Effect of Cerebral Ischaemia on the Cerebrovascular and Cardiovascular Response to Haemorrhage

Summary  Reports studying the combination of low blood pressure and cerebral ischaemia are few, and it remains to be determined how cerebral circulatory insufficiency modifies the cerebral perfusion and the central haemodynamic response to blood loss. We hypothesised that occlusion of arteries to the brain modifies the cerebrovascular and cardiovascular responses to blood loss. Continuous measurements of the cerebral microcirculation with laser Doppler microprobes in the cerebral cortex were performed in anaesthetised pigs during cerebral ischaemia and haemorrhagic hypotension. The response to rapid bleeding (25% of the blood volume) was recorded during normal conditions and during cerebral ischaemia induced by bilateral occlusion of the common carotid arteries. During normal conditions haemorrhage caused insignificant decreases in cerebral microcirculation. Haemorrhage during bilateral carotid artery occlusion, however, caused significantly greater changes in cerebral microcirculation and a greater posthaemorrhagic increase in cerebrovascular resistance shortly after the blood loss. Haemorrhage during bilateral carotid artery occlusion also caused greater reductions in cardiac output and arterial pressure than similar blood loss caused during normal conditions. This study showed a disproportionate decrease in cerebral blood flow with haemorrhage during bilateral carotid occlusion, caused by an immediate increase in cerebrovascular resistance. The results suggest that even a moderate blood loss in patients with impaired cerebral circulation could be dangerous, because normal compensatory mechanisms to haemorrhage are impaired.     

Is unilateral antegrade cerebral perfusion equivalent to bilateral cerebral perfusion for patients undergoing aortic arch surgery?

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was whether unilateral antegrade cerebral perfusion is equivalent to bilateral cerebral plegia for cerebral protection during aortic arch surgery. Altogether 233 papers were found using the reported search, of which 17 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. These papers documented antegrade selective cerebral perfusion in a total of 3548 patients: bilateral cerebral perfusion in 2949 patients and unilateral perfusion in 599 patients. Both methods of cerebral perfusion resulted in neurological injury rates of <5%, but the period of antegrade cerebral perfusion allowed by bilateral perfusion was significantly higher. While unilateral perfusion allowed around 30-50 min, bilateral perfusion allowed 86 to over 164 min of ASCP with an acceptably low CVA rate. Therefore, we conclude that while both methods are acceptable, once the ASCP time is expected to rise over 40-50 min, bilateral cerebral perfusion is the technique that is best documented to be safe.     

Radical surgery of a galenic aneurysm with regional cerebral blood flow analysis. A case report

Successful surgical treatment of a case of aneurysm of the vein of Galen is presented. An 11-month-old boy was admitted with episodes of convulsive attacks. Neuroradiological examination revealed an aneurysm of the vein of Galen filled by branches of posterior cerebral arteries and left thalamoperforating artery. Regional cerebral blood flow, which was measured by a method of xenon-enhanced computed tomography, showed a low flow area in the frontal and occipital regions. The aneurysm was approached through the bilateral parietooccipital interhemisphere, freed from the feeders, and ligated. During the operation, cortical blood flow was monitored for prevention of normal perfusion pressure breakthrough. After the feeders were successfully clipped, the blood flow increased and became normalized in the related cortex. There was no postoperative neurological deterioration.     

Assessment of sublingual PCO2 during selective cerebral perfusion

We monitored sublingual tissue PCO2 (PSLCO2) continuously with an ISFET (ion-sensitive field effect transistor) based PCO2 sensor during and after surgical treatment for descending aortic aneurysm. Using femoro-femoral bypass and a beating heart technique, distal end of aneurysm was clamped and then selective cerebral perfusion was performed into the left subclavian and left common carotid arteries. Aneurysmectomy and reconstructive surgery were carried out with proximal end of the left common carotid artery being clamped. Upon starting selective cerebral perfusion, PSLCO2 increased abnormally. PSLCO2 increased from 38 mmHg just after induction of anesthesia to the maximum value of 87 mmHg during selective cerebral perfusion. Three hours after arriving in the intensive care unit, the patient developed convulsion and anisocoria and the computed tomography showed cerebral infraction. Since the blood flow to the tongue is fed through the internal and external carotid arteries, the increase in PSLCO2 is supposed to be caused by the decrease of blood flow to the tongue during selective cerebral perfusion. The monitoring of PSLCO2 may be a useful method to estimate the brain blood flow during selective cerebral perfusion.     

