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Biomedical subjects

S C Nicholls

Publications and source records attributed to S C Nicholls.

At least 19 recordsLinked to original sources
PubMed2001

Predicting death from ruptured abdominal aortic aneurysms.

BACKGROUND: We have previously reported preoperative and immediate postoperative formulae to estimate mortality in patients with ruptured abdominal aortic aneurysms (rAAA). In this study, we prospectively compared these formulae in patients with rAAA with their actual outcomes. METHODS: Information was collected on 134 patients from two centers over a 3-year period. Preoperative mortality risk was estimated using coefficients for age, level of consciousness, and cardiac arrest. Mortality risk in the immediate postoperative state was based on the presence of coagulopathy, ischemic colitis, prolonged requirement for inotropes, time from arrival at hospital to surgery, patient age, perioperative myocardial infarction, renal failure, and pre-operative hemoglobin level. RESULTS: The average age was 73 years (range 30 to 92 y) and 20 of 134 (15%) patients were women. Sixty-three patients (47%) survived. For patients with a calculated preoperative mortality risk of >90%, the sensitivity, specificity, and positive and negative predictive values were 25%, 98%, 95%, and 54%, respectively. For a mortality risk >80%, these values were 37%, 94%, 87%, and 57%, respectively. For patients with an estimated immediate postoperative mortality risk > or = 90%, the sensitivity, specificity, and positive and negative predictive values were 17%, 87%, 60%, and 49%, respectively. For a predicted mortality > or = 80%, these values were 22%, 84%, 60%, and 50%, respectively. CONCLUSIONS: Our formula for predicting mortality for preoperative rAAA patients may be useful for patients with an estimated mortality risk >/=90%, based on the high positive predictive value. The formula for immediate postoperative rAAA patients was not useful in predicting death.

Aged↗
PubMed2001

Seat belt aorta: endovascular management with a stent-graft.

PURPOSE: To report the endovascular treatment of a relatively uncommon type of deceleration injury to the abdominal aorta. CASE REPORT: A 21-year-old backseat passenger was wearing a single lap belt without shoulder harness when the car was involved in a collision. He sustained a transverse (Chance) fracture of the third lumbar vertebra and a circumferential dissection of the infrarenal abdominal aorta with pseudoaneurysm. As an interim measure while a stent-graft was obtained, a Wallstent was deployed to tack down the dissection and prevent distal embolization. Thirty-six hours later, an AneuRx endograft was successfully implanted inside the Wallstent to seal the pseudoaneurysm. The patient's recovery was uneventful, and the endograft remains secure and the pseudoaneurysm excluded at 10 months after the accident. CONCLUSIONS: Endovascular repair of "seat belt aorta" is a minimally invasive, straightforward method of management for this type of aortic injury. The potential for infection in a contaminated peritoneal cavity and the long-term outcome of this treatment have not been determined.

Adult↗
PubMed2000

Peripheral arterial embolization: Doppler ultrasound scan diagnosis.

Use of intraoperative monitoring with transcranial Doppler scanning during carotid endarterectomy has enabled identification of embolus signals in the ultrasound spectrum. Extension of this technique to preoperative screening has enabled identification of actively embolizing lesions and correlation with neurologic deficits. We report embolus signals in the peripheral circulation before operation, which aided diagnosis and decision to operate. The patient had been transferred from another institution after multiple revascularization procedures, including posterior tibial artery thrombectomy. Angiography performed on arrival at our institution confirmed an open bypass graft, although a small indentation was noted at the site of the previous posterior tibial artery thrombectomy. Runoff was intact to the plantar arch where there was attenuation of that vessel and occlusion of most digital branches. Duplex monitoring revealed no embolic signals in the graft or in the posterior tibial artery proximal to the previous arteriotomy. Distal to this site, embolic signals were detected. At the time of operation, a large platelet thrombus was identified at the site of the previous arteriotomy, and platelet thrombus was obtained from the plantar artery. It is concluded that doppler ultrasound scanning enables detection of peripheral embolization and the identification and location of lesions with such embolic activity. Diagnostic accuracy may be improved when there is clinical suspicion of embolization, enabling better patient selection for surgical procedures. This report provides the first clinicopathologic characterization of the emboli detected.

