Train-of-four guard-controlled sugammadex reversal in patients with multiple sclerosis.

OBJECTIVE: Multiple sclerosis (MS) is a chronic inflammatory and demyelinating autoimmune disease of the central nervous system. It is known that the disease, which is manifested by a wide variety of symptoms, may exacerbate after anesthesia and show different responses to muscle relaxants in the normal population. It is planned to measure train-of-four (TOF) values of MS patients to be operated under general anesthesia before sugammadex application. MATERIALS AND METHODS: With the approval of the local ethics committee of the University of Health Sciences Bagcilar Training and Research Hospital and with written consents of participants, we anesthetized ten patients (from April 2014 to March 2017) with MS and ten American Society of Anesthesiologists I-III patients without MS. Neuromuscular conduction was assessed by the acceleromyometric method using a TOF-Guard apparatus (Organon, Holland). The patients were extubated after recovery of TOF higher than 0.9. The primary efficacy variable was the time from the start of administration of sugammadex to recovery of the TOF ratio to 0.9. RESULTS: The demographic characteristics of both groups, the type and duration of surgery and anesthesia applied, and the temperature of the operation room were similar. Similar characteristics of both groups were of concern for postoperative residual paralysis, and therefore we did not notice any difference between time to TOF> 90/s for both groups. CONCLUSION: Sugammadex and TOF patients will increase patient safety in general anesthesia practice.

Reversal of Vecuronium-induced Neuromuscular Blockade with Low-dose Sugammadex at Train-of-four Count of Four: A Randomized Controlled Trial.

BACKGROUND: Rocuronium-induced neuromuscular block that spontaneously recovered to a train-of-four count of four can be reversed with sugammadex 0.5 or 1.0 mg/kg. We investigated whether these doses of sugammadex can also reverse vecuronium at a similar level of block. METHODS: Sixty-five patients were randomly assigned, and 64 were analyzed in this controlled, superiority study. Participants received general anesthesia with propofol, sevoflurane, fentanyl, and vecuronium. Measurement of neuromuscular function was performed with acceleromyography (TOF-Watch-SX, Organon Teknika B.V., The Netherlands ). Once the block recovered spontaneously to four twitches in response to train-of-four stimulation, patients were randomly assigned to receive sugammadex 0.5, 1.0, or 2.0 mg/kg; neostigmine 0.05 mg/kg; or placebo. Time from study drug injection to normalized train-of-four ratio 0.9 and the incidence of incomplete reversal within 30 min were the primary outcome variables. Secondary outcome was the incidence of reparalysis (normalized train-of-four ratio less than 0.9). RESULTS: Sugammadex, in doses of 1.0 and 2.0 mg/kg, reversed a threshold train-of-four count of four to normalized train-of-four ratio of 0.9 or higher in all patients in 4.4 ± 2.3 min (mean ± SD) and 2.6 ± 1.6 min, respectively. Sugammadex 0.5 mg/kg reversed the block in 6.8 ± 4.1 min in 70% of patients (P < 0.0001 vs. 1.0 and 2.0 mg/kg), whereas neostigmine produced reversal in 11.3 ± 9.7 min in 77% of patients (P > 0.05 vs. sugammadex 0.5 mg/kg). The overall frequency of reparalysis was 18.7%, but this incidence varied from group to group. CONCLUSIONS: Sugammadex 1.0 mg/kg, unlike 0.5 mg/kg, properly reversed a threshold train-of-four count of four vecuronium-induced block but did not prevent reparalysis.

Adenosine A(2A) receptor antagonists are broad facilitators of antinicotinic neuromuscular blockade monitored either with 2 Hz train-of-four or 50 Hz tetanic stimuli.

