| Modifying the baricity of local anesthetics for spinal anesthesia by temperature adjustment: model calculations. | |
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MedLine Citation:
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PMID: 16871069 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND: Although local anesthetics (LAs) are hyperbaric at room temperature, density drops within minutes after administration into the subarachnoid space. LAs become hypobaric and therefore may cranially ascend during spinal anesthesia in an uncontrolled manner. The authors hypothesized that temperature and density of LA solutions have a nonlinear relation that may be described by a polynomial equation, and that conversion of this equation may provide the temperature at which individual LAs are isobaric. METHODS: Density of cerebrospinal fluid was measured using a vibrating tube densitometer. Temperature-dependent density data were obtained from all LAs commonly used for spinal anesthesia, at least in triplicate at 5 degrees, 20 degrees, 30 degrees, and 37 degrees C. The hypothesis was tested by fitting the obtained data into polynomial mathematical models allowing calculations of substance-specific isobaric temperatures. RESULTS: Cerebrospinal fluid at 37 degrees C had a density of 1.000646 +/- 0.000086 g/ml. Three groups of local anesthetics with similar temperature (T, degrees C)-dependent density (rho) characteristics were identified: articaine and mepivacaine, rho1(T) = 1.008-5.36 E-06 T2 (heavy LAs, isobaric at body temperature); L-bupivacaine, rho2(T) = 1.007-5.46 E-06 T2 (intermediate LA, less hypobaric than saline); bupivacaine, ropivacaine, prilocaine, and lidocaine, rho3(T) = 1.0063-5.0 E-06 T (light LAs, more hypobaric than saline). Isobaric temperatures (degrees C) were as follows: 5 mg/ml bupivacaine, 35.1; 5 mg/ml L-bupivacaine, 37.0; 5 mg/ml ropivacaine, 35.1; 20 mg/ml articaine, 39.4. CONCLUSION: Sophisticated measurements and mathematic models now allow calculation of the ideal injection temperature of LAs and, thus, even better control of LA distribution within the cerebrospinal fluid. The given formulae allow the adaptation on subpopulations with varying cerebrospinal fluid density. |
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Authors:
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Axel R Heller; Katrin Zimmermann; Kristin Seele; Thomas Rössel; Thea Koch; Rainer J Litz |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Anesthesiology Volume: 105 ISSN: 0003-3022 ISO Abbreviation: Anesthesiology Publication Date: 2006 Aug |
Date Detail:
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Created Date: 2006-07-27 Completed Date: 2006-09-08 Revised Date: 2007-05-11 |
Medline Journal Info:
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Nlm Unique ID: 1300217 Medline TA: Anesthesiology Country: United States |
Other Details:
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Languages: eng Pagination: 346-53 Citation Subset: AIM; IM |
Affiliation:
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Department of Anesthesiology and Intensive Care Medicine, University Hospital Carl Gustav Carus, Dresden, Germany. axel.heller@mailbox.tu-dresden.de |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Air Pressure Algorithms* Anesthesia, Spinal* Anesthetics, Local / cerebrospinal fluid, chemistry* Bupivacaine / cerebrospinal fluid, chemistry Cerebrospinal Fluid / chemistry Databases, Factual Humans Models, Statistical Temperature* |
| Chemical | |
Reg. No./Substance:
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0/Anesthetics, Local; 2180-92-9/Bupivacaine |
| Comments/Corrections | |
Comment In:
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Anesthesiology. 2007 Apr;106(4):882; author reply 882-3
[PMID:
17413939
]
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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