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Biomedical subjects

S M Lindenauer

Publications and source records attributed to S M Lindenauer.

At least 19 recordsLinked to original sources
PubMed1996

Abdominal aortic aneurysm repair in Veterans Affairs medical centers.

PURPOSE: This study was performed to define outcomes after abdominal aortic aneurysm (AAA) repair in Veterans Affairs (VA) medical centers during fiscal years 1991 through 1993. METHODS: With VA patient treatment file data, patients were selected from diagnosis-related groups 110 and 111 and were then classified in a patient management category. In the categories of repair of nonruptured and ruptured AAA, mortality and postoperative complication rates were defined for patients who underwent AAA repair in VA medical centers during the 3-year study period. RESULTS: Hospital mortality rates were 4.86% (166 of 3419) after repair of nonruptured AAA and 47.0% (126 of 268) after repair of ruptured AAA (p<0.001). Of 292 deaths after AAA repair, 136 (43.2%) followed repair of ruptured AAA, even though ruptured AAA comprised only 7.3% of total AAA surgical volume. AAA repairs were performed at 116 VA medical centers, with 31.8+/-23.1 (range, 1 to 140) procedures performed at each center. Although many lower-volume centers had excellent results, centers that performed >or=32 AAA repairs tended to have lower in-hospital mortality rates after repair of nonruptured AAA than those that performed <or=31 procedures (4.2%+/-3.5% compared with 6.7%+/-7.8%;p<0.05). Poisson regression analysis revealed an inverse relationship between the volume of AAA repairs and individual hospital mortality (p=0.001) and a direct relationship between illness severity and hospital mortality (p=0.008). The proportion of ruptured AAAs treated in a hospital was also directly related to individual hospital mortality rates (p<0.005). Postoperative complications were associated with an increased hospital mortality rate (11.7% with complication compared with 6.5% without; p<0.0001) and length of stay (23.6+/-17.1 days compared with 18.0+/-12.4 days; p<0.0001). In a logistic regression model, increased mortality rates after AAA repair were associated with hospital type (adjusted odds ratio [OR]=0.6), increasing age (OR=1.1), patient management category severity score (OR=2.2), hemorrhage (OR=2.3), myocardial infarction (OR=2.6), disseminated intravascular coagulation (OR=4.7), AAA rupture (OR=6.0), postoperative shock (OR=10.7), cardiopulmonary arrest (OR=15.4), central nervous system complications (OR=16.0) and urologic complications (OR=2.4). CONCLUSIONS: Mortality rates after AAA repair in VA hospitals were comparable with those previously reported in other large series. Outcomes for veterans with AAA may improve by referring patients eligible for elective repair to VA medical centers with a greater operative volume or to lower-volume centers that have had excellent results.

Age Factors↗
PubMed1993

Effects of lumbar sympathectomy on canine transcutaneous oxygen tension.

Augmentation of cutaneous blood flow by postganglionic lumbar sympathectomy may not reflect an increase in nutritive vascular supply to the dermal tissues. Transcutaneous oxygen tension (TcPO2) was compared with radionuclide microsphere determination of dermal microcirculation in a hind limb sympathectomy model in 20 dogs. After 90 minutes the TcPO2 was greater in the sympathectomized limbs than in the contralateral limbs (125 mm Hg versus 114 mm Hg, p < or = 0.05). In contrast, microsphere-determined paw dermal capillary flow declined in sympathectomized limbs (4.9 ml/min/100 gm versus 11.8 ml/min/100 gm, p < or = 0.05). Decreases in the TcPO2/venous PO2 ratio correlated with sympathectomy-induced increases in total limb blood flow (r = 0.60; p < or = 0.001), reflecting less efficient oxygen extraction. These observations confirm the lack of enhancement of tissue oxygen delivery by sympathectomy because of the associated dilation of cutaneous arteriovenous shunts.

Animals↗
PubMed1991

Clinical characteristics and surgical management of vascular complications in patients undergoing cardiac catheterization: interventional versus diagnostic procedures.

