Search PubMed⌕ Search

Biomedical subjects

K R Lees

Publications and source records attributed to K R Lees.

At least 109 records · Page 6Linked to original sources
PubMed1995

A pilot study of streptokinase for acute cerebral infarction.

We evaluated intravenous streptokinase in the treatment of cerebral infarction. Following neurological assessment and cerebral computed tomography (CT), patients aged 40-80 years with symptoms of anterior circulation acute ischaemic stroke were given 1.5 M units streptokinase or saline placebo in a double-blind randomized study. Twenty patients (10 streptokinase, 10 placebo), 11 males, 9 females, aged 57-79 years, were treated out of 512 consecutive admissions to the acute stroke unit over a 2-year period. Initial CT was normal in 11 (6 placebo, 5 streptokinase) and showed early signs of cerebral infarction in nine (4 placebo, 5 streptokinase). Median times from symptom onset to treatment were 5.2 h (placebo) and 5.8 h (streptokinase). Streptokinase treatment was associated with symptomatic hypotension in one patient. Repeat CT at 72 h demonstrated intracerebral haematoma in two patients and haemorrhagic infarction in one patient in the streptokinase group; the two cases of haematoma formation were associated with neurological deterioration and death. One patient in the placebo group had evidence of haemorrhagic infarction at 72 h. There were three deaths in each treatment group, all within the first 14 days. Patients with acute stroke can be evaluated with CT and treated with streptokinase within 6 h, but the opportunity for treatment is currently limited to few patients. Streptokinase treatment is not without risk, but potential clinical benefit justifies ongoing multicentre randomized trials.

Acute Disease↗
PubMed1995

Transcranial Doppler ultrasound signals associated with prosthetic heart valves: an in vitro study.

The application of transcranial Doppler (TCD) ultrasonography to asymptomatic prosthetic heart valve patients can result in detection of localized bursts of high intensity signals, similar to those caused by the passage of emboli. The origin of these signals is not known. In order to investigate this phenomenon in a simplified, more controllable environment, a TCD machine was used to record flow downstream from mechanical prosthetic heart valves in a mock circulatory loop. The model, which uses a saline solution seeded with silk particles (< 15 micrometers) as the circulatory fluid, recreates the principal hydrodynamic characteristics of the left heart and systemic circulation. Reproducibility of the system was established through repeated testing of a Monostrut valve. Three different mechanical valve types, (Monostrut, Medtronic Hall, St. Jude Medical) were tested over a range of simulated cardiac outputs, and the effect of valve size was investigated with four Omniscience tilting disc valves (21, 23, 25 and 29 mm). Average energy of the reflected Doppler signal was used to quantify the amount of high intensity Doppler signal, QTCD. TCD signals recorded in vitro were visually and aurally similar to those found in prosthetic heart valve patients. All valve types generated exponentially more QTCD with increasing simulated cardiac output. Differences amongst valve types were only significant at higher flow outputs, with the Monostrut valve producing the greatest QTCD. Larger valves consistently generated greater QTCD than smaller valves. In conclusion, TCD signals found in prosthetic heart valve patients can be reproduced, at least qualitatively, using a mock circulatory loop which does not incorporate the formed elements of blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1995

Transcranial Doppler ultrasound in commercial air divers: a field study including cases with right-to-left shunting.

Many cases of decompression illness occur in divers using recommended decompression tables. Doppler ultrasound has been used for over 20 yr and has shown the presence of venous bubbles in asymptomatic divers working well within decompression limits. Previous studies have demonstrated an increased prevalence of patent foramen ovale in divers who have suffered neurologic decompression illness. It has been postulated that right-to-left shunting through a patent foramen ovale could allow arterialization of these bubbles, causing symptoms and signs of acute decompression illness and possibly chronic subclinical neurologic impairment. We set out to determine the incidence of bubbles in the cerebral circulation of commercial divers decompressing from air dives. Using transcranial Doppler ultrasound (TCD), the middle cerebral arteries of 17 divers were monitored after surfacing from depths ranging between 3 and 50 m. Peripheral contrast injection with simultaneous transthoracic echocardiography and TCD was used to screen for right-to-left shunting. Right-to-left shunting was detected in four divers by TCD (one at rest, two after a Valsalva maneuver, and one only after coughing); however, echocardiography was positive in only one of these subjects after a Valsalva maneuver (TCD was positive at rest in this subject). Seventy-three TCD recordings were performed in four settings: 41 after underwater decompression, 18 after surface decompression, 10 in the interval between surfacing and entering the decompression chamber, and 4 after a chamber dive. Twenty-three of these recordings were in four subjects with right-to-left shunting; no bubbles were detected in any of these recordings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

On the origin of cerebrovascular microemboli associated with prosthetic heart valves.

