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Tantry TP, Karanth H, Shenoy SP, Ayya SV, Shetty PK, Adappa KK. Isoflurane versus sevoflurane with interscalene block for shoulder arthroscopic procedures: Value of process capability indices as an additional tool for data analysis. Indian J Anaesth 2016; 60:939-947. [PMID: 28003697 PMCID: PMC5168898 DOI: 10.4103/0019-5049.195488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND AND AIMS Hypotensive anaesthesia reduces intra-articular bleed and promotes visualisation during arthroscopy. The haemodynamic effects of inhalational agents isoflurane and sevoflurane were studied extensively, and both were found to reduce mean arterial pressures (MBP) to an equivalent magnitude. We investigated the relative ability of isoflurane vis-a-vis sevoflurane to maintain the target systolic blood pressure (SBP) in patients undergoing shoulder arthroscopic procedures. METHODS In a prospective randomised study, 59 patients in two groups of 30 and 29 patients each received concomitant general anaesthesia (1.2-1.5 MAC of isoflurane and sevoflurane) and interscalene brachial plexus block. Nitrous oxide was used in both groups. Intraoperatively, serial blood pressure recordings of SBP, diastolic blood pressure (DBP), MBP and heart rates were done at every 3rd min intervals. The manipulations needed to achieve target SBP (T = 90 mmHg) for optimal arthroscopic visualisation and treat unacceptable hypotensive episodes were noted. Conventional statistical tests and process capability index (PCI) evaluation were both deployed for data analysis. RESULTS Lower mean SBP and DBPs were recorded for isoflurane patients as compared to sevoflurane (P < 0.05, for mean, maximum and minimum recordings). Higher mean heart rates were recorded for isoflurane (P < 0.05). PCIs indicated that isoflurane was superior to sevoflurane in the ease of achieving target SBP of 90 mmHg as well as maintaining blood pressures in the range of 80-100 mmHg. CONCLUSION Isoflurane provides better intraoperative haemodynamic status vis-a-vis sevoflurane in patients undergoing shoulder arthroscopic surgery with preliminary interscalene blockade. The PCI can be a useful additional medical data analysis tool.
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Affiliation(s)
- Thrivikrama Padur Tantry
- Department of Anaesthesiology, A J Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka, India
| | - Harish Karanth
- Department of Anaesthesiology, A J Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka, India
| | - Sunil P Shenoy
- Department of Urology, A J Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka, India
| | - Shreekantha V Ayya
- Department of Quality, Infosys Limited, Electronics City, Phase 1, Bengaluru, Karnataka, India
| | - Pramal K Shetty
- Department of Anaesthesiology, A J Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka, India
| | - Karunakara K Adappa
- Department of Anaesthesiology, A J Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka, India
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Pérez-Isidoro R, Sierra-Valdez FJ, Ruiz-Suárez JC. Anesthetic diffusion through lipid membranes depends on the protonation rate. Sci Rep 2014; 4:7534. [PMID: 25520016 PMCID: PMC4269894 DOI: 10.1038/srep07534] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 11/26/2014] [Indexed: 12/16/2022] Open
Abstract
Hundreds of substances possess anesthetic action. However, despite decades of research and tests, a golden rule is required to reconcile the diverse hypothesis behind anesthesia. What makes an anesthetic to be local or general in the first place? The specific targets on proteins, the solubility in lipids, the diffusivity, potency, action time? Here we show that there could be a new player equally or even more important to disentangle the riddle: the protonation rate. Indeed, such rate modulates the diffusion speed of anesthetics into lipid membranes; low protonation rates enhance the diffusion for local anesthetics while high ones reduce it. We show also that there is a pH and membrane phase dependence on the local anesthetic diffusion across multiple lipid bilayers. Based on our findings we incorporate a new clue that may advance our understanding of the anesthetic phenomenon.
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Braun T, Wehmeier F. C–F Bond Activation of Highly Fluorinated Molecules at Rhodium: From Model Reactions to Catalysis. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201001184] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Thomas Braun
- Humboldt‐Universität zu Berlin, Institut für Chemie, Brook‐Taylor‐Str. 2 12489 Berlin, Germany, Fax: +49‐30‐2093‐6966
| | - Falk Wehmeier
- Humboldt‐Universität zu Berlin, Institut für Chemie, Brook‐Taylor‐Str. 2 12489 Berlin, Germany, Fax: +49‐30‐2093‐6966
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Eger EI. After you, please: the second Annual John W. Severinghaus Lecture on Translational Science. Anesthesiology 2010; 112:786-93. [PMID: 20216386 PMCID: PMC2862683 DOI: 10.1097/aln.0b013e3181d40f47] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Edmond I Eger
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, California
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Hughes RP. Conversion of Carbon–Fluorine Bonds α to Transition Metal Centers to Carbon–Hydrogen, Carbon–Carbon, and Carbon–Heteroatom Bonds. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200900816] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Russell P. Hughes
- Department of Chemistry, Dartmouth College, 6128 Burke Laboratories, Hanover, NH 03755, USA
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6
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Whateley TL. Literature Alerts. Drug Deliv 2008. [DOI: 10.3109/10717549609031381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Won A, Oh I, Liao M, Sonner JM, Harris RA, Laster MJ, Brosnan R, Trudell JR, Eger EI. The Minimum Alveolar Anesthetic Concentration of 2-, 3-, and 4-Alcohols and Ketones in Rats: Relevance to Anesthetic Mechanisms. Anesth Analg 2006; 102:1419-26. [PMID: 16632820 DOI: 10.1213/01.ane.0000204258.00676.98] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The Meyer-Overton hypothesis predicts that anesthetic potency correlates inversely with lipophilicity; e.g., MAC times the olive oil/gas partition coefficient equals a constant of approximately 1.82 +/- 0.56 atm (mean +/- sd) for conventional inhaled anesthetics. MAC is the minimum alveolar concentration of anesthetic required to eliminate movement in response to a noxious stimulus in 50% of subjects. In contrast to conventional inhaled anesthetics, MAC times the olive oil/gas partition coefficient for normal alcohols from methanol through octanol equals a constant one tenth as large as that for conventional inhaled anesthetics. The alcohol (C-OH) group causes a great affinity of alcohols to water, and the C-OH may tether the alcohol at the hydrophobic-hydrophilic interface where anesthetics are thought to act. We hypothesized that the position of the C-OH group determined potency, perhaps by governing the maximum extent to which the acyl portion of the molecule might extend into a hydrophobic phase. Using the same reasoning, we added studies of ketones with similar numbers of carbon atoms between the C=O group and the terminal methyl group. The results for both alcohols and ketones showed the predicted correlation, but the correlation was no better than that with carbon chain length regardless of the placement of the oxygen. The oil/gas partition coefficient predicted potency as well as, or better than, either chain length or oxygen placement. Hydrophilicity, as indicated by the saline/gas partition coefficient, also seemed to influence potency.
