Stress hormone and blood glucose response following acute stroke in the elderly

Outcome benefit of intensive insulin therapy in the critically ill: Insulin dose versus glycemic control

OBJECTIVES

Maintenance of normoglycemia with insulin reduces mortality and morbidity of critically ill patients. Here we report the factors determining insulin requirements and the impact of insulin dose vs. blood glucose control on the observed outcome benefits.

DESIGN

A prospective, randomized, controlled trial.

SETTING

A 56-bed predominantly surgical intensive care unit in a tertiary teaching hospital.

PATIENTS AND INTERVENTION

A total of 1,548 patients were randomly assigned to either strict normalization of blood glucose (80-110 mg/dL) with insulin infusion or the conventional approach, in which insulin is only given to maintain blood glucose levels at 180-200 mg/dL.

MEASUREMENTS AND MAIN RESULTS

It was feasible and safe to achieve and maintain blood glucose levels at <110 mg/dL by using a titration algorithm. Stepwise linear regression analysis identified body mass index, history of diabetes, reason for intensive care unit admission, at-admission hyperglycemia, caloric intake, and time in intensive care unit as independent determinants of insulin requirements, together explaining 36% of its variation. With nutritional intake increasing from a mean of 550 to 1600 calories/day during the first 7 days of intensive care, normoglycemia was reached within 24 hrs, with a mean daily insulin dose of 77 IU and maintained with 94 IU on day 7. Insulin requirements were highest and most variable during the first 6 hrs of intensive care (mean, 7 IU/hr; 10% of patients required >20 IU/hr). Between day 7 and 12, insulin requirements decreased by 40% on stable caloric intake. Brief, clinically harmless hypoglycemia occurred in 5.2% of intensive insulin-treated patients on median day 6 (2-14) vs. 0.8% of conventionally treated patients on day 11 (2-10). The outcome benefits of intensive insulin therapy were equally present regardless of whether patients received enteral feeding. Multivariate logistic regression analysis indicated that the lowered blood glucose level rather than the insulin dose was related to reduced mortality (p <.0001), critical illness polyneuropathy (p <.0001), bacteremia (p =.02), and inflammation (p =.0006) but not to prevention of acute renal failure, for which the insulin dose was an independent determinant (p =.03). As compared with normoglycemia, an intermediate blood glucose level (110-150 mg/dL) was associated with worse outcome.

CONCLUSION

Normoglycemia was safely reached within 24 hrs and maintained during intensive care by using insulin titration guidelines. Metabolic control, as reflected by normoglycemia, rather than the infused insulin dose, was related to the beneficial effects of intensive insulin therapy.

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.

Energy metabolism, stress hormones and neural recovery from cerebral ischemia/hypoxia

All the advancements in the understanding of the molecular and cellular processes leading to the great investments in developing neuroprotection against cerebral ischemic/hypoxic damage cannot obscure the simple fact that exhaustion of energy supplies is still at the basis of this disorder. Much has been investigated and postulated over the years about the quick collapse of energy metabolism that follows oxygen and glucose deprivation in the brain. Anaerobic glycolysis, recognized as a pathway of paramount importance in keeping energy supplies, although, at bare minimum, has also presented a dilemma-a significant increase in lactate production during ischemia/hypoxia (IH). The dogma of lactate as a useless end product of anaerobic glycolysis and its postulated role as a detrimental player in the demise of the ischemic cell has persisted for the past quarter of a century. This persistence is due to, at least in part, the well-documented phenomenon termed "the glucose paradox of cerebral ischemia," the unexplained aggravation of postischemic neuronal damage by preischemic hyperglycemia. Recent studies have questioned the deleterious effect of lactic acid, while others even have offered the possibility that this monocarboxylate serves as an aerobic energy substrate during recovery from IH. Reviewed here are studies published over the past few years along with some key older papers on the topic of energy metabolism and recovery of neural tissue from IH. New insights gained from both in vitro and in vivo studies on energy metabolism of the ischemic/hypoxic brain should improve our understanding of this key metabolic process and the chances of protecting this organ from the consequences of energy deprivation.

Blood glucose increases early after stroke onset: a study on serial measurements of blood glucose in acute stroke

The aim of this study was to evaluate if blood glucose levels change within the first 12 h after stroke onset and to investigate if the degree of change is related to stroke severity, type of stroke, or prognosis. This was a retrospective, descriptive trial based on 445 stroke patients with two blood glucose tests within 12 h of stroke onset and no history of diabetes mellitus. Blood glucose increased in the first 12 h after stroke onset; in mild to moderate stroke from 5.8 to 6.1 mmol/l (P < 0.001) and in severe stroke from 6.2 to 6.7 mmol/l (P < 0.001). In patients who died within 7 days of stroke onset, blood glucose increased from 6.8 to 7.1 mmol/l (P < 0.001). In conclusion, blood glucose increases after the onset of acute stroke and the increase is related to the severity of the stroke.

