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At least 19 recordsLinked to original sources
PubMedDate not supplied

A conformational model for the action of general anesthetics at the membrane level. II. Experimental observations on the effects of anesthetics on lipid fluidity and lipid protein interactions.

We have investigated the effect of general anesthetics (the normal alcohol series up to pentanol, halothane, pentrane, ether, chloroform, and ketamine) on lipid fluidity of phospholipid vesicles and mitochondrial and erythrocyte membranes by using spin labels and fluorescent probes. The spin labels used (5- and 16-doxyl stearic acids) show that all anesthetics tested have a slight fluidizing effect on lipid vesicles but induce a very strong increase in mobility of spin labels in mitochondria and lower in erythrocyte ghosts. These results are interpreted as a labilization of lipid protein interactions at all depths in the bilayer. The fluorescent molecules ANS and NPN, which probe the glycerol region and the core of the bilayer respectively, show a decrease of fluorescence induced by alcohols, halothane, ether, chloroform in both lipid vesicles and membranes. The decrease of fluorescence is due to decreased quantum yield as shown by double reciprocal plots of probe fluorescence against membrane concentration. The fluorescence decrease is interpreted mainly as an increase in fluidity of the lipid bilayer and not as an increase of polarity of the probe environment. The effect of ketamine is that of fluidization in the bilayer core (NPN) but of increased rigidity in the glycerol region (ANS) perhaps due to the amphipathic character of this anesthetic, that is supposed to bind in the polar region of the bilayer. Pentrane also induces fluidization in the bilayer core (NPN) but has a peculiar effect near the surface (ANS): in lipid vesicles it induces a fluorescence decrease, whereas an increase is seen in mitochondrial membranes. These complex effects are considered as the result of some specific change in the lipid protein interactions in the region probed by ANS. The effects of anesthetics on maximal NPN fluorescence (Fo) have been usually found to be stronger in mitochondrial membranes than in lipid vesicles, thus confirming the results of the spin label studies, showing a labilization of lipid protein interactions induced by anesthetics. The effects on Fo of ANS, however, appear to be stronger in lipid vesicles than in membranes. These findings indicate that the presence of the proteins counteracts the perturbation induced by anesthetics at the level of the membrane surface, in contrast with the disruption of lipid protein interactions observed in the membrane hydrophobic areas.

Anesthesia, General↗
PubMedDate not supplied

A conformational model of the action of general anesthetics at the membrane level. III. Anesthetics and the properties of membrane-bound enzymes: mitochondrial ATPase.

We have studied the effect of general anesthetics on the kinetic properties of the mitochondrial Mg2+-dependent ATPase. The enzyme is inhibited by anesthetics (alcohols, halotane, pentrane, ketamine) at concentrations of the order of those found to affect lipid-protein interactions. The inhibition appears usually uncompetitive with respect to the substrate, ATP, with a decrease of both Vmax and KM, indicating a possible stabilization of the enzyme-substrate complex. Arrhenius plots of ATPase activity show a striking increase in activation energy below 17-20 degrees C. Anesthetics affect the temperature dependence by increasing the activation energy above the break or abolishing the break whatsoever. An exception is diethyl ether, that induces a decrease in activation energy and a shift of the break to lower temperatures. Anesthetics make the ATPase insensitive to energy transfer inhibitor, oligomycin and dicyclohexyl carbodiimide. At low anesthetic concentration the oligomycin inhibition curve is changed from sigmoidal to hyperbolic, showing a loss of cooperativity in the inhibition.

Adenosine Triphosphatases↗
PubMed1976

The local anesthetic activity of saxitoxin alone and with vasoconstrictor and local anesthetic agents.

