Vasospasmogenic substance produced following subarachnoid haemorrhage, and its fate

Therapeutic potential of berries in age-related neurological disorders

Aging significantly impacts several age-related neurological problems, such as stroke, brain tumors, oxidative stress, neurodegenerative diseases (Alzheimer's, Parkinson's, and dementia), neuroinflammation, and neurotoxicity. Current treatments for these conditions often come with side effects like hallucinations, dyskinesia, nausea, diarrhea, and gastrointestinal distress. Given the widespread availability and cultural acceptance of natural remedies, research is exploring the potential effectiveness of plants in common medicines. The ancient medical system used many botanical drugs and medicinal plants to treat a wide range of diseases, including age-related neurological problems. According to current clinical investigations, berries improve motor and cognitive functions and protect against age-related neurodegenerative diseases. Additionally, berries may influence signaling pathways critical to neurotransmission, cell survival, inflammation regulation, and neuroplasticity. The abundance of phytochemicals in berries is believed to contribute to these potentially neuroprotective effects. This review aimed to explore the potential benefits of berries as a source of natural neuroprotective agents for age-related neurological disorders.

Role of platelets in the pathogenesis of delayed injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) patients develop delayed cerebral ischemia and delayed deficits (DCI) within 2 weeks of aneurysm rupture at a rate of approximately 30%. DCI is a major contributor to morbidity and mortality after SAH. The cause of DCI is multi-factorial with contributions from microthrombi, blood vessel constriction, inflammation, and cortical spreading depolarizations. Platelets play central roles in hemostasis, inflammation, and vascular function. Within this review, we examine the potential roles of platelets in microthrombi formation, large artery vasospasm, microvessel constriction, inflammation, and cortical spreading depolarization. Evidence from experimental and clinical studies is provided to support the role(s) of platelets in each pathophysiology which contributes to DCI. The review concludes with a suggestion for future therapeutic targets to prevent DCI after aSAH.

Cerebrospinal fluid superoxide dismutase and serum malondialdehyde levels in patients with aneurysmal subarachnoid hemorrhage: preliminary results

OBJECTIVES

Experimental studies provide evidence that oxidative damage plays a role in the development of vasospasm after aneurysmal subarachnoid hemorrhage (SAH) but data from human studies is still limited. The purpose of this study was to investigate the time course of cerebrospinal fluid (CSF) superoxide dismutase (SOD) and serum malondialdehyde (MDA) changes in patients with aneurysmal SAH.

METHODS

SOD in CSF and MDA in the serum were detected on days 1-3, 5 and 7 after aneurysmal SAH in 21 patients, and the results were compared with 15 patients with hydrocephalus. The results were also compared with those of clinical parameters including the patient's outcome at 6 months.

RESULTS

The mean CSF SOD levels were lower and serum MDA levels were higher than the controls. Patients with a high amount of blood within the cisterns had a trend to decreased SOD while increasing MDA levels.

CONCLUSION

These preliminary results suggest that the levels of antioxidants are decreased after the onset of SAH in the early period, possibly because of increased oxidative stress. Reactive oxygen-mediated oxidative damage may play an important role in inflammation after SAH.

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

Prevention of symptomatic vasospasm by continuous cisternal irrigation with mock-CSF containing ascorbic acid and Mg(2+)

BACKGROUND

Symptomatic vasospasm (SVS) is still a major cause of poor outcome in cases undergoing early surgical intervention for ruptured intracranial aneurysm. Among the numbers of therapeutic trials to prevent and ameliorate neurological deterioration due to SVS, removal or quenching of oxy-hemoglobin (OxyHb) from subarachnoid colts and administration of Mg(2+) (Mg) have especially been expected to be effective. In this report the authors investigated the effect of continuous cisternal irrigation (CCI) with mock CSF containing ascorbic acid (ASA) and Mg, performed after early surgery for ruptured aneurysm.

METHOD

Sixty-three cases which had received CCI were retrospectively compared with 40 control cases as to the incidence of SVS and outcome.

FINDINGS

Incidence of SVS was significantly less frequent (P < 0.05) in the CCI group (11%) than in the control group (25%). Severe and definitive SVS requiring additional specific treatment occurred only in 3.2% of the CCI group, while 22.5% in the control (P < 0.01). Overall outcome at discharge was significantly better in the CCI group than in the control (P < 0.01).

CONCLUSIONS

Postoperative CCI with ASA and Mg was definitively effective in preventing SVS and in lessening severity of SVS if it occurs.

Some extracardiac effects of diltiazem and other calcium entry blockers

Calcium entry blockers have a well documented relaxing effect of smooth muscle, vascular as well as non-vascular. Mainly as a consequence of this action, the drugs have been used for treatment of several non-cardiac disorders where hyperactivity of smooth muscle is considered to have an important role in the pathogenesis. In this short review some of these extracardiac effects of calcium entry blockers are discussed and also their clinical application.

Elevated cerebrospinal fluid and serum YKL-40 levels are not associated with symptomatic vasospasm in patients with aneurysmal subarachnoid haemorrhage

YKL-40 is a newly discovered matrix protein that is thought to be released during the acute stages of inflammation. It has recently been speculated that YKL-40 may serve as a specific serological marker of neutrophil function at the site of tissue inflammation. Our aim was to determine whether the levels of YKL-40 in both the cerebrospinal fluid and sera of 22 patients with aneurysmal subarachnoid haemorrhage were associated with either vasospasm or outcome. The levels were also compared with those of 16 control patients with hydrocephalus. We found that patients with aneurysmal subarachnoid haemorrhage had significantly higher YKL-40 levels in both cerebrospinal fluid and serum than controls. However, elevated YKL-40 levels were not associated with symptomatic vasospasm or 6-month outcome. We show that elevated YKL-40 levels are not correlated with the severity of subarachnoid haemorrhage and cannot be used as a serological marker of inflammation in patients with an aneurysm rupture.

Detection of caspase-3, neuron specific enolase, and high-sensitivity C-reactive protein levels in both cerebrospinal fluid and serum of patients after aneurysmal subarachnoid hemorrhage

OBJECTIVE

The purpose of this study is to explore whether or not the levels of caspase-3 (Casp3), neuron-specific enolase (NSE), and high-sensitivity C-reactive protein (hsCRP) were elevated in cerebrospinal fluid (CSF) and serum of patients after aneurysmal subarachnoid hemorrhage (SAH).

METHODS

This prospective clinical study consisted of 20 patients who experienced recent aneurysmal SAH and 15 control patients who experienced hydrocephalus without any other central nervous system disease. CSF and serum samples obtained within the first 3 days, and on the fifth and seventh days of SAH were assayed for Casp3, NSE, and hsCRP by using enzyme-linked immunosorbent assay.