Application of transcranial Doppler ultrasonography to asymptomatic prosthetic heart valve patients can result in the detection of transient high intensity signals, similar to those induced by the passage of emboli. However, the origin of these signals is unknown. An in vitro study has been undertaken to investigate the capacity of prosthetic heart valves to generate high intensity Doppler signals in the absence of blood. A pulse duplicator, filled with a seeded saline solution, was used to function prosthetic heart valves under mock-physiological conditions. A Björk-Shiley Monostrut valve was mounted in the aortic port while a tri-leaflet control valve was fixed in the mitral port. At stations upstream and downstream from the Björk-Shiley valve, flow was monitored using pulsed wave Doppler ultrasound (Nicolet TC-2000, 2 MHz probe). The effect of damping the harsh closure of the mechanical valve was investigated by applying a thin layer of soft adhesive tape between the valve occluder and outer ring. For all valve configurations, transient high intensity Doppler signals, characteristic of microemboli and similar to those observed in clinical studies of prosthetic heart valve patients, were detected downstream from the aortic port. The number of microemboli signals did not change significantly between sites at 20 cm and 40 cm downstream from the aortic valve. Damping the Björk-Shiley valve closure greatly reduced (by 80%) the number of microemboli signals detected. It is concluded that Doppler microemboli signals can be generated by prosthetic heart valves while functioning in the absence of the formed elements of blood, and that the number of microemboli signals produced depends upon the rate of energy dissipation at valve closure.

Aortic Valve↗
PubMed1995

Lack of association between angiotensin converting enzyme gene insertion/deletion polymorphism and stroke.

AIM: The human angiotensin converting enzyme (ACE) gene is a candidate genetic locus for stroke because of the importance of the renin-angiotensin system to the development of cardiovascular disease. In the present study, the association between ACE gene deletion/insertion (D/I) polymorphism and the presence or absence of ischaemic stroke was evaluated and possible associations between ACE gene polymorphism and certain subgroups of stroke were investigated. MATERIALS AND METHODS: DNA samples from 585 unselected suspected stroke patients admitted to the Acute Stroke Unit, Western Infirmary, Glasgow, and from 188 age- and sex-matched controls were genotyped by polymerase chain reaction. RESULTS: There was no evidence of any association between ACE gene polymorphism and the presence of ischaemic stroke except in the subgroup containing only hypertensive patients, where the odds ratio of a DD genotype for ischaemic stroke was just significantly greater than 1 (odds ratio 2.51, 95% confidence interval 1.06, 5.94). There was no significant association between ACE genotype and the stroke subgroups investigated. CONCLUSION: The DD genotype may not be a risk factor for stroke, particularly in the normotensive population. Further study in a strictly controlled population is required to test for the possibility of an increased risk of stroke in hypertensives with DD homozygotes.

Cerebrovascular Disorders↗
PubMed1994

Neuroprotective effect of remacemide hydrochloride in focal cerebral ischemia in the cat.

The neuroprotective effects of remacemide hydrochloride ((+/-)-2-amino-N-(1-methyl-1,2-diphenylethyl)acetamide hydrochloride) have been assessed with permanent occlusion of one middle cerebral artery in chloralose-anesthetized cats in which key physiologic variables have been monitored throughout the post-ischemic period. An infusion of remacemide hydrochloride (278 micrograms/kg/min; total dose 25 mg/kg) initiated 90 min prior to middle cerebral artery occlusion and discontinued at occlusion, reduced significantly (P < 0.02) the volume of ischemic damage (from 2505 +/- 454 mm3 of vehicle-treated cats to 1266 +/- 54 mm3 of remacemide hydrochloride-treated cats).

Acetamides↗
PubMed1994

Poor accuracy of stroke scoring systems for differential clinical diagnosis of intracranial haemorrhage and infarction.