不同体、脑灌注方式对StanfordA型主动脉夹层患者的脑保护研究

摘要：目的探讨不同的体、脑灌注方式对StanfordA型主动脉夹层患者脑保护的影响。方法回顾性分析哈尔滨医科大学附属第一医院2007年4月至2012年3月117例StanfordA型主动脉夹层手术患者的临床资料,依据不同的体、脑灌注方式将患者分为3组,组1：45例,股动脉插管行体循环灌注＋停循环后单侧或双侧顺行性脑灌注组;组2：38例,锁骨下动脉或无名动脉插管行体循环灌注和单侧顺行性脑灌注或双侧顺行性脑灌注组;组3：34例,锁骨下动脉或无名动脉插管＋股动脉插管行顺逆结合体循环灌注和单侧顺行性脑灌注或双侧顺行性脑灌注组。对比分析术后短暂性神经系统功能障碍（transientneurologicaldysfunction,TND）、永久性神经系统功能障碍（permanentneurologicaldysfunction,PND）的发生情况以及影响因素。结果组1脑部并发症发生率高于组2、组3（37．77％vs．13．16％vs．14．71％）,差异有统计学意义（P〈0．05）;组3体外循环的降温速度比组1、组2快（35．56±4．35VS．40．00±5．63、39．58_＋6．03）,差异有统计学意义（P〈0．05）;其他指标各组间差异无统计学意义（P〉0．05o结论顺行性、逆行结合的体外循环灌注方法联合顺行性脑灌注降温速度均匀快速,可能具有良好的脊髓、肾脏、腹腔器官的保护作用,特别是降低脑部并发症方面证明其是目前最佳的器官保护方法。     

Perfusion of naloxone through the fourth cerebral ventricle reverses the circulatory and hypnotic effects of halothane in dogs.

To determine whether naloxone when perfused through the cerebroventricular system would modify the circulatory and hypnotic effects of halothane, the authors studied its effect in six trained dogs. Naloxone, 20 microgram/ml, was perfused through the fourth cerebral ventricle in three and through the third cerebral and lateral ventricles in three other dogs when awake and during halothane anesthesia (0.75--0.82 vol per cent in oxygen). Blood pressure, heart rate, and circulatory responses to bilateral occlusion of the carotid arteries were measured. The state of consciousness was evaluated by the animals behavior and the EEG. Arterial hypotension, bradycardia, depressed baroreceptor responses, and EEG synchronization associated with halothane anesthesia were reversed when naloxone was perfused through the fourth ventricle. To maintain comparable depths of anesthesia the halothane concentration had to be doubled during naloxone perfusion. No change in the circulatory or hypnotic effects of halothane occurred when the third ventricle was perfused with naloxone. It is concluded that opiate receptors in structures bordering the fourth cerebral ventricle may be important modulators of inhalational anesthesia.     