RESULTS

Levels of Casp3, NSE, and hsCRP in the CSF (P = 0.00001, P = 0.00001, and P <0.003, respectively) and in the serum (P = 0.00001, P <0.01, and P = 0.00001, respectively) of SAH patients were found to be elevated when compared with controls with normal pressure hydrocephalus.

CONCLUSION

The authors have demonstrated the synchronized elevation of Casp3, NSE, and hsCRP in both CSF and serum of patients with aneurysmal SAH. Further studies with a large number of patients are recommended to more accurately determine the roles of these molecules in aneurysmal SAH.

Cerebral vasospasm: a consideration of the various cellular mechanisms involved in the pathophysiology

The cellular mechanisms responsible for cerebral vasospasm (CVS) occurring after subarachnoid hemorrhage (SAH) have been of major interest over the past 50 years. The present review describes how each of the discrete anatomic components that comprise the cerebral artery may contribute to the pathology of CVS. The blood extravasated after SAH is hemolyzed and undergoes degradation with resultant production of free radicals, known to be powerful initiators of vascular damage. An inflammatory response is generated activating both leukocytes and platelets with subsequent release of inflammatory agents. The cerebral artery affected by CVS undergoes phenotypic change involving both the endothelial and smooth muscle cells. In the endothelium the production of nitric oxide and prostacyclin is affected. In the smooth muscle cells signal transduction pathways that enhance the function of the contractile proteins and induce the upregulation of contractile receptors are activated. In parallel, there is evidence that nervous reflex pathways involving the trigeminal ganglion and the hypothalamus are activated. However, the relative contributions of each of the systems are speculative. Therapy may be directed at disrupting the cascade leading from the SAH insult to CVS or at overcoming the dysfunction incurred by CVS; possible therapeutical interventions are considered.

Serum and cerebrospinal fluid concentrations of E-selectin in patients with aneurysmal subarachnoid hemorrhage

The goal of the present study was to determine concentrations of E-selectin in both cerebrospinal fluid (CSF) and serum of patients with aneurysmal subarachnoid hemorrhage (SAH) and to evaluate the correlation between the clinical parameters and E-selectin levels. Both CSF and serum samples obtained from 12 patients with aneurysmal SAH and 8 patients with hydrocephalus (control group) without any other known central nervous system disease were assayed for E-selectin by quantitative enzyme-linked immunosorbent assay and the results were compared between the two groups. Mean levels of soluble forms of E-selectin within the first 3 days and on the 5th and 7th days of SAH were 4.0 +/- 7.9, 2.8 +/- 5.2, and 3.1 +/- 4.9 ng/ml in the patient's CSF, and 33.7 +/- 9.2, 35.1 +/- 7.0, and 35.2 +/- 8.7 ng/ml in serum, respectively. In contrast, mean E-selectin levels were 0.1 +/- 0.2 ng/ml in CSF and 8.7 +/- 5.0 ng/ml in serum of control patients. The difference between groups was statistically significant regarding both CSF and serum E-selectin levels (P < 0.05). Thus, we have demonstrated a marked increase of E-selectin concentration in both CSF and serum of patients with aneurysmal SAH compared with control and suggest that blocking the interaction between E-selectin and vascular endothelium may have a beneficial effect on vasospasms.

Inhibitory effect of deuterium oxide on cerebral vasospasm after experimental subarachnoid hemorrhage in a rabbit model

OBJECT

We wished to determine the inhibitory effect of deuterium oxide (D(2)O) on cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH).

METHODS AND RESULTS

An established rabbit single-hemorrhage was used. Thirty-five rabbits were randomly divided into four groups: non-treatment, sham control, lower-D(2)O, and higher-D(2)O treatment groups. Angiography was performed before (day 0) and after (day 2) SAH and the CVS ratio was calculated by comparing the diameter of the basilar artery (BA) on day 2 with that on day 0. After death, blood clot volume was assessed and the BA was dissected from the brain for histological examination. The CVS ratio in D(2)O-treatment groups was significantly higher in comparison with that in non-treatment and sham control groups (p < 0.0001). Furthermore, the volume of blood clot around the BA was reduced significantly in D(2)O-treatment groups, compared with those in both the non-treatment and the sham control groups (p < 0.05). Histological examination showed that the BA represented less folding of the internal elastic lumina in D(2)O-treatment groups, while a corrugation of the intima with the thickened vessel wall was seen in both the non-treatment and sham control groups.

CONCLUSION

Therapeutic administration of D(2)O into the cisterna magna exhibited an inhibitory effect on CVS after SAH in rabbits.

Free fatty acids in human cerebrospinal fluid following subarachnoid hemorrhage and their potential role in vasospasm: a preliminary observation

OBJECT

The mechanisms leading to vasospasm following subarachnoid hemorrhage (SAH) remain unclear. Accumulation in cerebrospinal fluid (CSF) of free fatty acids (FFAs) may play a role in the development of vasospasm; however, in no previous study have concentrations of FFAs in CSF been examined after SAH.

METHODS

We collected samples of CSF from 20 patients with SAH (18 cases of aneurysmal SAH and two cases of spontaneous cryptogenic SAH) and used a high-performance liquid chromatography assay to determine the FFA concentrations in these samples. We then compared these findings with FFA concentrations in the CSF of control patients. All FFA concentrations measured 24 hours after SAH were significantly greater than control concentrations (p < 0.01 for palmitic acid and < 0.001 for all other FFAs). All measured FFAs remained elevated for the first 48 hours after SAH (p < 0.05 for linoleic acid, p < 0.01 for palmitic acid, and p < 0.001 for the other FFAs). After 7 days, a second elevation in all FFAs was observed (p < 0.05 for linoleic acid, p < 0.01 for palmitic acid, and p < 0.001 for the other FFAs). Samples of CSF collected within 48 hours after SAH from patients in whom angiography and clinical examination confirmed the development of vasospasm after SAH were found to have significantly higher concentrations of arachidonic, linoleic, and palmitic acids than samples collected from patients in whom vasospasm did not develop (p < 0.05).

CONCLUSIONS

Following SAH, all FFAs are initially elevated. A secondary elevation occurs between 8 and 10 days after SAH. This study provides preliminary evidence of FFA elevation following SAH and of a potential role for FFAs in SAH-induced vasospasm. A prospective study is warranted to determine if CSF concentrations of FFAs are predictive of vasospasm.

