Continuous pulse oximetry in acute hemiparetic stroke

Serum detection of blood brain barrier injury in subjects with a history of stroke and transient ischemic attack

Objective

Stroke and transient ischemic attack may have long-term negative effects on the blood-brain barrier (BBB) and promote endothelial inflammation, both of which could increase neurodegeneration and dementia risk beyond the cell death associated with the index event.

Methods

Serum from 88 postmortem subjects in the Arizona Study of Aging and Neurodegenerative Disorders were analyzed by sandwich ELISA for specific biomarkers to investigate the effects of cerebrovascular accidents (CVAs) on BBB integrity and endothelial activation. Statistical analyses were performed using the Mann-Whitney U Test, Spearman rank correlation, and linear/logistic regressions adjusted for potential confounders; a P-value < .05 was considered significant for all analyses.

Results

Serum PDGFRẞ, a putative biomarker of BBB injury, was significantly increased in subjects with vs without a history of CVA who had similar cardiovascular risk factors (P < .01). This difference was stable after adjusting for age, hypertension, and other potential confounders in regression analysis (odds ratio, 27.02; 95% confidence interval, 2.61-411.7; P < .01). In addition, PDGFRẞ was positively associated with VCAM-1, a biomarker of endothelial inflammation (ρ = 0.42; P < .01).

Conclusions

Our data suggest that patients with stroke or transient ischemic attack have lasting changes in the BBB. Still more, this demonstrates the utility of PDGFRẞ as a serum-based biomarker of BBB physiology, a potentially powerful tool in studying the role of the BBB in various neurodegenerative diseases and COVID infection sequelae.

Clinical Relevance

Our data demonstrate the utility of serum PDGFRẞ, a putative biomarker of BBB integrity in the setting of stroke and TIA (CVA). A serum biomarker of BBB integrity could be a useful tool to detect early BBB damage and allow prospective work to study how such damage affects long-term neurodegenerative risk. Since BBB disruption occurs early in ADRD development, it could be monitored to help better understand disease progression and involvement of vascular pathways in ADRD.

An Investigation of Pulse Oximetry Levels during Swallowing in Healthy Adults and in Individuals with Severe and Very Severe Chronic Obstructive Pulmonary Disease

To compare pulse oximetry (PO) levels during swallowing in healthy adults and adults with severe chronic obstructive pulmonary disease (COPD). Participants included two groups of 60 healthy adults, balanced for gender. The young group ranged from 18 to 38 years, and the older group from 60 to 87 years. In addition, there were 11 participants with COPD aged 43 to 82 years. PO levels were collected as each participant swallowed 10 mL of water, 10 mL of applesauce, and a piece of diced pear (three trials each). Analyses for the healthy groups revealed neither statistically significant main effects for bolus type nor interactions between gender and age. For between-subject effects, there was no main effect for gender, but there was a large main effect for age, and a gender and age interaction. In the group with COPD, there were no significant differences across bolus types; however, PO measures were consistently lower than the healthy groups for all bolus types. Healthy adults exhibited stable PO levels across bolus types. Adults with COPD, although exhibiting significantly lower PO levels, also remained stable. For clinicians who monitor PO measures, these results offer a more comprehensive understanding of the nature of these measures during swallowing in these groups.

Stroke and breathing

Stroke remains a leading cause of neurologic disability with wide ranging effects, including a variety of respiratory abnormalities. Stroke may influence the central control of the respiratory drive and breathing pattern, airway protection and maintenance, and the respiratory mechanics of inspiration and expiration. In the acute phase of stroke, the central control of breathing is affected by changes in consciousness, cerebral edema, and direct damage to brainstem respiratory centers, resulting in abnormalities in respiratory pattern and loss of airway protection. Common acute complications related to respiratory dysfunction include dysphagia, aspiration, and pneumonia. Respiratory control centers are located in the brainstem, and brainstem stroke causes specific patterns of respiratory dysfunction. Depending on the exact location and extent of stroke, respiratory failure may occur. While major respiratory abnormalities often improve over time, sleep-disordered breathing remains common in the subacute and chronic phases and worsens outcomes. Respiratory mechanics are impaired in hemiplegic or hemiparetic stroke, contributing to worse cardiopulmonary health in stroke survivors. Interventions to address the respiratory complications are under researched, and further investigation in this area is critical to improving outcomes among stroke survivors.

