Allosteric inhibition of muscle-type nicotinic acetylcholine receptors by a neuromuscular blocking agent pancuronium.

Muscle relaxants are indispensable for surgical anesthesia. Early studies suggested that a classical non-depolarizing muscle relaxant pancuronium competitively binds to the ligand binding site to block nicotinic acetylcholine receptors (nAChR). Our group recently showed that nAChR which has two distinct subunit combinations are expressed in zebrafish muscles, αßδε and αßδ, for which potencies of pancuronium are different. Taking advantage of the distinct potencies, we generated chimeras between two types of nAChRs and found that the extracellular ACh binding site is not associated with the pancuronium sensitivity. Furthermore, application of either 2 µM or 100 µM ACh in native αßδε or αßδ subunits yielded similar IC50 of pancuronium. These data suggest that pancuronium allosterically inhibits the activity of zebrafish nAChRs.

Effect of preoperative ivabradine on hemodynamics during elective off-pump CABG.

Background: Ivabradine is a specific heart rate (HR)-lowering agent which blocks the cardiac pacemaker If channels. It reduces the HR without causing a negative inotropic or lusitropic effect, thus preserving ventricular contractility. The authors hypothesized that its usefulness in lowering HR can be utilized in patients undergoing off-pump coronary artery bypass (OPCAB) surgery. Objective: To study the effects of preoperative ivabradine on hemodynamics (during surgery) in patients undergoing elective OPCAB surgery. Methods: Fifty patients, New York Heart Association (NYHA) class I and II, were randomized into group I (control, n = 25) and group II (ivabradine group, n = 25). In group I, patients received the usual anti-anginal medications in the preoperative period, as per the institutional protocol. In group II, patients received ivabradine 5 mg twice daily for 3 days before surgery, in addition to the usual anti-anginal medications. Anesthesia was induced with fentanyl, thiopentone sodium, and pancuronium bromide as a muscle relaxant and maintained with fentanyl, midazolam, pancuronium bromide, and isoflurane. The hemodynamic parameters [HR and mean arterial pressure (MAP)] and pulmonary artery (PA) catheter-derived data were recorded at the baseline (before induction), 3 min after the induction of anesthesia at 1 min and 3 min after intubation and at 5 min and 30 min after protamine administration. Intraoperatively, hemodynamic data (HR and MAP) were recorded every 10 min, except during distal anastomosis of the coronary arteries when it was recorded every 5 min. Post-operatively, at 24 hours, the levels of troponin T and brain natriuretic peptide (BNP) were measured. This trial's CTRI registration number is CTRI/005858. Results: The HR in group II was lower when compared to group I (range 59.6-72.4 beats/min and 65.8-80.2 beats/min, respectively) throughout the study period. MAP was comparable [range (78.5-87.8 mm Hg) vs. (78.9-88.5 mm Hg) in group II vs. group I, respectively] throughout the study period. Intraoperatively, 5 patients received metoprolol in group I to control the HR, whereas none of the patients in group II required metoprolol. The incidence of preoperative bradycardia (HR <60 beats/min) was higher in group II (20%) vs. group I (8%). There was no difference in both the groups in terms of troponin T and BNP level after 24 hours, time to extubation, requirement of inotropes, incidence of arrhythmias, in-hospital morbidity, and 30-day mortality. Conclusion: Ivabradine can be safely used along with other anti-anginal agents during the preoperative period in patients undergoing OPCAB surgery. It helps to maintain a lower HR during surgery and reduces the need for beta-blockers in the intraoperative period, a desirable and beneficial effect in situations where the use of beta-blockers may be potentially harmful. Further studies are needed to evaluate the beneficial effects of perioperative Ivabradine in patients with moderate-to-severe left ventricular dysfunction.

Predictive stability, novel HPLC-MS analysis and semi-automatic compounding process for the emergency implementation of a production line of pancuronium in injectable solution.

