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  • 1
    ISSN: 1432-1912
    Keywords: Clonidine ; Morphine ; Intrathecal ; Spinal cord ; Opioid tolerance ; Alpha 2 adrenoceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous animal studies have shown the antinociceptive effects of intrathecal clonidine and intrathecal morphine to be synergistic. This study investigated the intrathecal administration of multiple doses of this drug combination to examine the rate of development of tolerance and to determine whether there was any toxic effect on the spinal cord. Rats with indwelling intrathecal catheters were given saline, morphine (2.5–7.5 μg), clonidine (17.5 μg), or clonidine (17.5 μg) plus morphine (1 μg) intrathecally twice daily for 41/2 days (total of 9 doses). Hot plate and tail flick tests were conducted after the first, fifth and ninth doses. After the ninth dose animals were killed and their spinal cords were removed for histological examination. Tolerance developed to the antinociceptive effects of the drug combination, but at a slower rate than to morphine alone. No evidence of toxicity or injury to the spinal cord was observed other than changes which could be ascribed to the presence of the catheter.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 22 (1994), S. 481-498 
    ISSN: 1573-8744
    Keywords: anesthetics local ; bupivacaine ; pharmacokinetics ; enantiomers ; administration rate ; dosage regimen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bupivacaine is used as a racemate. In previous studies the mean total body clearance ofR(+)-bupivacaine was found to be greater thanS(−)-bupivacaine by 65% after iv bolus dose of separate enantiomers and by 20% after iv infusion to steady state of racemate. The present studies were performed to determine whether different study designs using different iv dosage regimens could influence the pharmacokinetic parameters determined for either bupivacaine enantiomer. rac-Bupivacaine·HCl was administered iv to 6 adult Merino ewes by bolus, brief infusion, and prolonged infusion. Arterial blood concentrations ofR(+)- andS(−)-bupivacaine were measured by enantioselective HPLC. These regimens consistently produced lower arterial blood concentrations ofR(+)-bupivacaine thanS(−)-bupivacaine due toR(+)-bupivacaine having a greater initial dilution volume by 16 (95%CI=3–29)%, volume of distribution at steady state equilibrium by 32 (95%CI=17–32)% and mean total body clearance by 28 (95%CI=21–35)%. The slow half-life ofR(+)-bupivacaine, however, was found to be 15 (95%CI=0–31)% longer than that ofS(−)-bupivacaine. The difference between enantiomers in mean total body clearance thus was similar to the previous study based upon infusion to steady state of rac-bupivacaine. Differences in pharmacokinetics attributable to the dosage regimen consisted of a greater mean total body clearance forR(+)-bupivacaine along with a smaller terminal half life with the bolus regimen and a longer half-life ofS(−)-bupivacaine after prolonged infusion. Differences in pharmacokinetics between the bupivacaine enantiomers occurred consistently in both distribution and clearance but the magnitude of the effect was less than 50% in each case. Systematic differences in pharmacokinetics associated with the dosage regimen were found mainly in terminal half-life. Dosage regimen, thus, was found to influence the pharmacokinetic results found experimentally and is therefore a significant variable in its own right.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of clinical monitoring and computing 13 (1997), S. 109-113 
    ISSN: 1573-2614
    Keywords: pulse oximetry ; oxyhemoglobin saturation ; movement artefact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objectives. The Nellcor N-3000 pulse oximeter is designed to be ableto identify signal artefact related to movement of the body part to which theprobe is attached. It may therefore provide a reliable means of monitoringarterial oxyhemoglobin saturation (SpO2) in awake, movingpatients. This study compared the Nellcor N-3000 and N-200 pulse oximeters interms of their ability to identify readings associated with movement, in agroup of volunteers making standardized movements. Methods. Thirty-sixvolunteers were studied. Volunteers breathed room air throughout the study.SpO2 of each volunteer was monitored by both a Nellcor N-200and a Nellcor N-3000 simultaneously on both hands. Volunteers made a seriesof five standardized movements, each lasting one minute, with each hand duringthe monitoring session, while SpO2 and oximeter status wererecorded from all four oximeters. The mean SpO2 reading wascalculated during each movement. SpO2 readings which theoximeter identified as being associated with movement, pulse search notlocked, sensor not attached, or break in communications were excluded fromanalysis. Results. The N-3000 rejected from 17 to 78% of readings takenduring movement, compared to 0 to 2% with the N-200. Although the remainingreadings of both types of oximeters were subject to some movement artefact,which led to spuriously low SpO2, this was significantly lesswith the N-3000. Conclusions. The Nellcor N-3000 pulse oximeter is able,to some extent, to identify movement artefact. It should offer an advantageover the N-200 when monitoring moving patients.
    Type of Medium: Electronic Resource
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