1. The 2 Hz train-of-four ratio (TOF(ratio)) is used to monitor the degree of patient curarization. Using a rat phrenic nerve-hemidiaphragm preparation, we showed that antinicotinic agents, such as hexamethonium, d-tubocurarine and pancuronium, but not cisatracurium, decreased contractions produced by physiological nerve activity patterns (50 Hz) more efficiently than those caused by 2 Hz trains. Uncertainty about the usefulness of the TOF(ratio) to control safe recovery from curarization prompted us to investigate the muscarinic and adenosine neuromodulation of tetanic (50 Hz) fade induced by antinicotinic agents at concentrations that cause a 25% reduction in the TOF(ratio) (TOF(fade)). 2. Tetanic fade caused by d-tubocurarine (1.1 µmol/L), pancuronium (3 µmol/L) and hexamethonium (5.47 mmol/L) was attenuated by blocking presynaptic inhibitory muscarinic M(2) and adenosine A(1) receptors with methoctramine (1 µmol/L) and 1,3-dipropyl-8-cyclopentylxanthine (2.5 nmol/L), respectively. These compounds enhanced rather than decreased tetanic fade induced by cisatracurium (2.2 µmol/L), but they consistently attenuated cisatracurium-induced TOF(fade). The effect of the M(1) receptor antagonist pirenzepine (10 nmol/L) on fade produced by antinicotinic agents at 50 Hz was opposite to that observed with TOF stimulation. Blockade of adenosine A(2A) receptors with ZM 241385 (10 nmol/L) attenuated TOF(fade) caused by all antinicotinic drugs tested, with the exception of the 'pure' presynaptic nicotinic antagonist hexamethonium. ZM 241385 was the only compound tested in this series that facilitated recovery from tetanic fade produced by cisatracurium. 3. The data suggest that distinct antinicotinic relaxants interfere with fine-tuning neuromuscular adaptations to motor nerve stimulation patterns via activation of presynaptic muscarinic and adenosine receptors. These results support the use of A(2A) receptor antagonists together with atropine to facilitate recovery from antinicotinic neuromuscular blockade.

Presynaptic facilitatory adenosine A2A receptors mediate fade induced by neuromuscular relaxants that exhibit anticholinesterase activity.

1. Pancuronium, cisatracurium and vecuronium are antinicotinic agents that, in contrast with d-tubocurarine and hexamethonium, exhibit anticholinesterase activity. Pancuronium-, cisatracurium- and vecuronium-induced fade results from blockade of facilitatory nicotinic receptors on motor nerves, but fade produced by such agents also depends on the presynaptic activation of inhibitory muscarinic M2 receptors by acetylcholine released from motor nerve terminals and activation of inhibitory adenosine A1 receptors by adenosine released from motor nerves and muscles. The participation of presynaptic facilitatory A2A receptors in fade caused by pancuronium, cisatracurium and vecuronium has not yet been investigated. In the present study, we determined the effects of ZM241385, an antagonist of presynaptic facilitatory A2A receptors, on fade produced by these neuromuscular relaxants in the rat phrenic nerve-diaphragm (PND) preparation. 2. The muscles were stimulated indirectly at 75±3Hz to induce a sustained tetanizing muscular contraction. The lowest concentration at which each antinicotinic agent produced fade without modifying initial tetanic tension (presynaptic action) was determined. 3. d-Tubocurarine-induced fade occurred only at 55 nmol/L, a concentration that also reduced maximal tetanic tension (post-synaptic action). At 10 nmol/L, ZM 241385 alone did not produce fade, but it did attenuate pancuronium (0.32 µmol/L)-, cisatracurium (0.32 µmol/L)- and vecuronium (0.36 µmol/L)-induced fade. 4. The fade induced by the 'pure' antinicotinic agents d-tubocurarine (55 nmol/L) and hexamethonium (413 µmol/L) was not altered by 10 nmol/L ZM 241385, indicating that presynaptic adenosine A2A receptors play a significant role in the fade produced by antinicotinic agents when such agents have anticholinesterase activity.

Curare and pancuronium compared: effects on previously undepressed mammalian myoneural junctions.

Curare and pancuronium have multiple effects on previously undepressed rat diaphragm; these include depression of transmitter output and prolongation of the refractory period of prejunctional structures. The effect of curare on motor nerve terminals is greater than that of pancuronium. Both drugs depress postjunctional receptors; but curare, in addition, raises the threshold for the generation of muscle action potentials. In addition, these results raise questions about the validity of statistical methods used to calculate transmitter output.