During the early months of the COVID-19 pandemic, the international medical product supply chain was tight, causing breaks in the availability of neuromuscular blocking agents essential for the treatment of patients in intensive care units. The present study describes the pharmaceutical development of an injectable 2 mg/mL solution of pancuronium bromide (PC) in a very short lapse of time. The sterile solution was compounded into a good manufacturing practice grade A clean room, filtered (0.2 µm) and filled into 10 mL type I glass, manually sealed with bromobutyl rubber stoppers. A novel HPLC-MS stability indicating method for pancuronium quantification and its degradation product was developed and validated. This fast, sensitive and straightforward method was used to study the stability of the formulation using a semi-predictive method, enabling a very fast attribution of a temporary shelf-life, which was confirmed by a classic prospective stability study. The production line and the analytical tools set-up were performed in six weeks and the semi-predictive stability study was conducted in 90 days, allowing us to predict a shelf life, which was successfully confirmed by prospective study. In conclusion, using innovative methods, we were able to rapidly overcome the shortage of a critical drug.

[Simultaneous determination of three quaternary ammonium muscle relaxants in blood by high performance liquid chromatography-tandem mass spectrometry].

Vecuronium, rocuronium, and pancuronium are widely used as non-depolarizing muscle relaxants. There have been occasional cases of allergic reactions and even death when using such muscle relaxants. Rapid determination of the concentration of these muscle relaxants in blood can provide valuable information for early clinical diagnosis. As quaternary ammonium compounds, these muscle relaxants are highly polar. Hence, they cannot be retained effectively on reversed-phase chromatographic columns with conventional mobile phases. These quaternary ammonium muscle relaxants are mainly separated by ion-pair chromatography. Using an ion-pairing reagent can help improve the retention capabilities of quaternary ammonium muscle relaxants. Nevertheless, the sensitivity of MS detection is significantly decreased because of ionic inhibition caused by the ion-pairing reagent in the mobile phase. Furthermore, ion-pairing reagents can pollute the MS system. A method based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the simultaneous determination of the three quaternary ammonium muscle relaxants in blood. The blood samples were diluted and subjected to high-speed centrifugation. The supernatant was purified on a Bond Elut AL-N solid phase extraction column and then filtered through a 0.45 µm microporous membrane. The quaternary ammonium muscle relaxants were separated on a ZIC-cHILIC analytical column (50 mm×2.1 mm, 3.0 µm) with gradient elution. Acetonitrile and 0.1% formic acid aqueous solution were used as mobile phases. The separated compounds were analyzed by tandem MS with an electrospray ionization (ESI) source in positive and multiple reaction monitoring (MRM) modes. The matrix effects of vecuronium, rocuronium, and pancuronium in blood were 88.1% to 95.4%. The calibration curves for vecuronium, rocuronium, and pancuronium showed good linear relationships in each range, and all correlation coefficients (R2) were > 0.996. The limits of detection of vecuronium, rocuronium, and pancuronium were 0.2-0.8 ng/mL, with the corresponding limits of quantification being 0.5-2.0 ng/mL. The recoveries of vecuronium, rocuronium, and pancuronium were 92.8% to 110.6%, with relative standard deviations (RSDs) of 3.2%-9.4%. This method is sensitive, accurate, and easy to operate, and it can be used to rapidly determine vecuronium, rocuronium, and pancuronium in blood.

Deep Tissue Incision Enhances Spinal Dorsal Horn Neuron Activity During Static Isometric Muscle Contraction in Rats.

Translational correlates to pain with activities after deep tissue injury have been rarely studied. We hypothesized that deep tissue incision causes greater activation of nociception-transmitting neurons evoked by muscle contraction. In vivo neuronal activity was recorded in 203 dorsal horn neurons (DHNs) from 97 rats after sham, skin-only, or skin + deep muscle incision. We evaluated DHN responses to static, isometric muscle contractions induced by direct electrical stimulation of the muscle. The effect of pancuronium on DHN response to contractions was also examined. Approximately 50% of DHNs with receptive fields in the hindpaw were excited during muscle contraction. One-second .5- and 1.0-g muscle contractions produced greater DHN activity after skin + deep muscle incision (median [interquartile range], 32 [5-39] impulses, P = .021; and 36 [26-46] impulses, P = .006, respectively) than after sham (6 [0-21] and 15 [8-32] impulses, respectively). Neuromuscular blockade with pancuronium inhibited the muscle contractions and DHN activation during electrical stimulation, demonstrating contraction-induced activation. The greater response of spinal DHNs to static muscle contraction after skin + deep muscle incision may model and inform mechanisms of dynamic pain after surgery. PERSPECTIVE: Completion of various activities is an important milestone for recovery and hospital discharge after surgery. Skin + deep muscle incision caused greater activation of nociception-transmitting DHNs evoked by muscle contraction compared with skin-only incision. This result suggests an important contribution of deep muscle injury to activity-evoked hyperalgesia after surgery.

