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Biomedical subjects

N T Kouchoukos

Publications and source records attributed to N T Kouchoukos.

At least 55 records · Page 3Linked to original sources
PubMed1995

Transesophageal echocardiography and adult cardiac operations.

Transesophageal echocardiography (TEE) now is used widely as a monitoring technique during and after cardiac operations. Widespread adoption of the technique has provided a wealth of new information. This review analyzes the influence of TEE on the routine conduct of cardiac operations and on surgical decision making in specific areas. Its use in routine hemodynamic monitoring and problem solving, both intraoperatively and postoperatively, is discussed. Transesophageal echocardiography has a particular role in valve operations, in guiding and assessing the immediate results of mitral valve repair. It also has found application in the grading and operative management of the severely atheromatous aorta, the diagnosis and management of aortic dissection, and other aspects of surgery of the thoracic aorta. In addition, management in specialized areas, such as cardiopulmonary transplantation and the insertion and monitoring of ventricular assist devices, have also been helped by the information provided by TEE.

Adult↗
PubMed1995

Coronary artery disease in patients with type A aortic dissection.

The usefulness of preoperative coronary arteriography in patients with type A dissection of the aorta is controversial. To determine the prevalence of arteriosclerotic coronary artery disease in patients with type A dissection of the aorta, we reviewed our experience in 62 patients (42 with acute dissection and 20 with chronic dissection) who underwent operation between January 1, 1986, and December 31, 1993. Among 23 patients with acute dissection who underwent coronary arteriography, 8 (34.8%) had one or more coronary artery lesions causing a greater than 50% narrowing. Among 14 patients with chronic dissection who underwent coronary arteriography, 6 (42.9%) had one or more coronary artery lesions causing a greater than 50% narrowing. There were no fatal complications associated with coronary arteriography. Four patients with acute dissection and 6 patients with chronic dissection underwent coronary artery bypass grafting at the time of operative repair of the aortic dissection, with no operative deaths. On the basis of these findings and the success of combined coronary artery bypass grafting and aortic repair, we recommend that patients with an acute type A dissection who are in stable condition and all patients with a chronic type A dissection of the aorta should undergo preoperative coronary arteriography.

Acute Disease↗
PubMed1995

Thrombosis of mitral valve bioprostheses in patients requiring circulatory assistance.

Two patients with new mitral valve bioprostheses required implantation of Bio-Medicus centrifugal pumps (Bio-Medicus, Minneapolis, MN) for circulatory support and had evidence of prosthetic valve thrombosis 1 and 4 days later. Both patients died of thromboembolic complications despite surgical removal of the thrombus. Thrombosis is a rare early complication of bioprosthetic valves and in these cases was probably related to low transvalvular flow due to the use of circulatory assist devices. We discuss possible strategies for avoiding and managing this catastrophic complication.

Aged↗
PubMed1995

Quality initiatives and the power of the database: where we stand.

Many efforts to improve the quality of care focus on information drawn from databases. Such information can be very useful; however, the acquisition and analysis of data must be undertaken with caution. Six issues related to quality of care and the acquisition and analysis of data that pose problems for thoracic surgeons are the limitations and dangers of the right to know, the inadequacy of current databases, outcomes analysis and whether they help or hurt us, increased scrutiny of our practices, practice guidelines and the standards of care, and credentialing. To maximize the benefits of databases, physicians must participate in the process of data acquisition and analysis and the formation of practice guidelines. Speaking out against the misuse of incomplete or inaccurate data and supporting Society initiatives that address these concerns will help us as we strive to maintain a strong physician-patient relationship and to deliver optimal care to our patients.

Bias↗
PubMed1995

Profound systemic hypothermia inhibits the release of neurotransmitter amino acids in spinal cord ischemia.