STX (saxitoxin), alone and with various vasoconstrictor and local anesthetic agents, was evaluated for its ability to produce topical anesthesia on the rabbit cornea, peripheral nerve block in the rat, and epidural anesthesia in the dog. High frequency and long duration of block can be attained if sufficiently high concentrations of STX are used, although latency is long and the doses used may produce systemic toxicity. Frequency of satisfactory blocks and mean duration of block can be increased and systemic toxicity reduced if STX is administered with a vasoconstrictor agent. Conventional local anesthetic agents also enhance the nerve blocking activity of STX. When appropriate concentrations of STX, vasoconstrictor and local anesthetic agents are used, systemic toxic effects are not manifested and the blocks produced exhibit the rapid onset and high frequency of block characteristic of the local anesthetic agent and the remarkably long duration of STX.

Anesthesia, Epidural↗
PubMedDate not supplied

The local anesthetic activity of tetrodotoxin alone and in combination with vasoconstrictors and local anesthetics.

Tetrodotoxin (TTX), alone and in combination with various vasoconstrictors and local anesthetics, was evaluated for its ability to produce peripheral nerve blocks in the rat and central neural blocks in the cat and dog. High frequency and long duration of block can be attained if sufficiently high concentrations of TTX are used, although latency is long and high dosage may produce systemic toxicity. Frequency and mean duration of block can be increased and systemic toxicity reduced if TTX is administered with a vasoconstrictive agent. Conventional local anesthetics also enhance the nerve-blocking activity of TTX. When appropriate concentrations of TTX and local anesthetics are used, a high frequency of blocks characterized by short latency and long duration can be demonstrated. The studies present some indirect evidence that local anesthetics enhance TTX activity by reversibly increasing the permeability of various neural barriers to TTX.

Anesthesia, Epidural↗
PubMed1978

Pulmonary and systemic hemodynamic effects of delta9-tetrahydrocannabinol in conscious and morphine--chloralose-anesthetized dogs: anesthetic influence on drug action.

Pulmonary and systemic hemodynamic effects of delta 9-tetrahydrocannabinol (delta 9-THC) in conscious dogs and in those anesthetized with morphine (3 mg/kg, i.m.) plus alpha-chloralose (100 mg/kg i.v.) were evaluated in this study. A decrease in the heart rate, cardiac output (PBF) and a concomitant increase in the pulmonary arterial pressure (PAP), pulmonary vascular resistance (PVR) and right ventricular stroke work (RVSW) observed in conscious animals following the administration of delta 9-THC were qualitatively similar to the effects reported in dogs anesthetized with sodium pentobarbital; however, unlike in the pentobarbital group, hypotensive effects to THC were not evident in the consious animals. In contrast, the effect of delta 9-THC in morphine--chloralose dogs were different; in this group delta 9-THC administration resulted in increases in the heart rate the PBF, and significant reductions in PAR, PVR and RVSW. Further, a decrease in the arterial blood pressure noted following THC administration was closely associated with a reduction in the total peripheral resistance in the morphine--chloralose group. The results of this study indicated that the pulmonary effects of THC in dogs may be related to its actions on the heart rate and differ qualitatively as well as quantitatively depending on the anesthetic used.

Anesthetics↗
PubMed1975

[Relations between the physico-chemical properties, the chemical reactivity and the local anesthetic activity. 32. (Part 1): Binding capacity of a structural protein (wool) to local anesthetics].

1. The general part deals with the molecular structure of nerve membranes and different local-anesthetic substances as well as the various possibilities of local-anesthetic binding to the nerve membrane. Albumin is usually chosen as a model protein in such investigations, a short extract of which is given. 2. The special part includes the chemical composition and properties of wool macroprotein, the model system used in the present paper. We determined its protein-binding values with cinchocain and tetracain homologues and various known commercial products of local anesthetics (oxybuprocain, parethoxyprocain and tetracain). The binding constants of these substances on wool protein are shown. 3. A statistically confirmed relationship between the alkyl chain length and the strength of protein binding is given. The free energy per CH2-group ranges between 400 and 500 cal/mol and its larger in cases of low pH values. 4. From the present data, a relationship between the binding constant and the partition constant of each substance of the homologous series studied could easily be observed, which further makes it possible to estimate the characteristic protein-binding constant Kp and also the change in pi-values with the change in free reaction energy of the substances. 5. The large differences in the binding values of the different binding mechanisms, which most probably are dependent on the variable binding affinities of the functional groups as well as on steric factors. But as in the homologous series, only substituents like alkyl amino and alkoxy could be changed, the possibility of some other binding process depending on the alkyl chain length of these groups could not be ruled out. Since the alky groups are non-polar, hydrophobic binding plays a role.

