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Biomedical subjects

B T Allen

Publications and source records attributed to B T Allen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Role of Doppler US in screening for carotid atherosclerotic disease.

PURPOSE: To evaluate Doppler ultrasound (US) as a screening modality before arteriography for extracranial carotid artery disease. MATERIALS AND METHODS: The net benefit in stroke reduction from screening with Doppler US was calculated on the basis of literature estimates of disease prevalence, risk reduction data, and locally validated sensitivities and specificities for detection of carotid artery stenosis and occlusion in 215 patients. RESULTS: Screening a symptomatic population demonstrated a net stroke reduction. Screening asymptomatic populations with a 20% prevalence of > or = 60% stenosis also yielded a net stroke reduction. Screening low-prevalence (5%) asymptomatic populations produced a small benefit, which was lost if arteriographic or surgical complications increased slightly. Arteriographic confirmation of the US diagnosis of occlusion produced a small benefit only in the symptomatic population. CONCLUSION: Screening symptomatic and high-prevalence asymptomatic populations with US reduces stroke. Increased arteriographic or surgical complication rates reduce the benefit of screening in any population.

Arteriosclerosis↗
PubMed1994

Relationship between evoked potentials and clinical status in spinal cord ischemia.

STUDY DESIGN: Sciatic neurogenic motor-evoked potentials (sciatic-NMEP), spinal-evoked potentials (spinal-EP), and somatosensory-evoked potentials (SEP) were recorded in the lumbar cord during progressive ligation of segmental arteries. Relationship between electrophysiologic assessment and clinical status was studied. OBJECTIVES: In 12 anesthetized dogs that had arterial ischemia of the lumbar cord produced by ligation of segmental arteries, the aforementioned evoked potentials were recorded, and their presence or absence was compared with the clinical status of repeated wake-up tests. SUMMARY OF BACKGROUND DATA: Both sciatic-NMEP loss and ligation level producing cord ischemia were not associated with severity of wake-up test. Sciatic-NMEPs were lost earlier than spinal-EP and SEPs after progressive ligation. The false-negative rate of sciatic-NMEP, SEP at high spine and at low spine was 12.5%, 20.8%, and 41.7%, respectively. The waveform morphology of potentials by cord ischemia decreased in amplitude and in the number of peaks without a shift of latency. METHODS: First, baseline NMEPs and SEPs were obtained, lumbar arteries were ligated, evoked potentials were recorded continuously, and wake-up test was administered. If sciatic-NMEPs were not lost, intercostal arteries were ligated, and potentials and clinical status were reassessed. RESULTS: Though these results were complicated, sciatic-NMEP was more sensitive to the spinal cord ischemia and a better predictor of clinical outcome than spinal-EP and SEP. However, the presence was not a guarantee of normal function. Somatosensory-evoked potentials are not a good predictor of clinical motor status. The initial morphologic change of these potentials secondary to ischemia consisted of a decrease in amplitude and in the number of peaks without a shift of latency. CONCLUSIONS: The peripheral-NMEP is a better warning system to spinal cord ischemia and its adoption may prevent cord ischemia during surgery, whereas SEP and spinal-EP can not be indicies.

Animals↗
PubMed1994

Diagnosis of perioperative myocardial infarction with measurement of cardiac troponin I.

