Baseline hemodynamic state and response to hemodilution in patients with acute cerebral ischemia

Fifty Years of Acute Ischemic Stroke Treatment: A Personal History

BACKGROUND

It has been 50 years since the first explorations of the physiology of cerebral ischemia by measuring cerebral blood flow (CBF), and 25 years since the approval of tissue plasminogen activator for treating acute ischemic stroke. My personal career began and matured during those eras. Here, I provide my perspective on the evolution of acute stroke research and treatment from 1971 to the present, with some in-depth discussion of the National Institutes of Neurologic Disease and Stroke (NINDS) tissue-type plasminogen activator (tPA) stroke trial and development of mobile stroke units.

SUMMARY

Studies of CBF and metabolism in acute stroke patients revealed graded tissue injury that was dependent on the duration of ischemia. Subsequent animal research unraveled the biochemical cascade of events occurring at the cellular level after cerebral ischemia. After a decade of failed translation, the development of a relatively safe thrombolytic allowed us to achieve reperfusion and apply the lessons from earlier research to achieve positive clinical results. The successful conduct of the NINDS tPA stroke study coupled with positive outcomes from companion tPA studies around the world created the specialty of vascular neurology. This was followed by an avalanche of research in imaging, a focus on enhancing reperfusion through thrombectomy, and improving delivery of faster treatment culminating in mobile stroke units. Key Messages: The last half century has seen the birth and evolution of successful acute stroke treatment. More research is needed in developing new drugs and catheters to build on the advances we have already made with reperfusion and also in evolving our systems of care to get more patients treated more quickly in the prehospital setting. The history of stroke treatment over the last 50 years exemplifies that medical "science" is an evolving discipline worth an entire career's dedication. What was impossible 50 years ago is today's standard of care, what we claim as dogma today will be laughed at a decade from now, and what appears currently impossible will be tomorrow's realities.

Analytic Reviews : Potential New Therapies for Acute Ischemic Stroke

Evidence from animal models of acute stroke suggests ischemia may be reversible if blood flow is restored in the first few hours. Studies of human stroke using posi tron emission tomography demonstrate areas with re duced blood flow and relatively preserved metabolism, indicating potentially reversible ischemic brain. Resto ration of blood flow during this reversible phase should improve outcome after stroke.

Many therapeutic strategies for treatment of acute ischemic stroke have been proposed, including increas ing collateral flow, removing vascular obstructions, and interfering with the intracellular cascade of events that lead to neuronal cell death. Hypervolemic hemodilution reduces viscosity and increases cerebral blood flow, and this may hopefully raise blood flow above the critical threshold of irreversible ischemia. Naloxone, calcium channel blockers, and glutamate antagonists alter blood flow and influence intracellular events during and after acute ischemia. Thrombolytic therapy restores blood flow by lysis of obstructing clot. These therapies show promise in preliminary studies, but additional ran domized controlled studies are needed.

Analytic Reviews : Hypervolemic Hemodilution in Acute Ischemic Stroke

In patients with acute ischemic stroke, reversibility of the neurologic deficits depends on the depth and dura tion of the ischemic insult. The rapid elevation of cere bral blood flow (CBF) above ischemic thresholds may minimize or prevent infarction. Reduction of blood vis cosity has been shown to augment CBF and improve cerebral neuronal activity after stroke. Hypervolemic hemodilution decreases hematocrit, increases blood volume, augments cardiac output, and, in randomized clinical trials, improves the long-term outcome in acute ischemic stroke. Similarly, administration of drugs that decrease plasma fibrinogen and increase erythrocyte flexibility reportedly causes a decrease in the incidence of recurrent ischemia after an initial transient ischemic attack. Thus, the pharmacologic manipulation of blood viscosity appears to be effective in managing patients with acute ischemic stroke.

Usefulness of initial diagnostic tests carried out in the emergency department for blunt trauma

Aim

To evaluate the usefulness of the initial diagnostic tests carried out in blunt trauma patients in our emergency department.

Methods

Blunt trauma patients admitted between October 2009 and October 2011 were retrospectively reviewed. A scoring system was developed (0 to 28 points) to differentiate between potential major trauma patients and physiologically stable patients. Patients were classified into three groups: Group I (minor trauma), revised trauma score normal and our score 0-14; Group II (potential major trauma), revised trauma score normal and our score 15-28; Group III (major trauma), revised trauma score low. The proportions of patients with positive initial diagnostic test results (blood tests, X-rays, and computed tomography) were determined in each group.

