Biomedical subjects

Andreas Raabe

Publications and source records attributed to Andreas Raabe.

49 records · Page 3Linked to original sources

PubMed2003

Risk of postoperative hemorrhage after intracranial surgery after early nadroparin administration: results of a prospective study.

OBJECTIVE: Early postoperative pharmacological prophylaxis of deep vein thrombosis after intracranial surgery is still a matter of debate because of concerns regarding the formation of postoperative hematoma. The objective of this study was to prospectively analyze the rate of postoperative hemorrhage during a 3-year period of early postoperative administration of the low molecular weight heparin nadroparin (Fraxiparin) plus compression stockings in a large cohort of patients undergoing intracranial surgery. METHODS: A total of 2823 intracranial neurosurgical procedures, performed between June 1999 and 2002, were studied. Of these operations, 1319 (46.7%) were major intracranial surgical procedures (Group 1). Group 2 comprised 1504 operations (53.3%) considered to be minor surgical procedures (e.g., shunt procedures, biopsies). All patients except those with transnasal transsphenoidal removal of pituitary tumors underwent early postoperative imaging (computed tomography or magnetic resonance imaging) to determine postoperative hemorrhage. All significant postoperative hematomas (defined as those requiring surgical evacuation because of relevant space occupation and/or neurological deterioration) were treated surgically. Prophylaxis of venous thromboembolic events included early (<24 h) postoperative administration of 0.3 ml nadroparin subcutaneously plus intra- and postoperative compression stockings until discharge. RESULTS: Forty-three major postoperative hemorrhages (1.5%) were observed after 2823 intracranial procedures (95% confidence interval, 1.1-2.05). Forty-two (3.2%) of 1319 postoperative hematomas occurred in patients undergoing major intracranial procedures (Group 1). There was only 1 (0.07%) significant hemorrhage after 1504 minor intracranial procedures (Group 2). A subgroup analysis of patients who needed preoperative anticoagulation because of medical comorbidity did not reveal an increased frequency of postoperative hematoma when anticoagulation was stopped 24 hours before surgery P = 0.1, chi(2) test; 95% confidence interval, 0.89-3.0). CONCLUSION: This report describes the largest prospective study conducted to date to determine the hemorrhage rate after early postoperative anticoagulation. The results support the concept of postoperative pharmacological thromboembolic prophylaxis in patients undergoing intracranial surgery.

Adult↗

PubMed2003

Measurements of serum S-100B protein: effects of storage time and temperature on pre-analytical stability.

Measurement of S-100B protein in serum or cerebrospinal fluid is increasingly used as a molecular marker of brain damage. However, there is no information about the pre-analytical in vitro stability of S-100B. We have investigated whether storing blood samples at different time periods and conditions affected the measured levels of S-100B protein. Blood samples were taken from 29 neurosurgical patients with normal serum S-100B values and from seven patients with increased serum S-100B values. Blood samples were immediately divided into nine aliquots for measuring S-100B immediately and after 4, 8, 12, and 24 hours, stored at room temperature or at 4 degrees C. Measurement of S-100B was performed using the LIAISON assay (Byk-Sangtec Diagnostica, Dietzenbach, Germany). Moreover, in 10 additional patients the effect of freezing the serum and thawing the sample after 24 hours was investigated. There were no differences between the results of S-100B measurements after storing the sample at different temperatures and time periods. There was no trend towards higher or lower values in all three groups. Therefore, blood samples may be collected as part of the daily clinical routine without time constraint and even stored overnight without affecting S-100B serum levels when measured with the LIAISON Sangtec 100 assay.

Blood Preservation↗

PubMed2003

Automated fiducial marker detection for patient registration in image-guided neurosurgery.