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Affiliation(s)
- Albert Won
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, California 94143-0464, USA
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Sewell JC, Sear JW. Determinants of volatile general anesthetic potency: a preliminary three-dimensional pharmacophore for halogenated anesthetics. Anesth Analg 2006; 102:764-71. [PMID: 16492826 DOI: 10.1213/01.ane.0000195421.46107.d0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We investigated the molecular basis for the immobilizing activity of halogenated volatile anesthetics using comparative molecular field analysis. In vivo potency data (expressed as minimum alveolar concentrations) for 69 structurally diverse anesthetics were obtained from the literature. The drugs were randomly divided into a training set (n = 52) used to derive the activity model and a test set (n = 17) used to independently assess the model's predictive power. The anesthetic structures were aligned so as to maximize their similarity in molecular shape and electrostatic potential to the most potent drug in the group, CF2H-(CF2)3-CH2OH. The conformers and alignments of the anesthetics with maximum similarity (calculated as Carbo indices) were retained and used to derive the comparative molecular field analysis models. The final model explained 94.2% of the variance in the observed activities of the training set compounds. The model showed good predictive capability for both the training set (cross-validated r2 = 0.705) and randomly excluded test set anesthetics (r2 = 0.837). Three-dimensional pharmacophoric maps were derived to identify the spatial distribution of key areas where steric and electrostatic interactions are important in determining immobilizing activity of the halogenated drugs and were compared with our previously published maps obtained for nonhalogenated volatile anesthetics.
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Affiliation(s)
- Jason C Sewell
- Nuffield Department of Anaesthetics, University of Oxford, The John Radcliffe Hospital, Headington, Oxford, UK
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Katritzky AR, Kuanar M, Fara DC, Karelson M, Acree WE, Solov'ev VP, Varnek A. QSAR modeling of blood:air and tissue:air partition coefficients using theoretical descriptors. Bioorg Med Chem 2005; 13:6450-63. [PMID: 16202613 DOI: 10.1016/j.bmc.2005.06.066] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Revised: 06/29/2005] [Accepted: 06/30/2005] [Indexed: 11/21/2022]
Abstract
Human blood:air, human and rat tissue (fat, brain, liver, muscle, and kidney):air partition coefficients of a diverse set of organic compounds were correlated and predicted using structural descriptors by employing CODESSA-PRO and ISIDA programs. Four and five descriptor regression models developed using CODESSA-PRO were validated on three different test sets. Overall, these models have reasonable values of correlation coefficients (R(2)) and leave-one-out correlation coefficients (R(cv)(2)): R(2) = 0.881-0.983; R(cv)(2) = 0.826-0.962. Calculations with ISIDA resulted in models based on atom/bond sequences involving two to three atoms with statistical parameters that were similar to those of models obtained with CODESSA-PRO (R(2) = 0.911-0.974; R(cv)(2) = 0.831-0.936). A mixed pool of molecular and fragment descriptors did not lead to significant improvement of the models.
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Affiliation(s)
- Alan R Katritzky
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, 32611, USA.
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Katritzky AR, Kuanar M, Fara DC, Karelson M, Acree WE. QSPR treatment of rat blood:air, saline:air and olive oil:air partition coefficients using theoretical molecular descriptors. Bioorg Med Chem 2004; 12:4735-48. [PMID: 15294307 DOI: 10.1016/j.bmc.2004.05.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2004] [Revised: 05/13/2004] [Accepted: 05/25/2004] [Indexed: 11/19/2022]
Abstract
A QSPR treatment has been applied to a data set that consists of 100 diverse organic compounds to relate the logarithmic function of rat blood:air, saline:air and olive oil:air partition coefficients (denoted by log K(b:a), log K(s:a), and log K(o:a), respectively), with theoretical molecular and fragment descriptors. Three QSPR models with squared correlation coefficients of 0.881, 0.926, and 0.922, respectively, were obtained. The verification of the predictive power of these models on a test set of 33 organic chemicals that were not included in the training set gave satisfactory squared correlation coefficients: 0.791 for rat blood:air, 0.794 for saline:air and 0.846 for olive oil:air.
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Affiliation(s)
- Alan R Katritzky
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-17200, USA.
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12
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Cantor RS. Breaking the Meyer-Overton rule: predicted effects of varying stiffness and interfacial activity on the intrinsic potency of anesthetics. Biophys J 2001; 80:2284-97. [PMID: 11325730 PMCID: PMC1301419 DOI: 10.1016/s0006-3495(01)76200-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Exceptions to the Meyer-Overton rule are commonly cited as evidence against indirect, membrane-mediated mechanisms of general anesthesia. However, another interpretation is possible within the context of an indirect mechanism in which solubilization of an anesthetic in the membrane causes a redistribution of lateral pressures in the membrane, which in turn shifts the conformational equilibrium of membrane proteins such as ligand-gated ion channels. It is suggested that compounds of different stiffness and interfacial activity have different intrinsic potencies, i.e., they cause widely different redistributions of the pressure profile (and thus different effects on protein conformational equilibria) per unit concentration of the compound in the membrane. Calculations incorporating the greater stiffness of perfluoromethylenic chains and the large interfacial attraction of hydroxyl groups predict the higher intrinsic potency of short alkanols than alkanes, the cutoffs in potency of alkanes and alkanols and the much shorter cutoffs for their perfluorinated analogues. Both effects, increased stiffness and interfacial activity, are present in unsaturated hydrocarbon solutes, and the intrinsic potencies are predicted to depend on the magnitude of both effects and on the number and locations of multiple bonds within the molecule. Most importantly, the intrinsic potencies of polymeric alkanols with regularly spaced hydroxyl groups are predicted to rise with increasing chain length, without cutoff; such molecules should serve to distinguish unambiguously between indirect mechanisms and direct binding mechanisms of anesthesia.
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Affiliation(s)
- R S Cantor
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA.
