Biomedical subjects

Thompson G Robinson

Publications and source records attributed to Thompson G Robinson.

10 recordsLinked to original sources

PubMed2006

Pressor therapy in acute ischemic stroke: systematic review.

BACKGROUND AND PURPOSE: Systolic blood pressure (SBP) levels below 140 mm Hg after acute stroke occur in 18% to 25% of patients, and may be associated with adverse outcome, in terms of death and disability. It has thus been proposed that BP elevation in acute ischemic stroke may be beneficial by increasing perfusion to the peri-infarct penumbra, though not only in those with low BP levels. METHODS: All articles studying BP elevation in the context of acute stroke were identified using a structured search strategy. RESULTS: Two reviewers independently searched the databases, and 12 relevant publications were identified. All identified publications related to acute ischemic stroke and no articles on pressor therapy in primary hemorrhagic stroke were found. The review included 319 subjects (age: 42 to 88 years, 46% male), with phenylephrine being the most commonly used pressor agent, though 8 studies incorporated volume expansion. Because of small numbers, and varying entry/outcome criteria, no meta-analysis of outcome measures was possible. Overall, in these few studies undertaken, pressor therapy in acute stroke appears feasible and well-tolerated. The benefit and risks in terms of clinical outcomes remains unknown, but intensive monitoring is advised if such therapy is undertaken. CONCLUSIONS: Theoretical arguments exist for inducing BP elevation in acute ischemic stroke to increase blood flow to the ischemic penumbra across patients with a broad BP range. To date, there have only been a few small trials with inconclusive results. Many questions are still unanswered about the safety and potential benefits of pressor therapy in acute stroke. Hopefully, ongoing trials will answer some of these important questions.

Blood Pressure↗

PubMed2006

Reduced glomerular filtration rate in pre-dialysis non-diabetic chronic kidney disease patients is associated with impaired baroreceptor sensitivity and reduced vascular compliance.

Small uncontrolled studies of dialysis-dependent CKD (chronic kidney disease) patients have demonstrated abnormalities of cardiovascular autonomic control and vascular compliance, which may contribute to adverse cardiovascular morbidity in this population. However, there is little information utilizing newer non-invasive techniques in pre-dialysis patients with increasing degrees of uraemia. In the present study, 55 non-dialysis-dependent non-diabetic CKD patients with mean GFR (glomerular filtration rate) of 27 ml x min(-1) x m(-2) were studied. All patients underwent a 10-min period of electrocardiographic and non-invasive blood pressure monitoring. Cardiac BRS (baroreceptor sensitivity) was calculated from the combined alpha-index. PWV (pulse wave velocity) measurement and determination of arterial wave reflexion by applanation tonometry was performed in all patients. Mean (S.D.) cardiac BRS was 10.8 (7.1) ms/mmHg and mean (S.D.) PWV was 8.6 (1.7) m/s. Reduced GFR was correlated with increased PWV and decreased cardiac BRS. On logistic regression analysis with adjustment for clinical significant risk factors, severely impaired renal function (assessed by GFR < 15 ml x min(-1) x m(-2)) was associated with increased large artery stiffness [odds ratio for PWV = 3.14 (95% confidence intervals, 1.03-9.53); P = 0.04] and increased cardiovascular autonomic dysfunction [odds ratio for BRS = 0.87 (95% confidence intervals, 0.75-1.80); P = 0.06]. In conclusion, non-dialysis dependent non-diabetic CKD patients with decreasing GFR have reduced cardiac BRS and increased large artery stiffness. This may have important prognostic and therapeutic consequences for the management of vascular disease in a pre-dialysis population.

Adult↗

PubMed2005

Bendrofluazide fails to reduce elevated blood pressure levels in the immediate post-stroke period.

