Optimal dose of neostigmine antagonizing cisatracurium-induced shallow neuromuscular block in elderly patients: a randomized control study.

BACKGROUND: Residual neuromuscular block after using neuromuscular blocking agents is a common and potentially harmful complication of general anesthesia. Neostigmine is a widely used antagonist, but its optimal dose for elderly patients is unclear. OBJECTIVES: To compare the optimal dosage and safety of neostigmine for reversing shallow residual block in elderly patients after cisatracurium-induced neuromuscular block. METHODS: A randomized controlled trial was conducted in 196 elderly patients undergoing non-cardiac surgery under general anesthesia with cisatracurium. Patients were assigned to receive either no neostigmine (control group) or neostigmine at 20 µg/kg, 40 µg/kg or 50 µg/kg when train-of-four (TOF) ratio reached 0.2 at the end of surgery. The primary outcome was the time to reach TOF ratio of 0.9 after administration. Secondary outcomes included TOF ratio at 10 min after administration, postoperative nausea and vomiting, postoperative cognitive impairment and post-anesthesia care unit (PACU) stay time. RESULTS: The time to reach TOF ratio of 0.9 in the 20 µg/kg, 40 µg/kg and 50 µg/kg groups was significantly shorter than the control group (H = 104.257, P < 0.01), and the time of 40 µg/kg group and 50 µg/kg group was significantly shorter than the 20 µg/kg group (P < 0.001). There was no significant difference between 40 µg/kg and 50 µg/kg groups (P = 0.249). The TOF ratio at 10 min after administration showed similar results. There were no significant differences among groups in postoperative nausea and vomiting, postoperative cognitive impairment or post-operation hospital stay. CONCLUSIONS: Timely use of neostigmine after general anesthesia in elderly patients can significantly shorten time of TOF value reaching 0.9, among which 40 µg/kg dosage may be a more optimized choice. TRIAL REGISTRATION: this study was registered on chictr.org.cn (ChiCTR2100054685, 24/12/2021).

Novel Insights on MRGPRX2-Mediated Hypersensitivity to Neuromuscular Blocking Agents And Fluoroquinolones.

Neuromuscular blocking agents (NMBAs) like atracurium and rocuronium as well as fluoroquinolones (FQs) cause mast cell-mediated anaphylaxis by activating Mas-related G protein-coupled receptor X2 (MRGPRX2), but many questions remain unanswered. Here, we address three of them, namely whether primary human mast cells show similar activation by these drugs as murine mast cells and mast cell lines, how sugammadex protects from atracurium-induced MRGPRX2-mediated mast cell activation, and why some but not all patients treated with rocuronium develop anaphylaxis. We used peripheral blood-derived cultured mast cells from healthy donors and patients, assessed mast cell activation and degranulation by quantifying intracellular calcium and CD63 expression, respectively, and made use of MRGPRX2-silencing, via electroporation with Dicer-substrate small interfering RNAs, and single cell flow cytometric analyses. Atracurium, ciprofloxacin, and levofloxacin activated and degranulated primary human mast cells, but only MRGPRX2-positive and not MRGPRX2-negative or -silenced mast cells. Sugammadex attenuated the atracurium-induced and MRGPRX2-mediated activation and degranulation of human mast cells by reducing free atracurium levels. The mast cells of patients with IgE-independent anaphylaxis to rocuronium were similar, in their MRGPRX2 expression and function, to those of patients with IgE-mediated anaphylaxis. These findings further improve our understanding of the role and relevance of MRGPRX2-driven mast cell activation in anaphylactic reactions to NMBAs and FQs and may help to improve their prediction, prevention, and treatment.

An investigation of non-depolarizing muscle relaxants on embryonic development in cultured rat embryos.

BACKGROUND AND OBJECTIVE: We have investigated the toxic and teratogenic effects of certain non-depolarizing muscle relaxants on embryonic development in cultured rat embryos. METHODS: Rat embryos of 9.5 days were explanted and cultured in vitro for 48 h in rat serum. Whole rat serum was used as a culture medium for the control group while different concentrations of atracurium, cis-atracurium, rocuronium and mivacurium were added to rat serum for the experimental groups. Dose-dependent effects of these agents on embryonic developmental parameters were compared using morphological and biochemical methods. Each embryo was evaluated for the presence of any malformations. RESULTS: When compared to the control embryos, the muscle relaxants significantly decreased all growth and developmental parameters dose dependently with an increase in overall dismorphology. Among these malformations, maxillary deformity was most frequently observed. These effects were observed in much lower doses with atracurium and cis-atracurium compared to those with rocuronium and mivacurium. CONCLUSIONS: Our results suggest that non-depolarizing muscle relaxants cause dose-dependent toxicity on rat embryos at concentrations much greater than those in clinical practice. Although, these agents seems to have a low potential for causing developmental toxicity during organogenesis, because of the lower toxic effects observed with rocuronium and mivacurium, these agents may be preferred when recurrent administrations are necessary for parturients.