Results

The study included 1,291 patients (Group I, 1,019; Group II, 85; Group III, 187). Blood tests and X-rays were carried out frequently in all groups, but positive results were infrequent in Group I. Comparisons using Pearson's χ²-test showed significant differences in the proportions of patients with positive blood test, X-ray, and computed tomography results among the three groups. The proportions of patients with positive blood test and chest X-ray results were significantly lower in Group II than in Group III, but there were no significant differences in the proportions of patients with other positive results between these two groups.

Conclusions

In physiologically stable blunt trauma patients, diagnostic tests should be selected only after careful patient evaluation. To achieve this, standardized criteria for the identification of minor trauma patients should be established.

Partial intra-aortic occlusion improves perfusion deficits and infarct size following focal cerebral ischemia

Reperfusion with intravenous tissue plasminogen activator (tPA) has been the goal of therapy for acute ischemic stroke; however, tPA is contraindicated in many patients, has low recanalization rates in major occlusions, and carries a substantial risk of symptomatic intracerebral hemorrhage. In the present study, we hypothesized that partial intra-aortic occlusion of the abdominal aorta would increase salvage of ischemic penumbra and reduce infarct volume after focal embolic stroke in rats. We examined the effects of aortic occlusion on infarct volume, expression and activation of matrix metalloprotease-9, and hemorrhagic transformation with or without treatment with tPA. We then examined the effects of aortic occlusion on perfusion deficits following embolic occlusion. Results showed that partial aortic occlusion significantly reduces brain infarction volume with or without treatment with tPA after focal ischemia, but does not increase risk for hemorrhagic transformation or matrix metalloprotease-9 expression and activation. Partial intra-aortic occlusion also reduces perfusion deficits after focal cerebral ischemia as compared to control. The present study shows that partial intra-aortic occlusion significantly decreases infarction volume and perfusion deficits following ischemic injury in an embolic model of cerebral ischemia. Moreover, combination treatment with tPA and partial intra-aortic occlusion further reduces infarction volume without any increase in hemorrhagic transformation.

Variation in the management of acute physiological parameters after ischaemic stroke: a European perspective

Studies have shown significant variation in stroke case fatality across Europe. These variations suggest the need to explore whether differences in physiological support in acute stroke exist across Europe. Data were collected in four European centres over 6 months. These included clinical status and management of acute physiology (hydration, oxygenation, nutrition, hypertension, hyperglycaemia and temperature in the first week of ischaemic stroke) and survival at 3 months. Differences in acute supportive care between centres were adjusted for case mix. Patients admitted to centres in London (n = 106), Dijon (n = 95), Erlangen (n = 91) and Warsaw (n = 72) were studied. There were significant differences in incontinence, dysphasia, dysphagia, conscious level, pyrexia, hyperglycaemia and comorbidity between centres. After adjusting for case mix, there were significant differences in intravenous fluid use (P = 0.04), enteral feeding (P = 0.003), initiation of new antihypertensive therapy (P = 0.0006) and insulin therapy (P = 0.004) between centres, with the London centre having the lowest uptake of interventions. Three-month case fatality rates varied from 10 to 28%. This pilot study shows significant variation in acute physiological support in acute stroke across four European centres, which remains unexplained by case mix. Further research is required to link variation in acute care with stroke outcome, to identify which interventions appear to be the most effective.

From stroke unit care to stroke care unit

In some stroke units continuous monitoring of blood pressure, electrocardiogram, body temperature, and oxygen saturation has become an integral part of the management of acute stroke. In addition, regular measurements of blood glucose are performed. Stroke units equipped with such monitoring facilities should be named 'stroke care units' by analogy with coronary care units. The goal of a stroke care unit is early detection and rapid correction of extracranial factors which may aggravate cerebral damage in ischemic brain, including hypoxia, hyperglycemia, hypotension, cardiac arrhythmias, and elevated body temperature.

Ischemic stroke

Acute ischemic stroke is a neurological emergency that requires ultra-rapid intervention. Stroke teams and stroke protocols can be devised to expediate evaluation and treatment. In carefully selected patients, thrombolytic therapy offers a significant benefit but must be initialized within 3 hours of stroke onset. Emerging alternative strategies for reperfusion and neuroprotection must also be initiated during the hyperacute period. The role of more traditional therapies, such as antiplatelet agents and anticoagulants, have been better defined through several recent major clinical trials.