单侧与双侧顺行性脑灌注的前瞻性随机对照研究

目的 比较全主动脉弓替换术中单侧顺行性脑灌注（ASCP）和双侧ASCP的脑保护效果。方法 16例全主动脉弓替换术病人随机分为单侧ASCP组和双侧ASCP组，每组各8例。两组均行术前、术后颅脑计算机体层摄影（CT）、术中均动态监测无名动脉及左颈总动脉压力，均行颈内静脉球血样血气分析。结果 两组各有1例出现短暂性神经功能异常。在ASCP期间单侧组无名动脉压高于左颈总动脉压（P〈0．01），而双侧组无名动脉压与左颈总动脉压相同。两组间各时间段颈静脉血氧分压、颈静脉血氧饱和度差异无统计学意义（P〉0．05）。结论 在基底动脉环完整，存在有效侧支循环条件下，单侧ASCP及双侧ASCP均能取得良好效果。单侧灌注操作较为简便，双侧灌注在ASCP期间两侧灌注压较为均衡，双侧灌注是否增加脑栓塞的危险尚需进一步研究。     

Does anatomical completeness of the circle of Willis correlate with sufficient cross-perfusion during unilateral cerebral perfusion?

OBJECTIVES: The aim of the study was to evaluate the role of anatomical completeness of the circle of Willis for sufficient brain perfusion during unilateral cerebral perfusion and the methodology of the preoperative and intraoperative functional assessments of adequate cross-perfusion. METHODS: This prospective observational study included all elective patients (99) who underwent elective open arch surgery (hemiarch in 74 and arch replacement in 25 patients, respectively) at our institution between September 2004 and September 2006. Preoperative neuro-vascular evaluation included color-coded duplexsonography of the extracranial arteries, cranial CT angiography, and transcranial sonography. A functional test of cerebral cross-perfusion was performed during cross-clamping of the common carotid artery during cannulation by transcranial Doppler, electroencephalography and measurement of somatosensory evoked potentials. These examinations, which were completed through measurement of arterial pressure in both radial arteries, also served as an intraoperative assessment of cerebral perfusion during surgery. During mild hypothermic (30 degrees C) circulatory arrest with a mean duration of 18 min (range, 7-70) brain protection using unilateral cerebral perfusion was performed in all patients. RESULTS: As assessed in preoperative CT angiography, the circle of Willis was complete in only 59 patients. Eighteen patients showed a singular abnormal location within the circle of Willis, 13 patients presented with abnormalities within the posterior communicating arteries on both sides, and 9 patients within the anterior and posterior communicating arteries. Nevertheless, functional tests during carotid artery cross-clamping as well as intraoperative cerebral monitoring including transcranial Doppler showed no pathology in any patient, and only one patient with severe aortic valve calcification suffered from embolic minor stroke after surgery. CONCLUSIONS: The anatomical status of the circle of Willis assessed with cranial CT angiography does not correlate with functional and intraoperative tests examining the cerebral cross-perfusion. The authors do not recommend cranial CT angiography as a preoperative standard examination before open arch surgery in which unilateral cerebral perfusion is scheduled.     

Total aortic arch replacement with a branched graft and limited circulatory arrest of the brain

BACKGROUND: Total replacement of the aortic arch is commonly performed with either antegrade perfusion of the brachiocephalic arteries by means of direct cannulation or with an interval of hypothermic circulatory arrest of at least 30 to 40 minutes. We present a technique with a branched graft that uses antegrade brain perfusion without the need for direct cannulation of the brachiocephalic arteries or a separate perfusion circuit, with only a brief period of circulatory arrest of the brain. METHODS: Twelve patients underwent resection of the aortic arch through either a midline sternotomy (4 patients) or a bilateral anterior thoracotomy (8 patients). The right axillary artery was used for arterial return and for brain perfusion. After establishing hypothermic circulatory arrest, the brachiocephalic arteries were detached from the aorta, flushed, and occluded with clamps. Hypothermic perfusion of the brain was established through the right axillary artery, and the brachiocephalic arteries were sequentially attached to the limbs of a branched aortic graft. Flow to the brain was then established in the antegrade direction through the axillary artery. RESULTS: The mean duration of circulatory arrest of the brain at a mean nasopharyngeal temperature of 16 degrees C was 8.8 minutes (range, 6-13 minutes). The subsequent period of hypothermic (20 degrees C-22 degrees C) brain perfusion, during which the 3 branches of the graft were attached to the brachiocephalic arteries, averaged 35 minutes (range, 23-44 minutes). All the patients survived the procedure and were discharged from the hospital. No patient sustained a permanent neurologic deficit. One patient had lethargy for 2 days, with full recovery. Nine of the 12 patients were extubated within 72 hours. CONCLUSIONS: This technique obviates the need for direct cannulation of the brachiocephalic arteries and for a separate perfusion circuit and requires only a brief period of circulatory arrest of the brain.     