Hypercortisolemia in acute stroke is related to the inflammatory response

Hypercortisolemia is thought to be a marker of the stress response following stroke. The aim of this study was to investigate the prevalence and prognostic significance of hypercortisolemia. The circadian variation of cortisol level and the relationship between serum cortisol levels and other stress, inflammatory, and haemostatic markers were also investigated. Seventy consecutive patients with their first ischemic stroke and 24 age- and sex-matched controls were included in the study. Serum cortisol levels (at 6:00 AM, 10:00 AM, 6:00 PM, and 10:00 PM), 24-h urine catecholamine excretion, beta-thromboglobulin levels, and other standard biochemical and haematological parameters were measured on the first day of hospitalisation and in control subjects. Outcome measures used the Barthel Index at Day 30, as well as 30- and 90-day mortality rates. Hypercortisolemia, defined as at least two of the four measurements above the normal range of serum cortisol levels (i.e. >618 nmol/l from the morning samples and >460 nmol/l from the evening samples) was found in 25 (35.7%) of the acute stroke patients and in 3 (12.5%) of the controls (p<0.05). Hypercortisolemia was associated with older age, greater severity of neurological deficit, larger ischemic lesions on CT, and worse prognoses (p<0.05). The study did not find a correlation between serum cortisol levels and other markers of the stress response such as catecholamines excretion and glucose levels. A significant correlation between serum cortisol levels and some markers of the inflammatory response, such as fever, fibrinogen level, white blood cell (WBC) count, and beta-thromboglobulin level, was established in stroke patients. Prognostic significance of hypercortisolemia in acute stroke patients seems to be related to the inflammatory response rather than to the stress response.

Bench-to-bedside review: a possible resolution of the glucose paradox of cerebral ischemia

The glucose paradox of cerebral ischemia (namely, the aggravation of delayed ischemic neuronal damage by preischemic hyperglycemia) has been promoted as proof that lactic acidosis is a detrimental factor in this brain disorder. Recent studies, both in vitro and in vivo, have demonstrated lactate as an excellent aerobic energy substrate in the brain, and possibly a crucial one immediately postischemia. Moreover, evidence has been presented that refutes the lactic acidosis hypothesis of cerebral ischemia and thus has questioned the traditional explanation given for the glucose paradox. An alternative explanation for the aggravating effect of preischemic hyperglycemia on the postischemic outcome has consequently been offered, according to which glucose loading induces a short-lived elevation in the release of glucocorticoids. When an episode of cerebral ischemia in the rat coincided with glucose-induced elevated levels of corticosterone (CT), the main rodent glucocorticoid, an aggravation of the ischemic outcome was observed. Both the blockade of CT elevation by chemical adrenalectomy with metyrapone or the blockade of CT receptors in the brain with mifepristone (RU486) negated the aggravating effect of preischemic hyperglycemia on the postischemic outcome.

Preischemic hyperglycemia-aggravated damage: evidence that lactate utilization is beneficial and glucose-induced corticosterone release is detrimental

Aerobic lactate utilization is crucial for recovery of neuronal function posthypoxia in vitro. In vivo models of cerebral ischemia pose a conceptual challenge when compared to in vitro models. First, the glucose paradox of cerebral ischemia, namely, the aggravation of delayed neuronal damage by preischemic hyperglycemia, cannot be reproduced in vitro. Second, in vitro elevated glucose levels protect against ischemic (hypoxic) damage, an outcome that has seldom been reproduced in vivo. Employing a rat model of cardiac-arrest-induced transient global cerebral ischemia (TGI), we found that hyperglycemic conditions, when induced 120-240 min pre-TGI, significantly reduced post-TGI neuronal damage as compared to normoglycemic conditions. In contrast, hyperglycemia, when induced 15-60 min pre-TGI, significantly aggravated post-TGI neuronal damage. Brain lactate levels in rats loaded with glucose either 15 min or 120 min pre-TGI were significantly and equally higher than those of control, saline-injected rats. The beneficial effect of 120 min pre-TGI glucose loading was abolished by lactate transport inhibition. A significant increase in blood corticosterone (CT) levels was observed upon glucose loading that peaked at 15-30 min and returned to baseline levels by 60-120 min. When rats loaded with glucose 15 min pre-TGI were treated with metyrapone, a CT synthesis inhibitor, a significantly lower degree of delayed neuronal damage in comparison to both untreated, 15 min glucose-loaded rats and normoglycemic, control rats was observed. Thus, although elevated levels of brain lactate cannot explain the glucose paradox of cerebral ischemia, hyperglycemia-induced, short-lived elevation in CT blood levels could. More importantly, lactate appears to play a crucial role in improving postischemic outcome.

