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PubMed1998

[Histamine plasma concentration and cardiovascular effects of non-depolarizing muscle relaxants: comparison of atracurium, vecuronium, pancuronium and pipecuronium in coronary surgical patients at risk].

OBJECTIVE: Cardiovascular effects of four commonly used non-depolarising muscle relaxants and their ability to increase histamine plasma concentrations were studied in patients scheduled for coronary artery bypass grafting. METHODS: 40 patients were included in the study after informed consent. After premedication with Flunitrazepam (2 mg p.o.) on the evening before and 1 hour prior to surgery anaesthesia was induced with Flunitrazepam (4-6 micrograms kg-1). Fentanyl (3 micrograms kg-1) und Etomidate (150 micrograms kg-1) and the patients were ventilated via face mask with 50% N2O in oxygen. Patients were randomly allocated to one of four groups, and, 15 min after induction of anaesthesia, received equipotent doses of either Pancuronium (0.09 mg kg-1, n = 10). Pipecuronium (0.08 mg kg-1, n = 10), Atracurium (0.6 mg kg-1, n = 10), or Vecuronium (0.1 mg kg-1, n = 10) injected over 20 seconds via a central venous catheter. Cardiovascular variables were determined in the awake patient, 15 min after induction of anaesthesia and following administration of the respective muscle relaxant. In addition, plasma histamine concentrations were assessed before and after relaxation. Evoked muscular response to TOF simulation of the ulnar nerve (plethysmo-mechanogram) was continuously recorded to determine the onset of neuromuscular blockade. RESULTS: Heart rate, mean arterial pressure and cardiac index significantly decreased in all patients following induction of anaesthesia while systemic vascular resistance remained unchanged. Only Pancuronium caused a significant increase in heart rate (53 +/- 11 to 61 +/- 15 min-1) whereas cardiac index and mean arterial pressure did not change significantly. No other neuromuscular blocking agent caused any changes in the cardiovascular variables measured and histamine plasma concentrations remained within the reference range in all of the four groups with no differences detectable between groups. CONCLUSIONS: All investigated neuromuscular blocking agents exhibited marked cardiovascular stability which permits their use, being based exclusively on pharmacodynamic and pharmakokinetic considerations even in patients with coronary heart disease. If an increase in heart rate appears beneficial Pancuronium may be advantageous.

Anesthesia↗
PubMed1990

[A pharmacodynamic analysis of the onset of neuromuscular blockade by nondepolarizing muscle relaxants--the pharmacodynamics of a large dose of vecuronium].

From Sheiner's equation on pharmacokinetics and pharmacodynamics, we derived a new equation which described the pharmacodynamics of nondepolarizing muscle relaxants during the onset phase. This equation showed that log (l0/l-1) had a linear relation to log (t) where "t" is the time after the administration of nondepolarizing muscle relaxant and "l" and "l0" are the twitch height at t = t and t = 0 respectively. It also implies that the administration dose (D) is inversely proportional to the onset time (OT), i.e., D.OT = const. We proved that these two relations held well for the actual 7 cases of vecuronium use in man. In conclusion, when vecuronium dose level was within 0.15-0.30 mg.kg-1 i.v., the dose was inversely proportional to the onset time which was defined as the time interval from the end of the administration of vecuronium until the single twitch was depressed under 5% of control value, i.e., Dose (mg.kg-1) x onset-time (sec) not equal to 24. During anesthesia with enflurane as well as during neuroleptanesthesia, a dose of vecuronium 0.3 mg.kg-1 (n = 7) was found to produce a duration of neuromuscular blocking action equal to the mean duration produced by pancuronium 0.1 mg.kg-1.

Adult↗
PubMed1986

Tracheal epithelium releases a vascular smooth muscle relaxant factor: demonstration by bioassay.

Acetylcholine caused no relaxation of a rubbed strip from rabbit aorta (RASR) which was precontracted with phenylephrine. When the same strip was taken into epithelium-intact guinea-pig trachea, acetylcholine produced a slow-developing relaxation which was antagonized by atropine but not by propranolol, indomethacin, theophylline or hydroquinone. RASR was not relaxed by acetylcholine when it was taken from epithelium-rubbed trachea. The results indicate that acetylcholine releases vascular smooth muscle relaxant factor from tracheal epithelium.

