Lowest hematocrit on bypass and adverse outcomes associated with coronary artery bypass grafting. Northern New England Cardiovascular Disease Study Group.

BACKGROUND: Cardiac surgery patients' hematocrits frequently fall to low levels during cardiopulmonary bypass. METHODS: We investigated the association between nadir hematocrit and in-hospital mortality and other adverse outcomes in a consecutive series of 6,980 patients undergoing isolated coronary artery bypass graft surgery. The lowest hematocrit during cardiopulmonary bypass was recorded for each patient. Patients were divided into categories based on their lowest hematocrit. Women had a lower hematocrit during bypass than men but both sexes are represented in each category. RESULTS: After adjustment for preoperative differences in patient and disease characteristics, the lowest hematocrit during cardiopulmonary bypass was significantly associated with increased risk of in-hospital mortality, intra- or postoperative placement of an intraaortic balloon pump and return to cardiopulmonary bypass after attempted separation. Smaller patients and those with a lower preoperative hematocrit are at higher risk of having a low hematocrit during cardiopulmonary bypass. CONCLUSIONS: Female patients and patients with smaller body surface area may be more hemodiluted than larger patients. Minimizing intraoperative anemia may result in improved outcomes for this subgroup of patients.

The Norwood operation and subsequent Fontan operation in infants with complex congenital heart disease.

From April 1987 to September 1993, 60 infants underwent a Norwood operation for complex congenital heart disease including hypoplastic left heart syndrome (n = 41), ventricular septal defect and subaortic stenosis with aortic arch interruption/severe coarctation (n = 7), complex single right ventricle with subaortic stenosis (n = 8), critical aortic stenosis with endocardial fibroelastosis (n = 2), and malaligned primum atrial septal defect with coarctation (n = 2). Age at operation ranged from 1 day to 3.9 months (mean 9 days, median 3.5 days). The operative mortality (< 30 days) was 33% (20 patients). Late mortality was 17% (10 patients). Nine of the 20 (45%) operative deaths occurred during the first 2 days after the operation as a result of sudden hemodynamic instability. All four infants with premature closure of the foramen ovale had pulmonary lymphangiectasia and died of pulmonary failure. Seven operative deaths have occurred in 36 patients since 1990 (19%); in the past 2 years, no operative deaths have occurred in 22 patients. Overall, there are 30 long-term survivors (50%). Twenty-one of these 30 infants have undergone a two-stage repair with a modified Fontan operation at 7.3 to 27.6 months of age (mean 18.1 months) with no mortality. Six patients have entered a three-stage repair strategy by undergoing a hemi-Fontan procedure at 6.8 to 23.0 months (mean 8.8 months) with no mortality, and two of these patients have now had their modified Fontan operation at 23.0 to 46.7 months of age with no mortality (four are still awaiting surgery). Two patients have undergone a two-ventricle repair with a Rastelli procedure, with no mortality at 7.4 and 14.1 months of age. Early in our experience, infants undergoing the Norwood operation had a high early mortality most often related to sudden hemodynamic instability. After we instituted a protocol that adds carbon dioxide to the inspired gas during postoperative mechanical ventilation, the postoperative course became more stable and there have been no operative deaths. In summary, the operative mortality for the Norwood operation continues to improve. A subsequent Fontan operation can be performed with excellent clinical results.

Aprotinin therapy for insertion of ventricular assist devices for staged heart transplantation.

Bleeding after insertion of ventricular assist devices is a common problem which carries a major risk of immediate and late complications. We evaluated the safety and efficacy of aprotinin in six patients undergoing staged heart transplantation and compared the results with those of six patients who received no aprotinin. The groups did not differ significantly with respect to age, gender, preoperative cause of cardiomyopathy, or cardiopulmonary bypass time. Patients treated with aprotinin had a significant reduction in postoperative chest tube drainage (743 +/- 457 versus 2036 +/- 1184 cc, respectively, for aprotinin therapy versus no therapy; p = 0.047). Blood transfusion requirements were reduced in patients treated with aprotinin (2.2 +/- 2.2 versus 10.7 +/- 7.1 U respectively, for aprotinin therapy versus no therapy; p = 0.038). No demonstrable serious side effects were attributed to the aprotinin treatment. We conclude that aprotinin is effective in reducing bleeding and transfusion requirements without increasing the incidence of clinically significant renal dysfunction or thromboembolic events.

Analysis of edge-tracking errors inherent in fluoroscopic images of the beating heart.

RATIONALE AND OBJECTIVES: Because of the complex relationships between the dynamic three-dimensional cardiac surface shape and its projected image, errors arise with the use of two-dimensional silhouettes to measure displacements of the heart. The character and frequency of such errors are examined. METHODS: A high-precision x-ray scatter imaging technique was used to reconstruct the three-dimensional shape of the left ventricular free wall throughout the cardiac cycle. Displacements of the three-dimensional surface were then compared with those on the two-dimensional projected silhouette. Silhouette displacement errors were determined as a function of time during the cardiac cycle and variability between hearts. RESULTS: Differences between silhouette measurements and those on the cardiac surface range from 0% to 125% of peak-to-peak displacements occur, along 33% to 75% of the silhouette contours and cover 66% of the cardiac cycle. CONCLUSION: Two-dimensional silhouette displacements provide inconsistent measurements of motion patterns on the three-dimensional cardiac surface.

Improved recovery of immature myocardium with L-glutamate blood cardioplegia.

Enhancement of myocardial recovery with glutamate-enriched cold blood potassium cardioplegia (BPC) was evaluated using an isolated working heart model. Three groups of hearts from immature rabbits were subjected to 20 minutes of warm (37 degrees C) ischemia to allow energy depletion, followed by 90 minutes of hypothermic (10 degrees C) ischemia. Myocardial protection provided during hypothermia consisted of cardioplegia infusion, at 50 mm Hg every 30 minutes at 4 degrees C, of either St. Thomas' Hospital solution (group 1, n = 6), oxygenated BPC (group 2, n = 7), or oxygenated BPC enriched with 20 mmol/L L-glutamate (group 3, n = 7). Percent recovery of aortic flow was 87.6% +/- 6.3% (results expressed as mean +/- standard error of the mean) in group 3, which was significantly better than for either group 1 (63.4% +/- 4.0%) or group 2 (47.0% +/- 3.5%) (p < 0.05 by analysis of variance). Group 3 hearts had significantly better recovery of myocardial energy stores (mumol/g dry weight) compared with group 1 or 2 hearts: adenosine triphosphate, 17.8 +/- 1.1 versus 12.4 +/- 1.5 and 12.1 +/- 0.4; creatine phosphate, 25.9 +/- 1.8 versus 17.8 +/- 1.8 and 20.3 +/- 0.7; and glycogen, 140.7 +/- 12.6 versus 98.7 +/- 9.9 and 60.7 +/- 9.9 (p < 0.05). Glutamate-enriched BPC provided excellent myocardial protection after ischemia in this immature model, and this study quantitatively supports the use of glutamate-enriched BPC in neonatal clinical practice.