Acute stroke

Disruption of cerebral blood flow may influence brain energy metabolism to produce reversible or irreversible neurologic deficits. The emergency physician is in a unique position to provide timely treatment during the first few hours of an acute stroke. He or she must be facile with unique pharmacologic and non-pharmacologic treatment designed for the stroke patient concerning ventilation, blood pressure, and circulation.

Current emergency department management of stroke in Houston, Texas

BACKGROUND AND PURPOSE

This study describes emergency department (ED) management of stroke in Houston, Tex, in 1992 to identify delays and deficiencies in recognition and management of stroke patients in various hospital subtypes and to quantitate the impact of a rapid response stroke team.

METHODS

ED logs of eight hospitals were retrospectively screened, and 112 patients with suspected acute stroke onset within 6 hours were identified. EDs were divided into four groups based on hospital size (175 to 979 beds), acuity, number of stroke admissions (50/y to 210/y), and availability of neurological consultations. The intervals from stroke onset to triage, examination by a physician, neurological evaluation, computed tomography (CT) and other tests, vital signs, and treatments were recorded.

RESULTS

The average time from stroke to ED arrival was 115 minutes, and times from ED arrival to examination by a physician and CT scan were 28 and 100 minutes, respectively, with little variability among hospital groups except that the public hospital was slower. Neurological examinations were poorly documented in community and public hospitals. The presence of a stroke team shortened the time to examination by a physician and to CT by 13 and 63 minutes, respectively, and increased the number of patients admitted to the intensive care unit. Blood pressure was excessively lowered in 31% of hypertensive patients, and hypotonic dextrose intravenous fluids were given to 69% of all patients.

CONCLUSIONS

Transport, initial evaluation, and ED care of acute stroke patients are currently slow and often inexpert in all types of hospitals. A stroke team can speed initial ED management.

Role of hypervolemic hemodilution in focal cerebral ischemia of rats

This study was designed to better define a protocol for hypervolemic hemodilution in acute cerebral ischemia and investigate the mechanism of action of this therapy. Anesthetized rats (n = 40) were subjected to 6 h of middle cerebral artery (MCA) occlusion. At 45 min after MCA occlusion, each rat received one of the following treatment modalities: (1) control, (2) isovolemic hemodilution, (3) hypervolemic nonhemodilution (whole blood), (4) hypervolemic hemodilution (normal saline), and (5) hypervolemic hemodilution (hetastarch). Local cerebral blood flow (CBF) was determined with hydrogen clearance technique, and cardiac output was assessed by measuring the descending aorta blood flow (DAF). Infarction volume was estimated by 2,3,5-triphenyltetrazolium chloride staining method. Hetastarch infusion increased both DAF and local CBF more than the other treatments, by 98% and by 89%, respectively. Hetastarch also reduced infarction volume the most to 71 +/- 19 mm3 (p < 0.01 versus control 117 +/- 32 mm3). A significant correlation between percent (%) changes in local CBF and % changes in DAF existed in ischemic brain regions, and the hetastarch infusion improved local CBF more prominently in profoundly ischemic regions in contrast to isovolemic hemodilution. These data demonstrated the superiority of hypervolemic hemodilution with hetastarch as compared to other similar treatment modalities for acute cerebral ischemia, and indicate that cardiac output augmentation may be more responsible than decreased blood viscosity for the beneficial effect of hypervolemic hemodilution on local CBF in profoundly ischemic regions, as such ischemic brain tissue can severely lose its regulatory control of CBF to alterations in cardiac output.

Evaluation of long-term outcome and safety after hemodilution therapy in acute ischemic stroke

BACKGROUND AND PURPOSE

In a previous single-center, randomized controlled trial including 102 patients treated in a stroke unit, we showed that rapid, modest hemodilution improved short-term clinical outcome in ischemic stroke patients. I now evaluate the long-term outcome and potential risks of this combined venesection/dextran 40 therapy in the same 52 treated and 50 control patients.

METHODS

Mortality, need for institutional care, and recurrent strokes were registered during 1 year following inclusion in the trial, and a final evaluation of functional outcome was performed at 12 months after the stroke. Cerebrospinal fluid was analyzed for protein content and hemorrhagic admixture at two occasions during the acute phase.

