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Biomedical subjects

J W Hammon

Publications and source records attributed to J W Hammon.

At least 109 records · Page 6Linked to original sources
PubMed1981

Early operative intervention in aortic bacterial endocarditis.

Since 1974, 14 patients have required valve replacement for native aortic valve bacterial endocarditis at Vanderbilt University Medical Center. There were 7 male and 7 female patients ranging from 11 to 65 years old. Nine of the patients were less than 27 years old. All patients had congestive heart failure as a complication of the bacterial endocarditis and were in New York Heart Association (NYHA) Functional Class III or IV. Two patients were seen initially with arrhythmias, 3 had episodes of septic emboli, and 1 patient was operated on immediately after sustaining a cardiac arrest. Echocardiogram was utilized in 9 patients, and cardiac catheterization was performed in 6 patients who were suspected to have concomitant mitral valve or coronary artery disease. All patients were operated on within two weeks after the institution of antibiotic therapy, and there were no operative or early postoperatively deaths. Preoperative blood cultures were positive in 13 patients, with streptococcus cultured in 6 patients and staphylococcus in 4. Escherichia coli and enterococcus were the other pathogens cultured. All patients received antibiotics intravenously for a total of six weeks. There has been 1 late postoperative death, which occurred 2 months following operation in a patient with myocardial failure unresponsive to treatment. Two patients underwent reoperation, 1 because of a persistent aorto-right ventricular fistula and the second because of paraprosthetic aortic regurgitation. Nine patients are now in NYHA Functional Class I and 4 are in Class II.

Adolescent↗
PubMed1981

Comparison of the effects of saline and homologous plasma infusion on lung fluid balance during endotoxemia in the unanesthetized sheep.

The effects of saline infusion (20 ml/kg/30 minutes) and homologous plasma infusion (20 ml/kg/30 minutes) on the lung fluid balance during increased pulmonary capillary permeability secondary to Escherichia coli endotoxin infusion (1 microgram/kg/15 minutes) were studied in unanesthetized sheep. Saline and homologous plasma infusion increased lung lymph flow by 10.6% and 10.8%, respectively. The bloodless wet-to-dry ratio was 5.1 +/- 0.2 in the saline group and 5.2 +/- 0.2 in the homologous plasma group. The saline infusion decreased the plasma oncotic pressure while the plasma infusion increased plasma oncotic pressure. However, the increase in plasma oncotic pressure was negated by concomitant changes in the lymph oncotic pressure and greater increases in pulmonary microvascular pressure during the plasma infusion. Changes in pulmonary microvascular pressure predominated over changes in the oncotic pressure gradient. Both saline and homologous plasma infusion increase fluid filtration into the interstitial space by the same magnitude. Therefore neither has a clear advantage in the treatment of pulmonary edema during increased permeability.

Animals↗
PubMed1980

An analysis of the pulsatile hemodynamic responses of the pulmonary circulation to acute and chronic pulmonary venous hypertension in the awake dog.

In this study we measured high fidelity pulsatile pressure and flow waveforms at the inlet to the pulmonary vascular bed to assess the differences in adaptation to acute and chronic pulmonary venous hypertension in awake dogs. Acute elevations in left atrial pressure (P1a) were effected by inflation of left atrial balloons, while chronic elevations were accomplished by placement of aorta to left atrial shunts. Pulmonary artery hydraulic impedance was calculated and analysis of these data revealed marked differences between the responses to acute and chronic elevations of left atrial pressure. The acutely stressed dogs (n = 12) had significantly decreased pulmonary vascular resistance (when P1a = 16.9 +/- 1.0 mm Hg, PVR = 212 +/- 57 dynes sec/cm5; when P1a = 28.6 +/- 1.4 mm Hg PVR = 18 +/- 115 dynes sec/cm5; control P1a = 6.1 +/- 1.5 mm Hg, and PVR = 355 +/- 69 dynes sec/cm5) and normal characteristic impedances (ZO) (210 +/- 36, 227 +/- 39, 178 +/- 14 dynes sec/cm5, respectively), indicating recruitment of arteriolar-capillary perfusion density and no change in proximal pulmonary arterial physical properties. The chronic pulmonary venous hypertension group (n = 11) retained normal PVR (496 +/- 30 dynes sec/cm5) but demonstrated a markedly higher characteristic impedance, ZO = 361 +/- 11 dynes sec/cm5 (P < 0.001). This indicated a measurably different and extremely potent effect of chronic venous hypertension on the physical properties of the pulmonary vessels with an apparently increased arterial stiffness correlating with a 4-fold increase in Young's elastic modulus. These changes were not reversed by alpha-adrenergic blockade or acute lowering of left atrial pressures.

