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 10,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A prospective observational study was performed to assess the reliability of fibreoptic oximetric catheters and to identify the incidence and causes of jugular bulb oxygen desaturation in patients with acute closed head injury. There were twenty-five patients (30 +/- 16 years) with GCS < or = 8 in this study. Jugular bulb oximetry, mean arterial pressure, intracranial pressure, end-tidal CO2 and pulse oximetry were monitored continuously. Catheter calibration against a laboratory oximeter was performed post insertion and thereafter eight-hourly. Cerebral venous desaturation was defined as a jugular bulb oxygen saturation < 55% of > 10 minutes duration. There was a poor correlation for the first in vivo calibration (r2 = 0.602, P < 0.001, n = 25). Thereafter a close correlation between jugular bulb catheter and oximetry values was demonstrated (r2 = 0.868, P < 0.001, n = 205). Forty-two episodes of jugular bulb oxygen desaturation of 88 minutes mean duration (range 10 to 555) were observed. 83% occurred within 48 hours following injury. Hypocapnia was associated in 45% of episodes; hypoperfusion in 22%; raised ICP in 9% and a combination of the above in 24%. Validation with a laboratory oximeter is essential prior to continuous jugular bulb oximetry. Sustained episodes of cerebral venous desaturation are frequent within the first 48 hours following acute head injury. Factors such as hypocapnia and cerebral hypoperfusion that primarily reduce cerebral blood flow are predominant.
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PMID:Detection of cerebral venous desaturation by continuous jugular bulb oximetry following acute neurotrauma. 866 39

Transcranial Doppler ultrasonography is an extremely useful adjunct in neurosurgical intensive care. Continuous improvements in TCD equipment as well as computer software have improved examination success and also vessel identification. Recent expanding applications of TCD have also allowed the study of disorders of control of the cerebral circulation. TCD can be used to detect vessel narrowing from a variety of causes, including vasospasm, and also can be used to detect cerebral emboli and to evaluate CO2 reactivity, autoregulation, and the response to certain medications, as well as to indicate progressive obstruction of the cerebral circulation as seen in conditions leading to brain death. In the future, TCD may offer the ability to estimate the ICP using noninvasive means by evaluating velocity in the middle cerebral artery and arterial blood pressure tracings. The noninvasive determination of cerebral autoregulation may be useful in evaluating strategies to improve cerebral autoregulation as well as aid in the optimal management of ICP control and preservation of optimal cerebral circulation.
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PMID:Transcranial Doppler ultrasonography. 782 74

The possibility of measuring cerebral blood flow by mobile bedside units with the intravenous 133-Xenon technique increased the interest to monitor haemodynamic changes after head injury and subarachnoid haemorrhage in intensive care. Time course of resting CBF after trauma is variable (reduced CBF, hyperemia) and there is no strong correlation to clinical outcome. Additional studies of CBF/CO2 reactivity show normal and impaired CO2 response in the acute stage after trauma (day 1-8). A permanently impaired CO2 reactivity correlates with severe brain damage and bad outcome (GOS 1,2). A normal or improving CO2 reactivity indicates a favourable outcome (GOS 3-5). There was no significant correlation between CBF and ICP, nor between CBF and CPP. A CPP of more than 70 mmHg did not guarantee a sufficient CBF in every case indicating the variability of the limits of autoregulation. As therapeutic hyperventilation may lead to ischemia, mannitol was preferred to reduce ICP and increased low CBF to normal values. This fact should be considered in the treatment of patients with low CBF and normal CO2 reactivity. Delayed ischemic neurological deficits ("vasospasm") are well-known as significant complications of the clinical course following SAH. Immediately postoperatively performed CBF measurements enable to detect ischemia and allow to start early antiischemic therapy. During "vasospasm" CBF showed a better correlation to the neurological status than blood flow velocity in the basal arteries measured by transcranial doppler sonography. Furthermore hyperemia after SAH could only be verified by CBF measurements.
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PMID:Xenon 133--CBF measurements in severe head injury and subarachnoid haemorrhage. 790 78

The effects of acidosis on ischemic brain damage are unclear and probably diverse. To establish an in vivo model of acidosis, the authors assess changes in extracellular brain pH (pHe), CBF and ICP induced by hypercarbic ventilation, and discuss the reliability and short comings of this experimental model. Acidosis was induced by increasing the inspired CO2 concentration in mechanically ventilated rats. pHe was measured with a pH-sensitive electrode implanted into the cortical mantle. The rats were divided into five groups according to the CO2 concentrations inspired: G-1, 0% control; G-2, -5-% CO2; G-3, -10-% CO2; G-4, -20-% CO2; G-5, -25-% CO2. Cortical blood flow was measured using a laser Doppler flowmeter, and ICP was also determined in each of the experimental groups. pHe decreased rapidly after the CO2 supply was turned on and remained almost constant at fixed concentrations of inspired CO2. pHe values diminished as the concentration of inspired CO2 decreased, as follows: G-2, -0.10 +/- 0.03; G-3, -0.31 +/- 0.08; G-4, -0.49 +/- 0.09; G-5, -0.64 +/- 0.10. The changes in pHe almost perfectly paralleled the changes in blood pH. The percentage increase in CBF was more than 200% in the G-2 groups and minimal increases in CBF, probably due to changes in blood pressure, were observed in from G-2 to G-5. Changes in CBF paralleled changes in systemic blood pressure, especially after the CO2 supply was turned off. ICP also rose after increasing the CO2 supply, and the pattern of changes was similar to that of CBF.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Changes in cerebral extracellular pH, cerebral blood flow and intracranial pressure induced by hypercarbic ventilation--assessment as a potential in vivo model of cerebral acidosis]. 794 19

