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Biomedical subjects

R L Hardesty

Publications and source records attributed to R L Hardesty.

At least 181 records · Page 10Linked to original sources
PubMed1979

Arteriovenous ECMO for neonatal respiratory support. A study in perigestational lambs.

A study was undertaken to investigate the applicability of the arteriovenous mode of perfusion for partial support of neonatal respiration. Perigestational lambs, delivered by cesarean section, served as the animal model of respiratory distress. Arteriovenous flow was accomplished between a single umbilical artery and vein. A microchannel membrane oxygenator was used to provide partial respiratory support to the newborn lambs. Total systemic flow, pulmonary blood flow, and pulmonary vascular resistance were assessed at various rates of arteriovenous perfusion and correlated with systemic oxygenation. A reduction in right-to-left shunting of blood and pulmonary vascular resistance occurred as arterial oxygenation rose from conditions of hypoxemia to PaO2 values higher than 50 torr. Myocardial performance was not impaired at rates of arteriovenous perfusion below 30 percent of the total systemic flow, as evidenced by normal electrocardiographic tracings, pulmonary capillary wedge pressures, and central venous pressures. Arteriovenous extracorporeal membrane oxgenation (ECMO) may be particularly suitable for use in infants with hypoxia and high pulmonary vascular resistance.

Animals↗
PubMed1979

Dynamic computed tomography of the lung: regional ventilation measurements.

The spatial resolution provided by computed tomography (CT) yields excellent anatomic specificity, and fast scanners are capable of the serial imaging necessary to monitor rapid changes in tracer concentration over time. In this study, sequential CT imaging defined the temporal changes of xenon concentration in peripheral lung tissue of a nonhuman primate and three sheep, both during and after xenon inhalation. Ventilation rate constants (K) in lung tissue with normal and impaired function in the evaluation of regional ventilation using xenon enhanced CT are discussed.

Animals↗
PubMed1978

Selected therapy for ascending aortic aneurysms.

Since 1971, ten patients, 26 to 62 years of age, have undergone repair of ascending aortic aneurysms with concomitant aortic insufficiency. Three patients had Marfan's syndrome, five patients had cystic medial necrosis, one had leutic aortitis, and one had atherosclerotic involvement of the aorta. There was one operative death. Follow-up exceeds seven years. Because of the tendency for progressive annular and sinus dilation in Marfan's syndrome, composite graft and valve conduits with reimplantation of the coronary arteries is the procedure of choice. In selected patients with annulaortic ectasia, good valve tissue and no sinus dilation, bicuspidization of the valve, and replacement of the ascending aorta is indicated. The operation is generally less formidable than composite graft replacement, maintains normal coronary anatomy, and alleviates the long-term risks of anticoagulation.

Adult↗
PubMed1978

Delayed postoperative cardiac tamponade: diagnosis and management.

Symptoms and signs of decreased cardiac output associated with an elevated venous pressure should alert one to the possibility of delayed cardiac tamponade. Enlargement of the cardiothoracic ratio shown by serial roentgenograms and demonstration of significant pericardial effusion by echocardiogram or radionuclide angiocardiography support the diagnosis. Erratic response of the prothrombin time to administration of warfarin and abnormal results of liver function test are additional clues to its diagnosis. Right heart catheterization documents the presence of tamponade and excludes other diagnostic considerations. Operative decompression of the pericardial space can be accomplished by pericardicentesis, subxiphoid pericardiotomy, median sternotomy, or thoracotomy. Hemodynamic observations following the relief of tamponade assure that an adequate therapeutic procedure has been performed.

Adult↗
PubMed1978

Arteriovenous perfusion with the pulmonary assist membrane oxygenator.