BACKGROUND: Perioperative myocardial infarction is the most common cause of morbidity and mortality in patients who have had noncardiac surgery, but its diagnosis can be difficult. The present study was designed to determine whether the measurement of serum levels of cardiac troponin I, a highly sensitive and specific marker for cardiac injury, would help establish the diagnosis of myocardial infarction. METHODS: We obtained preoperative measurements of MB creatine kinase, total creatine kinase, and cardiac troponin I, in addition to base-line electrocardiograms and two-dimensional echocardiograms, in 96 patients undergoing vascular surgery and 12 undergoing spinal surgery. Blood samples were obtained every 6 hours for at least the first 36 hours after surgery, and electrocardiograms were obtained daily; a second echocardiogram was obtained approximately three days after surgery. The appearance of a new abnormality in segmental-wall motion on the postoperative echocardiogram (that is, an abnormality that had not been seen on the preoperative echocardiogram) was considered to be indicative of perioperative infarction. RESULTS: Eight patients who underwent vascular surgery had new abnormalities in segmental-wall motion and received a diagnosis of perioperative infarction. All eight had elevations of cardiac troponin I, and six had elevations of MB creatine kinase. Of the 100 patients without perioperative infarction detected by echocardiography, 19 had elevations of MB creatine kinase, and 1 had a slight elevation of cardiac troponin I. CONCLUSIONS: The measurement of cardiac troponin I is a sensitive and specific method for the diagnosis of perioperative myocardial infarction. It avoids the high incidence of false diagnoses associated with the use of MB creatine kinase as a diagnostic marker.

Creatine Kinase↗
PubMed1994

An institutional experience with arterial atheroembolism.

Seemingly minor blue-toe lesions resulting from atheroemboli are associated with unstable atherosclerotic plaques, which are at risk for causing recurrent emboli, tissue loss, and potentially death. At Washington University Medical Center, 62 patients (31 males and 31 females), ranging in age from 38 to 89 years (mean 62.8 +/- 11.7 years), were treated for cutaneous manifestations of atheroembolic disease. Most patients (62%) had spontaneous bouts of atheroembolism, but 13 (21%) had recently undergone an inciting invasive radiologic study, 10 (16%) were on anticoagulation therapy, and one (2%) experienced abdominal trauma. In addition to the cutaneous manifestations, 18 patients (29%) also developed coincidental deterioration in renal function and four (6%) had intestinal infarction from atheroemboli. Arteriography in nearly all patients (97%) implicated the aorta and iliac arteries most commonly (80%), with the femoral (13%), popliteal (3%), and subclavian (3%) arteries less frequently incriminated. Forty-two patients underwent bypass grafting procedures (36 anatomic and six extra-anatomic) after exclusion of the native diseased artery, 20 patients had endarterectomies (six with additional bypass grafts), and five patients had no corrective vascular procedures. The 30-day operative mortality rate was 5% in this series. Nineteen patients (31%) required minor amputations, whereas two required major leg amputations. Thus limb salvage was possible in 86 of 88 (98%) limbs. No further episodes of atheroembolism occurred in the involved limbs during follow-up (1 to 53 months, mean 20.2 months). We advocate urgent arteriography and surgical correction or bypass with exclusion of the offending lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The influence of anesthetic technique on perioperative complications after carotid endarterectomy.

PURPOSE: This study evaluated the influence of anesthetic techniques on perioperative complications after carotid endarterectomy. METHODS: Perioperative complications, the use of a carotid artery shunt, the duration of the operative procedure and postoperative hospital course were retrospectively compared in 584 consecutive patients undergoing 679 carotid endarterectomies with use of either general anesthesia (n = 361) or cervical block regional anesthesia (n = 318). There was no significant difference in the preoperative medical characteristics between the two anesthetic groups. Symptomatic carotid artery disease was the indication for surgery in 247 (68.4%) patients receiving general anesthetics, whereas 180 (56.6%) patients treated with a cervical block anesthetic had a symptomatic carotid artery stenosis (p = 0.02). RESULTS: The perioperative stroke rate and stroke-death rate for the entire series was 2.4% and 3.2%, respectively, and was not significantly different between the anesthetic groups or between patients with symptomatic or asymptomatic disease. A carotid artery shunt was used in 61 (19.2%) patients receiving a cervical block anesthetic and 152 (42.1%) patients treated with a general anesthetic (p < 0.0001). Use of cervical block anesthesia was associated with a significantly shorter operative time, fewer perioperative cardiopulmonary complications, and a shorter postoperative hospitalization when compared with general anesthesia. Multivariate risk factor analysis indicated that age greater than 75 years, operative time greater than 3 hours, and the use of a carotid artery shunt were all independent risk factors for perioperative cardiopulmonary complications. When a carotid artery shunt was not analyzed as a multivariate risk factor, then general anesthesia became a significant risk factor for perioperative cardiopulmonary complications (risk ratio 2.08; p = 0.04). CONCLUSIONS: We conclude that cervical block anesthesia is safer and results in a more efficient use of hospital resources than general anesthesia in the treatment of patients undergoing carotid endarterectomy.

