ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

It is well established that cerebral blood flow (CBF) is sensitive to variations in arterial PCO2(PaCO2) and can be influenced by changes in jugular venous return due to elevated intrathoracic pressure. Therefore, we compared cerebral CO, vasoreactivity when PaCO2was altered either by changing inspired PCO2or tidal volume. In addition, we sought to determine if noninvasive transcranial Doppler ultrasonography can be used instead of invasive CBF measurement to determine cerebral CO2vasoreactivity. In 36 mechanically ventilated patients in coma due to acute brain lesion, we evaluated CBF by continuous jugular thermodilution, middle cerebral artery flow velocity (Vm) by transcranial Doppler ultrasonography, intracranial pressure (ICP; in only 23 of them) by intraventricular catheter, systemic and pulmonary hemodynamic variables, and arterial and jugular bulb blood gases. Measurements were taken at four levels of PaCO2(25, 30, 35, and 40 mmHg) by modifying in a random order either tidal volume or inspired PCO2. Cerebral, pulmonary, and systemic hemodynamic changes were similar in magnitude during both methods of altering PaCO2. From the highest to the lowest PaCO2, CBF decreased from 61 ± 7 to 36 ± 4 ml/min/100 g (p < 0.001, mean ± SE), Vm from 89 ± 7 to 65 ± 5 cra/s (p < 0.001), and ICP from 29 ± 2 to 12 ± 2 mmHg (p < 0.001), but cerebral perfusion pressure remained constant, ranging from 65 ± 3 to 67 ± 4 mmHg (p = NS). Arteriojugular oxygen content difference increased from 3.2 ± 0.2 to 5.7 ± 0.4 ml/dl (p < 0.001). Eleven of the 20 patients with a preserved CBF response to CO2survived to 6 months, whereas only two of the 16 patients with an altered response were alive at 6 months (p < 0.05). When compared with CBF by jugular thermodilution, the rates of sensitivity and specificity of transcranial Doppler ultrasonography to detect impaired cerebral CO2vasoreactivity were 69% and 65%, respectively. In conclusion, the reduction of PaCO2from 40 to 25 mmHg by modifying either tidal volume or inspired PCO2resulted in similar effects on cerebral, pulmonary, and systemic circulations. Cerebral CO2vasoreactivity is of prognostic value in brain-injured patients when determined using CBF but may be misleading when evaluated using velocities measured by transcranial Doppler ultrasonography.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Several studies suggest that relative changes in cerebral blood flow (CBF) may be assessed via transcranial Doppler sonography (TCD). The present study investigates the correlation between changes in TCD-mean flow velocity (Vm) and changes in CBF in patients with a variety of types of intracranial pathology undergoing cerebrovascular reactivity tests. After informed consent was obtained, 32 patients presenting with stenoses of brain-supplying arteries (n = 13), cerebral vascular malformations (n = 6), surgical decompression for subarachnoid hemorrhage (n = 2), brain edema after closed head injury (n = 8), or hepatic encephalopathy (n = 3) were studied. The patients were divided into two groups for different reactivity tests. Patients in group 1 (awake or sedated, n = 18) received a 1-g dose of acetazolamide intravenously. In group 2 (n = 14), mechanical ventilation was adjusted to produce a 20% decrease in arterial CO2tension compared with baseline. Regional CBF was measured using xenon-enhanced computed tomography (Xe-CT). Xe-CT scans at the levels of the basal ganglia and the lateral ventricles were performed during a 4.5-min xenon wash-in period. Bilateral flow velocity was measured in the middle cerebral artery using a 2-MHz pulsed TCD system. Mean arterial blood pressure, heart rate, and endtidal CO2were continuously recorded during the procedure. After baseline measurements and either alteration of CO2or application of acetazolamide, the cerebrovascular reactivity was assessed at 20 min by a second measurement of CBF, TCD, and all other physiologic variables. The correlation coefficient for relative changes of MCA territory CBF versus Vm and for the overall population was r = 0.82. In groups 1 and 2, the r values were 0.39 and 0.5, respectively. Correlation coefficients did not exceed r = 0.4 in any subgroup-classification based on diagnosis. The close correlation between changes in CBF and Vm (r = 0.82) in patients with heterogenous intracranial pathology seems to show that TCD is a measure of CBF. However, in groups 1 and 2 and in subgroups formed of patients classified according to diagnoses, data dispersion suggests that the actual correlation is weaker. Relation of changes in Vm to those in CBF may depend on the underlying diagnosis. These data indicate that the correlation between Vm and CBF may vary with intracranial pathology.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Mild hypothermia and the 21-aminosteroids have both been neuroprotective in several models of cerebral ischemia. In this study we compared the effects of mild hypothermia and the 21-aminosteroid U-74389G, alone and in combination on neurologic and histopathologic outcome after temporary spinal cord ischemia. Forty male anesthetized New Zealand white rabbits were randomized to four groups (n = 10): (a) normothermia (control); (b) U-74389G (3 mg/kg intravenously [i.v.] before aortic occlusion, 1.5 mg/kg i.v. and 10 mg/kg intraperitoneally after occlusion); (c) mild hypothermia (4°C epidural temperature decrease); and (d) mild hypothermia combined with U-74389G. Spinal cord ischemia was produced by 40 min of infrarenal aortic balloon occlusion. Forty-eight hours after the procedure, the neurologic status of the animals was assessed (Tarlov score) and the animals were killed for histologie evaluation. In the normothermic control group, eight of 10 animals became paraplegic. There was a significant reduction of the incidence of paraplegia and overall neurologic deficits and a significant improved Tarlov score in the mild hypothermie group (one animal paraplegic) and in the group with both mild hypothermia and U-74389G (two animals with a mild paraparesis). The histopathologic scores showed significantly less damage in both hypothermie groups. In group 2, U-74389G administration did not improve neurologic or histopathologic outcomes. The results of the current study demonstrate that a slight decrease of intraischemic spinal cord temperature significantly improved neurologic and histopathologic outcomes after experimental spinal cord ischemia. Protection by the 21-aminosteroid at normothermic conditions, or additional protection when U-74389G was added to mild hypothermia, could not be demonstrated.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Closed head trauma (CHT) increases brain tissue prostaglandin E2 (PGE2) concentration, and that increase is associated with cerebral edema formation and worsening of the neurologic severity score (NSS). Injection of the bacterial endotoxin lipopolysacharride (LPS) increases cerebral and hypothalamic PGE2, and the hypothalamic increase is associated with increased body temperature. The present study determined (a) whether LPS-induced increase of PGE2 causes brain edema or worsens NSS and (b) whether CHT increases hypothalamic PGE2 and thereby increases body temperature. Halothane-anesthetized rats were divided into four groups: group 1 = surgery with no CHT and no LPS (n = 8); group 2 = surgery with LPS and no CHT (n = 8); group 3 = surgery with CHT and no LPS (n = 8); and group 4 = surgery with CHT plus LPS (n = 8). NSS was determined at 1 and 24 h after injury, and brain tissue PGE2 and edema were determined when animals were killed 24 h after injury. As compared with group 1, LPS alone, but not CHT or CHT plus LPS, increased rectal temperature. CHT and CHT plus LPS, but not LPS alone increased brain water content and worsened NSS. LPS, CHT, and CHT plus LPS all increased hypothalamic and cerebral PGE2 production. We conclude that although LPS and CHT increased PGE2 levels, LPS alone did not affect neurologic status or brain edema, CHT did not increase rectal temperature, and addition of LPS to CHT did not aggravate the sequelae of CHT.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

