Transcranial Doppler sonography within 12 hours after subarachnoid hemorrhage

Calcium and potassium channels in experimental subarachnoid hemorrhage and transient global ischemia

Healthy cerebrovascular myocytes express members of several different ion channel families which regulate resting membrane potential, vascular diameter, and vascular tone and are involved in cerebral autoregulation. In animal models, in response to subarachnoid blood, a dynamic transition of ion channel expression and function is initiated, with acute and long-term effects differing from each other. Initial hypoperfusion after exposure of cerebral vessels to oxyhemoglobin correlates with a suppression of voltage-gated potassium channel activity, whereas delayed cerebral vasospasm involves changes in other potassium channel and voltage-gated calcium channels expression and function. Furthermore, expression patterns and function of ion channels appear to differ between main and small peripheral vessels, which may be key in understanding mechanisms behind subarachnoid hemorrhage-induced vasospasm. Here, changes in calcium and potassium channel expression and function in animal models of subarachnoid hemorrhage and transient global ischemia are systematically reviewed and their clinical significance discussed.

Management of aneurysmal subarachnoid hemorrhage

OBJECTIVE

Acute aneurysmal subarachnoid hemorrhage (SAH) is a complex multifaceted disorder that plays out over days to weeks. Many patients with SAH are seriously ill and require a prolonged intensive care unit stay. Cardiopulmonary complications are common. The management of patients with SAH focuses on the anticipation, prevention, and management of these secondary complications.

DATA SOURCES

Source data were obtained from a PubMed search of the medical literature.

DATA SYNTHESIS AND CONCLUSION

The rupture of an intracranial aneurysm is a sudden devastating event with immediate neurologic and cardiac consequences that require stabilization to allow for early diagnostic angiography. Early complications include rebleeding, hydrocephalus, and seizures. Early repair of the aneurysm (within 1-3 days) should take place by surgical or endovascular means. During the first 1-2 weeks after hemorrhage, patients are at risk of delayed ischemic deficits due to vasospasm, autoregulatory failure, and intravascular volume contraction. Delayed ischemia is treated with combinations of volume expansion, induced hypertension, augmentation of cardiac output, angioplasty, and intra-arterial vasodilators. SAH is a complex disease with a prolonged course that can be particularly challenging and rewarding to the intensivist.

Correspondence between the time course of cerebral vasospasm and the level of cerebral dopamine-β-hydroxylase in rabbits

The aim of the study was to explore whether the biphasic time course of the vasospastic response following experimental subarachnoid hemorrhage is associated with any concomitant changes in the amount of cerebral dopamine beta-hydroxylase in the noradrenergic central nervous system. A single-hemorrhage animal model was used. Rabbits were sacrificed from day 1 to day 8 after subarachnoid hemorrhage. Intimal corrugation of the basilar artery and the amount of cerebral dopamine beta-hydroxylase in the hypothalamus and brain stem were measured each day. Vasospastic changes occurred in the biphasic manner following subarachnoid hemorrhage. More profound vasospastic corrugation occurred in the acute phase, followed by a slightly less intense corrugation in the chronic phase (between days 5 and 8 after the subarachnoid hemorrhage). Simultaneously, a clear concomitant biphasic time course developed in the form of an increased amount of dopamine-beta-hydroxylase in the noradrenergic nervous system of the rabbit hypothalamus and brain stem during the acute and chronic phases after the subarachnoid hemorrhage. Statistically significant correlation between basilar artery corrugation and the amount of dopamine beta-hydroxylase was found. These results suggest the possible role of the central sympathetic system in the pathogenesis of vasospasm. At the same time, this study demonstrates the chronological similarity of the vasospastic development after subarachnoid hemorrhage in the animal experimental model with the human time course of vasospasm.

Early transcranial Doppler after subarachnoid hemorrhage: clinical and radiological correlations

BACKGROUND

The initial decrease in the level of consciousness after subarachnoid hemorrhage (SAH) is commonly considered secondary to cerebral hypoperfusion and metabolic depression. Age, intracranial pressure, and the amount of cisternal blood are closely related to the clinical grade on admission after SAH. Transcranial Doppler (TCD) may partially and indirectly estimate cerebral blood flow through analysis of flow velocity in the middle cerebral artery (MCA). Besides, pulsatility index (PI) can also be considered an indirect estimator of cerebrovascular resistance. The objective of this study was to determine the TCD parameters in the early stage after SAH and to analyze their correlation with the main clinical and radiological variables on admission.