Albumins↗
PubMed1975

[Relations between the physico-chemical properties, the chemical reactivity and the local-anesthetic activity/part 33: studies on the interactions of local-anesthetically active cinchocaine homologues with phospholipids (author's transl)].

The general part consists of a review on nerve stimulus mechanism as well as the nerve structure and the function of nerve membrane as the site of action of local anesthetics. Furthermore a possibility of interaction between local anesthetics and the membrane components especially phospholipids is discussed. These phospholipids show interesting properties with respect to ions as well as local-anesthetics, which allow us to suppose that they are important participants in nervous stimulus transmission. In the experimental part two methods are described. The first deals with the measurement of electrical resistance as function of time at cephalin and cholesterin impregnated filter membrane in solutions of cinchocain homologues. An increase in the resistance with the increase in concentration of test substances was observed. The same was the effect of increasing chain length in alkoxy group where after butoxy derivative, a deformation of membrane was observed. In the second method the drug binding capacity of cephalin dispersed in aqueous medium was measured. Here, too, the increase in the binding capacity with the increase in alkoxy chain was observed. The large difference in free binding energy between two subsequent homologues is explained as the effect of increase in van der Waals' forces and hydrophobic interactions on one hand, and a change in colloidal form of cephalin dispersion on the other hand.

Absorption↗
PubMed1976

Study of local anesthetics. Part 46: Correlations between anesthetic activity and physico-chemical parameters of some alkoxy substituted esters of phenylcarbamic acids.

The partition in water-octanol and water-carbon tetrachloride systems and electronic spectra of three series of esters of phenylcarbamic acid and its m- and p-alkoxy derivatives were measured. The surface local anesthetic activity of these compounds as well as the infiltration anesthetic activity of some of them were correlated with combinations of partition coefficients, spectral parameters and sigma-coefficients.

Anesthetics, Local↗
PubMed1976

Cardiovascular effects of different anesthetics in man. Study of two volatile anesthetics: enflurane (ethrane), halothane (fluothane).

In the first part of this paper we report the effects of 4 short acting intravenous anesthetics (althesin, etomidate, epontol, brietal) on the cardiovascular effects due to ethrane. In the second part we learn with the same induction anesthetic (etomidate) the cardiovascular effects of ethrane and fluothane. We have proved that: 1 degree althesin least potentiates the variations in the cardiovascular parameters under the action of ethrane, 2 degrees halothane 2% decreases more the blood pressure than ethrane 1%.

Adolescent↗
PubMed1976

Cardiovascular effects of various anesthetics in man. Four short-acting intravenous anesthetics: althesin, etomidate, methohexital and propanidid.

Four groups of 15 patients without any cardiovascular or pulmonary pathology received an intravenous injection of one of the 4 studied anesthetics, Althesin (0.07 ml/kg), Methohexital (1.6 mg/kg), Etomidate 0.15 mg/kg) or Propanidid (6 mg/kg). Arterial pressure, heart rate, stroke volume and cardiac output were measured every thirty or sixty seconds. Stroke volume decreased and heart rate increased with all of them, but most of all with Propanidid. The only statistically significant reduction of cardiac output was observed with Althesin. Arterial pressures did not vary. Under the conditions of the present study and at the dose levels mentioned, Etomidate produced the least changes in cardiac parameters.

Adult↗
PubMed1977

[Reaction of local myocardial blood flow in non-anesthetized dogs and anesthetized cats to the oral and parenteral administration of a Crateagus fraction (oligomere procyanidines)].

Local blood flow in the myocardium of the left ventricle in unanesthetized dogs was measured by chronically implanted heat-conduction probes. Oral administration of a fraction of Crataegus (oligomere procyanidines) led to a significant rise in blood flow for several hours depending on the dose, the highest increase reaching an average value of about + 70% of the resting flow. In dogs regularly fed with this substance for a longer period of time, a rising tendency of the matutinal resting values of myocardial blood flow towards a maximum was seen. Intravenous application of oligomere procyanidines in anesthetized cats led to a dose-dependent increase in myocardial blood flow for several minutes and a slight decrease in arterial blood pressure.

Administration, Oral↗
PubMed2026

Adductor Canal Block and Local Anesthetic Versus Local Anesthetic Alone in ACL Reconstruction: A Double-Blind Randomized Controlled Trial.

BACKGROUND: Effective postoperative analgesia is crucial for early recovery after anterior cruciate ligament reconstruction (ACLR). Local infiltration analgesia (LIA) and adductor canal block (ACB) are common regional techniques, but their combined efficacy remains unclear. PURPOSE: To compare the effectiveness of LIA alone versus LIA combined with ACB in patients undergoing ACLR, with primary outcomes including postoperative opioid consumption and quadriceps function. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A double-blind randomized controlled trial enrolled 100 patients undergoing ACLR under general anesthesia. Patients were randomized into 2 groups: LIA + sham (saline injection) (n = 50) and LIA + ACB (n = 50). The primary outcome was postoperative opioid consumption in the first 24 hours. Secondary outcomes included visual analog scale (VAS) pain score, quadriceps function assessed by straight leg raise (SLR) at 3 hours, Quality of Recovery-15 (QoR-15) score, and Knee Injury and Osteoarthritis Outcome Score (KOOS) at 1 week. Statistical analysis was performed using t tests and chi-square tests with a P value <.05 considered significant. RESULTS: There was no significant difference in 24-hour opioid consumption between the LIA + ACB and LIA-only groups (P = .109). Similarly, VAS pain scores at 24 hours postoperatively showed no significant differences between the groups (P = .0804). Early functional recovery, assessed by SLR performance at 3 hours, was equivalent between groups (P = .6711). Additionally, QoR-15 scores on postoperative day 1 and KOOS values at 1 week demonstrated no significant differences (P = .6486 and P = .9054, respectively). Intraoperative opioid consumption was not different between the groups (P = .127). CONCLUSION: These findings indicate that the addition of ACB to LIA does not yield postoperative analgesic in ACLR. Consequently, LIA alone suffices for routine ACLR, potentially enabling clinicians to optimize perioperative workflows without incurring the additional time, financial burden, and resources associated with routine ACB administration. TRIAL REGISTRATION: ClinicalTrials.gov; NCT04721119.

Humans↗
PubMed1992

[Local anesthetics. CVII. Local anesthetic effects of phenylcarbamates--the effect of connecting chain modification].

The preceding study of the effect of the branching of the connecting chain by the metoxymethyl-, ethoxymethyl- and propoxymethyl group on the alpha carbon on local anaesthetic activity was a stimulus for the preparation of 16 drugs of the group of 1-ethoxyethoxymethyl-2-(1-pyrrolidinyl-), 2-piperidino- and 2-(1-perhydroazepinyl) ethyl esters of o-, m- and p-alkoxyphenylcarbamic acids. The discontinuation of the substituent on the alpha carbon of the connecting chain by another oxygen atom (introduction of an ethoxyethoxymethyl group) has a positive effect on surface and infiltration anaesthesia. Of the prepared agents, 2-piperidino- and 2-(1-perhydroazepinyl-) derivatives with a hexyl or heptyloxy group in the o-position of the benzene ring were most effective; they exceeded the standards cocaine and procaine more than one hundred times. p-Derivatives were least effective; in some cases their indices of effectiveness did not achieve the effectiveness of the standards in both surface and infiltration anaesthesia under study. Acute toxicity of all drugs lies within the range of the toxicities of the standards.

Anesthetics, Local↗