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Chomas JE, Dayton P, Allen J, Morgan K, Ferrara KW. Mechanisms of contrast agent destruction. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2001; 48:232-48. [PMID: 11367791 DOI: 10.1109/58.896136] [Citation(s) in RCA: 237] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Various applications of contrast-assisted ultrasound, including blood vessel detection, perfusion estimation, and drug delivery, require controlled destruction of contrast agent microbubbles. The lifetime of a bubble depends on properties of the bubble shell, the gas core, and the acoustic waveform impinging on the bubble. Three mechanisms of microbubble destruction are considered: fragmentation, acoustically driven diffusion, and static diffusion. Fragmentation is responsible for rapid destruction of contrast agents on a time scale of microseconds. The primary characteristics of fragmentation are a very large expansion and subsequent contraction, resulting in instability of the bubble. Optical studies using a novel pulsed-laser optical system show the expansion and contraction of ultrasound contrast agent microbubbles with the ratio of maximum diameter to minimum diameter greater than 10. Fragmentation is dependent on the transmission pressure, occurring in over 55% of bubbles insonified with a peak negative transmission pressure of 2.4 MPa and in less than 10% of bubbles insonified with a peak negative transmission pressure of 0.8 MPa. The echo received from a bubble decorrelates significantly within two pulses when the bubble is fragmented, creating an opportunity for rapid detection of bubbles via a decorrelation-based analysis. Preliminary findings with a mouse tumor model verify the occurrence of fragmentation in vivo. A much slower mechanism of bubble destruction is diffusion, which is driven by both a concentration gradient between the concentration of gas in the bubble compared with the concentration of gas in the liquid, as well as convective effects of motion of the gas-liquid interface. The rate of diffusion increases during insonation, because of acoustically driven diffusion, producing changes in diameter on the time scale of the acoustic pulse length, thus, on the order of microseconds. Gas bubbles diffuse while they are not being insonified, termed static diffusion. An air bubble with initial diameter of 2 microns in water at 37 degrees C is predicted to fully dissolve within 25 ms. Clinical ultrasound contrast agents are often designed with a high molecular weight core in an attempt to decrease the diffusion rate. C3F8 and C4F10 gas bubbles of the same size are predicted to fully dissolve within 400 ms and 4000 ms, respectively. Optical experiments involving gas diffusion of a contrast agent support the theoretical predictions; however, shelled agents diffuse at a much slower rate without insonation, on the order of minutes to hours. Shell properties play a significant role in the rate of static diffusion by blocking the gas-liquid interface and decreasing the transport of gas into the surrounding liquid. Static diffusion decreases the diameter of albumin-shelled agents to a greater extent than lipid-shelled agents after insonation.
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Affiliation(s)
- J E Chomas
- Division of Biomedical Engineering, University of California-Davis, Davis, CA 95616-5294, USA.
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Zhang Y, Trudell JR, Mascia MP, Laster MJ, Gong DH, Harris RA, Eger EI. The anesthetic potencies of alkanethiols for rats: relevance to theories of narcosis. Anesth Analg 2000; 91:1294-9. [PMID: 11049925 DOI: 10.1097/00000539-200011000-00045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED Meyer and Overton suggested that anesthetic potency correlates inversely with lipophilicity. Thus, MAC times the olive oil/gas partition coefficient equals an approximately constant value of 1.82 +/- 0.56 atm (mean +/- SD). MAC is the minimum alveolar concentration of anesthetic required to eliminate movement in response to a noxious stimulus in 50% of subjects. Although MAC times the olive oil/gas partition coefficient also equals an approximately constant value for normal alkanols from methanol through octanol, the value (0.156 +/- 0.072 atm) is 1/10th that found for conventional anesthetics. We hypothesized that substitution of sulfur for the oxygen in n-alkanols would decrease their saline/gas partition coefficients (i.e., decrease polarity) while sustaining lipid/gas partition coefficients. Further, we hypothesized that these changes would produce products of MAC times olive oil partition coefficients that approximate those of conventional anesthetics. To test these predictions, we measured MAC in rats, and saline and olive oil solubilities for the series H(CH(2))(n)SH, comparing the results with the series H(CH(2))(n)OH for compounds having three to six carbon atoms. As hypothesized, the alkanethiols had similar oil/gas partition coefficients, 1000-fold smaller saline gas partition coefficients, and MAC values 30 times greater than for comparable alkanols. Such findings are consistent with the notion that the greater potency of many alkanols (greater than would be predicted from conventional inhaled anesthetics and the Meyer-Overton hypothesis) results from their greater polarity. IMPLICATIONS The in vivo anesthetic potency of alkanols and alkanethiols correlates with their lipophilicity and hydrophilicity.
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Affiliation(s)
- Y Zhang
- Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0464, USA
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Zhang Y, Trudell JR, Mascia MP, Laster MJ, Gong DH, Harris RA, Eger EI. The Anesthetic Potencies of Alkanethiols for Rats: Relevance to Theories of Narcosis. Anesth Analg 2000. [DOI: 10.1213/00000539-200011000-00045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Bovill JG. Mechanisms of anaesthesia: time to say farewell to the Meyer-Overton rule. Curr Opin Anaesthesiol 2000; 13:433-6. [PMID: 17016337 DOI: 10.1097/00001503-200008000-00006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Taylor DM, Eger EI, Bickler PE. Halothane, but not the nonimmobilizers perfluoropentane and 1,2-dichlorohexafluorocyclobutane, depresses synaptic transmission in hippocampal CA1 neurons in rats. Anesth Analg 1999; 89:1040-5. [PMID: 10512287 DOI: 10.1097/00000539-199910000-00041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED Volatile anesthetics may decrease synaptic transmission at central neurons by presynaptic and/or postsynaptic actions. Nonimmobilizers are volatile compounds with lipophilicities that suggest that they should (but do not) prevent motor responses to surgical stimuli. However, nonimmobilizers interfere with learning and memory, and, thus, might be predicted to depress synaptic transmission in areas of the brain mediating memory (e.g., hippocampal CA1 neurons). To test this possibility, we stimulated the Schaffer collaterals of rat hippocampal slices and recorded from stratum pyramidale of CA1 neurons. At approximately 0.5 MAC (MAC is the minimum alveolar anesthetic concentration at one standard atmosphere that is required to eliminate movement in response to noxious stimulation in 50% of subjects), halothane decreased population spike amplitude 37% +/- 21% (mean +/- SD), increased latency 15% +/- 9%, and decreased excitatory postsynaptic potentials 16% +/- 10%. In contrast, at concentrations below (0.4 times) predicted MAC, the nonimmobilizer, 1,2 dichlorohexafluorocyclobutane (2N), slightly (not significantly) increased population spike amplitude, decreased population spike latency 9% +/- 4%, and increased excitatory postsynaptic potentials 22% +/- 16%. At concentrations above (2 times) predicted MAC, 2N did not significantly increase population spike, decreased latency 10% +/- 4%, and did not significantly change excitatory postsynaptic potentials. At 0.1 predicted MAC, a second nonimmobilizer, perfluoropentane, tended (P = 0.05) to increase (11% +/- 9%) population spike amplitude, decreased population spike latency 8% +/- 2%, and tended (P = 0.06) to increase excitatory postsynaptic potentials (9% +/- 8%). We conclude that clinically relevant concentrations of halothane depress synaptic transmission at Schaffer collateral-CA1 synapses and that the nonimmobilizers 2N and perfluoropentane have no effect or are excitatory. The Schaffer collateral-CA1 synapse may serve as a useful model for the production of immobility by volatile anesthetics, but is flawed as a model for the capacity of volatile anesthetics to interfere with memory and learning. IMPLICATIONS Halothane, but not the nonimmobilizers 1,2-dichlorohexafluorocyclobutane and perfluoropentane, inhibits hippocampal synaptic transmission at Schaffer collateral-CA1 synapses.
