A comparison of flat-sheet and hollow-fiber membrane oxygenators: the Shiley M-2000 vs. the Bentley BOS-CM 40.

To compare new flat-sheet and hollow-fiber membrane oxygenators for use in cardiopulmonary bypass, we randomly divided 40 coronary artery surgery patients into 2 groups of 20 patients each. The Shiley M-2000 flat-sheet membrane oxygenator was used in 1 group, and the Bentley BOS-CM40 hollow-fiber membrane oxygenator was used in the other group. Both oxygenators allowed for adequate transfer of oxygen and carbon dioxide. At the end of perfusion, the platelet counts were significantly lower and the arterial pH significantly higher in the Shiley group than in the Bentley group. The other hematologic parameters, as well as postoperative blood losses, were similar in the 2 groups, but were also similar to those reported earlier with respect to bubble oxygenators. On the basis of these results, we conclude that, for routine short-term perfusion, these new membrane oxygenator models, while marginally different from one another, offer no real advantage over bubble models.

Combined mitral valve and coronary artery surgery.

During the past 10 years, 50 patients underwent combined coronary artery bypass grafting (CABG) and mitral valve replacement (MVR) at our clinic, with additional aortic valve replacement (AVR) in six cases. The early mortality was 8%. During the first half of the study period this mortality was 4/11 patients, but in the second half it was 0/39. All six patients with CABG + MVR + AVR survived the operation. Adverse factors were found to be advanced functional impairment, female sex, concomitant untreated aortic valvulopathy and elevated pulmonary vascular resistance. All 46 patients who survived the operation were followed up for a mean period of 31 months, and during that time there were nine deaths. The survival rate was 54% after 3 years and 40% after 5 years. Most of the patients had improved by at least one functional class. The good results in this series probably were attributable to improvements in surgical procedure (introduction of cold potassium cardioplegia) and in postoperative management (intra-aortic balloon pumping).

Relationship of brain blood flow and oxygen consumption to perfusion flow rate during profoundly hypothermic cardiopulmonary bypass. An experimental study.

A study was made of the relation of brain blood flow and oxygen consumption to changes in perfusion flow rate during cardiopulmonary bypass at 20 degrees C in nine cynomolgus monkeys. Four perfusion flow rates varying from 0.25 to 1.75 L X min-1 X m-2 were randomly instituted, each for a 10 minute period. At the end of each period, brain arteriovenous oxygen content difference was measured and 15 mu radioactive microspheres were injected into the arterial perfusion line. The brain was then removed and section into anatomic regions and radioactivity was counted. Regional and total brain blood flows were calculated, as was whole brain oxygen consumption. Brain perfusion continued in all areas at all perfusion flow rates. Whole brain blood flow decreased (p less than 0.0001) as perfusion flow rate was reduced (45 +/- 6.5, 41 +/- 7.9, and 23 +/- 2.8 ml X min-1 X 100 gm-1 at 1.5, 1.0, and 0.5 L X min-1 X m-2, respectively). The proportion of the total perfusion delivered to the brain increased (p = 0.003) with decreasing perfusion flow rates (5.4% +/- 0.78%, 7.1% +/- 1.24%, and 8.2% +/- 1.11% at 1.5, 1.0, and 0.5 L X min-1 X m-2, respectively). Brain blood flow resistance remained unchanged (p = 0.4) while that of the remaining body increased (p less than 0.0001). There was a greater reduction of blood flow in the cortical white matter (p = 0.01) than in other regions of the brain. Brain oxygen consumption was the same (p = 0.5) at all perfusion flow rates, related to an increasing percent oxygen extraction with decreasing perfusion flow rate (p less than 0.0001). The data indicate that all areas of the brain remain perfused, even at low perfusion flow rates, during profoundly hypothermic cardiopulmonary bypass, and that brain oxygen consumption is maintained in part by increased oxygen extraction and in part by redistribution of the perfusate from the remaining body to the brain.

Prosthetic valve endocarditis.

Fifty-three (3.6%; actuarially 4.1% at 48 months) of 1465 consecutive in-hospital survivors of valve replacement from 1975 to July 1979 (aortic, mitral, or aortic and mitral, only one untraced) developed prosthetic valve endocarditis (PVE). Incremental risk factors for developing PVE were native valve endocarditis (p less than .0001), black race (p = .0001), mechanical prosthesis (vs bioprosthesis) (p = .005), male sex (p = .04), and longer cardiopulmonary bypass time (p = .09). In general, the hazard function for developing PVE was greatest at 3 weeks after valve replacement. Patients with native valve endocarditis had a tendency to develop PVE early after valve replacement, as did patients in whom mechanical prostheses were used. PVE associated with Staphylococcus epidermidis tended to appear within 6 months of valve replacement, whereas streptococcal PVE tended to appear later after valve replacement. PVE took an atypical form in some patients, but patients with possible PVE (n = 6) had the same findings as those with certain PVE (n = 47). In 11 patients bacteriologic confirmation of PVE was not obtained. The typical prosthetic and periprosthetic characteristics of PVE were present in 30 of the 40 cases in which observations were possible. PVE is a serious condition; 34 (64%) of our 53 patients died. Most deaths occurred within 3 months of the first evidence of PVE. Recovery of some patients is possible with appropriate medical and surgical treatment, but more intense preventive measures are indicated.

Determinants of early success in repair of aortic coarctation in infants.

Fifty-five infants less than 1 year of age underwent repair of coarctation of the aorta between 1967 and 1981. Sixteen (29%) died while in the hospital, with one death occurring from "pure" coarctation. Of the remaining patients, four among 20 with associated ventricular septal defect (VSD) and 11 among 19 with other major associated cardiac anomalies (p = 0.002) also died. Thirteen (62%) of 21 patients treated by resection and end-to-end anastomosis died in the hospital, while only two (7%) of 30 in whom the subclavian flap repair was used died (p less than 0.0001). Good femoral pulses were present early postoperatively in 29 of 30 patients with the subclavian flap in whom observations were recorded and in nine of 12 patients who received end-to-end anastomosis (p = 0.06). Multivariate analysis showed only the very small size of the patient, the presence of major associated cardiac anomalies other than VSD, and nonuse of the subclavian flap method to be incremental risk factors for hospital death. These data and the reports of others show the subclavian flap technique to be the method of choice for repair of coarctation of the aorta in infants.