The differentiation of cerebral infarction and cerebral haemorrhage is the most important first step in the management of acute stroke, because clinical management of the two disorders differs substantially. The Guy's Hospital and Siriraj stroke diagnostic scores were developed to aid clinicians in this decision. We have tested the performance of the two scores on a group of 1059 patients admitted to the acute stroke unit (ASU) at the Western Infirmary, Glasgow, with suspected stroke between May, 1990, and December, 1993. The diagnosis was confirmed as stroke by computed tomography (CT) scanning or necropsy (n = 10) in 991 patients. For each clinical score we subjectively identified the cut-off point that maximised sensitivity to cerebral haemorrhage with the smallest loss of specificity. At its optimum cut-off point the Guy's Hospital score had a sensitivity for the diagnosis of haemorrhage of 70% and specificity of 64%. The corresponding figures for the Siriraj score at its optimum cut-off point were 68% sensitivity and 64% specificity. The overall predictive accuracy of both scores was 64%. The greater complexity of the Guy's Hospital score (thirteen variables included) did not result in substantially superior performance to the Siriraj score (five variables). This validation study suggests that neither score is useful for exclusion of haemorrhage before anticoagulant treatment is initiated or as a diagnostic screening procedure for trials of low-risk treatments such as aspirin. Our findings emphasise the need for routine CT scanning in this setting, since this method remains the most accurate for differentiating between haemorrhage and infarction.

Acute Disease↗
PubMed1994

Anticardiolipin antibodies in an unselected stroke population.

A pathogenetic role in thrombotic disease, particularly in young people, has been postulated for anticardiolipin antibody (ACA). We have carried out a prospective controlled study of 262 unselected patients with acute stroke and 226 controls to assess the prevalence and relation to age and vascular risk factors of ACA. Titres of IgG, IgA, or IgM ACA were above the upper normal limit in 38% of patients. The proportions of patients and controls with raised titres did not differ significantly (13 vs 8% IgG, 22 vs 29% IgA, 11 vs 7% IgM). IgG titres were higher among patients than among controls (mean 3.88 vs 2.86 u/mL [95% CI for difference 0.62-0.87], p = 0.0004), whereas IgA and IgM titres were lower in patients than in controls (IgA 4.82 vs 5.98 u/mL [1.12-1.60], p = 0.01; IgM 3.00 vs 3.64 u/mL [1.01-1.45], p = 0.04). However, within age tertiles the only significant difference between patients and controls for IgG ACA was in the oldest tertile. Analysis by number of risk factors for stroke showed a significant difference between the groups only for subjects with one risk factor. IgA and IgM ACA titres were higher among controls only in those with no vascular risk factors. We found no evidence to support the hypothesis that ACA is an independent risk factor for stroke in young people. The increase in IgG titre with age and number of vascular risk factors in stroke patients suggests that ACA may be a non-specific accompaniment of vascular disease. Routine testing for ACA in stroke patients is not justified.

Acute Disease↗
PubMed1994

Subclinical embolism in patients undergoing cardiac valve implantation and coronary artery bypass surgery.

Patients undergoing prosthetic valve insertion and coronary artery bypass surgery were examined with transcranial Doppler ultrasound, recently shown to be capable of detecting continuing subclinical emboli in patients with embolic sources. In 30 patients examined at least 1 year after valve surgery, and in whom warfarinisation was stable within defined limits, 20 of 24 patients (83%) with mechanical valves and 3 of 6 patients (50%) with porcine valves had embolic signals. In a serial preoperative and postoperative study in a further 30 patients, of whom 29 had native or bioprosthetic valves, only the one patient with a previous mechanical mitral valve prosthesis had embolic signals preoperatively. The incidence of embolic signals increased to 9 (30%) on the first postoperative day, and 20 (67%) on day 5. In a similar serial study in 25 patients undergoing coronary bypass surgery, 8 (32%) had preoperative embolic signals, which were explicable by cardiac and/or carotid disease in 6 cases. The embolus signal incidence and count did not increase postoperatively in this group. No embolic signals were found in 15 volunteer controls. The results indicate that prosthetic valves cause continuing microembolisation, detectable by transcranial Doppler; coronary artery bypass cases may have incidental embolic signals which are unaffected by cardiac surgery. This new application of Doppler ultrasound may improve the clinical assessment of embolic risk of new prosthetic valve types and deserves further examination.

Adult↗
PubMed1994

Detection of intracranial emboli in patients with carotid disease.