OBJECTIVE: The registration of applied fiducial markers within the preoperative data is often left to the surgeon, who has to identify and tag the center of each marker. This is both time-consuming and a potential source of error. For this reason, the development of an automated procedure was desirable. In this study, we have investigated the accuracy of a software algorithm for detecting fiducial markers within the navigation data set. The influence of adjustable values for accuracy and threshold on the sensitivity and specificity of the detection process, as well as the time gain, was investigated. PATIENTS AND METHODS: One hundred MP-RAGE MRI data sets of patients with different pathologies who were scheduled for image-guided surgery were used in this study. A total of 591 applied fiducial markers were to be detected using the algorithm of the software VVPlanning 1.3 (BrainLAB, Heimstetten, Germany) on a Pentium II standard PC. The size value of a marker in the y-direction is called "accuracy" and depends on the slice thickness. "Threshold" describes the gray level above which the algorithm starts searching for pixel clusters. The threshold value was changed stepwise on the basis of a constant "accuracy" value. The "accuracy" value was changed on the basis of that threshold value at which all markers were detected correctly. RESULTS: The time needed for automatic detection varied between 12 s and 25 s. An optimum value for adjustable marker size was found to be 1.1 mm, with 8 undetected markers (1.35%) and 7 additionally detected structures (1.18%) out of 591. The mean gray level (Threshold) for all data sets above which marker detection was correct was 248.9. The automatic detection of markers was good for higher gray levels, with 11 missed markers (1.86%). Starting the algorithm at lower gray levels led to a decreased incidence of missed markers (0.17%), but increased the incidence of additionally detected structures to 27.92%. CONCLUSION: The automatic marker-detection algorithm is a robust, fast and objective instrument for reliable fiducial marker registration when used with optimum settings for both threshold and accuracy.

Adolescent↗

PubMed2003

Symmetry of cerebral hemodynamic indices derived from bilateral transcranial Doppler.

OBJECTIVE: The authors evaluated with bilateral transcranial Doppler (TCD) ultrasonography the norm of interhemispheric difference for several cerebrovascular hemodynamic parameters. METHODS: Forty-four volunteers (33 male, 11 female; average age = 21 years; range, 20-23 years) were studied. The authors recorded bilateral systolic, diastolic, and mean flow velocity (FV) and noninvasive systolic, diastolic, and mean arterial blood pressure. Calculated indices included Gosling's pulsatility index (GPI), an index of autoregulation (Mx), critical closing pressure (CCP), and a noninvasive estimator of cerebral perfusion pressure (nCPP). All indices were averaged per side and patient. For each parameter, the left-right correlation coefficient (r2) and the 95% confidence limit of the left-right differences were calculated. RESULTS: All TCD-derived indices displayed significant correlations between the left and right sides: r2 = 0.49 for mean FV (FVm), r2 = 0.66 for GPI, r2 = 0.79 for Mx, r2 = 0.93 for CCP, and r2 = 0.94 for nCPP. The 95% confidence intervals for the left-right differences were 20 cm/s for FVm, 0.16 for GPI, 0.18 for Mx, 13 mm Hg for CCP, and 4.6 mm Hg for nCPP. CONCLUSIONS: This study gives the reference values for the assessment of left-right symmetry of cerebral hemodynamics using various TCD-derived indices. These reference values should be useful for clinical studies assessing the left-right asymmetry of cerebral hemodynamics on a daily basis.

Adult↗

PubMed2003

Actual aspects of image-guided surgery.

Use of surgical navigation systems is becoming an increasingly important part of both planning and performing intracranial and spinal surgery. Numerous clinical reports have described neuronavigation as a useful adjunct to surgery that allows neurosurgery to be less invasive and more effective. Although the method of image-guided surgery was introduced more than a decade ago, new technologies have changed and refined the procedure substantially. This chapter summarizes the recent developments of advanced image-guided surgery. For most operations, microscope navigation has replaced pointer navigation. Using the microscope as the localizing device, the workflow is not interrupted and microsurgical procedure can be continued as usual. New chip technology allows integration of magnetic resonance images, angiography findings, endoscopic view, or other pictures in the eyepiece of the microscope. A new method of patient registration is laser scanning and surface matching. When using high-quality images, this new method can be used without additionally acquired images, may reduce costs, simplify the pre-registration procedure, and increase application accuracy compared to skin-fiducial registration. Moreover, integration of other imaging modalities is becoming an increasingly used feature and provides useful information during surgery.

Brain Mapping↗

PubMed2003

Serum S-100B protein as a molecular marker in severe traumatic brain injury.

