Normoglycemia (not hypoglycemia) optimizes outcome from middle cerebral artery occlusion

Low Glycolysis Is Neuroprotective during Anoxic Spreading Depolarization (SD) and Reoxygenation in Locusts

Migratory locusts enter a reversible hypometabolic coma to survive environmental anoxia, wherein the cessation of CNS activity is driven by spreading depolarization (SD). While glycolysis is recognized as a crucial anaerobic energy source contributing to animal anoxia tolerance, its influence on the anoxic SD trajectory and recovery outcomes remains poorly understood. We investigated the effects of varying glycolytic capacity on adult female locust anoxic SD parameters, using glucose or the glycolytic inhibitors 2-deoxy-d-glucose (2DG) or monosodium iodoacetate (MIA). Surprisingly, 2DG treatment shared similarities with glucose yet had opposite effects compared with MIA. Specifically, although SD onset was not affected, both glucose and 2DG expedited the recovery of CNS electrical activity during reoxygenation, whereas MIA delayed it. Additionally, glucose and MIA, but not 2DG, increased tissue damage and neural cell death following anoxia-reoxygenation. Notably, glucose-induced injuries were associated with heightened CO2 output during the early phase of reoxygenation. Conversely, 2DG resulted in a bimodal response, initially dampening CO2 output and gradually increasing it throughout the recovery period. Given the discrepancies between effects of 2DG and MIA, the current results require cautious interpretations. Nonetheless, our findings present evidence that glycolysis is not a critical metabolic component in either anoxic SD onset or recovery and that heightened glycolysis during reoxygenation may exacerbate CNS injuries. Furthermore, we suggest that locust anoxic recovery is not solely dependent on energy availability, and the regulation of metabolic flux during early reoxygenation may constitute a strategy to mitigate damage.

Drug-Induced Hyperglycemia as a Potential Contributor to Translational Failure of Uncompetitive NMDA Receptor Antagonists

Hyperglycemia is a comorbidity in 60–80% of stroke patients; nevertheless, neuroprotective drugs like NMDA receptor (NMDAR) antagonists are typically assessed in normoglycemic animals at the preclinical stage before they are approved to enter clinical trials. Interestingly, as a possible explanation for the translational failure of NMDAR antagonists, it was recently reported that stroke occurring during nighttime causes smaller infarctions in rodents and therefore has a smaller window for neuroprotection. To investigate why stroke occurring during different circadian phases confers a difference in severity, we reanalyzed the published source data and found that some mice that were used in the daytime have higher blood glucose than mice that were used in the nighttime. We then repeated the experiments but found no difference in blood glucose concentration or infarct volume regardless of the circadian phase during which stroke occurs. On the other hand, induction of hyperglycemia by glucose injection reproducibly increased stroke severity. Moreover, although hyperglycemia increases infarction volume, which presumably would provide a larger window for neuroprotection, uncompetitive NMDAR antagonists were unexpectedly found to exacerbate stroke outcome by worsening hyperglycemia. Taken together, our new data and reanalysis of the published source data suggested that blood glucose during stroke, rather than the circadian phase during which stroke occurs, affects the size of the ischemic infarction; moreover, we have revealed drug-induced hyperglycemia as a potential reason for the translational failure of uncompetitive NMDAR antagonists. Future trials for this class of neuroprotective drugs should monitor patients’ blood glucose at enrollment and exclude hyperglycemic patients.

Dose-dependent and long-term cerebroprotective effects of intranasal delivery of progesterone after ischemic stroke in male mice

Intranasal administration is emerging as a very promising route to deliver therapeutics to the brain. We have recently shown that the intranasal delivery of progesterone at 8 mg/kg is neuroprotective after stroke in male mice. To explore the translational potential of intranasal progesterone treatment, we performed a dose-response study and analyzed outcomes at 48 h after middle cerebral artery occlusion (MCAO). The effects on functional outcomes at long-term were examined by using the optimal dose. In the first experiment, male C57BL/6JRj mice were treated with progesterone at 8, 16 or 24 mg/kg, or with placebo at 1, 6 and 24 h post-MCAO. Our results show that the dose of 8 mg/kg was optimal in counteracting the early histopathological impairments as well as in improving functional recovery. Steroid profiling in plasma showed that the dose of 8 mg/kg is the one that leads to sustained high levels of progesterone and its neuroactive metabolites. In the second experiment, the dose of 8 mg/kg was used and analyzes were performed at 2, 7 and 21 days post-MCAO. Progesterone increased survival, glycemia and body weight. Furthermore, progesterone decreased neurological deficits and improved performances of mice on the rotarod and pole as early as 2 days and up to 21 days post-MCAO. These findings show that intranasal administration of progesterone has a significant translational potential as a cerebroprotective treatment after stroke that can be effective to reduce mortality, to limit tissue and cell damage at the acute phase; and to confer a long-term functional recovery.

Association between Clinical and Laboratory Markers and 5-year Mortality among Patients with Stroke

Factors influencing long-term stroke mortality have not been comprehensively investigated. This study aimed to identify the baseline clinical, laboratory, demographic/socioeconomic, and hospital factors influencing 5-year mortality in patients with first stroke. Total 3,956 patients with first-stroke hospitalization from 2004 to 2008 were connected to the longitudinal National Health Insurance Research Database. Post-admission baseline data that significantly increased 5-year mortality were red cell distribution width (RDW) >0.145 (adjusted hazard ratio [aHR] = 1.71), hemoglobin <120 g/L (aHR = 1.25), blood sugar <3.89 mmol/L (70 mg/dL)(aHR = 2.57), serum creatinine >112.27 μmol/L (aHR = 1.76), serum sodium <134 mmol/L (aHR = 1.73), body mass index (BMI) < 18.5 kg/m² (aHR = 1.33), Glasgow Coma Scale <15 (aHR = 1.43), Stroke Severity Index ≥20 (aHR = 3.92), Charlson–Deyo Comorbidity Index ≥3 (aHR = 4.21), no rehabilitation (aHR = 1.86), and age ≥65 years (aHR = 2.25). Hemoglobin, RDW, blood sugar, serum creatinine and sodium, BMI, consciousness, stroke severity, comorbidity, rehabilitation, and age were associated with 5-year mortality in patients with first stroke.

Intravenous Tissue-Type Plasminogen Activator in Acute Ischemic Stroke Patients With History of Stroke Plus Diabetes Mellitus

Background and Purpose- Acute ischemic stroke patients with history of prior ischemic stroke plus concomitant diabetes mellitus (DM) were excluded from the ECASS III trial (European Cooperative Acute Stroke Study) because of safety concerns. However, there are few data on use of intravenous tissue-type plasminogen activator and symptomatic intracerebral hemorrhage or outcomes in this population. Methods- Using data from the Get With The Guidelines-Stroke Registry between February 2009 and September 2017 (n=1619 hospitals), we examined characteristics and outcomes among patients with acute ischemic stroke treated with tissue-type plasminogen activator within the 3- to 4.5-hour window who had a history of stroke plus diabetes mellitus (HxS+DM) (n=2129) versus those without either history (n=16 690). Results- Compared with patients without either history, those with both prior stroke and DM treated with tissue-type plasminogen activator after an acute ischemic stroke had a higher prevalence of cardiovascular risk factors in addition to history of stroke, DM, and more severe stroke (National Institutes of Health Stroke Scale: median, 8 [interquartile range, 5-15] versus 7 [4-13]). The unadjusted rates of symptomatic intracerebral hemorrhage and in-hospital mortality were 4.3% (HxS+DM) versus 3.8% (without either history; P=0.31) and 6.2% versus 5.5% ( P=0.20), respectively. These differences were not statistically significant after risk adjustment (symptomatic intracerebral hemorrhage: adjusted odds ratio, 0.79 [95% CI, 0.51-1.21]; P=0.28; in-hospital mortality: odds ratio, 0.77 [95% CI, 0.52-1.14]; P=0.19). Unadjusted rate of functional independence (modified Rankin Scale score, 0-2) at discharge was lower in those with HxS+DM (30.9% HxS+DM versus 44.8% without either history; P≤0.0001), and this difference persisted after adjusting for baseline clinical factors (adjusted odds ratio, 0.76 [95% CI, 0.59-0.99]; P=0.04). Conclusions- Among patients with acute ischemic stroke treated with intravenous tissue-type plasminogen activator within the 3- to 4.5-hour window, HxS+DM was not associated with statistically significant increased symptomatic intracerebral hemorrhage or mortality risk.