The feasibility of employing a recently developed pulmonary assist membrane oxygenator for partial respiratory support in arteriovenous perfusion was studied using small mongrel dogs rendered hypoxic by oxygen depression. The unit is employed along with the conventional ventilation techniques (such as CPAP and PEEP) when the latter alone cannot maintain adequate gas exchange in the lung. The results indicate that poorly oxygenated arterial blood can be upgraded to life-sustaining levels when the bypass flow rate through the oxygenator is in the range of 18-33% of the total cardiac output. No cardiovascular derangements were noted at these arteriovenous flow rates for perfusion periods of four to six hours. The present results demonstrate the feasibility of providing partial support to pulmonary function using the pulmonary assist membrane oxygenator.

Animals↗
PubMed1977

Coarctation of the aorta with ventricular septal defect.

From 1965 to 1974, 53 children with coarctation of the aorta (COA) and an associated ventricular septal defect (VSD) underwent cardiac catheterization. Thirty-one patients presented with congestive heart failure. Twenty-five of 27 patients (92%) who underwent cardiac catheterization under age 3 months had either systemic hypertension, a systolic gradient across the coarctation greater than 20 mm Hg or both. Pulmonary hypertension was present in all 25 patients. COA repair was performed in 39 patients and there were seven deaths. Of the 32 survivors, 23 have no residual gradient; six are normotensive but have a mild residual gradient; three are hypertensive or have a gradient greater than 20 mm Hg. Repair of the VSD or pulmonary artery banding has been performed in 11 of 44 patients who survived infancy. Spontaneous closure of the VSD has occurred in three cases and 25 patients have a small VSD that does not warrant surgical repair. Surgical repair of COA during infancy may be unavoidable but conservative medical management of the associated VSD is often successful.

Aortic Coarctation↗
PubMed1977

Discrete subvalvular aortic stenosis. An evaluation of operative therapy.

Angiocardiographic and operative observations support the validity of classifying the spectrum of congenital subvalvular aortic stenosis into a membrane, fibromuscular collar, and tunnel. Our current operative method is to excise a thin membrane or thick fibrous ridge, and, if a fibromuscular collar or tunnel is identified, to effect a left ventricular myomectomy as described by Morrow for hypertrophic subaortic stenosis. Data from experience with 35 children indicate that this approach is effective and safe. Gradients are substantially reduced and residual obstruction acceptable. Successive clinical evaluations (100 percent of 33 survivors) over an interval of 1 to 13 years (mean of 6) affirm that amelioration of the obstruction endures.

Angiocardiography↗
PubMed1977

Valve replacement in children and adolescents.

Replacement of diseased heart valves has become the treatment of choice in many adults. Valve replacement in older children and adolescents has been done in our institution only when other procedures are ineffective. Over the past 10 years, 24 patients have received 28 artificial valves. Thirteen (54 per cent) had rheumatic heart disease; the remainder had congenital or acquired valvular abnormalities. The Björk-Shiley valve was most commonly used in the aortic position and the Beall prosthesis in the mitral position. Sixteen patients (67 per cent) survived operation and have been followed from 3 to 79 months, averaging 27 months. All are free of cardiac symptoms. Hemarthrosis occurred once in 2 survivors (13 per cent). Eight patients died (33 per cent), 5 immediately postoperatively and 3 within a year after the operation. The mortality rate has declined to 21 percent during the past 3 years. Our experience in the pediatric age group suggests that valve replacement is a serious undertaking with higher mortality rate than in adults. The operation should be reserved for those patients in whom valvuloplasty or valvulotomy is expected to be ineffective.

Adolescent↗
PubMed1975

Surgical treatment of atrioventricular canal defect.

Fifty-nine patients with congenital anomalies of the atrioventricular canal underwent operation and all survivors were followed up. In 42 patients with partial atrioventricular canal defects, ten had preoperative congestive heart failure. Three, or 7.1%, died of endomyocardial fibroelastosis, high pulmonary vascular resistance, and severe mitral regurgitation. A fourth patient later died of Wolff-Parkinson-White syndrome and fibrilation. Reoperations in five patients were all successful. No patients had persistent atrioventricular blocks, and all patients are asymptomatic. Two of these subjects continue to receive digoxin therapy, and one of them is believed to have substantial mitral insufficiency. Of the 17 patients who had complete atrioventricular canal defects, 13 had a divided common anterior leaflet attached to the septum by chordae tendineae, and four had undivided and unattached anterior leaflets. Two had previously undergone pulmonary banding, and nine were treated for congestive heart failure. Six died after operation. There were no reoperations. No patient presently has required a pacemaker. Two subjects have persistent cardiomegaly.