Current concepts in neurocritical care

The current concepts in neurocritical care including advancement in therapeutic interventions and monitoring modalities are covered for four entities: stroke, subarachnoid hemorrhage, traumatic brain injury and spinal cord injury. Although therapies were mainly supportive in the past, acute ischemic stroke may now be treated with tissue plasminogen activator if inclusion and exclusion criteria are met. The management of subarachnoid hemorrhage including cerebral vasospasm is discussed in detail. Traumatic brain injury and spinal cord injury with prevention of secondary injury to limit further sequelae are also covered. Medical complications which increase morbidity and mortality are also presented.

Prevention and reversal of experimental posthemorrhagic vasospasm by the periadventitial administration of nitric oxide from a controlled-release polymer

OBJECTIVE

Despite improvements in the care of patients with aneurysmal subarachnoid hemorrhage, delayed cerebral vasospasm remains a major cause of morbidity and death. There is now evidence that a decrease in the local availability of nitric oxide (NO) plays a role in delayed cerebral vasospasm. We evaluated a controlled-release polymer containing the NO donor (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO) for the treatment of chronic posthemorrhagic vasospasm in the rat femoral artery model.

METHODS

The release kinetics of ethylene/vinyl acetate copolymers loaded with 20% (w/w) DETA/NO were determined in vitro. Chronic vasospasm was induced in the left femoral artery of adult male Fischer 344 rats (n = 35) by exposure to autologous blood. At 1, 3, or 7 days after blood exposure, either a 5-mg polymer loaded with 20% (w/w) DETA/NO or an empty 5-mg polymer was placed in the periadventitial space next to the left femoral artery. At the same time, an empty 5-mg polymer was placed next to the right femoral artery. On the 8th day after blood exposure (at the peak of vasospasm in this model), rats were transcardially perfused with 4% paraformaldehyde, and the left and right femoral arteries were removed for histological processing and morphometric analyses. Vasospasm was expressed as the percent lumen patency of the treated left artery, compared with the control right artery.

RESULTS

The in vitro release kinetics demonstrated that the 20% DETA/NO-loaded polymers released up to 15% of their total drug load during a 9-day period. DETA/NO treatments initiated at 1, 3, or 7 days after blood deposition all significantly inhibited vasospasm, compared with control values (94.6 +/- 7.2% versus 67.6 +/- 5.8%, 104.6 +/- 5.5% versus 64.9 +/- 1.7%, and 102.4 +/- 5.1% versus 73.6 +/- 1.4%, respectively; mean +/- standard error of the mean percent lumen patency; P < 0.001). No adverse effects of treatment were observed.

CONCLUSION

The diazeniumdiolate NO donor DETA/NO can be effectively released from ethylene/vinyl acetate polymers. Administration of DETA/NO into the periadventitial space can prevent the development of chronic posthemorrhagic vasospasm in the rat femoral artery and can reverse established vasospasm. No adverse effects of DETA/NO were observed in this model.

A study of blood coagulation and fibrinolytic system in spontaneous subarachnoid hemorrhage. Correlation with hunt-hess grade and outcome

BACKGROUND

Subarachnoid hemorrhage (SAH) has been studied from various standpoints with the purpose of discovering criteria that might be useful in predicting the prognosis. In the literature a high incidence of coagulative and fibrinolytic disorders has been reported in SAH patients. A prospective study was performed to evaluate hemostatic plasmatic parameters in SAH patients.

METHODS

Hemostatic plasmatic parameters were prospectively studied in 76 patients with SAH. Both the coagulative (PT, APTT, fibrinogen, thrombin/antithrombin complex: TAT, and modified antithrombin III: MAT) and fibrinolytic (D-dimer) plasmatic systems were evaluated. Von Willebrand factor was also tested.

RESULTS

PT, APTT, and fibrinogen were within normal limits. High TAT levels were associated with clinical outcome since 16 patients out of 27 (59%) with unfavorable outcomes displayed TAT levels >20 ngzaq/L, as compared with 10 patients out of 38 (26%) with favorable outcomes. Plasmatic D-dimer, an index of subarachnoid clot lysis, was invariably found to be elevated. Nevertheless, very high levels (>1000 mcg/mL) were found in 16 patients out of 22 (73%) with unfavorable outcomes but in only 9 patients out of 38 (26%) with favorable outcomes. Significant D-dimer elevation showed a strong association with severe delayed ischemic deficit (DID). Patients were also tested for von Willebrand factor, displaying a specific increase in all cases.

CONCLUSION

The study provides evidence for an early activation of the coagulation and fibrinolytic system following SAH. Increase of plasmatic TAT parallels clinical outcome. A generalized increase of D-dimer was observed as well and D-dimer levels in the high range were associated with clinical outcome and poor results with DID. Our analysis shows close statistical significance between plasma levels of TAT, D-dimer, and outcome. A similar statistical significance has been found when comparing other known prognostic factors such as clinical and cerebral computerized tomography scan (CT) grade and outcome.

Role of adenosine 5'-triphosphate in vasospasm after subarachnoid hemorrhage: human investigations

OBJECTIVE

Adenosine 5'-triphosphate (ATP) is a vasoactive compound found in high concentrations inside erythrocytes. This compound may contribute to vasospasm after subarachnoid hemorrhage (SAH). We assessed the hypothesis that ATP contributes to vasospasm in humans.

METHODS

ATP and hemoglobin concentrations were measured in cerebrospinal fluid (CSF) from humans with SAH and in blood incubated in vitro. The vasoactivity of the human CSF samples and of fractionated (fractions with molecular weight greater than or less than 10 kDa) and unfractionated blood incubated in vitro was assessed by application of samples to canine basilar artery segments under isometric tension.

RESULTS

ATP in human CSF declined within 72 hours of SAH to concentrations too low to contract cerebral arteries. Vasoactivity of human CSF correlated with the concentration of hemoglobin. The vasoactivity of incubated erythrocyte hemolysates remained high despite a decline in ATP concentrations. Fractionation of incubated erythrocyte hemolysates showed that for incubation periods up to 7 days, all vasoactivity was in a fraction of molecular weight greater than 10 kDa.

CONCLUSION

ATP is unlikely to contribute to vasospasm because the concentrations in CSF after SAH in humans are not high enough to cause vasospasm after 72 hours. The vasoactivity of erythrocyte hemolysate is not related to the ATP or ferrous hemoglobin content but may be related to the total hemoglobin content. Therefore, ATP is unlikely to be a major cause of clinically significant delayed vasospasm.