Acute Ischaemic Stroke: Management, Recent Advances and Controversies

Acute ischaemic stroke is a major cause of death and disability. It may become an enormous burden to the patients themselves, their families as well as the health care systems. Patients at risk of airway, breathing and circulatory compromise should receive prompt resuscitation. Vital parameters and neurological status should be closely monitored. Attentions to blood pressure, temperature and sugar profile are important. The significance of early and correct diagnosis and subsequent treatment cannot be over-emphasised. There have been tremendous recent advances in different treatment modalities in acute stroke management. Various recanalisation modalities include intravenous and/or intra-arterial thrombolysis, acute defibrinogenation, anti-platelet treatment and anticoagulation. Carotid endarterectomy and endovascular strategies are recommended in selected patients. Advanced neuro-imaging techniques and neuroprotectants are being evaluated. Multidisciplinary stroke teams have been shown to improve patient survival and functional outcome. Pre-defined algorithms and protocols should be in place to expedite smooth and effective delivery of stroke service. Future directions should be aimed at exploring safer recanalisation modalities and extending the limit of the current 3-hour treatment window for thrombolysis.

Potential link between post-acute ischemic stroke exposure to hypoglycemia and hemorrhagic transformation

Hemorrhagic transformation is a severe complication of acute ischemic stroke owing to its limited treatment options and poor prognosis. In the last decade, the rates of hemorrhagic transformation incidence have been associated with blood glucose levels. In particular, hyperglycemia at the time of admission has been associated with increased rates of hemorrhagic transformation in acute ischemic stroke patients. Recent pilot clinical trials have attempted to use intensive insulin therapy during stroke treatment to reduce the severity of cerebral infarction and possibly alleviate the risk of hemorrhagic transformation. However, the results of these studies have shown no clear clinical benefit. In addition, intensive insulin therapy has increased rates of hypoglycemia which may be associated with larger infarct growth. We hypothesize that hypoglycemia, similarly to hyperglycemia, is a risk factor for worse outcomes in acute ischemic stroke by promoting hemorrhagic transformation. This review serves to call attention to patterns present within intensive insulin therapy trials and shed light into the pathophysiological effects of hypoglycemia. It is critical that efforts be directed toward the prevention of hemorrhagic transformation by optimizing insulin therapy during the treatment of acute ischemic stroke.

Effects of hypoglycemia on myocardial susceptibility to ischemia-reperfusion injury and preconditioning in hearts from rats with and without type 2 diabetes

BACKGROUND

Hypoglycemia is associated with increased mortality rate in patients with diabetes. The underlying mechanisms may involve reduced myocardial tolerance to ischemia and reperfusion (IR) or reduced capacity for ischemic preconditioning (IPC). As IPC is associated with increased myocardial glucose uptake (MGU) during reperfusion, cardioprotection is linked to glucose metabolism possibly by O-linked β-N-acetylglucosamine (O-GlcNAc). We aimed to investigate the impact of hypoglycemia in hearts from animals with diabetes on myocardial IR tolerance, on the efficacy of IPC and whether modulations of MGU and O-GlcNAc levels are involved in the underlying mechanisms.

METHODS

In a Langendorff model using diabetic ZDF (fa/fa) and non-diabetic (fa/+) rats (n = 6-7 in each group) infarct size (IS) was evaluated after 40 min of global ischemia and 120 min reperfusion during hypoglycemia [(glucose) = 3 mmol/l] and normoglycemia [(glucose) = 11 mmol/l]. Myocardial glucose uptake and O-GlcNAc levels were evaluated during reperfusion. IPC was induced by 2 × 5 min of global ischemia prior to index ischemia.

RESULTS

IS increased in hearts from animals with (p < 0.01) and without (p < 0.01) diabetes during hypoglycemia compared to normoglycemia. IPC reduced IS during normoglycemia in both animals with (p < 0.01) and without (p < 0.01) diabetes. During hypoglycemia, however, IPC only reduced IS in hearts from animals with diabetes (p < 0.05). IPC increased MGU during reperfusion and O-GlcNAc levels in animals with diabetes during hypo- (MGU: p < 0.05, O-GlcNAc: p < 0.05) and normoglycemia (MGU: p < 0.01, O-GlcNAc: p < 0.05) and in animals without diabetes only during normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01).

CONCLUSIONS

Hypoglycemia increases myocardial susceptibility to IR injury in hearts from animals with and without diabetes. In contrast to hearts from animals without diabetes, the hearts from animals with diabetes are amenable to cardioprotection during hypoglycemia. In parallel with IPC induced cardioprotection, MGU and O-GlcNAc levels increase suggesting that increased MGU and O-GlcNAc levels are involved in the mechanisms of IPC.

Diabetic aggravation of stroke and animal models

Cerebral ischemia in diabetics results in severe brain damage. Different animal models of cerebral ischemia have been used to study the aggravation of ischemic brain damage in the diabetic condition. Since different disease conditions such as diabetes differently affect outcome following cerebral ischemia, the Stroke Therapy Academic Industry Roundtable (STAIR) guidelines recommends use of diseased animals for evaluating neuroprotective therapies targeted to reduce cerebral ischemic damage. The goal of this review is to discuss the technicalities and pros/cons of various animal models of cerebral ischemia currently being employed to study diabetes-related ischemic brain damage. The rational use of such animal systems in studying the disease condition may better help evaluate novel therapeutic approaches for diabetes related exacerbation of ischemic brain damage.

The correlation between admission blood glucose and intravenous rt-PA-induced arterial recanalization in acute ischemic stroke: a multi-centre TCD study

BACKGROUND

The relationship between hyperglycemia and arterial recanalization following intravenous recombinant tissue-plasminogen activator treatment in acute ischemic stroke is not well understood.

AIM

We aimed to evaluate the effects of hyperglycemia in thrombolysed ischemic stroke patients on recanalization rate and clinical outcome.

METHODS

We studied 348 (231 subjects from the CLOTBUST databank and 117 subjects from the CLOTBUST trial phase II) with documented intracranial artery occlusion treated with intravenous recombinant tissue-plasminogen activator. Serum glucose was determined at baseline before intravenous recombinant tissue-plasminogen activator administration. Hyperglycemia was defined as a glucose level ≥140 mg/dl (7·7 mmol/l). Transcranial Doppler findings were interpreted using the thrombolysis in brain ischemia flow grading system as persistent arterial occlusion, re-occlusion or complete recanalization. Poor clinical outcome was defined by modified Rankin score > 2 at three-months.

RESULTS

At baseline, 138 patients (37·4%) were hyperglycemic and 210 patients (56·9%) normoglycemic. Baseline characteristics based on glucose ≥ 140 (7·7 mmol/l) or less 140: age (70·0 ± 12·4 vs. 67·3 ± 14·1, P = 0·065), baseline National Institutes of Health Stroke Scale (17·0 ± 5·5 vs. 15·8 ± 5·5, P = 0·054), time to recombinant tissue-plasminogen activator (141·4 ± 69·1 vs. 145·3 ± 48·4 mins, P = 0·56), and history of diabetes mellitus [60/138 (43·5%) vs. 22/210 (10·5%), P < 0·001]). Patients with hyperglycemia have a higher rate of persisting occlusion [72/138 (52·2%) vs. 66/210 (31·4%)] and less rate of complete recanalization [34/138 (24·6%) vs. 82/210 (39%), P < 0·001]. Median time to recanalization in patients with severe hyperglycemia (glucose ≥ 200) (11 mmol/l) and glucose <200 was 163 ± 79 and 131 ± 90 mins, respectively (P = 0·045). Sixteen patients (11·6%) in the hyperglycemic group and 12 (5·7%) in the normoglycemic group had symptomatic intracerebral hemorrhage (P = 0·049). Seventy-eight patients (69%) in the hyperglycemia group and 72 patients (41·6%) in the normoglycemic group had poor clinical outcome (three-month modified Rankin score > 2) (P ≤ 0·001). After adjusting for stroke risk factors, patients with hyperglycemia were more likely to have poor clinical outcome (three-month modified Rankin score > 2) (adjusted odds ratio = 2·22, 95% confidence interval: 1·2-4·11, P = 0·011) and low complete recanalization rate (adjusted odds ratio: 0·5, confidence interval: 0·3-0·92, P = 0·025) with trend of increase risk of symptomatic intracerebral hemorrhage (adjusted odds ratio: 2·07, confidence interval:0·8-5·1, P = 0·114). There was no association between baseline glucose as a continuous variable and poor clinical outcome, but there was with the complete recanalization's rate.