METHODS

A series of 52 consecutive patients diagnosed with SAH, with an abnormal computed tomography (CT) scan on admission and a TCD performed in the first 24 hours from the onset of the hemorrhage, were retrospectively reviewed. Age, sex, clinical grade, presence of cisternal blood or hydrocephalus on initial CT scan, and parameters of TCD examination were recorded for every patient. The relationship between sonographic and clinical and radiological variables was evaluated by partial correlation test, Kruskal-Wallis, and Student t test for paired samples.

RESULTS

There were no significant differences in blood flow velocities or PIs between the left and right sides. Lower velocities and higher PIs correlated with a worse clinical condition at admission. Lower velocities also correlated with larger amounts of cisternal blood on the initial CT scan. No significant correlation was observed between PI and the amount of blood in the initial CT scan.

CONCLUSIONS

A global decrease in blood velocity in the MCA along with a rise in PI is present in the first 24 hours after SAH. These changes correlate with the clinical deterioration and partially with the amount of blood in the initial CT scan. These findings support the hypothesis that low cerebral perfusion caused by high intracranial pressure leads to diffuse ischemic changes in the early phase of SAH.

The relation between cerebral blood flow velocities as measured by TCD and the incidence of delayed ischemic deficits. A prospective study after subarachnoid hemorrhage

Patients (n = 127) with aneurysmal subarachnoid hemorrhage (SAH) were examined by transcranial Doppler ultrasonography (TCD) in a prospective study to follow the time course of the posthemorrhagic blood flow velocity in both the middle cerebral artery (MCA) and in the anterior cerebral artery (ACA). Results were analysed to reveal their relationship and predictive use with respect to the occurrence of delayed ischemic deficits. Mean flow velocities (MFV) higher than 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA were interpreted as indicative for significant vasospasm. In 20 of our 127 patients (16%) a delayed ischemic deficit (DID) was subsequently diagnosed clinically (DID+ group). Patients in the DID+ group can be characterized as those individuals who presented early during the observation period post-SAH with highest values of MFV, a faster increase and longer persistence of pathologically elevated MFV-values (exceeding 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA). They also show a greater difference in MFV-values if one compares the operated to the nonoperated side. Differences in MFV-values obtained in MCA or ACA were statistically significant (p < 0.05) for DID+ and DID- patients. The daily maximal increase of MFV was found between days 9 and 11 after SAH. In the DID+ group, the maximal MFV was 181 +/- 26 cm sec(-1) in MCA and 119 +/- 14 cm sec(-1) in ACA. In contrast to this, patients in the DID- group were found to present with MFV of 138 +/- 11 cm sec(-1) in MCA and 100 +/- 7 cm sec(-1) in ACA respectively. Delayed ischemic deficits appeared three times more often in DID+ patients than in patients with MFV < 120 cm sec(-1), if they showed a MFV > 120 cm sec(-1) in MCA. If pathological values were obtained in ACA, this ratio increases to about four times, if DID + patients presented with MFV > 90 cm sec(-1) versus patients with MFV < 90 cm sec(-1). Daily monitoring of vasospasm using TCD examination is thus helpful to identify patients at high risk for delayed ischemic deficits. This should allow us to implement further preventive treatment regimens.

The efficacy of papaverine administration by different routes for the treatment of experimental acute cerebral vasospasm

OBJECTIVE

To compare the effect of papaverine (PPV) by different routes of administration for the treatment of experimental acute cerebral vasospasm.

METHODS

A rabbit model of acute cerebral vasospasm induced by autologous blood injected into the basilar and prepontine cistern was used. The PPV (2mg/kg) was injected either by an intravenous (IV), intra-arterial (IA), intra-cisternal (IC), or combination of intra-arterial and intra-cisternal (IA+IC) routes. Basilar artery diameters were measured before and after vasospasm was induced and after PPV treatment.

RESULTS

Induction of vasospasm reduced basilar artery diameters by more than 50% in all animals. Compared to artery diameters before vasospasm, diameters after PPV treatment via the IV route were only reduced by 0.5+/-4.7%. Other reductions in the diameter included 29.1+/-10.4%, about 1.8+/-3.1%, and about 26.7+/-8.4% in the IA, IC, and IA+IC groups, respectively. However, IA administration of PPV caused obvious side effects.

CONCLUSION

Intra-arterial application of the PPV was the most effective way to treat vasospasm in this study. The efficacy of IC route in our study did not confirm the results of prior study. The possibility of side effects of PPV via the IA route should be considered before clinical application.

