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Biomedical subjects

C Kolbitsch

Publications and source records attributed to C Kolbitsch.

At least 37 records · Page 2Linked to original sources
PubMed2000

Low-dose remifentanil increases regional cerebral blood flow and regional cerebral blood volume, but decreases regional mean transit time and regional cerebrovascular resistance in volunteers.

We have used contrast media-enhanced perfusion magnetic resonance imaging MRI to measure regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional mean transit time (rMTT) and regional cerebrovascular resistance (rCVR) in volunteers at baseline and during infusion of remifentanil (0.1 microgram kg-1 min-1). Remifentanil increased rCBF and rCBV in white and grey matter (striatal, thalamic, occipital, parietal, frontal) regions, with a parallel decrease in rMTT in those regions with the exception of occipital grey matter. rCVR was decreased in all regions studied. The relative increase in rCBF was greater than that in rCBV. Cerebral haemodynamics were increased significantly in areas less rich in mu-opioid receptors with a tendency towards more pronounced increases in rCBF and rCBV in pain-processing areas. Furthermore, interhemispheric differences in rCBF, rCBV and rMTT found prior to drug administration were almost eliminated during infusion of remifentanil. We conclude that, apart from direct and indirect cerebrovascular effects of remifentanil, these findings are consistent with cerebral excitement and/or disinhibition.

Adult↗
PubMed2000

The effects of remifentanil on cerebral capacity in awake volunteers.

UNLABELLED: Remifentanil, a short-acting potent mu-opioid agonist proposed for intraoperative analgesia but also for postoperative pain therapy, has not been investigated with regard to the effects of the drug on cerebral capacity in awake humans. We assessed cerebral capacity noninvasively by means of phase-contrast magnetic resonance imaging measurement of systolic cerebrospinal fluid peak velocity in the aqueduct of Sylvius before and during infusion of remifentanil (0.1 microg. kg(-1). min(-1) IV) in normocapnic humans. Remifentanil had no significant effect on systolic cerebrospinal fluid peak velocity as compared with baseline (mean +/- SD): baseline, -4.3 +/- 1.3 cm/s versus remifentanil (0.1 microg. kg(-1). min(-1)): -4.7 +/- 1.0 cm/s. Small-dose remifentanil (0.1 microg. kg(-1). min(-1)) did not influence cerebral capacity in healthy, awake volunteers free of intracranial pathology. IMPLICATIONS: Knowledge about the influence of remifentanil on cerebral capacity is crucial before routine use of the drug in neuroanesthesia. Thus, we assessed the influence of remifentanil on cerebral capacity noninvasively by means of phase-contrast magnetic resonance imaging measurement of systolic cerebrospinal fluid peak velocity in the aqueduct of Sylvius in humans.

Adult↗
PubMed2000

A subanesthetic concentration of sevoflurane increases regional cerebral blood flow and regional cerebral blood volume and decreases regional mean transit time and regional cerebrovascular resistance in volunteers.

Inhaled anesthetics exert metabolically mediated effects on cerebral blood vessels both directly and indirectly. We investigated the effects of a 0.4 minimum alveolar subanesthetic concentration of sevoflurane on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional cerebrovascular resistance (rCVR), and regional mean transit time (rMTT) in volunteers by means of contrast-enhanced magnetic resonance imaging perfusion measurement. Sevoflurane increased rCBF by 16% to 55% (control, 55. 03 +/- 0.33 to 148.83 +/- 1.9 mL. 100 g(-1). min(-1); sevoflurane, 71.75 +/- 0.36 to 193.26 +/- 2.14 mL. 100 g(-1). min(-1)) and rCBV by 7% to 39% (control, 4.66 +/- 0.03 to 10.04 +/- 0.12 mL/100 g; sevoflurane, 5.04 +/- 0.03 to 13.6 +/- 0.15 mL/100 g); however, sevoflurane decreased rMTT by 7% to 18% (control, 3.75 +/- 0.04 to 5. 39 +/- 0.04 s; sevoflurane, 3.4 +/- 0.03 to 4.44 +/- 0.03 s) and rCVR by 22% to 36% (control, 0.74 +/- 0.01 to 1.9 +/- 0.2 mm Hg/[mL. 100 g(-1). min(-1)]; sevoflurane, 0.54 +/- 0.01 to 1.41 +/- 0.01 mm Hg/[mL. 100 g(-1). min(-1)]). Interhemispheric differences in rCBF, rCBV, and rCVR were markedly reduced after the administration of sevoflurane. These findings are consistent with the known direct vasodilating effect of sevoflurane. The decrease in rMTT further shows that rCBF increases more than does rCBV. Furthermore, we can show that the observed increase in rCBF during inhalation of sevoflurane is not explained by vasodilation alone.