Alterations in fuel metabolism in critical illness: hyperglycaemia

Hyperglycaemia is common during critical illness and may be viewed teleologically as a means of ensuring an adequate supply of glucose for the brain and phagocytic cells. Under normal conditions, euglycaemia is maintained by neural, hormonal and hepatic autoregulatory mechanisms. Critical illness promotes hyperglycaemia through an activation of the hypothalamic-pituitary-adrenal axis, which in turn increases hepatic glucose production and inhibits insulin-mediated glucose uptake to skeletal muscle. Sustained hyperglycaemia is associated with adverse consequences that demand its control. Appropriate management includes discontinuing causative drugs, correcting hypokalaemia, treating infection and administering insulin. Insulin therapy also appears to be useful for promoting an anabolic response in skeletal muscle.

Intensive insulin therapy in critically ill patients

BACKGROUND

Hyperglycemia and insulin resistance are common in critically ill patients, even if they have not previously had diabetes. Whether the normalization of blood glucose levels with insulin therapy improves the prognosis for such patients is not known.

METHODS

We performed a prospective, randomized, controlled study involving adults admitted to our surgical intensive care unit who were receiving mechanical ventilation. On admission, patients were randomly assigned to receive intensive insulin therapy (maintenance of blood glucose at a level between 80 and 110 mg per deciliter [4.4 and 6.1 mmol per liter]) or conventional treatment (infusion of insulin only if the blood glucose level exceeded 215 mg per deciliter [11.9 mmol per liter] and maintenance of glucose at a level between 180 and 200 mg per deciliter [10.0 and 11.1 mmol per liter]).

RESULTS

At 12 months, with a total of 1548 patients enrolled, intensive insulin therapy reduced mortality during intensive care from 8.0 percent with conventional treatment to 4.6 percent (P<0.04, with adjustment for sequential analyses). The benefit of intensive insulin therapy was attributable to its effect on mortality among patients who remained in the intensive care unit for more than five days (20.2 percent with conventional treatment, as compared with 10.6 percent with intensive insulin therapy, P=0.005). The greatest reduction in mortality involved deaths due to multiple-organ failure with a proven septic focus. Intensive insulin therapy also reduced overall in-hospital mortality by 34 percent, bloodstream infections by 46 percent, acute renal failure requiring dialysis or hemofiltration by 41 percent, the median number of red-cell transfusions by 50 percent, and critical-illness polyneuropathy by 44 percent, and patients receiving intensive therapy were less likely to require prolonged mechanical ventilation and intensive care.

CONCLUSIONS

Intensive insulin therapy to maintain blood glucose at or below 110 mg per deciliter reduces morbidity and mortality among critically ill patients in the surgical intensive care unit.

Endocrine abnormalities and outcome of ischaemic stroke

Multiple endocrine abnormalities have been reported in stroke patients. In the past few years, it has been claimed that some of these abnormalities may play a role in worsening the neurological deficit and the outcome of stroke. Several mechanisms have been hypothesised, including a direct effect on the development of neuronal cell death, vasospasm, and development of brain edema. In this brief review, we discuss the current knowledge concerning the role of endothelin-1, arginine vasopressin, and cortisol in the pathogenesis of stroke. Finally, we discuss the possibility that leptin, the OB gene product, may be the link of some of these endocrine abnormalities, and that its abnormal secretion during stroke may contribute to the eating disorders and poor nutritional status often seen in these patients.

Transient hyperglycemia in ischemic stroke patients

The aim of the study was to investigate glucose derangement and its short- and long-term prognostic significance in nondiabetic ischemic stroke patients. The study involved 262 consecutive patients, mean age: 70.1+/-12.4 years, with a supratentorial ischemic stroke. The following data were collected: patients characteristics, risk factors, comorbidities, and stroke severity assessed by the Scandinavian Stroke Scale (SSS). Serum glucose levels were measured on admission, on the next, 2nd, 3rd, 5th, 7th and 14th day after stroke onset. The outcome measures on day 30 were mortality and capacity to perform daily activities: the Barthel Index and Rankin Scale. The 1-year survival was estimated by the Kaplan-Meier method. Cox proportional hazards regression was used to assess predictors of 1-year mortality in nondiabetics. Diabetes mellitus was found in 24.8% of patients and transient hyperglycemia in 36.3% of patients. Patients with transient hyperglycemia scored lower on SSS in the subsequent days of assessment than patients with either diabetes mellitus or normoglycemia. They had larger ischemic lesions on computer tomography (CT) than diabetics and had higher 30-day mortality than normoglycemics (p<0.05). One-year mortality was similar in transient hyperglycemics and diabetics, and both were significantly higher than in normoglycemics (p<0.05). A proportional hazards model analysis showed that transient hyperglycemia is not an independent predictor of death within a year after stroke.

Influence of hyperglycemia on stroke mortality

BACKGROUND

The influence of hyperglycemia on stroke mortality is controversial. The aim of this study was to investigate the prognostic role of hyperglycemia and diabetes on short-term and long-term mortality in patients with acute ischemic stroke.

