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Biomedical subjects

S M Lindenauer

Publications and source records attributed to S M Lindenauer.

At least 37 records · Page 2Linked to original sources
PubMed1984

Interaction of hindlimb blood flow, A-V shunting and A-V oxygen difference.

The interactions of blood flow, A-V O2 difference (AVDO2), and A-V shunting were measured in normal hindlimbs of nine anesthetized dogs. An aorto-iliac nonpulsatile perfusion pump was used to change femoral artery blood flow from zero (collateral flow only) to twice its baseline level. Femoral AVDO2 was measured by in-line spectrophotometric O2 analysis. A-V shunting was measured with radio-labeled microspheres. Systemic hemodynamic parameters and temperature remained constant during the experiments. Despite changes in femoral mean arterial pressure (160 to 54 mm Hg) and AVDO2 (1.8 to 8.2 ml O/2/dl) that occurred with femoral blood flow reduction, peripheral A-V shunting remained constant at 4.1-5.5%. Alpha-adrenergic ablation (sympathectomy) was used to increase A-V shunting (up to 20%) during part of this experiment. When hindlimb blood flow was normal or increased, autoregulation of O2 extraction maintained constant hindlimb O2 consumption, despite sympathectomy-induced changes in A-V shunting. Subnormal femoral artery blood flow reduced hindlimb O2 consumption, and in this setting the increased A-V shunting further decreased femoral AVDO2 and O2 consumption. Since AVDO2 is dependent upon both blood flow and the variable efficiency of cellular O2 extraction, it cannot be used as an accurate indicator of A-V shunting. Direct microsphere techniques should be applied to A-V shunt measurements in clinical settings where A-V shunting is suspected.

Animals↗
PubMed1984

Effects of glucagon and prostacyclin in acute occlusive and postocclusive canine mesenteric ischemia.

Effects of glucagon and prostacyclin (PGI2) were studied in anesthetized dogs during sequential occlusive and postocclusive mesenteric ischemia induced by 90 min of tourniquet stenosis of the superior mesenteric artery (SMA). After 30 min of SMA stenosis, glucagon (1 microgram/kg/min, n = 7), PGI2 (30 ng/kg/min, n = 7), or saline (1 ml/min, n = 3) was infused intravenously for 30 min, followed by 30 min of continued ischemia. SMA flow and distal SMA pressure ( SMAP ) decreased 76% with SMA stenosis (P less than 0.01). Ileal wall flow measured by radiolabeled microspheres decreased from 45 to 13 ml/min/100 g (P less than 0.01); mesenteric AV O2 difference ( AVDO2 ) increased from 5.1 to 10.1 ml/dl (P less than 0.01); and mesenteric O2 consumption (VO2) decreased by 48% (P less than 0.05). Glucagon infusion caused a further decrease in ileal wall flow, to 10 ml/min/100 g (P less than 0.05), and an increase in AVDO2 to 11 ml/dl (P less than 0.05), despite a 22% increase in cardiac output. PGI2 caused a similar decrease in ileal wall flow and an increase in AVDO2 , although these were not statistically significant. Saline infusion caused no change in measured variables. In the second phase of this study, SMA blood flow was restored by tourniquet release. After animals had stabilized for 30 min, a repeat 30-min drug infusion was studied. In this postocclusive period, persistent gut ischemia was indicated by a reduction in VO2 to 76% of original baseline, associated with a 50% decrease in both CO and SMAQ . Intravenous infusion of glucagon at this time increased SMAQ by 195% (P less than 0.05) and resulted in a return of VO2 to its original baseline level. PGI2 infusion caused a 21% increase in SMAQ and a 16% decrease in AVDO2 (NS), but had no significant effect on VO2. Glucagon was effective in the management of postocclusive mesenteric ischemia but appeared to have a detrimental effect on ileal blood flow in severe occlusive ischemia.

Acute Disease↗
PubMed1984

Pharmacologic interventions in acute mesenteric ischemia: improved survival with intravenous glucagon, methylprednisolone, and prostacyclin.