Aged↗
PubMed1994

Spinal cord ischemia and reperfusion metabolism: the effect of hypothermia.

PURPOSE: The metabolic and neurologic functional effects of regional hypothermia induced by cold (4 degrees C) heparinized saline perfusion on spinal cord ischemia were evaluated in 35 rabbits. METHODS: Spinal cord ischemia was induced for 20 minutes by infrarenal aortic occlusion in anesthetized animals. Regional spinal cord hypothermia was obtained by perfusing the lumbar arteries supplying the spinal cord through an infrarenal aortic catheter. The lumbar spinal cord was "snap frozen" in situ with liquid nitrogen and harvested immediately at the conclusion of the ischemic period or after 24 hours of normothermic reperfusion and neurologic observation. Spinal cord metabolic studies included determination of the energy charge and the intracellular concentrations of adenosine triphosphate, glucose, lactate, glutamate, and aspartate. RESULTS: Postoperative neurologic function was normal in all but one animal treated with hypothermia, while normothermic ischemia resulted in paralysis in all animals (p = 0.002). Spinal cord temperature during 20 minutes of ischemia and hypothermic perfusion decreased from 37.5 degrees +/- 0.43 degrees C to 22.8 degrees +/- 0.00 degrees C (p = 0.0001) compared to a fall in systemic temperature from 38.8 to 36.1 (p = 0.0001). Hypothermia reduced the decline in energy charge, adenosine triphosphate concentration and glucose concentration during ischemia but had no effect on markedly elevated levels of lactate acid. High-energy phosphates were restored after reperfusion in both normothermic and hypothermic animals and were not predictive of postoperative paraplegia. Intracellular glutamate and aspartate concentrations were unchanged during normothermic ischemia but decreased after reperfusion in all paralyzed animals. Intracellular glutamate and aspartate concentrations increased during hypothermic perfusion and remained elevated after reperfusion in animals with a normal or mildly abnormal neurologic examination result. CONCLUSIONS: We conclude that spinal cord hypothermia induced by cold heparinized saline perfusion is a simple technique that prevents paraplegia after 20 minutes of ischemia and preserves intracellular concentrations of important metabolites.

Adenosine Triphosphate↗
PubMed1994

Determinants of outcome for patients in the medical intensive care unit requiring abdominal surgery: a prospective, single-center study.

OBJECTIVE: To identify objective factors, available at the time of surgical evaluation, associated with outcome for patients in the medical ICU undergoing abdominal surgery. DESIGN: Single-center, prospective observational study. SETTING: An academic tertiary care center. PATIENTS: The study included 1,617 consecutive patients in the medical ICU. INTERVENTION: Prospective patient surveillance and data collection. MEASUREMENTS: Patient demographics, severity of illness, organ system derangements, abdominal processes requiring surgery, and hospital mortality. RESULTS: Sixty-seven patients in the medical ICU (4.1 percent) developed an acute abdominal process potentially amenable to surgical intervention. Eleven of these patients (16.4 percent) elected not to undergo surgery (mortality = 100 percent). Forty-two of the 56 patients who underwent surgery survived (75.0 percent). Stepwise logistic regression analysis identified two independent objective predictors of mortality for this patient cohort (p < 0.05): an organ system failure index (OSFI) > 2 (adjusted odds ratio [AOR] = 19.5; 95 percent confidence interval [CI], 7.4 to 51.5; p < 0.001); and an APACHE II score > 18 (AOR = 9.4; CI = 3.1 to 28.3; p = 0.03). The observed mortality following surgery was stratified according to the presence or absence of these two factors: neither present, 5.1 percent; APACHE II > 18 present alone, 33 percent; OSFI > 2 present alone, 60 percent; and both present, 88.9 percent (p < 0.001). Surgical nonsurvivors and patients electing not to undergo surgery were similar without significant differences for demographics, severity of illness, or organ system derangements at the time of surgical evaluation. CONCLUSIONS: The number of organ system derangements and the severity of illness, as assessed by APACHE II, appear to be useful discriminators of outcome for patients in the medical ICU undergoing abdominal surgery. These data suggest potential outcome predictors for this selected group of patients in the ICU.

