Christian Kolbitsch

Evaluation of Striatal Dopamine Transporter Function in Rats by in Vivo β-[123I]CIT Pinhole SPECT

Striatal dopamine transporter (DAT) function was evaluated in rats by in vivo SPECT-MRI coregistration using the radioligand 2-beta-carbomethoxy-3-beta-(4-[123I]iodophenyl)tropane (beta-[123I]CIT). The reconstructed transaxial resolution of 3.5 mm full width at half-maximum and the system sensitivity of 0.081 c/s/kBq using a 2.0-mm pinhole collimator aperture provided adequate spatial detail and sufficient sensitivity for imaging striatal beta-[123I]CIT uptake. SPECT images, coregistered onto a MRI template, showed high accuracy in the coronal and transverse planes (maximum mismatch of 1.3 mm). Following estimation of the in vivo binding equilibrium of beta-[123I]CIT in the healthy rat striatum, we evaluated the 6-hydroxydopamine-induced loss of striatal DAT function using beta-[123I]CIT SPECT and MRI coregistration and correlated these findings with dopaminergic cell counts in the substantia nigra pars compacta using TH immunohistochemistry. A subtotal unilateral DAT deficit was detected by beta-[123I]CIT SPECT in all animals which correlated significantly with the cell counting of the remaining dopaminergic neurons. beta-[123I]CIT pinhole SPECT provides a powerful and widely available tool for in vivo investigations of rat striatal DAT function. In contrast to classical autoradiography, the present method will be helpful in imaging dynamic changes of neurotransmission in the CNS by virtue of serial study designs. Depending on SPECT ligand availability, a wide range of other CNS receptors may be imaged as well using the presented in vivo technique.

Publication output in telemedicine during the period January 1964 to July 2003

The MEDLINE database was used to survey the period January 1964 to July 2003 for the number of publications relating to telemedicine (n = 5911), as well as their distribution by country (n = 42). Publications per million inhabitants were then correlated with each countrys population density, gross national product, human development index (HDI) and number of PCs per 1000 inhabitants. Telemedicine publications made up 0.05% of all medical publications cited in MEDLINE. American and European countries along with others classified as industrialized produced 97% of all telemedicine publications. In terms of publications per million inhabitants, Norway and Finland took the lead. There were significant correlations between telemedicine publications per capita and HDI (r = -0.60), number of PCs per 1000 inhabitants (r = 0.73) and gross national product per capita (r = 0.69), but not population density (r = -0.12).

The influence of hyperoxia on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV) and cerebral blood flow velocity in the middle cerebral artery (CBFVMCA) in human volunteers

Conflicting results reported on the effects of hyperoxia on cerebral hemodynamics have been attributed mainly to methodical and species differences. In the present study contrast-enhanced magnetic resonance imaging (MRI) perfusion measurement was used to analyze the influence of hyperoxia (fraction of inspired oxygen (FiO2) = 1.0) on regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) in awake, normoventilating volunteers (n = 19). Furthermore, the experiment was repeated in 20 volunteers for transcranial Doppler sonography (TCD) measurement of cerebral blood flow velocity in the middle cerebral artery (CBFV(MCA)). When compared to normoxia (FiO2 = 0.21), hyperoxia heterogeneously influenced rCBV (4.95 +/- 0.02 to 12.87 +/- 0.08 mL/100g (FiO2 = 0.21) vs. 4.50 +/- 0.02 to 13.09 +/- 0.09 mL/100g (FiO2 = 1.0). In contrast, hyperoxia diminished rCBF in all regions (68.08 +/- 0.38 to 199.58 +/- 1.58 mL/100g/min (FiO2 = 0.21) vs. 58.63 +/- 0.32 to 175.16 +/- 1.51 mL/100g/min (FiO2 = 1.0)) except in parietal and left frontal gray matter. CBFV(MCA) remained unchanged regardless of the inspired oxygen fraction (62 +/- 9 cm/s (FiO2 = 0.21) vs. 64 +/- 8 cm/s (FiO2 = 1.0)). Finding CBFV(MCA) unchanged during hyperoxia is consistent with the present studys unchanged rCBF in parietal and left frontal gray matter. In these fronto-parietal regions predominantly fed by the middle cerebral artery, the vasoconstrictor effect of oxygen was probably counteracted by increased perfusion of foci of neuronal activity controlling general behavior and arousal.

Pneumothorax following nasogastric feeding tube insertion in a tracheostomized patient after bilateral lung transplantation

Abstract We report the case of a pneumothorax caused by the improper placement of a nasogastric feeding tube in a tracheostomized patient after bilateral lung transplantation. We discuss the contribution of low-pressure cuffed tracheostomy tubes to the inadvertent respiratory tract misplacement of a nasogastric feeding tube, as well as the problems of nasogastric feeding tube insertion in the sedated patient, why the previously installed closed-tube thoracostomy did not prevent the pneumothorax and possible pitfalls in confirming the proper position of the nasogastric feeding tube. In conclusion, we stress that in high risk patients a nasogastric feeding tube should only be inserted under direct vision and that a subsequent routine X-ray is mandatory for confirming proper positioning.