PURPOSE: There is growing evidence that S-100B protein may be used as a novel biochemical marker of brain cell damage, measured by a simple blood test. In this paper, we summarize the current knowledge about S-100B serum measurements in severe head injury and address actual controversies. METHODS: The material of the present analysis consists of a MEDLINE literature search for S-100 and severe head injury from 1966 to 2003. Studies of S-100B in severe head injury were reviewed for their information about the potential clinical value of this marker. RESULTS: A total of 18 clinical studies were identified and reviewed. Peak values of serum S-100B were demonstrated to have the highest correlation to any endpoint parameter. Admission values also have a significant correlation to injury severity and outcome but show a highly time dependent temporal course. There is extracranial release of S-100B in multitrauma patients in the first 48 hours, but the impact is limited as many studies have found a clear relationship between S-100B and injury severity, imaging findings and outcome. CONCLUSION: S-100B belongs to a new generation of molecular serum markers of brain damage. These markers will have potential as a surrogate outcome marker or monitoring parameters for both clinical and experimental settings.

Biomarkers↗

PubMed2002

[D-Val22]big ET-1[16-38] inhibits endothelin-converting enzyme activity: a promising concept in the prevention of cerebral vasospasm.

The aim of this study was to investigate whether the blocking of endothelin-converting enzyme (ECE) activity offers a new approach to inhibiting the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) by preventing transformation of big endothelin-1 (big ET-1) to vasoactive endothelin-1 (ET-1). The effect of potential ECE inhibitors was determined in vitro by measurement of isometric contractions, induced by big ET-1, in isolated rat basilar arteries. Intact and de-endothelialized endothelium (E+ and E-, respectively) segments were examined after preincubation with the putative ECE inhibitors: phosphoramidon (10(-4) M), and [22D-Val]big ET-1 [16-38] (10(-5) M and 10(-6) M). Additionally, the effect of [D-Val22]big ET-1 [16-38] was investigated in rabbits after intracisternal application in order to inhibit the contraction of the basilar artery induced by (2x10(-6) M) big ET-1. Application of 10(-4)-M phosphoramidon resulted in a statistically significant decrease in big ET-1-induced contraction in E+ and E- segments; 10(-5)-M and 10(-6)-M [22D-Val]big ET-1 [16-38] in E- segments produced no statistically significant effect. The application of 10(-6)-M [22D-Val]big ET-1 [16-38] in E+ segments caused increased contractions, as shown by the shift to the left of the concentration-effect curve (CEC). In the rabbit group pretreated with [D-Val22]big ET-1 [16-38] (2x10(-5) M) (n=8), the angiographically measured diameter of the basilar artery increased from 0.63+/-0.12 mm to 0.66+/-0.12 mm. In the control group (n=8), this diameter decreased from 0.71+/-0.13 mm to 0.57+/-0.15 mm. This corresponded to an increase in vessel diameter of 5.24+/-9.89% in the treatment group and a decrease of 19.54+/-15.81% in the control group (P=0.002). The present study indicates the existence of functional ECE activity in rat basilar artery, which differs in the endothelium and the smooth muscle layer. These results demonstrate that [D-Val22]big ET-1 [16-38] has a potent ECE-inhibitory effect, preventing cerebral vasospasm in rabbit basilar artery by inhibiting the transformation of big ET-1 to vasoactive ET-1 after intracisternal application in vivo, whereas no inhibitory effect was detectable in rat basilar artery in vitro. Therefore, further studies of the biochemical nature of cerebrovascular ECE activity are required.

Animals↗

PubMed2002

Laser surface scanning for patient registration in intracranial image-guided surgery.

OBJECTIVE: To report our clinical experience with a new laser scanning-based technique of surface registration. We performed a prospective study to measure the calculated registration error and the application accuracy of laser surface registration for intracranial image-guided surgery in the clinical setting. METHODS: Thirty-four consecutive patients with different intracranial diseases were scheduled for intracranial image-guided surgery by use of a passive infrared surgical navigation system. Surface registration was performed by use of a Class I laser device that emits a visible laser beam. The Polaris camera system (Northern Digital, Waterloo, ON, Canada) detects the skin reflections of the laser, which the software uses to generate a virtual three-dimensional matrix of the anatomy of each patient. An advanced surface-matching algorithm then matches this virtual three-dimensional matrix to the three-dimensional magnetic resonance therapy data set. Registration error as calculated by the computer was noted. Application accuracy was assessed by use of the localization error for three distant anatomic landmarks. RESULTS: Laser surface registration was successful in all patients. For the surgical field, application accuracy was 2.4 +/- 1.7 mm (range, 1-9 mm). Application accuracy was higher for the surgical field of frontally located lesions (mean, 1.8 +/- 0.8 mm; n = 13) as compared with temporal, parietal, occipital, and infratentorial lesions (mean, 2.8 +/- 2.1 mm; n = 21). CONCLUSION: Laser scanning for surface registration is an accurate, robust, and easy-to-use method of patient registration for image-guided surgery.

