Biomedical subjects

Marek Czosnyka

Publications and source records attributed to Marek Czosnyka.

43 records · Page 3Linked to original sources

PubMed2002

Continuous monitoring of cerebrovascular pressure reactivity allows determination of optimal cerebral perfusion pressure in patients with traumatic brain injury.

OBJECTIVES: To define optimal cerebral perfusion pressure (CPPOPT) in individual head-injured patients using continuous monitoring of cerebrovascular pressure reactivity. To test the hypothesis that patients with poor outcome were managed at a cerebral perfusion pressure (CPP) differing more from their CPPOPT than were patients with good outcome. DESIGN: Retrospective analysis of prospectively collected data. SETTING: Neurosciences critical care unit of a university hospital. PATIENTS: A total of 114 head-injured patients admitted between January 1997 and August 2000 with continuous monitoring of mean arterial blood pressure (MAP) and intracranial pressure (ICP). MEASUREMENTS AND MAIN RESULTS: MAP, ICP, and CPP were continuously recorded and a pressure reactivity index (PRx) was calculated online. PRx is the moving correlation coefficient recorded over 4-min periods between averaged values (6-sec periods) of MAP and ICP representing cerebrovascular pressure reactivity. When cerebrovascular reactivity is intact, PRx has negative or zero values, otherwise PRx is positive. Outcome was assessed at 6 months using the Glasgow Outcome Scale. A total of 13,633 hrs of data were recorded. CPPOPT was defined as the CPP where PRx reaches its minimum value when plotted against CPP. Identification of CPPOPT was possible in 68 patients (60%). In 22 patients (27%), CPPOPT was not found because it presumably lay outside the studied range of CPP. Patients' outcome correlated with the difference between CPP and CPPOPT for patients who were managed on average below CPPOPT (r =.53, p <.001) and for patients whose mean CPP was above CPPOPT (r = -.40, p <.05). CONCLUSIONS: CPPOPT could be identified in a majority of patients. Patients with a mean CPP close to CPPOPT were more likely to have a favorable outcome than those whose mean CPP was more different from CPPOPT. We propose use of the criterion of minimal achievable PRx to guide future trials of CPP oriented treatment in head injured patients.

Adolescent↗

PubMed2002

Elastance correlates with outcome after endoscopic third ventriculostomy in adults with hydrocephalus caused by primary aqueductal stenosis.

OBJECTIVE: To study prospectively the correlation between clinical outcome after endoscopic third ventriculostomy (ETV) and resistance to the outflow of cerebrospinal fluid (R(out)) and elastance in adults with hydrocephalus caused by primary aqueductal stenosis (AS). METHODS: R(out) and elastance were measured in the subarachnoid space and intraventricularly before ETV in 15 consecutive patients. Three months after the ETV, the clinical effect was evaluated by standardized indices, and R(out) and elastance were measured. If symptoms persisted and the ETV was patent, shunt surgery was offered. The effect of the shunt operation and R(out) were measured after 3 months. RESULTS: Four patients experienced excellent improvement, six improved slightly, and five had unchanged or deteriorated symptoms after ETV. R(out) before ETV did not correlate with outcome. R(out) decreased after ETV with correlation to the clinical effect; in the six patients who had shunt surgery, R(out) decreased further. High preoperative elastance correlated strongly with a good outcome and reduction of ventricle size. Elastance did not change after ETV. CONCLUSION: R(out) intraventricularly and in the subarachnoid space could not predict the outcome of the ETV, but the reduction in R(out) correlated positively with clinical improvement. Preoperative elastance correlated positively with clinical improvement, and elastance was unchanged after ETV. Clinical improvement correlated positively with reduction in ventricle size.

Adolescent↗

PubMed2002

Cerebral autoregulation among patients with symptoms of hydrocephalus.

OBJECTIVE: To study the relationship between the resistance to cerebrospinal fluid (CSF) outflow and cerebral autoregulation. METHODS: We examined 35 patients who presented with ventricular dilation and clinical symptoms of communicating hydrocephalus. For all of these patients, CSF compensatory reserve was investigated by using a computerized infusion test, with simultaneous recording of blood flow velocity wave forms (by using transcranial Doppler ultrasonography) and arterial blood pressure (with a Finapress finger cuff). The resistance to CSF outflow was calculated as the absolute increase in intracranial pressure (interpolated over vasogenic waves) divided by the infusion rate (1.5 ml/min in most cases). The index of autoregulation was assessed as a correlation coefficient (moving time window of 5 min) between slow waves (with periods of 20 s to 2 min) in mean blood flow velocity and cerebral perfusion pressure. RESULTS: The mean intracranial pressure increased during the test, from 6 mm Hg (standard deviation, 6 mm Hg) to 20 mm Hg (standard deviation, 10 mm Hg) (P < 0.0001). The index of autoregulation was significantly correlated with the resistance to CSF outflow (r = -0.41, P < 0.03), indicating better autoregulation with greater resistance to CSF outflow. CONCLUSION: Patients presenting with ventricular dilation may exhibit either decreased (atrophy) or increased (normal-pressure hydrocephalus) resistance to CSF outflow. Increased resistance is correlated with preserved autoregulation. Patients with low resistance, suggesting brain atrophy, more often have disturbed autoregulation in the middle cerebral artery territory, as assessed by transcranial Doppler ultrasonography.

