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Biomedical subjects

N T Kouchoukos

Publications and source records attributed to N T Kouchoukos.

At least 73 records · Page 4Linked to original sources
PubMed1993

Profound systemic hypothermia protects the spinal cord in a primate model of spinal cord ischemia.

Spinal cord ischemia with resultant paraplegia or paraparesis remains an important clinical problem after operations on the thoracoabdominal aorta. Because hypothermia has a protective effect on ischemic neural tissue, we developed a baboon model of spinal cord ischemia to simulate the situation encountered clinically for resection of aneurysms of the thoracoabdominal aorta and to determine whether profound hypothermia produced by hypothermic cardiopulmonary bypass has a protective effect on spinal cord function. After cardiopulmonary bypass was established, the aorta was clamped distal to the left subclavian artery and proximal to the renal arteries for 60 minutes. Group I animals (n = 9) underwent aortic clamping at normothermia (37 degrees C), and group II animals (n = 9) were cooled to a rectal temperature of 15 degrees C before aortic clamping and underwent cardiopulmonary bypass at this temperature until the aorta was unclamped. Of the eight operative survivors in group I, six animals were paraplegic and two were paraparetic, whereas all six group II animals that survived the procedure were neurologically intact (p = 0.0002). The protective effect of hypothermia was associated with blunting of the hyperemic response of spinal cord blood flow (determined by the radioactive microsphere technique) in the lower thoracic and the lumbar segments of the spinal cord after unclamping of the aorta. Profound hypothermia produced by hypothermic cardiopulmonary bypass may be an effective method of protection of the spinal cord in patients undergoing repair of aneurysms of the thoracoabdominal aorta and may reduce the prevalence of ischemic injury to the spinal cord.

Animals↗
PubMed1993

When and how to include arch repair in patients with acute dissections involving the ascending aorta.

The arch should be included in the repair in patients with acute aortic dissection involving the ascending aorta when (1) the intimal tear is in the arch, (2) rupture of the arch has occurred, (3) the outer wall of the false channel in the arch is tenuous, and (4) the inner wall of the false channel is fragmented. A technique has evolved for patients with acute aortic dissection involving the arch that seems to minimize the difficulties and risks of including the arch, when indicated. Its place will best be determined by additional, prospective, and preferably multi-institutional testing.

Acute Disease↗
PubMed1992

Intraaortic balloon counterpulsation: patterns of usage and outcome in cardiac surgery patients.

Between January 1, 1986, and May 6, 1991, 7,884 cardiac surgical procedures requiring cardiopulmonary bypass were performed at our institution, including 672 (9.8% of adult procedures) performed in 669 patients that were associated with preoperative (n = 240), intraoperative (n = 353), or postoperative (n = 79) use of an intraaortic balloon pump. The mean age of recipients was 65.3 years (range, 16 to 89 years). Intraaortic balloon pump usage increased during the study period from 6.4% of patients (83/1,298) in 1986 to 12.7% of patients (169/1,333) in 1990. The relative distribution between preoperative (mean, 35.7%), intraoperative (52.5%), and postoperative (11.8%) insertion remained nearly constant during the study period. The overall operative (30-day) mortality for patients with preoperative, intraoperative, or postoperative insertion of the intraaortic balloon pump was 19.6%, 32.3%, and 40.5%, respectively (X2 = 16.4; p less than 0.001). Although use of the intraaortic balloon pump in the intraoperative and postoperative settings is accompanied by a favorable outcome in most patients, the high associated mortality suggests the need for earlier use of the intraaortic balloon pump or other supportive measures such as the ventricular assist device.

Angina, Unstable↗
PubMed1992

Surgery.

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Cardiovascular Diseases↗
PubMed1992

Transesophageal echocardiography predicts successful withdrawal of ventricular assist devices.