Molecular keys to the problems of cerebral vasospasm

The mechanisms responsible for subarachnoid hemorrhage (SAH)-induced vasospasm are under intense investigation but remain incompletely understood. A consequence of SAH-induced vasospasm, cerebral infarction, produces a nonrecoverable ischemic tissue core surrounded by a potentially amenable penumbra. However, successful treatment has been inconsistent. In this review, we summarize the basic molecular biology of cerebrovascular regulation, describe recent developments in molecular biology to elucidate the mechanisms of SAH-induced vasospasm, and discuss the potential contribution of cerebral microcirculation regulation to the control of ischemia. Our understanding of the pathogenesis of SAH-induced vasospasm remains a major scientific challenge; however, molecular biological techniques are beginning to uncover the intracellular mechanisms involved in vascular regulation and its failure. Recent findings of microvascular regulatory mechanisms and their failure after SAH suggest a role in the development and size of the ischemia. Progress is being made in identifying the various components in the blood that cause SAH-induced vasospasm. Thus, our evolving understanding of the underlying molecular mechanism may provide the basis for improved treatment after SAH-induced vasospasm, especially at the level of the microcirculation.

Reversal of cerebral vasospasm using an intrathecally administered nitric oxide donor

OBJECT

Intrathecal bolus administration of (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)aminio]diazen++ +-1-ium-1,2-diolate (DETA/NO), a long half-life diazeniumdiolate-class nitric oxide (NO) donor, was evaluated for safety and efficacy in the treatment of delayed cerebral vasospasm in a canine model of subarachnoid hemorrhage (SAH).

METHODS

The baseline basilar artery (BA) diameter of 25 dogs was measured with the aid of angiography on Day 0. Vasospasm was then induced by intracisternal injection of autologous arterial blood on Days 0 and 2. Repeated arteriography on Day 7 revealed an average BA diameter of 58% of baseline. Each dog was then randomized to one of four groups: a pathology control group (SAH only, four animals); a treatment control group (SAH plus 2 micromol of the inactive drug carrier DETA, eight animals); a low-dose treatment group (SAH plus 0.2 micromol DETA/NO, six animals); or a high-dose treatment group (SAH plus 2 micromol DETA/NO, six animals). The drugs were administered in a 2-ml intrathecal bolus via the cisterna magna. Arterial caliber was monitored by angiography over the subsequent 4 hours. A 2-micromol dose of the drug was then given and serial arteriography continued for an additional hour to screen for tachyphylaxis. Intracranial pressure and respiratory and hemodynamic parameters were continuously monitored. Histopathological analyses of the animals' brains were performed after the dogs were killed on Day 8. The drug DETA/NO produced reversal of vasospasm in a dose-dependent fashion that roughly followed a double exponential time course. Doses of 2 micromol DETA/NO resulted in restoration of the angiographically monitored BA diameter to the prevasospasm size at 1.5 hours posttreatment, and this was sustained at 88% of baseline at 4 hours (p < 0.01, independent samples t-test). By contrast, the treatment control group remained on average at 54% of baseline diameter. The low-dose treatment group achieved only partial and more transitory relaxation. Histopathological analyses showed findings consistent with chronic SAH but did not demonstrate any toxicity associated with the NO donor. No adverse physiological changes were seen.

CONCLUSIONS

This study indicates that long-acting NO donors are potentially useful as agents to restore circulation in patients suffering from cerebral vasospasm.

Role of ferrous iron chelator 2,2'-dipyridyl in preventing delayed vasospasm in a primate model of subarachnoid hemorrhage

OBJECT

Oxyhemoglobin (HbO2) causes vasospasm after subarachnoid hemorrhage (SAH). The most likely spasmogenic component of HbO2 is iron. Various iron chelators, such as deferoxamine, have prevented vasospasm in vivo with limited success. However, only chelators of iron in the ferric state have been studied in animal models of vasospasm after SAH. Because free radical formation requires the ferrous (Fe++) moiety and Fe++ is a potent binder of the vasodilator nitric oxide, the authors hypothesized that iron in the ferrous state causes vasospasm and that chelators of Fe++, such as 2,2'-dipyridyl, may prevent vasospasm. This study was undertaken to investigate the influence of 2,2'-dipyridyl on vasospasm after induction of SAH in a primate model.

METHODS

Twelve cynomolgus monkeys were randomly divided into two groups and then both groups underwent placement of an arterial autologous blood clot in the subarachnoid space around the right middle cerebral artery (MCA). The five animals in the control group received intravenously administered saline and the seven treated animals received intravenously administered chelator (2,2'-dipyridyl) for 14 days. Sequential arteriography for assessment of MCA diameter was performed before and on the 7th day after SAH.

CONCLUSIONS

Prevention of cerebral vasospasm by means of treatment with continuous intravenous administration of 2,2'-dipyridyl is reported in a primate model of SAH. This result provides insight into the possible mechanism of delayed vasospasm after aneurysmal SAH and provides a potential preventive therapy for it.

Loss of nitric oxide synthase immunoreactivity in cerebral vasospasm

To determine the distribution of nitric oxide synthase (NOS) in the primate cerebral artery nervi vasorum and to examine the potential role of NOS in cerebral vasospasm after subarachnoid hemorrhage (SAH) in primates, the distribution of NOS immunoreactivity (NOS-IR) in the major cerebral arteries was examined immunohistochemically in cynomolgus monkeys by the use of whole, mounted preparations of the circle of Willis. In four normal monkeys, NOS-IR was localized to the endothelial and adventitial layers of the large cerebral arteries. On the abluminal side, NOS-IR staining was densely concentrated in perivascular nerve fibers (nervi vasorum) of the anterior circulation. Staining was less prominent in the posterior circulation. In six monkeys with vasospasm on Day 7 after placement of preclotted arterial blood to form an SAH around the right middle cerebral artery (MCA) (42% +/- 8.3% decrease of MCA area, mean +/- standard deviation), NOS-IR was virtually absent in nerve fibers around the spastic right MCA but was normal on the contralateral side. In five monkeys in which vasospasm resolved by Day 14 after SAH (36% +/- 14% decrease of right MCA area on Day 7, and 5% +/- 14% decrease on Day 14), NOS-IR was also absent in the right MCA adventitial nerve fibers and remained normal in the left MCA. Adventitial NOS-IR was also normal in cerebral vessels of a sham-operated, nonspastic monkey. These findings provide further evidence that nitric oxide (NO) functions as a neuronal transmitter to mediate vasodilation in primates and indicate a role for adventitial NO in the pathogenesis of cerebral vasospasm after SAH in humans.