Adult↗

PubMed2002

A case study of hemispatial neglect using finite element analysis and positron emission tomography.

BACKGROUND: The authors present a patient who developed transient hemispatial neglect following surgical drainage of a large right frontotemporal arachnoid cyst. As symptoms evolved in parallel with brain shift over the subsequent months, the authors hypothesized that the disorder was associated with the appearance of mechanical stresses in the cerebral mantle. METHODS: To map tissue stress at the various stages of deformation, a finite element computer simulation was conducted on the basis of computed tomography scans of the patient. RESULTS: The authors' results demonstrate substantial shear and compressive stress concentrations in the parietal lobe, a region commonly associated with neglect, and where positron emission tomography confirmed hypoperfusion in this patient. Treatment with combined ventricular-peritoneal and cystoperitoneal shunts was accompanied by clinical recovery and improvement of right parietal lobe cerebral blood flow. CONCLUSIONS: The authors conclude that brain deformation was a contributing factor in the reversible neglect syndrome by compromising the normal flow of blood and/or the deactivation of subcortical circuits of the parietal lobe.

Aged↗

PubMed2002

Cerebral oxygen and microdialysis monitoring during aneurysm surgery: effects of blood pressure, cerebrospinal fluid drainage, and temporary clipping on infarction.

OBJECT: The aim of this study was to investigate potential episodes of cerebral ischemia during surgery for large and complicated aneurysms, by examining the effects of arterial temporary clipping and the impact of confounding variables such as blood pressure and cerebrospinal fluid (CSF) drainage. METHODS: Brain tissue PO2, PCO2, and pH, as well as temperature and extracellular glucose, lactate, pyruvate, and glutamate were monitored in 46 patients by using multiparameter sensors and microdialysis. Baseline data showed that brain tissue PO2 decreased significantly, below a mean arterial pressure (MAP) threshold of 70 mm Hg. Further evidence of its relationship with cerebral perfusion pressure was shown by an increase in mean brain tissue PO2 after drainage of CSF from the basal cisterns (Wilcoxon test, p < 0.01). Temporary clipping was required in 31 patients, with a mean total duration of 14 minutes (range 3-52 minutes), causing brain tissue PO2 to decrease and brain tissue PCO2 to increase (Wilcoxon test, p < 0.01). In patients in whom no subsequent infarction developed in the monitored region, brain tissue PO2 fell to 11 mm Hg (95% confidence interval 8-14 mm Hg). A brain tissue PO2 level below 8 mm Hg for 30 minutes was associated with infarction in any region (p < 0.05 according to the Fisher exact test); other parameters were not predictive of infarction. Intermittent occlusions of less than 30 minutes in total had little effect on extracellular chemistry. Large glutamate increases were only seen in two patients, in both of whom brain tissue PO2 during occlusion was continuously lower than 8 mm Hg for longer than 38 minutes. CONCLUSIONS: The brain tissue PO2 decreases with hypotension, and, when it is below 8 mm Hg for longer than 30 minutes during temporary clipping, it is associated with increasing extracellular glutamate levels and cerebral infarction.

Adult↗

PubMedDate not supplied

Hydrocephalus, ventriculomegaly and the vegetative state: a review.

The revised guidelines from the Royal College of Physicians make it clear that structural problems such as hydrocephalus should be excluded before the diagnosis of vegetative state (VS) can be made. Ventriculomegaly is common after severe head injury but the distinction between atrophy and potentially treatable hydrocephalus cannot be made on the basis of conventional computerised tomographic (CT) or magnetic resonance (MR) scanning alone--physiological measurements of intracranial pressure (ICP) and cerebrospinal fluid (CSF) outflow resistance may be helpful. These techniques are reviewed together with the limited literature available that documents the effect of CSF diversion on outcome in "vegetative" patients.

Cerebral Ventricles↗

PubMedDate not supplied

[Modeling of cerebrospinal fluid circulation with consideration of a pressure-volume curve in infusion tests of patients with suspected hydrocephalus. Preliminary report].

AIM OF THE STUDY: To verify the model of CSF circulation for both the increasing and decreasing CSF pressure during and after the infusion test. MATERIAL: Computerized infusion tests of 27 patients diagnosed for communicating hydrocephalus in the Department of Neurosurgery, Medical University of Warsaw were analyzed. METHOD: Pressure-volume (P-V) curves were plotted separately for ascending and descending phases of the test for comparison purposes. RESULTS: The phenomenon of significant change of the P-V curve slope after the infusion was identified in 70% of tests. It was found that the elastance coefficient was significantly greater during the infusion than after the infusion. The pulsatile changes in cerebral blood volume were higher after the infusion in comparison to values during the infusion. The baseline pressure was higher than that before the infusion. There was a significant increase in mean arterial blood pressure after the infusion and it was not associated with any change in the heart rate. CONCLUSIONS: We hypothesized that vasogenic component of intracranial pressure is responsible for the change of P-V curve slope. We also presume that the higher value of the pressure after the infusion can be due to by the excessive accumulation of cerebrospinal fluid in the intracranial space, including extra cellular parenchymal space. Both hypotheses require further studies to be evaluated.

Adolescent↗