Profound hypothermia induced with cardiopulmonary bypass has a protective effect on spinal cord function during operations on the thoracoabdominal aorta. The mechanism of this protection remains unknown. It has been proposed that the release of excitatory amino acids in the extracellular space plays a causal role in irreversible neuronal damage. We investigated the changes in extracellular neurotransmitter amino acid concentrations with the use of in vivo microdialysis in a swine model of spinal cord ischemia. All animals underwent left thoracotomy and right atrium-femoral artery cardiopulmonary bypass with additional aortic arch perfusion. Lumbar laminectomies were then done and microdialysis probes were inserted stereotactically in the anterior horn of the second and fourth segments of the lumbar spinal cord. The probes were perfused with artificial cerebrospinal fluid at a rate of 2 microliters/min and 15-minute samples were assayed by high-performance liquid chromatography. Group 1 animals (n = 6) underwent aortic clamping distal to the left subclavian artery and proximal to the renal arteries for 60 minutes at normothermia (37 degrees C) and group 2 animals (n = 5) were cooled to a rectal temperature of 20 degrees C before application of aortic clamps, maintained at this level during cardiopulmonary bypass until the aorta was unclamped, and then slowly rewarmed to 37 degrees C. Seven amino acids were studied, including two excitatory neurotransmitters (glutamate and aspartate) and five putative inhibitory neurotransmitters (glycine, gamma-aminobutyric acid, serine, adenosine, and taurine). Glutamate exhibited a threefold increase in extracellular concentration during normothermic ischemia compared with baseline values and remained elevated until 60 minutes after reperfusion. The increase in aspartate concentration was not significant. The extracellular concentrations of glycine and gamma-aminobutyric acid also increased significantly during ischemia and reperfusion. Hypothermia uniformly prevented the release of amino acids in the extracellular space. Glutamate levels remained significantly decreased even after rewarming to normothermia whereas glycine levels returned to baseline values. These results are consistent with a role for excitatory amino acids in the production of ischemic spinal cord injury and suggest that the mechanism of hypothermic protection may be related to decreased release of these amino acids in the ischemic spinal cord.

Analysis of Variance↗
PubMed1995

Hypothermic bypass and circulatory arrest for operations on the descending thoracic and thoracoabdominal aorta.

BACKGROUND: Hypothermic cardiopulmonary bypass with intervals of circulatory arrest is a useful adjunct during operations on the descending thoracic aorta and distal aortic arch when severe aortic disease precludes placement of clamps on the aorta. Hypothermia also has a marked protective effect on spinal cord function during periods of aortic occlusion. METHODS: Fifty-one patients (age range, 22 to 79 years) with descending thoracic or thoracoabdominal aortic disease had resection and graft replacement of the diseased aortic segments using hypothermic cardiopulmonary bypass and intervals of circulatory arrest in situations where the location, extent, or severity of disease precluded placement of clamps on the proximal aorta (8 patients) or (in 43 patients) when extensive thoracic (11) or thoracoabdominal (32) aortic disease was present and the risk for development of spinal cord ischemic injury and renal failure was judged to be increased. Patent intercostal (below T-6) and upper lumbar arteries were attached to the graft whenever possible. RESULTS: Thirty-day mortality was 9.8% (5 patients). Paraplegia occurred in 2 and paraparesis in 1 of the 46 30-day survivors (6.5%). Among the 27 operative survivors with thoracoabdominal aneurysms, paraplegia occurred in 1 of 12 with Crawford type I (8%), 0 of 10 with type II, and 1 of 5 with type III aneurysms (20%). Paraplegia occurred in none of the 12 patients with aortic dissection and in 2 of the 15 patients with degenerative aneurysms. Renal failure requiring dialysis occurred in 1 (2.2%) of the 46 30-day survivors. CONCLUSIONS: Hypothermic circulatory arrest is a valuable adjunct for the treatment of complex aortic disease involving the aortic arch and thoracoabdominal aorta. In patients with thoracoabdominal aneurysms, its use has been associated with a low incidence of renal failure and an incidence of paraplegia/paraparesis in traditionally high-risk subsets (type I and II aneurysms, aortic dissection), which may be less than that observed with other surgical techniques.

Adult↗
PubMed1994

Replacement of the aortic root with a pulmonary autograft in children and young adults with aortic-valve disease.

BACKGROUND: The optimal substitute for severely diseased aortic valves in children and young adults is unknown. The use of a mechanical prosthesis requires permanent treatment of the patient with anticoagulants and is associated with thromboembolic and hemorrhagic complications. Aortic-valve allografts and porcine bioprostheses, which do not necessitate anticoagulant therapy, may deteriorate and have limited durability. METHODS: We therefore evaluated the use of the autologous pulmonary valve (i.e., the patient's own pulmonary valve) and the adjacent pulmonary artery as a replacement for the aortic valve and aortic sinuses in 33 patients. Five of the patients were from 8 to 16 years of age, and 28 were from 20 to 47 years of age. The pulmonary valve and the main pulmonary artery were used to replace the diseased aortic valve and the adjacent aorta. The coronary arteries were detached from the aorta and implanted into the pulmonary artery. The pulmonary valve and artery were replaced with a cryopreserved pulmonary allograft. RESULTS: There were no deaths during follow-up of up to 48 months (mean, 21 months). There were no episodes of infective endocarditis, and no reoperations on the aortic root were necessary. Also, there was no evidence on echocardiography of progressive dilatation of the autografts. With color-flow Doppler imaging, 22 patients were found to have only trivial regurgitation or none, 9 patients to have mild regurgitation, and no patients to have moderate or severe regurgitation across the autograft at the most recent follow-up visit. The mean peak velocity of flow across the autograft was 1.3 m per second (upper limit of normal, 1.8), indicating the absence of stenosis. One patient required reoperation for stenosis of the pulmonary allograft. CONCLUSIONS: Although the pulmonary-autograft procedure is more complex than simple aortic-valve replacement, it has been safely applied in selected patients, including young adults. Intermediate follow-up indicates satisfactory function of the autografts, with no dilatation or progressive valvular regurgitation. Pulmonary-root autografts may thus be the best available substitute for diseased aortic valves in children and young adults.