An experimental model of acute mesenteric ischemia following 85 minutes of superior mesenteric artery (SMA) occlusion in male Wistar rats was used in this investigation. Untreated control animals had a 48-hour survival rate of 38% (n = 26), whereas sham laparotomy resulted in a 100% 48-hour survival rate (n = 10). Study groups received intravenous infusions of normal saline solution (16.6 ml/kg/hr; n = 26) or similar volumes of normal saline solution with the addition of glucagon (1.6 micrograms/kg/min; n = 26), dopamine (3.2 micrograms/kg/min; n = 26), or prostacyclin (PGI2) (10.7 ng/kg/min; n = 26). Infusions were begun 15 minutes after initiating 85 minutes of SMA occlusion and were continued for a total of 90 minutes. Glucagon increased the 48-hour survival rate to 85%, significantly greater than both control survival (p less than 0.001) and normal saline solution group survival rates (p less than 0.025). Neither normal saline solution alone nor dopamine significantly increased the 48-hour survival rate, which was 54% in both groups. The PGI2 group survival rate, 65% at 48 hours, was significantly greater than the control rate (p less than 0.05), was not statistically different from the normal saline solution group survival rate, and was 20% less than the glucagon group survival rate, the latter difference approaching statistical significance (p = 0.10). Methylprednisolone (40 mg/kg; n = 26) administered as an intravenous bolus 15 minutes after initiating SMA occlusion significantly increased the 48-hour survival rate to 73% (p less than 0.01), whereas neither intravenous heparin (150 U/kg; n = 26) nor superoxide dismutase (11,900 U/kg; n = 26) were beneficial. Glucagon, methylprednisolone, and PGI2 improved the survival rate in this model of acute mesenteric ischemia.

Animals↗
PubMed1984

Atherosclerotic extracranial carotid artery aneurysms.

Twenty-four atherosclerotic extracranial carotid artery aneurysms were encountered in 21 patients during a 25-year period. These represented 46% of all extracranial carotid artery aneurysms diagnosed at the University of Michigan during this period. Neurologic symptoms including amaurosis fugax, transient ischemic attacks, and stroke were present in 50% of the patients. An asymptomatic pulsatile neck mass occurred in 33%. Surgical therapy was undertaken for 18 aneurysms, and nonoperative treatment was pursued in the remaining six aneurysms. Operative therapy included 14 aneurysmectomies and four aneurysmorraphies. There were no surgical deaths. Transient perioperative neurologic deficits affected three of these patients (17%), and one individual (5%) experienced a permanent deficit. Transient cranial nerve deficits occurred in three patients (17%), and a permanent deficit was noted in one patient (5%). During a 7.6-year follow-up period no late strokes occurred among patients who were operated on. Nonoperative therapy was associated with three ipsilateral strokes during a mean follow-up period of 6.3 years. Atherosclerotic extracranial carotid artery aneurysms were associated with an exceptionally high stroke rate (50%) if treated nonoperatively. Prevention of late stroke justifies surgery, although perioperative neurologic deficits may accompany this therapy more often than with nonatherosclerotic carotid artery aneurysms.

Aged↗
PubMed1983

The effect of sympathetic innervation on canine muscle and skin blood flow.

Two microsphere techniques were used to measure skin and muscle capillary blood flow, plus blood flow through arteriovenous anastomoses (AVAs), before and after unilateral lumbar sympathectomy in 12 anesthetized dogs. Sympathectomy did not alter capillary flow to tibial muscle, thigh, or lower leg skin, whereas paw skin capillary flow decreased, from 28 to 13 mL/min/100 g. However, total extremity blood flow increased after sympathectomy, because of the rate of AVA flow, which increased from 7 to 30 mL/min. Transient nerve stimulation of the cut distal end of the lumbar sympathetic chain immediately and reversibly decreased the AVA flow rate, from 30 to 10 mL/min. The rate of total hind-limb capillary flow also decreased during nerve stimulation, from 86 to 46 mL/min. The only significant effect of sympathectomy in anesthetized dogs was to redistribute distal hind-limb capillary blood flow to AVAs, which are anatomically located in this region. In contrast to capillaries, AVAs have little intrinsic myogenic tone and are highly dependent on adrenergic innervation.

Animals↗
PubMed1983

Limb-threatening potential of arteriosclerotic popliteal artery aneurysms.

