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Biomedical subjects

J W Norris

Publications and source records attributed to J W Norris.

At least 37 records · Page 2Linked to original sources
PubMed1998

Changing practice and costs of carotid endarterectomy in Toronto, Canada.

BACKGROUND AND PURPOSE: During our annual audits of carotid endarterectomy (CEA) in Toronto metropolitan hospitals, we have been aware of major changes in the practice of this operation in recent years. To evaluate the effect of changing practice on costs of carotid endarterectomy, we have therefore compared the effects of changes in length of stay, complication rates, and other variables on cost during the last 3 years for which we have complete data. METHODS: We evaluated 757 consecutive patients, of whom 600 had CEA procedures in 3 teaching hospitals, and 190 procedures in 2 community hospitals in metropolitan Toronto. We estimated costs using a specially designed computer program, Transitional System Incorporated, including surgical complications, in patients admitted between January 1994 and December 1996. RESULTS: There was a significant decrease in length of stay in both groups of hospitals, mainly due to preoperative outpatient evaluation but also due to lower complication rates, which probably reflect an increase in asymptomatic surgery in both hospital groups. Costs fell from approximately $8000 per procedure to $5000 in asymptomatic patients and from approximately $10,000 to $7000 in symptomatic patients (Can $). CONCLUSIONS: Major changes in the management of patients undergoing CEA have resulted in a significant decrease in both length of hospital stay and utilization of postoperative intensive care. At the same time, complication rates have significantly fallen, although our mortality and morbidity figures remain slightly higher than those from published multicenter trials. Future changes in surgical practice in Canada, including noninvasive carotid imaging, should produce even lower costs within the next few years.

Aged↗
PubMed1997

The nucleotide sequence of the translated and untranslated regions of a cDNA for myotoxin a from the venom of prairie rattlesnake (Crotalus viridis viridis).

Myotoxin a, isolated from C. viridis viridis venom, is a myonecrotizing agent present in many snake venoms. A cDNA library was prepared from mRNA obtained from the venom glands of a C. viridis viridis. The complete base sequence of a cDNA corresponding to an mRNA encoding myotoxin a was determined. The 5' untranslated region has 15 nucleotides, while the 3' untranslated region has 109 nucleotides. The translated portion of the myotoxin a cDNA encodes a start methionine, a signal peptide, the myotoxin a peptide sequence, and an additional lysine residue. It is likely that myotoxin a is secreted as the cDNA encodes a signal peptide immediately 5' to the myotoxin a peptide code.

Amino Acid Sequence↗
PubMed1997

Consensus against both endarterectomy and routine screening for asymptomatic carotid artery stenosis. Canadian Stroke Consortium.

BACKGROUND: Despite several randomized controlled trials, the role of carotid endarterectomy for asymptomatic patients is controversial. Validated evidence-based guidelines are needed. METHODS: Thirty-five members of the Canadian Stroke Consortium, an independent body of cerebrovascular disease experts, reviewed evidence-based guidelines developed by the Canadian Task Force on the Periodic Health Examination. We held 3 rounds of Delphi consensus to solicit opinion and agreement. RESULTS: We found a high level of interrater agreement for all guidelines using multiple statistical measures. Members agreed that evidence is insufficient to endorse carotid endarterectomy for asymptomatic patients with angiographically proven stenosis of more than 60% (kappa = 0.70, P < .01). Reasons cited included concern over the reproducibility of low surgical morbidity rates in the community at large, the questionable clinical benefit conferred by surgery, and the lack of proven reduction in the risk of major disabling stroke. Screening the general population for asymptomatic stenosis was unanimously rejected. Also, screening even patients with risk factors or proven atherosclerosis at other sites was not endorsed (kappa = 0.91 and kappa = 0.79, respectively, both P < .01). CONCLUSIONS: There is insufficient evidence to recommend carotid endarterectomy for asymptomatic patients. Evidence is also insufficient to endorse a screening strategy even for patients with risk factors for carotid disease. While stroke prevention remains a critical goal, we do not recommend that it be accomplished by screening or by performing carotid surgery in asymptomatic patients.