Adult↗
PubMed2000

Sevoflurane (0.4 MAC) does not influence cerebral compliance in healthy individuals.

The use of sevoflurane is favored for its rapid onset and offset of anesthesia as well as good intraoperative titratability of the anesthetic. With regard to neuroanesthesia, the reported effects of sevoflurane on cerebral hemodynamics and cerebrospinal fluid dynamics are inconsistent. We used phase-contrast magnetic resonance imaging measurement of systolic cerebrospinal fluid peak velocity (CSFVPeak) to evaluate the effect of sevoflurane on cerebral compliance in healthy individuals. During administration of 0.4 MAC sevoflurane, systolic CSFVPeak in the aqueduct of Sylvius remained unchanged, thereby indicating unaffected cerebral compliance: (CSFVPeak baseline: -3.1 +/- 1.0 cm/s vs. sevoflurane: -3.0 +/- 1.2 cm/s). We conclude that low-dose administration of sevoflurane does not influence cerebral compliance in healthy individuals, but the influence of coexisting intracranial pathology or comedications on cerebral compliance requires further clinical investigation.

Adult↗
PubMed2000

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.

Analysis of Variance↗
PubMed1999

The influence of increasing concentrations of nitrous oxide on cerebral blood flow velocity in hypocapnic patients with brain tumours.

An increase of more than 50% in cerebral blood flow velocity in the middle cerebral artery was recently reported in hypocapnic volunteers, while inhaling 50% nitrous oxide. We measured cerebral blood flow velocity in the middle cerebral artery in 10 anaesthetized hypocapnic (ETCO2 = 25 mmHg) patients with brain tumours while administering increasing concentrations of nitrous oxide. At an end-tidal concentration of 50% and 70% nitrous oxide in oxygen, neither mean arterial pressure (base-line: 84 +/- 8 mmHg vs. (50% nitrous oxide): 82 +/- 9 mmHg and (70% nitrous oxide): 80 +/- 8 mmHg) nor cerebral blood flow velocity in the middle cerebral artery (base-line: 32 +/- 7 cm s-1 vs. (50% nitrous oxide): 34 +/- 8 cm s-1 and (70% nitrous oxide): 34 +/- 9 cm s-1) changed significantly. The data from our clinical investigation indicate that administration of increasing concentrations of nitrous oxide to already anaesthetized and hypocapnic patients does not change cerebral blood flow velocity in the middle cerebral artery.

Adult↗
PubMed1999

National publication output in medical research.

OBJECTIVE: Both the total number of publications and the number of publications in high-ranking journals determine a country's reputation in scientific research. A predominance of national authors in a country's international high-ranking journals has occasionally been presumed. We therefore analysed the publication output of various countries and the proportion of national authors in international high-ranking journals. METHODS: The database EMBASE (Excerpta Medica) by means of the online service Dialog was used to analyse the national publication output of various countries during the years 1986 to 1990 and 1991 to 1995 and the proportion of national authors in The Lancet and The New England Journal of Medicine (NEJM.). RESULTS: American and British publications played the leading roles in the total number of medical publications from 1986 to 1990 (35.6% and 8.8%, respectively) and also from 1991 to 1995 (34.3% and 9.1%, respectively). A more detailed analysis revealed an unexpectedly high national publication output (publications per million inhabitants) of smaller countries, which exceeded that of larger nations during both periods studied (national publication output 1986-90 vs. 1991-95: Israel: (3386 vs. 3447), Sweden: (3303 vs. 3620), Switzerland: (2930 vs. 3722), Denmark: (2884 vs. 3167), UK: (2186 vs. 2825), USA: (2042 vs. 2388)). Furthermore, the proportion of national authors during both periods (1986-90 vs. 1991-95) studied was 41.8% vs. 34.1% in the case of The Lancet and 77.9% vs. 69.5% in the case of The New England Journal of Medicine. CONCLUSIONS: The present study found an unexpectedly high national publication output of smaller countries as well as a clearly disproportionate number of published articles from national authors in The Lancet and the NEJM during the years 1986 to 1990 and 1991 to 1995.

Databases as Topic↗
PubMed1999

Bacterial contamination of needles used for spinal and epidural anaesthesia.

We have investigated prospectively the incidence of bacterial contamination of 114 spinal and 20 epidural needles collected immediately after lumbar puncture of the subarachnoid or epidural space. Bacteriological examination revealed bacterial contamination of 24 (17.9%) of the needles, mainly coagulase-negative staphylococci (21; 15.7%) followed by yeasts (2; 1.5%), enterococcus (1; 0.8%), pneumococcus (1; 0.8%) and micrococcus (1; 0.8%). Our results suggest that even during aseptic puncture for lumbar anaesthesia, there is a significant rate of needle contamination.