Amputation, Surgical↗
PubMed1999

Management of aortobronchial fistula with an aortic stent-graft.

Aortobronchial fistula presenting as massive hemoptysis is a rapidly fatal process that is extremely difficult to manage. We report a case in which endovascular occlusion of a fistula between a thoracic aortic pseudoaneurysm and lung was successfully managed by placement of an aortic endovascular stent-graft. Stent-grafting is a promising technique in managing complications of thoracic aneurysms and grafts.

Aged↗
PubMed1998

Rupture in small abdominal aortic aneurysms.

BACKGROUND: The decision of whether to repair small abdominal aortic aneurysms (AAAs), which are those that are less than 5 cm in diameter, remains controversial. METHODS: We describe 161 consecutive patients who were seen at a single urban hospital with ruptured AAAs (rAAAs) and in whom aneurysm size was measured with ultrasound scanning, or rarely computed tomography, en route to the operating room. Eleven patients (6.8%) had AAAs that measured less than 5.0 cm. This group was compared with 150 patients who had rAAAs that were more than 5 cm. RESULTS: The mortality rates were similar in both of the groups 70% for small rAAAs versus 66% for large rAAAs. No significant differences were seen between the patients with small and large ruptured aneurysms with respect to the prevalence rates of hypertension (60% vs 50%) or of cardiac disease (20% vs 22%). However, the prevalence rate of obstructive lung disease was significantly different (64% vs 25%; P =.02) as was the rate of diabetes (28% vs 3%; P =.004). Five aneurysms were measured at exactly 5 cm. This suggests that approximately 10% of all aneurysms that rupture in this series do so at 5 cm or less. CONCLUSION: In view of the safety of elective repair as compared with the prohibitive risk associated with aneurysm rupture, patients who are at good risk with small AAA (between 4 and 5 cm) should be considered for elective aneurysm resection. For unclear reasons, obstructive lung disease and diabetes are associated with a significantly greater risk for rupture of small AAA. Patients with these risk factors should be given special consideration.

Aged↗
PubMed1996

Venous thromboembolism: detection by duplex scanning.

PURPOSE: The usefulness of transcranial Doppler monitoring in identifying emboli in the arterial circulation has been established. We attempted to extend this technique to identify embolism in the venous circulation and to note any changes in embolism rate with anticoagulation. METHODS: From March to July 1993, 218 patients were evaluated by duplex scan for deep venous thrombosis. RESULTS: Sixty patients had positive study results; 26 scans (43%) demonstrated embolism. In five patients (19%) the emboli were also seen on a B-mode image, enabling us to estimate embolus size, which ranged from 200 to 5000 micrometer. Embolus counts varied from 5 to 800 per minute. Deep venous thrombosis was located in the iliofemoral vein in 2 patients, superficial femoral/profunda vein in 8, saphenofemoraal junction in 1, popliteal vein in 1, and the calf in 10. Concomitantly, studies in 158 patients were negative for deep venous thrombosis; embolism was detected in 4 patients (3%) in this group. In patients taking heparin, the embolus counts decreased 50% or more within 24 hours, and all embolism was abolished within 72 hours. Two patients died of pulmonary embolus. CONCLUSIONS: Patients with duplex scans that are positive for deep venous thrombosis have a high incidence of ongoing embolism. Heparin appears effective in eliminating the microemboli detected. The relationship among microembolism, deep venous thrombosis, and clinically significant pulmonary embolism remains to be elucidated.

Femoral Vein↗
PubMed1995

Transcranial Doppler and angiographic findings in adolescent stretch syncope.