Adolescent↗
PubMed1994

Adjuncts to reduce the incidence of embolic brain injury during operations on the aortic arch.

Two adjunctive techniques for operations involving the aortic arch, retrograde perfusion of cold oxygenated blood through the superior vena cava and establishment of antegrade flow after hypothermic circulatory arrest, are described. These techniques should reduce or possibly eliminate the embolization of air and particulate matter into the cerebral circulation and may reduce the incidence of brain injury.

Aorta, Thoracic↗
PubMed1994

Dextrorphan inhibits the release of excitatory amino acids during spinal cord ischemia.

The release of excitatory amino acids, particularly glutamate, into the extracellular space plays a causal role in irreversible neuronal damage after central nervous system ischemia. Dextrorphan, a noncompetitive N-methyl-D-aspartate receptor antagonist, has been shown to provide significant protection against cerebral damage after focal ischemia. We investigated the changes in extracellular neurotransmitter amino acid concentrations using in vivo microdialysis in a swine model of spinal cord ischemia. After lumbar laminectomies were performed, all animals underwent left thoracotomy and right atrial-femoral cardiopulmonary bypass with additional aortic arch perfusion. Microdialysis probes were then inserted stereotactically into the lumbar spinal cord. The probes were perfused with artificial cerebrospinal fluid and 15-minute samples were assayed using high-performance liquid chromatography. Group 1 animals (n = 9) underwent aortic clamping distal to the left subclavian and proximal to the renal arteries for 60 minutes. Group 2 animals (n = 7) were treated with dextrorphan before application of aortic clamps, and during aortic occlusion and reperfusion. Five amino acids were studied, including two excitatory neurotransmitters (glutamate and aspartate) and three putative inhibitory neurotransmitters (glycine, gamma-amino-butyric acid, and serine). Somatosensory-evoked potentials and motor-evoked potentials were monitored. Glutamate exhibited a threefold increase in extracellular concentration during normothermic ischemia compared with baseline values and remained elevated until 60 minutes after reperfusion. In animals treated with dextrorphan, glutamate concentrations decreased to one-third of baseline levels before aortic clamping and remained unchanged during ischemia and reperfusion. There was early loss of somatosensory-evoked potentials and motor-evoked potentials during ischemia in group 1 animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1994

Managed care involvement by cardiovascular specialists: prevalence, attitudes and influence on practice.

OBJECTIVES: The purpose of this study was to determine the involvement in and attitudes toward managed care by cardiovascular specialists and the influence of such programs on their practices. BACKGROUND: No in-depth study has measured the impact of managed care on cardiovascular specialists. Therefore, we conducted a mail survey to determine the prevalence of managed care arrangements among cardiovascular specialists and variations among pediatric and adult cardiologists and cardiovascular surgeons; the types of managed care arrangements in which cardiovascular specialists are engaged; the reasons why those not participating in managed care have chosen not to do so; and the general attitudes among cardiovascular specialists with regard to various aspects of managed care. In addition, we evaluated the impact of managed care among several aspects of cardiovascular practice. METHODS: A questionnaire was mailed in the spring of 1993 to 4,577 practicing, domestic, American College of Cardiology (ACC) members selected at random from within each primary cardiovascular specialty group (adult cardiologists, pediatric cardiologists and cardiovascular surgeons). Additional data concerning practice characteristics were cross tabulated using results from the 1992 ACC membership profile survey. RESULTS: In total, 1,961 of the 4,577 members responded to the survey, representing a 43% response rate. Of all survey respondents, 76% reported entering into at least one relationship with a health maintenance organization (HMO) or preferred provider organization (PPO). Of those not participating in managed care arrangements, the most frequently mentioned reason was "concern over the quality of care." This reason was cited by 51% of those not entering into HMO relationships and 41% of those not participating in PPOs. The majority of respondents indicated that they do not strongly object to the gatekeeper approach to managing nonemergent patients, although more than half indicated concern that gatekeepers may not be appropriate in the management of cardiac emergencies. In addition, cardiovascular specialists report that under managed care, referrals have not increased, income has decreased, and managed care formularies have not substantially affected their ability to prescribe appropriate medication to their patients. CONCLUSIONS: Despite concerns over the quality of care and contract requirements and general philosophical opposition of cardiovascular specialists, most are becoming integrated into managed care environments.

