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Biomedical subjects

M E DeBakey

Publications and source records attributed to M E DeBakey.

At least 19 recordsLinked to original sources
PubMed1995

Cytomegalovirus and atherosclerosis.

Finding that an avian herpesvirus can cause atherosclerosis in chickens prompted studies of human herpesviruses in human atherosclerosis. Antigens and nucleic acid sequences of cytomegalovirus (CMV), a widespread member of the herpesvirus family, were found in arterial lesions in human atherosclerosis, but infectious virus has not been observed. In atherosclerosis patients, high levels of CMV antibodies are present, suggesting the presence of virus that had been activated from a latent state. Atherosclerosis also develops in immune-suppressed heart transplant patients infected with CMV. The properties of CMV are consistent with its involvement at several levels of the atherogenic process. If this concept is correct, immunization with a CMV vaccine should prevent CMV infection and atherosclerosis.

Arteriosclerosis↗
PubMed1995

A fluid dynamic analysis using flow visualization of the Baylor/NASA implantable axial flow blood pump for design improvement.

The Baylor/NASA Axial Blood Flow Pump has been developed for use as an implantable left ventricular assist device (LVAD). The pump is intended as an assist device for either pulmonary or systemic circulatory support for more than 3-months' duration. To date the pump provides acceptable results in terms of thrombus formation and hemolysis (IH of 0.018 g/100 L). A fluid dynamics analysis using flow visualization was performed to investigate the flow fields and to determine areas within the pump that could be improved. These studies focused upon the inflow area in front of the pump. A prototype axial flow pump assembly was constructed to facilitate the flow visualization studies. Particle image tracking velocimetry techniques were used to measure Amberlite particles suspended in a blood analog fluid composed of 63% water and 37% glycerin. This method used a pulsed (612 Hz) laser light to determine flow velocity profiles, shear stress, Reynolds numbers, and stagnant areas within the axial pump. These studies showed that the flow straightener (a vaned assembly in the pump inflow) reduced Reynolds numbers from 4,640 to 2,540 (at 8.5 L/min) and that the flow straightener exacerbates a discontinuity found between it and the impeller. Within the inflow area, a maximum of 80 N/m2 shear stress was measured, which is well below published blood damage thresholds. Design variations were investigated resulting in a smoother flow transition between flow straightener and impeller. These variations must be investigated further to establish a correlation with hemolysis and thrombus formation.

Blood Flow Velocity↗
PubMed1994

Health care costs.

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Academic Medical Centers↗
PubMed1994

Cytomegalovirus DNA in arterial walls of patients with atherosclerosis.

The biological properties of cytomegalovirus (CMV) are consistent with a potential role in the pathogenesis of atherosclerosis. The evidence of such a role has so far been circumstantial, but CMV nucleic acid is beginning to be reported with increasing frequency in the arterial wall. Arterial specimens from 135 patients who underwent vascular surgery for symptomatic atherosclerotic vessel disease were analyzed by PCR for the presence of CMV nucleic acid. Samples were studied from the atheromatous plaque area and from uninvolved aortic tissues of patients undergoing surgery for vascular disease. One primer pair (LA) was used for detection of a late gene, and two other primer pairs (E1 and E2) were used for the immediate early gene region. Serum antibody to CMV was measured by radioimmunoassay. With the late gene primer, CMV nucleic acid was found in 76% of the tissue specimens tested, whereas the E2 gene primer complementary to the transforming mtr2 region was reactive in 90% of the arterial samples. There was no significant difference in the prevalence of CMV DNA in atherosclerotic plaque tissue and in uninvolved aortic tissue from the patients. A second early gene primer was not reactive with the tissue specimens, although it gave positive results with the positive control of infectious virus. Serum antibody to CMV was detected in 86% of the patients in whose tissue CMV DNA was demonstrated. CMV DNA was detected in a high proportion of atherosclerotic plaque tissues as well as in uninvolved aortic tissue of surgical patients, suggesting that latent CMV infection of the arterial wall may be a common occurrence in patients with atherosclerosis.

Adult↗
PubMed1994

Cardiopulmonary bypass with Nikkiso and BioMedicus centrifugal pumps.

In our department, a new compact and atraumatic centrifugal pump, Nikkiso, was developed as a second-generation cardiopulmonary bypass pump. To assess and confirm the function and controllability of this pump, comparative studies of cardiopulmonary bypass with Nikkiso and BioMedicus centrifugal pumps were performed using calves. Both pumps provided pump flows of 60-70 ml/kg/min without incidence. The hemodynamics of both groups were stable and within the normal range, and no leakage or thrombus formations were observed in either pump. All hematology and biochemistry data showed no significant differences between the two groups. Plasma free hemoglobin values of the Nikkiso pump tended to be lower than those of the BioMedicus pump. The Nikkiso pump was easy to handle because of its smaller size, and air removal was easily performed because of its low priming volume. The Nikkiso pump demonstrated easy manipulation and good controllability. This compact, atraumatic centrifugal pump meets the requirements for a second-generation cardiopulmonary bypass pump.