The influence of nitrous oxide and remifentanil on cerebral hemodynamics in conscious human volunteers.

Remifentanil is increasingly used in the context of anesthesia, e.g., in patients presenting for MRI examinations, not only as an analgesic but also to replace nitrous oxide. Therefore, a comparative analysis of the effects of commonly used doses of remifentanil and of nitrous oxide on cerebral hemodynamics is warranted. The present study used contrast-enhanced magnetic resonance (MR) perfusion measurement to compare the effects of nitrous oxide (N(2)O/O(2) = 50%; n = 9) and remifentanil (0.1 microg/kg/min; n = 10) on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), and regional mean transit time (rMTT) in spontaneously breathing human volunteers. Remifentanil increased rCBF above all in basal ganglia, whereas in supratentorial gray matter the increase in rCBF was equal or even more pronounced when using nitrous oxide. In contrast, nitrous oxide produced a greater increase in rCBV in gray-matter regions than did remifentanil. In summary, nitrous oxide increased rCBV in all gray-matter regions more than did remifentanil. However, the increase in rCBF, especially in basal ganglia, was typically less pronounced than during infusion of remifentanil.

Routine handling of propofol prevents contamination as effectively as does strict adherence to the manufacturer’s recommendations

PurposePropofol is a potential vector of infection, because it contains no preservative. Thus, the manufacturer’s specific recommendations for preparing injections or infusions go beyond the guidelines commonly used in our operating rooms for preparing other iv drugs. The purpose of the present study was to determine whether in the daily routine of an operating theatre a modified propofol handling technique can prevent contamination as effectively as do the manufacturer’s handling recommendations.MethodsA total of 160 consecutive neurosurgical patients were allocated to either Group I (manufacturer’s handling recommendations: i.e., 1) disinfecting propofol vials and ampoules before filling syringes; 2) replacing empty syringes; 3) discarding all material at the end of surgery); or Group II (modified propofol handling protocol: i.e., I) refilling empty syringes; 2) renewing only the infusion line to the patient).ResultsTotal contamination rates were comparable in both groups (Group I: 14/160 (8.75%), Group II: 13/160 (8.13%) (χ2 = 0.074; P = 0.96). Frequency of contamination was not different between groups; either in sample I taken at the beginning of the procedure, (Group I: 5/80 (6.25%) vs Group II: 6/80 (7.5%); χ2 = 0.098; P = 0.76) or in sample 2, taken at the end, (Group I: 9/80 (11.25%) vs Group II: 7/80 (8.75%); χ2 = 0.278; P = 0.598).ConclusionWe conclude that in the daily routine of the operating theatre following a modified propofol handling protocol prevents contamination of propofol syringes as effectively as does adhering to the manufacturer’s specific handling recommendations. However, neither of the tested guidelines completely prevented contamination.RésuméObjectifLe propofol, ne contenant aucun agent de conservation, est un vecteur potentiel d’infection. C’est pourquoi les recommandations spécifiques du fabricant au sujet de la préparation d’injections ou de perfusions vont au delà des directives habituellement suivies dans nos salles d’opération pour la préparation d’autres médicaments intraveineux. Nous avons voulu déterminer si, en modifiant le maniement du propofol en salle d’opération, nous pouvions prévenir la contamination aussi efficacement qu’en suivant à la lettre les recommandations du fabricant.MéthodeUn total de 160 patients successifs de neurochirurgie ont été répartis en deux groupes. Pour le Groupe I on a suivi les recommandations du fabricant en 1) désinfectant les flacons et les ampoules de propofol avant de remplir les seringues; 2) remplaçant les seringues vides; 3) jetant tout le matériel à la fin de l’intervention chirurgicale. Pour le Groupe II, on a modifié le maniement du propofol en 1) remplissant les seringues vides et 2) en renouvelant seulement les tubulures à perfusion des patients.RésultatsLes taux de contamination totale sont comparables : 14/160 (8,75 %) dans le Groupe I et 13/160 (8,13 %) dans le Groupe II (χ2 = 0,074; P = 0,96). La fréquence de contamination ne diffère pas d’un groupe à l’autre, pour l’échantillon I prélevé au début de l’opération (Groupe I : 5/80 (6,25 %) vs Groupe II : 6/80 (7,5 %); χ2 = 0,098; P = 0,76) ou l’échantillon 2 à la fin (Groupe I : 9/80 (11,25 %)vs Groupe II : 7/80 (8,75 %); χ2 = 0,278; P = 0,598).ConclusionLusage quotidien d’un protocole modifié de maniement du propofol en salle d’opération prévient aussi efficacement la contamination des seringues que l’adhésion aux recommandations spécifiques du fabricant. Aucune des directives testées n’a permis d’éliminer complètement la contamination.

