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Biomedical subjects

H Laks

Publications and source records attributed to H Laks.

At least 307 records · Page 17Linked to original sources
PubMed1977

A servo controlled transapical left ventricular to aortic assist device with implantable canulae.

A servo controlled transapical LV to aortic bypass system employing a roller pump was evaluated. The pump achieved complete LV decompression with reduction of LV pressure below systemic pressure. The servo control was responsive to LA pressure and allowed stable complete bypass during interventions designed to raise and lower LA pressure. A permanently implantable transapical LV cannula and aortic cannula without obturators was evaluated with and without anticoagulants. The teflon felt surface 'healed' rapidly and developed a multi-layered fibrous pseudointima. Anticoagulants appeared to avoid excessive thrombus formation at the cannula sites and embolization.

Animals↗
PubMed1977

The effect of left atrial-to-aortic assistance on infarct size.

Left atrial-to-aortic (La-A) assistance is effective in supporting the failing circulation. This study evaluated its effect in salvaging ischemic myocardium in both large and small infarct models. In a control group, good correlation was shown between measurements of infarct size by ST-segment mapping at 20 minutes, triphenyl tetrazolium chloride staining at 5 hours, and the distribution of radioactive microspheres (P less than 0.01). A servo controlled assist pump was used which controlled pump speed according to the left atrial pressure. This allowed greater degrees of bypass for prolonged periods with reduced risk of air embolism. La-A assistance reduced systolic left ventricular pressure, and reduced the pressure time index (P less than 0.05). La-A assistance did not reduce infarct size measured by ST-segment mapping in a large infarct model when instituted before occlusion or 20 minutes after occlusion. Triphenyl tetrazolium chloride staining, however, showed less severe and homogenous damage in the assisted group as compared to controls. Electron microscopy confirmed the patchy nature of the ischemia. In a small infarct model, La-A assistance reduced nST from 6.3 +/- 0.8 to 3.8 +/- 1.5 and ST from 4.9 +/- 0.6 to 2.7 +/- 0.9 (P less than 0.05). The endocardial to epicardial ratio in the ischemic area fell from 0.69 +/- 0.05 to 0.43 +/- 0.05 in the control group (P less than 0.05) and a similar fall occurred in the assisted groups. La-A assistance is thus effective in reducing myocardial ischemia in a small infarct model, but appears to be less effective in a large infarct model.

Animals↗
PubMed1977

The effects of cardiopulmonary bypass with crystalloid and colloid hemodilution on myocardial extravascular water.

The effect of cardiopulmonary bypass (CPB) on myocardial extravascular water (MEW) was evaluated with crystalloid and colloid hemodilution. Heart water was measured gravimetrically and by the double-indicator and thermal methods. CPB without hemodilution resulted in a 5.7 per cent increase in the wet : dry weight ratio of the left ventricle obtained by desiccation to stable weight. CPB with colloid hemodilution to a hematocrit of 10.7 +/- 0.4 per cent resulted in a 5.4 per cent increase in the wet:dry weight ratio. Crystalloid hemodilution to a hematocrit of 9.5 +/- 0.8 per cent resulted in a marked increase in myocardial water with a wet:dry weight ratio 30.3 per cent greater than the controls. Hypothermic (22 degrees C.) crystalloid hemodilution resulted in a 37.4 per cent increase in the wet:dry weight ratio. MEW was also measured by the double-indicator method with Evans blue dye and tritiated water. This method measured 85 per cent of the gravimetrically measured water. Although it indicated the increase in heart water in the crystalloid group, it proved less reliable in the measurement of MEW in this dynamic situation. The thermal heart water was also measured with an impedance and thermistor-bearing catheter similar to that used to measure thermal lung water. This proved ineffective in measuring heart water. Colloid hemodilution was thus found to prevent the development of myocardial edema which occurred with crystalloid hemodilution (p less than 0.01) with and without hypothermia. These findings support the addition of colloid to the hemodilution prime used for cardiopulmonary bypass.

Animals↗
PubMed1977

Long-term effect of the superior vena cava-pulmonary artery anastomosis on pulmonary blood flow.