The clinical, angiographic, and Doppler findings are reported for two young patients with recurrent syncope induced by neck hyperextension during stretching. Transcranial Doppler monitoring of both posterior cerebral arteries was performed during head manoeuvres. There were reproducible rapid decreases in blood flow velocities in both patients to an average of 28% and 41% of baseline values when they performed neck hyperextension. These decreases were regularly associated with the patients' symptoms and were not found during rotation or flexion. On return to a neutral head position there was a transient increase of the blood flow velocities to an average of 131% and 136% of baseline values (reactive hyperaemia). Routine four vessel angiography was normal except for the demonstration of very small posterior communicating arteries in one patient. Dynamic angiography showed evidence of extracranial compression of the craniocervical arteries in both patients. It is concluded that decreased blood flow to the posterior circulation is an important factor in the pathogenesis of adolescent stretch syncope.

Adolescent↗
PubMed1992

Flow separation in the carotid bulb: prognostic significance.

It has been previously shown that boundary layer or flow separation occurring in the carotid bulb and detected by duplex scanning denotes minimal or no carotid atherosclerotic disease as demonstrated by angiography and reliably predicts aetiology other than carotid artery disease in symptomatic patients. To evaluate outcome at long-term follow-up we prospectively studied 94 patients (48 males, 46 females) who demonstrated bilateral flow separation. Mean age was 61.2 years (27 to 86 years). Mean follow-up was 57 months (5 to 113 months). There was one death during follow-up at 69 months. It was stroke related. Using age and sex specific death rates for the general population 14.3 deaths would be expected for the same average period. By life table analysis, survival was 98.7% at five years compared to a general population expected 5 year survival of 85.9%. There were no strokes at 5 years of follow-up. (Age and sex specific stroke-free survival for Rochester, MN 1970-1974 is 98% at 5 years). TIA-free survival was 99% at one year (n = 87) and 96% at five years (n = 46). It is concluded that the presence of boundary layer separation in the carotid bulb not only indicates absent or minimal atherosclerotic disease, but is predictive of a favourable long-term outcome with respect to mortality and neurological events.

Age Factors↗
PubMed1992

Iliofemoral venous thrombosis following fascial excision of a deep burn of the lower extremity: case report.

Burned patients with deep venous thrombosis present a particularly perplexing challenge. They frequently require central venous catheters. Their altered skin integrity does not permit correlation with the typical changes described by the classic terminology for thrombophlebitis or its most severe forms, phlegmasia cerulea dolens or phlegmasia alba dolens. They are at risk of exsanguination or massive graft loss with lytic therapy or anticoagulation. Venous thrombectomy may be a necessary limb-saving surgical option.

Adult↗
PubMed1991

Clinical significance of retrograde flow in the vertebral artery.

Although retrograde vertebral artery flow was described over 100 years ago, its relationship to symptoms remains unclear. We documented 43 patients who were found by duplex scanning to have reverse flow in the vertebral artery. Of this group, seven patients (16%) were found to have symptoms described as typical for the "subclavian steal" syndrome. Nearly one-third were asymptomatic. Of the remaining patients, 13 (30%) presented with nonhemispheric symptoms while nine (21%) had hemispheric symptoms. Nine patients had "to and fro" flow in the vertebral artery. This variant was not found in subclavian steal patients but correlated with nonhemispheric symptoms. During follow-up (mean: 19 months) none of the asymptomatic patients became symptomatic, and there were no strokes or stroke-related deaths. Surgical procedures which restored antegrade vertebral artery flow did not necessarily improve symptoms of posterior circulation ischemia. In some patients improvement in posterior circulation symptoms was noted following carotid endarterectomy. It is concluded that retrograde flow in the vertebral artery is, per se, a benign entity. Accurate selection of surgical candidates remains imprecise. It will require not only identification of vertebrobasilar disease but as yet undefined tests to assure symptoms are due to these stenoses.

Follow-Up Studies↗
PubMed1991

Proteolytic processing of the Plasmodium falciparum merozoite surface protein-1 produces a membrane-bound fragment containing two epidermal growth factor-like domains.

