Biomedical subjects
Publications and source records attributed to W S Smith.
Differentiation, defined as the discrimination of list membership, was studied with a recognition procedure. In each of the two studies, the number of learning trials was varied for one list and the trials on the other list were held constant. Differentiation was a U-shaped function of trials, passing through a minimum when both lists were shown equally often.
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Technically uncomplicated percutaneous angioplasty and stent placement of a left subclavian artery stenosis was performed in a 56-year-old man for treatment of subclavian steal syndrome and vertebrobasilar insufficiency. Six days later the patient was readmitted with Staphylococcus aureus bacteremia and stigmata of septic emboli isolated to the ipsilateral hand. Nine days later he had computed tomography (CT) evidence of a contrast-enhancing phlegmon surrounding the stent. Despite clinical improvement and resolution of bacteremia on intravenous antibiotic therapy, the phlegmon progressed, and at day 21 a pseudoaneurysm was angiographically confirmed. The patient underwent surgical removal of the stented arterial segment and successful autogenous arterial reconstruction. The possible contributory factors leading to stent infection were prolonged right femoral artery access and an infected left arm venous access. Although the role of prophylactic antibiotics remains to be defined, it may be important in cases where the vascular access sheath remains in place for a prolonged period of time.
PURPOSE: To determine the accuracy of acute stroke identification by paramedics in an urban emergency medical services system. METHODS: Retrospective chart review of all patient encounters by paramedics resulting in transport to two university hospitals during a six-month period. Subjects were identified by paramedic coding of stroke/transient ischemic attach (TIA) or final hospital discharge ICD-9 diagnosis of acute stroke and TIA. The sensitivity and positive predictive value for paramedic identification of stroke were calculated, and the time intervals from symptom onset to various points along the patients' prehospital and hospital courses were identified. RESULTS: Ninety-six patients were identified, of whom 81 met the diagnosis of acute stroke or TIA. Paramedics identified 49 of these 81 patients (sensitivity 61%). Fifteen patients were identified by paramedics as having a stroke when the patient ultimately had a different diagnosis (positive predictive value 77%) Patients or their families waited on average 2.5 +/- 3.6 (SD) hours before accessing 911, and a mean of 5.1 +/- 4.0 (SD) hours elapsed from symptom onset until head imaging studies were obtained. CONCLUSION: Paramedics in San Francisco County were correct three-fourths of the time when their documentation listed patients as having stroke/TIA. However, they did not identify 39% of stroke victims, a patient population who may benefit from urgent therapy. A substantial period elapses before stroke victims access 911. This highlights the need to develop an educational program for the community at risk for stroke, and another for paramedics directed toward more accurate identification of acute stroke victims.
OBJECTIVE: The authors have previously shown that San Francisco paramedics without specific training in stroke recognition identified acute stroke victims with a 61% sensitivity and a 77% positive predictive value (PPV). The authors implemented an educational program on stroke to improve paramedic accuracy in stroke recognition. METHODS: Twenty-two paramedics volunteered to attend a four-hour seminar about stroke and then were followed prospectively for six months. All encounters with adult patients who were evaluated by both trained and untrained paramedics and were transported to two university hospitals were reviewed. Subjects were identified by paramedic assessment as stroke/transient ischemic attack (TIA) and/or final hospital discharge diagnosis of stroke/TIA after detailed chart review. Sensitivity and PPV for paramedic identification of stroke were calculated. RESULTS: During the prospective six-month phase, 84 confirmed stroke patients were transported to the target hospitals. Of the 32 who were transported by trained paramedics, all but three were identified as having stroke/TIA, resulting in a sensitivity of 91%. This is significantly higher than the 61% previously found (p=0.01). Nontrained paramedics also increased their sensitivity to 90%. Thirty-eight false-positive patients were identified, resulting in PPVs of 64% for trained paramedics and 69% for all other paramedics. CONCLUSIONS: Institution of an educational stroke program was associated with a significant increase in sensitivity in stroke identification by the paramedics; however, educational influences outside this training program may have contributed to the increased sensitivity. Better education for paramedics, combined with rapid response to stroke victims once identified, may result in improved care for victims of acute stroke.
OBJECTIVE: Certain forms of stroke can be treated if access to medical care is expeditious. Since many stroke victims first enter medical care through emergency medical services (EMS) access, minimizing delays in the EMS system may translate to improved neurologic outcome. Because EMS dispatchers determine the response priority for these calls, dispatchers should be able to recognize the signs and symptoms of stroke based on their brief phone interviews. The authors studied the abilities of dispatchers in a major urban area to correctly identify stroke and transient ischemic attack (TIA) in victims who access 911 and describe what is communicated in the 911 call. METHODS: A retrospective review was conducted of the medical records of patients treated for stroke or TIA at two urban hospitals during 1996. The tape-recorded 911 calls from patients using EMS were transcribed and analyzed. Information regarding dispatcher classification and triage of these calls was collected and described. RESULT: The records of 182 patients with acute stroke or TIA were reviewed. Fifty-three percent of patients used EMS. Dispatchers coded 31% of their 911 calls as stroke. The word "stroke" was used without prompting by 51% of callers, yet fewer than half of these calls were coded as stroke by dispatchers. Many callers reported symptoms characteristic of stroke, including impaired communication (36%), weakness (30%), and decreased ability to stand or walk (25%). Only 41% of ambulances were sent at high priority. CONCLUSION: People who activate EMS for stroke frequently use the word "stroke" and/or describe symptoms compatible with stroke in their calls. EMS dispatch protocols should be sensitive for these symptoms to ensure more accurate and timely ambulance dispatch.
