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Biomedical subjects

R W Stewart

Publications and source records attributed to R W Stewart.

89 records · Page 5Linked to original sources
PubMed1983

Repair of transposition of the great arteries with ventricular septal defect by an arterial switch operation.

Six patients with transposition of the great arteries and a large ventricular septal defect (VSD) underwent repair by transatrial VSD closure and arterial switching with translocation of the coronary ostia. They ranged in age from 2.0 to 18.8 months, and weighed between 3.2 and 9.9 kg. Each patient survived the perioperative period and was clinically well 7.2 to 15.9 months later. Cardiac catheterization studies done in four patients 0.25 to 7.5 months after surgery showed normal ventricular function in all, a competent aortic valve in two, and trivial and mild aortic valve incompetence in one each. This experience with a small group supports this surgical method as the procedure of choice for most patients with transposition of the great arteries and large VSD.

Abnormalities, Multiple↗
PubMed1982

Relationship of whole body oxygen consumption to perfusion flow rate during hypothermic cardiopulmonary bypass.

Whole body oxygen consumption (Vo2) and its relationship to randomly selected arterial perfusion flow rates (Q) during profoundly hypothermic (20 degrees C) cardiopulmonary bypass were determined in 17 adult patients undergoing routine coronary artery bypass operations. Vo2 falls progressively as Q decreases, from 33 +/- 8.2 ml . min(-1) . m(-2) at Q of 2.0 L . min(-1) . m(-2) to 28 +/- 5.8 at Q of 1.5, 25 +/- 5.7 at Q of 1.0, 20 +/- 4.1 at Q of 0.5, and 14 +/- 5.4 at Q of 0.25. This progressive decrease suggests shutdown of areas of the microcirculation. The upper 70% confidence limit overlaps the asymptote at Qs above 1.2. Percent oxygen extraction increases progressively as Q decreases, from 11 +/- 3.3% at Q of 2.0 to 45 +/- 9.6% at Q of 0.25, suggesting reduced reserves. Mixed venous Po2 and oxygen saturation fall linearly with decreasing Q below 1.2 (r = 0.78 and r = 0.89, p less than 0.0001, respectively), suggesting decreasing flow to perfused areas. Internal jugular venous Po2 and oxygen saturation (measured in 10 patients) fall linearly with decreasing Q below 1.8 (r = 0.72 and r = 0.88, p less than 0.0001, respectively), suggesting decreasing flow to perfused areas of the brain and a difference from the rest of the body in its behavior with decreasing Q. Thus, during cardiopulmonary bypass cerebral blood flow, autoregulation seems present at 20 degrees C. The data set indicates that flows of about 1.2 may be adequate despite limited reserves.

Aged↗
PubMed1981

Complement activation during cardiopulmonary bypass: evidence for generation of C3a and C5a anaphylatoxins.

We observed complement activation in 15 adults undergoing total cardiopulmonary bypass. Plasma levels of C3a were significantly elevated (P < 0.0001) at the beginning of the procedure, and they continued to increase steadily thereafter. At the end of the procedure, C3a levels were more than five times higher than preoperative levels. Plasma levels of C5a (a factor that binds avidly to neutrophils) did not change significantly during cardiopulmonary bypass. Instead, there was significant neutrophilia (P = 0.03) during bypass, and significant transpulmonary neutropenia (P = 0.0002) occurred when cardiopulmonary circulation was reestablished at partial bypass. The neutropenia is consistent with pulmonary-vascular sequestration of C5a-activated granulocytes. We also found that incubation of blood with the nylon-mesh liner of bubble oxygenators, as well as vigorous oxygenation of whole blood, promotes conversion of complement. We conclude that the complement-derived inflammatory mediators C3a and C5a produced during extracorporeal circulation may contribute to the pathogenesis of "post-pump syndromes."

Adult↗
PubMed1979

Repair of double-outlet right ventricle. An analysis of 62 cases.

Sixty-two patients with double-outlet right ventricle (DORV) underwent complete intracardiac repair between 1967 and July, 1978. Five patients (three deaths) with DORV and complete atrioventricular (AV) canal are the subject of a separate report and are not discussed further here. Twenty-eight patients had relatively uncomplicated DORV (subaortic ventricular septal defect [VSD], doubly committed VSD, or 1-malposition of the aorta with subaortic VSD) with or without pulmonary stenosis. Two (14%) of 14 died after a completely intraventricular repair, and one (12%) of eight after repair including use of a valved external conduit. Use of a transannular patch in this group was an incremental risk factor, five (83%) dying among six treated in this way. Anterior enlargement of a restrictive or unfavorably located VSD did not increase risk. A noncommitted VSD was an incremental risk factor, two (50%) of four dying after repair. No instances of complete heart block occurred in these groups. Two late deaths occurred in the uncomplicated group, from persisting servere pulmonary hypertension. The late results were good in the remainder and in the two surviving patients with noncommitted VSD. After repair of the Taussig-Bing type of DORV, eight deaths (32%) occurred among 25 patients. Complete heart block developed in two patients. In the Taussig-Bing type of DORV, the 6 year actuarial survival rate was only 38%. Most late deaths were related to improtant pulmonary vascular disease. The surgical technique that has evolved for the basic tunnel repair in the various types of DORV is described.

Adolescent↗
PubMed1973

Use of mailed questionnaire data in a study of swine congenital malformations.

A study was designed to evaluate the representativeness and accuracy of data collected on swine birth defects by mailed questionnaire. The study was conducted in the three contiguous counties of Johnson, Lafayette and Pettis in west central Missouri. A personal interview survey and an examination of malformed pigs were used to validate mailed questionnaire data which estimated the frequency and distribution of malformations observed in pigs over a six month period. This period between April and September 1970 was defined as the study period. The results were compared to a previous six month period (April-September 1969), or baseline period, when only the mailed questionnaire was used. The frequency and distribution of the reported malformations by type did not differ significantly (at the p=0.05 level) between the study period (70.4% response) and the baseline period (31.3% response). Evaluation of this and additional data collected during the study suggested that the mailed questionnaire can be used effectively to estimate the frequency and distribution of swine malformations within a defined geographic area.

Animals↗
PubMedDate not supplied

Nonpulsatile ventricular assist bridging to transplantation.

Six patients accepted into a cardiac transplantation program have been supported with a Biomedicus LVAD. Five of the six patients deteriorated while awaiting a donor organ; the sixth was being supported with a device following mitral valve surgery and showed no recovery of ventricular function. In all cases the device was used only after all other therapeutic modalities had failed. The periods of support ranged from 2.5 to 31 days, mean of 10 days. Three patients underwent cardiac transplantation and all three have been discharged and are well. The three survivors were supported for 2.5, 3, and 31 days. Three deaths occurred in the patients supported for 5, 9, and 15 days, the causes being sepsis, massive cerebral embolism, and respiratory failure. Patients were for the most part maintained with some degree of heparinization, and hemolysis was a significant problem in only one patient and associated with a very small arterial return cannula. Flows were routinely maintained above 2.4 L/min/m2, and all showed recovery of other organ functions while being supported. The patient supported for 31 days was capable of limited mobilization by use of the removable drive system. The Biomedicus LVAD represents a relatively inexpensive support modality for patients awaiting cardiac transplantation.

Adult↗