[Show abstract][Hide abstract] ABSTRACT: Medications that target norepinephrine (NE) neurotransmission alter the behavioral effects of cocaine and may be beneficial for stimulant-use disorders. We showed previously that the short-acting, α1-adrenergic antagonist, prazosin, blocked drug-induced reinstatement of cocaine-seeking in rats and doxazosin (DOX), a longer-acting α1 antagonist blocked cocaine's subjective effects in cocaine-dependent volunteers. To further characterize DOX as a possible pharmacotherapy for cocaine dependence, we assessed its impact on the development and expression of cocaine-induced locomotor sensitization in rats. Rats (n = 6–8) were administered saline, cocaine (COC, 10 mg/kg) or DOX (0.3 or 1.0 mg/kg) alone or in combination for 5 consecutive days (development). Following 10-days of drug withdrawal, all rats were administered COC and locomotor activity was again assessed (expression). COC increased locomotor activity across days indicative of sensitization. The high dose (1.0 mg/kg), but not the low dose (0.3 mg/kg) of DOX significantly decreased the development and expression of COC sensitization. DOX alone did not differ from saline. These results are consistent with studies showing that α1 receptors are essential for the development and expression of cocaine's behavioral effects. Results also suggest that blockade of both the development and expression of locomotor sensitization may be important characteristics of possible pharmacotherapies for cocaine dependence in humans.
[Show abstract][Hide abstract] ABSTRACT: This report summarizes the results of the in vitro evaluation of Soviet and American artificial hearts. The devices were tested at the All-Union Institute of Transplantation and Artificial Organs, Moscow, U.S.S.R., and Baylor College of Medicine, Houston, Texas, U. S. A. These studies were designed to standardize procedures to allow comparison of artificial ventricles of different designs. Also, these studies might provide a means for evaluation of other characteristics such as hemolysis, durability, and reliability. Static and dynamic tests were performed, varying preload, afterload, rate, and systolic and diastolic time intervals. All designs demonstrated comparable function curves with capability of taking over the pressure and volume work of the natural heart.
[Show abstract][Hide abstract] ABSTRACT: In our laboratories we have developed a roller pump for cardiopulmonary bypass and circulatory assistance that has the ability to produce steady or pulsatile flow. The pulsatile mode can also be used for counterpulsation. The roller pump has been tested both experimentally and clinically. Studies have also been performed in vitro and in vivo to evaluate and select the best medical-grade roller pump tubing to be used in the pump for shortand longterm support. In vitro tests included rebounding of tubing volume versus revolutions per minute, rebounding over time with continuous pumping, flex life, and spallation. In vivo testing was performed in mongrel dogs using heparinless left heart bypass pumping for 6 h. Hematologic studies were performed during the procedure. Postmortem examination was performed, looking especially for thromboembolism. The tubing and connectors were also inspected. The results of the in vivo and in vitro tests of all tubings were then compared.
[Show abstract][Hide abstract] ABSTRACT: A collaborative effort between Baylor College of Medicine and NASA/Johnson Space Center is underway to develop an axial flow ventricular assist device (VAD). We evaluated inducer/impeller component designs in a series of in vitro hemolysis tests. As a result of computational fluid dynamic analysis, a flow inducer was added to the front of the pump impeller. According to the surface pressure distribution, the flow inducer blades were connected to the impeller long blades. This modification eliminated high negative pressure areas at the leading edge of the impeller. Comparative studies were performed between inducer blade sections that flowed smoothly into the impeller blades (continuous blades) and those that formed discrete separate pumping sections (discontinuous blades). The inducer/impeller with continuous blades showed significantly (p < 0.003) lower hemolysis with a normalized index of hemolysis (NIH) of 0.018 ±< 0.007 g/100 L (n = 3), compared with the discontinuous model, which demonstrated an NIH of 0.050 ± 0.007 g/100 L (n = 3). The continuous blade model was evaluated in vivo for 2 days with no problems. One of the pumps evaluated ran for 5 days in vivo although thrombus formation was recognized on the flow straightener and the inducer/impeller. As a result of this study, the pump material was changed from polyether polyurethane to polycarbonate. The fabrication method was also changed to a computer numerically controlled (CNC) milling process with a final vapor polish. These changes resulted in an NIH of 0.0029 ± 0.0009 g/100 L (n = 4). which is a significant (p < .0001) value 6 times less than that of the previous model. This model was used for in vivo studies and achieved 9 days of operation with a sufficient flow between 3.6 and 4.7 L/min against 80 to 100 mm Hg mean arterial pressure. Plasma free hemoglobin levels remained at 2–3 mg/dl with a hematocrit of 20%.