Acetylcholine↗
PubMed2002

Muscular mass assessed by ultrasonography after administration of low-dose corticosteroids and muscle relaxants in critically ill hemiplegic patients.

BACKGROUND AIMS: The present study investigates the influence of low-dose and short- term administration of corticosteroids and muscle relaxants on the muscular mass (MM) in hemiplegic ICU patients, with the aid of ultrasonography (U/S). METHODS: Thirty-seven patients hospitalised in the ICU for 18.6+/-3.6 days, were included in the study. Sixteen patients did not receive either drug (group A), five patients received dexamethasone (24 mg/day) for 4 days (group B), eight patients received dexamethasone (24 mg/day) for 4 days and atracurium (0.3-0.6 mg/kg/h) for 2.8+/-0.4 days (group C), whereas eight other non-hemiplegic ICU patients comprised the control group. MM was measured in cm by U/S and serum Albumin (ALB, g/l) at the first and the tenth ICU hospitalisation day. The corresponding differences (DeltaMM, DeltaALB) were compared between the four groups of patients. RESULTS: MM and ALB decreased significantly in all groups. DeltaMM was significantly higher in group C in comparison to all other groups, while DeltaMM was also higher in group B, when compared to the control and A groups. DeltaALB did not show significant inter-group differences. DeltaMM was significantly related to patients' age (r=0.41,P =0.001). CONCLUSIONS: Muscular atrophy of the ICU hemiplegic patients is significantly influenced by the synchronous treatment with muscle relaxants and corticosteroids at low doses and for short term. This myopathy should be taken into account for the better prognosis and the safer outcome of the patient and U/S is suitable for accurate and non-invasive monitoring of MM.

APACHE↗
PubMed1983

Octylonium bromide: a smooth muscle relaxant which interferes with calcium ions mobilization.

A series of "in vitro" experiments have been carried out to determine the mechanisms(s) responsible for the smooth muscle relaxant properties exhibited by octylonium bromide. Unlike N-butyl-scopolammonium bromide, octylonium bromide possesses both competitive and non competitive antimuscarinic and antihistaminic properties. Pretreatment of ileal segments with dibenamie, which destroyed muscarinic spare receptors, revealed the non competitive nature of octylonium bromide antagonism. The competitive antagonism toward BaCl2-induced contraction of rat ileum and aorta suggested that octylonium bromide interferes with Ca++ mobilization. As compared with verapamil a known Ca++ entry blocker and unlike it, octylonium bromide is more effective in antagonizing Ca++-induced contraction in K+ depolarized rat colon than aorta. Both octylonium bromide and verapamil reduced in a concentration-dependent manner the tonic contraction produced by exposure to high K+ of rat duodenum and rabbit ear artery. Both octylonium bromide and verapamil antagonized carbachol-induced phasic plus sustained tonic contraction of rat colon in high K+ Ca++-free medium. Unlike octylonium bromide, verapamil antagonized the phasic contraction only and inhibition of the overall contraction did not exceed 60%. Unlike verapamil, octylonium bromide antagonized norepinephrine-induced contraction of rabbit ear artery in high K+ C++-free medium. Interference with mobilization of cellular and extracellular Ca++ pools produced by different neurohormones is likely to be the mechanism responsible for octylonium bromide smooth muscle relaxant properties in both animals and humans.

Animals↗
PubMed1994

Muscarinic stimulation of arachidonic acid release and prostaglandin synthesis in bovine ciliary muscle: prostaglandins induce cyclic AMP formation and muscle relaxation.