A case of anterior communicating artery aneurysm with occlusion of the bilateral middle cerebral arteries

A patient with ruptured anterior communicating artery aneurysm associated with occlusion of the bilateral middle cerebral arteries is presented. A 70-year-old woman was hospitalized for sudden onset of severe headache and vomiting. She was alert, and no neurological deficit was found. CT scan showed a subarachnoid hemorrhage. Cerebral angiogram demonstrated occlusion of the bilateral middle cerebral arteries and ruptured anterior communicating artery aneurysm. After operation, she fully recovered and was able to walk at the time of discharge. In aneurysmal formation, we know from the literatures that hemodynamic stress plays an important role. In this case, occlusion of the bilateral middle cerebral arteries caused hemodynamic stress on the anterior cerebral arteries and anterior communicating artery. It is suggested that this is a causative factor of aneurysmal formation under systemic hypertension.     

Dissecting aneurysms at the bases of the brachiocephalic artery and the left common carotid artery due to localized dissection of the aortic arch; report of a case

A 43-year-old male lost consciousness immediately after archery practice, and was brought to our hospital by ambulance. Angiography showed dissecting aneurysms at the bases of the brachiocephalic artery and the left common carotid artery, causing compression of these arteries. Under cardiopulmonary bypass with selective cerebral perfusion, the blood supply to these arteries was restored with a bifurcated graft. Surgical specimen showed localized dissection of the aortic arch at the bifurcation to the brachiocephalic artery and the left common carotid artery, with the formation of dissecting aneurysms at the bases of both arteries. The aneurysms were filled with thrombi. In addition to these dissecting aneurysms, there were arterial dissections involving the brachiocephalic artery and the bilateral common carotid arteries. Histopathological examination of the vessel wall showed no evidence of atherosclerosis or vasculitis, and no abnormalities in the arrangement of elastic fibers.     

Coronary revascularization in patients with bilateral internal carotid occlusions

Coronary revascularization that is neurologically uneventful in patients with bilateral totally occluded internal carotid arteries has not been previously reported. We performed saphenous vein coronary artery bypass grafting on three such patients and observed them for 6 to 23 months. Preoperatively two of our patients had chronic stable symptoms of cerebrovascular insufficiency, and one had received cerebral revascularization via a superficial temporal-to-middle cerebral artery bypass. Controversy exists regarding proper cerebral protective maneuvers during coronary revascularization for patients with advanced cerebrovascular disease. Cerebral protection for our patients during cardiopulmonary bypass included hypothermia and high perfusion flows and pressures. Two patients also received prophylactic sodium thiopental. None of these three patients had a stroke perioperatively or during the follow-up period. We believe that these case histories strongly suggest that the functional state of the cerebral collateral circulation, as judged by preoperative neurological symptoms, predicts neurological outcome after coronary revascularization better than the specific occlusive anatomy of the extracranial carotid arteries.     