METHODS

This retrospective cohort study included 416 acute ischemic stroke patients admitted to a tertiary hospital between July 1, 1995 and June 30, 1997. In-hospital mortality and 1-year mortality after discharge were the outcomes of the study. All patients were classified into four groups according to the glucose status and history of diabetes: group 1, normoglycemic without diabetes; group 2, normoglycemic with diabetes; group 3, hyperglycemic with diabetes and group 4, hyperglycemic without diabetes. Cochrane-Armitage trend test was used to assess the trend of mortality across the 4 groups. The influence of hyperglycemia on in-hospital and 1-year mortality were studied by logistic regression and Cox proportional hazards regression adjusting for confounders.

RESULTS

The Cochrane-Armitage trend test showed there was a strong trend towards increasing in-hospital mortality across groups 1 to 4 (P < .001). Hyperglycemia without a history of diabetes was an independent predictor of in-hospital mortality, odds ratio 3.0 (95% confidence interval: 1.1-8.3; P = .035). Hyperglycemia (with or without diabetes) did not predict in-hospital mortality significantly. Neither hyperglycemia per se nor hyperglycemia without a history of diabetes were significant in predicting 1-year mortality.

CONCLUSION

Hyperglycemia without diabetes is independently associated with higher in-hospital mortality in patients with acute ischemic stroke. There was a trend to increasing in-hospital mortality across groups 1 to 4.

Stress-induced hyperglycemia

Stress hyperglycemia is common and likely to be associated with at least some of the same complications as hyperglycemia in true diabetes mellitus, such as poor wound healing and a higher infection rate. The predominant cause is the intense counterregulatory hormone and cytokine responses of critical illness, often compounded by excessive dextrose administration, usually as TPN. Although randomized data suggesting benefit of controlling hyperglycemia in hospitalized patients are paltry, prospective controlled trials are feasible and should be initiated. In the interim, the practice at the authors' institution is to use insulin to lower plasma glucose concentrations to a safe range of 150 mg/dL to 200 mg/dL in all patients.

Hospital management of diabetes

The degree of hyperglycemia may be an important predictor of morbidity and mortality among patients with MI or stroke, and in those undergoing surgical procedures including coronary artery bypass. Hyperglycemia should be aggressively controlled from the time of hospital admission regardless of the patient's primary medical problem or previous diabetes status. Innovative systems for monitoring glucose and for delivering insulin coupled with new pharmacologic therapy, such as long-acting insulin analogues, may help reduce the morbidity and mortality occurring in the estimated 6 million annual hospitalizations that are accompanied by hyperglycemia in the United States.

Initial hyperglycemia as an indicator of severity of the ictus in poor-grade patients with spontaneous subarachnoid hemorrhage

An association between hyperglycemia and outcome in spontaneous subarachnoid hemorrhage (SAH) has been sporadically reported. Our hypothesis was that hyperglycemia is a sign of central metabolic disturbance linked with specific appearances on computerized tomography (CT) scans reflecting different degrees of corresponding brain injury. The admission plasma glucose level, initial CT findings, and outcome after 6 months were analysed in a cohort of 99 patients with SAH in Hunt & Hess Grade IV or V. The CT scans were quantitatively assessed for subarachnoid blood, intracerebral hematoma, intraventricular hemorrhage, hydrocephalus, midline shift and compression of the perimesencephalic cisterns. These findings were combined to determine a three-point CT severity score. All patients showed elevated (>5.8 mmol/l) plasma glucose levels on admission. Mortality among 33 patients with glucose concentration below 9.0 mmol/l was 33.3%, 71.1% for the 45 patients with glucose level between 9.0 and 13.0 mmol/l, and 95.2% for the 21 patients with concentration above 13.0 mmol/l (P<0.0001). Glucose level was higher in Grade V than in Grade IV patients (mean+/-SD) (11.8+/-3.2 vs 9.8+/-2.9 mmol/l; P=0.0012). Patients with mild CT findings (n=10) had the lowest glucose level (8.9+/-1.8 mmol/l; P=0.0082), whereas patients with severe findings (n=56) had the highest glucose (11.4+/-3.5 mmol/l; P=0.011). Despite association with clinical grade and extent of CT findings, logistic multiple regression revealed the admission plasma glucose level to be an independent prognosticator of outcome. The prognostic potential of the initial plasma glucose level may be beneficial in management protocols of poor-grade SAH patients.

