Morbidity and duration of ICU stay after cardiac surgery. A model for preoperative risk assessment.

Although risk factors for mortality after cardiac surgery have been identified, there is no widely applicable method for readily determining risk of postoperative morbidity based on preoperative severity of illness. The goal of this study was to develop a model for stratifying the risk of serious morbidity after adult cardiac surgery using readily available and objective clinical data. After univariate analysis of risk factors in 3,156 operations, 11 variables were identified as important predictors by logistic regression (LR) analysis and used to construct an additive model to calculate the probability of serious morbidity. Reliable correlation was found between a simplified additive model for clinical use and the LR model. The clinical and logistic models were then tested prospectively in 394 patients and demonstrated a pattern of increasing morbidity with ascending scores similar to that predicted by the reference group. Increasing clinical risk score was also associated with a greater frequency of individual complications as well as prolongation of ICU stay. This study demonstrates that it is feasible to design a simple method to stratify the risk of serious morbidity after adult cardiac surgery. With further prospective multicenter refinement and testing, such a model is likely to be useful for adjusting severity of illness when reporting outcome statistics as well as planning resource utilization.     

Descending Aortic Aneurysmectomy without Adjuncts to Avoid Ischemia

Encouraged by reports on the safety of simple aortic cross-clamping for resection of descending aortic aneurysm, we began utilizing this technique more liberally in 1976. This study was undertaken to examine the results of operation in 36 patients, equally divided into two distinct groups.In Group 1, either extracorporeal circulation or indwelling temporary shunts were employed during the period of aortic occlusion. In Group 2, simple aortic cross-clamping was utilized to manage the lesion. No adjuncts were used to avoid ischemia in the latter group. The only 2 early deaths and two instances of paraplegia occurred in Group 1. In general, there were fewer complications in Group 2, with approximately two-thirds of the patients experiencing an uneventful postoperative course. These differences are considered important since the two groups were similar in respect to the extent and nature of the lesions and other factors contributing to operative risk.     

Coronary revascularization in septuagenarians

Despite a 15 year experience with the aorta-coronary bypass operation, indications for its use remain unsettled, especially in the elderly. Between January, 1974, and June, 1980, 2,667 patients underwent coronary artery revascularization with an overall mortality of 3.8% (101/2,667). During the last 12 months the mortality has decreased to 1%. There were 2,562 patients below the age of 70, with a mortality of 3.5% (90/2,562), in contrast to 105 patients over the age of 70, with a mortality of 10.5% (11/105) (p = 0.002). In patients less than 70 years of age there was a significant difference between the mortality of men, 3.12% (67/2,146), and that of women, 5.53% (23/416) (p = 0.015). This disparity of operative risk was far more pronounced in patients over 70 years of age: men 6% (5/84) and women 28.6% (6/21) (p = 0.002). The overall operative mortality of women, 6.6% (29/437), was significantly different from the overall mortality of men, 3.2% (72/2,230) (p = 0.001). An in depth analysis of past medical history, risk factors, and catheterization data is presented in those patients over the age of 70. The average number of vessels bypassed was 2.40: men 2.47 and women 2.09 (p = NS). The ages varied from 70 to 81 years with a mean of 72.5. Smoking (p = 0.012) and diabetes (p = 0.0078) were significant risk factors for coronary disease. Smoking (p = 0.032) and abnormal pulmonary artery pressures (p = 0.0429) were significant variables affecting mortality. A 97.1% follow-up was obtained up to 78 months. Coronary artery revascularization can be performed in men below the age of 70 with acceptable mortality, but there is a twofold increase above the age of 70. Women can undergo revascularization below the age of 70 with a significantly higher risk than males. Those above the age of 70 are at severe risk and should undergo revascularization only after careful selection.     

Cerebral blood volume in a rat model of ischemia by MR imaging at 4.7 T

Perturbation of the cerebral circulation by occlusion of the vertebral arteries and a carotid artery can be visualized by using MR imaging and the intravascular contrast agent Gd-DTPA complexed to albumin. This tracer consistently reduced the T1 relaxation time in the brain and blood. The difference between hemispheres was revealed by less T1 reduction in the occluded hemisphere and by an adjustment in the display contrast of images that revealed the territory of decreased perfusion. These results were confirmed by comparing them with cerebral blood flow using radioactive microspheres and the intravascular blood volume tracer 51Cr-EDTA. This method, combined with high-resolution MR imaging, can be applied to serial noninvasive studies of cerebral blood volume in ischemia and other conditions.     

Permanent transvenous balloon occlusion of the inferior vena cava: experience with 60 patients.

Traditional operations to obstruct the IVC are often unsatisfactory because the morbidity and mortality is appreciable: poor risk patients do not tolerate surgical and anesthetic trauma. Furthermore, if the patient is anticoagulated, an operation requires that such desirable treatment be stopped. Ten years ago a study was begun to develop a transvenous method of IVC occlusion in the awake anticoagulated patient. Animal studies were done prior to patient application. A technique was evolved wherein IVC interruption could be accomplished with a balloon bearing catheter inserted through the jugular vein. The balloon was positioned with venography and after inflation held in place by lateral pressure in the distensible IVC. The catheter was then removed, leaving the balloon in position. Balloon occlusion has been used in the management of 60 selected patients since 1970. Twenty-nine patients were simultaneously anticoagulated without complication. Very sick patients tolerated the procedure well. No patient experienced further pulmonary emboli. Nine hospital deaths occurred from a variety of causes, none related to the balloon catheter. Late follow-up shows that the occluding balloon gradually deflates in about 12 months. The remnant has remained stable in all patients, contained in a scar that permanently interrupts the IVC.     

The preparation of DTPA-coupled antibodies radiolabeled with metallic radionuclides: an improved method

Isotopes of iodine are often employed as radiolabels for antibodies used in radioimmunodetection studies in which tumor localization is determined by external imaging. Because of drawbacks associated with the use of these isotopes, alternative labeling methods have been considered; such as covalently attaching strong chelators so that the coupled protein may be radiolabeled with metallic radionuclides by chelation. We have developed a method of coupling the strong chelator diethylenetriaminepentaacetic acid (DTPA) which is simple, efficient, and superior to reported methods. Using the cyclic anhydride, coupling to IgG antibody is about 75% efficient and is completed in less than 1 min at neutral pH. Because the concentration of hydrolytic products is small, the coupled protein is rapidly purified for use or storage. Labeling of the protein is also accomplished rapidly and the labeled product has been shown to be stable both in vitro and in vivo.     

Subendocardial myocardial necrosis: a preventable lesion.

Left ventricular subendocardial hemorrhagic necrosis, a lesion entirely different from conventional myocardial infarction, has been an important cause of serious morbidity and mortality in open heart surgery, particularly aortic valve replacement. An established experimental model in which this lesion could be consistently produced in calves, was utilized to examine the protective role of hypothermia and/or Solumedrol infusion. Solumedrol infusion and systemic hypothermia were not sufficiently effective in protecting the myocardium against 40 minutes of left coronary artery occlusion during total cardiopulmonary bypass. Profound continuous irrigation of the pericardial cavity with 4 degrees centigrade Ringers lactate solution, with or without Solumedrol infusion, under similar circumstances yielded excellent results, both in terms of myocardial performance and preservation. This experiment has encouraged the clinical use of this technique in our institution.