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Affiliation(s)
- D M Taylor
- Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA.
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Eger EI, Halsey MJ, Harris RA, Koblin DD, Pohorille A, Sewell JC, Sonner JM, Trudell JR. Hypothesis: volatile anesthetics produce immobility by acting on two sites approximately five carbon atoms apart. Anesth Analg 1999; 88:1395-400. [PMID: 10357351 DOI: 10.1097/00000539-199906000-00036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED All series of volatile and gaseous compounds contain members that can produce anesthesia, as defined by the minimum alveolar anesthetic concentration (MAC) required to produce immobility in response to a noxious stimulus. For unhalogenated n-alkanes, cycloalkanes, aromatic compounds, and n-alkanols, potency (1 MAC) increases by two-to threefold with each carbon addition in the series (e.g., ethanol is twice as potent as methanol). Total fluorination (perfluorination) of n-alkanes essentially eliminates anesthetic potency: only CF4 is anesthetic (MAC = 66.5 atm), which indicates that fluorine atoms do not directly influence sites of anesthetic action. Fluorine may enhance the anesthetic action of other moieties, such as the hydrogen atom in CHF3 (MAC = 1.60 atm), but, consistent with the notion that the fluorine atoms do not directly influence sites of anesthetic action, adding -(CF2)n moieties does not further increase potency (e.g., CHF2-CF3 MAC = 1.51 atm). Similarly, adding -(CF2)n moieties to perfluorinated alkanols (CH2OH-[CF2]nF) does not increase potency. However, adding a second terminal hydrogen atom (e.g., CHF2-CHF2 or CH2OH-CHF2) produces series in which the addition of each -CF2- "spacer" in the middle of the molecule increases potency two- to threefold, as in each unhalogenated series. This parallel stops at four or five carbon atom chain lengths. Further increases in chain length (i.e., to CHF2[CF2]4CHF2 or CHF2[CF2]5CH2OH) decrease or abolish potency (i.e., a discontinuity arises). This leads to our hypothesis that the anesthetic moieties (-CHF2 and -CH2OH) interact with two distinct, spatially separate, sites. Both sites must be influenced concurrently to produce a maximal anesthetic (immobility) effect. We propose that the maximal potency (i.e., for CHF2[CF2]2CHF2 and CHF2[CF2]3CH2OH) results when the spacing between the anesthetic moieties most closely matches the distance between the two sites of action. This reasoning suggests that a distance equivalent to a four or five carbon atom chain, approximately 5 A, separates the two sites. IMPLICATIONS Volatile anesthetics may produce immobility by a concurrent action on two sites five carbon atom lengths apart.
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Affiliation(s)
- E I Eger
- Department of Anesthesia and Perioperative Medicine, University of California, San Francisco 94143-0464, USA.
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Eger EI, Ionescu P, Laster MJ, Gong D, Hudlicky T, Kendig JJ, Harris RA, Trudell JR, Pohorille A. Minimum alveolar anesthetic concentration of fluorinated alkanols in rats: relevance to theories of narcosis. Anesth Analg 1999; 88:867-76. [PMID: 10195540 DOI: 10.1097/00000539-199904000-00035] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED The Meyer-Overton hypothesis predicts that the potency of conventional inhaled anesthetics correlates inversely with lipophilicity: minimum alveolar anesthetic concentration (MAC) x the olive oil/gas partition coefficient equals a constant of approximately 1.82 +/- 0.56 atm (mean +/- SD), whereas MAC x the octanol/gas partition coefficient equals a constant of approximately 2.55 +/- 0.65 atm. MAC is the minimum alveolar concentration of anesthetic required to eliminate movement in response to a noxious stimulus in 50% of subjects. Although MAC x the olive oil/gas partition coefficient also equals a constant for normal alkanols from methanol through octanol, the constant (0.156 +/- 0.072 atm) is one-tenth that found for conventional anesthetics, whereas the product for MAC x the octanol/gas partition coefficient (1.72 +/- 1.19) is similar to that for conventional anesthetics. These normal alkanols also have much greater affinities for water (saline/gas partition coefficients equaling 708 [octanol] to 3780 [methanol]) than do conventional anesthetics. In the present study, we examined whether fluorination lowers alkanol saline/gas partition coefficients (i.e., decreases polarity) while sustaining or increasing lipid/gas partition coefficients, and whether alkanols with lower saline/gas partition coefficients had products of MAC x olive oil or octanol/gas partition coefficients that approached or exceeded those of conventional anesthetics. Fluorination decreased saline/gas partition coefficients to as low as 0.60 +/- 0.08 (CF3[CF2]6CH2OH) and, as hypothesized, increased the product of MAC x the olive oil or octanol/gas partition coefficients to values equaling or exceeding those found for conventional anesthetics. We conclude that the greater potency of many alkanols (greater than would be predicted from conventional inhaled anesthetics and the Meyer-Overton hypothesis) is associated with their greater polarity. IMPLICATIONS Inhaled anesthetic potency correlates with lipophilicity, but potency of common alkanols is greater than their lipophilicity indicates, in part because alkanols have a greater hydrophilicity--i.e., a greater polarity.