Infarct volume and functional outcome after pre- and postoperative administration of metyrapone, a steroid synthesis inhibitor, in focal brain ischemia in the rat

High blood levels of glucocorticoids are associated with increased mortality, confusion and poor functional outcome in stroke patients. It has been proposed that inhibition of glucocorticoids in acute stroke might be beneficial, but experimental data are conflicting and no long-term follow-up study has been reported. We have studied whether pre- or postoperative administration of metyrapone, a steroid synthesis inhibitor, can influence long-term outcome after ligation of the right middle cerebral artery (MCA) distal to the striatal branches in hypertensive rats. Metyrapone (200 mg/kg) was administered either 30 min before or 1, 12 and 24 h after MCA occlusion. Limb placements and ability to traverse a rotating pole were evaluated pre- and postoperatively. Infarct size, histology and GFAP immunoreactivity were evaluated on 5 microm coronal sections from brains perfused in situ 4 weeks after the ischemic event. Pretreatment did not influence outcome, whereas postoperative administration of metyrapone significantly increased infarct volume (P < 0.05). Post-treated rats performed significantly worse than vehicle-treated rats on the rotating pole 3 weeks after the operation (P < 0.05). Our results do not support the hypothesis that inhibition of glucocorticoid synthesis improves outcome after cerebral ischemia.

Hypokalemia and potassium excretion in stroke patients

OBJECTIVES

To determine (1) the prevalence of hypokalemia (plasma potassium < or = 3.4 mmol/L) in a group of stroke patients in comparison with age- and sex-matched groups of patients having sustained a myocardial infarction or having mild hypertension and (2) the association between plasma potassium concentration and stroke outcome.

DESIGN

Observational study.

PARTICIPANTS

A total of 421 consecutive stroke patients admitted to a teaching hospital, 150 consecutive patients 50 years or older with myocardial infarction admitted to the hospitals Coronary Care Unit, and 161 out-patients 60 years or older with borderline and established hypertension.

MEASUREMENTS

All stroke and cardiac patients had plasma urea and electrolytes estimated within 2 hours of hospital admission; in the hypertensive group blood samples were taken in clinic. Stroke patients had blood pressure, stroke severity (Barthel score) and smoking status recorded. A sub-group of 61 stroke patients and all 79 hypertensive patients not taking antihypertensive medication had 24-hour urine electrolyte excretion measured. Outcome (independent, dependent, or dead) at 3 months post-stroke was established in 349 patients.

RESULTS

Hypokalemia occurred more frequently in stroke patients than in patients with myocardial infarction (84 (20%) vs 15 (10%), P = .008) or patients with hypertension (84 (20%) vs 13 (8%), P < .001), even when patients taking diuretics were excluded from analysis (56 (19%) vs 12 (9%) of cardiac group, P = .014 and 56 (19%) vs 4 (5%) of hypertensive group, P = .005, respectively). 24-hour urine excretion of potassium and the potassium:creatinine ratio was lower in stroke patients than in hypertensive patients (41 +/- 21 vs 62 +/- 25 mmol/24 hour, P = .001, 5.5 +/- 2.2 vs 7.4 +/- 2.6 mmol/24 hour, P = .001, respectively). On survival analysis, a lower plasma potassium on admission to hospital was associated with an increased chance of death, independent of age, stroke severity, history of hypertension, blood pressure level, or smoking history (hazard ratio 1.73 (95% CI: 1.03-2.9) for a 1 mmol/L lower plasma potassium concentration).

CONCLUSIONS

Hypokalemia post stroke is common and may be associated with a poor outcome.

Clinical implications of poststroke hypothalamo-pituitary adrenal axis dysfunction: A critical literature review

Persistent hypothalamo-pituitary adrenal axis dysregulation occurs in up to 40% of patients who have suffered a stroke. The degree of hypercortisolemia is partly determined by the size and site of the vascular lesion. Adrenocortical hyperactivity begins almost immediately after a cerebrovasacular infarct but is persistent in an important subgroup of patients. In the early poststroke period (1 day to 1 month) high corticosteroid levels correlate with the presence of an acute confusional state. In the medium term (1 month to 1 year) hypercortisolemia is associated with the development of a major depressive episode and also relates to functional outcome and survival. Neuroanatomical deficits (particularly in the frontal or medial temporal lobes), age of onset, cognitive impairment, and reduced functional status may act as maintaining factors in both the poststroke depression and the adrenocortical hyperactivity. Patients with persisting hypercortisolemia, with or without depression or cognitive impairment, have a worse prognosis with an increased mortality rate. The mechanism for this effect may involve induced hyperglycemia or direct glucocorticoid neurotoxicity, which impairs the brain's capacity for recovery. It is suggested that the cautions use of antiglucocorticoid strategies may be of value in the medical management of the neuropsychiatric complications that follow cerebrovascular accidents.