Functional changes in cultured strips of canine cerebral arteries after prolonged exposure to oxyhemoglobin

The present study was undertaken to determine whether oxyhemoglobin (OxyHb) is responsible for the functional alterations in the cerebral arteries observed during chronic vasospasm after subarachnoid hemorrhage. Vascular strips of canine basilar arteries were kept in organ culture for 3 days with or without repetitive exposure to OxyHb (OxyHb-treated and control strips). Contractions elicited by high levels of potassium (80 mM) and uridine 5'-triphosphate (3 x 10(-4) M) were reduced in the OxyHb-treated group in a concentration-dependent manner. The relaxations evoked by nitric oxide and 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP) were not affected. Relaxations elicited by the calcium channel blocker, diltiazem, were attenuated in the OxyHb-treated rings. When the extracellular calcium concentration ([Ca2+]e) was changed from a concentration in the external solution of 10(-8) M to 10(-3) M, myogenic tension developed. Myogenic tension, expressed as a percentage of the maximum contraction in each segment, was augmented in the OxyHb-treated group at [Ca2+]e of 10(-5) M and 10(-4) M. There were no significant differences in passive compliance of the arterial wall between the two groups. These results demonstrated that prolonged exposure to OxyHb in vitro results in a decrease in contractile capacity and an increase in sensitivity to [Ca2+]e, in agreement with previous findings in spastic arteries. By contrast, impairment of the 8-bromo-cGMP-mediated relaxation pathway and increased stiffness of the arterial wall, which have been reported to occur in spastic arteries, were not induced by prolonged exposure to OxyHb in vitro.

The role of hemolysate in the facilitation of oxyhemoglobin-induced contraction in rabbit basilar arteries

The importance of factors within hemolysate in modulating oxyhemoglobin (oxyHb)-induced contraction was examined in an in vitro model of rabbit basilar arteries. When the basilar arteries were exposed to purified oxyHb alone, the contractile response observed was significantly weaker than that seen in arteries exposed to hemolysate containing an equal concentration of oxyHb. In order to delineate the nature of the factors within hemolysate that facilitate contraction, hemolysate was fractionated, and various components were tested individually for their ability to elicit this effect. A low-molecular-weight fraction of hemolysate, ranging from 0.5 to 2.0 kD, elicited only a mild contraction. However, when this fraction was combined with purified oxyHb, the contractile response was comparable in magnitude to that of unfractionated hemolysate. These studies confirm that purified oxyHb is capable of inducing contraction in vitro. The data also demonstrate that oxyHb elicits a significantly weaker contraction than does hemolysate. In addition, the results suggest that low-molecular-weight components in hemolysate (in the 0.5- to 2.0-kD range), while incapable of inducing a potent contraction alone, may act in concert with oxyHb to elicit the vasoconstriction seen following subarachnoid hemorrhage.

The role of superoxide anions in the pathogenesis of cerebral vasospasm

BACKGROUND AND PURPOSE

To determine the role of superoxide anions in the pathogenesis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage, we studied the preventive effect of human recombinant copper-zinc superoxide dismutase (h-r SOD) in a rabbit subarachnoid hemorrhage (SAH) model.

METHODS

Forty-five rabbits receiving intracisternal injection of 3 mL autologous nonheparinized blood or 3 mL saline were divided into four groups as follows: (1) saline injected and no treatment (control group, n = 6); (2) blood injected and no treatment (SAH group, n = 20); (3) blood injected and treated by multiple intracisternal injections of 30,000 U of h-r SOD in 0.5 mL saline (SOD group, n = 9); and (4) blood injected and treated by multiple intracisternal injections of 0.5 mL saline (saline group, n = 10). Serial angiograms were performed after the blood injection, and the diameter of the basilar artery was measured. Three animals from the control group and five animals from the SAH and SOD groups each were killed 2 days after SAH, and their basilar arteries were processed for transmission electron microscopic observations.

RESULTS

In the SAH and saline groups, the diameter of the basilar arteries was significantly reduced (28 +/- 14% and 27 +/- 9%, respectively) at 2 days after the blood injection, then recovered to pre-SAH levels until 11 days. In the SOD group, the diameter of the basilar artery was only minimally changed during the follow-up period. Transmission electron microscopy revealed endothelial injury in all basilar arteries in the SAH group, whereas endothelial injury was minimal in the SOD group.

CONCLUSIONS

We determined that h-r SOD prevents the occurrence of vasospasm, possibly as a result of preventing endothelial injury initiated by superoxide anions.

Effect of stroma-free hemoglobin and diaspirin cross-linked hemoglobin on the regional circulation and systemic hemodynamics

The effects of unmodified stroma-free hemoglobin (SFHb) and diaspirin cross-linked hemoglobin (DCLHb) on the regional blood circulation and systemic hemodynamics were studied in rats using a radioactive microsphere technique. SFHb and DCLHb increased mean arterial blood pressure without affecting heart rate. SFHb produced a 24.9% decrease in the cardiac output while DCLHb produced an 44.8% increase in the cardiac output. Stroke volume was decreased (-27.3%) by SFHb and increased (+36.4%) by DCLHb. Total peripheral resistance increased with both SFHb and DCLHb. DCLHb increased blood flow to the heart, spleen, stomach, small intestine and skin, and had no effect on blood flow to the brain, kidneys, liver, mesentery, pancreas, caecum, large intestine and musculo-skeletal system. In contrast, in animals infused with SFHb, blood flow decreased to the kidneys, liver and spleen, increased to the heart, small intestine and skin, and had no effect to the brain, caecum, large intestine and musculo-skeletal system. DCLHb had no effect on vascular resistance in any organ except for an increase in the musculo-skeletal system. In contrast, SFHb increased vascular resistance in the kidneys, liver, spleen, skin, mesentery and pancreas, and had no effect on vascular resistance in the musculo-skeletal system, brain, heart, stomach, small intestine, caecum and large intestine. SFHb had no effect on distribution of cardiac output to the brain, gastrointestinal tract (GIT), kidneys, skin, musculo-skeletal and portal system, while DCLHb significantly decreased the percent cardiac output to the musculo-skeletal system. DCLHb did not affect the distribution of cardiac output to the brain, GIT, kidneys, skin and portal system. SFHb and DCLHb increased the percent cardiac output to the heart. It is concluded that similar concentrations and doses of DCLHb and SFHb produce different effects on the regional blood circulation and systemic hemodynamics.

Bilirubin levels in subarachnoid clot and effects on canine arterial smooth muscle cells

BACKGROUND AND PURPOSE

Previous studies have suggested that bilirubin is a potential contributor to cerebral vasospasm. The purpose of this investigation was to determine whether bilirubin accrues in subarachnoid clot, whether its vasoconstrictive effect could involve a direct action on arterial smooth muscle cells, and, if so, whether bilirubin affects their Ca2+ uptake.