Sugammadex, a selective reversal medication for preventing postoperative residual neuromuscular blockade.

BACKGROUND: Sugammadex is the first selective relaxant binding agent that has been studied for reversal of neuromuscular blockade induced by rocuronium and other steroidal non-depolarizing neuromuscular blocking agents (NMBAs). OBJECTIVES: To assess the efficacy and safety of sugammadex in reversing neuromuscular blockade induced by steroidal non-depolarizing NMBAs and in preventing postoperative residual neuromuscular blockade. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to August 2008), and EMBASE (1980 to August 2008). In addition, we handsearched reference lists of relevant articles and meeting abstracts. Furthermore, we contacted the medication's manufacturer for more information. SELECTION CRITERIA: All randomized controlled trials (RCTs) on adult patients (>/= 18 years old) in which sugammadex was compared with placebo or other medications, or in which different doses of sugammadex were compared with each other. We excluded non-randomized trials and studies on healthy volunteers. DATA COLLECTION AND ANALYSIS: We independently performed determination of trial inclusion, quality assessment, and data extraction. We applied standard meta-analytic techniques. MAIN RESULTS: We included18 RCTs (n = 1321 patients). Seven trials were published as full-text papers, and 11 trials only as meeting abstracts. All the included trials had adequate methods of randomization and allocation concealment. The results suggest that, compared with placebo or neostigmine, sugammadex can more rapidly reverse rocuronium-induced neuromuscular blockade regardless of the depth of the block. We identified 2, 4, and 16 mg/kg of sugammadex for reversal of rocuronium-induced neuromuscular blockade at T(2) reappearance , 1 to 2 post-tetanic counts, and 3 to 5 minutes after rocuronium, respectively. The number of trials are very limited regarding vecuronium and pancuronium. Serious adverse events occurred in < 1% of all patients who received the medication. There was no significant difference between sugammadex and placebo in terms of the prevalence of drug-related adverse events (RR 1.20, 95% CI 0.61 to 2.37; P = 0.59, I(2) = 0%, 5 RCTs). Also, no significant difference was found between sugammadex and neostigmine for adverse events (RR 0.98, 95% CI 0.48 to1.98; P = 0.95, I(2) = 43%, 3 RCTs). AUTHORS' CONCLUSIONS: Sugammadex was shown to be effective in reversing rocuronium-induced neuromuscular blockade. This review has found no evidence of a difference in the instance of unwanted effects between sugammadex, placebo or neostigmine. These results need to be confirmed by future trials on larger patient populations and with more focus on patient-related outcomes.

[Reversal from non-depolarising neuromuscular blockade in the postoperative period]. / Ocena przewodnictwa nerwowo-miesniowego po operacjach wykonywanych w znieczuleniu ogólnym z zastosowaniem niedepolaryzujacych srodków zwiotczajacych.

BACKGROUND: Postoperative residual curarisation (PORC) is a serious and underestimated problem and may occur even after relaxation with medium-acting non-depolarising agents. METHODS: One hundred adult patients, scheduled for elective surgical procedures, were enrolled in the study. Atracurium or cis-atracurium was used for relaxation. Neostigmine was administered for reversal at the end of surgery, at the discretion of the attending anaesthesiologist. Neuromuscular transmission was not monitored in the operating room. In the recovery room, the presence of residual block was assessed by a blinded investigator using accelerometry (TOF-Guard, Organon, Holland) immediately after arrival (T-A) and after 45 min (T-B). Those who received neostigmine were allocated to group I (49 patients), and those who did not were allocated to group II (51 patients). RESULTS: The mean duration of anaesthesia was 92 min in group I and 103 min in group II. The respective doses of atracurium were 78.2 and 72.0 mg; and of cis-atracurium--17.6 mg and 18.0 mg. Immediately after arrival, a TOF below 0.7 was detected in 26% of patients, and below 0.9 in 48% of patients. After forty-five minutes the TOF was still below 0.7 in one patient and below 0.9 in seven. The number of patients with residual block (TOF<0.9) did not differ statistically between those who received neostigmine and those who did not (3.92% and 10.2%, respectively). CONCLUSION: The clinical assessment of neuromuscular blockade reversal did not allow for detection of PORC. Neostigmine was not fully effective in reversal.

[Randomized, multicenter study of interaction between Org 9426 (rocuronium bromide) and anesthetic agents in Japanese population].

BACKGROUND: The purpose of this randomized, multi-center phase III trial was to investigate the influence of sevoflurane and propofol on the neuromuscular blocking effects and pharmacokinetic parameters of Org 9426 (rocuronium bromide) in Japanese population. METHODS: Thirty-nine adult Japanese patients participated in this randomized, multi-center study. Neuromuscular function was monitored continuously with TOF-Watch SX (Organon NV, Netherlands) after anesthetic induction with propofol. These subjects randomly received either 0.6 mg x kg(-1) or 0.9 mg x kg(-1) of rocuronium for endotracheal intubation. These two groups were further divided to two anesthetic regiments : sevoflurane group and propofol group. The difference in onset and recovery of rocuronium-induced neuromuscular block was statistically analyzed with two-way ANOVA. RESULTS: Mean duration for maximal block was 76 seconds and 66 seconds, respectively. The duration between Org 9426 administration and 25% recovery of first twitch response was significantly prolonged in patients given 0.9 mg x kg(-1) of Org 9426. Sevoflurane also significantly increased this duration. However, the serum concentration of Org 9426 was not statistically different between the four study groups. CONCLUSIONS: The duration of Org 9426-induced neuromuscular blockade was significantly increased under sevoflurane anesthesia compared to propofol anesthesia. This difference may be attributed to pharmacodynamic change.

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.

Vecuronium kinetics and dynamics in anesthetized infants and children.

Vecuronium kinetics and dynamics were determined in five infants (3 to 11 months old) and five children (1 to 5 years old) during anesthesia with 70% nitrous oxide and 0.9 MAC halothane. Vecuronium was infused intravenously at a rate of 2.5 micrograms/kg/min while twitch tension of the adductor pollicis muscle was recorded and venous blood samples were drawn for determination of vecuronium concentrations by mass spectrometry. The elimination t1/2 was determined by linear regression of the log postdistribution concentration-time data; these values and noncompartmental techniques were used to calculate total plasma clearance (Cl), volume of distribution at steady state (Vdss), and mean residence time. The steady-state plasma concentration resulting in 50% depression of twitch tension (Cpss50) was determined by an effect compartment and a sigmoid concentration vs. paralysis model. Vdss was larger in infants (357 +/- 70 ml/kg; mean +/- SD) than in children (204 +/- 116 ml/kg), and Cl was of the same order for infants and children (5.6 +/- 1.0 and 5.9 +/- 2.4 ml/kg/min). Mean residence time was longer in infants (66.3 +/- 22.9 minutes) than in children (34.3 +/- 8.0 minutes). Cpss50 was lower in infants (57 +/- 18 ng/ml) than in children (110 +/- 28 ng/ml). The quantity of vecuronium in the body at steady state at 50% depression of twitch tension (Vdss X Cpss50) was similar in infants and children (21.2 +/- 9.9 and 19.0 +/- 3.3 micrograms/kg). During comparable nitrous oxide-halothane anesthesia, age-related changes in Vdss, Cl, and Cpss50 were much like those found for d-tubocurarine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancuronium improves the neuromuscular transmission defect of human organophosphate intoxication.

Two patients with acute severe organophosphate intoxication showed (1) single evoked compound muscle action potentials (CMAP) with repetitive discharges and (2) prominent decremental responses of CMAP with 20 and 50 Hz supramaximal nerve stimulation. Following the intravenous injection of single small doses of pancuronium, marked improvement in these abnormalities occurred and persisted for several hours. We postulate that the physiologic improvement following low-dose pancuronium results from blockade of acetylcholine receptors, especially those located on the terminal axon responsible for antidromic backfiring.