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Affiliation(s)
- E I Eger
- Department of Anesthesia, University of California San Francisco 94143-0464, USA
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Eger EI, Koblin DD, Sonner J, Gong D, Laster MJ, Ionescu P, Halsey MJ, Hudlicky T. Nonimmobilizers and transitional compounds may produce convulsions by two mechanisms. Anesth Analg 1999; 88:884-92. [PMID: 10195542 DOI: 10.1097/00000539-199904000-00037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED Some inhaled compounds cause convulsions. To better appreciate the physical basis for this property, we correlated the partial pressures that produced convulsions in rats with the lipophilicity (nonpolarity) and hydrophilicity (polarity) of 45 compounds: 3 n-alkanes, 18 n-haloalkanes, 3 halogenated aromatic compounds, 3 cycloalkanes and 3 halocycloalkanes, 13 halogenated ethers, and 2 noble gases (He and Ne). In most cases, convulsions were quantified by averaging the alveolar partial pressures just below the pressures that caused and slightly higher pressures that did cause clonic convulsions (ED50). The ED50 did not correlate with hydrophilicity (the saline/gas partition coefficient), nor was there an obvious correlation with molecular structure. For 80% of compounds (36 of 45), the ED50 correlated closely (r2 = 0.99) with lipophilicity (the olive oil/gas partition coefficient). Perhaps because they block the effect of GABA on GABA(A) receptors, five compounds were more potent than would be predicted from their lipophilicity. Conversely, four compounds may have been less potent than would be predicted because they (like conventional inhaled anesthetics) enhance the effect of GABA on GABA(A) receptors. IMPLICATIONS Nonimmobilizers and transitional compounds may produce convulsions by two mechanisms. One correlates with lipophilicity (nonpolarity), and the other correlates with an action on GABA(A) receptors.
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Affiliation(s)
- E I Eger
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA.
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21
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Dayton PA, Morgan KE, Klibanov AL, Brandenburger GH, Ferrara KW. Optical and acoustical observations of the effects of ultrasound on contrast agents. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 1999; 46:220-32. [PMID: 18238417 DOI: 10.1109/58.741536] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Optimal use of encapsulated microbubbles for ultrasound contrast agents and drug delivery requires an understanding of the complex set of phenomena that affect the contrast agent echo and persistence. With the use of a video microscopy system coupled to either an ultrasound flow phantom or a chamber for insonifying stationary bubbles, we show that ultrasound has significant effects on encapsulated microbubbles. In vitro studies show that a train of ultrasound pulses can alter the structure of an albumin-shelled bubble, initiate various mechanisms of bubble destruction or produce aggregation that changes the echo spectrum. In this analysis, changes observed optically are compared with those observed acoustically for both albumin and lipid-shelled agents. We show that, when insonified with a narrowband pulse at an acoustic pressure of several hundred kPa, a phospholipid-shelled bubble can undergo net radius fluctuations of at least 15%; and an albumin-shelled bubble initially demonstrates constrained expansion and contraction. If the albumin shell contains air, the shell may not initially experience surface tension; therefore, the echo changes more significantly with repeated pulsing. A set of observations of contrast agent destruction is presented, which includes the slow diffusion of gas through the shell and formation of a shell defect followed by rapid diffusion of gas into the surrounding liquid. These observations demonstrate that the low-solubility gas used in these agents can persist for several hundred milliseconds in solution. With the transmission of a high-pulse repetition rate and a low pressure, the echoes from, contrast agents can be affected by secondary radiation force. Secondary radiation force is an attractive force for these experimental conditions, creating aggregates with distinct echo characteristics and extended persistence. The scattered echo from an aggregate is several times stronger and more narrowband than echoes from individual bubbles.
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Affiliation(s)
- P A Dayton
- Virginia Univ., Charlottesville, VA 22903, USA. pdayton@virginia edu
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22
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Sonner JM, Li J, Eger EI. Desflurane and the nonimmobilizer 1,2-dichlorohexafluorocyclobutane suppress learning by a mechanism independent of the level of unconditioned stimulation. Anesth Analg 1998; 87:200-5. [PMID: 9661574 DOI: 10.1097/00000539-199807000-00041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED We previously demonstrated that anesthetics and non-immobilizers suppress learning and memory in rats. In the training portion of the test, rats received a light plus a footshock and learned to associate the two, as evidenced by subsequent potentiation of the response (jumping) to light plus a noise (fear-potentiated startle). However, anesthetics and nonimmobilizers also decreased the response of animals receiving footshocks during training, which suggests that the reduction in fear-potentiated startle might reflect analgesia, rather than an impairment of learning and memory. Furthermore, although we previously demonstrated that the nonimmobilizer 2,3-dichlorohexafluorocyclobutane (2N) could completely abolish learning, we did not demonstrate the minimal dose required. In the present study, we eliminated analgesia as a confounding factor by training rats breathing desflurane and 2N with footshock intensities that produced responses at least equal to those produced in control animals. Both desflurane and 2N suppressed learning at 0.2 times the minimum alveolar anesthetic concentration (MAC) or the MAC predicted from lipid solubility, despite the increased footshock intensity. This partial pressure of desflurane equals that previously shown to suppress learning at lower footshock intensities. We conclude that suppression of learning and memory by desflurane and 2N does not result from decreased sensitivity to the unconditioned stimulus (the footshock) and that the potency of 2N is consistent with its lipophilicity. IMPLICATIONS General anesthesia eliminates recall of intraoperative events, including pain. Using an animal model, we refuted the hypothesis that lack of recall results from the analgesia (i.e., the reduced response to painful stimuli produced by inhaled drugs) rather than from a direct effect on learning.
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Affiliation(s)
- J M Sonner
- Department of Anesthesia, University of California-San Francisco 94143-0464, USA.