Transcranial Doppler emboli signal detection has been reported in several patient groups, including patients with symptomatic internal carotid artery stenosis. The potential of this technique in assessing embolic risk and selecting patients for surgery was examined in this study. Selected patients with symptomatic internal carotid artery stenosis underwent combined extracranial and transcranial Doppler study in the Vascular Surgery and Neurovascular Unit. Patients and normal controls were monitored with transcranial Doppler over both middle cerebral arteries. Severity of carotid disease was diagnosed with colour Duplex ultrasound examination or angiography. Selected patients underwent cranial computed tomography and transthoracic echocardiography. Patients undergoing carotid endarterectomy were re-examined one month after surgery. Fifty symptomatic patients, six asymptomatic patients and 30 normal controls were examined. Carotid disease was unilateral in 34 and bilateral in 22 cases. Emboli signals were detected in 94% of patients. The emboli signal count in patients with unilateral carotid stenosis was significantly higher in the middle cerebral artery distal to the stenosed internal carotid compared to the contralateral middle cerebral artery [14 (10-22) versus 2 (0-7) signals per hour, median and 95% confidence intervals, p < 0.001] and in symptomatic compared to asymptomatic cerebral hemispheres [15 (11-21) versus 4 (2-9) signals per hour, p < 0.001]. Emboli were detected in the contralateral middle cerebral artery in 40% of patients with unilateral carotid disease, in 85% of whom an additional embolic source was identified. No emboli signals were detected after carotid endarterectomy distal to the operated internal carotid, or in any of the normal controls. In conclusion, intracranial emboli signals are common in patients with carotid stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Pharmacological effects of the non-competitive NMDA antagonist CNS 1102 in normal volunteers.

1. Non-competitive antagonists at the glutamatergic N-methyl D-aspartate receptor significantly reduce the volume of ischaemic cerebral infarction in animals and are potential agents for the treatment of acute stroke in humans. 2. CNS 1102, a novel non-competitive NMDA antagonist, was administered as a 15 min intravenous infusion to healthy male volunteers in a double-blind, placebo-controlled, dose-ranging study. This was the first administration to man. 3. Clinically significant sedation, increased mean arterial pressure and pulse rate were seen at doses of 30 micrograms kg-1 and above. Symptoms of sedation and central nervous excitation became unacceptable for conscious individuals at doses of 45 micrograms kg-1 and above. 4. Rapid onset of central nervous system effects after administration is in keeping with rapid distribution of CNS 1102 to brain. Steady state volume of distribution was large (444 l) and terminal elimination half-life from plasma was approximately 4 h. 5. Pharmacokinetic properties are favourable for a potential neuroprotective therapy. The maximum tolerated dose for conscious individuals was 30 micrograms kg-1 given intravenously over 15 min. Further assessment of CNS 1102 should seek methods of drug administration which maximise administered dose with minimal side effects.

Adult↗
PubMed1994

Haemodynamic response and pharmacokinetics after the first dose of quinapril in patients with congestive heart failure.

1. Twenty-four elderly patients with stable, chronic congestive heart failure, NYHA II-IV, requiring addition of an ACE inhibitor to their existing therapy were randomised to receive double-blind a single dose of quinapril 2.5 mg p.o. or matching placebo after 24-48 h supervised diuretic withdrawal. 2. The effect of treatment on resting supine blood pressure, heart rate, plasma angiotensin converting enzyme (ACE) and circulating plasma renin activity was compared between groups over the first 24 h after dosing. The pharmacokinetic profiles of quinapril and the active metabolite quinaprilat were determined. 3. Compared with placebo, quinapril caused a statistically significant but modest fall in blood pressure from 3 to 10 h post dose. The maximum fall of 12 mm Hg (95% C.I. 5.4-18.5) was seen at approximately 5 h. Circulating ACE activity was 40% inhibited within 1 h. Maximum ACE inhibition (83.6%, 95% C.I. 76.7-90.5) was observed at 3 h. ACE remained 60% inhibited at 24 h post dose. tmax for quinapril was seen at 2.6 +/- 1.2 h. while tmax for quinaprilat was at 3.6, +/- 0.8 h. 4. Treatment with quinapril was associated with a significant rise in plasma renin activity (PRA) of 8.83 ng AI ml-1 h-1 (95% C.I. 0.30-17.96) compared with placebo. 5. Compared with placebo, quinapril 2.5 mg inhibits plasma ACE by over 60% for 24 h and reduces blood pressure for at least 10 h in patients with stable, chronic congestive heart failure. The blood pressure fall, although moderate and well tolerated, is more sustained than previously described for quinapril in heart failure.

Aged↗
PubMed1994

Responses to low dose intravenous perindoprilat infusion in salt deplete/salt replete normotensive volunteers.