Adolescent↗

PubMed2002

Effect of intraventricular sodium nitroprusside on cerebral hemodynamics and oxygenation in poor-grade aneurysm patients with severe, medically refractory vasospasm.

OBJECTIVE: Sodium nitroprusside (SNP) was recently suggested as a treatment for cerebral ischemia in patients with severe, medically refractory vasospasm after subarachnoid hemorrhage. In this study, we sought to objectify the effect on cerebral hemodynamics and oxygenation (PbrO2) when using intraventricular SNP as a last resort therapy in poor-grade patients with subarachnoid hemorrhage; severe, medically refractory vasospasm; and compromised cerebral blood flow. METHODS: Thirteen of 185 consecutive patients with subarachnoid hemorrhage developed severe, medically refractory vasospasm and were treated with intraventricular SNP. All of these patients' neurological conditions were classified as Hunt and Hess Grade IV. SNP doses ranged from 10 to 40 mg with single-dose treatment and from 2 to 8 mg/h with continuous infusion. Angiography or PbrO2 measurement was used to assess the treatment effects. RESULTS: In 6 of the 13 patients, SNP improved cerebral hemodynamics, as demonstrated by increased PbrO2 or decreased cerebral circulation time. Only 1 patient showed increased diameter of the spastic vessel, however. Maximum increase in PbrO2 ranged from 5 to 52 mmHg. Adverse effects were hypertension in five patients, vomiting in three patients, and cardiac arrhythmia in one patient. Cerebral infarctions caused by vasospasm occurred in 6 (46%) of the 13 patients. No differences between SNP responders and SNP nonresponders were noted. CONCLUSION: In patients with severe, medically refractory vasospasm, intraventricular SNP may improve PbrO2 and cerebral blood flow, but the effect is highly variable. On the basis of the improvements we observed in 6 of 13 patients, intraventricular SNP administration is justified as a last resort therapy in patients with cerebral ischemia and impending infarction. Our findings suggest that SNP may be more effective when initiated early and administered continuously.

Adult↗

PubMed2002

Increased risk for postoperative hemorrhage after intracranial surgery in patients with decreased factor XIII activity: implications of a prospective study.

BACKGROUND AND PURPOSE: The functional integrity of the hemostatic system is a prerequisite for the safe performance of neurosurgical procedures. To monitor the individual coagulation capacity of each patient, standard tests are effective to detect deficiencies involving the generation of fibrin. However, fibrin clot strength depends primarily on coagulation factor XIII, which cross-links fibrin monomers and enhances clot resistance against fibrinolysis. Therefore, factor XIII is functionally involved in both the hemostatic and fibrinolytic systems. The objective of this prospective study was to determine the incidence and clinical relevance of perioperative decreased factor XIII with respect to standard coagulation parameters and the occurrence of postoperative hematoma. METHODS: In 876 patients, 910 neurosurgical procedures were performed. Prothrombin time (PT), partial thromboplastin time (PTT), platelet count, fibrinogen, and factor XIII were tested in each patient preoperatively and postoperatively. RESULTS: Postoperative intracranial hematoma (defined as requiring surgical evacuation) occurred after 39 (4.3%) of 910 surgical procedures. Patients with postoperative hematoma had significantly lower factor XIII and fibrinogen levels preoperatively and postoperatively than patients without hematoma. In patients with postoperative hematoma, PT and platelets differed significantly only postoperatively, whereas PTT was different neither preoperatively nor postoperatively. Of the 39 patients with a postoperative hematoma, 13 (33.3%) had a postoperative factor XIII <60% compared with 61 (7%) of 867 patients without hematoma (P<0.01, Fisher's exact test). The relative risk of developing a postoperative hematoma is therefore increased 6.4-fold in patients with postoperative factor XIII <60%. The risk is increased 12-fold in patients who additionally have postoperative decreased fibrinogen levels (<1.5 g/L) and 9-fold in patients with platelet count <150x10(9)/L and factor XIII <60%. CONCLUSIONS: This is the first prospective study that demonstrates the association of decreased perioperative factor XIII with an increased risk of postoperative hematoma in neurosurgical patients. The risk is further increased in those patients with low factor XIII and additional abnormalities of fibrinogen, PT, platelets, and PTT. Factor XIII testing and specific replacement, as accepted for other clotting factors, may reduce the risk of postoperative hematoma.