RESULTS

Thirty-six hemodiluted and 30 control patients survived the first year following the stroke (difference not significant). One year after the stroke, persistent neurological deficits were less frequent among the hemodiluted patients and a larger proportion of hemodiluted survivors was independent in walking (92% versus 73%, p less than 0.05). Two hemodiluted patients (6%) and nine control patients (30%) were totally dependent in the activities of daily living (p less than 0.05). Three hemodiluted patients (8%) and eight control patients (27%) remained hospitalized 1 year after the stroke (p less than 0.05). With the possible exception of patients with a medical history of congestive heart failure, subset analyses revealed a tendency toward improved outcome for hemodiluted patients in all clinically important subgroups compared with the controls. When analyzing cerebrospinal fluid, signs of blood-brain barrier breakdown and hemorrhagic admixture to the cerebrospinal fluid during the acute phase were less frequent in the hemodiluted subjects.

CONCLUSIONS

These results suggest that, when applied in a stroke unit, the combination of venesection and dextran 40 administration is a clinically safe, therapeutic regimen in the treatment of acute cerebral infarction that improves long-term clinical outcome.

The no-reflow phenomenon is a post-mortem artifact

Post-ischemic reperfusion impairment, ("no-reflow phenomenon"), was studied in rats subjected to 8-30 minutes of global brain ischemia. During ischemia, rapid and complete loss of cerebral blood flow, EEG and 31P-high energy phosphates (ATP/PCr) was observed. Brain intravascular perfusion defects were examined by injecting carbon black intravenously in a group of rats with stable cardiopulmonary function and in another group subjected to rapid thoracotomy and intraarterial infusion of the carbon marker. Results indicate that global brain ischemic or non-ischemic control rats given intraarterial carbon black after thoracotomy had varying degrees of vessel filling defects in brain resulting in "pale tissue areas" suggestive of impaired perfusion (no-reflow). All rats given carbon black intravenously whether global brain ischemic or not, showed normal cerebrovascular filling of the carbon black and absence of "pale tissue areas". In addition, post-ischemic cerebral reperfusion following 8-30 minutes global brain ischemia can reverse neuroelectric, energy metabolite and cerebral blood flow loss in rats whose cardiopulmonary function is not compromised. These findings indicate that the "no-reflow phenomenon" is an agonal or post-mortem artifact observed in the presence of cardiopulmonary failure.

Beneficial effects of isovolemic hemodilution using a perfluorocarbon emulsion in a stroke model

In a clinically applicable cat stroke model, 16 purpose-bred adult animals were used to evaluate the beneficial effects of two treatment regimens: isovolemic hemodilution with either a perfluorocarbon emulsion or dextran 40 (a glucose polymer). Animals that received these treatment regimens were then compared with a control group of untreated animals. Focal cerebral infarctions were produced by transorbital ligation of the left middle cerebral artery. The randomly allocated treatment arms of the study were instituted 3 hours after ligation of the middle cerebral artery, thereby simulating a human clinical situation. In vivo mitochondrial metabolic activity of the peri-infarct cerebral tissue was continually assessed by means of a multiwavelength near-infrared spectrophotometer. This allowed measurement of cellular oxygenation at the cytochrome aa3 level, the terminal member of the cytochrome chain. Sequential proton-based magnetic resonance imaging was used to measure intracerebral water in vivo. Cardiac output, oxygen consumption/delivery, chemical, histologic, and rheologic parameters were also assessed. The data collected were analyzed by group means and standard statistical analyses, which revealed that the group treated with the perfluorocarbon emulsion had both less brain edema in the early post-infarct period (p less than 0.05), as well as a higher level of oxidation of cytochrome aa3 (p less than or equal to 0.025). This evidence supports the premise that isovolemic hemodilution with an oxygen-carrying hemodiluent may be beneficial in the treatment of ischemic strokes.

Adjusted hypervolemic hemodilution in acute ischemic stroke

We prospectively randomized 47 patients with acute ischemic stroke of the middle cerebral artery of less than 24 hours' duration to either adjusted hypervolemic hemodilution or control treatment and followed them up for 90 days. Rapid hemodilution to a target hematocrit of 30-35% as monitored with bedside determinations was achieved by using infusions of dextran 40, venesections, and infusions of additional crystalloid solution when necessary. There was no difference in the death rate between the two treatment groups. Of these 47 patients, 37 (19 in the hemodilution group and 18 in the control group) could be followed up for the entire study period of 3 months. The relative improvement in neurologic function from day 1 to days 8, 21, and 90 was significantly better in the hemodilution group than in the control group. In accordance, special tests for fine motor control of the paretic arm disclosed better performance in the hemodilution group. The frequency of patients with severe disability was significantly lower in the hemodilution group on days 8 and 21. Plasma viscosity (measured in 11 patients) was not affected by infusions of dextran 40. Vigorous hypervolemic hemodilution in patients with acute ischemic stroke is well tolerated and improves early neurologic outcome with an effect lasting at least 3 months.