[Show abstract][Hide abstract] ABSTRACT: Our newly developed axial flow pump consists of a flow tube, an internal rotating impeller, and a fixed flow stator (we call the stator) behind the impeller. This pump produces a flow of 3 to 8 L/min against 50 to 150 mm Hg pressure difference, respectively, in the range of 10,000 to 16,000 rpm. An axial flow pump that will be used as a ventricular assist device (VAD) has to have low hemolytic and good antithrombogenic characteristics. This paper will show how to decrease the hemolytic properties of this axial flow pump systematically using a test matrix. The test variables evaluated were impeller blade tip geometry, impeller flow tube clearance (radial clearance), impeller stator clearance (axial clearance), impeller blade number, stator blade number, and impeller length. All in vitro hemolysis tests were performed at 5.0 L/min against 100 mm Hg pressure difference using a total of 83 bags of fresh bovine blood. The results were as follows: the impeller blade tip geometry did not significantly effect hemolysis, a 0.005-inch and a 0.009-inch radial clearance were significantly (p < 0.01 or 0.001) less hemolytic than the other clearances, a 0.075-inch axial clearance was significantly (p < 0.05) more hemolytic than the other clearances, two-and six-bladed impellers were significantly (p < 0.01 and 0.02, respectively) less hemolytic than a four-bladed impeller, a five-bladed stator was significantly (p < 0.05 or 0.01) less hemolytic than the other stators, and the impeller length did not make a significant difference. Currently, the best index of hemolysis is 0.031 ± 0.018 g/100 L, and using parameters from these results, implantable devices are being fabricated.
[Show abstract][Hide abstract] ABSTRACT: The history of the role of government in health care is briefly reviewed and more fully discussed in the United States since the establishment of Medicare 40 years ago. Data and other evidence of the unintended consequences of this historic event are presented, identifying thorny and onerous issues that government has created, showing failed attempts at band-aid solutions, and suggesting that our present health care system is in disarray and cannot be rectified by the "incrementalism" approach. The establishment of a high-level commission jointly endorsed by the President of the United States and Congress is recommended to consider and analyze scrupulously all the components of our health care complex and provide a "roadmap" toward achieving a universal health care system that is culturally acceptable, affordable, and of optimal quality while avoiding its administration and total control by an ultimately rigid and unwieldy governmental or insurance-industry bureaucracy.
The American Journal of Surgery 03/2006; 191(2):145-57. DOI:10.1016/j.amjsurg.2005.09.016 · 2.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Azygous venous system injuries are rare. Although not commonly classified as a thoracic great vessel, the azygous system manifests morbidity and mortality that is similar to that of other great vessel injuries.
Over a 40 year period, data were retrospectively collected and charts reviewed from a vascular injury database.
A total of 22 injuries to the azygous venous system were identified with 21 to the azygous vein and 1 to the hemiazygous vein. All were secondary to penetrating trauma, with 19 from gunshot wounds and 3 from stab wounds. Eight of 22 patients died for an overall mortality of 36%. All patients had associated injuries, with concomitant injury to the lung noted in all cases.
Injuries to the azygous venous system have a significant associated lethality. As an azygous venous injury is not typically the indication for operation, anterior incisions are often employed, making exposure difficult. In the majority of injured patients, the azygous system injury was found after excluding injuries to the heart, lung, and great vessels. A key finding in detecting these injuries through an anterior incision is continued hemorrhage of dark blood from a posterior location in the thoracic cavity. The azygous venous system should be considered early as a source of significant hemorrhage from the posterior mediastinum.
