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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
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↗
PubMed1991

Heterotopic heart transplantation and native heart ventricular arrhythmias.

Heterotopic heart transplantation has been said to be contraindicated in patients with serious native heart arrhythmias that produce hemodynamic instability. Placement of heterotopic allografts, however, can theoretically act as a biological biventricular assist device to provide hemodynamic support during these unstable rhythms. Further, this operation might beneficially alter the hemodynamic milieu of heart failure such that the arrhythmias are ameliorated. Described is our experience with 4 patients with heart failure receiving heterotopic cardiac allografts, documenting changes in native heart arrhythmia that occurred. These cases demonstrate that heterotopic grafts can adequately sustain hemodynamics during malignant native heart dysrhythmia. We believe native heart ventricular arrhythmias are not a contraindication to heterotopic heart transplantation.

Arrhythmias, Cardiac↗
PubMed1989

Surgical treatment of atherosclerotic heart disease.

Because the surgical mortality rate in patients older than age 70 years is significantly higher than that of patients aged 50 to 60 years, surgical treatment of atherosclerosis in the elderly should be used after medical measures have failed. Balloon angioplasty is the surgical treatment of choice, but coronary artery bypass may be performed when necessary. In most patients older than 65 years, the rate of progression of atherosclerosis is slow, and additional surgical treatment may not be required for many years. In the elderly, atherosclerosis is often found in more than 1 of the 4 major arterial beds. About 15% of patients with coronary artery disease requiring operation have atherosclerosis in a second major arterial bed. Previously unpublished data on risk factors and survival rates in patients who have undergone coronary artery bypass surgery are reviewed.

Age Factors↗
PubMed1989

Renovascular reconstruction: factors affecting long-term prognosis in 919 patients followed up to 31 years.

During the 31-year period from May 3, 1955, to May 12, 1986, renovascular reconstructions were performed on 919 patients. The mean age of the 529 men was 54 +/- 0.58 (SE) years and, of the 390 women, 48 +/- 0.7 years. Mean preoperative diastolic blood pressure was 110 +/- 0.6 mm Hg. The most common causes of renal artery stenosis were atherosclerosis in 647 patients, fibromuscular disease in 161 patients, and renal artery aneurysm in 51 patients. In the remaining 60 patients, other causes were present, including kinks and fibrous bands. The most common surgical procedures were Dacron bypass graft (780 arteries) and endarterectomy with or without a patch graft (329 arteries). Four hundred sixty-nine patients had associated operations, the most common of which were abdominal aortic aneurysmectomy in 231 and aortoiliofemoral reconstruction in 141 patients. The perioperative mortality rate was 5.5% (51 of 919 overall); for renal procedures alone, it was 1.7% (8 of 450) and for combined surgical procedures, 9.2% (43 of 469). The overall graft patency rate at a follow-up of 18.8 +/- 1.9 months was 88.6% (381 of 430) and at a second follow-up of 50 +/- 4.3 months, 86.7% (111 of 128). Analysis of long-term blood pressure response and factors affecting late survival indicated that patients with preoperative diastolic pressures of greater than 100 mm Hg and renal artery stenosis of greater than 70% had the best blood pressure responses and that male sex, increasing age, bilateral renal stenosis, and associated vascular operations lowered the survival rate whereas fibromuscular disease enhanced the duration of survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1989

The St. Jude valve prosthesis: analysis of the clinical results in 815 implants and the need for systemic anticoagulation.

Between July 1979 and December 1984, 785 patients received 815 St. Jude Medical valve prostheses. Valve-related mortality in the follow-up period was due to thromboembolism in seven cases, anticoagulant-related hemorrhage in three and perivalvular leak in two. Freedom from valve-related death or reoperation at 3 years was 96.4% for aortic valve replacement and 98.3% for mitral valve replacement. The overall rate of thromboembolism was 2.6%/patient-year with warfarin, 9.2%/patient-year with antiplatelet medication and 15.6%/patient-year in patients with no anticoagulant therapy. One episode of thrombotic obstruction of a mitral valve, in a patient receiving no anticoagulant therapy, resulted in an occurrence rate of such obstruction of 0.22%/patient-year. Valve replacement with the St. Jude valve produced excellent clinical results, but long-term anticoagulation with warfarin was required to minimize thromboembolic complications. The use of antiplatelet agents alone provided inadequate protection.

Adolescent↗