Optimal perfusion criteria for deep hypothermic selective cerebral perfusion in patients with aortic aneurysm involving aortic arch

Although selective cerebral perfusion (SCP) might be an useful supportive method for aortic arch surgery, its optimal perfusion criteria has not been established. We studied the relationship between the oxygen saturation of superior vena cava or internal jugular vein (SvO2) and the perfusion hemodynamics during deep hypothermic (DH) SCP in twenty patients (pts) (type A dissection; 10, arch aneurysm; 10). SCP was accomplished by perfusion to the brachiocephalic trunk (BCT) and the left common carotid artery (LCC) using separate pumps. Cardiopulmonary bypass and DHSCP time were 128-312 (222 +/- 43, mean +/- SD) minutes and 25-214 (122 +/- 49) minutes, respectively. The cerebral perfusion pressures (CPP) monitored at the bilateral temporal arteries were 20-60 (47 +/- 9) mmHg and cerebral perfusion flow (CPF) was 0.28-0.7 (0.43 +/- 0.10) L/min/m2. The cerebral perfusion score (CPS) defined as CPP X CPF was 7-39 (20 +/- 8). SvO2 ranged from 79 to 99 (94 +/- 7)%. Two operative deaths were encountered from unrelated causes to SCP in both cases. Cerebral infarction occurred in one patient possibly form prolonged low perfusion with low SvO2. When the safety range of SvO2 in DHSCP was defined as greater than 90%, essential criteria to keep this range was CPP greater than 40 mmHg. In 13 out of 15 pts with SvO2 greater than 90%, CPS were above 15. In conclusion, optimal perfusion criteria for DHSCP was defined as CPP greater than 40 mmHg and CPS(CPP X CPF) greater than 15 considering adequate cerebral oxygen consumption.     

Extrathoracic cannulation of the left common carotid artery in thoracic aorta operations through a left thoracotomy: preliminary experience in 26 patients

BACKGROUND: In aortic operations performed through a left thoracotomy, which require total bypass and deep hypothermic circulatory arrest, femoral artery cannulation is commonly used for arterial perfusion. This route limits the time of safe circulatory arrest and is associated with the risks of retrograde embolization or, in the case of aortic dissection, malperfusion of the vital organs. To overcome these problems, we have used cannulation of the extrathoracic left common carotid artery to ensure a central a route of arterial perfusion in these operations. The preliminary results are presented. METHODS: Between December 1999 and April 2001, we used left common carotid artery cannulation in 26 operations on the thoracic aorta performed through a posterolateral thoracotomy with an open technique during deep hypothermic circulatory arrest. Institutional review board approval and informed consent were obtained. The indications included perforating atherosclerotic ulcer (n = 5), chronic aortic aneurysm (n = 9), acute type B aortic dissection (n = 3), and chronic dissection of the thoracic aorta (n = 9). Transcranial Doppler ultrasonographic monitoring of both the right and left middle cerebral arteries was used to assess the adequacy of cerebral bihemispheric perfusion and to determine the differences in blood flow velocities throughout the procedure. RESULTS: Left common carotid artery cannulation was successful in all patients. All patients awoke from the operation, and none had cerebrovascular accidents. None died in the hospital, and complications related to carotid artery cannulation were not observed. None of the patients experienced postoperative paraplegia. In all patients transcranial Doppler monitoring indicated the absence of cerebral embolic phenomena throughout the entire procedure. Significant differences in middle cerebral artery flow velocities were observed at different phases of the procedures and between the right and left middle cerebral arteries during carotid cannulation and during selective cerebral perfusion. Nevertheless, the maximal drop of right middle cerebral artery blood velocity during selective perfusion through the left common carotid artery was within 50% of the left middle cerebral artery velocity, indicating adequate bihemispheric perfusion. CONCLUSIONS: In patients undergoing aortic operations through a left thoracotomy, extrathoracic left common carotid artery cannulation was a safe and effective means of providing proximal arterial inflow during cardiopulmonary bypass, which can be used to selectively perfuse the brain, as well as to prevent embolic phenomena in the arch vessels.     

