Novel strategy for biofilm inhibition by using small molecules targeting molecular chaperone DnaK.

Biofilms are complex communities of microorganisms that attach to surfaces and are embedded in a self-produced extracellular matrix. Since these cells acquire increased tolerance against antimicrobial agents and host immune systems, biofilm-associated infectious diseases tend to become chronic. We show here that the molecular chaperone DnaK is important for biofilm formation and that chemical inhibition of DnaK cellular functions is effective in preventing biofilm development. Genetic, microbial, and microscopic analyses revealed that deletion of the dnaK gene markedly reduced the production of the extracellular functional amyloid curli, which contributes to the robustness of Escherichia coli biofilms. We tested the ability of DnaK inhibitors myricetin (Myr), telmisartan, pancuronium bromide, and zafirlukast to prevent biofilm formation of E. coli. Only Myr, a flavonol widely distributed in plants, inhibited biofilm formation in a concentration-dependent manner (50% inhibitory concentration [IC50] = 46.2 µM); however, it did not affect growth. Transmission electron microscopy demonstrated that Myr inhibited the production of curli. Phenotypic analyses of thermosensitivity, cell division, intracellular level of RNA polymerase sigma factor RpoH, and vulnerability to vancomycin revealed that Myr altered the phenotype of E. coli wild-type cells to make them resemble those of the isogenic dnaK deletion mutant, indicating that Myr inhibits cellular functions of DnaK. These findings provide insights into the significance of DnaK in curli-dependent biofilm formation and indicate that DnaK is an ideal target for antibiofilm drugs.

Haemodynamic differences between pancuronium and vecuronium in an experimental pig model.

OBJECTIVE: To compare baseline cardiovascular function in anesthetised pigs using either pancuronium or vecuronium as a neuromuscular blocker. STUDY DESIGN: Retrospective, non-randomized comparison. ANIMALS: Norwegian Land Race pigs (Sus scrofa domesticus) weighing mean 42 ± SD 3 kg. METHODS: One hundred and sixteen animals from four different research protocols premedicated with identical doses of ketamine, diazepam, atropine and isoflurane, and anaesthetised with pentobarbital, fentanyl, midazolam and N(2)O were arranged into three uniform groups with respect to neuromuscular blocking agent: pancuronium bolus of 0.063 mg kg(-1) followed by 0.14 mg kg(-1) hour(-1) (n = 54), low-dose vecuronium 0.4 mg kg(-1) /0.2 mg kg(-1) hour(-1) (n = 29) and high-dose vecuronium 0.6 mg kg(-1) /0.3 mg kg(-1) hour(-1) (n = 33). RESULTS: The majority of cardiovascular parameters demonstrated no significant differences between groups. For heart rate, there was an overall group difference, p = 0.036. Dromotropy was low in the pancuronium group, with an increased normalised PR-interval compared to the high-dose vecuronium group, median 0.200 interquartile range (0.190, 0.215) versus 0.182 (0.166, 0.199), p < 0.05. Left ventricular compliance was increased in pancuronium-treated animals, demonstrated as a reduction in the nonlinear end-diastolic pressure volume relationship ß compared to both vecuronium groups, 0.021 (0.016, 0.025) versus 0.031 (0.025, 0.046) and 0.031 (0.022, 0.048), p < 0.05. The linear end-diastolic pressure volume relationship EDPVR(lin) was reduced as well in the pancuronium group, compared to the low-dose vecuronium group, 0.131 (0.116, 0.169) versus 0.181 (0.148, 0.247), p < 0.05. CONCLUSIONS: There are only minor haemodynamic differences when using pancuronium compared to vecuronium in the fentanyl-pentobarbital-midazolam-N(2)O anesthetised domestic pigs. Furthermore, increasing doses of vecuronium have minimal haemodynamic effects. CLINICAL RELEVANCE: Experimental studies in pigs using either pancuronium or vecuronium as a neuromuscular blocking agent are comparable with regard to cardiac and haemodynamic performance.

Pancuronium dose refinement in experimental pigs used in cardiovascular research.