CONCLUSION

Hyperglycemia is associated with low rate of complete recanalization and poor clinical outcome in intravenous recombinant tissue-plasminogen activator-treated patients. Further studies are needed to evaluate whether lowering hyperglycemia is beneficial in the management of acute stroke patients.

Hyperglycemia, acute ischemic stroke, and thrombolytic therapy

Ischemic stroke is a leading cause of disability and is considered now the fourth leading cause of death. Many clinical trials have shown that stroke patients with acute elevation in blood glucose at onset of stroke suffer worse functional outcomes, longer in-hospital stay, and higher mortality rates. The only therapeutic hope for these patients is the rapid restoration of blood flow to the ischemic tissue through intravenous administration of the only currently proven effective therapy, tissue plasminogen activator (tPA). However, even this option is associated with the increased risk of intracerebral hemorrhage. Nonetheless, the underlying mechanisms through which hyperglycemia (HG) and tPA worsen the neurovascular injury after stroke are not fully understood. Accordingly, this review summarizes the latest updates and recommendations about the management of HG and coadministration of tPA in a clinical setting while focusing more on the various experimental models studying (1) the effect of HG on stroke outcomes, (2) the potential mechanisms involved in worsening the neurovascular injury, (3) the different therapeutic strategies employed to ameliorate the injury, and finally, (4) the interaction between HG and tPA. Developing therapeutic strategies to reduce the hemorrhage risk with tPA in hyperglycemic setting is of great clinical importance. This can best be achieved by conducting robust preclinical studies evaluating the interaction between tPA and other therapeutics in order to develop potential therapeutic strategies with high translational impact.

The Stroke Hyperglycemia Insulin Network Effort (SHINE) trial protocol: a randomized, blinded, efficacy trial of standard vs. intensive hyperglycemia management in acute stroke

RATIONALE

Patients with acute ischemic stroke and hyperglycemia have worse outcomes than those without hyperglycemia. Intensive glucose control during acute stroke is feasible and can be accomplished safely but has not been fully assessed for efficacy.

AIMS

The Stroke Hyperglycemia Insulin Network Effort trial aims to determine the safety and efficacy of standard vs. intensive glucose control with insulin in hyperglycemic acute ischemic stroke patients.

DESIGN

This is a randomized, blinded, multicenter, phase III trial of approximately 1400 hyperglycemic patients who receive either standard sliding scale subcutaneous insulin (blood glucose range 80-179 mg/dL, 4·44-9·93 mmol/L) or continuous intravenous insulin (target blood glucose 80-130 mg/dL, 4·44-7·21 mmol/L) for up to 72 h, starting within 12 h of stroke symptom onset. The acute treatment phase is single blind (for the patients), but the final outcome assessment is double blind. The study is powered to detect a 7% absolute difference in favorable outcome at 90 days.

STUDY OUTCOMES

The primary outcome is a baseline severity adjusted 90-day modified Rankin Scale score, defined as 0, 0-1, or 0-2, if the baseline National Institutes of Health Stroke Scale score is 3-7, 8-14, or 15-22, respectively. The primary safety outcome is the rate of severe hypoglycemia (<40 mg/dL, <2·22 mmol/L).

DISCUSSION

This trial will provide important novel information about preferred management of acute ischemic stroke patients with hyperglycemia. It will determine the potential benefits and risks of intensive glucose control during acute stroke.

Glucose modulation of spreading depression susceptibility

Spreading depression of Leão is an intense spreading depolarization (SD) wave associated with massive transmembrane ionic, water, and neurotransmitter shifts. Spreading depolarization underlies migraine aura, and occurs in brain injury, making it a potential therapeutic target. While susceptibility to SD can be modulated pharmacologically, much less is known about modulation by systemic physiological factors, such as the glycemic state. In this study, we systematically examined modulation of SD susceptibility by blood glucose in anesthetized rats under full physiological monitoring. Hyperglycemia and hypoglycemia were induced by insulin or dextrose infusion (blood glucose ∼40 and 400 mg/dL, respectively). Spreading depolarizations were evoked by direct cortical electrical stimulation to determine the intensity threshold, or by continuous topical KCl application to determine SD frequency. Hyperglycemia elevated the electrical SD threshold and reduced the frequency of KCl-induced SDs, without significantly affecting other SD properties. In contrast, hypoglycemia significantly prolonged individual and cumulative SD durations, but did not alter the electrical SD threshold, or SD frequency, amplitude or propagation speed. These data show that increased cerebral glucose availability makes the tissue resistant to SD.

Tight glycemic control reduces infection and improves neurological outcome in critically ill neurosurgical and neurological patients

BACKGROUND

Tight glycemic control (TGC) may improve outcomes in hyperglycemic neurosurgical patients. The adoption of TGC has been limited by a lack of adequate data on optimal insulin delivery protocols and serum glucose concentration and by concerns about the risks of hypoglycemia.

OBJECTIVE

This study was designed as a meta-analysis of outcomes to compare intensive insulin therapy and TGC with conventional insulin therapy and conventional glucose control. The secondary objective was to determine retrospectively whether a particular glucose range correlates with better outcomes.

METHODS

Using electronic databases, we retrieved all English language studies published between January 1997 and December 2010 reporting outcomes in neurological and neurosurgical patients as a function of glucose levels and insulin protocols. We conducted a meta-analysis around 4 outcome measures: infection, neurological outcome, hypoglycemia, and mortality. Effect sizes in each study were individually correlated with target intensive insulin therapy glucose levels. Individual studies were assessed for quality by use of the Jadad scale.

RESULTS

Nine studies reporting on 1459 patients met the inclusion criteria. Five were restricted to neurosurgical patients. Four included neurological patients. Compared with conventional glucose control, TGC lowered infection rates (odds ratio, 0.59; 95% confidence interval, 0.47-0.76; P < .001) and yielded better neurological outcomes (odds ratio, 1.72; 95% confidence interval, 1.36-2.16; P < .001). Beneficial effects increased as glucose limits tightened and study quality improved (R > 0.9 for both). TGC resulted in a higher rate of hypoglycemic events (odds ratio, 8.04; 95% confidence interval, 4.85-13.31; P < .001). Mortality was not affected.

CONCLUSION

TGC reduced infection risk and improved neurological outcome despite increased rates of hypoglycemic events. An optimal target for serum glucose concentrations could not be determined.

Intensive Versus Subcutaneous Insulin in Patients With Hyperacute Stroke

Background and Purpose—

Intensive insulin therapy (IIT) has not yet proven its efficacy on stroke prognosis or in the reduction of MRI infarct growth. The INSULINFARCT study aims at determining in patients with hyperacute stroke whether IIT, with a better control of poststroke hyperglycemia, would reduce subsequent MRI infarct growth than usual care with subcutaneous insulin.

