摘要:

Near-infrared spectroscopy is a technique used to monitor cerebral oxygenation. To validate the method, we measured regional oxygen saturation (rSo2) in the brains of 18 dead subjects (mean age, 74.4 ± 14.6 years) 19.8 ± 18.2 h (range, 1–73) after cessation of systemic circulation, and in 15 healthy probands (mean age, 34.2 ± 8.7 years) with an INVOS 3100 cerebral oximeter. The mean (±SD) rSo2in the dead subjects was 51.0 ± 26.8% [range, 6–88%; left, 48.4 ± 28.0% (n= 21); right, 54.4 ± 25.7% (n= 16)]. The mean rSo, in the control group was 68.4 ± 5.2% (range, 60–76%; left, 68.1 ± 5.0%; right, 68.7 ± 5.6%). After removal of the brain at autopsy in five of the dead subjects, the rSo2was 73.4 ± 13.3% (15 measurements). Six of 18 of the dead subjects had values above the lowest values found in the healthy adults (≥60%). These findings raise concerns about the validity of cerebral rSo2data in adults obtained by the INVOS 3100 system.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The purpose of this study was to evaluate arterial blood pressure and middle cerebral artery blood flow velocity in children during induction of anesthesia with sevoflurane. These measures were compared to findings in a control group anesthetized with halothane. Each child received mask induction of sevoflurane (n = 9) or halothane (n = 9) with 70% nitrous oxide in oxygen. Blood pressure was measured noninvasively by an oscillometric technique using a Dinamap. Blood flow velocity was measured using a transcranial Doppler with a 2-MHz probe. End-tidal CO2, nitrous oxide, and anesthetic concentrations were measured by a Datex Ultima Capnomac. Both sevoflurane (2.4%) and halothane (1.3%) combined with 70% nitrous oxide decreased blood pressure and increased cerebral blood flow velocity. Intubation increased blood pressure and further increased cerebral blood flow velocity with both anesthetic treatments. These results indicate that sevoflurane and halothane combined with nitrous oxide decrease blood pressure and increase cerebral blood flow velocity and suggest that sevoflurane produces cerebrovascular effects similar to those of halothane during anesthetic induction.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Cerebral vasospasm remains the principal cause of morbidity and mortality following successful clipping of intracranial aneurysms. Current management often requires subjective judgments concerning presumed abnormalities of cerebral blood flow. In this study, a combined intracranial pressure (ICP)-laser Doppler flowmetry (LDF) fiberoptic probe that permits continuous monitoring of local cerebral blood flow (1CBF) was used in the postoperative management of 20 aneurysm patients. Using this probe, 1CBF was simultaneously recorded and integrated on a real time basis with other physiological parameters, including ICP, systemic arterial pressure, pulmonary arterial pressure, central venous pressure, and pulse oximetry. The combined probe also provided the ability to obtain precise and detailed information concerning the presence or absence of cerebral autoregulation and CO2vascular reactivity, and allowed calculation of the cerebral vascular resistance. Continuous monitoring of 1CBF in this manner complemented by transcranial Doppler and angiographic data permitted early detection of cerebral ischemia, helped to differentiate cerebral ischemia from edema and hyperemia, was useful in titrating blood pressure and fluid management, provided direct feedback about the effectiveness of instituted therapies, and determined early on when medical management was of no avail and that interventional neuroradiology was indicated. Evidence is presented that the presence of angiographic vasospasm and increased velocities on TCD do not always correlate with ischemia in the microcirculation and that direct measurements of 1CBF are often at variance with calculations of cerebral perfusion pressure (CPP).