OBJECTIVE: To quantify the dose of pancuronium required to obtain moderate neuromuscular blockade as monitored by acceleromyography (NMB(mod) : train-of-four count of ≤2) as a part of a balanced anaesthetic protocol in pigs used in cardiovascular research. STUDY DESIGN: Prospective cross-sectional study. ANIMALS: Five pigs (median body weight: 60 (range 60-63) kg). METHODS: Anaesthesia was induced with xylazine, ketamine, atropine and midazolam and maintained with isoflurane in O(2) :air and fentanyl. Pigs received 0.1 mg kg(-1) pancuronium initial bolus to reach NMB(mod) followed by 0.1 mg kg(-1) hour(-1) constant rate infusion (CRI). During anaesthesia a twitch count of 3 or measureable T4/T1 ratio indicated unsatisfactory NMB. In this case additional 0.4 mg boluses of pancuronium were administered IV to effect in addition to the CRI. Descriptive statistical analysis was performed to express the median and range of the bolus and CRI dose of pancuronium in pigs. Cardiovascular parameters were analyzed at selected time points with Friedman Repeated Measures Analysis on Ranks. Spearman Rank test was used to evaluate correlation between parameters. RESULTS: Acceleromyographic monitoring of NMB is feasible in anaesthetized pigs. The median initial dose and rate of pancuronium required to achieve NMB(mod) were 0.10 (range 0.10-0.13) mg kg(-1) and 0.11 (range 0.10-0.21) mg kg(-1) hour(-1) , respectively. The administration rate showed considerable individual variation. CONCLUSIONS AND CLINICAL RELEVANCE: These pancuronium doses can be used as a guideline to achieve NMB(mod) in pigs as part of a balanced anaesthetic protocol. Instrumental NMB monitoring is essential because of individual kinetic variations and compliance to monitoring guidelines.

Variability in the muscle composition of rat esophagus and neural pathway of lower esophageal sphincter relaxation.

Several studies from our laboratory show that axial stretch of the lower esophageal sphincter (LES) in an oral direction causes neurally mediated LES relaxation. Under physiological conditions, axial stretch of the LES is caused by longitudinal muscle contraction (LMC) of the esophagus. Because longitudinal muscle is composed of skeletal muscle in mice, vagal-induced LMC and LES relaxation are both blocked by pancuronium. We conducted studies in rats (thought to have skeletal muscle esophagus) to determine if vagus nerve-mediated LES relaxation is also blocked by pancuronium. LMC-mediated axial stretch on the LES was monitored using piezoelectric crystals. LES and esophageal pressures were monitored with a 2.5-Fr solid-state pressure transducer catheter. Following bilateral cervical vagotomy, the vagus nerve was stimulated electrically. LES, along with the esophagus, was harvested after in vivo experiments and immunostained for smooth muscle (smooth muscle α-actin) and skeletal muscle (fast myosin heavy chain). Vagus nerve-stimulated LES relaxation and esophageal LMC were reduced in a dose-dependent fashion and completely abolished by pancuronium (96 µg/kg) in six rats (group 1). On the other hand, in seven rats, LES relaxation and LMC were only blocked completely by a combination of pancuronium (group 2) and hexamethonium. Immunostaining revealed that the longitudinal muscle layer was composed of predominantly skeletal muscle in the group 1 rats. On the other hand, the longitudinal muscle layer of group 2 rats contained a significant amount of smooth muscle (P < 0.05). Our study shows tight coupling between axial stretch on the LES and relaxation of the LES, which suggests a cause and effect relationship between the two. We propose that the vagus nerve fibers that cause LMC induce LES relaxation through the stretch-sensitive activation of inhibitory motor neurons.

Ivermectin effects on motor coordination and contractions of isolated rat diaphragm.