Weal and flare responses to intradermal rocuronium and cisatracurium in humans.

Thirty volunteers underwent intradermal skin testing with increasing concentrations of rocuronium and cisatracurium to evaluate weal and flare responses, and whether either agent would cause mast cell degranulation and sensitization upon re-exposure. We found that intradermal injection of rocuronium and cisatracurium at concentrations > 10(-4) M resulted in positive weal (>8 mm) responses, and positive flare responses at > 10(-4) and > 10(-5) M respectively. Only cisatracurium caused mild to moderate mast cell degranulation, and neither drug caused significant in vitro histamine release from whole blood collected from study subjects 4 weeks after skin testing. Skin testing with rocuronium and cisatracurium should be performed at concentrations < 10(-4) and < 10(-5) M respectively to avoid false-positive responses. The ability of these agents to produce positive weal and flare responses at relatively low concentrations may explain the high incidence of potential reactions reported.

Activation of brain acetylcholine receptors by neuromuscular blocking drugs. A possible mechanism of neurotoxicity.

BACKGROUND: Neuromuscular blocking drugs cause excitement and seizures when introduced into the central nervous system. We examined the possibility that these drugs produce paradoxical activation of acetylcholine or glutamate receptors, the chief types of brain receptors involved in excitatory neurotransmission. METHODS: Because activation of central glutamate or acetylcholine receptors causes calcium influx into postsynaptic neurons, we measured intracellular calcium concentration ([Ca2+]i) as an index of receptor activation. Changes in [Ca2+]i were compared in brain slices exposed to neuromuscular blocking drugs or acetylcholine and glutamate receptor agonists. [Ca2+]i was measured with the fluorescent dye fura-2. RESULTS: Pancuronium and vecuronium caused sustained increases in [Ca2+]i in approximately the same potency ratio as for seizure activity in vivo (concentrations at which the increase in [Ca2+]i was 95% of maximal: 100 and 400 microM, respectively). Atracurium and laudanosine did not increase [Ca2+]i in cortical slices. Increases in [Ca2+]i caused by both pancuronium and vecuronium were prevented by the non-subtype-specific nicotinic acetylcholine receptor antagonist D-tubocurarine and were reduced 44-73% by atropine. Blockade of glutamate receptors or voltage-gated calcium or sodium channels had no effect on calcium influx. CONCLUSIONS: The results suggest that the acute excitement and seizures caused by introduction of pancuronium and vecuronium into the central nervous system is due to accumulation of cytosolic calcium caused by sustained activation of acetylcholine receptor ion channels.

Influence of incubated atracurium on rat liver function.

Degradation of atracurium by Hofmann elimination and ester hydrolysis depends mainly on pH and temperature and is said to be independent of liver and kidney function. Consequently atracurium is used widely in patients with liver failure. However, there is evidence that incubation of atracurium at 37 degrees C and pH 8 leads to leakage of LDH from hepatocyte cell cultures. We have tested the hepatotoxic effects of incubated atracurium in an isolated perfused rat liver model. After equilibration, atracurium 2010 mumol ml-1 (preincubated at pH 8 and 37 degrees C for 120 min) was administered over a period of 10 min followed by perfusion of Krebs-Henseleit bicarbonate buffer for 60 min. We found that incubation resulted in considerable degradation of atracurium and formation of laudanosine. Administration of incubated atracurium did not produce either biochemical or morphological damage to liver cells, but caused considerable increase in bile flow. We conclude that administration of preincubated atracurium did not produce impairment of liver cell function. The increase in bile flow could be beneficial if it occurs clinically.

Developmental toxicity of nondepolarizing muscle relaxants in cultured rat embryos.

Evidence of developmental toxicity of clinically used nondepolarizing muscle relaxants was sought in rat embryos grown in culture. Embryos were explanted at 8 AM on day 9 of gestation (presomite stage, plug day = day 0), and were cultured in rotating bottles with medium containing various concentrations of d-tubocurarine, pancuronium, atracurium, and vecuronium. At 10 AM on day 11 of gestation (forelimb bud stage), culture was terminated and embryos were examined for general morphology. Treatment with tested agents resulted in dose-dependent developmental toxicity; namely, growth retardation seen as decreased crown-rump length, decreased number of somite pairs, and morphologic abnormalities. However, the concentrations that caused toxicity were at least 30-fold greater than serum concentrations clinically achieved in the mother. We conclude that these muscle relaxants have a low potential for causing developmental toxicity during organogenesis.

Recovery of costal and crural diaphragmatic contractility from partial paralysis.

Since the two muscles (costal and crural) that constitute the diaphragm are separate and histologically different, their individual recovery pattern from neuromuscular blockade also may be different. Therefore, we studied the recovery of force and shortening in the in vivo diaphragm from atracurium-induced neuromuscular blockade in seven pentobarbital anesthetized dogs to assess segmental differences. Transdiaphragmatic pressure (Pdi), shortening of costal and crural segments, integrated electromyogram (EMG), and tidal volume (VT) were measured during spontaneous breathing. After atracurium had reduced VT to 30% of control, breathing parameters were followed until recovered to 90% of control values. In addition, force-frequency curves generated by supramaximal tetanic stimuli of the phrenic nerve were measured. Recovery times for tidal Pdi, tidal EMG, tidal shortening, low-frequency shortening, and twitch Pdi were twice as fast as for VT (40 +/- 4 min), reflecting a slower rate of recovery of accessory inspiratory muscles. High-frequency recovery was typically slower than that of VT. During tidal breathing and tetanic stimulation, costal and crural shortening recovered simultaneously. On the other hand, comparison between costal and crural by analysis of pressure-shortening relationships showed a segmental difference (crural shortened 30% more than costal at the same Pdi), which implied reduced afterload on the crural segment. However, since shortening and pressure were linearly related during paralysis and recovery, measurements of Pdi alone can accurately reflect changes in contractile mass when heterogeneity and afterload are controlled.

Reactivity and toxicity of atracurium and its metabolites in vitro.

Cytotoxicity of atracurium and of its metabolites was tested in vitro. Exposure of isolated rat hepatocytes to atracurium produced cellular damage evidenced by extrusion of an intracellular enzyme, lactate dehydrogenase (LDH), into the incubation medium. Leakage of LDH was directly related to the concentration of atracurium in the medium (250 to 800 microM). If the spontaneous degradation of atracurium (presumably via Hofmann elimination) was first carried out in vitro and the degradation products subsequently added to the isolated hepatocytes, the leakage of LDH was also dose-dependent but larger than that observed after the addition of the parent drug. When l-cysteine was admixed to the products of the spontaneous degradation of atracurium prior to their addition to the liver cells, no leakage of LDH was observed. The results are compatible with the working hypothesis that atracurium itself and, even more so, acrylates formed in Hofmann elimination of atracurium, are reactive toward nucleophiles and damage the cells by alkylating nucleophiles present in cellular membranes. Antecedent covalent binding of acrylates to the nucleophile cysteine, i.e., the formation of acrylate-cysteine adducts, saturated the reactive capacity of acrylates for nucleophiles and thus prevented the reactive metabolites from alkylating the endogenous nucleophiles. Possible clinical consequences resulting from in vivo generation of reactive metabolites are not clear at the present time but are projected to be related to (a) the dose of atracurium administered, (b) the amount of acrylates generated, (c) the functional importance of the endogenous nucleophiles alkylated, and (d) the pathway and the speed of detoxification of atracurium and its metabolites.

[Atracurium and vecuronium: interaction with three orally administered calcium antagonists in animal experiments]. / Atracurium und Vecuronium: Wechselwirkungen mit drei oral verabreichten Calciumantagonisten im Tierexperiment.

Interactions between calcium antagonists (CA) and muscle relaxants have been reported however due to the extremely high dosages of CA used in these studies, the clinical relevance of the observed interactions has been questioned. In order to simulate clinical practice--which entails long-term oral treatment and significant reductions in systolic blood pressure--CA were administered to rats orally (by gavage) for 8 days at a dosage that induced a systolic blood pressure decrease of not more than 25 +/- 5 mmHg. Ten groups of six male Sprague-Dawley rats each, body weight (BW) 313 +/- 23 g, were subjected to oral administration of three different CA: nitrendipine (1 mg/kg BW), nisoldipine (1 mg/kg BW), and diltiazem (100 mg/kg BW) or their solvents (control) three times daily by gavage for a period of 8 days. One hour after the last dose of drug or solvent, the rats were anesthetized (pentobarbital 60 mg/kg BW) and mechanically ventilated via tracheostomy. Monitoring included rectal temperature, carotid artery pressure, central venous pressure, heart rate, blood gases, and end-tidal CO2. Evoked train-of-four (T4) twitch tension of the right tibialis anterior muscle was recorded continuously. After equilibration of vital signs and muscle twitch tension, vecuronium (150 micrograms/kg BW) or atracurium (500 micrograms/kg BW) was injected into the internal jugular vein four times at 5-min intervals after twitch tension had totally recovered and T4 fade had disappeared. Twitch depression, duration 90, and onset time of neuromuscular block in CA-pretreated animals were compared to control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of atracurium toxicity in isolated rat hepatocytes by inhibition of its hydrolytic degradation pathway.

This study tested the hypothesis that the esters of acrylic acid might be responsible for the previously observed cytotoxic effect of atracurium. Rats were pretreated with triorthotolyl phosphate (TOTP), an inhibitor of the hydrolytic degradation of atracurium. Because hydrolysis of acrylates is also inhibited by TOTP and because the hydrolysis represents a detoxification pathway for these esters, we postulated that the leak of lactic dehydrogenase (LDH) induced by atracurium would be enhanced in hepatocytes harvested from rats pretreated with TOTP. Hepatocytes isolated from rats previously treated with TOTP (25 or 50 mg/kg intraperitoneally, 20 hr before induced death) were incubated for 4 hr in the absence of muscle relaxants or in the presence of either atracurium (0.008-0.8 mM) or metocurine (0.015-0.85 mM). Atracurium produced a concentration-dependent leakage of LDH. The leakage out of cells obtained from TOTP-pretreated rats was greater than was the leakage out of hepatocytes harvested from animals pretreated only with corn oil (a vehicle for TOTP). Metocurine did not produce a leak of LDH. It is concluded that the LDH leakage was produced by ester-type products of atracurium degradation. Acrylates appear to be the toxic agent.

Post-operative morbidity associated with the use of atracurium and vecuronium in day-case laparoscopy.

Patients were randomly allocated to receive either vecuronium or atracurium as the sole muscle relaxant for day-case gynaecological laparoscopy to determine if either agent was superior with respect to post-operative morbidity during the 48 h after operation. Intubating conditions and cardiovascular stability were similar in both groups. Post-operative morbidity prior to discharge was also similar except for a significantly higher incidence of abdominal pain in the vecuronium group. There was no statistical difference in specific morbidity during the 48 h after laparoscopy, but a greater number of patients in the vecuronium group was able to resume normal activity 24 h after laparoscopy. Both agents are very suitable for day-case laparoscopies and other short surgical procedures.

Comparative toxicity of atracurium and metocurine in isolated rat hepatocytes.

Primary cultures of liver cells isolated from seven rats were used to study the possible toxicity of atracurium and metocurine. The muscle relaxants were separately added to the culture medium and the cells then incubated for 4 hr. The amount of lactic dehydrogenase (LDH) that leaked into the culture medium was determined at the end of incubation. The customary assumption was made that the exudation of LDH reflects the toxic effects of the relaxants. In untreated dishes, approximately 11% of the total intracellular LDH leaked out during the incubation. The net leakage of LDH produced by the relaxants was obtained by subtracting this amount from the LDH activity determined in the media of dishes with the relaxants added. On this basis, metocurine, in concentrations of 12-850 X 10(-6)M, did not cause a net leak of LDH. On the other hand, atracurium, in similar molar concentrations, caused a statistically significant and concentration-dependent leak of LDH that, at its maximum, amounted to more than one half of the intracellular LDH. The results are interpreted in terms of damage to cellular membranes produced by atracurium or its metabolites. Although the exact biochemical process was not identified, we hypothesize that acrylates--produced by Hofmann elimination from atracurium--might be the likely toxic species.