Hypoxia after stroke: a review of experimental and clinical evidence

Background

Hypoxia is a common occurrence following stroke and associated with poor clinical and functional outcomes. Normal oxygen physiology is a finely controlled mechanism from the oxygenation of haemoglobin in the pulmonary capillaries to its dissociation and delivery in the tissues. In no organ is this process more important than the brain, which has a number of vascular adaptions to be able to cope with a certain threshold of hypoxia, beyond which further disruption of oxygen delivery potentially leads to devastating consequences. Hypoxia following stroke is common and is often attributed to pneumonia, aspiration and respiratory muscle dysfunction, with sleep apnoea syndromes, pulmonary embolism and cardiac failure being less common but important treatable causes. As well as treating the underlying cause, oxygen therapy is a vital element to correcting hypoxia, but excessive use can itself cause molecular and clinical harm. As cerebral vascular occlusion completely obliterates oxygen delivery to its target tissue, the use of supplemental oxygen, even when not hypoxic, would seem a reasonable solution to try and correct this deficit, but to date randomised clinical trials have not shown benefit.

Conclusion

Whilst evidence for the use of supplemental oxygen therapy is currently lacking, it is vital to rapidly identify and treat all causes of hypoxia in the acute stroke patient, as a failure to will lead to poorer clinical outcomes. The full results of a large randomised trial looking at the use of supplemental oxygen therapy are currently pending.

The effects of position on oxygen saturation in acute stroke: a systematic review

Objective: To investigate the effect of body position on oxygen saturation in the acute stages post stroke.

Design: Systematic review.

Methods: Databases: PREMEDLINE and MEDLINE, Psychinfo, EMBASE, CINAHL, PEDro, all EBM Reviews and Scottish Intercollegiate Guidelines Network (SIGN). Keywords: combinations of cerebrovascular accident/stroke/hemiplegia/ cerbrovascular disorders and position or posture or sitting or standing/lying/supine/ side lying, with oxygen saturation/oxygen levels/blood gas analysis/hypoxia/sleep apnea syndrome/obstructive sleep disorder/Cheyne Stokes breathing. Limits: English language, human, adults and clinical trials. The quality of relevant papers was independently reviewed using criteria based on the SIGN guidelines for randomized controlled trials and methods described by Rywdik et al.

Results: There were four relevant studies involving 183 patients: three high quality and one poor quality. Heterogeneity in the testing positions, selection criteria, outcome measures and analysis methods prevented meta-analysis. There was strong evidence that body position did not affect oxygen saturation in acute stroke patients without relevant (respiratory) co-morbidities. There was limited evidence that sitting in a chair had a beneficial effect and lying positions had a deleterious effect on oxygen saturation in acute stroke patients with respiratory co-morbidities.

Conclusions: Acute stroke patients without respiratory co-morbidities can adopt any body position, people with respiratory co-morbidities should be positioned as upright as possible.

Acute Stroke: Current Evidence-based Recommendations for Prehospital Care

Introduction

In the United States, emergency medical services (EMS) protocols vary widely across jurisdictions. We sought to develop evidence-based recommendations for the prehospital evaluation and treatment of a patient with a suspected stroke and to compare these recommendations against the current protocols used by the 33 EMS agencies in the state of California.