Methods—

One hundred eighty patients with MRI-proven ischemic stroke and with National Institutes of Health Stroke Scale from 5 to 25 at admission (<6 hours) were randomized to receive IIT or usual subcutaneous insulin for 24 hours. Admission hyperglycemia was not required for recruitment. Control MRI and 3-month follow-up (with functional outcome and serious adverse events) were planned. The primary objective was to detect a difference in the proportion of patients with mean capillary glucose test <7 mmol/L during 24 hours. The secondary objective was to investigate whether IIT would reduce infarct growth. The analysis was planned in intention-to-treat. Patients with >3 missing capillary glucose test were excluded (n=4).

Results—

The proportion of patients with mean capillary glucose test <7 mmol/L in the first 24 hours was higher in the IIT group (95.4% [83 of 87] versus 67.4% [60 of 89]; P <0.0001). The infarct growth was lower in the subcutaneous insulin group (median, 10.8 cm 3 ; 95% CI, 6.5–22.4 versus 27.9 cm 3 ; 14.6–40.7; 60% of increase; P =0.04). The 3-month functional outcome (45.6% [41 of 90] versus 45.6% [41 of 90]), death (15.6% [14 of 90] versus 10% [9 of 90]), and serious adverse events (38.9% [35 of 90] versus 35.6% [32 of 90]) were similar in the subcutaneous insulin and IIT group.

Conclusion—

The IIT regimen improved glucose control in the first 24 hours of stroke but was associated with larger infarct growths. IIT cannot be recommended in hyperacute ischemic stroke.

Clinical Trial Registration—

URL: http://clinicaltrials.gov . Unique Identifier: NCT00472381.

Hyperglycaemia and infarct size in animal models of middle cerebral artery occlusion: systematic review and meta-analysis

Poststroke hyperglycaemia (PSH) is common, has an unclear pathophysiology, and is associated with poor outcomes. Animal studies report conflicting findings. We systematically reviewed the effects of hyperglycaemia on infarct volume in middle cerebral artery occlusion (MCAO) models, generating weighted mean differences between groups using random effects models summarised as effect size (normalised to control group infarct volume as 100%) and 95% confidence interval. Of 72 relevant papers, 23 reported infarct volume. Studies involved 664 animals and 35 distinct comparisons. Hyperglycaemia was induced by either streptozotocin (STZ, 17 comparisons, n=303) or dextrose (18 comparisons, n=356). Hyperglycaemic animals had infarcts that were 94% larger, but STZ was associated with significantly greater increase in infarct volumes than dextrose infusion (140% larger versus 48% larger). In seven studies, insulin did not significantly reduce infarct size and results were heterogeneous. Although hyperglycaemia exacerbates infarct volume in MCAO models, studies are heterogeneous, and do not address the common clinical problem of PSH because they have used either the STZ model of type I diabetes or extremely high glucose loads. Insulin had a nonsignificant and significantly heterogeneous effect. Further studies with relevant models may inform clinical trial design.

Hyperglycemia in aneurysmal subarachnoid hemorrhage: a potentially modifiable risk factor for poor outcome

Hyperglycemia after aneurysmal subarachnoid hemorrhage (aSAH) occurs frequently and is associated with delayed cerebral ischemia (DCI) and poor clinical outcome. In this review, we highlight the mechanisms that cause hyperglycemia after aSAH, and we discuss how hyperglycemia may contribute to poor clinical outcome in these patients. As hyperglycemia is potentially modifiable with intensive insulin therapy (IIT), we systematically reviewed the literature on IIT in aSAH patients. In these patients, IIT seems to be difficult to achieve in terms of lowering blood glucose levels substantially without an increased risk of (serious) hypoglycemia. Therefore, before initiating a large-scale randomized trial to investigate the clinical benefit of IIT, phase II studies, possibly with the help of cerebral blood glucose monitoring by microdialysis, will first have to improve this therapy in terms of both safety and adequacy.

Hyperglycemia in acute ischemic stroke: pathophysiology and clinical management

Patients with acute ischemic stroke frequently test positive for hyperglycemia, which is associated with a poor clinical outcome. This association between poor glycemic control and an unfavorable prognosis is particularly evident in patients with persistent hyperglycemia, patients without a known history of diabetes mellitus, and patients with cortical infarction. To date, however, only one large clinical trial has specifically investigated the effect of glycemic control on stroke outcome. This trial failed to show a clinical benefit, but had several limitations. Despite a lack of clinical evidence supporting the use of glycemic control in the treatment of patients with stroke, international guidelines recommend treating this subset of critically ill patients for hyperglycemia in the hospital setting. This treatment regime is, however, particularly challenging in patients with stroke, and is associated with an increased risk of the patient developing hypoglycemia. Here we review the available evidence linking hyperglycemia to a poor clinical outcome in patients with ischemic stroke. We highlight the pathophysiological mechanisms that might underlie the deleterious effects of hyperglycemia on acute stroke prognosis and systematically review the literature concerning tight glycemic control after stroke. Finally, we provide directions on the use of insulin treatment strategies to control hyperglycemia in this patient group.

Glucose/insulin infusions in the treatment of subarachnoid haemorrhage: a feasibility study

Hyperglycaemia following subarachnoid haemorrhage (SAH) is well recognized and has been shown to be associated with a worse prognosis. It is currently unclear whether this is a secondary phenomenon reflecting the magnitude of the stress response or whether it contributes directly to the pathophysiological disturbances within the brain. There is significant experimental work on ischaemic stroke to suggest that hyperglycaemia increases infarct volume. The authors propose that controlling blood glucose following SAH is safe and that it might improve outcome. All patients admitted with SAH were treated with insulin to control plasma glucose with a target range of 5.0-7.0 mmol/l. Episodes of hypoglycaemia were recorded. Outcome was assessed at 3 months using the Glasgow Outcome Scale. Fifty-five patients were recruited. 32/3389 (0.94%) of glucose readings fell below 3.5 mmol/l. All were treated with i.v. glucose without evidence of clinical deterioration. Insulin treatment for hyperglycaemia following SAH is feasible and safe. A randomised trial is required to assess any effect on outcome.

Variability in physician care practices for glucose treatment in stroke patients

BACKGROUND

Hyperglycemia is noted in up to 60% of stroke patients. Practice guidelines recommend glucose monitoring following stroke but provide few management recommendations. We examined physician care practices for glucose management in stroke patients.

METHODS

Emergency physicians, family physicians, general internists, intensive care specialists and neurologists in Ontario comprised the study population. A mailed, self-administered survey inquired about glucose management practices. Proportions of responses for survey questions were determined. Chi-square analysis was used for comparing physician groups.

RESULTS

Surveys were mailed to 2,280 physicians; 26.8% returned surveys. There were 278 respondents who reported providing stroke patient care. For physicians treating glucose in stroke patients, 16.6% targeted glucose 4.0-6.0 mmol/l, 52% targeted 6.1-8.0 mmol/l, 13.6% targeted 8.1-12.0 mmol/l, 0.8% targeted 12.1-15.0 mmol/l, and 7.5% were unsure. Comparing specialties, 32% of intensivists, 17.5% of neurologists, 13% of general internists, 14% of emergency physicians, and 0% of family physicians reported targeting 4.0-6.0 mmol/l (p=0.026). Overall, 44% reported aiming for target glucose within 12 hours and 77% within 24 hours from hospital presentation. Intensive care specialists treated glucose most aggressively, including 20% treating, with insulin infusion, patients with no diabetes and initial glucose 6.0-8.0 mmol/l. Emergency physicians were most conservative when treating glucose in stroke patients.

CONCLUSION

There is variability in the aggressiveness of glucose management in stroke patients by different physician specialty groups, reflecting the lack of evidence available to guide hyperglycemia management in this setting. These results highlight an important gap in knowledge and recommendations for stroke patient care that must be addressed to ensure optimal patient outcomes.

Therapeutic hypothermia and controlled normothermia in the intensive care unit: practical considerations, side effects, and cooling methods

BACKGROUND

Hypothermia is being used with increasing frequency to prevent or mitigate various types of neurologic injury. In addition, symptomatic fever control is becoming an increasingly accepted goal of therapy in patients with neurocritical illness. However, effectively controlling fever and inducing hypothermia poses special challenges to the intensive care unit team and others involved in the care of critically ill patients.