Transesophageal echocardiography has been found to be an effective technique for the real-time assessment of myocardial and valvular function in postoperative patients. To determine the value of transesophageal echocardiography in patients with mechanical assist devices, we performed daily, bedside transesophageal echocardiography on 16 patients with right (n = 3), left (n = 1), or biventricular assist devices (n = 12). We obtained four-chamber and short-axis views in all patients. Valvular function and the presence of left-to-right shunts were evaluated by means of color flow Doppler imaging. During the echocardiographic study ventricular assist device flow was diminished to less than 1.5 L/min, and inotropic agents (dobutamine or epinephrine) were given to assess ventricular reserve. Changes in day-to-day ventricular function were assessed in comparisons made by two observers (one unaware of the study sequence) using a semiquantitative method for wall motion analysis. The left ventricular wall motion scores in the patients successfully weaned from left or biventricular assist devices (n = 5) improved (14.2 +/- 1.6 versus 8.2 +/- 1.5, p < 0.0001). The scores did not improve in patients who remained dependent on the devices (n = 8). Two patients with only right ventricular assist devices were successfully weaned after documentation of improvement of right ventricular function by transesophageal echocardiography. Transesophageal echocardiography documented a clot compressing the heart in three patients; intracavitary thrombi were seen in two other patients. Marked hemodynamic improvement occurred after surgical decompression. In conclusion, transesophageal echocardiography is a safe, effective method for the assessment of ventricular function of patients on ventricular assist device support. In addition, it allows one to assess valvular function and the presence or absence of impaired ventricular filling.

Adult↗
PubMed1992

Management of the severely atherosclerotic ascending aorta during cardiac operations. A strategy for detection and treatment.

Embolization of atheroma from the ascending aorta is a principal cause of stroke after cardiac operations. We have previously shown that intraoperative ultrasonographic scanning of the aorta rapidly, safely, and accurately identifies atheromatous disease in the ascending aorta. Intraoperative ultrasonography of the ascending aorta was performed in 500 of a consecutive series of 540 patients 50 years of age or older (mean 68 years) who underwent a variety of cardiac operations. Eighty-nine percent required bypass grafting. Sixty-eight patients (13.6% of the total) with a mean age of 72 years (range 55 to 85 years) had significant atheromatous disease in the ascending aorta and were considered to be at increased risk for embolization. Palpation identified the atheromatous disease in only 26 (38%) of these patients and underestimated its severity. A total of 168 modifications in the standard techniques for cannulation and clamping of the aorta were implemented in the 68 patients (mean 2.5 per patient) and included alterations in the sites of aortic cannulation (50 patients), aortic clamping (54 patients), attachment of the vein grafts (35 patients), and cannulation for infusion of cardioplegic solution (29 patients). Ten patients with severe diffuse atheromatous disease underwent graft replacement of the ascending aorta with hypothermic circulatory arrest without aortic clamping. Fourteen patients with symptoms or with high-grade carotid artery occlusive disease were treated by concomitant carotid endarterectomy. Thirty-day mortality for the entire group was 3.4% (17 patients). Permanent neurologic deficits occurred in five (1.0%) of the patients in the entire group but in none of the 68 patients with significant atheromatous disease in whom modifications in technique were used. One patient in the latter group had a reversible ischemic neurologic deficit. Modification of standard cannulation and clamping techniques based on ultrasonography may reduce the frequency of stroke related to atheromatous embolization.

Aged↗
PubMed1992

Preoperative carotid artery screening in elderly patients undergoing cardiac surgery.

The role of preoperative screening for carotid artery disease in elderly patients undergoing cardiac surgical procedures is not clearly established. This prospective study was designed to determine the prevalence of carotid disease in this population and to identify preoperative risk factors for carotid artery stenosis. During a 54-month interval, 1087 patients of a consecutive series of 1184 patients 65 years of age and older who underwent cardiac surgical procedures (91% had coronary artery disease) were evaluated before operation with carotid duplex ultrasonography. The prevalence of disease was 17.0% for 50% or greater stenosis and 5.9% for 80% or greater stenosis. With use of a stepwise, logistic regression model of 12 preoperative variables, five variables were found by multivariate analysis to be significant (p less than or equal to 0.05) predictors of 80% or greater stenosis: female sex, peripheral vascular disease, history of transient ischemic attack or stroke, smoking history, and left main coronary artery disease. If all patients with at least one risk factor were screened, then this model predicts that 95% of patients with 80% or greater stenosis and 91% of patients with 50% or greater stenosis would be identified before operation. The probability of carotid disease in a given patient can also be estimated (range, 5% to 65%). Carotid endarterectomy combined with cardiac surgical procedures was performed on 46 patients who were either symptomatic (16) or had 80% or greater stenosis (30). The overall stroke rate for the 1087 patients was 2.0% (22 patients), and the 30-day mortality rate was 5.2% (56 patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Postcardiotomy mechanical circulatory support in the elderly.