Pulmonary artery sarcomas are a rare and frequently forgotten cause of pulmonary artery occlusion. We present a case report that details magnetic resonance and new CT findings, which may help establish early diagnosis of this infrequently encountered tumor.
Numerous neurogenic tumors can affect the musculoskeletal system, including traumatic neuroma, Morton neuroma, neural fibrolipoma, nerve sheath ganglion, neurilemoma, neurofibroma, and malignant peripheral nerve sheath tumors (PNSTs). The diagnosis of neurogenic tumors can be suggested from their imaging appearances, including lesion shape and intrinsic imaging characteristics. It is also important to establish lesion location along a typical nerve distribution (eg, plantar digital nerve in Morton neuroma, median nerve in neural fibrolipoma, large nerve trunk in benign and malignant PNSTs). Traumatic and Morton neuromas are commonly related to an amputation stump or are located in the intermetatarsal space, respectively. Neural fibrolipomas show fat interspersed between nerve fascicles and are often associated with macrodactyly. Nerve sheath ganglion has a cystic appearance and commonly occurs about the knee. Radiologic characteristics of neurilemoma, neurofibroma, and malignant PNST at computed tomography (CT), ultrasonography, and magnetic resonance imaging include fusiform shape, identification of entering and exiting nerve, low attenuation at CT, target sign, fascicular sign, split-fat sign, and associated muscle atrophy. Although differentiation of neurilemoma from neurofibroma and of benign from malignant PNST is problematic, recognition of the radiologic appearances of neurogenic tumors often allows prospective diagnosis and improves clinical management of patients.
We present an unusual case of diabetes insipidus occurring after selective embolization of 50% dextrose and pure ethanol into an enlarged left meningohypophyseal trunk (MHT) supplying a dural carotid cavernous fistula. The inferior hypophyseal artery was not opacified during the selective preembolization MHT injection; however, diabetes insipidus developed abruptly a few hours after the procedure. The patient required intranasal 1-deamino-(8-D-arginine)-vasopressin for approximately 3 months, after which his symptoms resolved. The hazards of using liquid embolic agents, especially ethanol, in the cavernous branches of the internal carotid artery should always be borne in mind.
A new CT perfusion technique providing extended anatomic coverage was evaluated in 12 patients with suspected acute middle cerebral artery ischemia. With a multidetector CT scanner, scans were obtained in an alternating fashion at two distinct "toggling" table positions (two 1-cm sections each) during a 40-mL contrast agent bolus (approximately 5 seconds per image), and perfusion parameter maps were created. The CT perfusion results were compared with follow-up images. Nine patients showed focal perfusion abnormalities in at least one section, most commonly on mean transit time maps. Using a single table location would have underestimated or missed the involved tissue in most cases. In three of 12 patients, perfusion maps failed to delineate any abnormality. In two patients, perfusion and diffusion MR imaging confirmed the absence of perfusion abnormality and tissue injury, respectively. In one case, a small ischemic injury was revealed by diffusion MR imaging. By using the toggling-table approach, perfusion images can be obtained over an extended anatomic area and, thus, reveal the presence and the extent of presumed tissue injury.
BACKGROUND: The MERCI (Mechanical Embolus Removal in Cerebral Ischemia) trial reported efficacy of the Merci Retriever for opening intracranial vessels in patients ineligible for intravenous (IV) tissue plasminogen activator (tPA). Patients who receive IV tPA but do not recanalize may also benefit from thrombectomy, but the revascularization efficacy and safety of this strategy has not been reported. METHODS: Multi MERCI is an ongoing international, multicenter, prospective, single-arm trial of patients with large vessel stroke treated within 8 hours of symptom onset. Patients were enrolled who had received IV tPA but did not recanalize or who were ineligible for IV tPA. Primary outcome was vascular recanalization (Thrombolysis in Myocardial Infarction [TIMI] score II/III) and safety. RESULTS: One hundred eleven patients received the thrombectomy procedure. Mean age +/- SD was 66.2 +/- 17.0 years, and baseline National Institutes of Health Stroke Scale (NIHSS) score was 19 +/- 6.3. Thirty patients (27%) received IV tPA before intervention. Treatment with the Retriever alone resulted in successful recanalization in 60 of 111 (54%) treatable vessels and in 77 of 111 (69%) after adjunctive therapy (IA tPA, mechanical). Symptomatic intracranial hemorrhage (ICH) occurred in 10 of 111 (9.0%). Clinically significant procedural complications occurred in 5 of 111 (4.5%) patients. The symptomatic ICH rate was 2 of 30 (6.7%) in patients pretreated with IV tPA and 8 of 81 (9.9%) in those without (P > .99). CONCLUSIONS: Mechanical thrombectomy after IV tPA seems as safe as mechanical thrombectomy alone. Mechanical thrombectomy with both first- and second-generation Merci devices is efficacious in opening intracranial vessels during acute ischemic stroke in patients who are either ineligible for IV fibrinolytic therapy or have failed IV fibrinolytic therapy.
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