Supratentorial dynamic computed tomography for the diagnosis of vertebrobasilar ischemic stroke

Dynamic computed tomography (CT) is an established method for the evaluation of perfusion in acute ischemic stroke, but is not frequently used to assess infratentorial ischemia. Eleven patients with vertebrobasilar ischemia underwent dynamic CT on admission and/or during the follow-up period. The time of appearance (TA) and time to peak (TTP) were mapped and differences in TA (deltaTA) and TTP (deltaTTP) between the bilateral middle cerebral artery and posterior cerebral artery (PCA) territories were calculated. Conventional angiography and brain imaging including CT and magnetic resonance imaging were also performed. The TA and TTP maps obtained within 48 hours after onset exhibited time delay in eight of nine patients in the bilateral PCA territories. deltaTA and deltaTTP were greater in patients with stenosis or occlusion of the bilateral vertebral arteries or the basilar artery, and in patients without collateral circulation via the posterior communicating arteries than in control subjects. Furthermore, TA and TTP normalized dramatically in patients with recanalization of the arteries. deltaTA and deltaTTP were also normalized. deltaTA and deltaTTP were negatively correlated with the time from onset to examination. Dynamic CT can provide important information in patients with vertebrobasilar ischemic stroke, and may allow the diagnosis of acute ischemia and monitoring of the course.     

Lethal thrombus in the carotid artery during operation for acute aortic dissection with cerebral malperfusion

A drowsy patient with acute type A aortic dissection and cerebral malperfusion required emergency operation. Because the right carotid artery was totally obstructed, cerebral perfusion was first restored by cannulating it and the left femoral artery before midline sternotomy. However, a long fresh thrombus was found flowing backward from the obstructed carotid artery. This thrombus was removed, and both arteries were connected through a Y-shaped extracorporeal circulation circuit to reperfuse the brain. During the subsequent aortic procedure, both arteries were used for arterial inflow. Such thrombi can cause grave postoperative neurologic dysfunction. Carotid artery cannulation is mandatory in such cases.     

Bilateral agenesis of internal carotid arteries

The authors present angiographic and computed tomographic demonstration of bilateral agenesis of internal carotid arteries. The patient was a seventy-six years old man who had been admitted to our hospital because of right hemisparesis and disorientation. In addition to the left chronic subdural hematoma, computed angiotomography showed the dilated basilar artery and dilated posterior communicating arteries. However, the bilateral internal carotid arteries were not recognized. Burr hole and irrigation were performed, then neurological deficits and symptoms were disappeared. Hematoma was 150 ml. Though axial transverse computed tomograms of base of skull demonstrated the absence of bilateral carotid canals. On aortography, the right common carotid artery and vertebral artery were supplied from the innominate artery and the left common carotid artery and vertebral artery were supplied from the left dilated subclavian artery. Bilateral retrograde brachial angiograms demonstrated the internal carotid circulation, which was supplied through bilateral dilated posterior communicating arteries. Basilar artery was also in a large caliber. Bilateral ophthalmic arteries were opacified from external carotid artery via the middle meningeal artery. Ten cases of bilateral agenesis of internal carotid arteries have been reported previously. The findings of angiograms and computed tomograms on the agenesis of bilateral internal carotid arteries were discussed. This anomaly is important on cerebral hemodynamics and embryology.     

A new rat model of chronic cerebral hypoperfusion associated with arteriovenous malformations

