Effect of nitroglycerin and aortic occlusion on myocardial blood flow.

To better characterize the cardiac and peripheral effects of nitroglycerin during aortic occlusion, we measured myocardial blood flow in 43 normal and pentobarbital (PB)-depressed dogs (groups I to VII). PB was continuously infused in groups IV to VII to maintain reduced cardiac output and contractility. In groups VI and VII nitroglycerin was administered at 2 micrograms/kg/min. Sequential injections of radioactive microspheres (10 micrometers) and hemodynamic measurements were performed during 2-hour occlusions of the infrarenal aorta. The hearts were divided into endocardium, midmyocardium, and epicardium; total and regional blood flows and the ratio of endocardial to epicardial blood flow (endo/epi) were calculated. The results (mean +/- SEM) were subjected to analysis of variance. Normal dogs that underwent aortic occlusion had predictable increases in peripheral vascular resistance. Coronary vascular resistance fell (P less than 0.05) and endo/epi ratios were maintained above 1. Following PB administration, the myocardial blood flow uniformly fell (1.08 +/- 0.34 to 0.55 +/-0.09 ml/min/gm, P less than 0.001), and the animals not treated with nitroglycerin demonstrated decreased endo/epi ratios (1.11 +/- 0-.07 to 0.83 +/- 0.08, P less than 0.001). Although nitroglycerin did not prevent decreases in total myocardial blood flow, endo/epi ratios were maintained above 1 in treated animals (group VI, 1.04 +/- 0.08; group VII, 1.18 +/- 0.17). Furthermore, the increases in left ventricular end diastolic pressure in the untreated animals were significantly greater than those in animals receiving nitroglycerin (P less than 0.01). Despite severe cardiac depression, nitroglycerin maintained normal transmural distribution favoring the endocardium. Since coronary and peripheral vascular resistances were not altered, this benefit most probably reflects decreased ventricular wall tension secondary to preload reduction.

Reactive hyperemia vs treadmill exercise testing in arterial disease.

We compared the ankle pressure response during reactive hyperemia to the response to treadmill exercise in 28 limbs of 14 normal individuals and 26 legs of 15 patients with arterial occlusive disease. The mean percent maximum drop in ankle blood pressure during reactive hyperemia in normal limbs, 17% +/- 11% (+/- 1 SD) was significantly less than that of legs with arterial disease, 54% +/- 15% (P less than .001). Abnormal values were recorded in all but three diseased limbs. There was good correlation between the ankle pressure responses to reactive hyperemia and treadmill exercise (r = 0.71, P less than .001). This study suggests that measurement of ankle pressure during reactive hyperemia may be a useful substitute for treadmill testing to determine the functional capacity of the circulation during stress in patients with arterial occlusive disease. Reactive hyperemia testing requires less time and equipment and may be performed in patients who might be at risk or unable to carry out treadmill exercise.

Toward further reducing wound infections in cardiac operations.

BACKGROUND: Serious wound infections such as mediastinitis still occur at a rate of 0.8% to 2.0%, according to the most recently published cardiac operative series. METHODS: Data from careful surveillance for infection have been collected prospectively during a 4.5-year period on 1,717 patients who underwent cardiac operations performed under direct ultraviolet C radiation. RESULTS: The rate for mediastinitis was 0.23%, and for deep incisional infection without mediastinitis, 0.12%; these rates are significantly lower than those for eight of nine of the most recently published cardiac series. When our infection rates were stratified using the National Nosocomial Infection Surveillance risk index, they were also significantly lower in the most important risk categories than the corresponding stratified rates collected from the participating hospitals of the Centers for Disease Control and Prevention National Nosocomial Infection Surveillance system. CONCLUSIONS: Though we lack the proof that only a large, randomized study might provide, certainly, one possible explanation for our lower wound infection rate was the use of bactericidal ultraviolet C radiation during operation. This is a simple and effective means of minimizing operating room airborne bacteria as one possible source of these infections.

Reduction in the morbidity and mortality of major hepatic resection. Experience with 52 patients.

The general surgeon can be expected to encounter patients who require major hepatic resection with increasing frequency. Successful resection of large neoplasms requires meticulous attention to surgical technique. Use of the Lin hepatic compression clamp significantly reduces morbidity and mortality, operative time, and blood loss, and should be employed whenever possible during hepatectomy. In addition, an extended subcostal incision with use of the table-attached Hepco Upper Hand retractor offers superb exposure and avoids the morbidity associated with thoracoabdominal incisions.