1. Intravenous ACE inhibitor therapy appears to have a role in the treatment of acute heart failure and early after myocardial infarction. Practical experience with intravenous administration with activation of renin is limited. We report responses to perindoprilat (Pt, 0.67 mg) or placebo (P) infused over 4 h in normotensive male volunteers (n = 12, 19-28 years, 53-77 kg) with double-blind, placebo controlled salt depletion (SD) or salt repletion (SR) as a model of the activated renin system. 2. Salt depletion caused no significant fall in serum sodium (P, 139.4 +/- 2.4; Pt, 138.3 +/- 1.9) compared with salt replete preparation (P, 139.9 +/- 1.2; Pt, 139.7 +/- 0.9) but elevation of plasma renin activity 2-3-fold. Pretreatment baseline systolic blood pressure following salt depletion (P, 121 +/- 9.3/71 +/- 7.9; Pt, 121.5 +/- 9.6/69 +/- 8.1) was higher than following salt replete preparation (P, 114 +/- 9.5/61 +/- 7.2; Pt, 116.9 +/- 6.9/67 +/- 7.2). 3. Baseline corrected supine SBP fell significantly and to a similar extent following active treatment regardless of activation of the renin system (SD, -14.6 +/- 9.5/-9.4 +/- 6.4; SR, -12 +/- 14/-10.1 +/- 6.6) compared with placebo (SD, -6.1 +/- 6/-3.7 +/- 5.6; SR, -4.7 +/- 10/-1.3 +/- 6.5). Heart rate was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Doppler emboli signals vary according to stroke subtype.

BACKGROUND AND PURPOSE: Doppler ultrasound detection of emboli signals may assist in distinguishing embolic from thrombotic stroke. Selected patient groups have a high incidence of such signals. We have examined consecutive stroke cases to identify the incidence of Doppler emboli in different etiologic subtypes of stroke. METHODS: Forty-five patients presenting with first-ever acute carotid territory cerebral ischemia were studied prospectively. Transcranial Doppler examination of both middle cerebral arteries, carotid color duplex ultrasound, and transthoracic or transesophageal echocardiography were completed within 48 hours of deficit onset. Clinical and imaging data were interpreted independent of emboli data, and stroke etiology was classified according to recent multicenter trial criteria. RESULTS: Middle cerebral artery signals were identified in at least one cerebral hemisphere in 41 of the 45 patients. Emboli signals were present in 29 of these 41 cases (71%). These signals were bilateral in 22, within the affected (symptomatic) cerebral hemisphere only in 5, and contralateral only in 2 cases. No emboli signals were detected in any of 8 patients with lacunar stroke. The overall difference in emboli signal counts between etiologic subgroups was significant (P = .001, Kruskal-Wallis). A significantly higher emboli signal count was found within affected cerebral hemispheres than contralaterally in the 8 patients with large artery atherosclerosis (11.3 versus 1 signals per hour, median [95% confidence interval, 3 to 40 and 0 to 3, respectively], P = .02), but this interhemisphere difference was not present for other etiologic subgroups. CONCLUSIONS: Emboli signals are common in patients with acute stroke, with the notable exception of lacunar stroke. This is consistent with the small vessel etiology for the latter group and provides support for the relevance of Doppler emboli signal detection in thromboembolic cerebrovascular disease.

Adult↗
PubMed1994

Prevalence and characteristics of intracranial microemboli signals in patients with different types of prosthetic cardiac valves.

BACKGROUND AND PURPOSE: Transcranial Doppler detection of microemboli is widely described, but there is no clear evidence of the clinical significance or nature of the embolic material in vivo. Thromboembolism is a major cause of morbidity in patients with prosthetic cardiac valves. We undertook this study to evaluate the prevalence and the acoustic characteristics of microembolic signals in three groups of patients with different prosthetic valves. METHODS: One hundred seventy-nine patients with prosthetic cardiac valves (85 Björk-Shiley, 56 Medtronic-Hall, and 38 Carpentier-Edwards) and 25 normal subjects were examined using transcranial Doppler. Monitoring time was 30 minutes over the right middle cerebral artery. RESULTS: The prevalence and numbers of embolic signals were significantly higher in patients with Björk-Shiley compared with those with Medtronic-Hall and Carpentier-Edwards valves (89% versus 50% and 53%, respectively; P < .001, chi 2; 156 [112, 204] versus 2 [1, 4] and 2 [1, 4] signals/h, respectively; median [95% nonparametric confidence interval], both P < .001, multiple comparisons, Bonferroni correction). The signal intensity was significantly higher in patients with Björk-Shiley and Medtronic-Hall valves than patients with Carpentier-Edwards valves (2435 [2345, 2527] and 2120 [1745, 2483] versus 225 [184, 287] power units, median [95% confidence interval], both P < .001). No correlation was found between embolic signal numbers and clinical parameters including history of neurological deficit, cardiac rhythm, duration of artificial valve, previous cardiac operations, or intensity of anticoagulation. Embolic signals were not detected in any of the control subjects. CONCLUSIONS: Our data showed that the prevalence, quantity, and acoustic characteristics of Doppler embolic signals differ in patients having three different types of prosthetic heart valves. However, no correlation with clinical parameters was identified.