OBJECTIVE

To discuss practical aspects and pitfalls of therapeutic temperature management in critically ill patients, and to review the currently available cooling methods.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

Cooling can be divided into three distinct phases: induction, maintenance, and rewarming. Each has its own risks and management problems. A number of cooling devices that have reached the market in recent years enable reliable maintenance and slow and controlled rewarming. In the induction phase, rapid cooling rates can be achieved by combining cold fluid infusion (1500-3000 mL 4 degrees C saline or Ringer's lactate) with an invasive or surface cooling device. Rapid induction decreases the risks and consequences of short-term side effects, such as shivering and metabolic disorders. Cardiovascular effects include bradycardia and a rise in blood pressure. Hypothermia's effect on myocardial contractility is variable (depending on heart rate and filling pressure); in most patients myocardial contractility will increase, although mild diastolic dysfunction can develop in some patients. A risk of clinically significant arrhythmias occurs only if core temperature decreases below 30 degrees C. The most important long-term side effects of hypothermia are infections (usually of the respiratory tract or wounds) and bedsores.

CONCLUSIONS

Temperature management and hypothermia induction are gaining importance in critical care medicine. Intensive care unit physicians, critical care nurses, and others (emergency physicians, neurologists, and cardiologists) should be familiar with the physiologic effects, current indications, techniques, complications and practical issues of temperature management, and induced hypothermia. In experienced hands the technique is safe and highly effective.

Evaluation of short-term consequences of hypoglycemia in an intensive care unit

BACKGROUND

Introduction of strict glycemic control has increased the risk for hypoglycemia in the intensive care unit. Little is known about the consequences of hypoglycemia in this setting. We examined short-term consequences (seizures, coma, and death) of hypoglycemia in the intensive care unit.

PATIENTS AND METHODS

All occurrences of hypoglycemia (glucose of <45 mg/dL) in our intensive care unit between September 1, 2002, and September 1, 2004, were identified. Patients with hypoglycemia (n = 156) were matched for time to hypoglycemia with control patients drawn from the at-risk population (nested case control method). Seizures observed within 8 hrs after hypoglycemia were scored. Discharge summaries for cases and controls were reviewed for occurrence of possible hypoglycemia-associated coma and death. A hazard ratio for in-hospital death was calculated with Cox regression analysis.

RESULTS

The hazard ratio for in-hospital death was 1.03 (95% confidence interval, 0.68-1.56; p = .88) in patients with a first occurrence of hypoglycemia relative to the controls without hypoglycemia, corrected for duration of intensive care unit admittance before hypoglycemia, age, sex, and Acute Physiology and Chronic Health Evaluation II score at admission. No cases of hypoglycemia-associated death were reported. Hypoglycemic coma was reported in two patients. Seizures after hypoglycemia were observed in one patient.

CONCLUSIONS

In this study, no association between incidental hypoglycemia and mortality was found. However, this data set is too small to definitely exclude the possibility that hypoglycemia is associated with intensive care unit mortality. In three patients with possible hypoglycemia-associated coma or seizures, a causal role for hypoglycemia seemed likely but could not fully be established.

[Insulin in the treatment of ischemic stroke]

Hyperglycemia is correlated with poor prognosis in ischemic strokes and also increases the risk of hemorrhagic transformation after thrombolysis. The toxicity of hyperglycemia, already well established in animals, is beginning to be clear for humans. On the other hand, the beneficial effect of insulin remains controversial in animals and has never been demonstrated in humans. Preliminary data, which suggest that the speed and quality of glycemic control may be decisive in the efficacy of treatment, merit testing in a randomized trial.

Therapeutic Time Window and Dose Dependence of Neuroprotective Effects of Sodium Orthovanadate following Transient Middle Cerebral Artery Occlusion in Rats

Vanadium is widely distributed in the environment and exhibits various biological and physiological effects in the human body. We previously documented the neuroprotective effect of sodium orthovanadate (SOV) against in rodents i.v. injected with 2 ml/kg 50 mM SOV just after the induction of middle cerebral artery occlusion (MCAO; 0 min post-MCAO). To evaluate its potential clinical use, we determined here therapeutic time window (0, 45, and 90 min post-MCAO) and the neuroprotective dose (2 ml/kg, 12.5, 25, 37.5, and 50 mM) of SOV in rats. A single injection of 50 mM SOV at 0 or 45 min post-MCAO produced similar neuroprotective effects, and even 50 mM delivered 90 min post-MCAO exerted significant neuroprotection. Although the maximal neuroprotective effect was obtained at 50 mM SOV, 25 mM injected once and 12.5 mM delivered at 0 and 45 min post-MCAO significantly reduced the infarct volume. We also documented that SOV treatment ameliorates ischemic neuronal cell injury via the activation of both protein kinase B (Akt) and extracellular signal-regulated kinase (ERK), inhibits serum glucose, and elicits the gradual recovery of regional cerebral blood flow (rCBF) after transient MCAO in rats. To elucidate the important factor(s) involved in the neuronal protection afforded by SOV, we measured Akt and ERK activity, physiological parameters, blood glucose levels, and rCBF following various SOV treatments. In conclusion, Akt activation was the most important factor in SOV-induced neuroprotection; ERK activation, the gradual recovery of rCBF, and decreased blood glucose were weak contributors.

Elevated total white blood cell count with high blood glucose is associated with poor outcome after ischemic stroke

Increases in total white blood cell (WBC) count and blood glucose level have each been associated with poor outcomes after ischemic stroke. The aim of this study was to determine whether there was an added effect of elevated total WBC count with glucose level on outcome after ischemic stroke. A total of 436 consecutive patients with ischemic stroke who were admitted to Suburban Hospital, Bethesda, MD, between June 2000 and December 2002 were included in this study. Nonfasting peripheral WBC count and glucose level were obtained on hospital arrival, along with self- and family member-reported risk factors for stroke and clinical parameters. WBC count and glucose level were dichotomized into 4 groups: increased WBC count with increased glucose level (IW;IG), increased WBC count with normal glucose level (IW;NG), normal WBC count with increased glucose level (NW;IG), and normal WBC count with normal glucose level (NW;NG). Poor outcome was defined as a modified Rankin scale score >/= 2 at hospital discharge. On univariate analysis, patients with IW;IG (n = 53) had worse outcome (P < .001) than patients with NW;NG (n = 210) or elevations in either factor alone. On multivariate logistic regression analysis, after adjustment for stroke severity and other factors, the odds ratios of poor stroke outcomes were 20 (95% confidence interval [CI] = 3.3-125; P < .001) for the IW:IG group, 3.3 (95% CI = 1.1-14.3; P = .03) for the IW;NG group, and 2.5 (95% CI = 1.1-5.0; P = .03) for the NW;IG group, all compared with the NW:NG group. There may be an added effect of elevated WBC count with hyperglycemia on poor outcome after ischemic stroke. Strict control of inflammatory parameters and glucose may help improve outcome for patients with ischemic stroke.

Impact of Admission Hyperglycemia on Stroke Outcome After Thrombolysis

BACKGROUND AND PURPOSE

We evaluated the impact of admission hyperglycemia (HG) on stroke outcome in relation to the timing of reperfusion in patients treated with tissue plasminogen activator (tPA).

METHODS

We studied 138 consecutive stroke patients with a documented middle cerebral artery (MCA) occlusion treated with intravenous tPA <3 hours of stroke onset. Serum glucose was determined at baseline before tPA administration. HG was defined as a glucose level >140 mg/dL. National Institutes of Health Stroke Scale (NIHSS) scores were obtained at baseline and 24 hour. Transcranial Doppler monitoring of recanalization was conducted during the first 12 hour of stroke onset. mRS was used to assess outcome at 3 months.

