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Biomedical subjects

J N Cunningham

Publications and source records attributed to J N Cunningham.

At least 127 records · Page 7Linked to original sources
PubMed1982

Scanning electron microscopic study of endothelial damage resulting from vein graft contraction during preparation.

Preservation of the endothelial lining of veins during preparation as grafts appears likely to play a critical role in subsequent early graft patency rates. 82 cephalic veins from 41 dogs were divided into 6 major groups by the type of heparinized vein preservation solution used. Veins were soaked for 5 min. or 1 hr. at either 10 degrees C or 20 degrees C in one of the following solutions with or without 60mg/100 ml of papaverine added: Plasma-Lyte 148 autologous blood, or Fluosol DA (an oxygenated perfluorocarbon emulsion). A segment was removed from each vein as soon as it was dissected free and perfused with fixative at 30 mm Hg as a control. In 4 additional dogs both cephalic veins were perfusion fixed in situ as further controls. SEM examination of the vein grafts' luminal surface after storage in the various preservation solutions showed that the greatest single cause of endothelial cell damage or loss was the extent to which the vein was permitted to undergo vigorous contraction during preparation and storage prior to use as an arterial graft. Preparation solutions which contained the smooth muscle cell relaxant papaverine, therefore, minimized endothelial protrusion and loss. In this regard Plasma-Lyte plus papaverine maintained at 20 degrees C was the most satisfactory of the solutions tested.

Animals↗
PubMed1981

Blood potassium cardioplegia administration. Comparison of myocardial protection offered by three techniques.

To investigate the best method of administration of blood potassium cardioplegia, 19 dogs were studied while undergoing 120 minutes each of aortic crossclamping (myocardial temperature, less than 15 degrees C). Group 1 (six dogs) underwent a single 120-minute period of aortic crossclamping with the heart protected by multiple reinjections (1,000 mL every 30 minutes) of blood potassium cardioplegia solution (potassium chloride, 30 mEq/L; pH, 8; temperature, less than 15 degrees C). Group 2 (six dogs) underwent four separate 30-minute periods of aortic crossclamping, but allowing hearts to beat in a nonworking state for 20 minutes at 35 degrees C between each arrest interval. Hearts in group 3 (seven dogs) were initially arrested as described above, following which a continuous infusion (75 mL/min; KCl, 10 mEq/L) of blood potassium cardioplegia solution was maintained throughout the arrest period. Measurements of myocardial metabolism, ventricular function, regional blood flow, and ultrastructure were carried out before arrest and 30 minutes after final unclamping. Analysis of the data revealed no significant benefit of one method over another, with the exception that adenosine triphosphate level was least preserved with intermittent unclamping and reperfusion. Because continuous perfusion techniques are more cumbersome than multidose reinjection, and intermittent aortic crossclamping lengthens total cardiopulmonary bypass time, we favor the simplest approach, multidose reinjection during a single uninterrupted period of aortic crossclamping.

Adenosine Triphosphate↗
PubMed1981

Vein contraction and smooth muscle cell extensions as causes of endothelial damage during graft preparation.

Meticulous preservation of the endothelial lining of vein grafts harvested during vascular operations is undoubtedly an important factor in determining patency rates following bypass procedures. Destruction of the vein graft's endothelial lining prior to graft implantation results in a more thrombogenic graft which is essentially a collagen-lined tube. This study used light, transmission, and scanning electron microscopy to investigate effects of various methods of vein graft preparation on endothelial and smooth muscle cells of the dog cephalic vein. Veins were removed and stored in one of three heparinized solutions at 10 C for either five minutes or one hour: autologous blood, Plasmalyte((R)) or Plasmalyte((R)) with 0.6 mg/ml papaverine HCI added. The vein wall was extremely sensitive to dissection, manipulation, or introduction of fixative solutions and reacted to such stimuli with severe contraction which not only diminished the luminal diameter but also resulted in protrusion of endothelial cells into the lumen and formation of cytoplasmic extensions of medial smooth muscle cells. Such cytoplasmic extensions were particularly frequent in the immediate subendothelial area and appeared to be instrumental in elevating, separating, or desquamating the endothelial cell lining. Veins stored in blood alone demonstrated the greatest vessel wall contraction and endothelial cell loss. Veins soaked in Plasmalyte((R))-papaverine solution had the most relaxed and normal appearance with minimal endothelial cell loss. Papaverine-treated veins which were subjected to brief periods of distension at pressures of 100 mmHg or greater demonstrated large gaps between the endothelial lining cells. The results suggest pretreatment with papaverine greatly reduces vein graft endothelial cell loss due to contraction, although such relaxation may be detrimental if vein grafts are subjected to excessive pressure prior to reversal of relaxation.

Animals↗
PubMed1981

Cardiac output determination after cardiac operation. Lack of correlation between direct measurements and indirect estimates.

