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At least 883 records · Page 49Linked to original sources
PubMed1995

Airway hyperresponsiveness in asthma: a problem of limited smooth muscle relaxation with inspiration.

We hypothesized that hyperresponsiveness in asthma is caused by an impairment in the ability of inspiration to stretch airway smooth muscle. If the hypothesis was correct, we reasoned that the sensitivity to inhaled methacholine in normal and asthmatic subjects should be the same if the challenge was carried out under conditions where deep inspirations were prohibited. 10 asthmatic and 10 normal subjects received increasing concentrations of inhaled methacholine under conditions where forced expirations from a normal end-tidal inspiration were performed. When no deep inspirations were allowed, the response to methacholine was similar in the normal and asthmatic subjects, compatible with the hypothesis we propose. Completely contrary to our expectations, however, was the marked responsivity to methacholine that remained in the normal subjects after deep breaths were initiated. 6 of the 10 normal subjects had > 20% reduction in forced expiratory volume in one second (FEV 1) at doses of methacholine < 8 mg/ml, whereas there was < 15% reduction with 75 mg/ml during routine challenge. The ability of normal subjects to develop asthmatic responses when the modulating effects of increases in lung volume was voluntarily suppressed suggests that an intrinsic impairment of the ability of inspiration to stretch airway smooth muscle is a major feature of asthma.

Adult↗
PubMed2005

The influence of a muscle relaxant bolus on bispectral and datex-ohmeda entropy values during propofol-remifentanil induced loss of consciousness.

Studies investigating the influence of muscle relaxants on the bispectral index have yielded contradictory results. In our prospective, randomized, double-blind experiments, patients received a fixed target concentration of remifentanil along with a target-controlled infusion of propofol, titrated until loss of consciousness. Two minutes after loss of consciousness, the study group received a bolus injection of atracurium, whereas the control group received a placebo. The following variables were recorded: bispectral index, spectral edge frequency, electromyographic activity, state entropy, and response entropy provided by the Datex-Ohmeda Entropy monitor. Similar values were obtained in both groups at loss of consciousness. Placebo administration induced a decrease in bispectral index (P < 0.002), spectral edge frequency (P < 0.05), electromyographic activity (P < 0.02), state entropy (P < 0.05), and response entropy (P < 0.01) compared with the values measured at loss of consciousness. Atracurium administration induced a decrease in bispectral index (P < 0.0001), spectral edge frequency (P < 0.01), electromyographic activity (P < 0.0001), state entropy (P < 0.0001), and response entropy (P < 0.0001) values. Decreases in bispectral index (P < 0.05), electromyographic activity (P < 0.0001), and response entropy (P < 0.01) were larger after atracurium than placebo injection. In lightly anesthetized patients, myorelaxant administration decreases bispectral index and response entropy, but not state entropy values.

Adult↗
PubMed1986

Effect of a smooth muscle relaxant from the stonefish, Synanceia trachynis, on KCl-induced responses in the guinea-pig vas deferens.

Stonefish skin secretion contains a smooth muscle relaxant, synancein II, that selectively inhibits tonic responses of KCl-induced contractions of the guinea-pig vas deferens. Synancein II (5-50 micrograms/ml) and nifedipine (10(-8)-10(-7) M) reduced tonic responses equally. Over these concentrations, synancein II inhibited phasic responses more than did nifedipine. Rapid inhibition of phasic responses by synancein II (low concentrations) but its inability to block this response at high concentrations suggests that more than one extracellular and/or intracellular Ca2+ source may contribute to the generation of the phasic response. Some calcium antagonists selectively inhibit tonic responses induced by KCl in many different organs, whilst others inhibit phasic responses. Whereas we previously reported that synancein II selectively inhibits phasic rather than tonic responses in the guinea-pig ileum, the present results reveals a reversal of this selectivity.

Animals↗
PubMed1996

Smooth muscle relaxant effects of tetrazepam on isolated guinea-pig and rat trachealis.

1. Tetrazepam (TZP) suppressed rat and guinea-pig tracheal tone by 100% and there was no difference in the relaxant effects against tone induced by 120 mM K+, carbachol (0.5 microM) or histamine (100 microM). 2. In trachealis pretreated with propranolol (1 microM), the relaxant response to TZP was unaltered. 3. TZP (10 microM) added to the relaxant effect of isoprenaline in tissues precontracted with carbachol. 4. The relaxant effect of TZP appears to be unrelated to peripheral benzodiazepine receptors (PBRs) because pretreatment with PK 11195 (1 microM) did not modify its effect. 5. Diltiazem (a calcium antagonist) was capable of relaxing the KCl (120 mM) or carbachol (0.5 microM) precontracted trachea, although at a different dose range than that of TZP. 6. The tracheal relaxation by TZP may be due to competition at some point in the chain of events linking carbachol, K+ or histamine to contraction, interacting with one of the transduction pathways, probably Ca2+. This inhibition of contraction is not related to the high-affinity PBRS.