Ivermectin, the antiparasitic drug from the macrocyclic lactones class raises attention due to its high efficiency against nematodes and arthropods and very specific toxic and side effects that it may produce in host. Dominant clinical symptoms of adverse effects and toxicity of ivermectin in animals are tremor, ataxia, CNS depression and coma which often results in mortality. In our study increasing intravenous doses of ivermectin, (6 or more times higher than therapeutic dose: 1.25, 2.5, 3.75, 5.0, 6.25 and 7.5 mg/kg), caused dose-dependent disturbance of motor coordination in treated rats. The median effective dose (ED50) that was able to impair the rota-rod performance in rats treated 3 min before testing was 2.52 mg/kg. This effect weakens over time, while in the rats treated 60 min before the rota-rod test, ED50 of ivermectin was 4.21 mg/kg. Whereas, all tested doses of ivermectin did not cause any other clinical symptoms of toxicity. Ivermectin has no effect on the contractions of isolated diaphragm caused by the EFS, which effectively blocked mecamylamine (100 µM) and pancuronium (1 and 2 µM). Effect on motor coordination is the first detectable clinical symptom of ivermectin toxicity and apparently is a result of its central effects.

Investigation of the relaxant effects of pancuronium, rocuronium, vecuronium and mivacurium on rat thoracic aorta.

BACKGROUND AND OBJECTIVE: Pancuronium, vecuronium, mivacurium and rocuronium are nondepolarizing neuromuscular blocking agents, which are competitive antagonists against acetylcholine at nicotinic receptors, and considered to have no direct actions on vascular smooth muscle. We aimed to investigate the relaxant effects and possible underlying mechanisms of these agents on isolated rat thoracic aorta. METHODS: The preparations were precontracted with prostaglandin F2alpha (10(-7) mol l(-1)) and pancuronium (10(-7)-10(-4) mol l(-1)), rocuronium (10(-7)-10(-4) mol l(-1)), vecuronium (10(-7)-10(-4) mol l(-1)) and mivacurium (10(-7)-10(-4) mol l(-1)) added at cumulative concentrations in the presence or absence of a prostaglandin synthesis inhibitor, indomethacin (10(-6) M), and a nitric oxide synthesis inhibitor, N(omega)-nitro-L-arginine methylester (3 x 10(-5)). The same protocol was applied to both endothelia (+) and endothelia (-) aortic rings. The preparations precontracted with prostaglandin F2alpha (10(-7) mol l(-1)) were stimulated with electrical field stimulation at a frequency of 10 Hz as square-wave pulses of 50 V (0.2 ms) in the presence of a noradrenaline reuptake inhibitor desipramine (10(-7) mol l(-1)) and a nonselective beta-blocker propranolol (10(-6) mol l(-1)). Drugs were added at ineffective concentration of 10(-7) mol l(-1). Tetrodotoxin (10(-7) mol l(-1)) was added to test whether the changes were dependent on the neuronal response. RESULTS: Pancuronium and rocuronium relaxed aortic rings precontracted by prostaglandin F2alpha in a dose-dependent manner, but vecuronium and mivacurium did not. The relaxation effect of pancuronium and rocuronium was endothelium independent because there was not a significant response difference from the endothelium-denuded group. CONCLUSION: In conclusion, their relaxation effect may be due to an increase in prostaglandin synthesis. The increased relaxation effect of these agents at electrical field stimulation may be by the decreasing effect of noradrenaline reuptake from nerve endings because a noradrenaline reuptake inhibitor desipramine did not change this effect. Also, these neuromuscular agents may affect beta-receptors, because a nonselective beta-blocker agent, propranolol, decreased their electrical field stimulation-induced relaxations.

Site selectivity of competitive antagonists for the mouse adult muscle nicotinic acetylcholine receptor.