Methods

We performed a literature review of the current evidence in the prehospital treatment of a patient with a suspected stroke and augmented this review with guidelines from various national and international societies to create our evidence-based recommendations. We then compared the stroke protocols of each of the 33 EMS agencies for consistency with these recommendations. The specific protocol components that we analyzed were the use of a stroke scale, blood glucose evaluation, use of supplemental oxygen, patient positioning, 12-lead electrocardiogram (ECG) and cardiac monitoring, fluid assessment and intravenous access, and stroke regionalization.

Results

Protocols across EMS agencies in California varied widely. Most used some sort of stroke scale with the majority using the Cincinnati Prehospital Stroke Scale (CPSS). All recommended the evaluation of blood glucose with the level for action ranging from 60 to 80mg/dL. Cardiac monitoring was recommended in 58% and 33% recommended an ECG. More than half required the direct transport to a primary stroke center and 88% recommended hospital notification.

Conclusion

Protocols for a patient with a suspected stroke vary widely across the state of California. The evidence-based recommendations that we present for the prehospital diagnosis and treatment of this condition may be useful for EMS medical directors tasked with creating and revising these protocols.

Adjustment of oxygen use by means of pulse oximetry: an important tool for patient safety

OBJECTIVE

To assess patient's level of oxygenation by means of pulse oximetry, avoiding hypoxia (that causes rapid and severe damage), hyperoxia, and waste.

METHODS

Calculations were made with a 7% margin of error and a 95% confidence interval. Physical therapists were instructed to check pulse oximetry of all patients with prescriptions for physical therapy, observing the scheduled number of procedures.

RESULTS

A total of 129 patients were evaluated. Hyperoxia predominated in the sectors in which the patient was constantly monitored and hypoxia in the sectors in which monitoring was not continuous.

CONCLUSIONS

Professionals involved in patient care must be made aware of the importance of adjusting oxygen use and the risk that non-adjustment represents in terms of quality of care and patient safety.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care: a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care : a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

The stroke oxygen pilot study: a randomized controlled trial of the effects of routine oxygen supplementation early after acute stroke--effect on key outcomes at six months

INTRODUCTION

Post-stroke hypoxia is common, and may adversely affect outcome. We have recently shown that oxygen supplementation may improve early neurological recovery. Here, we report the six-month outcomes of this pilot study.

METHODS

Patients with a clinical diagnosis of acute stroke were randomized within 24 h of admission to oxygen supplementation at 2 or 3 L/min for 72 h or to control treatment (room air). Outcomes (see below) were assessed by postal questionnaire at 6 months. Analysis was by intention-to-treat, and statistical significance was set at p ≤ 0.05.

RESULTS

Out of 301 patients randomized two refused/withdrew consent and 289 (148 in the oxygen and 141 in the control group) were included in the analysis: males 44%, 51%; mean (SD) age 73 (12), 71 (12); median (IQR) National Institutes of Health Stroke Scale score 6 (3, 10), 5 (3, 10) for the two groups respectively. At six months 22 (15%) patients in the oxygen group and 20 (14%) in the control group had died; mean survival in both groups was 162 days (p = 0.99). Median (IQR) scores for the primary outcome, the modified Rankin Scale, were 3 (1, 5) and 3 (1, 4) for the oxygen and control groups respectively. The covariate-adjusted odds ratio was 1.04 (95% CI 0.67, 1.60), indicating that the odds of a lower (i.e. better) score were non-significantly higher in the oxygen group (p = 0.86). The mean differences in the ability to perform basic (Barthel Index) and extended activities of daily living (NEADL), and quality of life (EuroQol) were also non-significant.

CONCLUSIONS

None of the key outcomes differed at 6 months between the groups. Although not statistically significant and generally of small magnitude, the effects were predominantly in favour of the oxygen group; a larger trial, powered to show differences in longer-term functional outcomes, is now on-going.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN12362720; Eudract.ema.europa.eu 2004-001866-41.