Canada↗
PubMed1997

Predictors of hemorrhagic transformation occurring spontaneously and on anticoagulants in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Hemorrhagic transformation (HT) is a common evolution of large-volume ischemic lesions, particularly of cardioembolic origin. We used transcranial Doppler ultrasound (TCD), single-photon emission computed tomography (SPECT) with 99mTc-hexamethylpropyleneamine oxime (HMPAO), and the Toronto Embolic Scale (TES) to decide (1) whether TCD, HMPAO-SPECT, and TES can improve on clinical and CT tests to predict spontaneous HT and (2) whether SPECT can help to predict the outcome of symptomatic HT. METHODS: Prognostic criteria included Canadian Neurological Scale (CNS) scores < or = 50 on admission, early ischemic changes on CT, M1 middle cerebral artery occlusion on TCD, the focal absence of brain perfusion on SPECT, and a high risk of cardiogenic embolism on TES. RESULTS: In part 1, 85 consecutive patients admitted within the first 6 hours were studied. No patient received thrombolysis. HT was found in 11 patients (13%) at 3 to 5 days. Admission CNS and CT were not predictive of HT: odds ratios (95% confidence intervals) were 0.49 (0.18 to 1.23) (P = .1) and 0.88 (0.23 to 3.45) (P = .8), respectively, TCD, SPECT, and TES were significant predictors of HT (P < .05), as follows: TCD, 8.67 (1.42 to 70.59); SPECT, 17.40 (2.69 to 170.89); and TES, 18.13 (2.6 to 406.86). In part 2, 490 consecutive patients were studied and 21 (4%) had symptomatic HT, of which 12 had focal hypoperfusion on SPECT at 4 days after stroke onset and 9 had focal hyperperfusion. Patients with hypoperfusion had larger CT lesions (115 +/- 97 versus 42 +/- 29 cm3; P = .04) and poorer outcome at 2 weeks (CNS, 38 +/- 45 versus 96 +/- 10; P = .001), including death (6/12 versus 0/9; P = .04); compared with those with hyperperfusion on SPECT. CONCLUSIONS: High risk of cardioembolism, M1 middle cerebral artery occlusion, and absence of collateral flow evaluated by TES, TCD, and SPECT help to identify patients at risk for spontaneous HT. Although TES was the most powerful predictor of HT, SPECT is the best single adjunct to the triage of clinical and CT tests. Patients with brain hyperperfusion on HMPAO-SPECT after symptomatic HT have better chances for recovery.

Anticoagulants↗
PubMed1997

Mass effect and death from severe acute stroke.

BACKGROUND: In severe acute stroke, the degree of midline cerebral displacement is related to level of consciousness but not to survival. Early identification of patients at high risk of death from mass effect would assist patient management decisions. METHODS: We measured lesion volume, horizontal pineal displacement (PD), and horizontal septum pellucidum displacement (SD) on axial CT of consecutive patients with severe (Canadian Neurological Scale score < or = 5) acute hemispheric stroke. We correlated CT measurements with the probability of 14-day survival. RESULTS: Forty-six (39%) of 118 patients died within 14 days and 72 (61%) died within 1 year following stroke. Crude risk factors for 14-day mortality were as follows: lesion volume > or = 400 ml, SD > or = 9 mm, PD > or = 4 mm, intraventricular hemorrhage, and coma on admission. Only SD (p = 0.001) and coma on admission (p = 0.019) remained significant in multivariate analysis, but PD was highly correlated with SD (r = 0.82). PD of > or = 4 mm on a scan performed within 48 hours of stroke onset identified patients with a low probability of 14-day survival (0.16; CI 0 to 0.32) with a specificity of 89% and a sensitivity of 46%. CONCLUSIONS: The degree of horizontal midline cerebral displacement correlates with the likelihood of death following stroke. Patients with > or = 4 mm PD on CT performed within 48 hours of stroke onset are at high risk for early death.

Acute Disease↗
PubMed1996

Carotid artery stenosis in peripheral vascular disease.

PURPOSE: The goal of the study was to assess the prevalence and severity of symptomatic and asymptomatic carotid artery disease in patients with peripheral vascular disease (PVD). METHODS: Consecutive patients with clinically and Doppler scanning-proven PVD (category 1 or greater) underwent prospective screening for the presence of carotid atherosclerosis with color-coded duplex ultrasonography. Preexisting risk factors were recorded with a standard questionnaire and included sex, age, diabetes mellitus, history of smoking, hypertension, prior stroke/transient ischemic attacks, and coronary artery disease. RESULTS: Three hundred seventy-three consecutive patients were studied over 2 years. The mean age of the patients was 70 +/- 10 years; there were 223 (60%) men and 150 (40%) women; 71% of the patients had a history of smoking, 47% had coronary artery disease, 43% had hypertension, and 21% had diabetes mellitus. Two hundred eleven (57%) patients had 30% or greater carotid artery stenosis detected by carotid artery duplex scanning. Sixty-seven (32%) of these had symptoms of ischemic cerebral events, of whom 22 had potentially operable carotid artery stenoses (70% to 99%), whereas 72 of the 144 symptom-free patients had 60% to 99% stenosis. An additional 34 patients would be eligible candidates for the ongoing carotid endarterectomy trials (North American Symptomatic Carotid Endarterectomy Trial and European Carotid Surgery Trial). Although all the risk factors were associated significantly with PVD and carotid artery disease (p < 0.002), male sex and prior stroke/transient ischemic attack were the strongest predictors. CONCLUSIONS: Routine carotid ultrasound screening of 373 consecutive patients with category I or greater PVD revealed that 22 patients with symptoms and 72 symptom-free patients were potential surgical candidates, representing 25% of the study cohort. An additional 34 patients were potential candidates for enrollment into the North American Symptomatic Carotid Endarterectomy Trial and European Carotid Surgery Trial.