In the present study it is demonstrated that in bovine ciliary muscle, muscarinic stimulation results in: (a) release of 14C-arachidonic acid (14C-AA) and 14C-labeled prostaglandins (PGs) from muscle prelabeled with 14C-AA; (b) release of endogenous PGs, measured by means of radioimmunoassay; (c) enhanced IP3 production and (d) muscle contraction. In addition, PGs, such as PGE2 and PGD2, increased cAMP formation and induced muscle relaxation. The studies on the kinetics of 14C-AA metabolism revealed that incorporation of 14C-AA into glycerolipids and its conversion into PGs by the ciliary muscle were rapid and time-dependent. The amounts of 14C-radioactivity recovered in the major PGs decreased in the following order: PGD2 > PGE2 < PGF2 alpha > 6-keto-PGF1 alpha. The rate of endogenous PGF2 alpha synthesis by iris-ciliary body tissues from different mammalian species was found to be in the following order: ciliary muscle < ciliary processes < sphincter muscle. The EC50s for muscarinic-stimulated release of 14C-AA, 14C-labeled PGs, and endogenous PGF2 alpha and PGE2, and for IP3 production and contraction of the ciliary muscle indicate that CCh is 2-16 times as potent as pilocarpine in eliciting these responses, with the greatest difference being for contraction. The maximal increase in ciliary muscle tension due to CCh was 48% greater than that evoked by pilocarpine. All PGs tested, including PGE2, 17-phenyl trinor PGE2, 11-deoxy PGE1, PGF2 alpha and PGD2 had no effect on IP3 production and contraction in the ciliary muscle. However, PGE2 and PGD2 stimulated cAMP formation and inhibited CCh-induced IP3 production in a dose-dependent manner. In addition, PGE2 and PGD2 induced relaxation in ciliary muscle precontracted by CCh. In presence of indomethacin (1 microM), the CCh-induced contraction was greater than that observed in absence of the cyclo-oxygenase inhibitor. It is suggested that in the ciliary muscle certain PGs, such as PGE2 and PGD2, may function to modulate, via cAMP, the responses to muscarinic stimulation in this tissue.

Animals↗
PubMed1987

Comparison of cutaneous and in vitro histamine release by muscle relaxants.

The authors compared histamine release in vitro in a human neonatal foreskin preparation to histamine release in vivo in adult humans with three commonly used muscle relaxants (vecuronium, atracurium, and d-tubocurarine) in concentrations ranging from 10(-1) M to 3 X 10(-3) M. They measured histamine release directly in the in vitro preparation and measured the wheal size resulting from intradermal injection in vivo. Both in vivo and in vitro testing revealed dose-related histamine release with d-tubocurarine and atracurium (P less than .05). Vecuronium did not release histamine at any concentration. It was concluded that the infant foreskin model is a valid predictor of histamine release by muscle relaxants in vivo, and can provide valuable information about mechanisms of histamine release by these, and perhaps others, drugs used in anesthetic practice.

Adult↗
PubMed1988

A "give" in tension and sarcomere dynamics in cardiac muscle relaxation.

Isometric relaxation in cardiac sarcomeres is characterised by an early, very slow phase of tension fall which is terminated by a 'give' in tension. A 'give' which occurs during relaxation in cardiac muscle can not be attributed to decrease in myofilament overlap. After the 'give' asynchronous motion occurs between sarcomeres, but the duration and extent of their displacement is limited. Intriguingly, the effect of isotonic displacements on the early fall in the velocity of sarcomere shortening indicates that an internal resistance increases near the peak of contraction. The complex shape of the sarcomere's complete force-velocity relation, with lengthening motions in particular, was consistent with an idealized model of cross-bridge cycling. The sarcomere's resistance to stretch is high at low velocity, but it diminishes to reveal yielding at larger velocities. Relative to tension, the resistance to yielding does not decrease during relaxation, and it may actually increase. The decay of isometric tension after a controlled stretch also slows during relaxation. Consequently, cycling slows in those cross-bridges which form (or persist but produce less force) later in contraction. Changes in cross-bridge properties may restrict sarcomere shortening, prolong activation, but promote a disequilibrium which favors rapid relaxation in cardiac muscle.

Animals↗
PubMed2004

Synthesis and pharmacological screening for muscle relaxant, anticonvulsant, and sedative activities of certain organic compounds produced by Michael addition.

Michael addition of certain nucleophiles on alpha, beta-unsaturated ketones 1 led to the formation of adducts 2-7 as well as the reaction of arylidene derivatives with secondary amines afforded the amino compounds 9 and 11. Also, dialkylmalonates were treated with alpha-cyano cinnamide to afford 13. On the other hand, double Michael cycloaddition of ethylcyanoacetate or tetrachlorophthalic anhydride to the suitable divinylketone were synthesized to produce 15-17. Selected compounds (13 and 6) were screened for muscle relaxant, anticonvulsant, and sedative activities using established pharmacological models. Their activities were compared with that of phenobarbital sodium taken as standard. Compound 6 was the most potent muscle relaxant while compounds 13a and 13c offered the highest anticonvulsant activity. Meanwhile compound 13c showed the highest potentiation of phenobarbital induced sleep in mice.