During the last few years continuous measurements of CBF by means of a thermal diffusion blood flow probe have been proposed as a possible means for monitoring the patient's CBF in a clinical setting. Also, it has been suggested that continuous CBF data from head injured patients can be correlated with other continuously recorded clinical parameters, such as ICP and blood pressure, in order to clarify pathophysiological mechanisms such as "plateau-waves". We measured regional cortical blood flow continuously with a thermal diffusion flow probe in 13 comatose head injured patients after undergoing craniotomy for evacuation of a traumatic intracranial mass lesion in order to assess the reliability and usefulness of the method. In seven patients stable Xenon-CT CBF studies were performed with the flow probe in place, in order to compare the two methods. The continuous blood flow values did not correlate with regional or global stable Xenon-CT values. These results indicate that continuous monitoring of CBF with the thermal diffusion method as currently used cannot be used in the clinical management of the patient. Further research will have to be directed to the question as to whether changes in CBF are reliably measured with this method. If this is true, the thermal diffusion flow probe with its high temporal resolution may still be useful in investigating pathophysiological mechanisms such as interaction between CBF, ICP, mean arterial blood pressure (MABP), and end-expiratory CO2 (etCO2).
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PMID:Monitoring of regional cerebral blood flow (CBF) in acute head injury by thermal diffusion. 831 Aug 62

The feline infusion model of brain edema was used to evaluate the pathophysiological effects of 0.6 ml infusions of autologous serum protein (66%), human serum protein (66%), human glioma cyst fluid and a tissue culture medium (TCM) on the structure and function of the forebrain white matter. These infusions increased local white matter water content by between 10.8 and 12.5 ml/100 g brain and were associated with moderate increases in ICP and CSF outflow resistance and a significant decrease in lumped craniospinal compliance. Cortical somatosensory potentials, motor evoked potentials, EEG and local cerebral blood flow (rCBF) at normocapnia were generally unchanged by the various infusions. All infusates except the 66% autologous serum protein infusion impaired rCBF CO2 reactivity. Histologically all infusates caused marked extracellular edema. The autologous serum protein infusion caused no additional histological changes whereas the glioma cyst infusates caused profound endothelial and astrocytic swelling, focal endothelial necrosis, basement membrane disruption, perivascular microglial reaction and pavementation and perivascular migration of polymorphonuclear leukocytes. Similar but less marked changes were seen after infusion of human serum protein whilst the TCM produced only minimal changes. The intensity and extent of Evans Blue extravasation into the forebrain white matter was greatest with glioma cyst infusates and with all infusions reflected the extent to microvascular changes. These studies show that products derived from gliomas cause additional damage to the blood-brain-barrier than that caused by non-autologous serum proteins. These results add further support for the existence of glioma derived permeability factors (GDPF), but suggest neither serum proteins nor glioma derived compounds in the white matter interstitium significantly influence local electrophysiological function. Some limitations of the infusion edema model when using non-autologous infusions and difficulties quantitating brain dysfunction are emphasised.
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PMID:Neuropathological and neurophysiological effects of interstitial white matter autologous and non-autologous protein containing solutions: further evidence for a glioma derived permeability factor. 846 May 70

Standardized volume-pressure craniospinal system loadings based on physiological loadings were developed in order to study the CSF outflow route efficiency and to evaluate the intracranial volume-pressure relations. The study was carried out on 10 cats. Standardized abdominal compression was applied in order to produce a central venous pressure increased and subsequently ICP increase to the level of 20 and 30 mmHg for 2 minutes. The abdominal compression test seems to be useful in the CSF outflow route evaluation. The orthostatic changes were studied in control animals and in cats with an epidural balloon. The animal body was evaluated to an angle of 50 degrees and 80 degrees with the head directed upwards and downwards. This test was found suitable for the intracranial volume reserve estimation. Similar application, especially in experimental conditions can be found in the hypercapnia test. PaCO2 concentration was increased by means of respiration with a gas mixture containing 5% CO2. A steady increase of ICP of 9 +/- 1 mmHg was obtained. Vascular dilatation resulted in an intracranial volume loading. The ICP response in subjects with normal CO2 response can be related to the intracranial volume reserve. The studies performed show the usefulness of the standardized volume-pressure loadings. The loadings applied are more physiological than lumbar infusion tests used so far.
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PMID:Evaluation of craniospinal system condition using standardized volume-pressure loadings. 874 65