Accuracy of transcranial color Doppler ultrasonography in the diagnosis of middle cerebral artery spasm determined by receiver operating characteristic analysis

OBJECT

The value of transcranial Doppler ultrasonography for the detection of middle cerebral artery (MCA) spasm has been asserted. None of the published studies, however, has adequately scrutinized the overall diagnostic accuracy of this procedure. There are only sporadic reports concerning the utility of transcranial color Doppler (TCCD) ultrasonography, although this method has been proved to be more precise. In this study the authors attempted to estimate the performance of TCCD ultrasonography in detecting MCA narrowing by using receiver operating characteristic (ROC) curve analysis, based on TCCD studies obtained in a relatively large, randomly selected population of patients.

METHODS

Transcranial color Doppler ultrasonography studies were obtained in 100 consecutive patients (54 men and 46 women ages 18-74 years, median age 50 years) routinely referred by neurosurgeons for intraarterial angiography. The M1 segment of the MCA was insonated using a 2.5-MHz probe via a temporal acoustic window, and angle-corrected flow velocities were obtained. Angiographically depicted vasospasm was graded as none, mild (< or = 25% vessel caliber reduction), and moderate to severe (> 25% vessel caliber reduction). The effectiveness of TCCD ultrasonography in diagnosing MCA spasm was evaluated by calculating the areas under the ROC curves (Az). Of the 200 MCAs examined, 173 were successfully visualized with the aid of TCCD ultrasonography. Mild vasospasm was angiographically diagnosed in 15 arteries and moderate-to-severe vasospasm in 28. The best-performing TCCD parameter for the detection of MCA narrowing was revealed to be peak systolic velocity. The Az value for moderate-to-severe vasospasm only was 0.93 and that for all vasospasms was 0.8. The best efficiency, that is, the optimal tradeoff between sensitivity and specificity in diagnosing vasospasms, was associated with a peak systolic velocity of 182 cm/second.

CONCLUSIONS

The performance of TCCD ultrasonography in the diagnosis of advanced MCA narrowing is very good, and is acceptable for all vasospasms. The best-performing parameter was peak systolic velocity.

The role of transcranial Doppler in the management of patients with subarachnoid haemorrhage--a review

Introduced 15 years ago, transcranial Doppler (TCD) recordings of blood-velocity in patients with recent subarachnoid haemorrhage (SAH) have two objectives: to detect elevated blood velocities suggesting cerebral vasospasm (VSP) and to identify patients at risk for delayed cerebral ischemic deficits (DID). The pathophysiological cascade causing DID is complex. Discrepancies between blood velocities and DID (presuming that there actually is an "ischemic threshold" for blood velocity in absolute terms, which seems most unlikely) have been demonstrated, particularly in patients with elevated intracranial pressure (ICP) levels. Furthermore, the vessel showing the highest blood velocity is not always the one perfusing the area where ischemic symptoms arise, nor does the site of the greatest subarachnoid blood clot always relate to the ischemic brain region. Moreover, it is probable that the complex haemodynamic changes following SAH and the subsequent development of VSP may be underestimated if only considering the crude intracranial artery blood velocities. Cerebral blood flow measurements combined with TCD to assess both flow and velocity have emphasised this point. Despite these findings and ignoring the basic principles of cerebral haemodynamics, cerebral vasospasm is still being assessed from the intracranial velocity measurement alone. The addition of at least a careful measurement from the extracranial internal carotid artery--using the same TCD equipment and taking only a few short minutes to perform--allows a much more accurate assessment of the degree and the effects of vasospasm. This probably explains why the clinical value of TCD is still debated. There is still uncertainty as to the best method to prevent and to treat VSP, and the overall outcome after SAH depends on so many factors besides VSP. Conclusive evidence may therefore be hard to obtain, and it appears sound to conclude that even with advanced investigation technology available, proper selection, pre- peri- and postoperative care and timing of surgery remain cornerstones in the management of these patients,--equal in importance to their treatment in the operating room or in the interventional angiography suite.