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Steffey EP, Laster MJ, Ionescu P, Eger EI, Emerson N. Ventilatory effects of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (2N) in swine. Anesth Analg 1998; 86:173-8. [PMID: 9428874 DOI: 10.1097/00000539-199801000-00034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
UNLABELLED Nonimmobilizers (inhaled compounds that do not suppress movement in response to a noxious stimulus) resemble anesthetics in their capacity to suppress memory, but unlike anesthetics, they can cause convulsions. Higher concentrations of nonimmobilizers may cause death, even with apparent suppression of convulsions by the concurrent administration of conventional inhaled anesthetics. We hypothesized that nonimmobilizers can depress ventilation and can cause death by adding to the depression of ventilation produced by conventional anesthetics. To test these hypotheses, we administered 1,2-dichlorohexafluorocyclobutane (2N) to four pigs anesthetized with desflurane. The addition of 2N decreased PaCO2 and tended to increase the slope of the ventilatory response to imposed increases in PETCO2. Limited results from study of two other nonimmobilizers (2,3-dichlorooctafluorobutane and perfluoropentane), in two pigs each, were consistent with the findings for 2N. However, experimental limitations (e.g., toxicity of 2,3-dichlorooctafluorobutane, and hypoxia from perfluoropentane) confound interpretation of these latter results. Our findings do not support our hypotheses--2N (and presumably all nonimmobilizers) seems to be a respiratory stimulant, not a depressant. IMPLICATIONS A new class of inhaled compounds, nonimmobilizers, allow tests of how inhaled anesthetics act. Nonimmobilizers may act like anesthetics (e.g., impair learning) or may not (e.g., do not prevent movement in response to a noxious stimulus). The present work shows that, unlike anesthetics,nonimmobilizers do not depress breathing.
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Affiliation(s)
- E P Steffey
- Department of Anesthesia, University of California-San Francisco 94143-0464, USA
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24
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Fang Z, Laster MJ, Ionescu P, Koblin DD, Sonner J, Eger EI, Halsey MJ. Effects of inhaled nonimmobilizer, proconvulsant compounds on desflurane minimum alveolar anesthetic concentration in rats. Anesth Analg 1997; 85:1149-53. [PMID: 9356117 DOI: 10.1097/00000539-199711000-00035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
UNLABELLED Anesthetics depress the central nervous system, whereas nonimmobilizers (previously called nonanesthetics) and transitional compounds having the same physical properties (e.g., solubility in lipid) do not produce anesthesia (nonimmobilizers) or are less potent anesthetics than might be predicted from their lipophilicity (transitional compounds). Potential explanations for the absent or decreased anesthetic effect of nonimmobilizer and transitional compounds include the theories that the nonimmobilizers are devoid of anesthetic effect and that transitional compounds have a decreased capacity to produce anesthesia; that the effects of these compounds are not apparent because the concentrations examined are too low; or that anesthesia, or lack thereof, results from a balance between depression and excitation (all nonimmobilizer and transitional compounds produce convulsions). To examine these issues further, we tested the effect of various multiples of the convulsive 50% effective dose (ED50) of three nonimmobilizers and one transitional compound on the minimum alveolar anesthetic concentration (MAC) of desflurane in rats. The nonimmobilizer 2,3-dichlorooctafluorobutane (NI-1), from 0.7 to 1.1 times its convulsive ED50, increased the MAC of desflurane by 14%-27%, but at 1.6 times its convulsive ED50 caused no change in MAC; the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (NI-2) did not change MAC at concentrations up to its convulsant ED50, but it increased MAC by 25% and 36% at 1.3 and 1.7 times its convulsant ED50, respectively. The nonimmobilizer flurothyl (NI-3) decreased the MAC of desflurane by 20% +/- 6% (mean +/- SD) at 0.5 times its convulsant ED50, but it caused no change at higher partial pressures (up to 7.8 times its convulsant ED50), and the transitional compound CF3CCl2-O-CF2Cl (T-1) significantly decreased MAC by 16% +/- 7% at 0.8 times its convulsant ED50, but the 6%-8% decreases in MAC at 0.4 and 1.6 times its convulsant ED50 were not significant. Thus, neither nonimmobilizer nor transitional compounds produced a consistent dose-related effect on the MAC of desflurane, and any changes were small. These results suggest that the excitation produced by transitional compounds or nonimmobilizers does not explain their limited ability or inability to produce anesthesia. The data are consistent with a decreased anesthetic efficacy of transitional compounds and the lack of efficacy of nonimmobilizers. IMPLICATIONS Inhaled compounds that do not cause anesthesia (nonimmobilizers) are used to test theories of anesthetic action. Their use presumes that a trivial explanation, such as cancelling stimulatory and depressant effects, does not explain the absence of anesthesia. The present results argue against such an explanation.
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Affiliation(s)
- Z Fang
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA
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25
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Fang Z, Laster MJ, Ionescu P, Koblin DD, Sonner J, Eger EI, Halsey MJ. Effects of Inhaled Nonimmobilizer, Proconvulsant Compounds on Desflurane Minimum Alveolar Anesthetic Concentration in Rats. Anesth Analg 1997. [DOI: 10.1213/00000539-199711000-00035] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Tang P, Yan B, Xu Y. Different distribution of fluorinated anesthetics and nonanesthetics in model membrane: a 19F NMR study. Biophys J 1997; 72:1676-82. [PMID: 9083671 PMCID: PMC1184361 DOI: 10.1016/s0006-3495(97)78813-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Despite their structural resemblance, a pair of cyclic halogenated compounds, 1-chloro-1,2,2-trifluorocyclobutane (F3) and 1,2-dichlorohexafluorocyclobutane (F6), exhibit completely different anesthetic properties. Whereas the former is a potent general anesthetic, the latter produces no anesthesia. Two linear compounds, isoflurane and 2,3-dichlorooctofluorobutane (F8), although not a structural pair, also show the same anesthetic discrepancy. Using 19F nuclear magnetic spectroscopy, we investigated the time-averaged submolecular distribution of these compounds in a vesicle suspension of phosphatidylcholine lipids. A two-site exchange model was used to interpret the observed changes in resonance frequencies as a function of the solubilization of these compounds in membrane and in water. At clinically relevant concentrations, the anesthetics F3 and isoflurane distributed preferentially to regions of the membrane that permit easy contact with water. The frequency changes of these two anesthetics can be well characterized by the two-site exchange model. In contrast, the nonanesthetics F6 and F8 solubilized deeply into the lipid core, and their frequency change significantly deviated from the prediction of the model. It is concluded that although anesthetics and nonanesthetics may show similar hydrophobicity in bulk solvents such as olive oil, their distributions in various regions in biomembranes, and hence their effective concentrations at different submolecular sites, may differ significantly.