Continuous versus intermittent physiological monitoring for acute stroke

BACKGROUND

Explanations for the effectiveness of stroke units compared with general wards in reducing mortality, institutionalisation and dependence of people with stroke remain undetermined, and the discussion on the most effective stroke unit model is still up for debate. The intensity of non-invasive mechanical monitoring in many western countries is one of the main issues regarding the different models. This is because of its strong impact on the organisation of the stroke unit in terms of the number of personnel, their expertise, the infrastructure and costs.

OBJECTIVES

To assess whether continuous intensive monitoring compared with intermittent monitoring of physiological variables in people with acute stroke can change their prognosis in terms of mortality or disability.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (November 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 8), MEDLINE (1966 to November 2012), EMBASE (1980 to November 2012), CINAHL (1982 to November 2012) and the British Nursing Index (1985 to November 2012). In an effort to identify further published, unpublished and ongoing trials we searched trials registers (November 2012) and reference lists, handsearched conference proceedings and contacted trial authors.

SELECTION CRITERIA

We included all randomised, cluster randomised and quasi-randomised controlled trials comparing continuous monitoring with intermittent monitoring in people within three days of stroke onset. We excluded studies confounded by the delivery of care in different settings (that is studies in which the location of the intervention was not in the same ward in the two arms of the trial).

DATA COLLECTION AND ANALYSIS

Three review authors independently selected studies for inclusion, assessed methodological quality and extracted data. We sought original data from trialists in two trials and verified the inclusion criteria in another four trials (three presented at conferences and one was from the Chinese Clinical Trial Registry). Where possible, we extracted data on the threshold level of abnormality that triggered intervention for a given physiological variable, the specific intervention given to correct the abnormality and compliance with the allocated therapy.

MAIN RESULTS

Three studies, involving a total of 354 participants, met our inclusion criteria for the primary outcome. Compared with intermittent monitoring, continuous monitoring significantly reduced death and disability at three months or discharge (odds ratio (OR) 0.27, 95% confidence interval (CI) 0.13 to 0.56) and was associated with a non-significant reduction in deaths from any cause at discharge (OR 0.72, 95% CI 0.28 to 1.85). These significant results depend on one study that has a high risk of bias.Continuous monitoring was associated with a non-significant reduction of dependency (OR 0.79, 95% CI 0.30 to 2.06), death from vascular causes (OR 0.48, 95% CI 0.10 to 2.39), neurological complications (OR 0.81, 95% CI 0.46 to 1.43), length of stay (mean difference (MD) -5.24, 95% CI -10.51 to 0.03) and institutionalisation (OR 0.83, 95% CI 0.04 to 15.72) (secondary outcomes). For the last two outcomes we detected consistent heterogeneity across trials.Cardiac complications (OR 8.65, 95% CI 2.52 to 29.66), fever (OR 2.17, 95% CI 1.22 to 3.84) and hypotension (OR 4.32, 95% CI 1.68 to 14.38) were detected significantly more often in participants who received continuous monitoring (surrogate outcomes).We detected no significant increase in adverse events due to immobility (pneumonia, other infections or deep vein thrombosis) in participants who were continuously monitored compared with those allocated to intermittent monitoring.

AUTHORS' CONCLUSIONS

Continuous monitoring of physiological variables for the first two to three days may improve outcomes and prevent complications. Attention to the changes in physiological variables is a key feature of a stroke unit, and can most likely be aided by continuous monitoring without complications related to immobility or to treatments triggered by the relief of abnormal physiological variables. Well-designed, high-quality studies are needed because many questions remain open and deserve further research. These include when to start continuous monitoring, when to interrupt it, which people should be given priority, and which treatments are most appropriate after the identification of abnormalities in physiological variables.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Critical care management of acute ischemic stroke

PURPOSE OF REVIEW

Acute ischemic stroke (AIS) can have profound and devastating effects on the CNS and several other organs. Approximately 15% to 20% of patients with AIS are admitted to an intensive care unit and cared for by a multidisciplinary team. This article discusses the critical care management of patients with AIS.

RECENT FINDINGS

Patients with AIS require attention to airway, pulmonary status, blood pressure, glucose, temperature, cardiac function, and, sometimes, life-threatening cerebral edema.