Dihydroergotamine (DHE) is used in our recently introduced therapy of post-traumatic brain oedema and is suggested to reduce ICP through reduction in both cerebral blood volume and brain water content. This study aims at increasing our knowledge of the mechanisms behind the ICP reducing effect of DHE by analysing cerebrovascular effects of a bolus dose of DHE in severely head injured patients (GCS < 8). Mean hemispheric cerebral blood flow (CBF) calculated from the clearance of i.v. 133Xenon, ICP, and cerebral arterio-venous difference in oxygen content (AVDO2), were measured before and after hyperventilation and after a bolus dose of DHE (4 micrograms/kg). The patients were divided into two groups, one with preserved and one with impaired cerebrovascular CO2-reactivity to hyperventilation, the latter being predictive of poor outcome. The haemodynamic effects of DHE were compared to those of hyperventilation. Regional CBF and brain volume SPECT measurements were performed in two patients. DHE increased cerebrovascular resistance (CVR) by about 20% and significantly reduced ICP in both groups of patients, resulting in unchanged AVDO2. Hyperventilation with preserved CO2-reactivity caused a similar decrease in ICP as by DHE but with a much larger increase in CVR (by 70%) and a substantial increase in AVDO2. Hyperventilation with impaired CO2-reactivity reduced ICP but otherwise had no significant cerebrovascular effects. The study supports the concept that the ICP reducing effect of DHE results more from constriction of the large veins than from arterial vasoconstriction, also implying a relatively smaller risk of ischaemia with DHE than with hyperventilation.
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PMID:Cerebral haemodynamic effects of dihydroergotamine in patients with severe traumatic brain lesions. 884 93

Simultaneous oxygen measurements in brain tissue (p(ti)O2) and hemoglobin saturation measurement in cerebrovenous blood in patients after severe head injury have shown different results regarding the comparability of the findings in respect to CPP and ICP. This is contrast to theoretical expectations. The aim of this study was to compare continuous ptiO2 measurement with oxygen partial pressure measurement in sagittal sinus (pO2cv) during simultaneously performance in an animal intracranial pressure model. For continuous measurement we used a newly available multisensor probe. We placed a Paratrend 7 probe (BSL, High Wycombe, UK) in the left frontoparietal white matter and measured ptiO2, pCO2 (ptiCO2) pH (pHti) and temperature (t(ti)) while simultaneously measuring these parameters (pcvO2, pcvCO2, pHcv, tcv) in the sagittal sinus in 9 pigs under general anaesthesia. A fogarty balloon catheter was placed supracerebellar infratentorial and inflated stepwise in order to increase ICP. The baseline levels of pO2ti, pCO2ti und pHti in the non-injured brain tissue showed a more extended heterogeneity compared to the findings in cerebrovenous blood. Both, pO2ti and pO2cv were significant correlated to the CPP decrease. In both measurement compartments pCO2 was inverse correlated to the course of CPP and seems the course of pH mainly to determine. p(ti)O2 as well as p(cv)O2 showed a close correlation to the CPP course and have proven to be qualified to indicate metabolic information about the relation of cerebral blood flow and metabolic cerebral demands. The measurement of CO2 tension in both measurement compartments shows a distinct heterogeneity of the absolute values and the results are only weak correlated to CPP. Metabolic influence on this parameter could not be revealed in the used experimental approach.
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PMID:Comparison between continuous brain tissue measurement and cerebrovenous measurement of pO2, pCO2 and pH in a porcine intracranial pressure model. 940 55

Local brain tissue oxygenation (p(ti)O2) and global cerebrovenous hemoglobin saturation (SjO2) are increasingly used to continuously monitor patients after severe head injury (SHI). In patients, simultaneous local and global oxygen measurements of these types have shown different results regarding the comparability of the findings during changes in CPP and ICP. This is in contrast to theoretical expectations. The aim of this study was to compare p(ti)O2 measurement with cerebrovenous oxygen partial pressure measurement (p(cv)O2) in an animal intracranial pressure model. To this end, a multisensor probe was placed in the left frontoparietal white matter to measure p(ti)O2, pCO2 (p(ti)CO2), pH (pH[ti]), and temperature (t[ti]) while simultaneously measuring these same parameters (p(cv)O2, p(cv)CO2 pH(cv), t[cv]) in the sagittal sinus of 9 pigs under general anesthesia. By stepwise inflating a balloon catheter, placed in supracerebellar infratentorial compartment, ICP was increased and CPP was decreased. The baseline levels of p(ti)O2, p(ti)CO2, and pH(ti) in the noninjured brain tissue showed more heterogeneity compared to the findings in cerebrovenous blood. Both, p(ti)O2 and p(cv)O2 were significantly correlated to the induced CPP decrease. PCO2 was inversely correlated to the course of CPP in both measurement compartments. Temperature measurement showed a positive correlation with CPP in both compartments. These findings demonstrate that brain tissue oximetry and cerebrovenous PO2 measurement are sensitive to CPP changes. The newly available continuous parameters in multisensor probes could be helpful in interpreting findings of cerebral oxygen measurement in man by analyzing the interrelationship of these parameters.
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PMID:Comparison between continuous brain tissue pO2, pCO2, pH, and temperature and simultaneous cerebrovenous measurement using a multisensor probe in a porcine intracranial pressure model. 955 72


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