Animals↗
PubMed1993

Long-term fate of the aortic root and aortic valve after ascending aneurysm surgery.

OBJECTIVE: The authors determined in which patients tube graft replacement could be used. SUMMARY BACKGROUND DATA: Tube graft replacement of ascending aortic aneurysms requires no coronary anastomoses and preserves the native aortic valve, but aortic insufficiency or aortic root aneurysms may develop requiring reoperation. Use of Bentall or Cabrol composite valve graft procedures obviates these problems but requires prosthetic valve replacement and coronary reattachment, both of which are associated with complications. These two procedures have been applied increasingly but because of renewed interest in aortic valve preservation and reconstruction, the authors determined in which patients tube replacement could be used. METHODS: The authors analyzed the fate of 277 patients, mean age 49 +/- 14 years, operated on between 1953 and 1992 by techniques that preserved the aortic root. The most common pathology was atherosclerosis in 104 patients. Perioperative mortality since 1975 was 14%. RESULTS: Fifteen patients required reoperation on the ascending aorta or aortic root; ascending aneurysm reoperation (6 patients); aortic valve replacement (8 patients), and a combined procedure (1 patient). Of these 15 patients, 8 had Marfan's syndrome, 10 had dissections, and 5 had medial degeneration/necrosis. CONCLUSIONS: Simple tube graft replacement of the ascending aorta was a durable technique in patients without Marfan's syndrome or medial degeneration/necrosis and allowed preservation of the native aortic valve in many patients.

Adolescent↗
PubMed1993

In vitro performance of the Baylor/NASA axial flow pump.

A cooperative effort between Baylor College of Medicine and NASA/Johnson Space Center is under way to develop an implantable axial flow left ventricular assist device (LVAD). The pump is intended as an assist device for either pulmonary or systemic circulatory support for more than 3 months' duration. Currently, in vitro studies are under way to reduce the hemolysis generated by the axial flow pump. A system utilizing a testing matrix has been developed to analyze the effects of different pump parameters on hemolysis. The following parameters are being investigated: impeller blade tip geometry, impeller/flow tube clearance, impeller/stator clearance, number of impeller blades, number of stator blades, and length of the impeller. To date, an index of hemolysis of 0.038 g/100 L has been achieved. The test matrix is not complete, and further improvements are expected.

Animals↗
PubMed1992

Experimental and clinical evaluation of a noninvasive reflectance pulse oximeter sensor.

The objective of this study was to evaluate a new reflectance pulse oximeter sensor. The prototype sensor consists of 8 light-emitting diode (LED) chips (4 at 665 nm and 4 at 820 nm) and a photodiode chip mounted on a single substrate. The 4 LED chips for each wavelength are spaced at 90-degree intervals around the substrate and at an equal radial distance from the photodiode chip. An optical barrier between the photodiode and LED chips prevents a direct coupling effect between them. Near-infrared LEDs (940 nm) in the sensor warm the tissue. The microthermocouple mounted on the sensor surface measures the temperature of the skin-sensor interface and maintains it at a present level by servoregulating the current in the 940-nm LEDs. An animal study and a clinical study were performed. In the animal study, 5 mongrel dogs (weight, 10-20 kg) were anesthetized, mechanically ventilated, and cannulated. In each animal, arterial oxygen saturation (SaO2) was measured continuously by a standard transmission oximeter probe placed on the dog's earlobe and a reflectance oximeter sensor placed on the dog's tongue. In the first phase of the experiment, signals from the reflectance sensor were recorded while the dog was immersed in ice water until its body temperature decreased to 30 degrees C. In the second phase, the animal's body temperature was normal, and the oxygen content of the ventilator was varied to alter the SaO2. In the clinical study, 18 critically ill patients were monitored perioperatively with the prototype reflectance sensor. The first phase of the study investigated the relationship between local skin temperature and the accuracy of oximeter readings with the reflectance sensor. Each measurement was taken at a high saturation level as a function of local skin temperature. The second phase of the study compared measurements of oxygen saturation by a reflectance oximeter (SpO2[r]) with those made by a co-oximeter (SaO2[IL]) and a standard transmission oximeter (SpO2[t]). Linear regression analysis was used to determine the degree of correlation between (1) the pulse amplitude and skin temperature; (2) SpO2(r) and SaO2(IL); and (3) SpO2(t) and SaO2(IL). Student's t test was used to determine the significance of each correlation. The mean and standard deviation of the differences were also computed. In the animal study, pulse amplitude levels increased concomitantly with skin temperature (at 665 nm, r = 0.9424; at 820 nm, r = 0.9834; p < 0.001) and SpO2(r) correlated well with SaO2(IL) (r = 0.982; SEE = 2.54%; p < 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Spinal oxygenation, blood supply localization, cooling, and function with aortic clamping.

