[Treatment of acute cerebral ischaemia with low-molecular dextran: results of a retrospective study (author's transl)]

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.

Haemodilution for acute ischaemic stroke

BACKGROUND

Ischaemic stroke interrupts the flow of blood to part of the brain. Haemodilution is thought to improve the flow of blood to the affected areas of the brain and thus reduce infarct size.

OBJECTIVES

To assess the effects of haemodilution in acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (Issue 1, 2014), MEDLINE (January 2008 to October 2013) and EMBASE (January 2008 to October 2013). We also searched trials registers, scanned reference lists and contacted authors. For the previous version of the review, the authors contacted manufacturers and investigators in the field.

SELECTION CRITERIA

Randomised trials of haemodilution treatment in people with acute ischaemic stroke. We included only trials in which treatment was started within 72 hours of stroke onset.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trial quality and one review author extracted the data.

MAIN RESULTS

We included 21 trials involving 4174 participants. Nine trials used a combination of venesection and plasma volume expander. Twelve trials used plasma volume expander alone. The plasma volume expander was plasma alone in one trial, dextran 40 in 12 trials, hydroxyethyl starch (HES) in five trials and albumin in three trials. Two trials tested haemodilution in combination with another therapy. Evaluation was blinded in 14 trials. Five trials probably included some participants with intracerebral haemorrhage. Haemodilution did not significantly reduce deaths within the first four weeks (risk ratio (RR) 1.10; 95% confidence interval (CI) 0.90 to 1.34). Similarly, haemodilution did not influence deaths within three to six months (RR 1.05; 95% CI 0.93 to 1.20), or death and dependency or institutionalisation (RR 0.96; 95% CI 0.85 to 1.07). The results were similar in confounded and unconfounded trials, and in trials of isovolaemic and hypervolaemic haemodilution. No statistically significant benefits were documented for any particular type of haemodiluting agents, but the statistical power to detect effects of HES was weak. Six trials reported venous thromboembolic events. There was a tendency towards reduction in deep venous thrombosis or pulmonary embolism or both at three to six months' follow-up (RR 0.68; 95% CI 0.37 to 1.24). There was no statistically significant increased risk of serious cardiac events among haemodiluted participants.

AUTHORS' CONCLUSIONS

The overall results of this review showed no clear evidence of benefit of haemodilution therapy for acute ischaemic stroke.These results are compatible with no persuasive beneficial evidence of haemodilution therapy for acute ischaemic stroke. This therapy has not been proven to improve survival or functional outcome.

Haemodilution for acute ischaemic stroke

BACKGROUND

Ischaemic stroke interrupts the flow of blood to part of the brain. Haemodilution is thought to improve the flow of blood to the affected areas of the brain.

OBJECTIVES

The objective of this review was to assess the effects of haemodilution in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register, Medline and conference abstracts. We contacted manufactures and investigators in the field.

SELECTION CRITERIA

Randomised trials of haemodilution treatment in people with acute ischaemic stroke. Only trials where treatment was started within 72 hours of stroke onset were included.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and independently extracted the data.

MAIN RESULTS

Sixteen trials were included. A combination of venesection and plasma volume expander was used in eight trials. Eight trials used plasma volume expander alone. The plasma volume expander was dextran 40 in 11 trials, hydroxyethyl starch in four trials and albumin in one trial. Two trials tested haemodilution in combination with another therapy. Evaluation was blinded in 11 trials. Five trials probably included some patients with intracerebral haemorrhage. Haemodilution did not significantly reduce deaths within seven to 28 days (odds ratio 1.12, 95% confidence interval 0.88 to 1.43). Similarly, haemodilution did not influence deaths within three to six months (odds ratio 1.02, 95% confidence interval 0.85 to 1.23), or death and dependency or institutionalisation (odds ratio 1.01, 95% confidence interval 0.86 to 1.19). The results were similar in confounded and unconfounded trials, in trials of isovolaemic and hypervolaemic haemodilution, and in trials using different types of hemodiluting agents. Six trials reported venous thromboembolic events. There was a tendency towards reduction in deep venous thrombosis and/or pulmonary embolism at three to six months follow-up (odds ratio 0.59, 95% confidence interval 0.33 to 1.06).