The purpose of this report is to define the clinical characteristics and outcome of surgical management of vascular complications after interventional cardiac catheterization and to contrast them to those after diagnostic cardiac catheterization. From October 1985 to December 1989, 101 patients were treated for 106 vascular complications after 1866 interventional and 5046 diagnostic cardiac catheterizations at the University of Michigan Medical Center. Interventional catheterizations resulted in 69 vascular complications in 64 patients (frequency 3.4%). The most common interventions included coronary angioplasty (34), of which 10 required percutaneous partial cardiopulmonary bypass, intraaortic balloon pump placement (14), and aortic valvuloplasty (11). Interventional catheter-related complications included hemorrhage (33), arterial thrombosis (18), pseudoaneurysm formation (12), catheter embolization (2), thromboembolism (2), as well as arteriovenous fistula, pseudoaneurysm, and arterial dissection (1 each). Fifteen of these 69 patients (24%) had suffered acute myocardial infarction just before their catheterization. Surgical repair was performed under local anesthesia in 70% of patients. Major vascular reconstructions were required in 9% of patients. Three percent of the involved lower extremities had to be amputated because of complications occurring after arterial puncture. Eight percent of the patients incurring vascular complications after interventional procedures died after operation. Diagnostic catheterizations resulted in 37 vascular complications in 37 patients (frequency 0.7%). In contrast to diagnostic cardiac catheterization, vascular complications after interventional cardiac catheterization occurred more frequently, were most often due to hemorrhage at the vascular access site, and occurred in high-risk, critically ill patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Arterial aneurysms in children: clinicopathologic classification.

Thirty-one arterial macroaneurysms in 23 pediatric-aged patients (16 boys and 7 girls) were treated at the University of Michigan. The average age at time of diagnosis was 10.2 years (range 6 months to 18 years). Vessels involved the aorta (4), as well as hepatic (1), splenic (2), gastroepiploic (1), renal (12), iliac (1), superficial femoral (4), popliteal (1), brachial (1), radial (2), and ulnar (2) arteries. Twelve children exhibited overt clinical manifestations including presence of a mass (7), local pain (3), hematemesis (1), and painless obstructive jaundice (1). Eleven children had asymptomatic lesions. Aneurysm existence was confirmed by arteriography or operation. All but one child underwent surgical therapy, with 20 long-term survivors (mean follow-up 3.5 years). One operative death occurred and one death occurred 6 years after surgery. This experience and a review of previously reported cases served as a basis for categorization of childhood aneurysmal disease as true aneurysms associated with (I) arterial infection, (II) giant-cell aortoarteritis, (III) autoimmune connective tissue disease, (IV) Kawasaki's disease, (V) Ehlers-Danlos syndrome or Marfan's syndrome, (VI) other forms of noninflammatory medial degeneration, (VII) arterial dysplasias, (VIII) congenital-idiopathic factors, as well as (IX) false aneurysms associated with extravascular events causing vessel wall injury or disruption. Knowledge of the varied clinicopathologic characteristics of arterial aneurysms in children is important in treating these patients.

Adolescent↗
PubMed1990

Artery, periarterial adipose tissue, and blood microbiology during vascular reconstructive surgery: perioperative and early postoperative observations.

The presence and clinical significance of bacteria in the arterial wall, periarterial adipose tissue, and blood samples acquired during elective vascular operations were assessed in this study. Specimens were obtained from a random series of 84 patients (56 men, 28 women) undergoing 75 primary and 9 secondary arterial reconstructions. Operations performed most frequently included abdominal aortic aneurysmectomy (42), aortofemoral bypass reconstruction (15), and lower extremity bypass surgery for occlusive disease (7). Perioperative antibiotics were administered to all but one patient. A sample of artery, adjacent adipose tissue, and blood were obtained for microbial analysis during the vascular anastomosis or arteriotomy. This yielded a total of 152 artery, 139 adipose tissue, and 129 blood samples for study. Each specimen was divided and placed in blood agar plates, thioglycolate broth, and brain-heart infusion broth. Tissues yielding growth of the same organism(s) in two or more different media were considered positive for the presence of bacteria. Bacteria were present in at least one of the three tissues studied in 32/84 patients (38%). The frequency of positive cultures in primary (29/75, 39%) and secondary procedures (3/9, 33%) were similar. One positive culture site occurred in 26/32 (81%) patients, two positive culture sites existed in 5/32 (16%) patients, and three positive sites were found in 1/22 (3%) patients. Eighteen individual artery (18/152, 12%) and 19 adipose tissue samples (19/139, 14%) harbored bacteria, whereas only two blood cultures were positive (2/129, 2%). Organisms identified included coagulase-negative staphylococci (71%), gamma-streptococci (7%), diphtheroids (7%), Micrococcus (5%), alpha-streptococci (5%), Staphylococcus aureus (2%), and Pseudomonas picketti (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1989