The muscle-type nicotinic acetylcholine receptor has two nonidentical binding sites for ligands. The selectivity of acetylcholine and the competitive antagonists (+)-tubocurarine and metocurine for adult mouse receptors is known. Here, we examine the site selectivity for four other competitive antagonists: cisatracurium, pancuronium, vecuronium, and rocuronium. We rapidly applied acetylcholine to outside-out patches from transfected BOSC23 cells and measured macroscopic currents. We have reported the IC(50) of the antagonists individually in prior publications. Here, we determined inhibition by pairs of competitive antagonists. At least one antagonist was present at a concentration producing > or =67% receptor inhibition. Metocurine shifted the apparent IC(50) of (+)-tubocurarine in quantitative agreement with complete competitive antagonism. The same was observed for pancuronium competing with vecuronium. However, pancuronium and vecuronium each shifted the apparent IC(50) of (+)-tubocurarine less than expected for complete competition but more than expected for independent binding. The situation was similar for cisatracurium and (+)-tubocurarine or metocurine. Cisatracurium did not shift the apparent IC(50) of pancuronium or vecuronium, indicating independent binding of these two pairs. The data were fit to a two-site, two-antagonist model to determine the antagonist binding constants for each site, L(alphaepsilon) and L(alphadelta). We found L(alphaepsilon)/L(alphadelta) = 0.22 (range, 0.14-0.34), 20 (9-29), 21 (4-36), and 1.5 (0.3-2.9) for cisatracurium, pancuronium, vecuronium, and rocuronium, respectively. The wide range of L(alphaepsilon)/L(alphadelta) for some antagonists may reflect experimental uncertainties in the low affinity site, relatively poor selectivity (rocuronium), or possibly that the binding of an antagonist at one site affects the affinity of the second site.

[Delayed diagnosis of a postanaesthesia temporomandibular joint dislocation]. / Luxation de l'articulation temporomandibulaire diagnostiquée au décours d'une anesthésie générale.

Temporomandibular joint (TMJ) dislocation during anaesthesia is a rare occurrence. Patients with a history of prior dislocations or TMJ dysfunction, and patients with mandibular retrognathism are at risk of this complication. This is a case report of delayed diagnosis of TMJ dislocation after a general anaesthesia for aortic valvular replacement surgery in a predisposed patient. Considering this unusual presentation, TMJ evaluation should be performed during preoperative anaesthetic assessment. In at-risk patients, one should not worry about TMJ dislocation during intubation but concentrate on glottic exposure. However, afterwards, one should be highly aware of this possible complication in order to detect it early, allowing an immediate simple manual reduction. This manoeuver may be performed with or without sedation by a practitioner, familiar with this way of resetting a dislocated jaw.

Dose-response effect of serum butyrylcholinesterase activity after clinical doses of pancuronium.

INTRODUCTION: Low-dose pancuronium is known to affect serum cholinesterase activity (BChE); however, the dose-response effect of clinical doses of pancuronium on BChE has not been investigated. METHODS: Thirteen ASA I-II patients scheduled for elective surgery requiring muscle relaxation were enrolled in this study. All patients had normal BChE before surgery. Incremental doses of pancuronium (10, 20, 50, and 100 microg/kg) were injected in accordance with surgical needs every 45 min. BChE was measured 3 min after injection by an automatic colorimetric method. RESULTS: BChE decreased significantly in all except one patient in comparison to the baseline (P < 0.05). However all values remained within normal clinical range. A dose of 100 microg/kg yielded significant decrease in comparison to 10 microg/kg but not to other dosages. Linear regression was not significant for the dose-response relationship (P = 0.05). CONCLUSION: After clinical incremental doses of pancuronium, BChE remained within clinical range.

Roles of amino acids and subunits in determining the inhibition of nicotinic acetylcholine receptors by competitive antagonists.