Similar to other methods of organ preservation, "spinoplegia" may protect the spinal cord from the effects of oxygen desaturation during aortic cross-clamping. In porcine experiments, spinal cord O2 saturation was studied during intraoperative localization of the blood supply to the spinal cord using hydrogen; division of arteries not supplying the spinal cord; aortic cross-clamping for 60 minutes; and 60 minutes after unclamping. In 5 animals, 120 mL of cold saline solution with lidocaine (100 mg/dL) was infused into the aorta during aortic cross-clamping. During sequential localization, O2 saturation dropped by 40.02% (standard deviation, 20.16%) for T-14 artery testing versus a decrease of 17.27% (standard deviation, 11.88%; p = 0.0075) for L-5 artery segment testing in the control animals and returned to baseline thereafter. During aortic cross-clamping maximal O2 desaturation was 5% of baseline (15.7%; p less than 0.0001), which improved slightly by 30 minutes after clamping (48% of baseline +/- 37.37%; p = 0.048 versus maximum) and then returned to baseline (97.1% of baseline +/- 41%) with unclamping; 5 minutes later, hyperoxygenation occurred with a progressive decline thereafter (68% of baseline +/- 29.3%; p = 0.025, 45 minutes after unclamping versus baseline). The decrease in spinal motor evoked potentials was significantly less (p less than 0.02) in the treated group. Intraoperative hydrogen testing in 8 patients was demonstrated to be safe. It accurately localized reattached arteries, and O2 saturation of the spinal cord fell by 56% (standard deviation, 29%; p = 0.0025) with aortic cross-clamping. We conclude that spinal cord ischemia occurs with aortic cross-clamping in both animals and humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A compact centrifugal pump for cardiopulmonary bypass.

A majority of the cardiopulmonary bypass (CPB) systems still utilize bulky roller pumps. A direct-drive small centrifugal pump intended for second-generation CPB pump has been developed. The pump has a 50 mm diameter impeller and provides a 6 L/min flow at 3,000 rpm against 300 mm Hg. A flexible drive shaft allows us to separate the pump head from the console resulting in easier manipulation. An in vitro study showed that the pump generated less hemolysis (index of hemolysis = 0.0011, comparable to the value for Bio-medicus BP-80). To improve blood flow around the shaft-seal region and to reduce thrombus formation around the shaft, six holes were drilled through the impeller. In biventricular bypass experiments using calves, our pump demonstrated excellent antithrombogenicity and durability for 48 h. And the compact and atraumatic centrifugal pump system showed excellent performance and easy manipulation under actual CPB conditions in animal.

Animals↗
PubMed1992

Versatile one-piece total artificial heart for bridge to transplantation or permanent heart replacement.

A versatile, one-piece total artificial heart (TAH) system that can be driven by either an electromechanical acutator (EM-TAH) or a pneumatic source (P-TAH) has been developed. The common units for both TAHs are the conically shaped left and right pusher-plate-type pumps (63 ml SV) that sandwich a thin centerpiece (18 mm) having a respective actuator. The EM actuator, mounted in the middle of the centerpiece, consists of a direct-current brushless motor and a roller screw while the pneumatic actuator consists of a low-pressure air source. The outer diameter of the pumping unit is 97 mm with its central thickness being 82 mm; overall volume is 510 cc. The TAH is operated in the left master alternative ejection mode with the left pump fill signal. High-flex-life Hexsyn rubber is used as the diaphragm, and the blood-contacting surface is coated with dry gelatin. The TAH can provide 3-8 L/min flow with a preload of 1-10 mm Hg against 100 mm Hg afterload. Anatomical fit of the pumping unit has been demonstrated in the pericardial space of 26 heart transplant recipients with average body weight of 78 kg. To date, 2 P-TAH and 4 EM-TAH (1 week) implantations were performed in 80-100 kg calves demonstrating excellent anatomical fit, controllability, and biocompatibility. This versatile TAH is suitable for a bridge to transplantation or permanent heart replacement.

Animals↗
PubMed1991

The National Library of Medicine. Evolution of a premier information center.

From a small collection of medical publications in the Surgeon General's Office in 1836, the National Library of Medicine has developed into the leading repository of medical information in the world. Despite strong opposition and impediments from certain quarters, involving considerable machinations and intrigue, the determination of interested medical leaders and sympathetic members of Congress triumphed in having this remarkable institution established on the campus of the National Institutes of Health, Bethesda, Md. As a participant in many of the negotiations preceding that decision, I have happily witnessed the transformation of the Library, long housed in cramped, makeshift quarters, to its present magnificent structures in the heart of our nation's foremost medical research center. Its prodigious collection of print, audiovisual, and electronic information; its imaginative research projects; its excellent outreach program; and its innovative services and products are indispensable to all practicing health professionals, scientists, and medical educators, as well as to journalists, government officials, and others. The ultimate beneficiary, of course, is the patient.

History, 19th Century↗