Acute Disease↗
PubMed1980

Hypoplasia of the systemic ventricle in congenitally corrected transposition of the great arteries: preoperative documentation and possible implications of operation.

This article describes the determination of small systemic ventricular volume by quantitative cineangiocardiography in two patients with congenitally corrected transposition of great arteries, Ebstein's malformation of the systemic atrioventricular valve, and ventricular septal defect. A subjectively small systemic ventricle and an Ebstein-like abnormality of the systemic atrioventricular valve have been described previously in association with congenitally corrected transposition, but in vivo quantification of ventricular size and pump function has not been reported. An initial palliative rather than a totally corrective procedure is probably desirable in patients with this combination of findings. Ventricular volume calculations may prove useful as an aid in selection of operation in this setting.

Adolescent↗
PubMed1980

Total anomalous pulmonary venous connection in infancy. Ten years' experience including studies of postoperative ventricular function.

The surgical experience with total anomalous pulmonary venous connection (TAPVC) at the Venderbilt Hospital between the years 1969 and 1979 was reviewed. Twenty-five patients with TAPVC were studied. All but one patient presented at less than 1 year of age, and 11 patients were operated upon in the first 2 weeks of life. Operative mortality rate was 20% (5/25). Four of the five deaths were in critically ill neonates requiring preoperative ventilatory support. All operative deaths were in patients with pulmonary venous obstruction. All operative survivors have been followed for a mean 4.5 years (6 months to 10 years). There have been no late deaths or cases of symptomatic pulmonary venous obstruction. All children have had normal growth patterns. Ten patients have been recatheterized. Pulmonary artery systolic pressure, which was markedly elevated prior to operation, fell to normal levels after operation. Ventricular function has been evaluated by quantitative angiocardiography in nine patients before and after operation. Left ventricular size and function were markedly depressed preoperatively and rose to normal levels in postoperative survivors. Left atrial maximal volume was found to be 94% of normal values. These data support the contention that preoperative pulmonary venous obstruction is the single risk factor predicting higher risk of operative death. The presence of severe depression of left ventricular size and function preoperatively does not predict a higher operative risk, and postoperative survivors can expect normal ventricular function.

Angiocardiography↗
PubMed1979

Pulmonary vascular impedance analysis of adaptation to chronically elevated blood flow in the awake dog.

Pulsatile pulmonary hemodynamics were analyzed in a chronic awake canine high flow model. Standard mean flow and pulsatile flow hemodynamics were measured and alterations in the proximal pulmonary vascular physical properties were quantified by the characteristic impedance (Zo). Pulmonary vascular resistance (PVR), which assesses arteriolar-capillary recruitment of perfusing radius and measures a more distal pulmonary vascular response to changing flows, also was calculated. Twelve control dogs were studied and had mean Qpa (pulmonary blood flow) = 2.02 +/- 0.15 liters/min, Zo = 193 +/- 20 dyne sec cm-5 and PVR = 416 +/- 32 dyne sec cm-5. Ten dogs were studied awake 20 weeks after creation of bilateral arteriovenous fistulae. Five of these shunted dogs, designated group A, developed Qpa = 3-4 liters/min (mean = 3.80 +/- 0.09, P less than 0.001 different from control group); the other five dogs (group B) developed Qpa = 4-8 liters/min (mean = 5.87 +/- 0.16, P less than 0.001). In group A, Zo = 143 +/- 8 (P less than 0.05) and PVR = 249 +/- 6 (P less than 0.10). In group B, Zo = 90 +/- 5 (P less than 0.005) and PVR = 126 +/- 14 (P less than 0.01). The total input power (potential and kinetic) was 125% above the controls for group A (P less than 0.001) and 264% for group B (P less than 0.001), but the mean energy components increased significantly more than did the pulsatile components. These data demonstrate a lower impedance to pulsatile flow during chronically elevated total flow which effects a reduction in both the work load of the right ventricle and the transmission of energy to the precapillary bed. Analysis of the alterations in characteristic impedance suggests a distinct proximal pulmonary vascular mechanism of decreased vessel stiffness (decreased elastic moduli) for adaptation to chronically elevated flow loads which is in addition to the two geometric alterations of proximal arterial dilation and distal vascular channel recruitment.