Effect of anaesthetic and choice of neuromuscular blocker on vagal control of heart rate under laboratory animal experimental conditions.

Neuromuscular-blocking agents are commonly used in laboratory animal research settings. Due to actions of cholinergic receptors at locations other than the motor end-plate, these agents have a strong propensity to modulate autonomic outflow and may therefore not be desirable in studies examining autonomic function. This study aimed to compare the effect of two non-depolarizing neuromuscular-blocking agents, pancuronium and cisatracurium, on blood pressure, heart rate and non-invasive indices of autonomic function (heart rate variability, systolic blood pressure variability and baroreflex sensitivity) under two different types of anaesthesia in Lewis rats. Pancuronium produced a profound vagolytic response characterized by tachycardia, reduction in heart rate variability and baroreflex sensitivity under urethane anaesthesia, and with minimal effect under isoflurane anaesthesia. Conversely, cisatracurium produced no evidence of vagolytic action under either urethane or isoflurane anaesthesia. Therefore, for studies interested in examining autonomic function, particularly baroreflex or vagal function, neuromuscular blockade would be best achieved using cisatracurium.

Synergistic Activities of Abdominal Muscles Are Required for Efficient Micturition in Anesthetized Female Mice / 대한배뇨장애요실금학회지

PURPOSE: To characterize the electromyographic activity of abdominal striated muscles during micturition in urethane-anesthetized female mice, and to quantitatively evaluate the contribution of abdominal responses to efficient voiding. METHODS: Cystometric and multichannel electromyographic recordings were integrated to enable a comprehensive evaluation during micturition in urethane-anesthetized female mice. Four major abdominal muscle domains were evaluated: the external oblique, internal oblique, and superior and inferior rectus abdominis. To further characterize the functionality of the abdominal muscles, pancuronium bromide (25 μg/mL or 50 μg/mL, abdominal surface) was applied as a blocking agent of neuromuscular junctions. RESULTS: We observed a robust activation of the abdominal muscles during voiding, with a consistent onset/offset concomitant with the bladder pressure threshold. Pancuronium was effective, in a dose-dependent fashion, for partial and complete blockage of abdominal activity. Electromyographic discharges during voiding were significantly inhibited by applying pancuronium. Decreased cystometric parameters were recorded, including the peak pressure, pressure threshold, intercontractile interval, and voiding duration, suggesting that the voiding efficiency was significantly compromised by abdominal muscle relaxation. CONCLUSIONS: The relevance of the abdominal striated musculature for micturition has remained a topic of debate in human physiology. Although the study was performed on anesthetized mice, these results support the existence of synergistic abdominal electromyographic activity facilitating voiding in anesthetized mice. Further, our study presents a rodent model that can be used for future investigations into micturition-related abdominal activity.

Patient's death as a result of mistakenly injection of pancuronium.

Pancuronium is a typical non-depolarizing, curare-mimetic, very potent muscle relaxant. Besides application in anesthesiology and intensive care, it is used in execution as a part of lethal injection. In medico-legal practice, there are cases of using this substance in order to commit suicide or to deprive other people of their lives. Accidental pancuronium intoxications are very rare. The authors present such case ended in sudden death of hospitalized woman after mistakenly injection of the drug. 57-year-old female alcoholic was admitted to the Acute Poisoning Centre after ethylene glycol ingestion. During the fifth day of treatment the nurse by mistake, instead of furosemide, intravenously administered her pancuronium. Sudden respiratory and circulatory arrest occurred, so she was intubated and resuscitation with artificial ventilation were undertaken, however within 1 hour and 45 minutes the patient died. Due to the vague background of a sudden deterioration in the patient's condition, the case was brought for prosecution. The autopsy and histopathological studies did not reveal the cause of death, but undertaken chemico-toxicological examinations identified the presence of pancuronium in blood, liver and kidney (190 ng/ml, 70 ng/g and 125 ng/g, respectively). Chemico-toxicological analysis proved that the cause of death of the 57-year-old hospitalized woman was pancuronium intoxication due to evident medical error during drug administration. In our case the concentration of pancuronium in blood was in therapeutic range (200-600 ng/ml). However, even a therapeutic pancuronium dose administered to patient the breath of whom is not supported and monitored can be a threat to his life.

Association between levobupivacaine and pancuronium. Interference in neuromuscular transmission and blockade in rats.

PURPOSE: To evaluate the effects of levobupivacaine on neuromuscular transmission and neuromuscular blockade produced by pancuronium in vitro. METHODS: Thirty rats were distributed into groups (n = 5) according to the drug used alone or in combination: Group I - levobupivacaine (5 µg.mL-1); Group II - pancuronium (2 µg.mL-1); Group III - pancuronium (2 µg.mL-1) + levobupivacaine (5µg.mL-1). The following parameters were evaluated: 1) amplitude of diaphragmatic response to indirect stimulation, before and 60 minutes after the addition of levobupivacaine and pancuronium alone, and after the addition of levobupivacaine combined with pancuronium; 2) membrane potentials (MP) and miniature endplate potentials (MEPP). RESULTS: Levobupivacaine alone did not alter the amplitude of muscle response and MP. In preparations previoulsy exposed to levobupivacaine, the block with pancuronium was significantly denser (90.2 ± 15.2%), showing a significant difference (p=0.031) in comparison to the block produced by pancuronium alone (48.9% ± 9.8%). There was a decrease in the frequency and amplitude of MEPPs. CONCLUSION: Levobupivacaine potentiated the neuromuscular blockade produced by pancuronium, confirming a presynaptic action by a decrease in miniature endplate potentials.

Association between levobupivacaine and pancuronium. Interference in neuromuscular transmission and blockade in rats

ABSTRACT PURPOSE: To evaluate the effects of levobupivacaine on neuromuscular transmission and neuromuscular blockade produced by pancuronium in vitro. METHODS: Thirty rats were distributed into groups (n = 5) according to the drug used alone or in combination: Group I - levobupivacaine (5 µg.mL-1); Group II - pancuronium (2 µg.mL-1); Group III - pancuronium (2 µg.mL-1) + levobupivacaine (5µg.mL-1). The following parameters were evaluated: 1) amplitude of diaphragmatic response to indirect stimulation, before and 60 minutes after the addition of levobupivacaine and pancuronium alone, and after the addition of levobupivacaine combined with pancuronium; 2) membrane potentials (MP) and miniature endplate potentials (MEPP). RESULTS: Levobupivacaine alone did not alter the amplitude of muscle response and MP. In preparations previoulsy exposed to levobupivacaine, the block with pancuronium was significantly denser (90.2 ± 15.2%), showing a significant difference (p=0.031) in comparison to the block produced by pancuronium alone (48.9% ± 9.8%). There was a decrease in the frequency and amplitude of MEPPs. CONCLUSION: Levobupivacaine potentiated the neuromuscular blockade produced by pancuronium, confirming a presynaptic action by a decrease in miniature endplate potentials.

Pancuronium enhances isoflurane anesthesia in rats via inhibition of cerebral nicotinic acetylcholine receptors.

PURPOSE: This study was conducted to elucidate the mechanism of enhancement of volatile anesthetics by neuromuscular blocking agents in rats and to consider the relevance of this enhancement to clinical anesthesia. METHODS: Male Sprague-Dawley rats were used. After confirming a movement in response to tail clamping under 1.1 % isoflurane anesthesia, response was determined when the tail clamp was applied at several points after microinjection of pancuronium into the lateral ventricle. Arousal responses to microinjection of nicotine into the lateral ventricle were assessed with or without pretreatment with intraventricular pancuronium. The intravenous 50 % effective dose (ED50) and 95 % effective dose (ED95) for neuromuscular blockade with pancuronium administered in a cumulative fashion at 1.1 % isoflurane were calculated. RESULTS: Intraventricular pancuronium dose-dependently reduced the response to tail clamping, and the dose required to show immobilization of 50 % of rats (intraventricular ED50) was 1.62 µg/kg. Pretreatment with pancuronium at 6 µg/kg significantly reduced the effect of awakening by nicotine under isoflurane anesthesia (P = 0.044). The intravenous ED50 and ED95 for neuromuscular blockade were 63 µg/kg (90 % confidence interval [CI] 52-75 µg/kg) and 133 µg/kg (90 % CI 109-158 µg/kg), respectively. The ratio of intraventricular ED50 to intravenous ED50 was 0.026. CONCLUSION: Pancuronium microinjection into the lateral ventricle dose-dependently enhances the depth of isoflurane anesthesia, which might be caused by inhibition of neuronal nicotinic acetylcholine receptor transmission in the cerebrum. Intravenous injection of pancuronium at high doses might increase the cerebrospinal concentration to a level at which an effect can be observed.

Interrupted (self -)medication with pancuronium(bromide) and fatal outcome.

Pancuronium(bromide) is used because of its relaxing effect on striated muscles and usually requires artificial respiration. A 52-year-old woman suffered from long-standing "generalized dystonia", which had become resistant to conventional therapy. Therefore, an anesthetist established a permanent medication scheme with pancuronium using a PCA pump. This pump had been controlled by the patient herself ensuring an acceptable quality of life with broad personal autonomy. Finally, the woman was found dead in her flat by a member of a home nursing service. The infusion hose showed a fixed knot and further blocking by a clamp. The autopsy findings were non-specific, except for the presence of opioid tablets in the colon. Toxicological analyses showed 72ng/ml pancuronium and 21 ng/ml oxycodone (therapeutic) in the femoral venous blood. The range of published pancuronium levels varies from approx. 80 to 2,000 ng/ml. Thus it had to be assumed that the pancuronium level was too low (72 ng/ml) so that symptoms of dystonia recurred. Based on extensive literature research, the described case can be qualified as unique. The therapy concept had been innovative, sufficient and effective for more than 10 years. It allowed the patient to enjoy a maximum of autonomy. Ultimately, death was due to the blocked pancuronium infusion. The relatively low pancuronium level had provoked the dystonia to return with generalized spasms also involving the respiratory muscles resulting in respiratory arrest. During the police investigations, two previous suicide attempts came to light.

Modulation of medial geniculate nucleus neuronal activity by electrical stimulation of the nucleus accumbens.

Dysfunctional sensory gating has been proposed to result in the generation of phantom perceptions. In agreement, it has been recently suggested that tinnitus, a phantom perception of sound commonly associated with hearing loss, is the result of a breakdown of circuitry involving the limbic system and the medial geniculate nucleus (MGN) of the thalamus. In humans with tinnitus, structural changes and abnormal activity have been found to occur in the auditory pathway as well as parts of the limbic system such as the nucleus accumbens (NAc). However, at present, no studies have been conducted on the influence of the NAc on the MGN. We investigated the functional connectivity between the NAc and MGN single neurons. Bipolar electrical stimulation was delivered to the NAc while recording single neuron activity in MGN in anesthetized Wistar rats. Histological analysis was used to confirm placement of electrodes. NAc electrical stimulation generally decreased spontaneous firing rates in MGN neurons and, in a limited number of neurons, caused an increase in firing rate. This suggests that NAc can modulate the activity of auditory neurons in the MGN and may play a role in the development of tinnitus.

Effect of ropivacaine combined with pancuronium on neuromuscular transmission and effectiveness of neostigmine and 4-aminopyridine for blockade reversal: experimental study / Efeito da associação ropivacaina-pancurônio na transmissão neuromuscular e eficácia da neostigmine e 4-aminopiridina na reversão do bloqueio: estudo experimental / Efecto de la asociación ropivacaína-pancuronio en la transmisión neuromuscular. Eficacia de la neostigmina y 4-aminopiridina en la reversión del bloqueo. Estudio experimental