METHODS

Subarachnoid clots were analyzed for bilirubin using high-performance liquid chromatography. The length and 45Ca2+ uptake of vascular smooth muscle cells enzymatically dissociated from canine carotid arteries were measured before and after exposure to bilirubin solution. Additional experiments were conducted on cultured smooth muscle cells from canine basilar artery and on ATP-depleted cardiac myocytes.

RESULTS

Mean +/- SE bilirubin concentration in experimental clot was 263 +/- 35.7 mumol/L. Vascular smooth muscle cells exposed to bilirubin showed progressive shortening (P < .01) and an increased uptake of 45Ca2+ (P < .001). Contraction was prevented by Ca(2+)-free media but not by verapamil. Experiments with heart myocytes showed that bilirubin caused an increased uptake of 45Ca2+ but not of [14C]sucrose.

CONCLUSIONS

The results indicate that bilirubin accrues in subarachnoid clot, that it exerts a direct constrictive effect on arterial smooth muscle cells, and that this effect is associated with an increased uptake of Ca2+. Studies on heart myocytes suggest that the Ca2+ uptake induced by bilirubin could be due to a selective increase in membrane permeability to Ca2+.

Hemin: levels in experimental subarachnoid hematoma and effects on dissociated vascular smooth-muscle cells

Although hemin is known to exert toxic effects on a variety of cell types, its possible participation in the genesis of cerebral vasospasm has received little attention. The authors measured the concentration of hemin in experimental subarachnoid clot and studied its effects on the morphology and 45Ca++ uptake of vascular smooth-muscle cells dissociated from canine carotid artery. Craniectomies were performed in five dogs under general anesthesia, and 3 to 5 ml of autologous whole blood was deposited in the supraclinoid subarachnoid compartment. The concentration of hemin recovered by Folch extraction from clotted material removed 7 days after surgery was 390 +/- 247 microM (mean +/- standard error of the mean). Mean vascular smooth-muscle cell length after 40 minutes of exposure to 50 microM hemin was 37.3 +/- 1.2 microns (control 51.6 +/- 1.6 microns) (p < 0.01). The mean percent permeation of 45Ca++, measured by a dual label technique, of cells exposed to hemin was 200.9% +/- 23% (control 102.9% +/- 4.3%) (p < 0.01). These findings indicate that hemin accrues in subarachnoid hematoma, that it exerts a constrictive effect on vascular smooth-muscle cells, and that this effect is associated with an increased uptake of Ca++. This study demonstrates that hemin should be included in the list of potential agents that participate in the development of cerebral vasospasm.

Etiology of cerebral vasospasm in primates

A primate model was used to determine whether oxyhemoglobin (OxyHb), methemoglobin (MetHb), or bilirubin is likely to be responsible for cerebral vasospasm following subarachnoid hemorrhage (SAH). Forty cynomolgus monkeys were randomly assigned to one of five groups. On Day 0, each animal underwent angiography followed by right craniectomy and placement of an Ommaya reservoir with its catheter adjacent to the right middle cerebral artery (MCA). The animals received intrathecal injections twice a day for 6 days of one of the following solutions: mock cerebrospinal fluid (CSF); OxyHb; MetHb; bilirubin; or supernatant fluid from an incubated mixture of autologous blood and mock CSF. On Day 7, angiography was repeated and the animals were killed. Comparison of angiograms obtained on Day 0 and Day 7 of the experiment showed significant vasospasm of the right MCA and the right anterior cerebral and internal carotid arteries in the animal groups that had received OxyHb or supernatant fluid. There was a smaller reduction in diameter of the same vessels in the bilirubin group (not statistically significant), while no effects were observed in the groups receiving MetHb or mock CSF. Electron microscopy of the right MCA's gave results consistent with the angiographic findings. One monkey in the OxyHb group developed a delayed-onset right MCA infarction. These data suggest that OxyHb is the cause of cerebral vasospasm following SAH.

A review of hemoglobin and the pathogenesis of cerebral vasospasm

We believe that current experimental and clinical evidence can be most satisfactorily interpreted by assuming that oxyhemoglobin is the cause of cerebral vasospasm that follows subarachnoid hemorrhage. We review the pathogenetic mechanisms by which oxyhemoglobin affects cerebral arteries. The relative importance of each of these mechanisms in the genesis of vasospasm, the biochemical pathways of oxyhemoglobin-induced smooth muscle contraction, and the intracellular actions of oxyhemoglobin on smooth muscle and on other cells in arteries are still not definitely established.

Haem derivatives in subdural haematomas

The oxyhaemoglobin, methaemoglobin and bilirubin concentrations were determined in subdural haematomas and cerebrospinal fluid from 18 patients. The total haem derivative concentration ranged from 55 mumol/l to 13.9 mmol/l in the haematomas and from 0.1 mumol/l to 8.2 mumol/l in the cerebrospinal fluid. Bilirubin was the dominating fraction in haematomas with haem derivative concentrations lower than 1 mmol/l. For haematomas exceeding this value, the bilirubin transforming capacity seemed to have reached a maximum. More of the oxyhaemoglobin was oxidized to methaemoglobin in these cases, a reaction known to release superoxide radicals. The possible pathophysiological significance hereof, e.g. in cerebral vasospasm, is discussed.

Potentiating effects of extraluminal oxyhemoglobin to intraluminal 5-hydroxytryptamine in isolated canine internal carotid arteries

The interaction between oxyhemoglobin (oxyHb) and 5-hydroxytryptamine (5-HT) was investigated in an experimental model of isolated canine internal and common carotid arteries with insertion of stainless steel cannulae. Extraluminal application of 10(-5) M oxyHb induced marked and long-lasting vasoconstriction in the internal carotid but not in the common carotid arteries. The 5-HT-induced vasoconstriction was potentiated significantly in both the internal and common carotid arteries. These potentiations were not influenced by the presence or absence of endothelium, a finding which was confirmed by vascular responses to intraluminal acetylcholine. It is concluded that the interaction between extraluminal oxyHb and intraluminal 5-HT may be one of the possible etiological factors behind the chronic phase of vascular spasm following subarachnoid hemorrhage.