Ninety-two mean thermodilution cardiac indices were determined in 25 patients following cardiac operations. Arterial and venous blood gases, hematocrit, body temperature, central venous pressure, left atrial pressures, urine output, heart rate, and mean arterial pressure were simultaneously recorded. Six variables, arterial and venous pH, arterial and venous PCO2, venous PO2, and temperature, showed significant simple correlations with cardiac index, but the degree of correlation was inadequate for use of these variables as reliable indices of cardiac function. When stepwise multiple regression analysis was performed, two variables, venous PO2 and left atrial pressure were associated with the best correlation with cardiac index, such that CI = 0.073 PO2V -- 0.060 LAP + 1.39 (r = 0.60, p less than 0.001). When measured values for venous PO2 and left atrial pressure were substituted into this equation, a "predicted" value for cardiac index could be obtained with only slightly improved reliability. The data indicate that indirect estimation of cardiac output by measurement of the various laboratory parameters described above is not sufficiently reliable for clinical use. The importance of obtaining direct measurements of cardiac output by thermodilution or other means in order to properly evaluate postoperative cardiac function is stressed.

Blood Gas Analysis↗
PubMed1979

Constant-pressure aortic root perfusion versus cardioplegia and hypothermia. Comparison of methods of myocardial protection.

Both coronary perfusion and hypothermic cardioplegia are widely used methods of myocardial protection during aortic valve replacement. A theoretical objection to coronary perfusion is that it is not synchronized with cardiac contractions. Accordingly, a special pump was designed to provide perfusion at a constant range of pressure. Twenty dogs were studied during 4 hours of bypass. In six dogs no manipulations were carried out and hearts were allowed to beat in a nonworking state. Seven dogs underwent 2 hours of aortic cross-clamping and constant-pressure aortic root perfusion. Seven dogs underwent 2 hours of uninterrupted aortic occlusion with myocardial protection being maintained by cold potassium-induced arrest, Contractility did not change significantly in any of the three groups. All animals demonstrated significant hyperemia after bypass but normal endocardial/epicardial flow ratios. Although compliance deteriorated in all groups, the most striking changes were seen following 4 hours of bypass alone or constant-pressure aortic root perfusion. Hypothermic potassium arrest, in contrast, provided a slightly greater degree of myocardial protection, perhaps both by limiting the degree of ischemic injury directly and by excluding the heart from the circulating blood and the pump oxygenator system.

Animals↗
PubMed1977

Long-term results in 1375 patients undergoing valve replacement with the Starr-Edwards cloth-covered steel ball prosthesis.

The two principal considerations with prosthetic valves are durability and thromboembolism. With the widespread interest in recently developed prosthetic valves (porcine, tilting disc, Cooley), the long-term results at one institution with a single prosthesis were considered of particular importance. Accordingly, a 97% follow-up has been completed on 1375 patients (pts) undergoing prosthetic valve replacement with the Starr-Edwards cloth-covered steel ball prosthesis at New York University between October 1967 and December 1975. Operative procedures were as follows: aortic valve replacement (AVR): 470 pts; mitral valve replacement (MVR): 362 pts; combined AVR and MVR: 129 pts; other combined procedures: 414 pts. Overall operative deaths were 13.7%, 9% for AVR, 10.8% for MVR, and 18.6% for combined AVR and MVR. At seven years, AVR survival was 64%, and MVR survival 64.5%. There has been widespread pessimism, usually without significant data, about the cloth-covered prosthesis, because of concern of cloth wear, hemolysis and other complications. Therefore, a particularly significant finding by actuarial analysis was that 85% of surviving patients with isolated AVR remained free of emboli for five years. In pts surviving isolated MVR, 80% remained free of emboli for five years. Of those having embolic episodes, 33% were not on anticoagulants. Fatal hemorrhage from anticoagulants occurred in 0.8% of pts. Endocarditis occurred in 5.7% of the entire group, with 1.3% requiring reoperation. Clinically significant hemolysis occurred in 5.1% of the group, with only 0.2% requiring reoperation. Hence, the total frequency of clinically significant cloth-wear was less than 0.5%. These data indicate both the reliability and the limitations of the Starr-Edwards cloth-covered steel ball valve and can be used in comparing experiences with the more recently developed prostheses.

Aortic Valve↗
PubMed1977

Pseudocoarctation and mid-arch aortic coarctation.

A 21-year-old woman was found to have a mid-arch aortic coarctation in combination with pseudocoarctation. The angiographic disgnosis was established by left atrial injection after transseptal puncture.

Adolescent↗
PubMed1977

Use of autologous fascia lata as a pericardial substitute following open-heart surgery.

Thirteen patients requiring repeat open-heart surgery had autologous free fascia lata grafts implanted to effect complete pericardial closure. In four patients, the graft was used to augment the pericardial space because of myocardial failure and enlargement. In the remainder, fascia lata was used because shrinkage, scarring, or absence of the pericardium from prior operation prevented primary closure. No hemodynamic problems related to implantations of the grafts were seen. The harvesting of the grafts produced no functional deficits, and complications at the donor site were insignificant. Complete pericardial closure with fascia lata protects underlying myocardial structures (i.e., saphenous vein grafts) in the event that further reoperation for bleeding or infection is required. In addition, it provides for compartmentalization of the mediastinum, allowing accurate assessment of the site of postoperative bleeding.

Adolescent↗