BACKGROUND AND OBJECTIVES: The local anesthetic effects on neuromuscular junction and its influence on blockade produced by nondepolarizing neuromuscular blockers are still under-investigated; however, this interaction has been described in experimental studies and in humans. The aim of this study was to evaluate in vitro the interaction between ropivacaine and pancuronium, the influence on transmission and neuromuscular blockade, and the effectiveness of neostigmine and 4-aminopyridine to reverse the blockade. METHODS: Rats were divided into groups (n = 5) according to the study drug: ropivacaine (5 µg mL-1); pancuronium (2 µg mL-1); ropivacaine + pancuronium. Neostigmine and 4-aminopyridine were used at concentrations of 2 µg mL-1 and 20 µg mL-1, respectively. The effects of ropivacaine on membrane potential and miniature endplate potential, the amplitude of diaphragm responses before and 60 min after the addition of ropivacaine (degree of neuromuscular blockade with pancuronium and with the association of pancuronium-ropivacaine), and the effectiveness of neostigmine and 4-aminopyridine on neuromuscular block reversal were evaluated. RESULTS: Ropivacaine did not alter the amplitude of muscle response (the membrane potential), but decreased the frequency and amplitude of the miniature endplate potential. Pancuronium blockade was potentiated by ropivacaine, and partially and fully reversed by neostigmine and 4-aminopyridine, respectively. CONCLUSIONS: Ropivacaine increased the neuromuscular block produced by pancuronium. The complete antagonism with 4-aminopyridine suggests presynaptic action of ropivacaine. .

JUSTIFICATIVA E OBJETIVOS: Os efeitos dos anestésicos locais na junção neuromuscular e sua influência no bloqueio produzido por bloqueadores neuromusculares não-despolarizantes é ainda alvo de pouca investigação, no entanto esta interação tem sido descrita em trabalhos experimentais e em humanos. O objetivo deste estudo foi avaliar in vitro, a interação da ropivacaína com o pancurônio, a influência na transmissão e bloqueio neuromuscular e a efetividade da neostigmina e 4-aminopiridina na reversão do bloqueio. MÉTODO: Ratos foram distribuídos em grupos (n = 5) de acordo com o fármaco estudado: ropivacaína (5 µg mL-1); pancurônio (2 µg mL-1); ropivacaína + pancurônio. A neostigmina e a 4-aminopiridina foram usadas nas concentrações de 2 µg mL-1 e 20 µg.mL-1, respectivamente. Avaliou-se: 1) efeitos da ropivacaína sobre o potencial de membrana e potenciais de placa terminal em miniatura; 2) a amplitude das respostas do diafragma antes e 60 minutos após a adição da ropivacaína; o grau de bloqueio neuromuscular com o pancurônio e com a associação pancurônio - ropivacaína; 3) a efetividade da neostigmina e 4-aminopiridina na reversão do bloqueio neuromuscular. RESULTADOS: A ropivacaína não alterou a amplitude das respostas musculares, os potenciais de membrana, mas diminuiu a frequência e a amplitude dos potenciais de placa terminal em miniatura. O bloqueio produzido pelo pancurônio foi potencializado pela ropivacaína, e parcial e totalmente revertido pela neostigmina e 4-aminopiridina, respectivamente. CONCLUSÕES: A ropivacaína potencializou o bloqueio neuromuscular produzido pelo pancurônio. O antagonismo completo com a 4-aminopiridina sugere ação pré-sináptica da ropivacaína. .