Comorbidity↗

PubMed2002

Application of recombinant activated factor VII during surgery for a giant skull base hemangiopericytoma to achieve safe hemostasis. Case report.

The authors report on a 64-year-old woman with a huge recurrent skull base hemangiopericytoma, in whom they encountered severe difficulty in attaining intraoperative hemostasis. Standard surgical hemostatic methods and the administration of fresh-frozen plasma and prothrombin complex concentrates failed to stop diffuse bleeding from an inoperable tumor remnant. At a critical point during the operation, the intravenous administration of recombinant activated factor VII, combined with mechanical compression, finally led to satisfactory hemostasis. The rationale for using recombinant activated factor VII in situations of uncontrolled bleeding during neurosurgical procedures is discussed, along with the literature in which the use of recombinant activated factor VII as a maneuver of last resort is reported for hemostasis in other surgical fields.

Cerebral Angiography↗

PubMed2002

Robot-assisted navigated neuroendoscopy.

OBJECTIVE: Major steps in the evolution of advanced neurosurgical techniques include microneurosurgery, neuroendoscopy and its minimally invasive variations, neuronavigation, and advanced intraoperative imaging. With traditional neuroendoscopic techniques (e.g., freehand endoscopy or the use of mechanical arms), definitive controlled movement of the endoscope within the brain depends on the experience and skill of the individual neurosurgeon. METHODS: With the Evolution 1 precision robot (Universal Robot Systems, Schwerin, Germany), a new neurosurgical tool has become available for the precise steering of instruments within the cranium. After preclinical anatomic and precision studies, the system was used for neuronavigated endoscopic procedures for three patients. RESULTS: All robot-assisted, navigated, endoscopic procedures were successfully completed. The time for the registration procedure and setup of the robot decreased from 60 minutes for the first patient to 30 minutes for the third patient. The time for the surgical part of the endoscopic procedure ranged from 17 to 65 minutes. No complications occurred during any procedure. CONCLUSION: The use of robotic technology for neuroendoscopic procedures is a major advance for controlled movement of the endoscope within the cranium. The start-up procedure and calibration of the robot are still time-consuming, but the actual operation time is comparable to that of freehand neuroendoscopic procedures. Steering of the endoscope is facilitated, and the precision of the endoscopic movements is noteworthy.

Adolescent↗

PubMedDate not supplied

Cerebrovascular characterization of the novel nonpeptide endothelin-A receptor antagonist LU 208075.

Enhanced cerebrovascular resistance under pathologic conditions, like cerebral vasospasm after subarachnoid hemorrhage, seems to be caused by the vasocontractile effect of endothelin-1 (ET-1). Therefore, the effect of the novel and ET(A) receptor selective antagonist LU 208075 was characterized by the contraction and relaxation induced by ET-1 and bigET-1 on rat basilar artery. Basilar artery ring segments with (E+) and without (E-) functionally intact endothelium were prepared to measure the isometric force. Concentration-effect curves were constructed by cumulative application of ET-1 or bigET-1 in the presence of LU 208075 (10(-7)M, 10(-6)M, and 10(-5)M). The effect of LU 208075 was determined by the pA(2) value. The contraction by ET-1 and bigET-1 was inhibited by LU 208075 in a dose-dependent manner. The pA(2) values for ET-1 and for bigET-1 were 6.51 +/- 0.39 (E+) and 6.67 +/- 0.43 (E-), and 7.03 +/- 0.32 (E+) and 7.24 +/- 0.31 (E-) respectively. The E(max) values for bigET-1 but not for ET-1 were reduced significantly in the presence of LU 208075. A significant relaxation by ET-1 or bigET-1 was observed only in the presence of LU 208075. This relaxation was inhibited by LU 208075 in higher concentrations, with pA(2) values of 5.68 +/- 0.05 (ET-1) and 5.50 +/- 0.39 (bigET-1). The current data correlate with a competitive inhibition of ET(A) receptor-mediated contraction and relaxation, caused by ET(B) receptor activation on cerebral vessels by LU 208075. The selectivity for the ET(A) receptor was approximately sevenfold. Furthermore, the results may suggest an inhibition of the functional ET-converting enzyme activity by LU 208075.

Animals↗