Adult↗
PubMed1999

Effects of hyperoxia and hypocapnia on regional venous oxygen saturation in the primary visual cortex in conscious humans.

Hyperoxia can improve oxygen delivery in patients exposed to hypocapnia for neurosurgical procedures but this effect may be modified by regional differences in the degree of hypocapnic vasoconstriction. Using functional magnet resonance imaging (fMRI), we have investigated the influence of hyperoxia on blood flow and blood oxygenation in the primary visual cortex in hypocapnic volunteers. Consecutive fMRI measurements were performed in 10 awake, male volunteers during hypocapnia (mean PE'CO2 3.3 (SD 0.1) kPa) and normocapnia (PE'CO2 5.3 (0.1) kPa) at FIO2 values of 0.21 and 1.0, respectively. Hypocapnia significantly reduced the pixel count in the primary visual cortex (median 169 (quartiles 34-246) vs 21 (0-40) pixels at an FIO2 of 0.21). Additional hyperoxia had no influence on this reduction in pixel count (16 (0-28) pixels at FIO2 1.0 vs 21 (0-40) pixels at FIO2 0.21). Hyperoxia did not influence hypocapnic vasoconstriction in the primary visual cortex. These data suggest that in the primary visual cortex, administration of oxygen alone may not be sufficient to improve oxygen delivery under hypocapnic conditions.

Adult↗
PubMed1999

Phase-contrast MRI measurement of systolic cerebrospinal fluid peak velocity (CSFV(peak)) in the aqueduct of Sylvius: a noninvasive tool for measurement of cerebral capacity.

BACKGROUND: Cerebrospinal fluid (CSF) outflow to intra- and extracranial subarachnoid spaces caused by arterial inflow to the brain predominantly compensates systolic increases in cerebral blood volume. Phase-contrast magnetic resonance imaging is a new tool for noninvasive assessment of CSF displacement by measuring CSF peak velocity (CSFV(Peak)). The authors tested this new tool in an experimental human model of increased intracranial pressure and reduced cerebral capacity by means of continuous positive airway pressure (CPAP) breathing. METHODS: The authors investigated systolic CSFV(Peak) in the aqueduct of Sylvius in 11 awake, normocapnic (end-tidal carbon dioxide [ET(CO2)] = 40 mmHg) volunteers without CPAP and at two different CPAP levels (6 and 12 cm H2O) by means of electroencephalography-gated phase-contrast magnetic resonance imaging. RESULTS: Administration of 6 cm H2O CPAP did not change systolic CSFV(Peak) (-4.9+/-2.8 cm/s vs. control: -5.1+/-2.7 cm/s), whereas 12 cm H2O CPAP significantly reduced systolic CSFV(Peak) (-4.0+/-1.8 cm/s vs. control: -5.1+/-2.7 cm/s; P < 0.05). CONCLUSIONS: These findings in awake volunteers show that monitoring CSFV(Peak) in the aqueduct of Sylvius is a sensitive method for detecting even minor impairment of cerebral capacity caused by experimentally induced increases in intracranial pressure.

Adult↗
PubMed1999

Effect of fluvoxamine on sufentanil antinociception and tolerance under chronic intravenous infusion in rats.

Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), significantly potentiates analgesia when administered in animals together with opioids. The aim of the present study was to investigate the effects of fluvoxamine on sufentanil antinociception and tolerance. Following animal care committee approval, the effects of continuous infusions of fluvoxamine and sufentanil were studied in behavioural tests (hot-plate test, tail-flick test, catalepsy test) in Sprague-Dawley rats with a jugular vein catheter. Saline was administered as a control. The time-effect curves for continuous intravenous sufentanil indicate dose-related antinociception and rapid development of tolerance in the hot-plate and tail-flick tests. Co-administration of fluvoxamine with continuous sufentanil enhances antinociception and attenuates development of tolerance, most clearly seen in the tail-flick test. Fluvoxamine alone and saline were not effective. No animal showed catalepsy. As a side effect we observed a marked loss of body weight. The IC50 values of sufentanil binding with and without fluvoxamine addition are 0.56+/-0.17 nM and 0.3+/-0.15 nM, respectively, indicating no direct effect on the occupancy of sufentanil on the mu-receptor by this serotonin reuptake inhibitor. In conclusion, we were able to show that the combination of an opioid with an SSRI at low doses improves analgesia and decreases development of tolerance in nociceptive tests in rats. The clinical implications of these promising results in an animal model, however, await further investigation.

Analgesics, Opioid↗
PubMed1997

[Acceptance of an Ethics Committee (International Review Board)].