JUSTIFICACIÓN Y OBJETIVOS: Los efectos de los anestésicos locales en la unión neuromuscular y su influencia en el bloqueo producido por bloqueantes neuromusculares no-despolarizantes todavía son poco investigados, sin embargo, esta interacción ha sido descrita en trabajos experimentales y en seres humanos. El objetivo de este estudio fue evaluar in vitro la interacción de la ropivacaína con el pancuronio, la influencia en la transmisión y bloqueo neuromuscular y la efectividad de la neostigmina y 4-aminopiridina en la reversión del bloqueo. MÉTODO: Unos ratones fueron distribuidos en grupos (n = 5) de acuerdo con el fármaco estudiado: ropivacaína (5 µg/ml-1); pancuronio (2 µg/ml-1); ropivacaína + pancuronio. La neostigmina y la 4-aminopiridina fueron usadas en concentraciones de 2 µg/ml-1 y 20 µg/ml-1, respectivamente. Evaluamos: 1) efectos de la ropivacaína sobre el potencial de membrana y potenciales de placa terminal en miniatura; 2) la amplitud de las respuestas del diafragma antes y 60 min después de la adición de la ropivacaína; el grado de bloqueo neuromuscular con el pancuronio y con la asociación pancuronio-ropivacaína; 3) la efectividad de la neostigmina y 4-aminopiridina en la reversión del bloqueo neuromuscular. RESULTADOS: La ropivacaína no alteró la amplitud de las respuestas musculares, los potenciales de membrana, pero disminuyó la frecuencia y la amplitud de los potenciales de placa terminal en miniatura. El bloqueo producido por el pancuronio fue potenciado por la ropivacaína, y parcial y totalmente revertido por la neostigmina y 4-aminopiridina, respectivamente. CONCLUSIONES: La ropivacaína potenció el bloqueo neuromuscular producido por el pancuronio. El antagonismo completo con la 4-aminopiridina muestra una acción presináptica de la ropivacaína. .

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.

Volume guarantee ventilation during surgical closure of patent ductus arteriosus.

BACKGROUND: Surgical closure of patent ductus arteriosus (PDA) is associated with adverse outcomes. Surgical exposure requires retraction of the lung, resulting in decreased aeration and compliance. Optimal respiratory support for PDA surgery is unknown. Experience with volume guarantee (VG) ventilation at our institution led us to hypothesize that surgery would be better tolerated with automatic adjustment of pressure by VG to maintain tidal volume (VT) during retraction. OBJECTIVE: The objective of this study was to describe ventilator support, VT, and oxygenation of infants supported with VG during PDA surgery. DESIGN/METHODS: Ventilator variables, oxygen saturation, and heart rate were recorded during PDA surgery in a convenience sample of infants during PDA closure on VG. Pressure limit increased 11% and set VT was 26% lower during lung retraction. Fentanyl and pancuronium/vecuronium were used for anesthesia/muscle relaxation. Longitudinal data were analyzed by analysis of variance for repeated measures. RESULTS: Seven infants, 25.4 ± 1.5 weeks and 723 ± 141 g, underwent closure of PDA on VG at a mean age 29.9 days. No air leak, bradycardia, or death occurred. Target VT was maintained with a modest increase in inflation pressure. Oxygenation remained adequate. CONCLUSIONS: VG avoided hypoxemia and maintained adequate VT with only a modest increase in peak inflation pressure and thus may be a useful mode during PDA surgery.

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.

Comparative pharmacodynamics of pancuronium, cisatracurium, and CW002 in rabbits.

Pancuronium is a long-duration neuromuscular blocking drug (NMBD) that has been used in anesthetized rabbits at 0.1 mg/kg. However, there are limited data regarding the time course for recovery from this dose either spontaneously or with pharmacologic reversal. Here we defined the potency, onset, and recovery characteristics for the intermediate-duration NMBD cisatracurium and CW002 (a novel cysteine-inactivated molecule) in the rabbit, and test the hypothesis that these drugs may be alternatives to 0.1 mg/kg pancuronium for survival procedures. New Zealand white rabbits anesthetized with isoflurane were studied in a cross-over design. Potencies of cisatracurium and CW002 were defined as the effective dose for 95% depression of evoked muscle twitch (ED95). Responses to 3×ED95 were used to define onset (time to maximal effect), recovery index (RI; time from 25% to 75% recovery of twitch), and duration (time to complete recovery). Responses to all drugs were determined with and without reversal by neostigmine-glycopyrrolate or L-cysteine. CW002 was 4-fold more potent than was cisatracurium, but their onset, RI, and duration were similar. Pancuronium had similar onset and RI but longer duration, compared with cisatracurium and CW002. Reversal shortened the recovery index and duration for all 3 drugs. At 3×ED95, cisatracurium and CW002 had the same onset as did standard-dose pancuronium, but durations were shorter and more predictable. In addition, CW002 can be reversed without the potential side effects of cholinergic manipulation. We conclude that cisatracurium and CW002 are viable alternatives to pancuronium for survival studies in rabbits.