The long-term effects of the superior vena cava-pulmonary artery anastomosis were evaluated in 15 patients a mean of 8.5 years postoperatively. There were eight patients with tricuspid atresia and seven with other complex anomalies. Ten patients underwent 133xenon ventilation scans and 99mtechnetium perfusion scans in the upright and suprine positions. Perfusion scans showed decreased perfusion of the right upper lobe which improved in the supine position. Shunt flow, measured by thermodilution in nine patients, was a mean of 1.7 L. per minute per square meter, with a mean superior vena caval pressure of 8 mm. Hg and a resistance of 3.0 units. Right and left pulmonary venous saturations were 94 and 96 percent, respectively, showing little intrapulmonary shunting. Venous collaterals were the major cause for shunt failure. Six patients underwent a left Blalock-Taussig shunt and division of venous collaterals a mean of 6 years after the Glenn shunt and are all doing well. The superior vena cava-pulmonary artery anastomosis did not result in progressive pulmonary deterioration in the patients studied. The staged treatment of tricuspid atresia by the Glenn shunt followed by a systemic-pulmonary artery shunt and ligation of venous collaterals gives prolonged effective palliation.

Adolescent↗
PubMed1977

Valve replacement in children.

Since 1964, 27 valve replacements have been performed in patients who ranged from 5 months to 20 years of age. Fourteen underwent aortic valve replacement, 10 underwent mitral valve replacement, two had systemic atrio-ventricular valve replacement, and one had tricuspid valve replacement. Nineteen patients had congenital heart disease, five had rheumatic disease, and three had Marfan's syndrome. Starr-Edwards prostheses were used in 17 patients, Björk-Shiley prostheses in six, and procine xenografts in for. There were five early deaths and five late deaths. Patients were followed for 2 months to 6 years postoperatively (mean 2.1 years). All survivors showed clinical improvement. There were no episodes of thromboembolism. Minor bleeding, arrhythmias, and bacterial endocarditis occurred infrequently.

Adolescent↗
PubMed1977

In situ placement of a valved conduit at the pulmonary annulus.

The technique of repair of pulmonary atresia with intact ventricular septum is described. The porcine valved conduit (Hancock) was placed so that the valve was in the "anatomic" position, avoiding compression by the sternum. There was a mild gradient (15 mm. Hg) at a cardiac index of 4 L. per minute per square meter across the porcine valve itself, measured at the postoperative catheterization. The valve orifice diameter was only 15 mm., which is considerably less than the 22 mm. valve annulus. The possible merits of this procedure over the conventionally placed valved conduit and over an outflow tract patch are discussed.

Cardiac Catheterization↗
PubMed1976

Intraaortic balloon assistance.

Intraaortic balloon (IAB) assistance in 64 patients over 2 1/2 years has resulted in a survival rate of 11% (1 patient) when used alone but 47% when utilized in patients treated surgically (long-term survival, 38% [21 patients]). Patients undergoing coronary artery bypass grafting or aortic valve replacement have a long-term survival of 50% (8 and 9 patients, respectively). The required duration of IAB support has a bearing on the clinical result. Complications have been minimal. Though it was originally developed to assist in the nonoperative management of complications of ischemic heart disease, IAB assistance offers significant promise as an adjuvant to operative therapy for both ischemic and valvular heart disease.

Aortic Valve↗
PubMed1976

A servocontrolled atrial-aortic assist device: experimental findings and clinical experience.

A servocontrol system was developed to regulate a single roller pump left atrial-aortic (La-A) assist device. Responsiveness of the servomechanism to blood volume changes, myocardial damage, and mitral regurgitation was evaluated in 5 sheep and 6 dogs. Myocardial damage was induced by occlusion of coronary arteries. and the hemodynamic effects of La-A assistance were evaluated. While La-A assistance reduced left atrial pressures to low levels, the left ventricular end-diastolic pressure remained elevated in the severely damaged heart. LaA-assistance was used in 3 patients. Two were weaned from cardiopulmonary bypass after failure of intraaortic balloon counterpulsation, and 1 is a long-term survivor. The third was supported for 48 hours after attempt repair of complex congenital heart disease. The servocontrol device added to the safety of prolonged La-A assistance. This mode of assistance should be considered when intraaortic balloon counterpulsation has failed.

Adolescent↗
PubMed1976

The relationship between muscle surface pH and oxygen transport.

The relationship between muscle surface pH (pHM) and the arterial-venous oxygen content difference (AVO2D) was studied in 4 patients undergoing reconstructive arterial surgery and in 6 patients undergoing acute normovolemic hemodilution. There was a consistent inverse relation between pHM in the ischemic lower extremity and the femoral AVO2D before, during and after aortic clamping. There was also an inverse relation between AVO2D and pHM during hemodilution. These data confirm that pHM is a reliable indicator of tissue perfusion and correlates with the AVO2D.

Adult↗
PubMed1976

Crystalloid versus colloid hemodilution in man.