RESULTS

Median baseline NIHSS score was 17 points. At baseline, 42 (37.3%) patients were hyperglycemic and 96 (62.7%) normoglycemic. Reperfusion was achieved <3 hours of stroke onset in 32 (23%) patients, between 3 to 6 hours in 49 (36%), 6 to 12 hours in 15 (12%), and in 32 (23%) the MCA remained occluded at 12 hours. A logistic regression model revealed that baseline NIHSS score >16 points (odds ratio [OR], 3.32; 95% CI, 2.18 to 24.7; P=0.032) and admission glucose level >140 mg/dL (OR, 5.65; 95% CI, 1.97 to 16.18; P=0.002) independently predicted poor outcome (modified Rankin scale, 3 to 6) at 3 months. After adjusting by age, stroke severity, site of MCA occlusion, and degree of recanalization, the contribution of HG for poor outcome was higher as shorter the time to reperfusion. The highest odds for poor outcome related to HG corresponded to patients who recanalized <3 hour (OR, 3.1; 95% CI, 1.8 to 14.3; P=0.002), as compared with those who recanalized between 3 and 6 hours (OR, 2.1; 95% CI, 1.1 to 16; P=0.034) and between 6 to 12 hours (OR, 1.1; 95% CI, 0.7 to 21; P=0.43). Moreover, baseline glucose level was negatively correlated (r=-0.45; P=0.001) with the degree of improvement in the NIHSS score at 24 hours after early (<3 hours) but not after delayed (>3 hours) or no recanalization.

CONCLUSIONS

The impact of admission HG on stroke outcome varies depending on the time to tPA-induced reperfusion. The detrimental effect of acute HG is higher after early than after delayed or no reperfusion. Ultra-early glycemic control before reperfusion may improve the efficacy of thrombolytic therapy.

Optimal blood glucose levels while using insulin to minimize the size of infarction in focal cerebral ischemia

Object. Insulin has been shown to ameliorate cerebral necrosis in global and, more recently, in focal cerebral ischemia. The goal of this study was to determine the relationship between this neuroprotective effect and blood sugar levels in a rat model of focal ischemia.

Methods. Thirty-four rats were subjected to 80 minutes of transient middle cerebral artery occlusion at a mean arterial blood pressure of 60 mm Hg and a temperature of 37°C. Insulin (3.5 IU/kg) was administered 1 hour before (12 rats) and 20 minutes after (12 rats) ischemia; 10 animals served as controls. A quantitative histopathological study conducted after 1 week of survival showed that insulin was not beneficial in reducing the size of the infarction or selective neuronal necrosis in the penumbra when administered before or after ischemia. In addition to infarction, six animals from the insulin-treated groups had bilateral selective neuronal necrosis in the hippocampus or the neocortex. A nonlinear regression analysis in which glucose levels were compared with both cortical necrosis and total infarction yielded a U-shaped curve with a nadir for cerebral necrosis that lay in the 6- to 7-mM blood glucose range. The increased brain damage induced by insulin occurred in animals with very low blood sugar values in the range of 2 to 3 mM.

Conclusions. These results in rats indicate that if insulin is used following ischemia, blood glucose levels should be maintained at approximately 6 to 7 mM. From these data one can infer that hypoglycemia of less than 3 mM should be avoided in situations of focal cerebral ischemia in which insulin is used. Additional animal studies and clinical trials in humans are needed to study the effects of insulin on ischemia.

Intensive Insulin Therapy for Critically III Patients

OBJECTIVE:

To evaluate the clinical outcomes of glycemic control of intensive insulin therapy and recommend its place in the management of critically ill patients.

DATA SOURCES:

Searches of MEDLINE (1966—March 2004) and Cochrane Library, as well as an extensive manual review of abstracts were performed using the key search terms hyperglycemia, insulin, intensive care unit, critically ill, outcomes, and guidelines and algorithms.

STUDY SELECTION AND DATA EXTRACTION:

All articles identified from the data sources were evaluated and deemed relevant if they included and assessed clinical outcomes.

DATA SYNTHESIS:

Mortality among patients with prolonged critical illness exceeds 20%, and most deaths are attributable to sepsis and multisystem organ failure. Hyperglycemia is common in critically ill patients, even in those with no history of diabetes mellitus. Maintaining normoglycemia with insulin in critically ill patients has been shown to improve neurologic, cardiovascular, and infectious outcomes. Most importantly, morbidity and mortality are reduced with aggressive insulin therapy. This information can be implemented into protocols to maintain strict control of glucose.

CONCLUSIONS:

Use of insulin protocols in critically ill patients improves blood glucose control and reduces morbidity and mortality in critically ill populations. Glucose levels in critically ill patients should be controlled through implementation of insulin protocols with the goal to achieve normoglycemia, regardless of a history of diabetes. Frequent monitoring is imperative to avoid hypoglycemia.

Neuroprotective effect of postischemic administration of sodium orthovanadate in rats with transient middle cerebral artery occlusion

Orthovanadate is a competitive inhibitor of protein tyrosine phosphatases. Some of its reported biologic effects are its insulin mimetic property and its activation of phosphoinositide 3-kinase and extracellular-signal regulated kinase (ERK). The authors previously reported its neuroprotective effect on delayed neuronal death of gerbil hippocampal CA1 neurons via Akt and ERK activation after transient forebrain ischemia. In the present study, the neuroprotective effect of postischemic intraperitoneal administration of sodium orthovanadate (2 l/kg of 50-mmol/l sodium orthovanadate in saline) was investigated in rats with transient middle cerebral artery occlusion. Ischemic neuronal injury was evaluated 1 day and 28 days after ischemia. The neuroprotective effect of orthovanadate was significant in the cortex but not the caudate putamen (ischemic core) at both 1 and 28 days after ischemia. In orthovanadate group, the activities of Akt and ERK were maintained after reperfusion; they were decreased in saline group. Blood glucose level decreased but within normal range. Regional cerebral blood flow was lower than that of saline group only at 0 hours after reperfusion. These data suggest that orthovanadate has neuroprotective effects in rats with transient middle cerebral artery occlusion and that these effects are mediated by Akt and ERK activation. Furthermore, low blood glucose levels and gradual recovery of regional cerebral blood flow may contribute to neuroprotection.

Effects of admission hyperglycemia on stroke outcome in reperfused tissue plasminogen activator--treated patients

BACKGROUND AND PURPOSE

We sought to investigate the impact of hyperglycemia before reperfusion on long-term outcome in patients treated with intravenous tissue plasminogen activator (tPA).

METHODS

Of 268 consecutive patients with a nonlacunar middle cerebral artery (MCA) stroke evaluated at <3 hours after onset, 73 (27.2%) received intravenous tPA. Serum glucose was determined at baseline before tPA administration. Hyperglycemia was defined as a glucose level >140 mg/dL. National Institutes of Health Stroke Scale (NIHSS) scores were obtained at baseline and 24 hours. Transcranial Doppler monitoring of recanalization and reocclusion was conducted during the first 24 hours. Total infarct volume was measured on CT at day 5 to 7. Modified Rankin Scale was used to assess outcome at 3 months.

RESULTS

Median NIHSS score was 17. At baseline, 31 patients (42.5%) were hyperglycemic and 42 (57.5%) normoglycemic. Early reperfusion (<6 hours) occurred in 43 patients (58.9%). Admission blood glucose correlated negatively with the degree of neurological improvement at 24 hours in reperfused (r=-0.43; P=0.019) but not in nonreperfused (r=-0.20; P=0.21) tPA-treated patients. Increased age (P=0.014), history of diabetes mellitus (P=0.043), admission glucose >140 mg/dL (P=0.002), and early reocclusion (P=0.004) were factors associated with poor outcome among reperfused patients. A logistic regression modeling revealed that only admission glucose value >140 mg/dL (odds ratio, 8.4; 95% CI, 1.76 to 40.02; P=0.005) emerged as an independent predictor of poor outcome despite tPA-induced recanalization. In patients with 6-hour persistent MCA occlusion, baseline NIHSS score >15 points (P=0.011) and proximal MCA occlusion (P=0.039) were variables associated with poor outcome on univariate analysis. In a logistic regression model, only NIHSS score >15 points (odds ratio, 11.9; 95% CI, 1.48 to 97.1; P=0.032) remained as an independent predictor of poor outcome and functional dependence at 3 months in nonreperfused tPA-treated patients.