INTRODUCTION: Blood pressure (BP) levels, beat-to-beat blood pressure variability, dynamic cerebral autoregulation and cardiac baroreceptor sensitivity are frequently abnormal following acute stroke and are associated with an adverse short- and long-term prognosis. Thiazide diuretics are effective antihypertensive agents in preventing primary and secondary stroke, but their hypotensive and cerebral autoregulatory effects in the immediate post-stroke period have not been studied. METHODS: Thirty-seven hypertensive neuroradiologically proven ischaemic stroke patients were randomized in a double-blind, placebo controlled, parallel group study to bendrofluazide 2.5 mg daily or matching placebo, within 96 h of stroke onset, for a 7-day period. Casual and non-invasive beat-to-beat arterial BP levels, cerebral blood flow velocity, ECG and transcutaneous carbon dioxide levels were measured within 70 +/- 20 h of cerebral infarction and again 7 days later. Dynamic cerebral autoregulatory indices, pulse interval, BP variability and cardiac baroreceptor sensitivity were also calculated. RESULTS: Small, non-significant falls were seen in casual and beat-to-beat BP levels over the 7-day period in both active and placebo-treated patients with no differences between treatments. No significant changes were seen in dynamic cerebral autoregulation or in cardiac baroreceptor sensitivity during the follow-up in either group. CONCLUSION: Following acute ischaemic stroke, the standard dose of bendrofluazide at 2.5 mg daily in this study sample did not lower systemic BP levels over the subsequent 7-day period. There was no evidence that bendrofluazide significantly altered cerebral autoregulation or improved cardiac baroreceptor sensitivity post-ictus. Bendrofluazide appears to be an ineffective hypotensive agent at the standard dosage in the initial post-stroke period.

Aged↗

PubMed2005

Abnormalities in cardiac baroreceptor sensitivity in acute ischaemic stroke patients are related to aortic stiffness.

Cardiac BRS (baroreceptor reflex sensitivity) is impaired following ischaemic stroke and predicts the risk of subsequent long-term death and disability. Impaired cardiac BRS may be due to impaired central processing of baroreceptor information following stroke or reduced baroreceptor activity due to increased large artery stiffness. We evaluated the relationship between large (aortic) artery stiffness and cardiac BRS during the acute phase of ischaemic stroke and in comparison with a group of stroke-free control subjects. Thirty-one ischaemic stroke patients were studied within 48 h of onset and again on day 14, along with 26 control subjects free of cerebrovascular disease. Cardiac BRS (determined by spectral analyses) and arterial stiffness estimated by PWVcf (carotid-femoral pulse wave velocity) using applanation tonometry were obtained. At baseline, cardiac BRS was lower in the stroke compared with the control group (4.3+/-2.3 compared with 6.5+/-4.2 ms/mmHg; P < 0.05). Cardiac BRS values were correlated with PWVcf at < 48 h (r = -0.51, P < 0.01) and on day 14 (r = -0.54, P < 0.01), but not in the control group (r = -0.27, P = not significant). In quantile regression models, taking into account the effect of all cardiovascular variables, cardiac BRS was independently related to PWVcf at baseline and on day 14 in the stroke patients, but stroke was not related to cardiac BRS level when other cardiovascular variables were considered. Wall stiffness of the arterial vessels involved in the baroreflex arc may account for, at least in part, the reduced cardiac BRS observed in acute stroke patients.

Acute Disease↗

PubMed2005

Cardiac baroreceptor sensitivity: a prognostic marker in predialysis chronic kidney disease patients?

BACKGROUND: Small, uncontrolled studies of dialysis-dependent chronic kidney disease (CKD) patients have demonstrated abnormalities of cardiovascular autonomic control and vascular compliance, which may contribute to adverse cardiovascular morbidity in this population. However, there is little information utilizing newer, noninvasive techniques in predialysis patients with increasing degrees of uremia. METHODS: One hundred and five nondialysis CKD patients with a median GFR of 23 mL/min/1.73 m(2) (range: 6 to 102) at baseline were studied. Cardiac baroreceptor sensitivity (BRS) was recorded by time- and frequency-domain techniques, and its relationship with increasing degrees of uremia studied. During a mean follow-up period of 42 months (range: 3 to 70), primary (death, dialysis, transplantation) and secondary (fatal and nonfatal cardiovascular events) outcome measures were recorded. The importance of cardiac BRS in comparison to other important renal and cardiovascular prognostic variables in predicting outcome was assessed. RESULTS: Median cardiac BRS by time domain analysis at baseline was 8.85 msec/mm Hg (interquartile range: 6.85), and impaired cardiac BRS was related to reduced GFR, increasing age, and hypertension on quantile regression analysis. 'Impaired' cardiac BRS was associated with a trend toward increased likelihood of both primary and secondary outcomes, and may act as a surrogate measure of other cardiovascular risk factors, including age, hyperlipidemia, hypertension, previous cardiovascular disease, and doubling of creatinine. CONCLUSION: Nondialysis-dependent CKD patients have impaired cardiac BRS, and this was related to decreasing GFR. There was a trend toward poorer prognosis in patients with impaired cardiac BRS that requires further study. Cardiac BRS may provide a simple, bedside, noninvasive assessment of overall cardiovascular risk in this population.

Adult↗

PubMed2005

Acute stroke hypertension: current and future management.

The management of hypertension in acute stroke remains a hotly debated issue. Clinical practice varies widely between physicians, and both European and US guidelines reflect the uncertainty surrounding this question. Although there is a large amount of data that, on the whole, tends to support a connection between poststroke hypertension and hypotension and worse outcome, there have been few randomized controlled trials to clarify whether pharmacologic intervention is safe or beneficial. Data from secondary prevention trials convincingly demonstrate the benefits of controlling hypertension after a stroke but do not guide us as to how early to implement therapy. There is even less information from trials regarding the use of pressor agents in hypotensive stroke patients. This review discusses the dilemmas in the management of acute stroke hypertension and summarizes the available evidence from studies involving a variety of both depressor and pressor agents. The authors detail the ongoing studies that will help to answer some of the outstanding questions and summarizes the existing guidelines regarding indications for acute stroke blood pressure manipulation currently available to physicians.

Acute Disease↗

PubMed2004

Blood pressure in acute stroke.

Elevated systolic blood pressure levels (> or =160 mmHg) are a common complication of acute stroke, affecting up to 60% of patients, and providing an immediate management dilemma in the 40% of acute stroke patients on pre-existing antihypertensive therapy. There are theoretical reasons for both lowering blood pressure in the acute stroke situation, as well as leaving raised levels untreated. Furthermore, low systolic blood pressure levels (< or =140 mmHg), though a less common problem affecting approximately 20% of patients, may also be associated with increased morbidity and mortality. However, limited data exists from randomised, placebo-controlled trials to inform as to the optimum management of acute stroke blood pressure. This review will consider the evidence for and against the therapeutic manipulation of acute stroke blood pressure, and discuss the information currently available from observational and therapeutic intervention trials, as well as consider the ongoing clinical trials in this area.

Acute Disease↗

PubMed2004

The systemic haemodynamic and cerebral autoregulatory effects of bendrofluazide in the subacute post-stroke period.