The neurologic implications of diabetic hyperglycemia during surgical procedures at increased risk for brain ischemia

The neurologic implications of diabetic hyperglycemia depend on whether the ischemic insult is permanent or temporary. Laboratory studies show that following permanent focal ischemia, a situation analogous to stroke, diabetic hyperglycemia is protective in the penumbral region, whereas it may slightly increase infarct size. In addition, clinical studies cannot unequivocally attribute poor outcome in diabetic stroke patients to hyperglycemia. Thus, both laboratory and clinical studies have been unable to define a cause and effect relationship between diabetic hyperglycemia and neurologic outcome following stroke. On the other hand, diabetic hyperglycemia is an important determinant of neurologic outcome following temporary focal ischemia (analogous to temporary occlusion of a cerebral vessel) and global ischemia (analogous to circulatory arrest). Based on laboratory studies, aggressive insulin-based blood glucose management with the goal of euglycemia is imperative prior to temporary ischemia. However, intraoperative ischemic events are overwhelmingly of a permanent focal nature, and the neurologic implications of diabetic hyperglycemia for the vast majority of surgical procedures at increased risk for brain ischemia are minimal. It is only in circumstances where temporary focal or global ischemia are used as part of the surgical procedure that aggressive insulin-based blood glucose management is warranted.

Nutritional management of the critically ill neurologic patient

To summarize, the event of severe neurologic injury results in significant metabolic changes. These changes cause increased requirements for protein and nonprotein calories, micronutrients, and small bowel feedings or TPN. Early feeding has been shown to improve survival. Therefore, every effort should be made to provide aggressive nutritional support within the first 72 hours after injury. Specific guidelines are as follows: Provide full-strength, full-rate feedings within 72 hours. Provide enteral nutrients via nasojejunal or percutaneous endoscopic jejunostomy feeding tube if access is available; attempt gastric feedings if not. Provide TPN within 48 hours if enteral access is not available and begin enteral feeding as soon as possible. Provide 2 to 2.3 g protein/kg/d if renal function is normal. Provide 40% to 70% above basal needs as total calories, with 30% to 40% of calories as lipid to minimize hyperglycemia. Provide protein as small peptides to improve tolerance, absorption, utilization, and gut integrity. Provide a lipid source with 50% to 70% medium-chain triglycerides and an omega-6 to omega-3 ratio of 2:1 to 8:1 to minimize negative effects of omega-6 fatty acids and provide an easily absorbed and utilized source of lipid.

The Copenhagen Stroke Study experience

The Copenhagen Stroke (COST) Study was a prospective, consecutive, community-based study of 1,197 patients with acute stroke who underwent acute stroke care and rehabilitation in a stroke unit setting. This article reviews the results of this study with respect to (1) the effect of organized stroke care and rehabilitation, (2) neurological outcome and functional outcome of stroke in relation to initial stroke severity and functional disability, (3) recovery of upper-extremity function and walking, (4) time course of neurological and functional recovery relative to initial stroke severity, (5) mechanisms of stroke recovery, and (6) the effect on stroke recovery of various demographic, medical, and pathophysiological factors, such as stroke in progression, spontaneous reperfusion age, diabetes, blood glucose on admission, stroke type (hemorrhage/infarction), silent infarction, and leuco-araiosis.

Glucose modulation of ischemic brain injury: review and clinical recommendations

Ischemic brain injury is the third-leading cause of death among Americans and the leading cause of serious disability. Based on studies of animal models, a substantial amount of experimental evidence shows that hyperglycemia at the onset of brain ischemia worsens postischemic neurologic outcome. Consistent with these observations, hyperglycemia also is associated with a worsening of postischemic brain injury in humans. In humans, however, data are often difficult to interpret because of problems in determining the timing of hyperglycemia relative to a critical ischemic event and in elucidating the effect of coexisting pathophysiologic processes (for example, a stress response) on outcome. Glucose modulation of neurologic injury is observed when ischemia is either global (for example, that accompanying cardiac arrest or severe systemic hypotension) or focal (for example, that accompanying thrombotic or embolic stroke). Toxicity is probably the result of an intracellular lactic acidosis. Specifically, the associated hydrogen ions are injurious to neurons and glia. On the basis of these factors, we recommend diligent monitoring of blood glucose concentrations in patients who are at increased risk for new-onset, ongoing, or recurring cerebral ischemia. In such patients, the use of fluid infusions, corticosteroid drugs, and insulin, as well as stress management, should be tailored to treat preexisting hyperglycemia and prevent new-onset hyperglycemia. Maintenance of normoglycemia is recommended. When one attempts to treat preexisting hyperglycemia, care should be taken to avoid rapid fluid shifts, electrolyte abnormalities, and hypoglycemia, all of which can be detrimental to the brain.

Cerebrovascular disorders in patients with diabetes mellitus

Diabetes mellitus is a risk factor for ischemic, but not hemorrhagic stroke. The frequency of transient ischemic attacks is not increased in patients with diabetes compared to the general population. Diabetes mellitus is associated with higher mortality, worse functional outcome, more severe disability after stroke and a higher frequency of recurrent stroke. Diabetes is not associated with an increased size of cerebral infarction. Controversy exists regarding whether hyperglycemia adversely affects stroke outcome or primarily reflects stroke severity. Cerebral blood flow disturbances, impaired cerebrovascular reactivity, and damage to large and small extra- and intracranial cerebral vessels have been found in humans and animals with diabetes. Combinations of some or all of these factors may underlie the high incidence and worse outcome of stroke in patients with diabetes. Knowledge of these pathophysiologic factors will assist in the design of future intervention strategies.