Animals↗
PubMed2002

Monitoring of basophil activation using CD63 and CCR3 in allergy to muscle relaxant drugs.

Allergic or pseudoallergic reactions that occur during anesthesia have been increasing for the last few years. To date, the diagnosis of allergy to muscle relaxants remains difficult. In this respect, we developed a flow cytometric method for the study of drug-induced basophil degranulation using CD63 and CCR3. Fifty patients who developed clinical features evocative of allergic reactions immediately after induction of anesthesia were included and classified into two groups. Group 1 (n = 39) comprised true allergic patients, who developed typical signs of shock associated to positive skin testing. Group 2 (n = 11) consisted of patients whose clinical history was not typical and skin testing was negative or nonconclusive. Seventeen control subjects were also studied in this report. We compared data from flow cytometry to skin tests, specific IgE, and histamine release results. Flow cytometry showed a sensitivity of 54%, while that of specific IgE was similar, at 62%. Interestingly, when considering the sensitivity of IgE + CD63 for diagnosis, we reached a sensitivity value of 80%. Of 15 negative results for specific IgE, we found 7 positive CD63 tests, while histamine release gave positive results in only 2 cases. Furthermore, the CD63 protocol showed good specificity (100%). We conclude that our flow cytometry protocol is a promising tool in allergy diagnosis since it is specific and complementary to specific IgE detection.

Anesthesia, General↗
PubMed1969

Timing of atropine and neostigmine in the reversal of muscle relaxants.

The antimuscarinic effects of atropine were studied in 46 patients to whom neostigmine had been given after operation to reverse the action of a muscle relaxant. Neostigmine was given to alternate patients three minutes after, or together with, atropine, and the effects of the two procedures were compared by measuring the secretions which collected in the buccal and oropharyngeal cavities and observing the heart rate.It was found that the glands of the oral cavity were stimulated to a greater extent when neostigmine was given with atropine than after atropine. Any dose of atropine sufficient to inhibit peristaltic movements of the bowel is more than enough to block completely secretion by the salivary glands, and the appearance of some secretion in all cases after the administration of neostigmine suggests that the bowel was at liberty to react to the neostigmine in every case, but perhaps particularly so when atropine and neostigmine were given mixed. The integrity of an anastomosis of the bowel could be endangered by vigorous peristalsis in the early postoperative period.Electrocardiograms in about half the patients from each group confirmed earlier work that the muscarinic effects of neostigmine on the heart can be prevented by giving the atropine either before or together with the neostigmine.

Adult↗
PubMed1998

Effects of five different airway smooth muscle relaxants on inhibitory neurotransmission in isolated guinea-pig trachea in vitro.

Pharmacodynamic effects produced by terbutaline (10 nM), theophylline (10 microM), sodium nitroprusside (30 nM), levcromakalim (0.3 microM) or isradipine (1 nM) on frequency-dependent relaxations induced by electric field stimulation of either proximal or distal parts of isolated guinea-pig trachea were studied in vitro. Preparations were depleted for tachykinins by capsaicin, pretreated with atropine (0.1 microM) and contracted by histamine (2 microM). Drug effects were studied in preparations with combined adrenergic and inhibitory non-adrenergic non-cholinergic (NANC) innervation and in preparations with inhibitory NANC innervation either with or without additional treatment with N(G)-nitro-L-arginine methyl ester (L-NAME) (100 microM). In preparations with combined adrenergic and inhibitory NANC innervation terbutaline, sodium nitroprusside, levcromakalim and isradipine significantly reduced relaxant responses to electric field stimulation in proximal preparations, whereas distal preparations were only affected by terbutaline. In preparations with inhibitory NANC innervation without L-NAME pretreatment, terbutaline significantly enhanced relaxant responses to electric field stimulation only in distal preparations, whereas theophylline, sodium nitroprusside and levcromakalim significantly augmented responses to electric field stimulation in both proximal and distal preparations. In preparations with inhibitory NANC innervation pretreated with L-NAME, theophylline significantly inhibited relaxant responses in distal preparations, whereas sodium nitroprusside, levcromakalim and isradipine significantly augmented relaxant responses to electric field stimulation in proximal preparations. It was concluded that drugs used in the present study can modulate the effects of inhibitory autonomic and NANC neurotransmission in isolated guinea-pig trachea. Furthermore, it was shown that some variation in drug effects exists in relation to proximal and distal parts of guinea-pig trachea.

Animals↗