INTRODUCTION: Little data exist on the efficacy in terms of blood pressure reduction or outcome measures for the various antihypertensive agents in patients post-stroke. In this study the effects of bendrofluazide on blood pressure levels and variability, dynamic cerebral autoregulation and cardiac baroreceptor sensitivity were assessed in the sub-acute stroke period. METHODS: A total of 36 hypertensive ischaemic stroke patients were randomized to oral bendrofluazide 2.5 mg daily or matching placebo starting 10 days post-ictus and continued for 28 days. A total of 12 hypertensive controls were similarly randomized in a double-blind, crossover study, each limb being of 28 days duration. Cerebral blood flow velocity, non-invasive beat-to-beat blood pressure levels, electrocardiograms (ECGs) and transcutaneous carbon dioxide levels were measured before and at the end of each treatment period in stroke and control subjects. RESULTS: Casual blood pressure levels were not significantly reduced in stroke patients with bendrofluazide, but in the placebo group levels increased by 13 +/- 13/6 +/- 7 mmHg (P < 0.001) at study termination. In the control group, casual systolic blood pressure fell during active treatment by 12 +/- 16 mmHg (P < 0.03) compared with placebo. Dynamic cerebral autoregulation, beat-to-beat blood pressure variability and cardiac baroreceptor sensitivity did not change with bendrofluazide or placebo in either the stroke patients or controls. CONCLUSION: Bendrofluazide does not appear to be an effective hypotensive agent in the sub-acute post-stroke period but may limit the blood pressure rise seen during stroke recovery. Bendrofluazide however does not adversely influence dynamic cerebral autoregulation, blood pressure variability or cardiac baroreceptor sensitivity in either strokes or control subjects.

Adult↗

PubMed2003

Cardiac baroreceptor sensitivity predicts long-term outcome after acute ischemic stroke.

BACKGROUND AND PURPOSE: The baroreceptor reflex arc is important in the short-term regulation of the cardiovascular system, and small studies have reported impaired cardiac baroreceptor sensitivity (BRS) after acute stroke. However, the prognostic significance of impaired BRS is uncertain. METHODS: One hundred twenty-four patients underwent simultaneous ECG and noninvasive beat-to-beat blood pressure (BP) monitoring within 72 hours of neuroradiologically confirmed acute ischemic stroke. Cardiac BRS was assessed from the combined alpha-index by means of power spectral analysis techniques. Baseline data for acute stroke patients were compared with those of a control group matched for age, sex, and casual BP. Patients were followed up for a median of 1508 days (range, 9 to 2656 days), and outcome was compared between patients with and without impaired BRS. RESULTS: Median BRS values were significantly lower in stroke patients than in controls (5 [interquartile range, 3.5 to 7.4] versus 6.2 [interquartile range, 4.5 to 8.3] ms/mm Hg; P=0.04). Sixty-one (33 male) patients (mean age, 70.2 [SD 10.5] years) had impaired BRS (< or =5.0 ms/mm Hg) compared with 63 (35 male) patients (mean age, 70.6 [SD 11.7] years) without impaired BRS (>5.0 ms/mm Hg). Stroke patients with impaired BRS values had a significantly poorer prognosis (28% versus 8% mortality rate during the follow-up period) although there were no differences in age, stroke severity, stroke type, or casual or 24-hour BP parameters between the 2 groups. CONCLUSIONS: Impaired cardiac BRS is associated with increased long-term mortality after acute ischemic stroke, irrespective of age, sex, stroke type, and BP. This may reflect cardiac arrhythmias, but the mechanisms underlying this association are unknown, although therapies that improve cardiac BRS after stroke warrant further investigation.

Acute Disease↗

PubMed2002

Cardiovascular autonomic dysfunction in uremia.

Cardiovascular morbidity and mortality is common in chronic renal failure patients, and may be explained in part by abnormalities in cardiovascular autonomic regulation. This review discusses the results of cardiovascular autonomic function studies in chronic renal failure patients. While covering most methods of assessing autonomic function, we focus particularly on power spectral analysis methods. These newer techniques are non-invasive, reproducible, and allow the rapid assessment of the integrity of cardiovascular autonomic reflexes at the bedside. The abnormalities of parasympathetic, sympathetic and cardiac baroreceptor function seen in dialysis-dependent patients are highlighted, and their significance in intra-dialytic hypotension and cardiovascular mortality as well as the effects of dialysis and transplantation on these parameters examined. Importantly, studies of cardiovascular autonomic dysfunction in pre-dialysis chronic renal failure patients, when abnormalities may be amenable to intervention to prevent progression and premature cardiovascular morbidity and mortality, are reviewed.

Autonomic Nervous System Diseases↗