Serial changes in blood pressure and neurohormone levels after the onset of lacunar stroke

To assess serial changes in blood pressure and its circadian variation following a lacunar stroke, the authors studied 7 patients who developed a single lacunar infarction in either the internal capsule or the corona radiata. Blood pressure and pulse rate were monitored noninvasively for twenty-four hours by an ambulatory blood pressure monitoring device in the acute, subacute, and chronic phases of the strokes. In the acute and chronic phases, the authors also measured urinary excretion of catecholamines every 6 hr, and serum cortisol concentration at 9:00, 17:00, and 21:00 hr. The patients were free from antihypertensive agents during the study. The twenty-four-hour averages of both systolic and diastolic blood pressure in the chronic phase were lower than those in the acute phase (P < 0.05). A nighttime fall in blood pressure was observed in the subacute and chronic phases (P < 0.05), but not in the acute phase. Urinary excretion of epinephrine at night in the acute phase was significantly higher than that in the chronic phase (P < 0.05). Serum levels of cortisol at 17:00 and 21:00 hr in the acute phase also exceeded those in the chronic phase (P < 0.05 and P < 0.01, respectively). The authors conclude that an increased secretion of epinephrine and cortisol might, at least in part, contribute to a high blood pressure and a lack of circadian variation in blood pressure in the acute phase of lacunar stroke.

Insulin reduction of cerebral infarction due to transient focal ischemia

Insulin has recently been shown to ameliorate damage in models of global brain ischemia. To determine whether insulin is also neuroprotective in focal ischemia, 20 rats were given 2 to 3 IU/kg insulin and 10 did not receive treatment prior to normothermic transient middle cerebral artery occlusion for 2 hours at a blood pressure of 60 mm Hg. To further elucidate whether infarction volume is influenced by variations in blood glucose levels within the physiological range, blood glucose was raised in 10 of the insulin-treated animals to levels comparable with the untreated controls. At 1-week survival, damage was assessed using quantitative neuropathological examination of 25 coronal planes. It was found that preischemic insulin lowered the mean intraischemic blood glucose level from 8.4 +/- 0.2 mM (mu +/- standard error of the mean) in the control group to 3.4 +/- 0.2 mM and reduced total damage (atrophy plus cortical and striatal necrosis), expressed as the percentage of the normal hemisphere, from a control of 28.5% +/- 2.9% to 14.5% +/- 1.6% (p < 0.005). Coadministration of glucose and insulin resulted in a mean intraischemic blood glucose level of 10.1 +/- 0.5 mM, with 27.0% +/- 2.4% total damage (p = 0.96, compared with control). Total ischemic damage showed an independent correlation with blood glucose levels (r = 0.67, p = 0.0018). The findings indicate that insulin benefits transient focal ischemia and that reducing the blood glucose from 8 to 9 mM to the low-normal range of 3 to 4 mM with insulin dramatically reduces subsequent infarction. The data suggest that the neuroprotective mechanism of insulin action in focal middle cerebral artery occlusion is mediated predominantly via alterations in blood glucose levels. In comparison to global ischemia, focal ischemia appears to show only a minor direct central nervous system effect of insulin. In clinical situations in which transient focal ischemia to the hemisphere can be anticipated, insulin-induced hypoglycemia of a mild degree may be beneficial.

Glucocorticoids increase extracellular [3H]D-aspartate overflow in hippocampal cultures during cyanide-induced ischemia

Glucocorticoids (GCs), the adrenal steroid hormones secreted during stress, exacerbate neuronal death in the hippocampus during ischemia. Since ischemia brain damage is ascribed to an elevated level of extracellular excitatory amino acids (EAAs), this study was undertaken to investigate the effect of GCs on EAA homeostasis in hippocampal cell cultures during the insult of cyanide exposure. Using D-[2,3-3H]aspartic acid ([3H]D-Asp) as a tracer, we found that corticosterone (CORT, the physiological GC in rats) increased the accumulation of extracellular [3H]D-Asp by 25% in hippocampal cultures during cyanide-induced ischemia. CORT had no effect on the release of [3H]D-Asp. Instead, analysis of [3H]D-Asp uptake kinetics indicates that CORT decreased the maximum uptake rate and the Michaelis constant by 44% and 50%, respectively, in cells treated with cyanide. It is concluded that, during cyanide-induced ischemia, CORT might enhance extracellular overflow of [3H]D-Asp by decreasing its uptake, thereby endangering neurons.