Eighty-eight popliteal artery aneurysms were diagnosed in 59 men and two women (mean age 67 +/- 10 years). Bilateral aneurysms affected 27 patients (44%). Aneurysm diameter ranged from 1.3 to 12 cm (mean 4 +/- 2.6 cm). Most aneurysms were symptomatic (55%). Dominant symptoms included rest pain (19%), claudication (14%), local pain (13%), and gangrene (9%). The remainder of the aneurysms were asymptomatic (45%). Aneurysm thrombosis occurred in 24% of extremities. Associated aneurysms involved the abdominal aorta (62%), iliac artery (36%), and femoral artery (38%). Aneurysms that caused local pain were larger (6.2 +/- 1.9 cm) than asymptomatic aneurysms (2.9 +/- 2.1 cm, P less than 0.01). Aneurysms smaller than 2 cm were more likely to be asymptomatic than larger aneurysms (P less than 0.05). Operative intervention was undertaken for 56 aneurysms, with aneurysmal exclusion or excision with arterial reconstruction performed most often. Four primary and five secondary major amputations were associated with thrombosed aneurysms, compared to no amputations with asymptomatic aneurysms (P less than 0.01). Thirty-two aneurysms were not treated surgically. Limb loss resulted from ischemic complications which developed in 18% of aneurysms treated without operation. The duration of follow-up for patients who had operation and those who did not averaged 62 months and 25 months, respectively. Operative treatment for all bland popliteal artery aneurysms appears justified if complications leading to major amputation are to be avoided.

Adult↗
PubMed1982

Extracranial internal carotid artery dissections: noniatrogenic traumatic lesions.

Noniatrogenic traumatic extracranial internal carotid artery dissections were encountered in six patients (five men and one woman) 31 to 62 years old. All but one had overt cerebral ischemia manifest by paresis (three), sensory deficits (three), aphasia (three), or amaurosis fugax (two), One patient had an asymptomatic carotid artery bruit. Cerebral arteriography established the diagnosis in all cases. Internal carotid artery impingement between the mandible and transverse processes of the second and third cervical vertebrae, or undue stretching over these vertebral structures, were the most likely primary mechanisms of injury. Secondary complications, a result of distal thromboembolism, were evident in two patients. Direct cerebral revascularization, staged internal carotid artery constriction and ligation, as well as intensive nonoperative therapy were valid therapeutic options. There were no deaths. Treatment relieved transient ischemic symptoms or arrested progression of established neurologic deficits in each case. In select patients, early surgical intervention may lessen attending neurologic sequelae.

Adult↗
PubMed1982

Adenocarcinoma of the ampulla of Vater. Diagnosis and treatment.

Fifty-one patients underwent operation for adenocarcinoma of the ampulla of Vater. Seven patients underwent palliative bypass, with an operative mortality of 28.6%; 44 additional patients underwent potentially curative pancreaticoduodenal resection (PDR), with an operative mortality of 15.9%. Postoperative complications occurred in 63% of patients. Postoperative gastrointestinal bleeding was observed in 11 of 44 patients who underwent PDR (25%). Although anastomotic ulcers (AU) were directly implicated in five cases (45%), the 12% incidence of AU-related bleeding among 33 patients who underwent PDR without truncal vagotomy (TV) was not significantly different from the 9% incidence observed in 11 patients who underwent PDR plus TV. However, performance of TV appeared to result in a higher incidence of postoperative pulmonary complications. Five patients who underwent curative resection survived for five years (11%). Only one of seven patients who underwent palliative bypass survived three years (14%), and none survived to five years. Acceptable survival rates following resectional therapy warrant an aggressive approach to this tumor. Further, our experience suggests that TV may increase postoperative patient morbidity without actually providing any protection from anastomotic ulceration.

Adenocarcinoma↗
PubMed1982

Abdominal aortic aneurysm rupture: statistical analysis of factors affecting outcome of surgical treatment.

One hundred sixteen patients underwent surgery for ruptured abdominal aortic aneurysms with intraoperative and overall mortality rates of 20.7% and 51.7%, respectively. The correlation of multiple factors to morbidity and mortality was assessed with detailed statistical analysis. Eight preoperative factors were identified as predictors of mortality. Increased intraoperative mortality rates were associated with heart disease (29%), hypertension (30%), flank ecchymoses (57%), and pulsatile abdominal mass (24%). Increased intraoperative and overall mortality rates were associated with preoperative hypotension (39%, 78%) and BUN levels higher than 30 mg/dl (47%, 82%). Increased overall mortality rates were associated with creatinine levels higher than 3 mg/dl (71%) and a hematocrit of 30.0 to 32.5 vol% (75%) (P less than 0.05). Seven intraoperative factors were identified as predictors of mortality. Increased postoperative mortality rates were associated with a duration of operation of more than 400 minutes (100%), hypotension lasting longer than 110 minutes (88%), estimated blood loss more than 11,000 ml (75%), blood transfusion more than 17 U (68%), fluid administration in excess of 7000 ml (70%), and a blood pressure lower than 100 mm Hg at the conclusion of the operation (88%). Cardiac arrest was associated with increased intraoperative and overall mortality rates (77%, 82%) (P less than 0.05). In general these factors cannot be controlled by the surgeon, and future significant reduction in the operative mortality rate may be possible. These findings support the general concept of aggressive elective resection of abdominal aortic aneurysms.