Age Factors↗
PubMed1996

Agreement on disease-specific criteria for do-not-resuscitate orders in acute stroke. Members of the Canadian and Western New York Stroke Consortiums.

BACKGROUND AND PURPOSE: The do-not-resuscitate (DNR) order is a mechanism of withholding cardiopulmonary resuscitation (CPR). The lack of DNR guidelines specific for acute stroke may result in many stroke patients receiving unnecessary and futile resuscitation and ventilator-assisted breathing. METHODS: A prospective multicenter evaluation of disease-specific criteria for DNR orders in acute stroke was initiated using a modified Delphi process. The participants were the Canadian and Western New York Stroke Consortium members who are closely involved in caring for acute stroke patients and conducting clinical trials at the academic centers. Previously published provisional criteria were reviewed by the participants. Modifications were made to the criteria until statistically significant agreement (P < .05, z score, or 67% similar answers) was achieved. RESULTS: Disease-specific criteria for DNR orders in acute stroke were discussed by 26 physicians in three rounds of the opinion survey. An agreement was reached that a "no resuscitation" decision is appropriate when any two of the following three clinical criteria are present (the degree of agreement is given in parentheses): severe stroke (88%, P = .00007), life-threatening brain damage (73%, P < .01), and significant comorbidities (92%, P = .00003). The poor prognosis implied by these criteria should be discussed whenever possible among physician(s), the patient, and family members before the decision to withhold CPR is made. Eighty-one percent of the participants agreed that these disease-specific criteria are appropriate for clinical use (P = .0008). CONCLUSIONS: Disease-specific criteria for DNR orders were developed to supplement general DNR policies for patients with hemispheric brain infarction and intracerebral hemorrhage during the first 2 weeks of stroke. A significant agreement was reached by a panel of physicians that patients with acute stroke should not be resuscitated if these disease-specific criteria are met.

Acute Disease↗
PubMed1996

The clinical value of methods to measure carotid stenosis.

BACKGROUND: The North American (NASCET) and European (ECST) carotid surgery trials have shown a surgical benefit for symptomatic stenosis greater than 70%. The Asymptomatic Carotid Artery Surgery (ACAS) trial have shown some benefit for the stenosis greater than 60%. Although the NASCET/ACAS angiographic methods were similar, these are discrepant from ECST and have technical limitations inherent to measurement of the distal internal carotid artery (ICA) or guessing the ICA bulb diameter. METHODS: Consecutive carotid angiograms were analyzed to verify the relationships between proximal and distal aspects of the common carotid artery (CCA) and ICA bulb. We then compared the NASCET and ECST methods and, two new techniques, the Common Carotid (CC) and Carotid Stenosis Index (CSI). The CC method is based on a direct comparison of the residual lumen to the distal CCA diameter adjacent to the bulb. The CSI is based on the known relationship between the proximal CCA and ICA (1.2 x CCA diameter = proximal CCA diameter). The normal ICA bulb diameter can therefore be calculated from direct measurement of the CCA. RESULTS: 125 consecutive carotid angiograms were evaluated (250 arteries). Technical applicability of NASCET was 89%, ECST 95%, CC/CSI 99%. The CCA/ICA diameter ratios were established: 1.23 +/- 0.23 (ICA bulb/distal CCA), and 1.27 +/- 0.2 (ICA bulb/proximal CCA). The CCA is enlarged at its distal end that such the distal CCA/proximal CCA ratio is 1.04 +/- 0.12. The CC and CSI methods were statistically different in 8 of 10 groups when these methods were compared per decile stenosis (p < 0.04). However, CC and CSI methods disagreed in classifying patients into mild (0-29%), moderate (30-69%), and severe (70-99%) only in 3%, 5%, and 8% of cases. Linear regression analysis shows excellent correlation between the methods (CC = 15.7 + 0.82 x CSI, r2 = 0.92). Lumen asymmetry is most common with mild-to-moderate stenoses which may affect accuracy and reproducibility of measurements. CONCLUSIONS: We have confirmed previous data on the relationships between the components of the carotid artery. Of the different angiographic techniques, CSI is the most reliable validated method of measuring carotid stenosis, and is proposed as a bridge between results of carotid surgery trials, and to validate noninvasive modalities against angiography.

Angiography, Digital Subtraction↗
PubMed1995

Noninvasive assessment of intracranial perfusion in acute cerebral ischemia.