Animals↗
PubMed2001

The effect of superoxide dismutase on nitric oxide-mediated and electrical field-stimulated diabetic rabbit cavernosal smooth muscle relaxation.

OBJECTIVE: To investigate the effect of superoxide dismutase (SOD, the enzyme that accelerates the breakdown of the superoxide anion, O2- to H2O) on nitric oxide (NO)-mediated and electrical field stimulated (EFS) relaxation in diabetic rabbit cavernosal smooth muscle. Materials and methods Diabetes was induced with alloxan (65 mg/kg) in six adult New Zealand White rabbits. After 6 months, cavernosal smooth muscle strips from age-matched controls and diabetic animals were mounted in organ baths. After precontraction with phenylephrine (10 micromol/L) in the presence of atropine (1 micromol/L), guanethidine (5 micromol/L) and indomethacin (10 micromol/L), relaxation responses to EFS (1-20 Hz), carbachol (10(-8)-10(-4) mol/L) and sodium nitroprusside (SNP, 10(-9)-10(-4) mol/L) were assessed in the presence and absence of SOD (100 IU/mL). RESULTS: SNP- and carbachol-mediated (endothelium-independent and -dependent, respectively) relaxations were impaired in the diabetic cavernosal smooth muscle strips compared with controls (concentration required for 50% inhibition, 1.4 micromol/L for diabetic and 0.75 micromol/L for control with SNP, and 44 micromol/L for diabetic and 0.4 micromol/L for control with carbachol). SOD significantly enhanced both SNP- and carbachol-mediated diabetic cavernosal smooth muscle relaxations (both P < 0.05). EFS-mediated relaxations were also significantly (P < 0.05) impaired in the diabetic cavernosal smooth muscle strips; these relaxations were also significantly (P < 0.05) enhanced by SOD. CONCLUSION: NO- and EFS-mediated cavernosal smooth muscle relaxation is impaired in a rabbit model of diabetes but SOD significantly reversed the impaired relaxation. Therefore, in diabetes, the generation of reactive oxygen species may play an important role in the development of erectile dysfunction.

Alloxan↗
PubMed1999

Assuming peripheral elimination: its impact on the estimation of pharmacokinetic parameters of muscle relaxants.

For anesthetic drugs undergoing nonorgan-based elimination, there is a definite trend towards using pharmacokinetic (PK) models in which elimination can occur from both central (k10) and peripheral compartments (k20). As the latter cannot be assessed directly, assumptions have to be made regarding its value. The primary purpose of this paper is to evaluate the impact of assuming various degrees of peripheral elimination on the estimation of PK parameters. For doing so, an explanatory model is presented where previously published data from our laboratory on three muscle relaxants, i.e., atracurium, doxacurium, and mivacurium, are used for simulations. The mathematical aspects for this explanatory model as well as for two specific applications are detailed. Our simulations show that muscle relaxants having a short elimination half-life are more affected by the presence of peripheral elimination as their distribution phase occupies the major proportion of their total area under the curve. Changes in the exit site dependent PK parameters (Vdss) are also mostly significant when k20 is smaller than k10. Although the physiological processes that determine drug distribution and those affecting peripheral elimination are independent, the two are mathematically tied together in the two-compartment model with both central and peripheral elimination. It follows that, as greater importance is given to k20, the rate of transfer from the central compartment (k12) increases. However, as a result of a proportional increase in the volume of the peripheral compartment, peripheral concentrations remain unchanged whether or not peripheral elimination is assumed. These findings point out the limitations of compartmental analysis when peripheral elimination cannot be measured directly.

Adolescent↗
PubMedDate not supplied

KATP channel openers reverse immune complex-induced airways hyperreactivity independently of smooth muscle relaxation.