BACKGROUND: Binding sites for agonists and competitive antagonists (nondepolarizing neuromuscular blocking agents) are located at the alpha-delta and alpha-epsilon subunit interfaces of adult nicotinic acetylcholine receptors. Most information about the amino acids that participate in antagonist binding comes from binding studies with (+)-tubocurarine and metocurine. These bind selectively to the alpha-epsilon interface but are differentially sensitive to mutations. To test the generality of this observation, the authors measured current inhibition by five competitive antagonists on wild-type and mutant acetylcholine receptors. METHODS: HEK293 cells were transfected with wild-type or mutant (alphaY198F, epsilonD59A, epsilonD59N, epsilonD173A, epsilonD173N, deltaD180K) mouse muscle acetylcholine receptor complementary DNA. Outside-out patches were excised and perfused with acetylcholine in the absence and presence of antagonist. Concentration-response curves were constructed to determine antagonist IC50. An antagonist-removal protocol was used to determine dissociation and association rates. RESULTS: Effects of mutations were antagonist specific. alphaY198F decreased the IC50 of (+)-tubocurarine 10-fold, increased the IC50 of vecuronium 5-fold, and had smaller effects on other antagonists. (+)-Tubocurarine was the most sensitive antagonist to epsilonD173 mutations. epsilonD59 mutations had large effects on metocurine and cisatracurium. deltaD180K decreased inhibition by pancuronium, vecuronium, and cisatracurium. Inhibition by these antagonists was increased for receptors containing two delta subunits but no epsilon subunit. Differences in IC50 arose from differences in both dissociation and association rates. CONCLUSION: Competitive antagonists exhibited different patterns of sensitivity to mutations. Except for pancuronium, the antagonists were sensitive to mutations at the alpha-epsilon interface. Pancuronium, vecuronium, and cisatracurium were selective for the alpha-delta interface. This suggests the possibility of synergistic inhibition by pairs of antagonists.

Sepsis stage dependently and differentially attenuates the effects of nondepolarizing neuromuscular blockers on the rat diaphragm in vitro.

We investigated the effects of early and late sepsis on the actions of nondepolarizing neuromuscular blockers by using a rat sepsis model induced by cecal ligation and puncture. Isometric twitch tensions of nerve-hemidiaphragm preparations elicited by indirect (phrenic nerve) supramaximal stimulation at 0.1 Hz were evaluated. Rocuronium, pancuronium, and d-tubocurarine dose-dependently decreased the twitch tensions of the nonseptic, early septic, and late septic diaphragms (P < 0.01 each by analysis of variance [ANOVA]). Late sepsis shifted the concentration-twitch tension curves rightward from those of nonsepsis to larger degrees than did early sepsis, as indicated by increases in 50% inhibitory concentration (IC(50)) values (P < 0.01 each by ANOVA and P < 0.01 or 0.05 by the Scheffe F test). The standardized rightward shifts in early and late sepsis were largest for pancuronium, second largest for rocuronium, and smallest for d-tubocurarine (5.741, 2.979, and 1.660 times in late sepsis, respectively; P < 0.01 each by ANOVA and the Scheffe F test). Sepsis-induced increases in IC(50) values did not accompany the decreases in slopes. The results indicate that sepsis induces hyposensitivities to nondepolarizing neuromuscular blockers, the degree of which depends on the stage of sepsis and on the kind of neuromuscular blocker.

Pancuronium bromide, a non-depolarizing muscle relaxant which promotes apoptosis of blood lymphocytes in vitro.

BACKGROUND: Several compounds used in anesthesia practice have demonstrated to impair immune function and to influence the process of apoptotic death in T cell population following surgical trauma. We designed this study to test in vitro the impact of neuromuscular blocker, such as pancuronium, at clinically relevant concentration on lymphocyte apoptosis, death factor expression and mitochondrial function. METHODS: Following isolation, lymphocytes were incubated with pancuronium bromide at a clinically relevant concentration (0.136 micro mol l-1) for 3 h at 37 C in a 5% carbon-dioxide-humidified atmosphere and the frequency of apoptotic lymphocytes was then measured. We also investigated crucial steps in the apoptotic process, including Fas/Fas ligand (FasL) phenotype, intracellular expression of the interleukin-1beta-converting enzyme (ICE) p20, mitochondrial membrane potential (DeltaPsim), generation of mitochondrial reactive oxygen species, and glutathione (GSH) levels. Control experiments were performed incubating cells in the complete culture medium added with the dilution medium of the drug without addition of the drug. RESULTS: Expression of Fas, FasL and ICEp20 was six-fold, four-fold, and five-fold increased, respectively, among pancuronium-treated lymphocytes with respect to control cultures (P = 0.0001). The percentage of cells exhibiting either dissipation of mitochondrial membrane potential or increased production of reactive oxygen species was seven-fold increased following exposure to pancuronium compared with untreated lymphocytes (P = 0.0001). These findings were associated with a decrease in GSH level. In addition, the frequency of apoptotic cells was 10-fold greater among lymphocytes cultured in the presence of the drug with respect to control cultures. (P = 0.0001). CONCLUSION: Our data suggest an apoptogenic effect of pancuronium in vitro at clinically relevant concentration on peripheral blood lymphocytes. This could be implicated in the transient immune suppression following a surgical operation.