SUMMARY

The lack of disease-specific data has led to numerous management approaches and limited guidance on choosing among them. Existing guidelines emphasize risk factors, prevention, natural history, and prevention of bleeding but provide little discussion of the complex critical care issues involved in caring for patients with AIS.

Ischemic stroke and neuroprotection

Stroke is a major cause of morbidity and mortality in both developed and developing countries of the world. Greater understanding of the pathophysiology of neuronal damage in ischemic stroke has generated interest in neuroprotection as a management strategy. This paper aims to review the current concept and place of neuroprotection in ischemic stroke. An extensive search of all materials related to the topic was made using library sources including Pubmed and Medline searches. Current research findings were also included. The findings are as presented. Neuroprotection is an increasingly recognized management strategy in ischemic stroke that promises to assist clinicians in reducing stroke mortality rates and improving the quality of life of survivors.

The SOS pilot study: a RCT of routine oxygen supplementation early after acute stroke--effect on recovery of neurological function at one week

Mild hypoxia is common after stroke and associated with poor long-term outcome. Oxygen supplementation could prevent hypoxia and improve recovery. A previous study of routine oxygen supplementation showed no significant benefit at 7 and 12 months. This pilot study reports the effects of routine oxygen supplementation for 72 hours on oxygen saturation and neurological outcomes at 1 week after a stroke.

METHODS

Patients with a clinical diagnosis of acute stroke were recruited within 24 h of hospital admission between October 2004 and April 2008. Participants were randomized to oxygen via nasal cannulae (72 h) or control (room air, oxygen given only if clinically indicated). Clinical outcomes were assessed by research team members at 1 week. Baseline data for oxygen (n = 148) and control (n = 141) did not differ between groups.

RESULTS

The median (interquartile range) National Institutes of Health Stroke Scale (NIHSS) score for the groups at baseline was 6 (7) and 5 (7) respectively. The median Nocturnal Oxygen Saturation during treatment was 1.4% (0.3) higher in the oxygen than in the control group (p<0.001) during the intervention. At 1 week, the median NIHSS score had reduced by 2 (3) in the oxygen and by 1 (2) in the control group. 31% of participants in the oxygen group and 14% in the control group had an improvement of ≥4 NIHSS points at 1 week doubling the odds of improvement in the oxygen group (OR: 2.9).

CONCLUSION

Our data show that routine oxygen supplementation started within 24 hours of hospital admission with acute stroke led to a small, but statistically significant, improvement in neurological recovery at 1 week. However, the difference in NIHSS improvement may be due to baseline imbalance in stroke severity between the two groups and needs to be confirmed in a larger study and linked to longer-term clinical outcome.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN12362720; European Clinical Trials Database 2004-001866-41.

Frequency of nocturnal hypoxia in clinically stable patients during stroke rehabilitation

OBJECTIVE

Sleep disordered breathing is common in patients with cerebrovascular disease. Nocturnal hypoxia may lead to daytime tiredness and cognitive impairment, thus affecting progress. This study assessed the prevalence of nocturnal hypoxia during rehabilitation from stroke.

DESIGN

Prospective observational trial.

SETTING

The stroke rehabilitation wards of the North Staffordshire Hospital, UK and of Kreiskrankenhaus Grevenbroich, Germany.

SUBJECTS

Adult patients on a stroke rehabilitation ward, 10 days to 3 months (mean 32 days, SD18) after stroke onset (n = 160). Age and local environment-matched controls (n = 156) without a history of stroke were recruited from the community at both centres.

MAIN MEASURES

Pulse oximetry was performed overnight on the day of enrolment from 21:00 to 09:00. The baseline awake oxygen saturation, the mean nocturnal oxygen saturation, the lowest nocturnal oxygen saturation and the 4% Oxygen Desaturation Index were calculated for each participant.