REVIEWER'S CONCLUSIONS

The overall results of this review are compatible both with a modest benefit and a moderate harm of haemodilution therapy for acute ischaemic stroke. As used in the randomised trials, this therapy has not been proven to improve survival or functional outcome.

Incidence of acute oligoanuric renal failure in dextran 40 treated patients with acute ischemic stroke stage III or IV

Two hundred eleven patients with acute ischemic stroke, stage III or IV, received daily intravenous infusion of 500-1000 mL low-molecular dextran (dextran 40) over a period of 4 days. In 10 cases (4.7%) acute renal failure, associated with dextran infusion, could be observed; oligoanuria occurred after a mean time of 4 (3-6) days. The incidence of dextran-induced acute renal failure was significantly higher in patients with a preexisting reduction of glomerular filtration rate below 30 mL/min/1.73 m2 (p < 0.005). Five of the patients (50%) with acute renal failure died within 4-12 days after the hemodilution therapy with dextran 40; this high lethality was due to nonrenal complications.

Why do all drugs work in animals but none in stroke patients? 1. Drugs promoting cerebral blood flow

Medical treatments which presumably alter cerebral blood flow (CBF) have been quite unimpressive in their effect on stroke outcome. In considering experimental and clinical data from the use of haemodilution and of the antiplatelet agent prostacyclin in focal cerebral ischaemia, and the current work with fibrinolytic agents in acute stroke, several lessons are apparent. Often agents hypothesized to affect CBF receive an underserved reputation based on sparse experimental evidence. Significant even unsuspected differences between species limit application to the clinical setting. Limitations of CBF measurements in experimental models and in humans raise questions about apparent responses to those agents. The failure to confirm a relationship between CBF enhancement and reduction in infarct development experimentally has plagued these approaches. The need for early application of agents which may modulate CBF during cerebral ischaemia is critical. Attention to these general issues and careful application of appropriate models are necessary so that a potentially useful therapeutic intervention is not overlooked.

Induced hypertension as an approach to treating acute cerebrovascular ischaemia: possibilities and limitations

As, after an stroke, the autoregulation of the cerebral vessels in the ischaemic region is disturbed to a high degree, it is, on principle, possible to improve the blood flow particularly in the zone surrounding the infarct (penumbra) by raising the systemic blood pressure. During a basic treatment with low-molecular dextrans (infukoll M40), 37 patients with an acute ischaemic cerebral stroke multiply underwent elevations in blood pressure up to systolic values of about 210 to 220 mmHg. A comparison with a control group (n = 44) who were treated with low-molecular dextrans revealed no differences in lethality on the 21st day after the stroke. However, a very good acute effect in terms of a short-term improvement was remarkable a result that is noteworthy also in future.

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)

Relationship between blood viscosity and cerebral ischemia after surgical treatment of ruptured intracranial aneurysms

To determine the role of blood viscosity after surgical treatment of ruptured intracranial aneurysms, the relationship between blood viscosity and clinical condition was examined in 17 patients. A total of 213 blood samples were analyzed. An inverse correlation was found between blood viscosity and level of consciousness; in addition, blood viscosity was higher when focal neurologic deficit was observed. Hematocrit was similarly related to clinical condition, although the correlations observed were less strong. Postoperative plasma viscosity was higher in patients with focal neurologic deficit. Regular blood viscosity measurements are of value in patients at risk for developing cerebral ischemia.