Food deprivation protects the rat striatum against hypoxia-ischemia despite high extracellular glutamate

In a model that combines hypoxia with ischemia, the relationship between histological outcome, evoked rise in blood glucose, and striatal glutamate release was investigated in the 24-h food-deprived and normally fed rat. Food deprivation protected the dorsolateral striatum very effectively, as was shown with a silver stain. An online monitoring technique based on microdialysis showed that, in the protected condition, more glutamate was released into the striatal extracellular space than in the compromised condition. The possibility that the microdialysis results were influenced by a difference in shrinking of the extracellular space following food deprivation was excluded by the measurements of whole-tissue impedance. During the hypoxic-ischemic challenge, blood glucose rose in normally fed rats, but was suppressed almost completely after food deprivation. These results led us to conclude that, in our model of hypoxia-ischemia, the amount of glutamate released is not related directly to the extent of brain damage, but the increase in blood glucose may determine at least part of the brain damage.

Prevalence of stress hyperglycemia among patients attending a pediatric emergency department

OBJECTIVE

To determine the prevalence and clinical characteristics associated with stress hyperglycemia among children and adolescents attending a pediatric emergency department.

DESIGN

Patients who required a venipuncture for evaluation of an acute illness or injury from October 1992 to March 1993 in an urban pediatric emergency department were enrolled and screened prospectively for hyperglycemia (glucose level > or = 8.3 mmol/L; > or = 150 mg/dl). Data were collected regarding demographic characteristics, history, clinical findings, and admission status.

RESULTS

A total of 926 patients ranging in age from 3 days to 21 years were enrolled. Blood glucose values ranged from 1.94 mmol/L (35 mg/L) to 14.65 mmol/L (264 mg/dl); 35 patients (3.8%) had hyperglycemia. The prevalence of stress hyperglycemia was significantly increased among patients if they (1) had temperatures greater than 39.5 degrees C (9.3%) versus normal temperatures (2.8%) (p < 0.001), (2) had been admitted to a critical care unit of the hospital (24.1%) or to any hospital unit (4.4%) versus not having been admitted (2.6%) (p < 0.001), and (3) had received fluids intravenously (6.0%) versus having received no fluids intravenously (2.7%) (p = 0.014).

CONCLUSIONS

Stress hyperglycemia is a frequent clinical occurrence in a pediatric emergency department. It does not appear to be associated with a particular diagnostic category but is significantly associated with severity of illness as measured by elevated temperature, hospital admission, and hydration status.

Serum cortisol and outcome of ischemic brain infarction

The predictive value of serum cortisol level on the prognosis in acute brain infarction of the carotid circulation territory was studied in 101 patients younger than 70 years. The levels of 7 a.m. and 7 p.m. serum cortisol were measured initially and at 1 week. All patients underwent a computed cerebral tomography (CT) within 2 days of the onset of symptoms, and a second CT 3 weeks or 3 month later. Serum cortisol values predicted the stroke outcome. Both the 7 a.m. and the 7 p.m. values in the initial and 1-week samples correlated positively with the severity of hemiparesis on the corresponding days. The 7 p.m. values predicted better than the 7 a.m. values the functional outcome and case fatality during the 3 month follow-up. Initially and at 1 week, the median 7 p.m. serum cortisol values were statistically significantly higher in those with frontally extending infarcts than in those with non-frontal infarcts. Both 7 a.m. fasting blood glucose and glycosylated hemoglobin (HbA1c) measurements were taken within 3 days of the onset in 95 cases. The patients were diagnosed to have prestroke normoglycemia (n = 73) and hyperglycemia (n = 22) on the basis of the HbA1c level. A highly significant (P = 0.0001) correlation was demonstrated between the initial 7 p.m. cortisol and 7 a.m. fasting blood glucose values in those with prestroke normoglycemia, suggesting that hyperglycemia during the acute phase of stroke is a stress response.

Blood glucose, glycosylated haemoglobin, and outcome of ischemic brain infarction

From August 1987 through December 1989 all consecutive conscious patients younger than 70 years with a recent (less than 48 h) brain infarction of the carotid territory were prospectively included in the study. Blood samples for fasting blood glucose and glycosylated haemoglobin (HbA1c) were taken after a median delay of 23 h of the onset of symptoms. The severity of hemiparesis was assessed on admission, at 1 week, 3 weeks, and 3 months. The functional outcome was assessed at 3 months. Computed cerebral tomography was performed on admission, and later on at 3 weeks or 3 months. The brain infarct volume was measured from the CTs. The patients were diagnosed to have prestroke normoglycemia (n = 76) and prestroke hyperglycemia (n = 23) on basis of the HbA1c level. The case fatality rate, severity of hemiparesis, functional outcome, and infarct size did not differ between these 2 groups. On the other hand, fasting blood glucose level of the non-diabetics correlated strongly with the severity of hemiparesis and predicted stroke outcome. A statistically significant correlation was observed between blood glucose values and the volumes of cortical infarcts in non-diabetics. Because prestroke blood glucose level, in contrast to post-stroke blood glucose level, did not have any predictive value concerning stroke outcome it is concluded that high fasting blood glucose values after stroke reflect a stress response to a more severe ischemic brain lesion.