Many openers of ATP-dependent potassium channels (KATP channel openers) cause bronchorelaxation, whereas only a few of them have been claimed to reverse airways hyperreactivity. We investigated whether the antihyperreactive effect is a general feature of KATP channel openers and whether this property is linked to their ability to relax airways smooth muscle. For this purpose, the potency of the four KATP channel openers, bimakalim, rilmakalim, levcromakalim and SDZ PCO 400 ((-)-(3S,4R)-3,4-dihydro-3-hydroxy-2,2-dimethyl-4-(3-oxo-cyclopent -1 -enyloxy)-2H-1-benzopyran-6-carbonitrile), to inhibit bombesin- or histamine-induced bronchoconstriction and to reverse immune complex-induced airways hyperreactivity to histamine in guinea pigs, was compared to salbutamol, following intratracheal administration to minimize pharmacokinetic differences. Total lung resistance (RL) was determined in anaesthetized, ventilated guinea pigs. Bronchoconstriction, measured as increase in RL, was elicited in normoreactive animals by i.v. infusion of bombesin (100 ng/kg/min) or by i.v. injection of histamine (1.8-10 micrograms/kg). Airways hyper-reactivity was induced by acute i.v. administration of preformed immune complexes. I.v. bolus injections of histamine were used to define the sensitivity of the airways prior to and after the exposure to immune complex. Levcromakalim (ED50 = 150 micrograms/kg), bimakalim (ED50 = 4 micrograms/kg), rilmakalim (ED50 = 40 micrograms/kg) and SDZ PCO 400 (ED50 = 280 micrograms/kg) reverse bombesin-induced bronchoconstriction with lower potency than salbutamol (ED50 = 1 microgram/kg). The four KATP channel openers and salbutamol also reversed immune complex-induced airways hyperreactivity to histamine with ED50 values which were markedly lower than those for reversal of bombesin-induced bronchoconstriction; the rank order of potency was rilmakalim (ED50 = 0.2 microgram/kg) > bimakalim (ED50 = 0.5 microgram/kg) > SDZ PCO 400 (ED50 = 3.2 micrograms/kg) > levcromakalim (ED50 = 22 micrograms/kg). Salbutamol (ED50 = 0.008 microgram/kg) was the most potent compound in this test. Bimakalim, levcromakalim and SDZ PCO 400 did not inhibit histamine-induced bronchoconstriction in normoreactive guinea pigs at doses which completely reversed immune complex-induced airways hyperreactivity to histamine. For rilmakalim and salbutamol, 60-130 times higher doses were needed for protection against histamine-induced bronchoconstriction in normoreactive guinea pigs than for reversal of airways hyperreactivity. There was a poor correlation between the ED50 values for inhibition of histamine- or bombesin-induced bronchoconstriction in normoreactive guinea pigs and the reversal of immune complex-induced airways hyperreactivity. It is thus concluded that the ability of KATP channel openers to reverse immune complex-induced airways hyperreactivity is independent of their ability to reverse or prevent bronchoconstriction and thus from their ability relax airway smooth muscle.

Albuterol↗
PubMed1999

Validation of a flow cytometric assay detecting in vitro basophil activation for the diagnosis of muscle relaxant allergy.

BACKGROUND: Anaphylactic reactions during anesthesia are mainly the result of muscle-relaxant (MR) drugs. Skin tests, serologic detection of specific IgE, and in vitro leukocyte histamine release are used to investigate MR allergy. OBJECTIVE: We describe a new assay that is based on the detection by flow cytometry of the altered expression of plasma membrane molecules of MR-activated basophils. METHODS: For this assay, which we have named the BASIC assay, basophils are incubated in vitro with MR, after which they are fixed and then triple labeled with fluorescein-conjugated anti-CD63, tandem dye R-phycoerythrin-cyanin 5.1 conjugated anti-CD45, and R-phycoerythrin conjugated anti-IgE. The resulting B asophils' A ltered S urface I mmunofluorescence is detected by flow C ytometry (BASIC). RESULTS: Forty-one patients who had an allergic reaction during general anesthesia and 23 control subjects without such a history were studied. All included subjects' basophils were tested in the BASIC assay with at least 4 MR: suxamethonium, gallamine, vecuronium, and pancuronium. After reaction of the basophils of the MR-allergic patients with MRs, increased surface expression of CD63 and CD45 and decreased expression of IgE were detected. Increased expression of CD63 was observed most frequently and it was stronger than the alteration of the 2 other markers. Cross-reactivity between MRs commonly occurred. MRs diluted 10(-1) activate the basophils of the control subjects, suggesting that at relatively high concentrations MRs are also nonspecific basophil activators. CONCLUSION: In the diagnosis of MR allergy, the BASIC assay has a good specificity but a low sensitivity, and it correlates strongly with skin test results. It is currently appraised for the diagnosis of anaphylactic reaction induced by other classes of drugs.

Adult↗