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

Hemodynamic data were obtained in 9 patients (mean age 65 yrs) with carotid territory cerebral infarct within the preceding 24 hours (mean 14 +/- 8) as part of a pilot study testing the feasibility and safety of hypervolemic hemodilution. Pulmonary arterial catheters (PACs) were placed without complication in all patients, and after baseline measurements were obtained, up to 1500 cc of 6% hetastarch in 0.9% sodium chloride was administered the first day and up to 1000 cc per day the second and third days. Pulmonary wedge pressure (PWP) rose from 6.3 +/- 3.5 to 14.4 +/- 3.4 mm Hg (p less than 0.001) without development of congestive heart failure in any patient. This was accompanied by a drop in hematocrit (Hct) from 40.3 +/- 3.4 to 32.9 +/- 2.0 (p less than 0.001) and rise in cardiac output (CO) from 4.3 +/- 1.0 to 5.3 +/- 0.6 (p less than 0.05). Phlebotomy of 250 cc was performed in 2 patients and 500 cc in one in order to reduce Hct to desired levels. The volume of fluid needed to raise PWP to 15 was unpredictable (2361 +/- 1106 cc) and therefore PACs were necessary to monitor the rate and volume of fluid administration. The data show that PWP is sufficiently low and Hct sufficiently high following stroke in most patients that hemodilution by volume expansion with phlebotomy added if necessary can be undertaken safely with appropriate monitoring of hemodynamic function, and that this therapy results in optimal reduction of Hct and increased CO without risk of hypotension.

Fibrinogen, blood viscosity, and cerebral ischemia

This study examines the effect of fibrinogen and consequent blood viscosity reduction on cerebral blood flow and cellular injury following severe cerebral ischemia for 30 minutes in 78 Wistar rats. In half of these rats 10 to 15 cc's of blood was removed and replaced with a mixture of 5% albumin and autologous red blood cells maintaining a constant hematocrit but resulting in a 30% decrease in fibrinogen and corresponding reduction in viscosity. Fibrinogen reduction in a slight increase in baseline CBF and the elimination of post-ischemic hyperemia at 24 hours. Both study and control animals showed a similar decrease in CBF at 30 minutes and 2 hours. There was no significant difference in the severity of ischemic cellular change between the fibrinogen reduction group and controls, although there was a significant inverse relationship between the amount of viscosity change and severity of cellular injury within the treatment group. Fibrinogen reduction alone cannot significantly ameliorate ischemic injury in this model. Viscosity reduction therapy should include reduction of hematocrit and alteration of red cell deformability.

Failure of intravascular volume expansion without hemodilution to elevate cortical blood flow in region of experimental focal ischemia

Cerebrovascular and cardiac alterations evoked by intravascular volume expansion with whole blood, a popular adjunct in the clinical prevention or therapy of the focal ischemic deficits of cerebral vasospasm and acute stroke, were studied in splenectomized dogs. Clipping of the right distal internal carotid and proximal middle cerebral arteries in eight dogs reduced regional cortical blood flow (rCoBF) by 49% to 58% without altering cardiac output (CO), and produced about 10% hemispheric infarction. Eight dogs underwent similar cerebral arterial occlusion and eight dogs underwent arterial manipulation without clipping. Both latter groups received two autologous whole blood infusions within 2 hours, each equal to 20% of the respective dog's total blood volume. Despite significant CO elevations after the infusions, rCoBF in the middle cerebral arterial territory did not rise. These whole-blood infusions did not significantly alter mean arterial blood pressure, hematocrit, intracranial pressure, or, in dogs with clipped cerebral arteries, the relative size of infarction. These data suggest that nondilutional hypervolemia neither elevates collateral perfusion to ischemic regions of the brain nor reduces infarction. In addition, elevations in CO do not appear to augment blood flow in either ischemic or normal brain.

The effect of pentoxifylline ('Trental') on cerebral blood flow: a double-blind study

A double-blind, placebo controlled crossover study was carried out in 20 geriatric patients with cerebrovascular insufficiency ot asses the effect of pentoxifylline on cerebral blood flow. Using 99m Tc cerebral scinitigraphy and a gamma comera/computer system, the pattern of blood flow in 5 brain areas was manitored after a single intravenous infusion of 200 mg pentoxifylline (10 ml) and after 10 ml saline solution. The results showed that, with the exception of one brain area, there was a statistically significant increase both in regional and hemispheric cerebral blood flow after pentoxifylline. It is of particular interst that global hemispheric blood flow, which gives an indication of total blood supply to the brain, showed approximately the same percentage increase on both sides with pentoxifylline.