The work input of an institutional review board, the satisfaction or dissatisfaction of project applicants with its decisions, as well as the amount of time needed for preparatory and follow-up work for projects submitted to the board were surveyed in a questionnaire. An analysis of the status quo provided proposals for improvement, with the aim of increasing the satisfaction of all parties involved. Questionnaires were returned by 41.4% (101/244) of the specialist doctors surveyed. Of these, 42 were doctors who had submitted projects for review and whose evaluation was used for the study. The proportion of trained "clinical review doctors" was 14.3%. Analysis of work input showed that 13.5 +/- 15.2 hours were invested before submitting a project and 6.3 +/- 9.3 hours in the follow-up. Although the board's work was given a satisfactory grading with a score of 2.8 +/- 1.0, the surveyed satisfaction/importance profile showed marked deficits in many areas, primarily in organization and communication, as well as in the examination and evaluation of projects. The suggestions for improvement above all requested the introduction of a review system employing specialists from outside the institution or from other disciplines, standardization of project submission, optimization of organization and improvement in communication. In summary, the institutional review board plays an important role in clinical research. The acceptance of a review board's work, however, can only be improved when the suggestions for improvement are realized step by step. The results of this evaluation and the proposed solutions can also help other boards improve their work. At any rate, it would be desirable to take a new look in several years' time at how the proposals worked out in this study have been implemented.

Austria↗
PubMed1997

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

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 conclusions, 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.

Humans↗
PubMed1997

Quotation accuracy in neuroanesthesiologic research.

A considerable number of quotational inaccuracies have been detected in medical and surgical publications in the past. Our study investigated the quotational accuracy of selected references of 32 scientific publications in six anesthesia journals referring to a single article published in a 1973 issue of the British Journal of Anaesthesia. In four (12.5%) articles, the quotation was in contradiction to the primary author's statement; in 15 (46.9%) articles, it was selective; and in 13 (40.6%) publications, it was in complete agreement with the important statements made in the original article. These results suggest that quotational inaccuracy is also evident in neuroanesthesiologic research. This problem deserves increased attention by authors as well as by reviewers and journal editors.

Anesthesiology↗
PubMed1997

Effects of normo- and hypocapnic nitrous-oxide-inhalation on cerebral blood flow velocity in patients with brain tumors.

Nitrous oxide (N2O) use during anesthesia for intracranial procedures has been a subject of controversy in the past. To date, the isolated influence of N2O on mean cerebral blood flow velocity in the middle cerebral artery (VMCA) has not been investigated during hypocapnia in patients with brain tumors. We compared VMCA during normocapnic (ETCO2: 40 mm Hg) and hypnocapnic (ETCO2: 25 mm Hg) inhalation of air and 50% nitrous oxide in oxygen N2O/O2 in eight patients with unilateral brain tumors on both the tumor side and the healthy side. Six patients completed the study. Mean VMCA increased during normocapnic inhalation of N2O/O2 (tumor side: 86 +/- 16 cm sec-1; healthy side: 74 +/- 17 cm sec-1) when compared with air (tumor side: 72 +/- 18 cm sec-1; healthy side: 62 +/- 14 cm sec-1, p < 0.01), whereas during hyperventilation VMCA decreased on both sides (p < 0.001). Mean VMCA values were quite similar during hypocapnic inhalation of 50% N2O/O2 (tumor side: 50 +/- 12 cm sec-1; healthy side: 45 +/- 13 cm sec-1) and air (tumor side: 51 +/- 14 cm sec-1; healthy side: 45 +/- 12 cm sec-1). The data of our study suggest that in patients with cerebral tumors the N2O-induced increase in mean VMCA can be completely reversed by hyperventilation.

Adult↗
PubMed1997

Hypocapnia reverses the fentanyl-induced increase in cerebral blood flow velocity in awake humans.

Investigations on the effects of opioids on cerebrovascular dynamics have repeatedly demonstrated mild to moderate increases in cerebral blood flow velocity in the middle cerebral artery (CBFVMCA), cerebral blood flow, and cerebrospinal fluid pressure in humans and animals. However, the influence of hypocapnia on these fentanyl effects has not been investigated. We compared mean CBFVMCA during normo- and hypocapnia before and after administration of fentanyl (2.5 micrograms/kg i.v.) in 20 awake humans. During normocapnia (end-tidal carbon dioxide [ETCO2] 40 mmHg) fentanyl significantly increased mean CBFVMCA (60 +/- 10 cm/s vs. 81 +/- 12 cm/s [mean +/- SD]; p < 0.01), whereas during hypocapnia (ETCO2 25 mmHg) mean CBFVMCA values were identical (40 +/- 7 cm/s vs. 40 +/- 7 cm/s) before and after fentanyl administration. These results confirm previous findings that administration of fentanyl increases CBFVMCA, but, more importantly, clearly indicate that hypocapnia reverses this potentially undesirable effect.

Adult↗