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Affiliation(s)
- P Tang
- Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh, Pennsylvania 15261, USA
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27
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Eger EI, Koblin DD, Harris RA, Kendig JJ, Pohorille A, Halsey MJ, Trudell JR. Hypothesis: inhaled anesthetics produce immobility and amnesia by different mechanisms at different sites. Anesth Analg 1997; 84:915-8. [PMID: 9085981 DOI: 10.1097/00000539-199704000-00039] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- E I Eger
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA
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29
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Fang Z, Laster MJ, Gong D, Ionescu P, Koblin DD, Sonner J, Eger EI, Halsey MJ. Convulsant Activity of Nonanesthetic Gas Combinations. Anesth Analg 1997. [DOI: 10.1213/00000539-199703000-00032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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30
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Fang Z, Laster MJ, Gong D, Ionescu P, Koblin DD, Sonner J, Eger EI, Halsey MJ. Convulsant activity of nonanesthetic gas combinations. Anesth Analg 1997; 84:634-40. [PMID: 9052316 DOI: 10.1097/00000539-199703000-00032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Most nonanesthetics (inhaled compounds that neither cause anesthesia when given alone nor decrease the partial pressure of a known inhaled anesthetic required to produce anesthesia) and transitional compounds (inhaled compounds that are less potent than would be predicted by the Meyer-Overton hypothesis) cause convulsions. A possible exception is the perfluoroalkane series of nonanesthetics. The present study tested whether perfluoroalkanes do provide an exception. Further, we tested whether the convulsant effects of nonanesthetic and transitional compounds were additive. The nonanesthetic perfluoropropane caused convulsions at 7.5 +/- 0.7 atm (mean +/- SD). Convulsions also were produced by perfluorocyclobutane (0.976 +/- 0.002 atm), 1,2-dichlorotetrafluoroethane (0.358 +/- 0.011 atm), 2,3-dichlorooctafluorobutane (0.085 +/- 0.007 atm), 1,2-dichlorohexafluorocyclobutane (0.055 +/- 0.007 atm), and flurothyl (0.00156 +/- 0.00039 atm). Of these, 1,2-dichlorotetrafluoroethane is a transitional compound, the remainder being nonanesthetics. The combination of flurothyl plus 1,2-dichlorohexafluorocyclobutane gave evidence of antagonism (a 17% +/- 21% deviation from additivity; P < 0.05), whereas the combination of 1,2-dichlorotetrafluoroethane plus 2,3-dichlorooctafluorobutane gave evidence of synergy (a -13% +/- 8% deviation from additivity; P < 0.05). The combinations of perfluoropropane plus perfluorocyclobutane (-4% +/- 15%), and perfluoropropane plus 1,2-dichlorohexafluorocyclobutane (-1% +/- 26%) did not produce results that deviated significantly from additivity. We conclude that pairs of these compounds either produce convulsions in an additive manner, a finding consistent with (but not proving) a common mode of action; or deviate modestly from additivity, a finding suggesting that at least a portion of the mechanistic basis for convulsions might differ, particularly for flurothyl plus other nonanesthetics, or for the combination of non-anesthetics and transitional compounds.
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Affiliation(s)
- Z Fang
- Department of Anesthesia, S-455, University of California, San Francisco 94143-0464, USA
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31
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Fang Z, Sonner J, Laster MJ, Ionescu P, Kandel L, Koblin DD, Eger EI, Halsey MJ. Anesthetic and convulsant properties of aromatic compounds and cycloalkanes: implications for mechanisms of narcosis. Anesth Analg 1996; 83:1097-104. [PMID: 8895293 DOI: 10.1097/00000539-199611000-00035] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We examined the anesthetic and convulsant properties of 16 unfluorinated to completely fluorinated aromatic compounds, having six to nine carbon atoms (e.g., benzene to 1,3,5-tris(trifluoromethyl)benzene), and four cycloalkanes (cyclopentane to cyclooctane). Benzene, fluorobenzene, toluene, p-xylene, ethylbenzene, and cyclopentane caused excitation (twitching, jerking, and hyperactivity), and three aromatic compounds (perfluorotoluene, p-difluorotoluene and 1,3,5-tris(trifluoromethyl)benzene) and three cycloalkanes (cyclohexane, cycloheptane, and cyclooctane) produced convulsions. Cyclooctane and 1,3,5-tris(trifluoromethyl)benzene were nonanesthetics. Except for nonanesthetics and perfluorotoluene (too toxic to test for anesthetic potency), all compounds produced anesthesia or decreased the minimum alveolar anesthetic concentration of desflurane. Aromatic compounds were more potent and lipid-soluble than n-alkanes (data from previous report) and cycloalkanes. All three series increasingly disobeyed the Meyer-Overton hypothesis as molecular size increased. For a particular number of carbons (e.g., cyclohexane, n-hexane, and benzene), the deviation was cycloalkanes > or = normal alkanes > aromatic compounds. These results suggest that molecular shape (including "bulkiness") and size provide limited clues to the structure of the anesthetic site of action.
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Affiliation(s)
- Z Fang
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA
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Fang Z, Sonner J, Laster MJ, Ionescu P, Kandel L, Koblin DD, Eger II EI, Halsey MJ. Anesthetic and Convulsant Properties of Aromatic Compounds and Cycloalkanes. Anesth Analg 1996. [DOI: 10.1213/00000539-199611000-00035] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Eger EI, Ionescu P, Koblin DD, Weiskopf RB. Compound A: solubility in saline and olive oil; destruction by blood. Anesth Analg 1996; 83:849-53. [PMID: 8831333 DOI: 10.1097/00000539-199610000-00034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Compound A is a degradation product of sevoflurane. Knowledge of the solubility of Compound A, CH2F-O-C(=CF2)(CF3), in blood and other solvents would aid in the definition of its kinetics. Accordingly, we determined solvent/gas partition coefficients of Compound A for saline (0.166 +/- 0.002 [mean +/- SD; n = 4]) and olive oil (20.1 +/- 1.1 [n = 4]). Measurement of solubility in blood was confounded by degradation of Compound A in blood and blood components. If a mixture of 99.3% saline and 0.7% oil provides the solubility equivalent to that possessed by blood (as it does for the parent compound, sevoflurane), then blood solubility and solubility in plasma, albumin, red blood cells, or pure hemoglobin is approximately 0.31. The order of Compound A degradation was human plasma = rat blood > whole human blood >5% human serum albumin = washed human red blood cells (hematocrit 50%) = 5% pure hemoglobin. Presuming a solvent/gas partition coefficient of 0.31, respective approximate times for 50% degradation equaled 2.7, 2.8, 4.6, 9.9, 11.0, and 12 min. The accuracy of these approximations was limited by the need to estimate, rather than determine, the solubility of Compound A in such solvents. Pasteurization (heating to 60 degrees C for 12 h) or pretreatment with N-ethylmaleimide (a compound that reversibly binds to sulfhydryl groups) decreased the degradation rate in plasma. These results suggest that degradation arises, at least in part, from reaction of Compound A with proteins in blood, possibly from covalent reaction of Compound A with protein and/or from an enzymatically mediated reaction. The products of degradation, the binding sites, and the clinical implications of such binding and degradation remain to be determined.