Volume therapy in orthostatic transient ischemic attacks

We report the case of an 83-year-old man with recurrent orthostatic transient ischemic attacks despite anticoagulation and crystalloid therapy. An initial cerebral angiogram revealed a nearly occluded right carotid artery with a string sign. Following aggressive volume expansion with albumin, the patient became asymptomatic. A second angiogram demonstrated the resolution of the carotid string sign and unmasked a high-grade, very tight, surgically approachable stenosis. The role of a high intravascular volume status is discussed.

Hemodilution increases cerebral blood flow in acute ischemic stroke

We measured cerebral blood flow in 10 consecutive, but selected, patients with acute ischemic stroke (less than 48 hours after onset) before and after hemodilution. Cerebral blood flow was measured by xenon-133 inhalation and emission tomography, and only patients with focal hypoperfusion in clinically relevant areas were included. Hemodilution was done according to the hematocrit level: for a hematocrit greater than or equal to 42%, 500 ml whole blood was drawn and replaced by the same volume of dextran 40; for a hematocrit between 37% and 42%, only 250 ml whole blood was drawn and replaced by 500 cc of dextran 40. Mean hematocrit was reduced by 16%, from 46 +/- 5% (SD) to 39 +/- 5% (SD) (p less than 0.001). Cerebral blood flow increased in both hemispheres by an average of 20.9% (p less than 0.001). Regional cerebral blood flow increased in the ischemic areas in all cases, on an average of 21.4 +/- 12.0% (SD) (p less than 0.001). In three patients, a significant redistribution of flow in favor of the hypoperfused areas was observed, and in six patients, the fractional cerebral blood flow increase in the hypoperfused areas was of the same magnitude as in the remainder of the brain. In the last patient, cerebral blood flow increased relatively less in the ischemic areas. Our findings show that cerebral blood flow increases in the ischemic areas after hemodilution therapy in stroke patients. The marked regional cerebral blood flow increase seen in some patients could imply an improved oxygen delivery to the ischemic tissue.

Transcranial Doppler measurements of the middle cerebral artery. Effect of hematocrit

We evaluated the effects of hematocrit on blood velocity in the middle cerebral artery measured by transcranial Doppler ultrasonography in 45 patients. Hematocrits ranged from 16% to 46%, and systolic blood velocities ranged from 70 to 190 (mean 40 to 140) cm/sec. Decreases in hematocrit correlated with increases in blood velocity in the middle cerebral artery. These results suggest that transcranial Doppler measurements made in the presence of anemia may need correction.

Determination of whole blood apparent viscosity: experience with a new hemorheologic technique

A new experimental technique of determining apparent blood viscosity at low rates of shear using a porous bed viscometer (PBV) was evaluated in a study of 213 blood samples from 43 mongrel dogs. Viscosity was measured over a wide range of hematocrit (Hct), 6.5-51%, and plasma fibrinogen (Fib), 11-597 mg%, levels significantly altered (P less than 0.0005) by isovolemic hemodilution. Viscosity was highly correlated with Hct and Fib (r = 0.89), which confirmed the results of previous investigations. An important finding was the ability of the PBV to detect the non-Newtonian behavior of whole blood that occurs under low shear conditions at higher Hct levels. In a subgroup of 10 animals, viscosity was also measured by a precision cone and plate viscometer (CPV) at various shear rates. Although the PBV and CPV measurements showed excellent correlation (r = 0.92), a marked nonlinear deviation of the plotted data from the regression of Hct vs viscosity measured by the PBV at Hct levels greater than or equal to 30% was noted which could not be identified by the CPV. The PBV technique affords valid measurements of the apparent viscosity of normal canine blood. Moreover, the device is apparently sensitive to the anomalous rheologic properties of whole blood attributable to shear-dependent changes in red blood cell aggregation that can become physiologically significant in low-flow states.