Adult↗
PubMed1994

Hypothermic circulatory arrest for cerebral protection during combined carotid and cardiac surgery in patients with bilateral carotid artery disease.

OBJECTIVE: The authors evaluated the protective effect of hypothermic circulatory arrest for patients with bilateral carotid artery disease who underwent cardiac surgical procedures. SUMMARY BACKGROUND DATA: Severe bilateral carotid artery disease coexisting with cardiac disease that requires surgical treatment is associated with a substantial incidence of stroke after operations that require cardiopulmonary bypass. The optimal method of management of patients with these coexisting conditions is not established clearly. Because hypothermia has a protective effect on neural and myocardial tissue during cardiac operations, a protocol employing profound hypothermia and a period of circulatory arrest was evaluated in a group of patients who underwent combined carotid and cardiac surgery who were considered to be at increased risk for the development of stroke. METHODS: Fifty patients with bilateral carotid artery disease, including 24 patients with high-grade unilateral stenosis and contralateral occlusion and 6 patients with 80% to 99% bilateral stenosis, underwent combined carotid endarterectomy and cardiac surgery (coronary artery bypass grafting in all 50 patients and additional procedures in 8 patients). Profound systemic hypothermia (15 C) was instituted, and the carotid endarterectomy was performed during a period of circulatory arrest that averaged 30 minutes. The cardiac procedure was performed during the periods of cooling and rewarming. RESULTS: The 30-day mortality rate was 6% (3 patients). There were no early postoperative strokes or reversible ischemic neurologic deficits. There have been seven late deaths in the postoperative period, which extends to 54 months. None of these deaths were caused by stroke. There has been one late stroke, which occurred in the distribution of the unoperated carotid artery. CONCLUSIONS: This technique provides adequate protection of the brain and myocardium during combined carotid and cardiac surgical procedures and appears to reduce the frequency of stroke in the high-risk subgroup of patients with bilateral carotid artery disease.

Aged↗
PubMed1994

Management of the severely atherosclerotic aorta during cardiac operations.

Embolization of atheroma from the ascending aorta is a major cause of stroke following cardiac surgery. We evaluated a protocol for intraoperative detection and treatment of the severely atherosclerotic ascending aorta which included epiaortic ultrasonographic scanning and resection and graft replacement of the involved segment using hypothermic ischemic arrest. During an 81-month interval, 47 patients 50 years of age and older (mean age 71 years) who underwent coronary artery bypass grafting had resection and graft replacement of the ascending aorta. This represented approximately 2% of the patients in this age group who had cardiac operations during this interval. Nineteen patients (40%) required additional procedures. The 30-day mortality rate was 4.3% (2 patients). Both patients died of myocardial failure. None of the 45 surviving patients sustained a perioperative stroke. There have been no strokes or transient ischemic events in the follow-up period, which extends to 72 months (mean 21 months). While this technique for management of the severely atherosclerotic aorta could be considered radical, it was associated with lower mortality and stroke rates than those that were observed in patients with moderate or severe atherosclerosis in whom only minor modifications in technique were made to avoid embolization of atheroma. Resection and graft replacement during a period of hypothermic circulatory arrest is currently our preferred method of treatment for the severely atherosclerotic aorta during cardiac surgery.

Aged↗
PubMed1994

Atherosclerosis of the ascending aorta. Prevalence and role as an independent predictor of cerebrovascular events in cardiac patients.