RESULTS

The mean baseline awake oxygen saturation of stroke patients was at 95.3% (SD 1.7), 0.5% lower than that of controls (P = 0.005, independent t-test). The group means of the mean nocturnal oxygen saturation for stroke patients were 0.5% lower (at 93.8% SD 2.2) than controls (P = 0.03, independent t-test). The mean lowest nocturnal oxygen saturation was at 79.4% (SD 9.9), 5.9% lower than that of the controls (P<0.001, independent t-test). Considerably more stroke patients (n = 67, 42%) than controls (n = 24, 15%) had > or =10 desaturations below the baseline per hour (P<0.001 chi-square test).

CONCLUSION

Clinically stable stroke patients enrolled in rehabilitation programmes have lower oxygen saturation and more nocturnal desaturations than non-stroke controls.

Hypoxaemia and stroke

The topic of hypoxaemia after stroke was last reviewed in this journal in 2001. Since then a lot of new information on the subject has been published, and while some questions have been resolved, new problems have emerged. This article discusses new research in the light of what is already known and outlines areas of persisting uncertainty.

Early changes in physiological variables after stroke

Several aspects of physiology, notably blood pressure, body temperature, blood glucose, and blood oxygen saturation, may be altered after an ischemic stroke and intracerebral hemorrhage. Generally, blood pressure and temperature rise acutely after a stroke, before returning to normal. Blood glucose and oxygen levels may be abnormal in individuals, but they do not follow a set pattern. Several aspects of these physiological alterations remain unclear, including their principal determinants - whether they genuinely affect prognosis (as opposed to merely representing underlying processes such as inflammation or a stress response), whether these effects are adaptive or maladaptive, whether the effects are specific to certain subgroups (e.g. lacunar stroke) and whether modifying physiology also modifies its prognostic effect. Hypertension and hyperglycemia may be helpful or harmful, depending on the perfusion status after an ischemic stroke; the therapeutic response to their lowering may be correspondingly variable. Hypothermia may provide benefits, in addition to preventing harm through protection from hyperthermia. Hypoxia is harmful, but normobaric hyperoxia is unhelpful or even harmful in normoxic patients. Hyperbaric hyperoxia, however, may be beneficial, though this remains unproven. The above-mentioned uncertainties necessitate generally conservative measures for physiology management, although there are notably specific recommendations for thrombolysis-eligible patients. Stroke unit care is associated with better outcome, possibly through better management of poststroke physiology. Stroke units can also facilitate research to clarify the relationship between physiology and prognosis, and to subsequently clarify management guidelines.

Day-night differences in oxygen saturation and the frequency of desaturations in the first 24 hours in patients with acute stroke

BACKGROUND

Hypoxia is common after acute stroke. Most studies of oxygenation after stroke were done at night. The objective of this study was to determine whether there are differences in oxygenation between day and night early after stroke.

METHODS

Patients with an acute stroke were recruited within 24 hours of admission. Patients who were hypoxic (oxygen saturation < 90%) were excluded. Oxygen saturation was assessed by pulse oximetry over 24 hours. Daytime recordings were taken from 9 am to 9 pm and nighttime recordings from 10 pm to 6 am. Respiratory rate and sleep/awake status were recorded twice during the day and the night.

RESULTS

Forty patients were recruited (mean age 77 years [range 55-93 years], 53% men; median [range] Glasgow Coma Scale score 15 [10-15] and Scandinavian Stroke Scale score 31 [4-56]; 80% cerebral infarcts, 20% hemorrhages). The median (range) respiratory rate was 20 (14-30) breaths/min in the day and 18 (12-32) breaths/min in the night (P < .01, Wilcoxon paired test). The median (range) oxygen saturation was 95.5% (87%-98.6%) in the day and 94.3% (80%-98%) at night (P < .001, Wilcoxon paired test). The median (range) 4% oxygen desaturation index was 1.7 (0.0, 18.0) in the day and 3.0 (0.0, 39.4) at night (P < .001, Wilcoxon paired test). Respiratory rate, oxygen saturation, and 4% oxygen desaturation index during the day and night were strongly correlated.