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

This report is the first to correlate data concerning intraoperative somatosensory evoked potentials (SSEPs) and local spinal cord blood flow (1SCBF) in patients with syringomyelia. In a consecutive study, bilateral median nerve SSEPs were recorded intraoperatively in 13 patients undergoing a syrinx shunt to the posterior fossa cisterns (syringocisternostomy). 1SCBF was measured in five of these patients using laser doppler flowmetry (LDF) calibrated in arbitrary units (AU). SSEP recordings obtained 30 min after syrinx decompression demonstrated a slight but consistent reduction of N20latencies (mean change: 0.53 ms right, p < 0.003; 0.58 ms left, p < 0.001) concurrent with a similar but less consistent increase of N20amplitudes (0.16 mV right, p = 0.256; 0.29 mV left, p = 0.03). Prior to shunting, LDF recordings from the spinal cord overlying syrinxes revealed very low 1SCBF values in five of five patients (mean LDF, 13.2 AU ± 15.3 SD). Immediately after shunting, there was a dramatic rise of 1SCBF (mean LDF, 241.2 AU ± 106.3 SD) associated with visualized hyperemia of the spinal cord and pial vessels. The 1SCBF fell to intermediate levels after 2 min (157.2 AU ± 33.0 SD) and remained at these levels during the interval of recording (5 min). Hyperventilation testing in two patients prior to shunting revealed no change in 1SCBF consistent with a loss of CO2vascular reactivity and a paradoxical increase of 1SCBF in one patient 5 min after shunting. Each patient in this study experienced neurological improvement in the immediate postoperative period associated with collapse or disappearance of the syrinx on magnetic resonance imaging scans. Because syrinx shunting results in an acute decompression of the distended spinal cord, it is possible that the rapid improvement of SSEPs reflects a relief of mechanical factors such as stretching and compression of nervous tissue. However, the LDF findings in this study suggest that distended spinal cord cavities are also capable of producing regional ischemia. A significant reduction of 1SCBF is a possible contributing cause of neurological injury and SSEP abnormalities. Intraoperative improvement of SSEPs and 1SCBF were found to correlate well with neurological recovery following syringocisternostomy. Our results indicate that SSEP monitoring can provide useful information during surgical procedures for syringomyelia and that further experience with LDF monitoring may provide insights into the pathophysiology of this condition.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Eight patients with normal-pressure hydrocephalus were studied. Intracranial pressure (ICP) and mean arterial blood pressure (MAP) were measured continuously before and during administration of ketanserin i.v. (10 mg bolus followed by an infusion of 3 mg over a 60-min period, 6 mg over the next 30 min, and 12 mg over the last 30 min). The mean baseline MAP and ICP were 103 and 8 mm Hg, respectively. Five minutes after the bolus dose, the maximum decrease in MAP occurred (mean, 17 mm Hg;p< 0.05). The maximum ICP (10 mm Hg) occurred at 5 min and at 100 min after the bolus dose but was not significantly different from the baseline value. There was no change in relative global cerebral blood flow (CBF) expressed as 1/(arteriovenous oxygen difference). It is concluded that ketanserin in a clinically recommended dose decreases blood pressure without significantly influencing the ICP or CBF.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

We report a case of cerebral infarction following traumatic brain injury associated with low cerebral blood flow, but not detected by measurements of jugular venous oxygen saturation, cerebral lactate production, cerebral perfusion pressure, transcranial Doppler ultrasound, or measures of systemic hemodynamics.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

During spinal surgery using a horseshoe headrest with the patient in the prone position, the possibility of central retinal artery occlusion (CRAO) increases, and its cause can be attributed primarily to excessive extraocular pressure, a very rare complication. This report describes a case of CRAO, occurring in an adult, after cervical syringomyelia surgery in which a horseshoe headrest was used.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

This study was designed to evaluate the ability of dexmedetomidine, an α2-adrenergic agonist, to attenuate increases in the hippocampal concentration of extracellular glutamate and glycine that result from episodes of transient global cerebral ischemia. After the induction of anesthesia with halothane and oxygen, microdialysis catheters were stereotactically inserted into the hippocampi of 16 New Zealand white rabbits. After the collection of baseline samples of dialysate, animals were randomly assigned to receive an intravenous infusion of either saline (n= 8) or dexmedetomidine (n= 8). Transient global cerebral ischemia was produced by the inflation of a neck tourniquet and induction of deliberate hypotension for 10 min. Dialysates were collected during the ischemic period and for the ensuing 60 min of reperfusion. During ischemia, the concentrations of glutamate and glycine increased from the preischemic baseline in both groups. Glutamate concentrations rapidly returned to baseline after reperfusion, whereas glycine concentrations remained elevated throughout the reperfusion period. There were no significant differences between the control and dexmedetomidine-treated groups. These results suggest that the mechanism of the putative neuroprotective effects of dexmedetomidine is not related to decreased concentrations of glutamate or glycine.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Thromboxane A2accumulates in the hippocampus after global ischemia and may play a key role in postischemic hypoperfusion. Thromboxane synthetase inhibitor (OKY-046) inhibits the accumulation of thromboxane A2and promotes prostacycline production. Therefore, we set out to determine whether the inhibition of thromboxane synthesis would ameriolate postischemic neuronal death. Three groups of six Mongolian gerbils were subjected to different treatments: untreated control, untreated ischemia, and treated ischemia. Immediately after forebrain ischemia, OKY-046 (10 mg/kg) was injected intraperitoneally into the treated group. After 7 days of survival, the histopathology of the brain was examined. Pyramidal cell density in the CA1 sector in the treated group was 147 ± 70 nuclei/mm (mean ± SD), which was significantly (p < 0.05) higher than that in the untreated group (33 ± 10 nuclei/mm). The findings were 231 ± 7 nuclei/mm for the control group. No significant difference was seen in the profile of temporal muscle temperature before and after ischemia between the groups. Ultrastructurally, the vessels in the CA1 sector showed lumen patency in the treated group, whereas occluded vessels with an extended perivascular space were observed in the untreated group. Thromboxane synthetase inhibitor thus partly ameliorates the selective vulnerability of the hippocampus after forebrain ischemia, suggesting that thromboxane A2is involved in the development of delayed neuronal death, independently of any thermal effect.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID