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Anesthesiology Feb 1993Volatile anesthetics exert both direct and indirect (neurally mediated) effects to produce splanchnic venodilation. These effects may result in clinically relevant...
BACKGROUND
Volatile anesthetics exert both direct and indirect (neurally mediated) effects to produce splanchnic venodilation. These effects may result in clinically relevant hemodynamic changes. The present study examined the direct effects of isoflurane, halothane, and enflurane on rabbit mesenteric venous smooth muscle.
METHODS
Changes in isometric tension, in response to exogenous and endogenous norepinephrine, were measured in isolated mesenteric vein rings before and during the administration of volatile anesthetics.
RESULTS
Exogenous and electrically evoked endogenous norepinephrine produced an increase in tension with super-imposed rhythmic oscillations in tension. The exogenous norepinephrine-induced increase in tension was augmented in the presence of NG-nitro-L-arginine methyl ester (L-NAME, 5 x 10(-5) M). The oscillatory activity was not altered by L-NAME. The increase in isometric tension in response to electrical stimulation was inhibited by phentolamine (5 x 10(-6) M) and tetrodotoxin (3 x 10(-6) M). Equianesthetic (1 MAC) concentrations of isoflurane, halothane, and enflurane significantly attenuated contractile responses to exogenous and endogenous norepinephrine, with isoflurane demonstrating a more depressant effect than halothane or enflurane. Volatile anesthetics also suppressed the amplitude and frequency of oscillations in the control as well as L-NAME-treated veins. The inhibitory effects of volatile anesthetics on the oscillations were comparable to the effects of ryanodine, a specific blocker of calcium channels in sarcoplasmic reticulum.
CONCLUSIONS
These results suggest that: 1) vascular endothelium, via endothelium-derived relaxing factor, modulates exogenous norepinephrine responses of the venous smooth muscle; 2) the oscillatory behavior of mesenteric veins may be attributed to calcium fluxes in the venous smooth muscle cells; and 3) the norepinephrine-dependent increases in contractile and oscillatory activity are attenuated more by isoflurane than halothane or enflurane. This indicates that volatile anesthetic-mediated splanchnic venodilation is, at least in part, due to a direct action on vascular smooth muscle as well as withdrawal of sympathetic tone.
Topics: Animals; Enflurane; Halothane; In Vitro Techniques; Isoflurane; Male; Mesenteric Veins; Muscle, Smooth, Vascular; Norepinephrine; Rabbits
PubMed: 8439028
DOI: 10.1097/00000542-199302000-00017 -
British Journal of Anaesthesia Apr 1989The superficial and deep body temperatures of 40 healthy females undergoing total abdominal hysterectomy were measured during surgery and for 4 h afterwards. The... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
The superficial and deep body temperatures of 40 healthy females undergoing total abdominal hysterectomy were measured during surgery and for 4 h afterwards. The patients were allocated randomly to one of five groups and anaesthetized to produce an end-tidal concentration of 1% halothane, 1% enflurane, 2% enflurane, 1% isoflurane or 2% isoflurane. The patients received also 70% nitrous oxide in oxygen and neuromuscular blockade. The theatre temperature was maintained at 22.0 degrees C. There were significant body temperature changes during operation in all groups. The mean (SD) decrease in core temperature over 85 min was approximately 1.1 (0.3) degrees C in the 1% halothane, 2% enflurane and 2% isoflurane groups, and 0.6 (0.4) degrees C in the 1% enflurane and 1% isoflurane groups (P less than 0.05). During the recovery period the 1% halothane, 2% enflurane and 2% isoflurane groups took 2 h to rewarm to preoperative temperatures, and the rate of rewarming during this time was similar for all groups.
Topics: Adult; Aged; Anesthesia Recovery Period; Body Temperature; Enflurane; Female; Halothane; Humans; Hysterectomy; Intraoperative Period; Isoflurane; Middle Aged; Postoperative Period
PubMed: 2706176
DOI: 10.1093/bja/62.4.409 -
Anesthesiology Jun 1992EDRF (endothelium-derived relaxing factor) is a cellular and intercellular messenger that activates soluble guanylate cyclase. In blood vessels it is released from the...
EDRF (endothelium-derived relaxing factor) is a cellular and intercellular messenger that activates soluble guanylate cyclase. In blood vessels it is released from the endothelium and causes relaxation of vascular smooth muscle. Halothane previously has been shown to attenuate EDRF-induced vasodilation elicited by the receptor-mediated vasodilators acetylcholine and bradykinin and to alter muscarinic receptor activity. We examined and compared the effects of the inhaled anesthetics halothane, enflurane, and isoflurane on endothelium-dependent vasodilation and tested the hypothesis that these agents inhibit EDRF-mediated vasodilation solely through inhibition of endothelial cell receptor-mediated EDRF release. Isolated rat thoracic aortic rings were mounted for isometric tension recording and preconstricted with phenylephrine. Cumulative dose-response curves were obtained to methacholine, a receptor-mediated endothelium-dependent dilator; to A23187, a nonreceptor-mediated endothelium-dependent dilator; and to sodium nitroprusside, a direct-acting endothelium-independent dilator before, during, and after inhalational anesthetic exposure. Both receptor-mediated and non-receptor-mediated endothelium-dependent relaxation by methacholine and A23187, respectively, were significantly (P less than 0.01 to P less than 0.05) and reversibly attenuated by halothane, enflurane, and isoflurane at 2 MAC and by isoflurane at 1 MAC. Endothelium-independent relaxation by sodium nitroprusside, an agent that acts directly on the vascular smooth muscle cell to activate guanylate cyclase, was unaffected by any of the anesthetics at any concentration tested. Indomethacin had no significant effect on the inhibition of endothelium-dependent vasodilation by these inhalational anesthetics. We conclude that halothane, enflurane, and isoflurane inhibit endothelium-dependent vasodilation; that isoflurane is more potent than halothane and enflurane in this regard.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Aorta, Thoracic; Calcimycin; Depression, Chemical; Enflurane; Halothane; In Vitro Techniques; Isoflurane; Male; Methacholine Chloride; Nitric Oxide; Nitroprusside; Rats; Rats, Inbred Strains
PubMed: 1599087
DOI: 10.1097/00000542-199206000-00023 -
British Journal of Pharmacology Oct 19921. The effects of two general anaesthetics, propofol and enflurane, on electrical activity and contractions were investigated in single myocytes isolated from guinea-pig...
1. The effects of two general anaesthetics, propofol and enflurane, on electrical activity and contractions were investigated in single myocytes isolated from guinea-pig ventricles. 2. Propofol and enflurane depressed the plateau and shortened the duration of action potentials. 3. Under voltage-clamp conditions, propofol and enflurane reduced the amplitude of inward calcium current and of additional inward current activated by cytosolic calcium. 4. Contractions (measured with an optical technique) accompanying either action potentials or second inward currents (in response to depolarizations to 0 mV) were reduced by both anaesthetics. The mechanisms for calcium entry during contractions accompanying pulses to positive potentials such as +60 mV are thought to differ from those accompanying second inward currents which are evoked by pulses from -40 to 0 mV. Enflurane enhanced the amplitudes of contractions accompanying pulses to positive potentials; in contrast these contractions were depressed by propofol. 5. In experiments where recovery processes were investigated by use of pairs of voltage-clamp pulses with a variable interval between them, enflurane but not propofol slowed the recovery of contractions and calcium-activated 'tail' currents. These observations are consistent with the hypothesis that enflurane may impair calcium handling by the sarcoplasmic reticulum whereas propofol has little, if any, effect at this site. 6. In conclusion, the actions of propofol and enflurane on second inward currents contribute to their effects on action potentials and contraction. The negative inotropic effect of both anaesthetics may result partly from reduced calcium influx to trigger contraction, and for enflurane, partly from an impairment of calcium handling by the sarcoplasmic reticulum.
Topics: Animals; Calcium; Calcium Channels; Enflurane; Guinea Pigs; Heart Ventricles; In Vitro Techniques; Membrane Potentials; Myocardial Contraction; Myocardium; Propofol
PubMed: 1330186
DOI: 10.1111/j.1476-5381.1992.tb12783.x -
Anesthesiology Jul 1990The effects of ketamine, halothane, enflurane, and isoflurane on systemic and splanchnic hemodynamics in cirrhotic rats that were either normovolemic or hypovolemic... (Comparative Study)
Comparative Study
