ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Transcranial Doppler (TCD) ultrasonography has been used in a variety of clinical contexts to assess cerebrovascular reserve by measuring carbon dioxide reactivity. Reproducibility with time and altered position of the patient is examined in the present study. Carbon dioxide reactivity was determined in 10 healthy volunteers using TCD. Hypocarbia was produced by voluntary hyperventilation, and hypercarbia was produced by rebreathing from a circuit primed with 7% carbon dioxide. Each patient was studied in the supine position twice (1 week apart) and once in the seated position. Carbon dioxide reactivity was determined from linear regression analysis of paired middle cerebral artery flow velocity and end-tidal carbon dioxide values. Analysis of covariance for repeated measures was used for statistical analysis. Both the absolute slope and the relative slope (absolute slope expressed as a percentage of flow velocity at 40 mm Hg) were compared. In the supine position, flow velocity, absolute and relative slopes, and mean arterial pressure were similar from one week to the next at all carbon dioxide levels. In contrast, flow velocity, mean arterial pressure (adjusted for hydrostatic gradient), and absolute slope were decreased in the seated position (p< 0.05). No difference was observed when the relative slope was used for comparison. We conclude that absolute carbon dioxide reactivity is reproducible over time but may be influenced by position. Relative reactivity (relative slope), however, was both time and position independent.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

This study was carried out to evaluate the effects of perioperative indomethacin on intracranial pressure (ICP), cerebral blood flow (CBF), and cerebral metabolism. Twenty patients subjected to craniotomy for supratentorial cerebral tumors were anesthetized with thiopental, fentanyl, nitrous oxide, and isoflurane. A Paco2level averaging 4.8 kPa (median) was achieved. The patients were randomized to intravenous indomethacin 50 mg or placebo administrated after exposure of the dura. ICP was measured continuously subdurally with a 22-gauge canula connected to a transducer. CBF and the arteriovenous difference of oxygen (AVDO2) were measured twice, before and after indomethacin/placebo administration. A significant decrease in ICP from 6.5 to 1.5 mm Hg (median) was found after indomethacin administration. This decrease was caused by a significant decrease in CBF associated with a significant increase in AVDO2. Indomethacin did not affect the cerebral metabolic rate of oxygen, the arteriovenous difference of lactate, or the lactate/oxygen index, suggesting that indomethacin did not provoke global cerebral ischemia. In the indomethacin group, dura was sufficiently relaxed in eight of nine patients and dura was opened without the occurrence of cerebral swelling. In one patient, mannitol treatment was necessary to prevent dural tightness. In the placebo group, mannitol supplemented with hypocapnia was applied in five patients. These findings suggest that perioperative treatment with indomethacin is an excellent treatment of intracranial hypertension during normocapnic isoflurane anesthesia for craniotomy.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The aim of the study was to evaluate a new noninvasive transcranial near-infrared spectroscopy (TNIRS) technique for determination of the lower limit of cerebral blood flow (CBF) autoregulation by comparing this technique with the standard cerebral arteriovenous oxygen saturation difference (AVDo2) method. In eight healthy volunteers, mean arterial blood pressure was increased by infusion of angiotensin and decreased by the combination of lower-body negative pressure and labetalol. For each 5-mm Hg change in mean arterial pressure, blood was sampled from the bulb of the internal jugular vein and a radial artery, and simultaneously, the oxygen saturation of hemoglobin in the brain was measured with an INVOS 3100 Cerebral Oximeter (Somanetics). The lower limit of autoregulation was then calculated by a computer using (a) AVDo2and (b) the difference between arterial oxygen saturation and the saturation determined with the cerebral oximeter (ACDo2). The median lower limit of autoregulation determined by the two methods was 73 and 78.5 mm Hg, respectively (p> 0.05). A statistically significant correlation between relative CBF (percentage of baseline) determined with the two methods was found below the lower limit of autoregulation (1/AVDo2= 12 + 0.8 ± 1/ACDo2;r= 0.55;p< 0.001). For all the 98 pairs of saturations registered, the correlation was 0.37 (p< 0.001), the mean difference was 16%, and the limits of agreement were −2.2 and 33.8%. We conclude that the cerebral oximeter might be useful in evaluation of the lower limit of cerebral autoregulation. This method, however, is of no value for estimation of levels of global cerebral oxygen saturation.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Access to the central venous circulation is often necessary in patients who have elevated intracranial pressure. It has been suggested that a disadvantage of the internal jugular vein approach to the central circulation may be an elevated intracranial pressure. The purpose of this prospective study was to evaluate the effect of right internal jugular vein cannulation on intracranial pressure in patients who are at risk of intracerebral hypertension. Eleven adult patients studied in the intensive care unit were evaluated. The population included those patients who were admitted to the neurosurgical intensive care unit requiring intracranial pressure monitoring and central venous access. With the intracranial pressure monitor in place, patients were put in supine and 30° head-up positions while intracranial pressure was recorded. The Queckenstedt maneuver was performed on all patients. A central venous line was then placed in the right internal jugular vein, and intracranial pressure was recorded. The Queckenstedt maneuver was again performed in the study population, and intracranial pressure measurements were recorded for the right, left, and bilateral compression of the internal jugular vein. The results of the intracranial pressure measurements before and after placement of the central venous line were statistically analyzed using single-factor analysis of variance over time. The mean Glasgow coma and Apache II scores for the study groups were 8 ± 4 and 15 ± 6, respectively. There were no significant differences in heart rate; cerebral perfusion pressure; or systolic, mean, or diastolic pressures throughout the study period. There was no statistical difference found between the intracranial pressures at any time point throughout the study. Furthermore, no difference was found in percentage change from baseline intracranial pressure data throughout the study period. Our results suggest that cannulation of the right internal jugular vein is a safe approach to the central circulation in patients at risk of intracranial hypertension. A description of the possible accommodating mechanisms are outlined.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

After spinal cord injury, quadriplegic patients generally require tracheostomy for ventilatory support and airway clearance. Early tracheostomy has several advantages over translaryngeal intubation, but in patients who undergo anterior surgical fixation of the spine, it is often delayed until after recovery of the surgical wound. We report the case of a quadriplegic patient who underwent a successful percutaneous dilational tracheostomy with the Ciaglia technique after surgical fixation of the spine. The percutaneous dilational technique minimizes the injury to the adjacent structures of the neck and the risk of stomal infection. Therefore, it should be considered the technique of choice when an early tracheostomy is indicated for quadriplegic patients who have undergone anterior surgical fixation of the cervical spine.

ISSN:0898-4921    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

While intravenous and volatile anesthetics have widely differing effects on cerebral blood flow (CBF), clinical studies suggest that the relative differences in their effects on intracranial pressure (ICP) may be smaller. Because acute changes in ICP are determined primarily by changes in cerebral blood volume (CBV), we compared the impact of propofol, pentobarbital, and isoflurane on CBF and CBV in rats. Equipotent doses of the three agents were determined by tail-clamp studies. Animals were then anesthetized with propofol (20 mg/kg load, 38 mg ± kg-1± h-1infusion), pentobarbital (30 mg/kg load, 20 mg ± kg-1± h-1infusion), or isoflurane 1.6–1.8%. Two hours later, CBF and CBV were measured using3H-nicotine as a CBF tracer, and14C-dextran and99mTc-labeled red cells as markers for cerebral plasma and red blood cell volumes (CPV and CRBCV), respectively. Total CBV was the sum of CPV and CRBCV. CBF was 2.0–2.6 times greater with isoflurane than with propofol or pentobarbital (137 vs. 67 and 52 ml ± 100 g-1± min-1, respectively). By contrast, while CBV was greater in the isoflurane group than in either the propofol or pentobarbital groups, the magnitude of the intergroup differences were much smaller (propofol = 2.49 ± 0.28 ml/100 g; pentobarbital = 2.27 ± 0.15 ml/100 g; isoflurane = 2.77 ± 0.24 ml/100 g, mean ± SD). These results suggest that the simple measurement of CBF may not adequately describe the cerebrovascular effects of an anesthetic, at least with respect to predicting the magnitude of the agents likely effects on ICP.

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

摘要:

The workup that I would recommend of a patient with a single TIA and an 80% carotid stenosis would include carotid ultrasound combined with MRA. If these studies correlated, then I would proceed with carotid endarterectomy after medicine or cardiology consultation and workup for coronary artery disease.

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