APACHE↗
PubMed1994

Long-term effectiveness of extraanatomic renal artery revascularization.

BACKGROUND: The efficacy of direct aortorenal bypass and renal artery endarterectomy are well established. The purpose of this study is to define better the results of extraanatomic renal revascularization procedures. METHODS: From April 1987 to March 1993, 124 patients underwent renal artery revascularization. Forty-eight (39%) of them (33 women, 15 men; average age, 65.9 years) underwent 49 extraanatomic renal artery bypasses. Preoperative risk factors included smoking in 30 patients (61%), history of myocardial infarction in 14 (29%), diabetes mellitus in 11 (22%), congestive heart failure in nine (18%), chronic obstructive pulmonary disease in 11 (22%), and stroke in six (12%). The average creatinine level was 2.3 mg/dl. The average number of antihypertensive medications was 2.4. Thirty iliorenal, 10 gastroduodenal-renal, seven hepatorenal, and two splenorenal bypasses were performed together with 10 contralateral nephrectomies. RESULTS: Six major postoperative complications occurred. There were no deaths. Forty-one (85%) of patients had improvement or cure of their hypertension. Seven (15%) of patients failed to respond to treatment, and three required subsequent nephrectomy. After operation the average creatinine level was 1.7 mg/dl and the average number of medications was 1.7. Mean follow-up period has been 23.2 months (range, 1 to 79 months). CONCLUSIONS: Extraanatomic bypass proved to be efficacious in treating hypertension and preserving renal function and has an acceptable rate of morbidity and mortality. We conclude that these procedures are an acceptable alternative to direct aortorenal artery revascularization.

Aged↗
PubMed1993

Preoperative duplex venous imaging in the assessment of patients with venous access.

Occult or clinically apparent central venous thrombosis frequently complicates central venous catheter placement in patients requiring long-term vascular access. Thirty-three patients, aged 12-83 years, underwent duplex scanning of the internal jugular, axillary, and brachial veins prior to placement of long-term venous access catheters. Twenty-seven patients underwent duplex scanning because of a prior history of either long-term or short-term central venous access. Of 12 patients with a history of long-term central venous access, without complications, 42% (5/12) had an abnormal duplex scan demonstrating thrombosis. Duplex scans on 15 patients having complications associated with central venous access demonstrated thrombosis of one or more of the central veins, 46% (7/15). Five patients who underwent duplex scanning without a history of a previous central venous catheter or other indication were found to have normal central veins. In 13 patients found to have thrombosis or obstruction by duplex scan, the surgeon was directed to successful venous access in all cases. Normal findings were very helpful in confirming that the venous system was normal in selected patients. In approximately 40% of patients with a history of venous access, catheters were found to have evidence of thrombosis of one or more of the central veins. In 13 patients found to have thrombosis or obstruction by duplex scan, the surgeon was directed to a successful site for venous access in all cases.

Adolescent↗
PubMed1993

Simultaneous surgical management of aortic and renovascular disease.

The results of simultaneous elective infrarenal aortic reconstruction and renovascular surgery were retrospectively reviewed in 102 patients who consecutively underwent operation. The perioperative mortality rate (0 to 54 days) was 5% (5 of 102). Renal function had returned to baseline or was improved at discharge in 89 of 97 (92%) surviving patients. The intraoperative use of renal hypothermia was an independent predictor of improved postoperative renal function, by multivariate analysis. Twenty-five of 29 (86%) patients with severe hypertension had improvement in their blood pressure on the same or fewer medications postoperatively (p = 0.0005). A retroperitoneal incision was associated with less intraoperative crystalloid fluid administration (p = 0.03), more rapid postoperative resumption of an oral diet (p = 0.04), and better long-term survival (p = 0.02) when compared with a transperitoneal incision. We conclude that the simultaneous repair of infrarenal aortic pathology and renovascular lesions is associated with an acceptable perioperative morbidity and preserves or improves renal function in the majority of patients. The frequent use of renal hypothermia and careful consideration of the route of operative exposure will lead to optimal results.

Aged↗
PubMed1993

Preservation of renal function in juxtarenal and suprarenal abdominal aortic aneurysm repair.

PURPOSE: Deterioration in renal function is a common cause of morbidity in patients treated surgically for juxtarenal and suprarenal abdominal aortic aneurysms. We reviewed our experience over the last 8 years with 65 consecutive patients undergoing juxtarenal (n = 31) or suprarenal (n = 34) abdominal aortic aneurysm repair. METHODS: The aneurysms were repaired with a transabdominal (n = 8), thoracoabdominal (n = 4), retroperitoneal (n = 22), or thoracoretroperitoneal (n = 31) approach. Proximal aortic clamps were placed at the suprarenal, supra-superior mesenteric artery, or supraceliac level. Renal hypothermia with cold heparinized saline solution renal artery perfusion was used to protect renal function in 38 patients with either preoperative renal insufficiency or with anticipated prolonged renal ischemia (> 30 minutes). Concomitant renal artery reconstruction was required in 30 patients. RESULTS: Significant operative morbidity developed in 23 (35.3%) patients. There was one (1.53%) perioperative death (0 to 90 days). Temporary dialysis was necessary in two patients. Preoperative renal insufficiency was a significant risk factor on multivariate analysis for a decline in renal function during the first postoperative week. However, serum creatinine concentration had returned to baseline or improved in all patients but two (3.1%) at the time of discharge. In spite of significantly longer renal ischemia, discharge creatinine levels were, on univariate analysis, statistically less than baseline creatinine levels in patients with suprarenal aneurysms, patients requiring renal reconstruction, and patients treated with renal hypothermia. The location of the proximal aortic clamp was not a factor in postoperative morbidity. There was no significant difference between juxtarenal and suprarenal aneurysms with respect to operating room time, transfusion requirements, days intubated, resumption of oral diet, or the length of hospitalization. CONCLUSIONS: Careful consideration of the route of exposure, location of the proximal aortic clamp, and the preservation of renal function with renal hypothermia and with the repair of significant renal artery lesions will result in minimal morbidity and mortality in patients requiring surgery for juxtarenal or suprarenal abdominal aortic aneurysms.

Aged↗
PubMed1992

Transvenous retrieval of misplaced stainless steel Greenfield filters.

Transvenous retrieval was attempted in five patients following surgical misplacement of stainless steel Greenfield filters. Four filters were located within the right atrium, and one was in the left hepatic vein. All retrievals were attempted within 5 days of placement. Retrieval was successful for the four filters in the right atrium and failed for the filter in the left hepatic vein. One air embolism occurred; this was the only filter- or retrieval-related complication. Transvenous retrieval is a safe and effective minimally invasive method of removing misplaced filters.

Female↗
PubMed1992

Detection of the source of arterial emboli by transesophageal echocardiography: a case report.

We report a case acute lower extremity ischemia caused by emboli in which the initial diagnostic evaluation, including standard aortoiliofemoral arteriography and routine transthoracic two-dimensional echocardiography, failed to reveal the offending source. Because of the strong clinical suspicion that the origin of the arterial occlusion was embolic, transesophageal echocardiography was performed. Transesophageal echocardiography demonstrated an aortic valvular lesion and cardiac surgery was performed on an emergency basis. The use of transesophageal echocardiography in evaluating the heart and thoracic aorta as a source of distal emboli is also discussed.

Aortic Valve↗
PubMed1992

An embolizing lesion in a minimally diseased aorta.

A case report of a patient with an unusual source of emboli resulting in acute limb-threatening ischemia is presented. Diagnostic angiography of the lower extremity was performed, followed by thromboembolectomy, which successfully restored normal arterial flow to the threatened leg. After surgery the patient underwent transesophageal echocardiography, which failed to identify an embolic source. Because of the high degree of clinical suspicion that the primary disease process was embolic rather than thrombotic, a thorough evaluation of the arterial tree was performed, including computed tomography and aortography. A large, mobile intravascular lesion arising from a normal descending thoracic aorta was identified and successfully treated with resection and graft placement.

Angiography, Digital Subtraction↗
PubMed1992

In situ saphenous vein for lower extremity revascularization.

BACKGROUND: During a 6-year period, 349 in situ saphenous vein bypass grafts were performed for limb salvage by three surgeons. METHODS: Outflow anastomoses were constructed to the infrageniculate popliteal (25%), posterior tibial (20%), peroneal (20%), anterior tibial (19%), and dorsal pedal arteries (7%). Mean patient age was 70 1/2 years. RESULTS: The 30-day mortality rate was 3.2%, and 19% died during the ensuing 68-month interval. At 1, 24, and 60 months primary graft patency was 89%, 77%, and 74%, secondary graft patency was 91%, 80%, and 78%, and cumulative limb survival was 94%, 88%, and 84%, respectively. Cumulative patency rates at 60 months depending on outflow site were as follows: popliteal (85%), anterior tibial (80%), posterior tibial (70%), dorsal pedal (68%), and peroneal (60%). Patency at the peroneal position was significantly inferior to that of other infrapopliteal sites combined (p less than 0.05). Cumulative limb survival at 60 months, according to outflow site, was as follows: popliteal (95%), anterior tibial (85%), posterior tibial (78%), dorsal pedal (73%), and peroneal (67%). There was no significant difference in limb salvage among infrapopliteal outflow sites. However, patency rates and limb salvage were significantly better for the popliteal outflow site than the infrapopliteal outflow sites (p less than 0.01). CONCLUSIONS: (1) A 5-year graft patency rate of 78% and a limb salvage rate of 84% are achievable, (2) peroneal bypass is associated with a lower rate for graft patency but not limb salvage, and (3) popliteal bypass has the best graft patency and limb salvage rates.

Aged↗
PubMed1990

Impact of glucose self-monitoring on non-insulin-treated patients with type II diabetes mellitus. Randomized controlled trial comparing blood and urine testing.

The goal of this study was to compare the relative efficacy and cost of self-monitoring of blood glucose (SMBG) with routine urine testing in the management of patients with type II (non-insulin-dependent) diabetes mellitus not treated with insulin. Fifty-four patients with type II diabetes mellitus, not treated with insulin, who had inadequate glucose control on diet alone or diet and oral hypoglycemic agents were studied. Patients performed SMBG or urine glucose testing as part of a standardized treatment program that also included diet and exercise counseling. During the 6-mo study, both the urine-testing and SMBG groups showed similar improvement in glycemic control; within each group, there were significant improvements in fasting plasma glucose (reduction of 1.4 +/- 3.2 mM, P less than 0.03) and glycosylated hemoglobin (reduction of 2.0 +/- 3.4%, P less than 0.01) levels. Seventeen (31%) of 54 patients actually normalized their glycosylated hemoglobin values, 9 in the urine-testing group and 8 in the SMBG group. Comparisons between the urine-testing and SMBG groups showed no significant differences in mean fasting plasma glucose (P greater than 0.86), glycosylated hemoglobin (P greater than 0.95), or weight (P greater than 0.19). In patients with type II diabetes mellitus not treated with insulin, SMBG is no more effective, but is 8-12 times more expensive, than urine testing in facilitating improved glycemic control. Our results do not support widespread use of SMBG in diabetic patients not treated with insulin.

Aged↗