Analog-Digital Conversion↗
PubMed1979

Regional myocardial dimensions following coronary artery bypass grafting in patients. Relationship of functional deterioration to graft occlusion.

The direct relationship between graft flow and regional midwall myocardial function has not been documented in patients. Therefore, the present study was designed to quantitate the effects of coronary artery bypass grafting on regional myocardial mechanics distal to a coronary artery obstruction. Twenty-one patients with subtotal or total occlusion of the left anterior descending (LAD) coronary artery underwent coronary artery bypass grafting. Following completion of the aortic and coronary anastomoses, two miniature ultrasonic dimension transducers (2.5 mm. diameter) were positioned within the minor axis of the anterior left ventricular free wall and were allowed complete freedom of movement. The transducers were placed at midwall depth, and areas of clinically apparent myocardial fibrosis were not utilized as sites of implantation. During control, 30 minutes following the termination of cardiopulmonary bypass, regional myocardial dimensions, pulmonary artery diastolic pressure, arterial pressure, and heart rate were recorded with all saphenous vein grafts open and after 30 seconds of single vein graft occlusion. These measurements were repeated during atrial pacing at a rate of 128 +/- 4 beats per minute. Data are mean +/- the standard error of the mean. During control, graft occlusion resulted in a regional decrease in systolic excursion from 1.3 +/- 0.1 to 1.0 +/- 0.2 mm. (p less than 0.01), as well as a decrease in the rate of shortening from 8.7 +/- 0.2 to 6.2 +/- 1.1 mm. per second (p less than 0.05); heart rate, mean arterial pressure, and diastolic pulmonary artery pressure remained unchanged. Graft occlusion with atrial pacing resulted in an exaggerated decrease in both regional systolic excursion, from 1.2 +/- 0.2 to 0.6 +/- 0.2 mm. (p less than 0.01), and rate of shortening, from 9.4 +/- 1.5 to 4.4 +/- 0.2 mm. per second (p less than 0.01). For the group of patients studied, end-diastolic lengths were unchanged with graft occlusion during control and atrial pacing. Moreover, with graft occlusion, isolated patients demonstrated regional dyskinesia as evidenced by holosystolic bulging. These studies in patients have documented for the first time that, despite a constant preload, afterload, and heart rate, regional myocardial function following coronary artery bypass grafting is dependent upon adequate graft flow, especially during stress.

Cardiac Pacing, Artificial↗
PubMed1978

The role of fibrin formation in the pathogenesis of bacteremic shock in the primate.

In this study, an attempt was made to elucidate further the role of intravascular fibrin formation in the pathogenesis of sepsis in the primate. It was found that injected live Escherichia coli caused death in primates within four to 11 hours as a result of microcirculatory failure and acidosis. Pretreatment with Arvin did not prolong the survival rate, probably because of an overloading of the reticuloendothelial system with fibrin degradation products. This study does not support an obligatory role for intravascular coagulation or fibrin formation in primate sepsis and coincides with an earlier report (6) from this laboratory on cats. Vascular damage and malfunction, secondary to mediators released by platelets, leukocytes, red cells or Hageman factor, are not ruled out.

Ancrod↗
PubMed1976

The effect of positive end-expiratory pressure on regional ventilation and perfusion in the normal and injured primate lung.

Although positive end-expiratory pressure (PEEP) is being employed in the management of respiratory insufficiency, many of its physiological effects remain undetermined. The cardiopulmonary effects of PEEP as well as its effect on regional ventilation and perfusion were studied in 10 baboons before and after pulmonary injury with oleic acid. In the normal lung, there was significant improvement in oxygenation at a PEEP of 5 cm. of water secondary to improved ventilation and perfusion in all PEEP greater than 5 cm. of water produced increasing mismatch of ventilation and perfusion in all zones. After oleic acid was injected, hypoxemia was evident with a reversal of the normal ventilation-perfusion (V/Q) relationship between upper and lower lung zones. This mismatch of ventilation and perfusion was corrected at a PEEP of 15 cm. of water. It was reasonable to conclude that the use of PEEP in the injured lung exerts it beneficial effect by balancing regional ventilation and perfusion in addition to increasing functional residual capacity.

Animals↗
PubMed1968

Adrenal cyst.

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Adrenal Gland Diseases↗