Adolescent↗
PubMedDate not supplied

Evaluation of right ventricular function during clinical left ventricular assistance.

Hemodynamic and mechanical parameters of right ventricular (RV) performance were measured in eight patients undergoing left ventricular (LV) assistance as a bridge to cardiac transplantation. All patients, even those with impaired RV performance, survived support and transplantation. The reduction of LV afterload produced by the left ventricular assist system (LVAS) results in RV afterload reduction, which permits even the marginal RV to function adequately during LVAS support.

Adult↗
PubMedDate not supplied

ECMO support for adult patients with acute respiratory failure.

The authors analyzed factors that may influence the outcome of adult patients with respiratory failure who were treated with ECMO. Between December 1990 and July 1995, the authors used ECMO to support 33 patients (age range, 17-56 years) with respiratory failure from adult respiratory distress syndrome (ARDS; n = 9), primary graft failure after lung transplantation (n = 16), late graft failure after lung transplantation (n = 5), and miscellaneous reasons (n = 3). Twenty (61%) patients were successfully weaned from ECMO, and 13 (39%) survived to hospital discharge. Venoarterial ECMO was used in 46% of survivors, compared with 60% of nonsurvivors (p = 0.43). The time on mechanical support before ECMO and the duration on ECMO for survivors and nonsurvivors was 2.9 +/- 1.8 days vs 5.0 +/- 1.3 days (p = 0.35), and 6.5 +/- 1.8 days vs 5.7 +/- 1.1 days (p = 0.68), respectively. Compared with the nonsurvivors, survivors had higher PF ratios (PaO2/FIO2; 104 +/- 33 vs 81 +/- 8, p = 0.43) before ECMO was initiated, although the differences were not significant. Among the patients who received ECMO for primary graft failure, 75% were weaned from ECMO, and 56% survived to discharge. ECMO is beneficial for adult patients with respiratory failure, especially those with primary graft failure after lung transplantation.

Acute Disease↗
PubMedDate not supplied

Interleukin-6, a marker of preservation injury in clinical lung transplantation.

Interleukin-6 (IL-6) is one of the cytokines produced by human alveolar macrophages, lung parenchyma, and other cells in response to injury and infection. We hypothesized that IL-6 is released from poorly preserved lung grafts and may serve as a marker of preservation injury. Sixteen patients who received lung allografts were enrolled in this study. The average ischemic time was 284 +/- 78 minutes. Serum IL-6 level was measured before and at 4 and 24 hours after reperfusion of the grafts by an enzyme-linked immunosorbent assay. Preservation injury was assessed by (1) the need for prolonged intubation (> 7 days), (2) the arterial/alveolar oxygen tension ratio (PaO2/PAO2 ratio) at 4 hours after graft reperfusion (only in heart-lung or double lung recipients), (3) the presence of diffuse alveolar damage on first lung biopsy, and (4) the 30-day graft survival rate. IL-6 level peaked at 4 hours after reperfusion and returned to baseline at 24 hours. The patients were divided into group I (n = 6) and group II (n = 10), depending on whether the 4-hour IL-6 level was more than 1000 pg/ml or less than 500 pg/ml, respectively. Group I patients required longer intubation (p < 0.01) and had a lower PaO2/PAO2 ratio (p < 0.001), more diffuse alveolar damage (p < 0.01), and a lower graft survival rate (p < 0.01) than those of group II. No bacterial, fungal, or viral infection was found during postoperative week 1 in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