Vasospasm diagnosis: theoretical and real transcranial Doppler sensitivity

In 40 patients middle cerebral artery trunk (M1) flow velocity was recorded just before 54 carotid angiography in 54 cases exhibiting vasospasm after aneurysm rupture. Angiographic vasospasm distribution was studied; cases of symptomatic vasospasm were noted and were compared with transcranial Doppler data. Angiographic vasospasm was present in M1 in 41/54 carotid angiograms. Postulating that all the cases of M1 angiographic vasospasm should be identified by transcranial Doppler, the theoretical sensitivity of TCD was 76%. In this series however the real sensitivity of TCD in vasospasm diagnosis was only 70%: besides 13 cases where vasospasm was not present in M1 (mainly after ACoA Aneurysm rupture), TCD failed to identify 3 cases of M1 angiographic vasospasm. Vasospasm may not be located in M1 even when severe and symptomatic (4 cases in this series). Transcranial Doppler remains a mediocre tool for identifying vasospasm after anterior communicating artery aneurysm rupture (sensitivity: 55%). Its reliability is better after internal carotid aneurysm rupture (sensitivity: 72%) and excellent after middle cerebral artery aneurysm rupture (sensitivity: 93%). In order to test the drugs or methods used to prevent or combat vasospasm, angiography has to be considered when during the vasospasm risk period TCD does not demonstrate vasospasm in M1, either in patients in whom clinical deterioration is occurring without other obvious explanation, or in all patients.

Cerebral vasospasm and free radicals

The literature implicating free radical reactions in the genesis of cerebral vasospasm following aneurysmal subarachnoid hemorrhage is reviewed. While this condition has features of a prototypical free radical-mediated disease and a plausible theory can be outlined, data to support the theory are limited. An association of lipid peroxidation with vasospasm has been observed, but more sophisticated techniques for detection of free radicals and for detection of free radical damage to arterial wall proteins and nucleic acids have not been used. There are conflicting reports about efficacy of various antioxidant treatments for vasospasm. In these studies, concomitant experiments have usually not confirmed that the treatments have decreased free radicals or lipid peroxides in cerebrospinal fluid. Because smooth muscle contraction is involved in vasospasm, it would be interesting to investigate the actions of free radicals on smooth muscle cells using, for example, isometric tension recordings and patch clamp techniques. Studies of cardiac myocytes indicate that free radicals alter conductances through potassium and calcium channels and through the sodium-calcium exchanger and may result in elevations in intracellular calcium. Few studies have been performed on cerebral smooth muscle cells. In one study, exposure of cerebrovascular smooth muscle cells to free radicals resulted in increased outward currents, decreased membrane resistance, cell contraction, appearance of membrane blebs, and cell death. In summary, more investigations using better experimental techniques are required before free radicals and reactions induced by them can be said with certainty to be the primary cause of vasospasm.

Transcranial Doppler in neurosurgery

This chapter describes the use of the transcranial Doppler apparatus in neurosurgery. The principles of Doppler insonation, the techniques of recording and the use of activation techniques is described. The relationship between blood flow and blood velocity is discussed, and the interaction of various pharmacological agents. The establishment of normal values for the laboratory and various vessels insonated is emphasised. The use of indices particularly the pulsatility index is described together with its variations. Cerebral vascular reactivity measurements and the interaction of Doppler recordings with raised intracranial pressure, useful in assessment of cerebral perfusion pressure as in head injury and in terminal cases, is documented. The use of transcranial Doppler in management of head injury and subarachnoid haemorrhage is described. The latter is probably the most useful routine place for Doppler measurement in neurosurgical practice and the documentation of the onset and progress of vasospasm is the final portion of the chapter.

Correlations between cerebral arterial velocities, blood flow, and delayed ischemia after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Elevated middle cerebral erythrocyte velocities and tissue hypoperfusion have been correlated with delayed ischemia after subarachnoid hemorrhage, but few studies have compared serial arterial velocities with cerebral blood flow and neurological deficits.

METHODS

Serial measurements of middle cerebral velocities, using transcranial Doppler ultrasonography, were performed in 34 patients after subarachnoid hemorrhage and correlated with cerebral blood flow, measured in 20 of the 34 using single-photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime and neurological evidence of delayed ischemia.

RESULTS

In 16 patients without delayed ischemia, eight had evidence of vasospasm (greater than 120 cm/sec), but only one of seven had hypoperfusion, suggesting that vasospasm might be more common than hypoperfusion in this group (p = 0.1). In 10 patients with delayed ischemia and a lateralizing deficit, both asymmetrical middle cerebral vasospasm (eight of nine with vasospasm) and hypoperfusion (six of six studied) were concordant with the clinically ischemic hemisphere (p less than 0.05). Vasospasm occurred with nonlateralized delayed ischemia in seven of eight patients and with hypoperfusion in five of six, affecting the anterior cerebral territory in three.