Evaluation of the role hemoglobin in cerebrospinal fluid plays in producing contractions of cerebral arteries

Many investigators have concluded that hemoglobin is the spasmogen responsible for cerebral vasospasm. The present study was designed to ascertain whether the contractile responses of isolated canine basilar arteries to xanthochromic cerebrospinal fluid from subarachnoid hemorrhage patients was associated with hemoglobin concentration as measured spectrophotometrically. The results clearly showed that spasmogenicity and hemoglobin content were not correlated. The magnitude and duration of the arterial responses varied greatly, further indicating that more than a single factor was responsible. The potent antagonistic, vasodilator effect of such proteins as antithrombin III may account for some of the variation, but the results directly complement clinical findings of others indicating that hemoglobin is not the singular cause of cerebral vasospasm.

Comparison of the inhibitory effects of antithrombin III, alpha 2-macroglobulin, and thrombin in human basilar arteries: relevance to cerebral vasospasm

Isolated human basilar arteries were used in this study to evaluate the inhibitory effect of antithrombin III (AT III), thrombin, and alpha 2-macroglobulin (alpha 2-M) on contractions elicited by K+, serotonin (5-HT), prostaglandin (PG) D2, PGF2 alpha, and plasmin. alpha 2-M (0.5-1.0 mg/ml) failed to affect the contractions produced by contractile agonists significantly but did notably reduce the basal tone of the arteries. Thrombin (1 and 10 U/ml) reduced basal tone and significantly inhibited the contractions elicited by K+, PGF2 alpha, and plasmin. The relaxant effect of thrombin was abolished by procedures that destroy endothelium and by exposing the artery to thrombin for prolonged periods (tachyphylaxis). AT III (1-6 U/ml) reduced basal tone and significantly inhibited, in a concentration-dependent manner, the contractile responses to K+, 5-HT, PGD2, PGF2 alpha, and plasmin. In sharp contrast to thrombin, AT III did not induce tachyphylaxis nor was its vasorelaxant effect significantly reduced by destruction of the endothelium. The results show AT III to be a potent and nonspecific inhibitor of human cerebral arteries and support the hypothesis that AT III may contribute to the delay of cerebral vasospasm seen in patients who experience aneurysmal hemorrhage.

Vasodilator proteins: role in delayed cerebral vasospasm

Blood proteins could play a critical role in the pathogenesis of cerebral vasospasm in subarachnoid hemorrhage (SAH) as agonists and as antagonists of vasoconstriction. The present study was designed primarily to quantify the inhibition produced by antithrombin III of the phasic responses elicited by cumulative doses of KCl, serotonin (5-HT), uridine triphosphate (UTP), and thrombin in isolated canine basilar arteries, and to ascertain whether other proteins might act similarly. Antithrombin III (1 unit/ml and 3 units/ml) given 2 min beforehand inhibited all agonists. The inhibition was not dependent on a functional endothelium nor due to stimulation of the electrogenic sodium pump. Alpha2-macroglobulin (0.1 mg/ml and 0.4 mg/ml) inhibited the contractile responses to high K+, 5-HT and thrombin. Kallikrein (1 and 4 units/ml) did not inhibit UTP but inhibited high K+ and 5-HT through an effect on the endothelium. Kallikrein (1 unit/ml) irreversibly blocked the responses to thrombin. Globulins (3 mg/ml) and fibrinogen (0.3 mg/ml) were not inhibitory. The results demonstrate that anticoagulant proteins are very effective nonspecific inhibitors of the vasoconstriction, whereas the serine protease kallikrein selectively blocks thrombin. The remarkable potency of antithrombin III suggests that it may protect cerebral arteries from exhibiting vasospasm in SAH.

Bifrontal interhemispheric approach to aneurysms of the anterior communicating artery

The authors review their experience with the bifrontal interhemispheric approach in 603 cases of single anterior communicating artery (ACoA) aneurysms and describe the operative technique. With this approach, the olfactory tracts are dissected, and both A1 segments of the anterior cerebral arteries are identified subfrontally. The interhemispheric fissure is then dissected and A2 segments are followed from the distal portion toward the ACoA complex. Following the administration of a combination of mannitol, vitamin E, and dexamethasone, a temporary clip is placed on at least the dominant A1 segment prior to dissection of the aneurysm itself. Once the aneurysm has been completely freed from the surrounding structures, the neck is ligated and clipped. If the aneurysm ruptures during surgery, temporary clips are placed on both A1 and A2 segments bilaterally and the operation proceeds in a completely dry field. With this method, it is possible to occlude any of the intracranial vessels for up to 40 minutes within 100 minutes of drug administration. To prevent the possibility of rerupture and the development of vasospasm in the period before aneurysm surgery, the authors have adopted a policy of performing ultra-early operations within 48 hours of the onset of symptoms. Among the 257 cases operated on during the 9 years since 1975, one-fifth have been operated on within 48 hours of rupture, and the in-hospital mortality rate has been only 4.3% (11 cases). Follow-up studies have shown that 87% of the 246 surviving patients have returned to useful lives.

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage is one of the most important causes of cerebral ischemia, and is the leading cause of death and disability after aneurysm rupture. There are two definitions of cerebral vasospasm: angiographic and clinical. Care must be exercised to be certain that it is clear which entity is being addressed. The diagnosis of the clinical syndrome is one of exclusion and can rarely be made with absolute certainty. The pathogenesis of cerebral vasospasm is poorly understood. Most current theories focus on the release of factors from the subarachnoid clot. More attention must be given to the role of endothelial damage and alterations in the blood-arterial wall barrier. The application of modern techniques for studying vascular smooth muscle which have been developed as a result of research in the areas of hypertension and atherosclerosis must be applied to the problem of cerebral vasospasm. A stress test to select patients with angiographic arterial narrowing who have adequate cerebral vascular reserve to undergo surgery should be developed. The optimal treatment of vasospasm awaits development of agents for blocking or inactivating spasmogenic substances or blocking arterial smooth muscle contraction. Rheological or hemodynamic manipulations to prevent or reverse ischemic consequences of vasospasm are relatively effective, but complicated and hazardous, and should be viewed principally as interim measures awaiting development of more specific therapies for the arterial narrowing.