Tolerance to acute isovolemic hemodilution. Effect of anesthetic depth.

BACKGROUND: Acceptance of a lower transfusion trigger in the perioperative period requires study of the effects of anesthetic depth on the tolerance to acute isovolemic anemia. Anesthetic agents with negative effects on the cardiovascular system may exert proportionately greater depressant effects on cardiac output response than on tissue oxygen demand, reducing tolerance to acute isovolemic anemia. METHODS: In the first study, animals were anesthetized with halothane (n = 14; 23.8 +/- 4.8 kg, mean +/- SD). In a second study, animals were anesthetized with ketamine (n = 14; 24.3 +/- 4.7 kg). In each study, dogs were randomly allocated to receive either low or high concentrations of anesthetic. Oxygen delivery and oxygen consumption were determined from independent measurements during a stepwise isovolemic hemodilution protocol. In each dog, critical oxygen delivery was determined from a plot of oxygen consumption versus oxygen delivery using a least-sum-of-squares technique. Critical hemoglobin (hemoglobin) was determined from a plot of hemoglobin versus oxygen consumption using the same method. RESULTS: With both agents, the higher anesthetic concentration was associated with decreased oxygen consumption, resulting in a lower critical oxygen delivery. However, critical hemoglobin was significantly higher in the animals receiving the higher anesthetic dosage (1.5 vs. 1.0 minimum alveolar concentration of halothane: 4.1 +/- 1.3 vs. 2.3 +/- 0.5 g/dl, P < 0.05; high- vs. low-dose ketamine: 3.7 +/- 1.4 vs. 2.5 +/- 0.6 g/dl, P < 0.05). This was related to a marked blunting of the cardiac output response to hemodilution in the animals receiving the higher anesthetic dosage. CONCLUSIONS: Increased anesthetic depth with halothane or ketamine resulted in a decreased tolerance to acute anemia, as reflected by a significant increase in critical hemoglobin concentration.

Potentiation of mivacurium blockade by low dose of pancuronium: a pharmacokinetic study.

BACKGROUND: Mivacurium is potentiated by pancuronium to a much greater extent than other relaxants. In a previous investigation we suggested that this potentiation could be due to the ability of pancuronium to inhibit plasma cholinesterase activity, but we did not measure plasma concentrations of mivacurium. In the current study we performed a pharmacokinetic analysis by measuring the plasma concentration of mivacurium when preceded by administration of a low dose of pancuronium. METHODS: After induction of general anesthesia with propofol and fentanyl and orotracheal intubation, 10 patients (pancuronium-mivacurium group) received 15 microg/kg pancuronium followed 3 min later by 0.1 mg/kg mivacurium, whereas 10 other patients (mivacurium group) received saline followed by 0.13 mg/kg mivacurium 3 min later. Plasma cholinesterase activity was measured before and 3 and 30 min after pancuronium dosing in the pancuronium-mivacurium group and was measured before and after administration of saline in the mivacurium group. Arterial plasma concentrations of mivacurium and its metabolites were measured at 0.5, 1, 1.5, 2, 4, 10, 20, and 30 min after injection. Neuromuscular blockade was assessed by mechanomyography. RESULTS: Plasma cholinesterase activity decreased by 26% in the pancuronium-mivacurium group 3 min after injection of pancuronium (P < 0.01) and returned to baseline values 30 min later; however, no significant variation was observed in the mivacurium group. The clearances of the two most active isomers (Cis-Trans and Trans-Trans) were lower in the pancuronium-mivacurium group (17.6 +/- 5.1, 14.7 +/- 5.3 ml. min-1. kg-1, respectively) than in the mivacurium group (32.4 +/- 20.2, 24.8 +/- 13.5 ml. min-1. kg-1; P < 0.05). CONCLUSIONS: A subparalyzing dose of pancuronium decreased plasma cholinesterase activity and the clearance of the two most active isomers of mivacurium. Pancuronium potentiates mivacurium more than other neuromuscular blocking agents because, in addition to its occupancy of postsynaptic acetylcholine receptors, it slows down the hydrolysis of mivacurium.