CONCLUSIONS

All indicators of oxygenation assessed in this study were significantly worse at night than in the day. Because daytime and nighttime results were strongly correlated, borderline hypoxia during the day is strongly predictive of overt hypoxia at night.

Hypoxaemia in Acute Stroke Is Frequent and Worsens Outcome

BACKGROUND

Hypoxaemia in the acute phase of stroke might damage the ischaemic penumbra and worsen clinical outcome. We determined the frequency of hypoxaemia on admission with stroke and assessed whether it was related to outcome.

METHODS

We measured arterial oxygen saturation (SaO2) and breathing effort with portable monitoring equipment in a large cohort of acute stroke patients, continually from arrival at hospital, during interdepartment transfer, in imaging and on the ward. Patients received best medical care according to current guidelines. Baseline neurological examination and 3-month outcome (Modified Rankin Scale) were assessed blind to other data. Hypoxaemia was defined as SaO2 <90% for >or=10% of each assessment stage.

RESULTS

Mean SaO2 was lowest during transfers (p < 0.01), but hypoxaemia was common in all assessment stages. Patients with hypoxaemia (30/153, 20%) were more likely to have a pre-existing respiratory disease on admission than those without hypoxaemia (p < 0.04). More patients with hypoxaemia (40%) died than those without hypoxaemia (20%) (hazard ratio, 2.0; 95% CI, 1.0-4.1), though after adjusting for National Institute of Health Stroke Scale and age this association was not statistically significant (hazard ratio, 1.5; 95% CI, 0.7-3.1). There were similar numbers of dependent survivors in both groups.

CONCLUSION

Hypoxaemia during acute stroke assessment was associated with increased risk of death. Although SaO2 is lower during transfers, hypoxaemia occurs in all stages of the admission process. Further research is necessary to determine whether strategies to avoid hypoxaemia during acute assessment improve stroke survival.

Homeostasis as basis of acute stroke treatment: stroke units are the key

INTRODUCTION

Several studies suggest that the control of blood pressure (BP), blood glucose level, body temperature, and oxygen saturation, when analyzed separately, is related with successful acute stroke outcome. However, in a biological system these parameters are interrelated and could influence the process. Recent studies highlight the importance of the appropriate maintenance of these variables that are involved in homeostasis in patients with stroke and the influence they have on outcome.

METHODS

A review was conducted of published studies which analyzed the influence of control of these physiological variables in acute stroke, whether in isolation or combinations, and we have contributed our own data derived from observational studies.

RESULTS

The maintenance of homeostasis forms the basis of acute stroke treatment, in what is termed nonpharmacological neuroprotection. Stroke units (SU) are the ideal environment for this therapeutic approach since their favorable influence on the correct management of BP, body temperature, oxygen saturation, and blood glucose in the progress of stroke patients have been proved.

CONCLUSIONS

The proper management of physiological variables (homeostasis) such as BP, body temperature, blood glucose, and oxygen saturation is the basis of acute stroke treatment, and SU are the key to this approach.

Transient middle cerebral artery occlusion influence on systemic oxygen homeostasis and erythropoiesis in Wistar rats

BACKGROUND AND PURPOSE

Systemic hypoxia is a common complication in stroke patients and may exacerbate ischemic brain damage. Expression of the hypoxia-inducible cytokine erythropoietin (Epo) is upregulated in the brain in both stroke patients and in animal stroke models and exerts local neuroprotective effects in the ischemic brain. Epo is also well known to stimulate red blood cell (RBC) production. The purpose of the present study was to evaluate whether poststroke systemic hypoxia is present in the rat model and whether it is associated with increased peripheral Epo and RBC production.