The effects of intraoperative prebleeding and hemodilution with lactated Ringer's solution on hemodynamics, oxygen transport and lung water were studied in four patients undergoing extensive surgical procedures. The results were contrasted with those previously obtained from hemodilution of a group of patients with Plasmanate. The mean volumes bled were 1,950 milliliters in the lactated Ringer's solution group and 1,697 milliliters in the Plasmanate group. The posthemodilution hematocrit values were 26 per cent and 25 per cent, respectively. Cardiac output increased to only 115 per cent of the base line in the lactated Ringer's solution group but to 161 per cent in the Plasmanate group. Systemic oxygen transport was reduced to 80.0 per cent in the lactated Ringer's solution group, while in the Plasmanate group, it rose to 109.7 per cent. The lung water and alveolar arterial oxygen gradients were increased to 134 and 112 per cent in the lactated Ringer's solution group, whereas in the Plasmanate group, the lung water was reduced to 82 per cent, and the arterial alveolar oxygen gradient was reduced to 75 per cent. In these selected patients, hemodilution was well tolerated. Plasmanate hemodilution resulted in better compensatory changes than did hemodilution with lactated Ringer's solution in terms of oxygen transport and changes in lung water.

Adult↗
PubMed1975

The Blalock-Hanlon procedure. Simple transposition of the great arteries.

Between 1959 and 1975 at St. Louis University Medical Center, 71 patients underwent surgery with the Blalock-Hanlon technique. Thirty-nine had simple transposition of the great vessels. The mean age at the time of operation was 3.4 weeks. Sixty-four percent were less than 1 month of age. Eighty-five percent survived the operation. In 11 the Blalock-Hanlon procedure was performed after failure of ballon septostomy. Arterial saturation was increased from a mean of 47% to 73%. There were three late deaths prior to Mustard repair (intra-atrial baffle procedure). Sixteeen patients underwent Mustard repair at a mean age of 4 years and a mean follow-up of 2 1/2 years. There were three deaths after surgery and three late deaths after the Mustard procedure. The Blalock-Hanlon procedure achieves prolonged palliation, avoiding an emergency Mustard procedure in infancy with its risk of late vena caval obstruction.

Cardiac Surgical Procedures↗
PubMed1975

Local cardiac hypothermia for myocardial protection during correction of congenital heart disease.

Eighty-eight operations for correction of intracardiac congenital heart defects were performed using local cardiac hypothermia for protection of the ischemic myocardium. Twenty-six patients underwent repair of tetralogy of Fallot, 23 had patch closure of ventricular septal defect, 24 had correction of various types of congenital aortic stenosis, and 15 were operated upon for other complex lesions. The overall operative mortality was 5.6%. Ischemia times ranged from 9 to 119 minutes (mean, 48 minutes). Ischemic arrest protected by local cardiac hypothermia provides an optimal operative field, permitting repair of uncomplicated intracardiac defects in a precise, unhurried manner. No hemodynamic abnormalities attributable to the technique were encountered.

Adolescent↗
PubMed1975

A twenty year survey of arterial complications of renal transplantation.

The significant arterial complications of renal transplantation are hemorrhage, infarction, stenosis and aneurysm formation. Hemorrhage is often associated with sepsis and may be lifethreatening. Large infarcts may be secondary to multiple small vessels or intraoperative hypotension with inadequate perfusion of the organ. Nephrectomy is invariably indicated in these situations. Renal artery stenosis with resultant hypertension may occur secondary to stenosis at the anastomosis, atherosclerotic plaque formation or intimal fibrosis of the renal artery. Operative reconstruction if the anastomotic site may relieve hypertension is selected patients but places the transplanted kidney greatly at risk. Aneurysm formation is often mycotic and is associated with multiple operations and wound sepsis. The iliac artery may be ligated without loss of limb, while the resultant claudication may be relieved by a surgical bypass procedure.

Aneurysm↗
PubMed1975

Intraoperative prebleeding in man: effect of colloid hemodilution on blood volume, lung water, hemodynamics, and oxygen transport.

The effects of acute normovolemic hemodilution on lung water, blood volume, hemodynamics, and oxygen transport were studied. The subjects were six patients undergoing major operations, with prebleeding and hemodilution under fluoroxene and nitrous oxide anesthesia. The menatocrit was reduced form 43 to 25 percent in one step, with simultaneous infusion of Plamanate and lactated Ringer's solution. Blood volume was expanded by 5 percent by the hemodilution. The major compensation was a striking rise in cardiac output to 161 percent. Systemic oxygen transport (CO times arterial O2 content) increased despite the marked fall in oxygen-carrying capacity, and the arteriovenous O2 content difference decreased. Lung water the aveolararterial (A-a) oxygen differences were reduced. The procedure was well tolerated by this group of selected patients and homologous blood utilization was reduced.

Adult↗