The role of mechanical circulatory support after cardiac operations in elderly patients is not clearly established. Between November 1985 and July 1989, 18 patients 65 years of age or older (mean age, 71 years; range, 65 to 82 years) were treated after cardiotomy with a centrifugal vortex or pneumatic mechanical ventricular assist device. This group comprised 1.9% of the 926 patients 65 years of age or older undergoing cardiac surgical procedures and 69% of the 26 patients requiring postcardiotomy support during this interval. Before institution of mechanical support, all patients were receiving maximal inotropic support and 16 patients had intraaortic balloon pumps inserted. Univentricular support was used in 9 patients (6 left, 3 right) and biventricular support in 9 patients. The mean duration of support was 45 hours (range, 8 to 118 hours). Twelve patients (67%) were successfully weaned, 8 (44%) were discharged from the hospital, and 6 (33%) remain alive 11 to 31 months postoperatively. Four of the 6 survivors are in New York Heart Association class I, 1 is in class II, and 1 is in class IV. The Combined Registry for ventricular assist device support has recently reported an overall survival rate of 12% in patients 65 to 70 years of age and 6% in those older than 70 years. Our results are comparable with those reported for younger patients and justify the use of postcardiotomy ventricular assist device support in the elderly.

Acute Kidney Injury↗
PubMed1991

Sixteen-year experience with aortic root replacement. Results of 172 operations.

During a 16-year interval ending in October 1990, 168 patients underwent 172 aortic root replacements. Thirty patients (18%) had Marfan syndrome. Annuloaortic ectasia (81 patients) and aortic dissection (63 patients) were the principal indications for operation. Twenty-seven patients (16%) had previous operations on the ascending aorta or aortic valve. The hospital mortality rate was 5% and the duration of cardiopulmonary bypass was the only significant independent predictor of early death (p = 0.017). Major modifications in technique were made in 1981, when the inclusion/wrap technique employing a composite graft (used in the first 105 procedures) was abandoned in favor of an open technique (used in 51 procedures), and in 1988, when aortic allografts and pulmonary autografts were introduced for selected conditions (reoperations, dissection, endocarditis, isolated aortic valve disease) in 16 patients. The mean duration of follow-up was 81 months. Forty-six patients were followed for more than 10 years. The actuarial survival rate was 61% at 7 years and 48% at 12 years. No significant difference in survival rate was observed between the patients with annuloaortic ectasia and aortic dissection, or between the inclusion/wrap and open techniques. However the frequency of pseudoaneurysm formation at suture lines and the frequency of reoperations on the ascending aorta and aortic valve were less with the open technique. The actuarial freedom from thromboembolism for the 152 patients with prosthetic valves was 82% at 12 years. One early and one late death occurred among the 16 patients with allograft or autograft root replacement. Anticoagulant therapy was not used in these patients and no thromboembolic episodes occurred in the follow-up period (mean, 7 months). The satisfactory results observed with extended follow-up support the continued use of the composite graft technique as the preferred method of treatment for patients with annuloaortic ectasia, persistent aneurysms of the sinuses of Valsalva following previous operations, and for patients with ascending aortic dissection who require aortic valve replacement. The availability of aortic root allografts and the perfection of techniques for safe implantation of the autologous pulmonary root into the aortic position have broadened the indications for aortic root replacement.

Actuarial Analysis↗
PubMed1991

Surgery.

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Cardiac Surgical Procedures↗
PubMed1991

Aortic and vascular surgery.

Diagnosis and treatment of thoracic vascular disease remain difficult problems for the clinician. These pathologic conditions often result in significant morbidity and mortality. Currently, published series document long-term treatment results and allow investigators to analyze both pre- and postoperative predictors of outcome. This review outlines some of the many significant publications over the past 12 months dealing with these disorders.

Aorta, Thoracic↗
PubMed1991

Intraoperative ultrasonographic evaluation of the ascending aorta in 100 consecutive patients undergoing cardiac surgery.