Pelvic exenteration, University of Michigan: 100 patients at 5 years.

One hundred patients undergoing pelvic exenteration (total 69, anterior 13, posterior 18) at the University of Michigan Medical Center from 1964-1984 are reported. All patients were followed for at least 5 years or until time of death. The overall cumulative survival was 66% at 3 years and 61% at 5 years. The age of the patients ranged from 21-74 years (median 53). The type of pelvic neoplasm included squamous cell of the cervix, 57; adenocarcinoma of the cervix, nine; squamous cell carcinoma of the vulva, 12; squamous cell carcinoma of the vagina, eight; vaginal sarcoma, four; adenocarcinoma of the vagina, one; adenocarcinoma of the endometrium, four; uterine sarcoma, four; and adenocarcinoma of the ovary, one. The cumulative 5-year survival was significantly related to the presence of metastatic disease to the regional lymph nodes (8% 3-year and 0% 5-year survival), time interval from primary diagnosis to exenteration (within 1 year 44%, 1-10 years 60%, and over 10 years 95%), and cell type (squamous cell 68%, sarcoma 62%, and adenocarcinoma 26%). Patients with squamous cell carcinoma of the cervix (N = 57) had a cumulative 5-year survival of 73%, compared with nine patients with adenocarcinoma of the cervix, who had a 22% 5-year survival. No significant difference in survival existed for the type of exenteration, original stage of squamous cell cervical carcinoma, size of recurrent squamous cell lesion, or age of the patient. Early or late complications occurred in 49 patients. Two patients died in the postoperative period. Small-bowel obstruction was the most common complication seen in this series.

Adenocarcinoma↗
PubMed1989

A prospective study of clinically and endoscopically documented colonic ischemia in 100 patients undergoing aortic reconstructive surgery with aggressive colonic and direct pelvic revascularization, compared with historic controls.

Clinically and endoscopically proved ischemia of the colon complicates elective aortic reconstruction in 1% to 2% and 6% to 7% of cases, respectively. Operative mortality exceeds 60% when transmural infarction occurs. A prospective study of colonic ischemia was undertaken in 100 male patients (mean age, 62.4 +/- 7.9 years) undergoing operation for aortic aneurysms (58) or aortoiliac occlusive disease (42). Conventional aortic surgery was undertaken in 88 patients, and in 12 patients adjunctive procedures to enhance colonic perfusion were performed 14 times, including IMA reimplantation (8), direct bypass to the internal iliac artery (4), and anastomosis of an aortofemoral bypass limb to adjacent common iliac artery (2). Colonoscopy was performed within 24 to 48 hours of aortic reconstruction. Three patients had endoscopic evidence of colonic ischemia. Transmural infarction did not develop in any patient, and bowel resections or diverting colostomies were not necessary. Three patients died, none manifesting colonic ischemia. The 12% utilization of adjunctive procedures to enhance blood flow in the colon was substantially greater than the 4% frequency of an earlier experience from our institution in which nearly half of the 5.7% operative mortality was attributed to colonic infarction. Attention to factors contributing to ischemia of the colon, and more frequent adjunctive revascularization of the colon, may lessen this complication of aortic reconstructive surgery.