Effect of neuromuscular blockade on energy expenditure in patients with severe head injury.

BACKGROUND: The purpose of this study was to determine the effect of neuromuscular blockade on energy expenditure in severely head-injured patients; to determine the effects of body temperature, nutrition support, and morphine use on metabolic rate; and to compare measured energy expenditure with values from predictive equations. METHODS: Energy expenditure was measured using indirect calorimetry in 2 groups of ventilated patients-18 with severe head injury during and after administration of pancuronium bromide and morphine, and second, 14 severely traumatized patients without severe head injury (trauma group) who received morphine without neuromuscular blockade. RESULTS: The mean energy expenditure of head-injured patients increased significantly once pancuronium was discontinued, ie, from 24.2 +/- 3.1 to 28.7 +/- 4.6 kcal/kg (p = .002). This effect was independent of other relevant variables such as morphine dose, body temperature, and nutrition support. When compared with the Harris-Benedict and World Health Organization predictive equations, neuromuscular blockade resulted in a stress factor of only 0.96 and 0.95, respectively, which increased to 1.19 and 1.18, respectively, once blockade was discontinued. Head-injured patients not on neuromuscular blockade had a significantly greater energy expenditure when compared with the trauma group (p = .02). CONCLUSIONS: Neuromuscular blockade in severely head-injured patients decreases energy expenditure to basal levels, independent of morphine use, body temperature, and feeding. Levels of hypermetabolism in both the head-injured and trauma groups were relatively low, at 19% and 5% above predicted values, respectively. This study provides useful information for the management of nutrition support in severely traumatized patients.

[Hemostatic profile of women using low-dose oral contraceptive Mercilon. (Preliminary report)]. / Khemostazen profil pri zheni upotrebiavashti niskodoziraniia oralen kontratseptiv--Mercilon (predvaritelno suobshtenie).

The authors have investigated the hemostatic profile at 20 women using low-dosed oral contraceptive Mercilon (Organon) in continuation of six months. Statistically significant changes are found for factor X of hemocoagulation, plasminogen, protein C, protein S and antithrombin III. It is concluded that Mercilon causes activation of the coagulation system, which is balanced by the activation of the fibrinolytic system.

Isobolographic analysis of non-depolarising muscle relaxant interactions at their receptor site.

Administration of certain combinations of non-depolarising muscle relaxants produces greater than expected neuromuscular blockade. Synergistic effects may be explained by drug interactions with the postsynaptic muscle nicotinic acetylcholine receptor. To investigate this hypothesis, the adult mouse muscle nicotinic acetylcholine receptor (alpha(2)beta delta epsilon) was heterologously expressed in Xenopus laevis oocytes and activated by the application of acetylcholine (10 microM). The effects of five individually applied muscle relaxants and six combinations of structurally similar and dissimilar compounds were studied. Drug combinations containing equipotent concentrations of two agents were tested and dose-response curves were determined. All compounds tested alone and in combination produced rapid and readily reversible, concentration-dependent inhibition. Isobolographic and fractional analyses indicated additive interactions for all six tested combinations. These findings suggest that synergistic neuromuscular blocking effects, observed for the administration of certain combinations of muscle relaxants, do not result from purely postsynaptic binding events at the muscle nicotinic acetylcholine receptor, but rather from differential actions on pre- and postsynaptic sites.

Do muscle relaxants influence vascular tone in isolated coronary artery segments?