CONCLUSIONS

Hyperglycemia before reperfusion may in part counterbalance the beneficial effect of early restoration of blood flow, which translates into a worse outcome in hyperglycemic patients despite tPA-induced recanalization.

The influence of diabetes mellitus and hyperglycaemia on stroke incidence and outcome

Diabetes mellitus is a complex metabolic syndrome with significant effects on the systemic and cerebral vasculature. The incidence and severity of ischaemic stroke are increased by the presence of diabetes, and outcome from stroke is poorer. More than one third of patients admitted with acute stroke are hyperglycaemic at presentation. Reasons for the altered prognosis in diabetes associated stroke are multifactorial. A direct influence of hyperglycaemia at the time of ischaemia is likely to be important. The use of novel methods to delineate stroke topography and pathophysiology such as MR spectroscopy, diffusion and perfusion weighted MRI appear helpful in delineating the effects of hyperglycaemia on stroke pathophysiology. Randomised clinical trials to determine optimal management for patients with hyperglycaemia following stroke are ongoing. Such trials will determine if aggressive control of acute hyperglycaemia following stroke has similar benefits to that observed following acute myocardial infarction. Clinicians responsible for stroke patients should be aware of the importance of adequate glycaemic control in both primary and secondary prevention of stroke.

Acute hyperglycemia adversely affects stroke outcome: a magnetic resonance imaging and spectroscopy study

Controversy exists whether acute hyperglycemia is causally associated with worse stroke outcome or simply reflects a more severe stroke. In reversible ischemia models, hyperglycemia is associated with lactic acidosis and conversion of penumbral tissue to infarction. However, the relationship between hyperglycemia, lactic acidosis, and stroke outcome has not been explored in humans. Sixty-three acute stroke patients were prospectively evaluated with serial diffusion-weighted and perfusion-weighted magnetic resonance imaging and acute blood glucose measurements. Patients with hypoperfused at-risk tissue were identified by acute perfusion-diffusion lesion mismatch. As a substudy, acute and subacute magnetic resonance spectroscopy was performed in the 33 most recent patients to assess the relationship between acute blood glucose and lactate production in the ischemic region. In 40 of 63 patients with acute perfusion-diffusion mismatch, acute hyperglycemia was correlated with reduced salvage of mismatch tissue from infarction, greater final infarct size, and worse functional outcome. These correlations were independent of baseline stroke severity, lesion size, and diabetic status. Furthermore, higher acute blood glucose in patients with perfusion-diffusion mismatch was associated with greater acute-subacute lactate production, which, in turn, was independently associated with reduced salvage of mismatch tissue. In contrast, acute blood glucose levels in nonmismatch patients did not independently correlate with outcome measures, nor was there any acute-subacute increase in lactate in this group. Acute hyperglycemia increases brain lactate production and facilitates conversion of hypoperfused at-risk tissue into infarction, which may adversely affect stroke outcome. These findings support the need for randomized controlled trials of aggressive glycemic control in acute stroke.

Effect of posttraumatic hyperglycemia on contusion volume and neutrophil accumulation after moderate fluid-percussion brain injury in rats

The purpose of this study was to evaluate the effects of posttraumatic hyperglycemia on contusion volume and neutrophil accumulation following moderate traumatic brain injury (TBI) in rats. A parasagittal fluid-percussion (F-P) brain injury (1.8-2.1 atm) was induced in male Sprague-Dawley rats. Rats were then randomized into four trauma groups (n = 7/group) by the timing of dextrose injection (2.0 gm/kg/ip), which included (1) early (E) group: 5 min after TBI; (2) delayed (D) group: 4 h after TBI; (3) 24-h group: 24 h after TBI; or (4) control (C) group: no dextrose injection. A sham operated control group also received dextrose to document physiological parameters (n = 4). Rats were perfusion fixed 3 days following TBI, and the brains were processed for routine histopathological and immunocytochemical analysis. Contusion areas and volumes, as well as the frequency of myeloperoxidase immunoreactive polymorphonuclear leukocytes (PMNLs) were determined. Dextrose injections significantly increased blood glucose levels (p < 0.005) in all treated groups. Although acute hyperglycemia following TBI did not significantly affect total contusion volume, contusion area was significantly elevated in the early treatment group. In addition, early posttraumatic hyperglycemia enhanced neutrophil accumulation in the area of the cortical contusion (p < 0.005). In contrast, delayed induced hyperglycemia (i.e., 4 h, 24 h) did not significantly affect histopathological outcome or neutrophil accumulation. Taken together, these findings indicate that acute but not delayed hyperglycemia aggravates histopathological outcome and increased accumulation of PMNLs. Posttraumatic hyperglycemia in the acute phase may worsen traumatic outcome by enhancing secondary injury processes, including inflammation.

The effects of early insulin treatment combined with thrombolysis in rat embolic stroke

The therapeutic effect of insulin alone or insulin combined with 30 min delayed thrombolytic therapy was investigated in rats embolized in the right hemisphere with a fibrin clot made from autologous blood. Animals were killed seven days after embolization and the infarct volumes were measured in % of the affected hemisphere. Mortality was calculated as the number of animals dying spontaneously before the scheduled euthanasia. The median infarct volume in control animals (n = 12) was 24%. Insulin (3 IU kg(-1)) was given subcutaneously 15 min, 3 h, and 24 h after embolization (n = 12) and reduced median infarct volume to 11%. Human recombinant tissue plasminogen activator, 8 mg kg(-1), was infused intravenously during 45 min starting 30 min after embolization (n = 14), and the median infarct volume was 18% in this group. When the two treatments were combined, the median infarct volume was reduced to 11% (n = 14). The infarct volumes in the treatment groups were not significantly different from controls (p = 0.62, Kruskal Wallis test). Mortality rates increased from 0% among controls to 47% (p = 0.01) in the insulin alone and 38% (p = 0.02) in the combination therapy group. In conclusion, insulin treatment aiming at blood glucose levels around 2-4 mmol l(-1) was detrimental to clinical outcome causing significantly increased mortality.

Non-pharmacologic (physiologic) neuroprotection in the treatment of brain ischemia

Clinical trials for ischemic stroke have been characterized by a disappointing series of negative results, using a panoply of pharmacologic agents. This paper emphasizes five physiologic measures that can be taken to mitigate ischemic brain damage. These are (1) hypothermia, (2) insulin, (3) arterial hyperoxemia, (4) blood pressure control and (5) magnesium. Hypothermia is protective in both focal and global ischemia, even postischemically protecting against selective neuronal necrosis and infarction. The total equation for protection includes the (i) postischemic delay, (ii) depth, and (iii) duration of hypothermia. Insulin operates by lowering glucose levels to the normal range in focal ischemia. It is possible that very low glucose levels are detrimental in focal ischemia with paradoxical augmentation of the infarct size, and that spreading depression plays a role in this. Controlled arterial hyperoxemia seems effective experimentally in reducing infarct size, operating mechanistically by either a direct effect of oxygen, or vasoconstriction causing shunting of blood into the infarct, or both. Blood pressure is a critical determinant of infarct size, and raising blood pressure improves collateral blood flow and reduces stroke size. To be used clinically, however, hemorrhage must be ruled out. The most dramatic clinical effects of blood pressure are seen in aneurysm patients with vasospasm, where minor increases in blood pressure reverse temporary hemiparesis by reducing ischemia. Magnesium is likely the safest NMDA antagonist, with a long history of safe administration to pregnant women with eclampsia. There is potential interaction with insulin, in that magnesium causes hyperglycemia, which requires insulin to counteract it. Magnesium and insulin together have been shown effective in experimental brain ischemia. In the absence of safe and effective pharmacologic neuroprotection agents, clinical trials should be designed and launched to test these physiologic measures, singly and in combination, to reduce brain damage after ischemia.

Neurological evaluation and intelligence testing in the child with operated congenital heart disease

BACKGROUND

The immediate and intermediate-term neurodevelopmental outcome in infants undergoing open heart procedures using deep hypothermic cardiopulmonary bypass was assessed prospectively.