The amino-terminal sequence has been obtained for 2 fragments of the Plasmodium falciparum T9/94 merozoite surface protein precursor (PfMSP1) and these have been compared with the sequence predicted from the gene. These data define the position of these fragments in the precursor and indicate that the C-terminal sequence which is carried into the red cell during invasion consists of 2 epidermal growth factor (EGF)-like domains. A homologous cleavage sequence and domain structure can be identified in the MSP1 molecules of other malarial species. In addition the results suggest that the smaller fragment is not N-glycosylated.

Amino Acid Sequence↗
PubMed1991

Ruptured abdominal aortic aneurysm: the Harborview experience.

During the last decade (1980 to 1989) 186 patients with ruptured abdominal aortic aneurysm were admitted to a single urban hospital. Ninety-six percent of these patients had a prehospital systolic blood pressure less than 90 mm Hg. Management included paramedic field resuscitation and transport, an emergency department diagnostic protocol completed in an average of 12 minutes, rapid transport to a dedicated emergency operating room, aneurysmorrhaphy by general surgery chief residents under the supervision of specialist vascular surgeons, and skilled postoperative intensive care unit care. Nevertheless, 130 (70%) patients died in the first 30 postoperative days--3% in the emergency department, 13% in the operating room, 51% in the intensive care unit, and 3% on the ward or at home. Certain features--age greater than 80 years, female gender, persistent preoperative hypotension despite aggressive crystalloid and blood replacement, admission hematocrit less than 25, transfusion requirements exceeding 15 units--were associated with a greater than 90% likelihood of death. No patient with preoperative cardiac arrest survived more than 24 hours. From this experience we conclude that, although "optimal" prehospital, emergency department, operating room, and postoperative care can improve the outcome of patients with ruptured abdominal aortic aneurysms in shock, most such patients will die. Certain clinical features predict such excessive mortality rates after ruptured abdominal aortic aneurysms that withholding operation may be reasonable. Screening of patients at high risk for abdominal aortic aneurysm, followed by elective aneurysmorrhaphy, is clearly indicated.

Aged↗
PubMed1990

Concurrent monitoring of brainstem auditory and somatosensory evoked potentials during carotid endarterectomy.

Intraoperative management of a 68-year-old man with a 3-month history of presyncopal attacks presenting for left carotid endarterectomy is reported. Preoperative angiograms revealed that the patient had a 90% stenosis of his left internal carotid artery and a 35% stenosis of right internal carotid artery, absent posterior communicating arteries, a totally occluded left vertebral artery, and a right vertebral artery that became compressed upon turning his head to the right, often precipitating the presyncopal attacks. The surgical procedure was managed with intraoperative monitoring of both brainstem auditory and somatosensory evoked potentials. The patient had an uneventful outcome. The anesthetic management is discussed.

Journal Article↗
PubMed1990

Detection of middle cerebral artery emboli during carotid endarterectomy using transcranial Doppler ultrasonography.

The purpose of our study was to define the signal characteristics and clinical circumstances associated with emboli detected in the middle cerebral artery using 2-MHz pulsed transcranial Doppler ultrasound in patients undergoing carotid endarterectomy. Signals designating emboli were transients displaying harmonic qualities the signatures of which were clearly different from those of mechanical and electronic artifacts. We reviewed the audio/video tape recordings from 91 patients for signals of air bubble emboli occurring upon release of common carotid artery crossclamps; recordings from 35 patients (38%) demonstrated air bubble emboli. Transients with signatures identical to those of air bubble emboli were also discovered when bubbles in the bloodstream were improbable; we defined these transients as representing formed-element emboli. Such signals were found in recordings from 24 patients (26%), and they occurred before (both spontaneously and upon common carotid artery compression), during, and after surgical dissection. Signals indicating formed-element emboli were associated with intraluminal platelet thrombus, with ulcerations in the carotid artery, and with transient ischemic attacks or stroke. Most postoperative formed-element emboli did not cause symptoms but, when persisting for hours, they were associated with strokes and cerebral infarction. This Doppler ultrasound method of detecting emboli will be useful in the study of stroke mechanisms and as a clinical test to guide the medical and surgical treatment of patients at risk of stroke.

Arterial Occlusive Diseases↗