The aim of this study was to elucidate the influence of four neuromuscular blocking substances on coronary vascular tone using the model of isolated porcine coronary artery segments. We studied the effects of four muscle relaxants, atracurium, pancuronium, rocuronium, and vecuronium (0.1, 1, and 10 microg mL-1 each), on the contractile response to three vasoconstrictors: acetylcholine, histamine, and serotonin. None of the neuromuscular blocking agents under investigation exerted a significant influence on the vasoconstricting effects of these mediators except for pancuronium, which dose-dependently attenuated acetylcholine-mediated contractions (-10.8% attenuation for 10 microg mL-1 pancuronium, P < 0.05). There was no difference between vessels with intact endothelium and denuded preparations. It is concluded that high-dose pancuronium exerts an antimuscarinic effect in vascular smooth muscle. The other neuromuscular agents studied do not alter vascular reactivity of isolated porcine coronary arteries.

The mechanism of pancuronium potentiation of mivacurium block: use of the isolated-arm technique.

UNLABELLED: The neuromuscular blocking effects of mivacurium are greatly enhanced when mivacurium is preceded by a subparalyzing dose of pancuronium. The mechanism of this potentiation has not been elucidated. This study investigated the effects of the anticholinesterase activity of a small dose of pancuronium on the neuromuscular blocking effects of mivacurium. Forty patients were enrolled in the study. The neuromuscular effects of 7.5 and 15 microg/kg pancuronium, followed by 50 and 100 microg/kg mivacurium, were assessed in Groups PM1 and PM2 (n = 20), respectively. The neuromuscular effects of 65 and 130 microg/kg mivacurium were assessed in Groups M1 and M2 (n = 20), respectively. One arm was excluded from circulation with a tourniquet, which was inflated before the injection of pancuronium and deflated 3 min after the injection of mivacurium. The plasma cholinesterase activity was measured before induction for all patients and 3 min after the injection of pancuronium for Groups PM1 and PM2. The plasma cholinesterase activity was decreased by 16% and 33% after pancuronium administration in Groups PM1 and PM2, respectively. In the nonexcluded arm, pancuronium significantly potentiated the effects of mivacurium. In the excluded arm, no significant block was detected for Groups M1 and M2, whereas the maximal degree of neuromuscular block was 79% and 100% for Groups PM1 and PM2, respectively. Using the isolated-arm technique, we suggest that pancuronium potentiation of the neuromuscular blocking effects of mivacurium is more likely attributable to an increase in the effective plasma concentration of mivacurium than to occupancy of postsynaptic acetylcholine receptors. IMPLICATIONS: Using the isolated-arm technique, we suggest that pancuronium potentiation of the neuromuscular blocking effects of mivacurium is more likely attributable to an increase in the effective plasma concentration of mivacurium than to occupancy of postsynaptic acetylcholine receptors.

Effects of non-depolarizing neuromuscular blocking agents on norepinephrine release from human atrial tissue obtained during cardiac surgery.

We have studied the effect of non-depolarizing neuromuscular blocking agents, at concentrations present in serum during anaesthesia, on release of [3H]-norepinephrine ([3H]NE) from superfused atrial appendage obtained during cardiac surgery from 48 patients. Three of the neuromuscular blocking agents (pancuronium, gallamine and rocuronium), which are known to cause an increase in heart rate during anaesthesia, increased stimulation-evoked release of [3H]NE. In contrast, (+)tubocurarine and pipecuronium, neuromuscular blocking agents that do not cause tachycardia, did not affect release of NE. Org 9487 significantly enhanced release while SZ1677 was ineffective, even at concentrations higher than those expected after administration of a 2 x ED95 dose. Atropine enhanced release. These data suggest that the axon terminals of sympathetic nerves in human heart have muscarinic heteroreceptors whose activation by acetylcholine (ACh) released from the vagal nerve reduces release of NE. This action contributes to lowering of heart rate. Therefore, any neuromuscular blocking agent with antimuscarinic actions and capable of increasing the release of NE may produce tachycardia.