METHODS

One hundred consecutive infants (age 2 to 174 days) were operated on using either deep hypothermic bypass only (group A, n = 28), or with associated circulatory arrest (group B, n = 72). Early neurological outcome was recorded. Survivors underwent mental development evaluation after 31 to 55 months. Fifty other children of similar demographic profile but without heart disease were also tested as controls.

RESULTS

In group A, there were two neurological deaths. In group B, 5 patients had clinical seizures, 1 had monoparesis and 1 had hyperkinetic syndrome with decreased attention span. Mean mental performance quotient was 90.0+/-8.2 in group A, and 89.1+/-6.8 in group B, (group A vs. B, p = 0.60). Mean mental performance quotient in the control group was 101.4+/-8.4, which was significantly higher than the patient population (p << 0.001). No correlation was found between duration of circulatory arrest and postoperative mental performance quotient.

CONCLUSIONS

There was significant retardation of mental development in infants operated with deep hypothermic cardiopulmonary bypass. However, use of total circulatory arrest and its duration did not affect clinical outcome up to preschool age.

High-dose S(+)-ketamine improves neurological outcome following incomplete cerebral ischemia in rats

PURPOSE

To determine the effects of the non-competitive NMDA-receptor antagonist S(+)-ketamine on neurological outcome in a rat model of incomplete cerebral ischemia.

METHODS

Thirty rats were anesthetized, intubated and mechanically ventilated with isoflurane, O2 30% and nitrous oxide 70%. Following surgery animals were randomly assigned to one of the following treatment groups: Rats in group 1 (n = 10,OFF control) received fentanyl (bolus: 10 microg x kg(-1) i.v.; infusion 25 microg x kg(-1) x h(-1)) and N2O 70% / O2. Rats in group 2 (n = 10) received O2 30% in air and low-dose S(+)-ketamine (infusion: 0.25 mg x kg(-1) x min(-1)). Rats in group 3 (n = 10) received O2 30% in air and high-dose S(+)-ketamine (infusion: 1.0 mg x kg(-1) min(-1)). Following 30 min equilibration period ischemia was induced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to 35 mm Hg for 30 min. Plasma catecholamines were assayed before and at the end of ischemia. Neurological deficit was evaluated for three postischemic days.

RESULTS

Neurological outcome was improved with high-dose S(+)-ketamine when compared to fentanyl / N2O -anesthetized controls (9 vs. 1 stroke related deaths, P<0.05). Increases in plasma catecholamine concentrations were higher in fentanyl / N2O -anesthetized (adrenaline baseline 105.5+/-92.1 pg x ml(-1), during ischemia 948+/-602.8 pg x ml(-1), P<0.05; noradrenaline baseline 407+/-120.2 pg x ml(-1), ischemia 1267+/-422.2 pg x ml(-1), P <0.05) than in high-dose S(+)-ketamine-treated animals (adrenaline baseline 71+/-79.5 pg x ml(-1), ischemia 237 +/-131.9; noradrenaline baseline 317.9+/-310.5 pg x ml(-1), ischemia 310.5+/-85.7 pg x ml(-1)).

CONCLUSION

Neurological outcome is improved following incomplete cerebral ischemia with S(+)-ketamine. Decreases in neuronal injury may be related to suppression of sympathetic discharge.

Predictors of stroke outcome

Recent literature has identified many of the important factors helpful in predicting outcome even at the very acute stage of stroke. Demographic factors, risk factors, clinical exam findings, clinical scales laboratory tests, and neuroimaging all provide important information that can assist the clinician in predicting outcome. Specific factors seem to influence the effect of stroke treatments such as thrombolysis. Consideration of these factors is important when treatment decisions such as thrombolysis are being contemplated. New techniques such as eco-planar MR Imaging are now being developed that seem extremely accurate in predicting outcome. These techniques represent the "crystal ball" of predicting stroke outcome.

Hypoglycemic brain injury: potentiation from respiratory depression and injury aggravation from hyperglycemic treatment overshoots

Hypoglycemia can cause brain dysfunction, brain injury, and death. The present study seeks to broaden current information regarding mechanisms of hypoglycemic brain injury by investigating a novel etiology. The cat's high resistance to brain injury from hypoglycemia suggested that additional influences such as respiratory depression might play a facilitating role. Three groups of cats were exposed to fasting and insulin-induced hypoglycemia (HG; n = 6), euglycemic respiratory depression (RD; n = 5), and combined hypoglycemic respiratory depression (HG/RD; n = 10). The HG animals were maintained at <1.5 mmol (mean 1 mmol) serum glucose concentration for 2 to 6.6 hours. The respiratory depression was associated with PaO2 and PaCO2 values of approximately 50 mm Hg for 1 hour and of approximately 35 and approximately 75 mm Hg, respectively, for the second hour. Magnetic resonance diffusion-weighted imaging estimated brain energy state before, during, and after hypoglycemia. The hypoglycemic respiratory depression exposures were terminated either to euglycemia (n = 4) or to hyperglycemia (n = 6). Brain injury was assessed after 5 to 7 days of survival. Cats exposed to hypoglycemia alone maintained unchanged diffusion coefficients; that is, they lacked evidence of brain energy failure and all six remained brain-intact. Only 1 of 5 euglycemic RD but 10 of 10 HG/RD cats developed brain damage (HG and RD vs. HG/RD, P < 0.01). This difference in brain injury rates suggests injury potentiation by hypoglycemia and respiratory depression acting together. Three injury patterns emerged, including activation of microglia, selective neuronal necrosis, and laminar cortical necrosis. Widespread activation of microglia suggesting damage to neuronal cell processes affected all damaged brains. Selective neuronal necrosis affecting the cerebral cortex, hippocampus, and basal ganglia was observed in all but one case. Instances of laminar cortical necrosis were limited to cats exposed to hypoglycemic respiratory depression treated with hyperglycemia. Thus, treatment with hyperglycemia compared with euglycemia after hypoglycemic respiratory depression exposures significantly increased the brain injury scores (24 +/- 6 vs. 13 +/- 2 points; P < 0.05). This new experimental hypoglycemia model's contribution lies in recognizing additional factors that critically define the occurrence of hypoglycemic brain injury.

Factors influencing the frequency of fluorescence transients as markers of peri-infarct depolarizations in focal cerebral ischemia

BACKGROUND AND PURPOSE

Peri-infarct depolarizations (PIDs) that occur in ischemic boundary zones of the cerebral cortex of experimental animals have been shown to promote rather than simply to indicate the evolution of the lesion and are especially prominent in the rat. To study the influence of one factor, species, on PID incidence, we compared the frequency of PIDs in a primate species, the squirrel monkey, with that in the cat after middle cerebral artery occlusion. Plasma glucose was reviewed as a possible cause of interexperiment variability in the cat experiments.

METHODS

In open-skull experiments under chloralose anesthesia, changes in cortical fluorescence believed to indicate NADH/NAD(+) redox state, as markers of PIDs, were recorded by serial imaging of the cortical surface in vivo for 4 hours after middle cerebral artery occlusion.

RESULTS

Fluorescence transients occurred in squirrel monkeys at a frequency (mean+/-SD) of 0.7+/-0.8 hours(-1) (n=5), which was not significantly less than in that observed in cats (1.3+/-1.6 hours(-1), n=8). Data from the cat experiments indicated a relationship between number of transients (dependent) and plasma glucose, with a striking increase in PID frequency in association with values of mean postocclusion plasma glucose <4.1 mmol/L (Mann-Whitney U=15.0, P=0.034); this observation agrees well with other published findings.

CONCLUSIONS

Transient changes in fluorescence strongly suggestive of peri-infarct depolarizations, either transient or terminal, occur and propagate in the ischemic cerebral cortex of a nonhuman primate. The results also suggest that the relationship of frequency of peri-infarct depolarizations with plasma glucose requires further examination, to confirm the finding and to determine a safe lower limit for a target range for control of plasma glucose if insulin is used in the management of patients with cerebral ischemia.