CONCLUSIONS

Concordant vasospasm and hypoperfusion were most often present in patients with delayed ischemia and lateralizing neurological deficits. Discordant results reflect inherent limitations and the different levels of the circulation monitored by the two techniques.

Cerebral blood flow and intracranial pressure during experimental subarachnoid haemorrhage

The relationships of intracranial pressure (ICP), systemic blood pressure (SBP) and cerebral blood flow (CBF) during experimental subarachnoid haemorrhage were investigated in cats. Continuous monitoring of regional cerebral blood flow (rCBF) was done by a thermal diffusion method using a Peltier stack. During haemorrhage ICP rose within 5.4 +/- 0.97 minutes from 10.5 +/- 4.9 to 176.1 +/- 27.8 mmHg. This strong increase of ICP resulted in a temporary arrest of cerebral circulation. The Cushing response during the haemorrhage could not improve the cerebral circulation, but in contrast caused a further increase of ICP. After the haemorrhage the cerebral blood flow normalised within minutes. It is concluded, that the Cushing response during a subarachnoid haemorrhage should be regarded as a deleterious rather than a beneficial mechanism.

Longitudinal time course of reversible and irreversible components of chronic cerebrovasospasm of the rabbit basilar artery

Multiple injections of autologous blood were made around the basilar artery of rabbits through a silicone catheter placed into the prepontine cistern. The total blood injected was 3 ml/kg in aliquots of 0.5 to 0.8 ml over a 4-hour period. Control angiograms were obtained 7 days before this procedure. Groups of animals were examined by angiography on each of 9 days after the injections of blood. An angiogram was obtained 15 minutes after the first injection of blood, 20 seconds after the intra-arterial injection of a maximum dilating dose of papaverine. All surviving animals showed basilar artery narrowing, which was greatest 24 hours after the hemorrhage, when the vessel diameter was reduced to 54% of the control value. The narrowing then decreased to a reduction of about 30%, which was maintained throughout the rest of the study period. A papaverine-resistant component of narrowing was not seen until the 3rd day. It increased progressively to Day 9 when it represented 63% of the total. This model has a number of features that are reminiscent of human cerebrovasospasm, including the fact that there is an initial phase of narrowing that is completely reversed by an intra-arterially administered vasodilator, and a second phase beginning on Day 3 which exhibits a progressively increasing papaverine-resistant component.

Haemodynamic considerations in the management of patients with subarachnoid haemorrhage

Cerebral vasospasm occurs, following subarachnoid haemorrhage, in the majority of patients and is accompanied by cerebral ischaemia in 30%. The objectives of this article are to review (1) the effects of subarachnoid haemorrhage and vasospasm on cerebral blood flow (CBF); (2) the effects of induced hypotension and hypocapnia on CBF in these patients; (3) current therapy for cerebral ischaemia from vasospasm. The medical literature was searched using Index Medicus; for the period 1983-90 this search was done on a computer with the CD-ROM version of Index Medicus, Silver Platter. Papers were selected on the basis of validity and applicability to clinical practice; animal studies are included when human data is lacking. Cerebral vasospasm may decrease cerebral blood flow, disturb autoregulation and place the patient at risk for delayed cerebral ischaemia. Intraoperative induced hypotension and hypocapnia can decrease CBF further, although effects of either on outcome have not been evaluated. Calcium antagonists are effective for both the prevention and the treatment of delayed cerebral ischaemia. Of the mechanical treatments, systemic-arterial hypertension has the firmest scientific foundation, although this is frequently combined with haemodilution and blood volume expansion. There is a need for randomized clinical trials to assess the efficacy of these latter treatments.

Correlation of transcranial Doppler sonography findings with timing of aneurysm surgery

Thirty-six patients with a proven first subarachnoid hemorrhage (SAH) from a ruptured supratentorial aneurysm were subjected to repeated transcranial Doppler sonography assessments. Eighteen individuals (Group A) were operated on within 48 hours, while the other 18 (Group B) had surgery between 49 and 96 hours after SAH. The patients represented two clinically comparable groups. In the first 72 hours post-SAH, no increased flow velocities suggestive of arterial narrowing or vasospasm were recorded. There was no significant difference in preoperative flow velocities between the groups. Postoperative flow velocities were significantly lower in patients operated on within 48 hours (p less than 0.001). Two patients, who had surgery on Day 4 post-SAH and who showed the highest recorded postoperative flow velocities, died from cerebral vasospasm and infarction. The results favor a referral system which enables early surgical intervention not only to prevent rebleeds but also aimed at reducing delayed ischemic dysfunction.