Angiography↗
PubMed1986

Adrenergic and dopaminergic control of the canine paw microcirculation.

Basal isolated canine paw blood flow was equally distributed between arteriovenous anastomosis (AVA) and capillary circulations. Norepinephrine decreased AVA flow by 92% and capillary flow by 41%. Dopamine significantly reduced AVA flow by 94% compared to baseline with a 37% reduction in capillary flow. However, with alpha-adrenergic blockade dopamine decreased AVA flow 66% while capillary flow increased 42%. Isoproterenol increased capillary flow almost twofold and appeared to decrease AVA flow, although the latter was statistically insignificant. Differential effects of adrenergic and dopaminergic agonists on canine paw AVA and capillary blood flow suggest the existence of independent regulation of these components of the microcirculation.

Animals↗
PubMed1986

Effects of continuous intravenous infusions of nitroglycerin on canine systemic and hind limb microcirculatory hemodynamics.

Systemic and hind limb hemodynamics were assessed in anesthetized dogs during continuous 30-minute intravenous infusions of nitroglycerin at 1, 5, 10, and 25 micrograms/kg/min. Nitroglycerin at 1 microgram/kg/min redistributed hind limb blood flow; hind limb arteriovenous shunting increased from 5.6% +/- 4.0% to 17.8% +/- 7.4% after 30 minutes (p less than 0.01); absolute hind limb shunt flow increased from 12 +/- 10 ml/min to 31 +/- 26 ml/min at 10 minutes (p less than 0.01); whereas hind limb nutrient blood flow decreased from 184 +/- 81 ml/min to 150 +/- 55 ml/min and 132 +/- 32 ml/min, respectively, at 10 and 30 minutes (p less than 0.05). Such hind limb blood flow redistribution was absent during infusion of all other nitroglycerin dosages. Total catecholamines increased at 30 minutes during both 1 and 10 micrograms/kg/min nitroglycerin infusions (p less than 0.05) with perhaps a slightly greater catecholamine response to 10 micrograms/kg/min after 30 minutes (0.05 less than p less than 0.10). The renin-angiotensin response at 3 minutes differed between nitroglycerin infusions of 1 and 10 micrograms/kg/min with an initial significant reduction from baseline in plasma renin activity at the lower dose compared with a significant increase from baseline in plasma activity at the higher dose. Nitroglycerin did not increase femoral artery flow or cardiac output and did not lower total peripheral vascular resistance at any dose studied. Despite this, arterial pressure and cardiac work were reduced at all nitroglycerin doses tested. Massive volume loading prevented the anticipated blood pressure reduction and blunted the expected cardiac work reduction during nitroglycerin infusions of 10 micrograms/kg/min. This study demonstrates that nitroglycerin is not a potent peripheral arteriolar vasodilator, 1 microgram/kg/min nitroglycerin infusions increase hind limb arteriovenous shunting and decrease hind limb nutrient blood flow, and myocardial work and arterial pressure reductions during nitroglycerin infusions appear to be caused by mechanisms other than generalized peripheral arterial dilation.

Animals↗
PubMed1986

Prostacyclin treatment of ischemic ulcers and rest pain in unreconstructible peripheral arterial occlusive disease.

The efficacy of prostacyclin (PGI2) treatment was assessed in 26 patients with surgically unreconstructible atherosclerotic arterial occlusive disease of the lower extremity manifested by nonhealing ulcers and rest pain. Patients were randomized to receive a 72-hour intravenous infusion of PGI2 (6 ng/kg/min, n = 13) or placebo (n = 13). Ulcer size was measured by photographic planimetry, and rest pain was graded by blinded objective scoring at monthly intervals for 6 months. Ulcer size increased 64% in PGI2-treated patients and 22% in placebo-treated patients by 1 month after infusion. Rest pain decreased slightly in both PGI2 and placebo groups. At the conclusion of the study, 54% of placebo-treated patients and 31% of PGI2-treated patients had a positive treatment response, indicated by at least a 20% decrease in ulcer size and a 33% decrease in rest pain. PGI2 infusion did not improve the high-placebo response rate seen in these patients with severely ischemic extremities. These results emphasize the importance of placebo-controlled studies, even in patients with unreconstructible arterial disease.