Dislodgement of atheromatous plaque from the ascending aorta following manipulation is one of the principal causes of stroke following cardiac surgery. To define clinical correlates that predict the presence of severe atherosclerosis, we performed ultrasonographic evaluation of the ascending aorta at the time of cardiac surgery in 100 consecutive patients. The ascending aorta was divided into three equal segments for analysis, and the severity of atherosclerosis was determined as mild when intimal thickening (less than 3 mm) was localized to one segment, moderate when intimal thickening (greater than 3 mm) was present in one or two segments, and severe when intimal thickening (greater than 3 mm) was present throughout the entire circumference in all three segments. Thirty-eight percent of the studies were normal, mild atherosclerosis was present in 33%, moderate atherosclerosis in 19%, and severe atherosclerosis in 10% of the patients. Palpation of the ascending aorta to detect atherosclerosis significantly underestimated the presence (p less than 0.001) and severity (p less than 0.001) of atherosclerosis when compared with ultrasonography. Age, carotid artery disease, diabetes, gender, smoking, and hypertension were evaluated for their ability to discriminate between normal and severely atherosclerotic aortas. Stepwise logistic regression analysis showed age (p less than 0.02) and diabetes (p less than 0.04) to be significant independent predictors of the presence of severe atherosclerosis in the ascending aorta. Based on the ultrasonographic findings, the operative procedure was altered to reduce the risk of embolization in 17% of the patients. We conclude that high-resolution images of the ascending aorta for identification of atherosclerosis can be obtained by ultrasonography.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Risks of bilateral internal mammary artery bypass grafting.

Although use of one internal mammary artery (IMA) for coronary artery bypass grafting does not appear to be associated with increased risk, the results with both IMAs are less certain; the potential for a higher incidence of sternal wound infection as a result of devascularization of the sternum is a major concern. During a 42-month interval ending July 1988, 1,566 patients had coronary artery bypass grafting alone or in combination with other procedures: 633 received only vein grafts, 687 had unilateral IMA grafting, and 246 had bilateral IMA grafting. The IMA patients were younger, were more often male, had better cardiac function, and underwent fewer emergent, urgent, or combined procedures than the patients receiving vein grafts (p less than 0.05). Thirty-day mortality was lower among the IMA patients (unilateral IMA group, 2.8%; bilateral IMA group, 3.7%; and vein graft group, 7.9%; p = 0.001). With the exception of sternal wound problems, occurrence rates for postoperative complications among the IMA patients did not differ significantly from or were lower (p less than 0.05) than those among the patients with vein grafts. Sternal infections occurred with greater frequency among the bilateral IMA patients (6.9%) than among the unilateral IMA (1.9%) or vein graft (1.3%) patients (p = 0.001). By univariate analysis, obesity, diabetes, bilateral IMA grafting, and need for prolonged (greater than 48 hours) mechanical ventilation were associated with a significantly higher incidence of sternal infection (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Use of single internal mammary artery grafts in older patients.

The indications for use of the internal mammary artery as a coronary bypass conduit in older patients are not clearly established. Between January 1985 and December 1988, 786 patients received single internal mammary artery grafts alone (717) or in conjunction with other procedures (69). Of these patients, 341 were 65 years of age or older (mean, 69.3 years). This group was compared with those patients less than 65 years of age (mean, 56.2 years). There were no significant differences between the two groups in the incidence of diabetes mellitus; the number of distal coronary anastomoses; left ventricular wall motion score; the frequency of isolated bypass procedures, reoperations, or emergent operations; or the durations of aortic clamping and cardiopulmonary bypass. The older group contained more women (34.9% versus 20.7%) and more patients with left main coronary artery disease (15.5% versus 9.4%) (p less than 0.01). No significant differences in the frequency of reoperation for hemorrhage, perioperative infarction, neurological deficits, requirements for intra-aortic balloon pumping, sternal wound infections, necessity for prolonged ventilatory support, or 30-day mortality (2.7% versus 3.2%) were observed. The length of postoperative hospitalization was greater in the older group (11.8 versus 10.2 days) (p = 0.02). Blinded histological examination of biopsies from 61 internal mammary artery grafts (34 patients less than 65 years, 27 patients greater than or equal to 65 years) showed no significant differences in luminal area or wall thickness. No significant degenerative changes were observed in either group. We conclude that the use of the internal mammary artery for bypass grafting in older patients is safe and may provide long-term benefit.

Age Factors↗