BACKGROUND AND PURPOSE: The cause of cerebral and peripheral embolism remains undetermined in a significant number of patients. An atherosclerotic thoracic aorta has thus far been considered to be an uncommon one. METHODS: To define the potential role of the ascending thoracic aorta as an embolic source, intraoperative ultrasonic aortic imaging was performed in 1200 of 1334 consecutive patients aged 50 years and older who were undergoing cardiac surgery. Patients were divided into two groups according to the results of the ultrasound study in terms of presence or absence of atherosclerotic disease. The prevalence of previous neurological events in the two groups was characterized and compared. RESULTS: Ascending aortic atherosclerosis was present in 231 (19.3%) of the patients studied. Patients in this category were older (P < .0001). A higher percentage of them were smokers (P < .0001) compared with patients with less severe disease. Coronary artery disease was more extensive (P = .012), and a higher percentage of these patients had a history of peripheral vascular disease (P < .0001). Univariate analysis of the subjects with (n = 158) and without (n = 1042) previous neurological events indicated that age, body mass index, atrial fibrillation, hypertension, and atherosclerosis of the ascending aorta were associated significantly with previous occurrence of a cerebrovascular accident. For the group as a whole, multiple logistic regression analysis demonstrated that hypertension (odds ratio, 1.81; P = .002), atherosclerosis of the ascending aorta (odds ratio, 1.65; P = .013), and atrial fibrillation (odds ratio, 1.54; P = .060) were significantly and independently associated with the occurrence of previous neurological events. CONCLUSIONS: Atherosclerosis of the ascending aorta is an independent risk factor for cerebrovascular events. An atherosclerotic ascending aorta may represent a potential source of emboli or may be a marker of generalized atherosclerosis.

Age Factors↗
PubMed1993

Strategy for the reduction of stroke incidence in cardiac surgical patients.

Atherosclerosis of the ascending aorta (AAA) and severe carotid artery disease are risk factors for stroke in cardiac surgical patients. Twelve hundred of a consecutive series of 1,334 patients 50 years of age or older having a cardiac operation were screened for the presence of AAA by intraoperative ultrasonographic scanning and for the presence of carotid artery occlusive disease (791 of 798 patients > or = 65 years of age and younger symptomatic patients) by carotid duplex scanning. Coronary artery disease was present in 88% of the patients. Patients with moderate or severe AAA (n = 231; 19.3% of the total) were treated by ascending aortic replacement (n = 27) or by modified, less extensive techniques (n = 168) to avoid the atherosclerotic areas. Thirty-three patients had combined carotid endarterectomy and cardiac operation. Thirty-day mortality and stroke rates for the 1,200 patients were 4.0% and 1.6%, respectively. The stroke rate was low (1.1%) among the 969 patients with no or mild AAA. It was zero among 27 patients with moderate or severe AAA who had ascending aortic replacement and among the 33 patients who had carotid endarterectomy. The stroke rates were higher for 111 patients with moderate or severe ascending aortic disease who had only minor interventions (6.3%) and for 16 patients with severe carotid artery disease who did not have carotid endarterectomy (18.7%). Screening for AAA and carotid artery disease and aggressive surgical treatment of moderate or severe AAA and severe or symptomatic carotid artery disease appears to reduce the frequency of stroke in older cardiac surgical patients.

Aged↗
PubMed1993

Renal dysfunction and intravascular coagulation with aprotinin and hypothermic circulatory arrest.

High-dose aprotinin was used in 20 patients undergoing primary or repeat operations on the thoracic or thoracoabdominal aorta using cardiopulmonary bypass and hypothermic circulatory arrest. The activated clotting times immediately before the establishment of hypothermic circulatory arrest exceeded 700 seconds in all but 1 patient. Three patients (15%) required reoperation for bleeding. Seven patients died during hospitalization, and 5 had postmortem examination. Platelet-fibrin thrombi were present in multiple organs including the coronary arteries of 4 patients with myocardial infarction or failure, the pulmonary arteries of 2 patients, 1 of whom died of acute right ventricular failure, the brains of 2 patients who sustained a stroke, and the kidneys of 4 patients, 3 of whom had development of renal dysfunction. Renal dysfunction occurred in 13 patients (65%), and all were 65 years of age or older. Five of these patients required hemodialysis. Among 20 age-matched patients who had similar operations without aprotinin, there was one hospital death (5%) from myocardial infarction, and renal dysfunction developed in 1 patient (5%), who did not require dialysis. None of these 20 patients required reoperation for bleeding. Although aprotinin has been shown to reduce blood loss in patients having cardiac operations employing cardiopulmonary bypass, this benefit was not attained in this group of patients with thoracic aortic disease in whom hypothermic circulatory arrest was used. Use of aprotinin in elderly patients undergoing these procedures was associated with an increased risk of renal dysfunction and failure, and of myocardial infarction and death.

Aged↗