Aged↗
PubMed1985

Brachiocephalic arterial occlusions and stenoses. Manifestations and management of complex lesions.

Complex stenotic and occlusive lesions involving multiple brachiocephalic arteries were encountered in 17 symptomatic patients, 25 to 76 years of age. Symptoms included hemispheric transient ischemic attacks (16), visual symptoms (ten), global cerebral ischemia (11), true syncope (six), upper extremity ischemic symptoms (eight), and frank tissue loss (one). Of 68 brachiocephalic arteries, 53 exhibited hemodynamically significant stenoses, including 21 that were totally occluded. Transthoracic surgical reconstruction consisted of bypass grafting (11), innominate artery endarterectomy (five), or proximal left common carotid endarterectomy with reimplantation into the contralateral carotid artery (one). There were no operative deaths and only one transient perioperative neurologic deficit. All patients had relief of symptoms. When multiple brachiocephalic arterial occlusions and stenoses preclude standard cervical reconstructive procedures, direct transthoracic reconstruction is appropriate and may be undertaken with acceptable risk in properly selected patients.

Adult↗
PubMed1985

Nonpenetrating subclavian artery injuries.

Nonpenetrating subclavian artery trauma, a potentially catastrophic injury, has been recognized more frequently with the liberal use of angiography in evaluating blunt cervicothoracic trauma. Six patients, five men and one woman, recently underwent surgical treatment at the University of Michigan Hospital for blunt injury of the subclavian artery. The diagnoses were established by arteriography. Physical findings, chest roentgenograms, and results of noninvasive vascular evaluation were found to be nonspecific or unreliable. Operative treatment with resection of the injured arterial segments and either primary anastomosis or bypass grafting resulted in restoration of distal, upper extremity blood flow in all of the cases. One patient died 20 days after trauma from a severe associated cerebral injury. Among the five survivors, residual soft tissue and neurologic injury compromised full recovery in three. Thus, only two of the six patients survived without sequelae, a fact that underscores the seriousness of this type of subclavian artery injury.

Accidents, Traffic↗
PubMed1985

Celiac artery aneurysms: historic (1745-1949) versus contemporary (1950-1984) differences in etiology and clinical importance.

Celiac artery aneurysms were encountered in nine patients, ranging in age from 39 to 76 years, at the University of Michigan Medical Center between 1961 and 1983. Developmental defects and atherosclerosis were etiologic factors in six cases. Four patients were without symptoms, whereas five experienced abdominal pain, including one with a ruptured aneurysm. Eight patients were subjected to surgical treatment; no deaths occurred and symptoms were resolved in all patients. A literature review of 108 celiac artery aneurysms revealed two distinct subgroups. Among 60 celiac artery aneurysms encountered before 1950, representing the historic era, 40% were infectious (usually luetic), 7% were traumatic, and 52% were of undetermined cause. Most were symptomatic, 87% ruptured, and 95% were diagnosed at postmortem examination. The contemporary era since 1950 consisted of 48 cases, including nine in the Michigan experience. Congenital or developmental medial defects of the arterial wall and atherosclerosis were the most common causes of aneurysms. Most aneurysms in the contemporary period were either asymptomatic or accompanied by vague abdominal discomfort. Rupture affected 13% of those aneurysms. Operative therapy was successfully undertaken in 91% of 43 patients during the contemporary era, including eight in the present series.

Adult↗
PubMed1985

Actuarial analysis of variables associated with rupture of small abdominal aortic aneurysms.