METHODS

Wistar rats underwent 1-hour transient middle cerebral artery occlusion (MCAO) under mechanical ventilation, followed by reperfusion without further ventilation. Groups of MCAO and sham-operated animals were evaluated at extended times after reperfusion for assessment of arterial blood gases, plasma Epo, and complete blood count.

RESULTS

Arterial oxygen saturation was significantly lower in the infarct group between 6 and 24 hours after reperfusion (P=0.0005), and plasma Epo levels were increased 6 hours after reperfusion (P<0.05). RBC counts and hematocrit were transiently increased 2 to 7 days after reperfusion in animals with MCAO compared with sham. Maximal increases were seen at day 7 (22% and 16% increases of RBC count and hematocrit, respectively; P<0.001). In contrast, the white blood cell counts in animals with MCAO decreased by >30% in the same time period.

CONCLUSIONS

Plasma Epo levels, RBC counts, and hematocrit are all increased in response to systemic hypoxia after cerebral ischemia in rats.

Unexpected Nocturnal Hypoxia in Patients With Acute Stroke

Background and Purpose— Patients who have had a stroke are at risk of hypoxia through alterations in the central regulation of respiration, through aspiration, and through respiratory muscle weakness. Sleep-related breathing disorders are common and may lead to episodes of nocturnal hypoxia even when daytime oxygenation is normal. The aim of this study was to assess the prevalence of unexpected nocturnal hypoxia in stroke patients.

Methods— Consecutive adult patients with stroke were recruited within 72 hours of admission to hospital. Patients with indications for oxygen treatment were excluded. Older adults from the local community were recruited as control subjects. Oxygenation was assessed by pulse oximetry (Minolta 3i) for 5 minutes when awake before bedtime and continuously from 11 pm until 7 am .

Results— Of the 238 potentially eligible stroke patients, 120 were excluded because they required oxygen, 118 were recruited, and 100 had adequate pulse oximetry data. The mean±SD age was 74±8 years for stroke patients and 72±8 years for control subjects (n=85). Mean awake oxygen saturation (S o 2 ) was 94.5±1.7% for the stroke group and 95.8±1.7% for the control group ( P <0.001). Mean nocturnal S o 2 was 93.5±1.9% in stroke patients and 94.3±1.9% in control subjects ( P <0.01). Stroke patients had a higher oxygen desaturation index (ODI 4%) (8.9 versus 2.1, P <0.001). In addition, 23% of stroke patients spent >30 minutes with S o 2 <90% during the night.

Conclusions— Oxygen saturation at night is ≈1% lower than when awake. Almost a quarter of stroke patients who are normoxic at screening during the day spend >30 minutes with an oxygen saturation <90%.

Admitting acute ischemic stroke patients to a stroke care monitoring unit versus a conventional stroke unit: a randomized pilot study

BACKGROUND AND PURPOSE

Pathophysiological considerations and observational studies indicate that elevated body temperature, hypoxia, hypotension, and cardiac arrhythmias in the acute phase of ischemic stroke may aggravate brain damage and worsen outcome.

METHODS

Both units were organized with the same standard care and multidisciplinary approach to nursing and rehabilitation. A blinded observer assessed functional outcome at 3 months with the modified Rankin scale (mRS) and Barthel Index (BI). End points were (1) poor outcome, defined as either mRS > or =4 or BI <60 or the need for institutional care and (2) mortality.

RESULTS

Fifty-four patients meeting the inclusion criteria were randomized. The groups were well matched for baseline characteristics, stroke subtype, stroke severity, vascular risk factors, and prognostic factors. Poor outcome was seen in 7 (25.9%) patients in the SCMU group and in 13 (48.1%) in the SU group (P=0.16). Mortality was lower in the SCMU group than in the SU group (1 [3.7%] vs 7 [25.9%]; odds ratio, 0.11 [95% CI, 0.02 to 0.96], P=0.05).

CONCLUSIONS

This pilot study suggests that admission of acute stroke patients to an SCMU may reduce mortality and poor outcome. A larger trial is required to confirm these findings.