Single-photon emission computed tomography (SPECT) and transcranial Doppler sonography (TCD) may help to determine a target group of patients with maximum therapeutic response for tissue rescue after acute stroke. As previously described, the cerebral perfusion index represents a combination of these techniques, and is calculated by multiplying assigned values for TCD and SPECT perfusion patterns. The three grades of cerebral perfusion index (1-5, 6-12, 15-20) may predict short-term outcome if the index is based on SPECT and TCD performed within the first 6 hours after stroke. A total of 30 consecutive patients were studied (18 with middle cerebral artery stroke and 12 with transient ischemic attack or minor stroke). Neurological deficit was scored using the Canadian Neurological Scale. SPECT and TCD were performed 4 +/- 2 hours after the onset. Forty-five minutes were required to perform both tests, evaluate the results, and calculate the cerebral perfusion index. The mean score (+/- standard deviation) of the neurological deficit on admission was 84 +/- 20 in patients with transient ischemic attack/minor stroke and 54 +/- 33 in patients with stroke (p < 0.009). The volume of ischemic lesion was measured on computed tomography scans performed more than 3 days after the ictus. Patients with transient ischemic attack/minor stroke had lesion volumes of 8 +/- 7 cm3 compared to 72 +/- 26 cm3 for those with stroke (p < 0.0001). The mean cerebral perfusion index in the transient ischemic attack group was 18 +/- 4, while in the stroke group it was 4 +/- 1 (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1995

Carotid Stenosis Index. A new method of measuring internal carotid artery stenosis.

BACKGROUND AND PURPOSE: Current methods of measuring carotid stenosis such as those used in the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) have limitations caused by difficulties in measuring the normal width of the distal internal carotid artery (ICA) or the carotid bulb. METHODS: We developed a new technique, the Carotid Stenosis Index (CSI), based on the known anatomic relationship between the common carotid artery (CCA) and ICA (1.2 x CCA diameter=proximal ICA diameter). The normal ICA diameter can therefore be calculated from direct measurement of the CCA. Three blinded observers evaluated the angiograms of 57 patients (114 carotid arteries), previously screened with duplex ultrasonography, using the NASCET, ECST, and CSI methods. In a subset of 30 patients undergoing carotid endarterectomy, comparison was also made to computerized carotid plaque planimetry. RESULTS: The NASCET method could only be applied correctly in 89% and the ECST method in 95% of cases because of overlying vessels or inadequate views of the distal ICA or carotid bulb. An additional 9% of NASCET cases had a "negative" stenosis, in which the stenosis is wider than the distal ICA. The CSI method was applicable in 99% of cases. Interobserver comparison using ANOVA revealed significant differences using NASCET (P < .0001) and ECST (P <.001) but not CSI (P = NS). NASCET had a sevenfold variation (P < .01) and ECST a twofold variation (P < .01) in results compared with CSI. The intraobserver reliability was 0.87 for NASCET, 0.86 for ECST, and 0.90 for CSI. However, the 95% confidence intervals for an individual measurement by an observer were +/- 30% for NASCET, +/- 19% for ECST, and +/- 15% for CSI. With linear methods of measurement there were significant differences between NASCET and CSI (P < .0001) and ECST (P < .0001) but not between CSI and ECST. A comparison of area derivations of these methods to carotid plaque planimetry revealed significant differences from NASCET (P <.0001) but not ECST, CSI, or duplex methods. A CSI nomogram was created, allowing measurement of both linear and area percent stenosis. CONCLUSIONS: CSI is the most reliable validated method of measuring carotid stenosis, and it correlates with duplex and carotid pathology.

Carotid Artery, Common↗
PubMed1995

Do-not-resuscitate orders in acute stroke.

Although the general guidelines for do-not-resuscitate (DNR) orders apply to acute stroke patients, few data are available to aid decision-making. With a view to developing specific guidelines for use in patients with acute stroke, we decided to evaluate the clinical factors associated with DNR orders at our university teaching hospital. We prospectively studied 450 consecutive patients with acute hemispheric strokes (237 men and 213 women, mean age 75 +/- 12 years). Thirty-six patients (8%) had intracerebral hemorrhage (ICH) and 414 (92%) had ischemic strokes. Overall inhospital mortality was 26%. DNR status was given to 31% of all patients at some time during their admission (83% of those died). DNR decision-making was closely associated with the severity of the neurologic deficit (Canadian Neurological Scale score < or = 5); the patient's incapacity for informed DNR decision-making; age (> 60 years); and devastating ICH unsuitable for surgery (p < 0.001). Fifty-three percent of DNR orders were given on admission (first 24 hours of the hospital stay), 35% during the first week of the hospital stay, due to brain damage, and 12% at any time between days 8 and 44 due to systemic complications. Once DNR status was given, 53% of patients continued to receive normal nutrition and 60% still received medical or surgical treatment. Although the current practice of DNR orders in patients with acute stroke is generally satisfactory, some criteria (eg, age and operable ICH) need revision.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