A case of severe cerebral head injury in a child, chronically treated with cyclosporine A after orthotopic liver transplantation, is presented. The initial Glasgow Coma Scale score after the motor vehicle accident was 3, and computed tomography showed multiple sites of intracerebral bleeding, an epidural hematoma, and signs of perifocal edema. Although these lesions are normally associated with a poor outcome, the child recovered unexpectedly well. In brain injury, a lucid interval can be followed by secondary neurologic deterioration due to a loss of high-energy metabolites, a release of neurotransmitters, and an increase in intracellular Ca2+. These events finally led to cell damage in the penumbra of an ischemic infarction. Among other drugs, immunosuppressants such as cyclosporine A have been shown to exhibit neuroprotective properties in experimental models if given during this time interval of secondary neurologic deterioration. Although human data on these effects are still lacking, we conclude that neuroprotective actions of cyclosporine A may have been involved in the favorable outcome in this 14-year-old boy.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The present series of experiments was performed to investigate the influence of acute intracranial hypertension on the upper limit (UL) of cerebral blood flow (CBF) autoregulation. Three groups of eight rats each—one with normal intracranial pressure (ICP) (2 mmHg), one with ICP = 30 mmHg, and one with ICP = 50 mmHg— were investigated. Intracranial hypertension was maintained by continuous infusion of lactated Ringer's solution into the cisterna magna, where the pressure was used as ICP. Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure (MABP) - ICP, was increased stepwise by continuous intravenous infusion of norepinephrine. CBF was calculated by the intracarotid133Xe method. In all three groups the corresponding CBF/CPP curve included a plateau where CBF was independent of changes in CPP, showing intact autoregulation. At normal ICP the UL was found at a CPP of 141 ± 2 mmHg, at ICP = 30 mmHg the UL was 103 ± 5 mmHg, and at ICP = 50 mmHg the UL was found at 88 ± 7 mmHg. This shift of the UL was more pronounced than the shift of the lower limit (LL) of the CBF autoregulation found previously. We conclude that intracranial hypertension is followed by both a shift toward lower CPP values and a narrowing of the autoregulated interval between the LL and the UL.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

This report describes a sudden decrease in blood pressure after conservative treatment of acute intracranial hypertension. A 63-year-old woman with acute hydrocephalus after undergoing clipping of an aneurysm of the right supracerebellar artery developed increased intracranial pressure, necessitating surgical management. On the operating table, the patient developed Cushing's reflex. Mannitol injection combined with hyperventilation was begun immediately to reduce her intracranial pressure. Fifteen minutes later, a sudden and prolonged suppression of circulation was observed (blood pressure 65/35–85/40 mmHg, heart rate 90–100 beats/min). Postoperatively, computed tomography of the head showed compression of the brain stem. We believe that this patient's blood pressure decrease was related to a sudden reduction of intracranial pressure and that mannitol injection was principally responsible for this occurrence.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Simultaneous and continuous recording and processing of different noninvasive neuromonitoring parameters were carried out, including spontaneous and evoked bioelectrical brain activities obtained by new “active electrodes,” transcranial Doppler sonographic measurements using robotic probes, a multiscan principle for three-dimensional transcranial Doppler imaging, and recording of near-infrared spectroscopic data. The recording and processing were carried out over periods of some hours with a new recording technique integrated in a helmet construction.

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID

ISSN:0898-4921    

出版商:OVID    

年代:1998

数据来源: OVID