Aged↗
PubMed1981

Developmental occlusive disease of the abdominal aorta and the splanchnic and renal arteries.

Developmental occlusive disease of the abdominal aorta and the renal and splanchnic arteries represent an unusual vascular condition. When unrecognized or untreated this disease is associated with premature death, usually from severe secondary hypertension as a consequence of renovascular stenotic lesions. Strong circumstantial evidence indicates that developmental abnormalities occurring during the fetal union of the two dorsal aortae account for most of the occlusive lesions affecting the abdominal aorta and its visceral branches in these patients. Complete arteriographic studies are necessary to confirm and accurately delineate the disease process. Surgical treatment, which often encompasses complex vascular reconstructive efforts, affords excellent results when carefully planned and executed.

Adolescent↗
PubMed1981

Dacron velour arteriovenous fistula for hemodialysis access.

Dacron velour arteriovenous fistulas were created in the necks of 12 dogs. Sham dialysis was performed three times per week for one month in six animals, and for six months in an additional six animals. One prosthesis became infected, and perigraft bleeding occurred twice. There were no false aneurysms, and all prostheses remained patent. Dacron velour appears to be a satisfactory prosthetic material for use as an arteriovenous fistula for chronic hemodialysis access. The enhanced fibrous tissue adherence of Dacron velour may account for the few complications encountered.

Animals↗
PubMed1981

Chronic total renal artery occlusion: effects of treatment on secondary hypertension and renal function.

Chronic total occlusion of 42 main renal arteries was documented by arteriographic studies in 25 female and 15 male patients being evaluated for drug-resistant hypertension. Arteriosclerotic lesions affected 35 patients, and fibrodysplastic obstructions occurred in five. Hypertensive urographic studies showed lateralization to the affected kidney in all 31 studies obtained. Renal vein renin activity lateralized with a mean ratio of 3.88 in the 24 patients studied. In 15 patients, mean renal: systemic renin indices (RSRI) of 2.39 confirmed ischemic kidney renin hypersecretion, and a mean RSRI of 0.03 confirmed contralateral suppressed secretion. Affected kidney lengths averaging 9.4 cm were significantly smaller than the 13.0 cm length of kidneys without occluded arteries. Thirty patients with 31 occluded arteries underwent renal artery bypass (18), endarterectomy (2), or nephrectomy (11). There were two perioperative deaths. Eighty-nine percent of survivors benefited in regard to hypertension control, and 47% exhibited improved renal function. Nonoperative treatment of 10 patients was associated with frequent progression of renal failure and inadequate blood pressure control. This experience documents the appropriateness of surgical therapy for secondary hypertension caused by chronically occluded renal arteries.

Aged↗
PubMed1981

Discriminant arteriographic criteria in the management of forearm and hand ischemia.

Fifty-five patients (33 male and 22 female), 3 to 73 years in age, underwent aortic arch and selective upper extremity arteriography for the evaluation of forearm and hand ischemia from 1971 to 1980. Fifty-one patients had organic occlusive lesions (12 subclavian, 15 axillobrachial, 17 radial-ulnar, and 7 palmar-digital), including distal forearm and hand emboli, as a consequence of proximal occlusive disease in nine patients (5 subclavian, 2 axillobrachial, and 2 radial-ulnar). The remaining four patients had vasospastic disease. Major arteriographic findings of obstructive disease were defined by: morphology of lesions, symmetry or asymmetry of obstructions, segmental versus tandem lesion distribution, and the resultant pattern of collateral circulation. Vasodilatory pharmacoangiography with magnification technique frequently facilitated evaluation of digital and collateral vessels. Therapeutic interventions were dictated by clinical data heavily weighed by the arteriographic examination. Limited arteriographic studies would have been misleading in the evaluation of many patients.

Adolescent↗