrogenase (LDH1 and LDH2) isoenzymes was carried out in 200 consecutive cases of aorta-coronary bypass. Myocardial infarct index (MII), calculated from the CK disappearance value, measured a mean of 5.3. Peak value of CK-MB occurred immediately after operation (2 hours) and ranged from 10.2 +/- 2.6 IU for 30 minutes of ischemia to 13.3 +/- 4.2 IU for 61 minutes, gradually decreasing to less than 2 IU in 48 hours. None of the patients required inotropic agents postoperatively and 89.9% had spontaneous re-establishment of normal cardiac beat following coronary reperfusion. The electrocardiogram (ECG) failed to show any detectable myocardial infarction during this period of time. The system satisfactorily protected the heart for up to 70 minutes of ischemia. The total amount of cardioplegic solution used for 60 minutes measured 1,200 +/- 200 ml. Myocardial temperature dropped to 15 degrees C within 12 +/- 4.3 seconds. The method more closely approximates the ideal flows and pressures for the coronary vascular bed and size of the adult human heart.

Pressurized rapid cardioplegia versus administration of exogenous substrate and topical hypothermia.

Five hundred fifty-nine patients undergoing aortocoronary operation were analyzed retrospectively according to the type of myocardial protection implemented during the period of ischemia. In Group 1 (253 patients), a rapid method of hypothermic cardioplegia alone was utilized. In Group 2 (306 patients), slower infusion of the same solution with topical hypothermia was implemented. Cardiac isoenzymes (CPK-MB, LDH1, LDH2, serum glutamic oxaloacetic transaminase [SGOT]) and myocardial infarct index (MII) were measured postoperatively for 48 hours. Immediately after operation, a significant difference was found between Groups 1 and 2 in the CPK-MB isoenzyme mean value levels--12.1 versus 18.6 IU, p less than 0.01--and MII mean values--5.2 versus 8.1, p less than 0.01. CPK-MB variances between subgroups receiving two, three, and four grafts were significantly different in favor of Group 1. Differences were also found in LDH1, LDH2, total lactic dehydrogenase (LDH), and SGOT: Group 2 levels were significantly higher than in Group 1. There were ten intraoperative infarctions in Group 2 and none in Group 1. In 45% of the patients in Group 2, inotropic agents were necessary in the postoperative period versus none in Group 1. Spontaneous cardiac rhythm following ischemia occurred in 89.7% of the patients in group 1 versus 29% in Group 2. A method of pressurized high-flow rapid cardioplegia with intermittent reperfusions alone, seems to provide adequate protection of the myocardium during ischemia over a slower low-flow method of infusion combined with topical hypothermia.

Multichannel 18-test panels: are 60% of panels abnormal by chance?

Current teaching concerning the frequency of abnormal results secondary to chance alone in a multichannel panel is theoretically based on the binomial distribution. However, this distribution can be used only when the probability of an abnormal result (pi) is the same for each test in the panel. In modern-day multichannel testing, pi varies from test to test and most often is less than the usually reported 0.05. On the other hand, a test such as cholesterol may have a pi level as high as 0.55. Theoretically the only distribution that can take this variability into consideration is the Lexis distribution, a form of the binomial distribution that allows for varying pi s. Since no formula is available to calculate this distribution, we wrote a computer program to generate it. We arranged 18-test panels from 203 normal patients in a frequency distribution. This was then compared with the theoretical Lexis and binomial distributions. This analysis showed that although there was a 50% chance of having one abnormality per panel and a 16% chance of having two abnormalities per panel, there was less than 4% chance of having three or more abnormalities per 18-test panel. In addition, most of the abnormalities noted were minor and were thought to be clinically unimportant.