Adult↗
PubMed1994

Coagulation activity and emboli counts in patients with prosthetic cardiac valves.

BACKGROUND AND PURPOSE: The underlying embolic material detected by transcranial Doppler ultrasound in patients with prosthetic heart valves remains unknown. We undertook this study to evaluate the relation between the number of Doppler emboli signals and the activity of the coagulation system. METHODS: Patients with various types of prosthetic valves (n = 120) and patients in atrial fibrillation (n = 20) were monitored for 30 minutes using transcranial Doppler with a 2-MHz probe. The plasma concentrations of cross-linked D-dimer, antithrombin-III, and thrombin-antithrombin III complex were measured. RESULTS: No correlation between the levels of any of the hematologic parameters and the number of emboli was demonstrated in the studied groups. The D-dimer levels were significantly higher in patients with mechanical prosthetic valves with an international normalized ratio under 2.0 compared with those with an international normalized ratio between 2 and 3.5 or above 3.5, and in patients with Medtronic-Hall versus Björk-Shiley or Carpentier-Edwards valve prostheses. CONCLUSIONS: The lack of correlation between the activity of the coagulation system and the number of Doppler emboli in patients with prosthetic valves suggests that the underlying embolic material in these patients is not thrombotic. Our results also suggest that an increase of the anticoagulation intensity to an international normalized ratio above 3.5 does not result in a further decrease of the activity of the unstimulated coagulation system in patients with mechanical prosthetic valves.

Adult↗
PubMed1994

Interconversion of stroke scales. Implications for therapeutic trials.

BACKGROUND AND PURPOSE: Stroke scales are intended to measure stroke severity for the purpose of clinical trials. Scores have been used to determine trial entry, to compare patient groups within or between trials, or as a secondary end point. The use of scores as an end point in meta-analysis has not been validated, but such analyses have nevertheless been performed when equivocal results have been obtained using the main outcome measure. The different scale designs suggest that conversion of scores may not be possible. We sought to determine whether scores on different scales could be interconverted. METHODS: A single observer scored 433 consecutive admissions to an acute stroke unit on the Canadian Neurological Scale, the middle cerebral artery Neurological Score (or Orgogozo scale), and the National Institutes of Health stroke scale. Data were separated into training and test sets, and linear regression was used to model conversion between scales. Prediction errors were calculated. Strokes were subdivided according to the Oxfordshire Community Stroke Project classification, and coefficients of determination were calculated for different subtypes. RESULTS: Conversion between Canadian and middle cerebral artery Neurological scales was satisfactory (R2 = 94.7%), and prediction errors were acceptable (absolute prediction error, 5.0 +/- 5). Conversion from the National Institutes of Health scale was worse (R2 = 87.5% to Canadian and 89.0% to Neurological Score), and prediction errors were significantly greater (Neurological Score error, 8.7 +/- 7; Canadian Neurological Scale error, 8.5 +/- 7.3; P < .005 for both). Coefficients of determination for interconversion were significantly worse for dysphasic patients with total anterior circulation strokes than for other stroke types (P < .01). Reweighting the motor component of the National Institutes of Health scale improved coefficients of determination and reduced prediction errors, but prediction error for conversion to the Canadian scale remained significantly greater than other conversions (P = .001). CONCLUSIONS: The Canadian Neurological Scale and the middle cerebral artery Neurological Score may reliably be converted. The National Institutes of Health scale cannot be used to predict these scores reliably, even with reweighting of the motor score. Interconversion is poorest for patients with dysphasia and total anterior circulation strokes. These results suggest that there will be more general difficulty in interconverting scales that use different test items and weighting. Meta-analysis using sequential changes in averaged scores from various stroke scales is not valid.

Adult↗