The Journal of trauma 03/2006; 60(2):357-62. DOI:10.1097/01.ta.0000202552.26628.84 · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although studies have ascertained that ten percent of soldiers killed in battle bleed to death from extremity wounds, little data exists on exsanguination and mortality from extremity injuries in civilian trauma. This study examined the treatment course and outcomes of civilian patients who appear to have exsanguinated from isolated penetrating extremity injuries.
Five and 1/2 years' data (Aug 1994 to Dec 1999) were reviewed from two Level I trauma centers that receive 95% of trauma patients in metropolitan Houston, TX. Records (hospital trauma registries, emergency medical system (EMS) and medical examiner data) were reviewed on all patients with isolated extremity injuries who arrived dead at the trauma center or underwent cardiopulmonary resuscitation (CPR) or emergency center thoracotomy (ECT).
Fourteen patients meeting inclusion criteria were identified from over 75,000 trauma emergency center (EC) visits. Average age was 31 years and 93% were males. Gunshot wounds accounted for 50% of the injuries. The exsanguinating wound was in the lower extremity in 10/14 (71%) patients and proximal to the elbow or knee in 12/14 (86%). Ten (71%) had both a major artery and vein injured; one had only a venous injury. Prehospital hemorrhage control was primarily by gauze dressings. Twelve (86%) had "signs of life" in the field, but none had a discernable blood pressure or pulse upon arrival at the EC. Prehospital intravenous access was not obtained in 10 patients (71%). Nine patients underwent ECT, and nine were initially resuscitated (eight with ECT and one with CPR). Those undergoing operative repair received an average of 26 +/- 14 units of packed red blood cells. All patients died, 93% succumbing within 12 hours.
Although rare, death from isolated extremity injuries does occur in the civilian population. The majority of injuries that lead to immediate death are proximal injuries of the lower extremities. The cause of death in this series appears to have been exsanguination, although definitive etiology cannot be discerned. Intravenous access was not obtainable in the majority of patients. Eight patients (57%) had bleeding from a site that anatomically might have been amenable to tourniquet control. Patients presenting to the EC without any detectable blood pressure and who received either CPR or EC thoracotomy all died.
The Journal of trauma 08/2005; 59(1):217-22. DOI:10.1097/01.TA.0000173699.71652.BA · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A succinct, historical review of developments in mechanical devices to assist the failing heart is provided.
A number of methods of mechanical devices to assist the failing heart are briefly assessed. Personal experimental and clinical studies of devices developed over several decades are presented.
Findings and data of devices used in assisting the failing heart, including those developed by the author, are analyzed.
On the basis of this review, the left ventricular assist device is believed to be the most effective. There is also reason to believe that the axial flow system has considerable advantages. This form of therapy has potentially great value for permanent use in some patients with intractable heart failure.
The Annals of thoracic surgery 07/2005; 79(6):S2228-31. DOI:10.1016/j.athoracsur.2005.03.029 · 3.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report and describe the design and the first clinical implantation of the DeBakey ventricular assist device (VAD) Child, a pediatric intracorporeal left ventricular assist device, in a 6-year-old girl. The risk-benefit of novel technologies in advanced heart failure and the lessons learned by our experience are important to consider in hopes that other centers (where this device is now available) may benefit.
The Journal of Heart and Lung Transplantation 04/2005; 24(3):331-7. DOI:10.1016/j.healun.2004.12.117 · 5.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Congestive heart failure poses a serious health risk to millions of Americans. Medical therapy for advanced stages of this condition has offered a minimal benefit and surgical treatment through transplantation is limited by the donor organ shortage. Although left ventricular assist devices may represent the future of therapy for this disease, the first generation of these pumps are limited by a number of factors that restrict their use to only the sickest of patients. The development and clinical use of the MicroMed DeBakey VAD represents a paradigm shift in the field of heart disease, supporting the notion that mechanical assistance can be achieved with continuous flow pumps. Axial flow devices, such as the DeBakey VAD, may open new doors for smaller patients and children, as well as improve the current standard of care for adults who require long-term circulatory support.
Expert Review of Medical Devices 04/2005; 2(2):137-40. DOI:10.1586/174344220.127.116.11 · 1.78 Impact Factor