Cerebral vasospasm as a complication of aneurysmal subarachnoid hemorrhage: a brief review

Cerebral vasospasm is one of the most dreaded consequences of a ruptured intracranial aneurysm. Although exceptions may be found, the relationship between angiographic narrowing of cerebral arteries and deterioration of clinical status is supported by many authors. The cause of cerebral vasospasm still remains obscure. Several substances such as serotonin, prostaglandins, catecholamines appear to have a vasoconstrictive effect on the cerebral vessels. Recent evidence indicates that erythrocyte lysis within the subarachnoid spaces may play a major role in the genesis of delayed clinically relevant cerebral vasoconstriction following aneurysmal subarachnoid hemorrhage (SAH). The pathophysiology of brain ischemia following aneurysmal rupture, and the correlation between angiographic vasospasm, neurological condition, intracranial pressure (ICP) value, cerebral blood flow and CT findings are briefly discussed. It is concluded that, at present, blood volume expansion and/or induced hypertension, and pharmacological control of increased ICP provide the best basis for clinical management of the cerebral ischemic complications of SAH. Preoperative antifibrinolytic therapy and delayed surgical obliteration of the bleeding aneurysm, i.e. the policy at present most frequently adopted, are currently undergoing critical review in the light of the fact that antifibrinolytic therapy seems to be accompanied by a higher rate of ischemic SAH complications and vasospasm, whilst there are very recent suggestions that the results of early intracranial aneurysm surgery may be better than those of delayed surgery, if account is taken of the patients lost because of recurrent SAH or ischemia during the waiting period.

Surgical treatment of middle cerebral artery aneurysms

The authors report their experience with the surgical therapy of middle cerebral artery (MCA) aneurysms in 413 cases, and describe their technique. After the M1 portion of the MCA is identified, the Sylvian fissure is opened. During the administration of 20% mannitol, temporary occluding clips are applied to the feeding and draining vessels of the aneurysm. The aneurysm is freed from all surrounding tissue, and the aneurysm neck is treated by ligation, clipping, or wrapping. Analysis of surgical results in 91 cases operated on after the surgical approach had become standardized indicates that more than 94% of patients have returned to useful social lives by the time of follow-up evaluation. Twenty-four percent of these patients were operated on within 48 hours after subarachnoid hemorrhage.

CSF smooth-muscle constrictor activity associated with cerebral vasospasm and mortality in SAH patients

Cerebrospinal fluid (CSF) was collected preoperatively (by lumbar puncture) or perioperatively (by lumbar or ventricular drain) from 32 patients with subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysms. Samples were also obtained from six control patients without evidence of subarachnoid blood. Smooth-muscle constrictor activity in the CSF was measured by bioassay using the isolated rat stomach fundus preparation. Concentrations of unidentified smooth-muscle constrictor substances were considerably greater in CSF from a group of seven patients with evidence of severe angiographic vasospasm and/or delayed ischemic deficits who died (73.8 +/- 39.7 nmol/liter prostaglandin E2 (PGE2) equivalents), as compared to 25 other SAH patients who survived (6.5 +/- 1.4 nmol/liter PGE2 equivalents), and six control patients (1.17 +/- 0.34 nmol/liter PGE2 equivalents). The data suggest that there is a relationship between smooth-muscle constrictor substances in the CSF after SAH and both the degree of angiographic vasospasm and the outcome. It is possible that this relationship might be exploited clinically.

The role of hemoglobin in the etiology of cerebral vasospasm. An in vivo study of baboons

Oxyhemoglobin was injected intracisternally into three baboons, and methemoglobin into one baboon, in an attempt to mimic the prolonged cerebral arterial spasm sometimes seen after subarachnoid hemorrhage due to aneurysm rupture. Cerebral angiography was performed for up to 7 days after injection of hemoglobin, and the degree of vasospasm was estimated from the angiograms. Oxyhemoglobin caused slight arterial narrowing, which lasted for 3 days. Methemoglobin had no significant effects. Motor neurological deficits and histopathological signs, characteristic of prolonged cerebral vasospasm, were not observed. It was concluded that hemoglobin alone is not capable of causing the cerebral vasospasm syndrome in these experimental animals.

The effect of prostacyclin on cerebral vasospasm. An experimental study

Prostacyclin (PGI2), a strong vasodilator of cerebral vessels and potent inhibitor of platelet aggregation, was infused intravenously into seven cats after induction of prolonged vasospasm by hourly application of oxyhaemoglobin solution into the subarachnoid space round the basilar artery. PGI2, at a concentration of 50 ng/kg/min, was effective in releasing the vasospasm in the seven cats. It did not produce significant hypotension. This report gives our results and the probable mechanism of action of PGI2 in cerebral vasospasm.

Cerebral vasoactivity of heme proteins in vitro. Some mechanistic considerations

The dose responses of canine basilar arteries to human hemoglobin, rabbit hemoglobin, horse-heart myoglobin, and human methemoglobin and cyanomethemoglobin are compared in this paper. The in vitro arterial segments responded similarly to the hemoglobins and myoglobin when doses were based on the hemoglobin dimer rather than on the tetramer. Superoxide free radicals produced by the autoxidation of hemoglobin to methemoglobin do not seem to be involved in the mechanism of hemoglobin-induced vasocontraction as the contraction cannot be blocked by superoxide dismutase or other agents known to react with superoxide-generated products. Nonspecific uptake of hemoglobin into the smooth-muscle cells by pinocytosis is also discounted.

Relation of cerebral vasospasm to operative findings of subarachnoid blood around ruptured aneurysms

An investigation was carried out in 28 patients in order to evaluate the relationship between angiographically documented vasospasm, amount of subarachnoid blood found at surgery around ruptured intracranial aneurysms, and delayed ischaemic deficits. Angiography was performed at time intervals ranging between 5 and 17 days, and surgery not later than 21 days following subarachnoid haemorrhage. The absence of subarachnoid clots was associated in ten patients, with no or minor vasospasm and no or mild neurological deficits. Thin clots were found in eight patients; one of them had no vasospasm, six had minor vasospasm, and one showed severe vessel narrowing. Major clinical signs were absent in these cases. All ten patients with thick clots developed severe vasospasm, and eight of them severe neurological signs. The important aetiological role of local subarachnoid clots developed severe vasospasm, and eight of them severe neurological signs. The important aetiological role of local subarachnoid clots in determining vasospasm in emphasized in view of surgical timing.

Medical management of patients following a ruptured cerebral aneurysm, with epsilon-aminocaproic acid, kanamycin, and reserpine

Patients suffering from a subarachnoid hemorrhage who were admitted to the Neurosurgical Unit of the Royal Perth Hospital during the period 1971 to 1979 were assessed with regard to the effectiveness of preoperative treatment with epsilon-aminocaproic acid, kanamycin, and reserpine. Forty-two patients who were treated with epsilon-aminocaproic acid had a rebleed rate of 2.3% compared to 1 9.7% rebleed rate in appropriately selected controls. Patients treated with kanamycin and reserpine had a preoperative cerebral vasospasm rate of 32% compared to a 26% rate in controls; however, kanamycin and reserpine were found useful for decreasing the postoperative complications of cerebral vasospasm.