The impact of increased mean airway pressure on contrast‐enhanced MRI measurement of regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional mean transit time (rMTT), and regional cerebrovascular resistance (rCVR) in human volunteers

Contrast‐enhanced magnetic resonance imaging (MRI) measurement of cerebral perfusion is a diagnostic procedure increasingly gaining access to clinical practice not only in spontaneously breathing patients but also in mechanically ventilated patients. Effects of increased mean airway pressure on cerebral perfusion are entirely possible. Therefore, the present study used continuous positive airway pressure (CPAP) (12 cm H2O) to study the effects of increased mean airway pressure on cerebral perfusion in volunteers. CPAP significantly reduced regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) but increased regional mean transit time (rMTT) and regional cerebrovascular resistance (rCVR). Active vasoconstriction (e.g., arterial) and/or passive compression of capillary and/or venous vessel areas are the most likely underlying mechanisms. The number of interhemispheric differences in rCBF, rCBV, rMTT, and rCVR found at baseline rose when mean airway pressure was increased. These results, although obtained in volunteers, should be taken into consideration for the interpretation of contrast‐enhanced MRI perfusion measurements in mechanically ventilated patients with an increased positive airway pressure. Hum. Brain Mapping 11:214–222, 2000.

Sevoflurane and nitrous oxide increase regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) in a drug-specific manner in human volunteers

Anesthesia for diagnostic procedures, e.g., MRI measurements, has increasingly used sevoflurane and nitrous oxide in recent years. Sevoflurane and nitrous oxide are known cerebrovasodilatators, however, which potentially interferes with MRI examination of cerebral hemodynamics. To compare the effects of relevant equianesthetic concentrations (0.4 MAC) of both drugs on regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) we used contrast-enhanced magnetic resonance imaging (MRI) perfusion measurement, which has the advantage of providing regional anatomic resolution. Sevoflurane increased rCBF more than did nitrous oxide in all regions except in parietal and frontal gray matter. Nitrous oxide, by contrast, increased rCBV in most of the gray matter regions more than did sevoflurane. In summary we show that, in contrast to nitrous oxide, sevoflurane supratentorially reversed the anterior-posterior gradient in rCBF and typically redistributed rCBF to infratentorial gray matter. In contrast, nitrous oxide increased rCBV more than did sevoflurane. Both inhalational anesthetics had a drug-specific influence on cerebral hemodynamics, which is of importance when interpreting MRI studies of cerebral hemodynamics in anesthetized patients.

Lornoxicam characteristically modulates cerebral pain-processing in human volunteers: a functional magnetic resonance imaging study

BACKGROUND Lornoxicam like other non-steroidal anti-inflammatory drugs (NSAIDs) is widely used for postoperative pain therapy. Evaluation of the effect of lornoxicam on cerebral processing of surgical pain was thus the aim of the present functional magnetic resonance imaging (fMRI) study. METHODS An fMRI-compatible pain model that mimics surgical pain was used to induce pain rated 4-5 on a visual analogue scale (VAS) at the anterior margin of the right tibia in volunteers (n=22) after i.v. administration of saline (n=11) or lornoxicam (0.1 mg kg(-1)) (n=11). RESULTS Lornoxicam, which significantly reduced pain sensation [VAS: mean (sd) 4.6 (0.7) vs 1.2 (1.5)], completely suppressed pain-induced activation in the SII/operculum, anterior cingulate cortex, insula, parietal (inferior), prefrontal (inferior, medial), temporal (inferior, medial/superior) lobe, cerebellum, and contralateral (e.g. left-sided) postcentral gyrus (SI). Only the hippocampus and the contralateral superior parietal lobe (BA 7) were activated. CONCLUSIONS As compared with saline, lornoxicam typically suppressed pain-induced brain activation in all regions except the hippocampus. Furthermore, de novo activation was found in the contralateral, superior parietal lobe (BA 7).

In vivo magnetic resonance imaging of embryonic neural grafts in a rat model of striatonigral degeneration (multiple system atrophy).

The effects of embryonic neural transplantation in experimental models of neurodegenerative disorders are commonly assessed by behavioral tests and postmortem neurochemical or anatomical analysis. The purpose of the present study was to evaluate embryonic neuronal grafts in a novel rat model of multiple system atrophy (MSA) with the help of in vivo magnetic resonance imaging (MRI) and to correlate imaging with histological parameters. Striatonigral double lesions were created in male Wistar rats by unilateral intrastriatal injection of 3-nitropropionic acid (3-NP). Seven weeks following lesion surgery animals were divided into four transplantation groups receiving either pure mesencephalic, pure striatal, mesencephalic-striatal cografts, or sham grafts. In vivo structural imaging was performed 21 weeks after transplantation using a whole body 1.5 Tesla MR scanner. The imaging protocol comprised T2-weighted TSE and T1-weighted TIR sequences. Immunohistochemistry using DARPP-32 as striatal marker and tyrosinhydroxylase as marker for nigral neurons was performed for correlation analysis of imaging and histological parameters. The sensitivity of graft detection by in vivo MRI was 100%. The graft tissue was clearly demarcated from the remaining striatal tissue in both T2- and T1-weighted sequences. Morphometrically, cross-sectional areas of the grafts and spared intact striatum as defined by immunohistochemistry correlated significantly with measurements obtained by in vivo MRI. In conclusion, we were able to evaluate in vivo both lesion-induced damage and graft size in a 3-NP rat model of MSA using a conventional whole body 1.5 Tesla MRI scanner. Additionally, we obtained an excellent correlation between MRI and histological measurements.