Isovolemic hemodilution in experimental focal cerebral ischemia. Part 2: Effects on regional cerebral blood flow and size of infarction

Seventy-six splenectomized dogs were entered in a study of the value and effects of isovolemic hemodilution. Of these, seven were not included in the analysis because of technical errors. Of the remaining 69 dogs, 35 were treated with hemodilution; 28 were subjected to a 6-hour period of temporary occlusion of the distal internal carotid artery and the proximal middle cerebral artery, and seven underwent a sham operation only, with arterial manipulation but no occlusion. The other 34 dogs were not subjected to hemodilution; 26 of these underwent temporary arterial occlusion and eight had a sham operation only. In each group the animals were about equally divided into 1) an acute protocol with regional cerebral blood flow measurements by a radioactive microsphere technique and sacrifice at the end of the acute experiment, and 2) a chronic protocol with survival for 1 week to permit daily neurological assessment and final histopathological examination but without blood flow measurements. The general experimental protocol, the hemodynamic and rheological measurements, and the changes in intracranial pressure are described in Part 1 of this report. In the animals with arterial occlusion, blood flow decreased significantly in the territory of the ischemic middle cerebral artery. This decrease was partially reversed by hemodilution in the animals so treated. When the changes in blood flow before and after hemodilution in treated animals are compared with the changes at equivalent times in animals without hemodilution, the increases in flow in the gray matter of the ischemic hemisphere brought about by hemodilution are statistically significant. The neurological condition of the animals in the chronic protocol (sacrificed 1 week after occlusion) with hemodilution, as evaluated by daily neurological assessment, was significantly better than that of the control animals. In the animals sacrificed acutely (8 hours after arterial occlusion), the volume of infarction as estimated by the tetrazolium chloride histochemical method was 7.36% of the total hemispheric volume in the control animals and 1.09% in the hemodiluted animals, showing a statistically significant difference (p less than 0.005). In the chronic animals these values were 9.84% and 1.26%, respectively (p less than 0.005), as calculated by fluorescein staining. By histopathological examination the volume of infarction in the chronic animals was calculated as 10.92% in the control animals and 1.20% in the hemodiluted animals (p less than 0.005).(ABSTRACT TRUNCATED AT 400 WORDS)

Isovolemic hemodilution in experimental focal cerebral ischemia. Part 1: Effects on hemodynamics, hemorheology, and intracranial pressure

A total of 76 splenectomized dogs were entered in a study of the value and effects of isovolemic hemodilution. Of these, seven were not included in the analysis because of technical errors. Of the remaining 69 dogs, 35 were treated with hemodilution; 28 were subjected to a 6-hour period of temporary occlusion of the distal internal carotid artery and the proximal middle cerebral artery, and seven underwent a sham operation only, with arterial manipulation but no occlusion. The other 34 dogs were not subjected to hemodilution; 26 of these underwent temporary arterial occlusion and eight had a sham operation only. In each group the animals were about equally divided into 1) an acute protocol with regional cerebral blood flow measurements by a radioactive microsphere technique and sacrifice at the end of the acute experiment, and 2) a chronic protocol with survival for 1 week to permit daily neurological assessment and final histopathological examination but without blood flow measurements. Isovolemic hemodilution was performed about 1 hour after the arterial occlusion or sham operation and was accomplished by phlebotomy and infusions of low molecular weight dextran to bring the hematocrit to a level of 30% to 32%. This treatment resulted in a very significant reduction in viscosity and fibrinogen levels. The decrease in hematocrit lasted throughout the week in the animals in the chronic protocol. The decrease in viscosity correlated almost linearly with the decrease in hematocrit. There was a slight decrease in systemic arterial pressure with hemodilution but there were no significant changes in central venous pressure or in pulmonary arterial or wedge pressure. There was a slight decrease in cardiac index in both the hemodilution and control groups, which may have been due to the effects of barbiturate anesthesia. There was a slight increase in the measured blood volume in both groups, which was probably artifactual and related to the method of calculation. Intracranial pressure increased significantly with time in all animals subjected to arterial occlusion, but this increase was less severe in the hemodilution group. There was no significant change in intracranial pressure in sham-operated animals, whether hemodiluted or not. The results of cerebral blood flow measurements, assessment of neurological conditions, and measurement of infarct size are given in Part 2 of this report.

Brain resuscitation and protection

No drug that is used for brain protection after global brain ischaemia as a result of cardiac arrest has been shown to be of benefit. Barbiturate agents have been proved not to be beneficial whereas studies of calcium-channel blocking drugs are inconclusive. Hypothermia, haemodilution and mechanical hyperventilation are not of proven benefit. Immediate defibrillation with rapid restoration of blood pressure is the best method to improve the neurological outcome after a cardiac arrest. After severe head injury, prompt emergency care to restore ventilation, oxygenation and blood pressure improves the neurological outcome. The early evacuation of extracerebral intracranial haematomas also improves the outcome. Corticosteroid therapy does not improve the outcome. The monitoring of intracranial pressure and the control of increased intracranial pressure by hyperventilation, cerebrospinal-fluid drainage and mannitol, frusemide and barbiturate therapy appear to improve the outcome after a severe head injury, although this has not been proved by randomized controlled studies.