OBJECT: A new experimental model of chronic cerebral hypoperfusion was developed to study the effects of systemic arterial shunting and obstruction of the primary vessel that drains intracranial venous blood on cerebral perfusion pressure (CPP), as well as cerebral pathological changes during restoration of normal perfusion pressure. METHODS: Twenty-four Sprague-Dawley rats were randomly assigned to either a sham-operated group, an arteriovenous fistula (AVF) group, or a model group (eight rats each). The animal model was readied by creating a fistula through an end-to-side anastomosis between the right distal external jugular vein (EJV) and the ipsilateral common carotid artery (CCA), followed by ligation of the left vein draining the transverse sinus and bilateral external carotid arteries. Systemic mean arterial pressure (MAP), draining vein pressure (DVP), and CPP were monitored and compared among the three groups preoperatively, immediately postoperatively, and again 90 days later. Following occlusion of the fistula after a 90-day interval, blood-brain barrier (BBB) disruption and water content in the right cortical tissues of the middle cerebral artery territory were confirmed and also quantified with transmission electron microscopy. Formation of a fistula resulted in significant decreases in MAP and CPP, and a significant increase in DVP in the AVF and model groups. Ninety days later, there were still significant increases in DVP and decreases in CPP in the model group compared with the other groups (p < 0.05). Damage to the BBB and brain edema were noted in animals in the model group during restoration of normal perfusion pressure by occlusion of the fistula. Electron microscopy studies revealed cerebral vasogenic edema and/or hemorrhage in various amounts, which correlated with absent astrocytic foot processes surrounding some cerebral capillaries. CONCLUSIONS: The results demonstrated that an end-to-side anastomosis between the distal EJV and CCA can induce a decrease in CPP, whereas a further chronic state of cerebral hypoperfusion may be caused by venous outflow restriction, which is associated with perfusion pressure breakthrough. This animal model conforms to the basic hemodynamic characteristics of human cerebral arteriovenous malformations.     

Vasospasm assessed by angiography and computerized tomography.

In 44 consecutive cases of ruptured cerebral aneurysm, vasospasm was demonstrated pre- or postoperatively. These cases were examined by bilateral carotid angiography and computerized tomography (CT), and the relationship between the angiographically visualized distribution of vasospasm, the neurological symptoms, and infarction seen on CT was evaluated. Vasospasm occurred in only some intracranial portions of the cerbral arteries that were immersed in blood-stained cerebrospinal fluid. Angiographically, diffuse vasospasm extensively involving bilateral carotid systems indicated the gravest prognosis for patients. Vasospasm affecting one carotid system and the anterior cerebral arteries on the opposite side often produced permanent neurological deficits. On the contrary, when vasospasm was restricted to one carotid system or to bilateral anterior cerebral arteries, it was usually associated with temporary neurological symptoms; however, it always produced residual neurological symptoms if it extended to the ascending branches (M3) of the middle cerebral arteries. Computerized tomography definitely demonstrated a low-density area or infarction in the territory of the spastic arteries in 25 (71%) of 35 cases with vasospasm. A low-density area was always detected when vasospasm occurred in M3 segments.     

The significance of posttraumatic increase in cerebral blood flow velocity: a transcranial Doppler ultrasound study.

Using transcranial doppler ultrasonography, cerebral blood flow velocity was measured daily from both middle cerebral arteries in 121 patients who had suffered minor (n = 55), moderate (n = 16), or severe (n = 50) brain injury. Serial computed tomographic scans were performed to identify noncontusion-related infarction (NCI). Cerebral perfusion pressure was monitored continuously in 41 patients who had severe head injury; of these, 22 had continuous measurement of arterial and jugular bulb venous oxygen (SJO2) saturation. Abnormally high mean flow velocity (greater than 100 cm/s) was observed in 23 patients (minor injury, n = 3; moderate injury, n = 3; severe injury, n = 17), but was recorded only when cerebral perfusion pressure exceeded 60 mm Hg (P less than 0.0001). Fourteen patients who underwent SJO2 monitoring developed increased mean flow velocity (MFV). In 6, the arterial-jugular venous oxygen content difference (AVDO2) was below 4 ml/dl, indicating global cerebral hyperemia. All had bilateral elevation of MFV, and 6 of the 8 nonhyperemic patients (AVDO2, 4-9 ml/dl) had a unilateral increase of MFV (P = 0.018). Four of the 23 patients with increased MFV developed NCI, as compared with none of the patients without elevated MFV (P = 0.015). All patients with NCI had suffered severe brain injury, had unilateral elevation of MFV in the terriory of the relevant cerebral vessel, and had received therapy to correct reduced cerebral perfusion pressure (P = 0.008). NCI did not occur in any patient with increased MFV that was associated with global hyperemia.