This study identified risk factors associated with rupture of small abdominal aortic aneurysms in patients initially selected for nonoperative management. Sixty-seven patients, 53 men and 14 women, 50 to 91 years of age (mean 72 years) were followed 3 to 99 months (mean 36 months). All patients underwent serial aortic ultrasonography. The annual rate of aneurysm rupture was 6%, with an annual mortality rate caused by rupture of 5% and an annual mortality rate caused by coexistent disease of 6%. Thirty potential risk factors, including blood pressure, aneurysm size measured by ultrasonography, rate of aneurysm expansion, smoking, serum cholesterol levels, and cardiac, pulmonary, and renal risks, were analyzed by Cox proportional hazards regression to identify variables related to rupture. Aneurysm anteroposterior expansion rates varied from 0 to 1.5 cm/year but were not different in aneurysms that ruptured. Only diastolic blood pressure, initial aneurysm anteroposterior diameter, and degree of obstructive pulmonary disease were independently predictive of rupture (p less than 0.05, Wald test). With these data, actuarial rupture rates were predicted for patients with selected values of these three covariates. Predicted 5-year rupture rates varied from 2% when these risk factors were absent to 100% when all three risk factors were significant. Obstructive pulmonary disease, initial aneurysm size, and diastolic hypertension must be evaluated prospectively to assess their accuracy in predicting small aneurysm rupture.

Actuarial Analysis↗
PubMed1985

Reoperation for complications of renal artery reconstructive surgery undertaken for treatment of renovascular hypertension.

Seventy-two secondary operations for complications of prior renal artery reconstructive surgery were undertaken in 58 patients. This experience evolved from the management of 373 patients who underwent 425 primary operations for renovascular hypertension. Secondary operations were performed 10 times in pediatric patients following 42 primary procedures (24%); 44 times in adult fibrodysplastic patients following 199 initial operations (22%); and 18 times in atherosclerotic patients after 184 primary operations (10%). The overall reoperation rate was 15.5% (58 of 373 patients). Reoperation typically followed persistent or recurrent hypertension caused by graft thromboses, perianastomotic graft narrowing, or progressive nonanastomotic graft stenoses. Aneurysmal deterioration of vein grafts was an uncommon reason for reoperation. Secondary reconstructions included nephrectomy (31), bypass with vein grafts (15) or prosthetic grafts (8), angioplasty or reimplantation (12), thrombectomy (4), and operative dilation (2). Benefits regarding hypertension control were afforded 91% of these patients. One death occurred among the 72 reoperations, representing a 1.4% operative mortality rate. Reoperative renal artery reconstructive surgery for complications of renal revascularization may present formidable technical problems. Early diagnosis and prompt reoperation with exacting vascular surgical techniques are most likely to provide optimal results.

Adolescent↗
PubMed1984

Early derangements of arteriovenous anastomotic and capillary blood flow in the canine hindlimb induced by supplemental pentobarbital anesthesia.

Vasoactive effects of supplemental pentobarbital anesthesia in the canine hindlimb microcirculation were documented in two groups of animals previously anesthetized with 30 mg/kg pentobarbital: Group I with a 5 mg/kg intravenous (iv) bolus of pentobarbital (n = 8) and Group II with a 5 mg/kg 2-min iv infusion of pentobarbital (n = 7). In Group I, measurements at baseline (BL) and 5, 15, 20, and 30 min (min) following pentobarbital administration included cardiac output, mean arterial pressure, total peripheral vascular resistance, common femoral artery flow (CFAQ) and resistance (CFAR), percentage hindlimb arteriovenous anastomotic shunt (AVA%), absolute shunt flow (AVAQ), and hindlimb nutrient capillary flow (NCQ). In Group II these same measurements were made, but the study was continued until all hindlimb hemodynamic parameters returned to control values. CFAQ, AVA%, AVAQ, and NCQ were significantly increased, and CFAR was decreased in both groups. CFAQ and NCQ remained significantly elevated at 30 min in Group I. In Group II CFAR, AVA%, and AVAQ remained elevated at 30 min, but did return to BL by 40 min, as did all other hindlimb hemodynamic parameters measured. Pentobarbital resulted in both AVA and arteriolar dilation, with an increase in the percentage total flow distributed to AVAs. These alterations of microcirculatory flow should be considered during investigations of the distribution of peripheral blood flow, as well as during metabolic studies assessing arteriovenous substrate differences, if interpretative errors are to be avoided.

Anesthesia↗