Hemorheologic factors in the postacute phase of ischemic stroke

Clinical and hemorheologic data were recorded in a homogeneous group of 72 patients (age range sixty-one to seventy years), suffering from ischemic stroke with an onset of less than eight hours, confirmed clinically and by computerized tomography. A quantitative neurologic analysis and the following hemorheologic parameters were monitored for twenty weeks following the acute episode: fibrinogen, total proteins, albumin, hematocrit, leukocyte and platelet counts, whole blood filterability (WBF), red blood cell deformability (RBCD), and blood plasma, and serum viscosity. The results show a significant decrease in hematocrit values parallel to the clinical neurologic improvement and a significant increase in RBCD in the patients with the better clinical recovery. These data confirm the role of hemorheologic parameters in the clinical follow-up of cerebrovascular disorders.

Multicenter trial of hemodilution in acute ischemic stroke. Results of subgroup analyses. Scandinavian Stroke Study Group

In a multicenter trial, 183 patients with acute ischemic stroke of less than 48 hours' duration and hematocrits of 38-50% were randomized to standardized hemodilution treatment (venesection and dextran 40 administration) and 190 to a control group. We have previously reported that there were no beneficial effects of hemodilution in the total patient population. In this report, the case fatality rates and neurologic outcome in survivors (3 months' follow-up) in subsets of patients have been analyzed. The patients were subgrouped by sex, age, medical history, smoking habits, delay from the onset of symptoms to the start of treatment, hematocrit at entry, venesection volume, neurologic score at entry into the study, blood pressure changes in the acute phase, presence of atrial fibrillation, location of brain lesion by computed tomography, type of diagnostic procedures, and hospital setting. No subset in which hemodilution reduced mortality or improved neurologic outcome could be identified. Case fatality rate was apparently higher in hemodiluted patients with infarction affecting deep brain structures than in control patients with such lesions. By simple clinical criteria, we have been unable to define subsets of stroke patients who benefit from the present standardized regimen of moderate hemodilution. The sample sizes are, however, too small to refute the possibility that a modest clinical effect of hemodilution may be present in some patients with stroke.

Multicenter trial of hemodilution in acute ischemic stroke. I. Results in the total patient population. Scandinavian Stroke Study Group

Hemodilution by the combination of venesection and dextran 40 administration has previously been reported to enhance neurologic recovery in the acute phase of ischemic stroke. To study this therapeutic principle in its "natural habitat," a stratified and randomized multicenter trial involving 15 large and small hospitals was performed. Patients with acute ischemic stroke of less than 48 hours' duration and with hematocrits of 38-50% on admission were randomized to a hemodilution (183 patients, mean age 72.0 years) or a control group (190 patients, mean age 71.6 years). The two groups did not differ in sex distribution or medical history. Hematocrit, blood pressure, and neurologic score were closely similar at entry. By graded venesection (250-1000 ml) during the first 2 days and dextran 40 infusions (500 ml daily) during 5 days, the mean hematocrit was reduced from 44.2 to 37.1%. Three-month survival expressed as life table product was 0.84 in hemodilution and 0.88 in control patients. In survivors, neurologic score and activities of daily living performance during 3 months of follow-up were not improved by hemodilution. Length of stay in an acute-care hospital and the need for long-term institutional care was not reduced among patients in the hemodilution group. Major cardiovascular events occurred somewhat more often and there was an apparent increase in mortality during the first few days of hemodilution therapy. However, the differences were not significant. We conclude that the present standardized treatment with moderate hemodilution has no overall beneficial effects in general patients with acute ischemic stroke.

Plasticity of the brain in respect of functional restoration after subarachnoid haemorrhage

Subarachnoid haemorrhage caused by aneurysmal rupture constitutes a great impact on the brain and on the intracranial content as a whole, with emphasis on the subarachnoid spaces and arteries. The rupture is followed by a wide range of pathological alterations in the neural function and an outcome varying from neglected signs subsiding in a few days to immediate death. Two main factors seem to influence the different events after subarachnoid bleeding. One is the rupture itself which can be extremely variable in severity and in its immediate as well as late consequences. The other is the ability of all parts of the intracranial content to recover. In order to understand either of both the other should also be looked at and both have to be dealt with if we are to treat patients with an aneurysmal rupture properly. For this reason a grading of rupture will be given in respect of some characteristic events in the light of neural restoration. Clearing of CSF, resolution of brain oedema, restoration of impaired CBF, absorption of cisternal and parenchymal haematoma are all of importance. The majority of lesions which developed after the rupture are not fatal or irreversible and even the neural tissue destroyed by the impact or late ischaemia can be functionally replaced. Possible methods of treatment for attaining this functional restoration will be discussed.