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Affiliation(s)
- E I Eger
- Department of Anesthesia, University of California, San Francisco, 94143-0464, USA
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Matsushita M, Ohashi I, Becker GL, Pohorecki R. Isoflurane Preserves Adenosine Triphosphate Levels in Anoxic Isolated Rat Hepatocytes by Stimulating Glycolytic Adenosine Triphosphate Formation. Anesth Analg 1996. [DOI: 10.1213/00000539-199606000-00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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36
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Matsushita M, Ohashi I, Becker GL, Pohorecki R. Isoflurane preserves adenosine triphosphate levels in anoxic isolated rat hepatocytes by stimulating glycolytic adenosine triphosphate formation. Anesth Analg 1996; 82:1261-7. [PMID: 8638802 DOI: 10.1097/00000539-199606000-00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The hypothesis that general anesthetics protect energy reserves by decreasing energy demand is widely accepted but poorly substantiated. Isoflurane at clinical doses preserved adenosine triphosphate (ATP) levels in anoxic isolated hepatocytes. Specific inhibitors were used to block mitochondrial and/or glycolytic ATP formation to ascertain whether pathways of energy supply or demand, or both, were involved in ATP preservation by isoflurane. Hepatocytes were isolated from fed adult male rats after perfusing livers with Krebs buffer containing collagenase. Cells were incubated in Krebs buffer for 0-30 min at 25 degrees C under N2/CO2 (95%/5%) +/- isoflurane 0.63 mM in liquid phase. Oligomycin, iodoacetate, or fasting were used to block mitochondrial and glycolytic ATP formation. Under anoxia alone, ATP levels declined more slowly in the presence than in the absence of isoflurane, confirming the ATP-protective effect of isoflurane reported previously. With oligomycin plus iodoacetate blocking all ATP formation, ATP decline (representing pure ATP consumption) was not slowed by isoflurane. Isoflurane's protective effect recurred when glycolytic ATP supply was restored by incubating with oligomycin only. The protective effect was accompanied by increased lactate accumulation, and both effects-ATP preservation and lactate formation-were similarly dependent on isoflurane concentration. We conclude that the protective effect of isoflurane on energy status in anoxic isolated hepatocytes was not associated with reduced ATP demand but with enhanced ATP supply via stimulation of glycolysis.
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Affiliation(s)
- M Matsushita
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha 68198-4455, USA
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Pohorille A, Wilson MA. Excess chemical potential of small solutes across water--membrane and water--hexane interfaces. J Chem Phys 1996; 104:3760-73. [PMID: 11539401 DOI: 10.1063/1.471030] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The excess chemical potentials of five small, structurally related solutes, CH4, CH3F, CH2F2, CHF3, and CF4, across the water-glycerol 1-monooleate bilayer and water-hexane interfaces were calculated at 300, 310, and 340 K using the particle insertion method. The excess chemical potentials of nonpolar molecules (CH4 and CF4) decrease monotonically or nearly monotonically from water to a nonpolar phase. In contrast, for molecules that possess permanent dipole moments (CH3F, CH2F, and CHF3), the excess chemical potentials exhibit an interfacial minimum that arises from superposition of two monotonically and oppositely changing contributions: electrostatic and nonelectrostatic. The nonelectrostatic term, dominated by the reversible work of creating a cavity that accommodates the solute, decreases, whereas the electrostatic term increases across the interface from water to the membrane interior. In water, the dependence of this term on the dipole moment is accurately described by second order perturbation theory. To achieve the same accuracy at the interface, third order terms must also be included. In the interfacial region, the molecular structure of the solvent influences both the excess chemical potential and solute orientations. The excess chemical potential across the interface increases with temperature, but this effect is rather small. Our analysis indicates that a broad range of small, moderately polar molecules should be surface active at the water-membrane and water-oil interfaces. The biological and medical significance of this result, especially in relation to the mechanism of anesthetic action, is discussed.
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Affiliation(s)
- A Pohorille
- Department of Pharmaceutical Chemistry, University of California, San Francisco 94143, USA
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Kandel L, Chortkoff BS, Sonner J, Laster MJ, Eger E. I II. Nonanesthetics Can Suppress Learning. Anesth Analg 1996. [DOI: 10.1213/00000539-199602000-00019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
Nonanesthetic gases or vapors do not abolish movement in response to noxious stimuli despite partial pressures and affinities for lipids that would, according to the Meyer-Overton hypothesis, predict such abolition. We investigated whether nonanesthetics depress learning and memory (i.e., provide amnesia). To define learning, we used a "fear-potentiated startle paradigm": rats trained to associate light with a noxious stimulus (footshock) will startle more, as measured by an accelerometer, when a startle-eliciting stimulus (e.g., a noise) is paired with light than when the startle-eliciting stimulus is presented alone. We imposed light-shock pairings on 98 rats under three conditions: no anesthesia (control); 0.20, 0.29, and 0.38 times the minimum alveolar anesthetic concentration (MAC) of desflurane; or two nonanesthetics (1,2-dichloroperfluorocyclobutane and perfluoropentane) at partial pressures predicted from their lipid solubilities to be between 0.2 and 1 MAC. Desflurane produced a dose-related depression of learning with abolition of learning at 0.28 MAC. Perfluoropentane at 0.2-predicted MAC had the same effect as 0.28 MAC desflurane. 1,2-Dichloroperfluorocyclobutane at 0.5- to 1-predicted MAC abolished learning. Because nonanesthetics suppress learning but not movement (the two critical components of anesthesia), they may prove useful in discriminating between mechanisms and sites of action of anesthetics.
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Affiliation(s)
- L Kandel
- Department of Anesthesia, University of California, San Francisco 94143-0464, USA
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Ruzicka JA, Pedersen SD, Baker MT. Synthesis and toxicity of 1,2-bis(trifluoromethoxy)-1,1,3,3,-pentafluoropropane. J Fluor Chem 1996. [DOI: 10.1016/0022-1139(95)03374-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gonzales JM. Molecular Properties of the "Ideal" Inhaled Anesthetic. Anesth Analg 1995. [DOI: 10.1213/00000539-199504000-00038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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