The effects of ketamine, halothane, enflurane, and isoflurane on systemic and splanchnic hemodynamics in cirrhotic rats that were either normovolemic or hypovolemic following hemorrhage were characterized. Rats received at random either ketamine (30 mg/kg iv, 1.5 mg.kg-1.min-1 iv), halothane, enflurane, or isoflurane (1 MAC). Conscious rats were considered the control group. Four weeks before hemodynamic studies bile duct ligation was performed in all rats to induce cirrhosis. Hemodynamic measurements were performed using the radioactive microsphere method 1 h after the onset of anesthesia and 30 min after hemorrhage. Anesthetized rat lungs were mechanically ventilated with room air. Before hemorrhage cardiac index was higher in conscious rats and in rats receiving isoflurane than in the other groups (P less than 0.001). Hepatic arterial blood flow was similar in conscious rats and in those receiving isoflurane or halothane and was higher than in those receiving ketamine or enflurane. The lowest splanchnic and portal venous tributary blood flows were observed in rats receiving enflurane. After hemorrhage cardiac index was significantly less than before hemorrhage in all groups, except in rats receiving enflurane. After hemorrhage portal venous tributary blood flow decreased significantly in all groups except in enflurane group. During halothane and enflurane anesthesia hepatic arterial blood flow and hepatic arterial fraction of cardiac output decreased (P less than 0.01) and they were maintained in the other groups. After hemorrhage hepatic arterial fraction of cardiac output in conscious rats was higher than in those receiving ketamine, halothane, or enflurane (P less than 0.05) and was similar to those receiving isoflurane.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Enflurane; Halothane; Hemodynamics; Infusions, Intravenous; Isoflurane; Ketamine; Liver Circulation; Liver Cirrhosis, Experimental; Male; Microspheres; Rats; Rats, Inbred Strains; Shock; Splanchnic Circulation
PubMed: 2360721
DOI: 10.1097/00000542-199007000-00017 -
Medycyna Pracy Feb 2022The aim of this work is to analyze the health hazards of enflurane exposure and to analyze the occupational exposure limits (OEL). The method of obtaining evidence based... (Review)
Review
The aim of this work is to analyze the health hazards of enflurane exposure and to analyze the occupational exposure limits (OEL). The method of obtaining evidence based on a review of online databases of scientific journals was used. Enflurane is an inhalation anesthetic. Malignant hyperthermia, seizures, arrhythmias, respiratory depression and hypotension have been observed in patients. Occupational exposure to enflurane may occur in healthcare professionals. The target organ for enflurane is the central nervous system with a critical consequence of deterioration in psychomotor performance. In studies on volunteers recruited from the medical staff of operating rooms exposed to enflurane, a significant deterioration in the results of the Simple Reaction Time Test was shown. World experts' groups assume that the LOAEC (lowest observed adverse effect concentration) value for the deterioration of psychomotor test results is 5-10% of the MAC value (minimal anesthetic concentration), i.e., 6342-12 684 mg/m3. Assessment of the nephrotoxic potential of enflurane has shown that it is unlikely to occur because biotransformation of enflurane in humans results in a low peak serum fluoride concentration of 15 μmol/l. Early reports about liver damage in patients were not be supported. Occupational exposure epidemiological studies have raised concerns about the effects of anesthetic gas mixtures on the abortion rate or on fetal development and birth defects in children, but none of these studies specifically determined the type and concentration of anesthetic gases used. The carcinogenicity and mutagenicity studies were negative. Occupational exposure to enflurane is not monitored in Poland, as no standard value has been established for it in the air of the working environment. It is necessary to quickly introduce this anesthetic along with the applicable limit value to the OEL list. Med Pr. 2022;73(1):51-69.
Topics: Anesthetics, Inhalation; Child; Enflurane; Fluorides; Humans; Occupational Exposure; Operating Rooms
PubMed: 35129537
DOI: 10.13075/mp.5893.01204 -
British Medical Journal May 1980
Topics: Anesthesia, General; Chemical and Drug Induced Liver Injury; Enflurane; Enzyme Induction; Halothane; Humans; Liver
PubMed: 7388468
DOI: No ID Found -
Anesthesiology Oct 1996Minimum alveolar concentration (MAC) of isoflurane is decreased in early pregnancy but it is not known whether this occurs to the same extent with other inhalational... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
BACKGROUND
Minimum alveolar concentration (MAC) of isoflurane is decreased in early pregnancy but it is not known whether this occurs to the same extent with other inhalational anesthetics. The MAC of halothane and enflurane were compared in pregnant women undergoing elective termination of pregnancy and in nonpregnant women.
METHODS
We studied 16 pregnant women scheduled for termination of pregnancy at 8 to 13 weeks gestation and 16 non-pregnant patients undergoing laparoscopic sterilization. Eight patients in each group received halothane and the others received enflurane. After inhalational induction of anesthesia and tracheal intubation, MAC was determined in each patient by observing the motor response to a 10-s, 50-Hz, 80-mA transcutaneous electric tetanic stimulus to the ulnar nerve at varying concentrations of either halothane or enflurane. The end-tidal concentration of inhalational anesthetic was kept constant for at least 15 min before each stimulus and the concentration was varied ultimately in steps of 0.05 vol% (halothane) or 0.10 vol% (enflurane) until a sequence of three alternate responses (move, not move, move) or (not move, move, not move) was obtained. Minimum alveolar concentration for each person was taken as the mean of the two concentrations just permitting and just preventing movement, and MAC for the group was the median of individual MAC values. Confidence intervals were calculated for the percentage decrease in MAC for pregnant women compared with nonpregnant women.
RESULTS
The median (range) MAC of halothane, 0.58 vol% (0.53 to 0.58), and enflurane, 1.15 vol% (0.95-1.25), in the pregnant women were less than those in the nonpregnant women, 0.75 vol% (0.70 to 0.78), P = 0.0005 and 1.65 vol% (1.45 to 1.75), P = 0.0007, respectively. The percentage decrease (95% CI) in MAC for pregnant women was 27% (20 to 27%) for halothane and 30% (24 to 36%) for enflurane.
CONCLUSIONS
The MAC of halothane and enflurane were reduced by a similar degree in pregnant women at 8 to 13 weeks gestation compared with nonpregnant women.
Topics: Adolescent; Adult; Anesthetics, Inhalation; Electric Stimulation; Enflurane; Female; Halothane; Humans; Motor Neurons; Pregnancy; Pulmonary Alveoli; Single-Blind Method
PubMed: 8873548
DOI: 10.1097/00000542-199610000-00013 -
British Journal of Anaesthesia Dec 1978Plasma concentrations of thiopentone following the injection of 3.5 mg kg-1 i.v. were studied in six patients who received enflurane and nitrous oxide anaesthesia and...
Plasma concentrations of thiopentone following the injection of 3.5 mg kg-1 i.v. were studied in six patients who received enflurane and nitrous oxide anaesthesia and six volunteers. We identified a three-compartment open model system containing both a "shallow" and a "deep" peripheral compartment in all the patients and half of the controls, and a two-compartment open model for the remaining volunteers. The distribution of thiopentone to the tissues was very rapid, the alpha and beta distribution half-lives averaging 2.5 min and 46.4 min respectively for the patient group and 2.8 min and 48.7 min for the control group. The wide distribution of the drug was indicated by the apparent volume of distribution, the means of which varied between 2 and 1.5 times body weight. The mean elimination half-life was 5.1 h for the patients and 5.7 h for the volunteers. The return of the drug to the central compartment from the deep peripheral compartment was the rate-controlling factor in its elimination. Neither enflurane and nitrous oxide anaesthesia nor the stress of surgery affected the distribution or clearance of the drug from plasma.
Topics: Adult; Anesthesia, General; Enflurane; Female; Half-Life; Humans; Male; Methyl Ethers; Nitrous Oxide; Surgical Procedures, Operative; Thiopental; Time Factors
PubMed: 747695
DOI: 10.1093/bja/50.12.1237 -
Anesthesiology Jun 1991The authors examined the direct myocardial and coronary vascular responses to isoflurane, enflurane, and halothane and compared their effects on attenuating... (Comparative Study)
Comparative Study
The authors examined the direct myocardial and coronary vascular responses to isoflurane, enflurane, and halothane and compared their effects on attenuating autoregulation of coronary flow (CF) as assessed by changes in the O2 supply-demand relationship. The effects of these anesthetics on left ventricular pressure (LVP), CF, percentage of O2 extraction, O2 delivery (DO2), and myocardial O2 consumption (MVO2) were examined in 47 isolated guinea pig hearts perfused at constant pressure. An increase in DO2 from control relative to MVO2 was used to indicate attenuation of autoregulation, and a decrease in MVO2 relative to DO2 to indicate a reduction of myocardial work and O2 utilization. Each heart was exposed to 0.51, 0.70, and 1.20 vol% halothane (n = 16); 0.91, 1.41, and 2.04 vol% enflurane (n = 16); or 0.45, 0.87, and 1.22 vol% isoflurane (n = 15). Adenosine (2 mM) was given to test maximal CF in arrested and in paced hearts. Mean results for increasing concentrations of each agent were as follows: LVP (average control 92 +/- 5 mmHg) (standard error of mean [SEM]) decreased by 15%,* 25%,* and 34%* with halothane; 13%,* 24%,* and 34%* with enflurane; and only 3%, 7%, and 13%* with isoflurane (*P less than 0.05 vs. controls). CF (control 6.1 +/- 0.3 ml.min-1.g-1) was not altered significantly with halothane or enflurane but increased by 6%, 9%, and 16%* with isoflurane and maximally by 86 +/- 7%* with adenosine. The percentage of O2 extraction (control 69.2 +/- 1.8%) decreased by 9%,* 16%,* and 22%* with halothane; 7%,* 15%,* and 22%* with enflurane; and only 1%, 4%, and 7%* with isoflurane.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Enflurane; Guinea Pigs; Halothane; Heart; In Vitro Techniques; Isoflurane; Oxygen Consumption
PubMed: 2042761
DOI: 10.1097/00000542-199106000-00017