Haemodilution therapy in ischaemic stroke: plasma concentrations and plasma viscosity during long-term infusion of dextran 40 or hydroxyethyl starch 200/0.5

In 21 patients with ischaemic strokes we have monitored plasma viscosity, total plasma concentration, numeric average molecular weight (Mn), and weight average molecular weight (Mw) of Dextran 40 (dextran) and hydroxyethylstarch 200/0.5 (HES) during 10 days of treatment (days 1-4, 2 X 500 ml; days 5-10, 1 X 500 ml). Plasma concentrations of dextran increased during the first 4 days (8.3 mg X ml-1 on the first day to 18.0 mg X ml-1 on the fifth day), reached an apparent steady state of 17.2 mg X ml-1 during the next 6 days, and declined subsequently with a half-time (t1/2) of 4.03 days. After ten days treatment Mn and Mw were shifted towards higher values. Plasma viscosity increased from 1.26 mPas to 1.69 mPas on Day 10 (p less than 0.01) and was linearly correlated with the total plasma concentration of dextran (p less than 0.001; r = 0.88). Total plasma concentrations of HES averaged 11.7 mg X ml-1 on Day 1 and 12.4 mg X ml-1 on Day 5. The molecular weight distribution did not change during the infusions but decreased in comparison with the administered solution. Plasma viscosity fell from 1.40 mPas to 1.30 mPas at Day 10 (p less than 0.05) and was not related to the concentration of HES. The haemodiluting effect, as indicated by a decrease of the haematocrit, was 22% and 16.8% for dextran and HES respectively. These data suggest several advantages of HES compared with dextran in haemodilution therapy of ischaemic stroke.

Cerebral protection

Cerebral protection from an ischemic/hypoxic insult implies that tissue injury can be controlled or even prevented by certain therapeutic maneuvers. For example, physiological thresholds may be altered so that tissue vulnerability to the insult is reduced, or the intensity of an insult may be blunted by enhancing brain homeostasis. Such a therapeutic maneuver is carotid endarterectomy to improve blood flow in the disordered hemisphere. Alternatively, drugs with protective properties can be used before or even after the insult to "stabilize" injured tissue and prevent the harmful secondary effects that often follow. Various past and present approaches to cerebral protection employing physiological, pharmacological, and surgical intervention are reviewed. The mechanisms by which each allegedly protects the brain from ischemia and hypoxia are discussed briefly. Promising, but not always successful, approaches used in the past have pointed the way for new and more rational therapies. Truly effective protection of the brain from ischemia and hypoxia depends directly upon our capability to explore basic mechanisms of injury and our willingness to measure accurately and objectively the outcome of newly developed protective measures.

Effect of the acute phase reaction on blood viscosity after infrainguinal arterial bypass

A new method of determining apparent blood viscosity at low shear rates using a porous bed viscometer has been validated in an experimental study of canine blood altered by isovolemic hemodilution. The data confirm the ability of the technique to detect the non-Newtonian behavior of blood at higher hematocrit and fibrinogen values. The technique was then employed in a limited clinical study of nine patients undergoing infrainguinal vascular reconstruction to evaluate the effect of operation and the associated increase in serum fibrinogen levels, resulting from the acute phase reaction, on blood viscosity. Although there was a substantial change in serum glycoprotein levels, the concurrent relative decrease in red cell mass after operation resulted in a decrease in whole blood viscosity. These findings support the beneficial effect of moderate hemodilution as a means of compensating for the potentially detrimental effects of the acute phase reaction on blood rheology.

Cerebral borderzone infarcts after phlebotomy

We describe a 68-year-old patient with cerebral ischaemia who underwent a phlebotomy to lower an elevated haematocrit (0.61 l/l. The procedure was complicated by the development of a total hemiplegia after two hours. CT scanning showed two borderzone infarcts. We conclude that the plasma volume of patients with cerebral ischaemia and a high haematocrit may be contracted to such an extent that venesection is hazardous. The most appropriate treatment in these patients is expansion of the plasma volume.