Effects of pancuronium and hexamethonium on paraoxon-induced twitch potentiation and antidromic firing in rat phrenic nerve diaphragm preparations.

The actions of pancuronium, a selective antagonist of acetylcholine (ACh) at nicotinic cholinoceptors at motor endplates, and hexamethonium, a selective antagonist of ACh at nicotinic cholinoceptors in autonomic ganglia, have been studied in rat phrenic nerve diaphragm preparations. The effects on paraoxon-induced twitch potentiation and antidromic firing (ADF) in the phrenic nerve, were compared with the effects on normal twitch tension and intracellularly recorded miniature endplate potentials (m.e.p.ps) and endplate potentials (e.p.ps.) In preparations exposed to paraoxon, pancuronium was found to be approximately 10 times more effective in reducing the potentiated component of the twitch than the component which corresponded to the pre-paraoxon twitch. A similar result was obtained with hexamethonium. Pancuronium and hexamethonium, in concentrations which reduced paraoxon-induced twitch potentiation but had no effect on the twitch tension of preparations not treated with paraoxon, reduced paraoxon-induced ADF. The lowest concentrations of pancuronium and hexamethonium required for this also reduced the amplitude of m.e.p.ps and e.p.ps. Dithiothreitol, a disulphide bond reducing agent which reduces the affinity of ACh for nicotinic cholinoceptors, enhanced the potency of pancuronium 2 to 3 fold. The same also applied for hexamethonium. It is concluded that the experiments failed to provide evidence for an action of ACh on prejunctional nicotinic cholinoceptors of the ganglionic-type being involved in the initiation by paraoxon of twitch potentiation and ADF. Furthermore, the results obtained can be explained by pancuronium and hexamethonium reducing the action of ACh at the postjunctional membrane.

A comparison of the effects of pancuronium bromide and its monoquaternary analogue, ORG NC 45, on autonomic and somatic neurotransmission in the rat.

1 Potentiation by pancuronium of the effects of adrenergic nerve stimulation, previously shown in cardiovascular tissues, was also found in rat anococcygeus and vas deferens, in vitro or in vivo. 2 In the pithed rat, in the presence of pancuronium, pre-junctional alpha-adrenoceptor-mediated feedback inhibition of cardiac sympathetic transmission was uncovered at relatively low stimulation frequencies by phentolamine or yohimbine. 3 The effects of pancuronium and its mono-quaternary analogue Org NC 45 on autonomic and somatic neuromuscular transmission were compared, in the pithed rat. Org NC 45 was less potent than pancuronium at blocking somatic neuromuscular transmission by a factor of 2.1, at blocking cardiac, parasympathetic transmission by a factor of 538 and at potentiating sympathetic transmission by a factor of 33.

The prejunctional actions of some non-depolarizing blocking drugs.

1. Trains of end-plate potentials (e.p.p.s) have been recorded from the isolated tenuissimus of the cat. The muscle was paralyzed either by transversely cutting the muscle fibres or by non-depolarizing blocking drugs.2. The following parameters of transmitter synthesis, storage and release have been calculated: the quantal content of the first e.p.p. in the train, the size of the available store, fractional release, quantum size, and the rate of refilling of the available store.3. Tubocurarine and benzoquinonium depressed the rate of refilling of the available store causing its depletion at high rates of stimulation. This was offset by an increase in fractional release, which in the case of tubocurarine was sufficient for the quantal content of the first e.p.p. to be unchanged.4. Dimethyltubocurarine and pancuronium had a similar effect to tubocurarine on the rate of refilling of the store and depletion of the store at high rates of stimulation but did not increase fractional release. There was, therefore, a decrease in the quantal content of the first e.p.p.5. Lignocaine depressed the rate of refilling of the store and depleted the store at high rates of stimulation. Fractional release was also depressed.6. It is suggested that the non-depolarizing drugs have a weak local anaesthetic action retarding the influx of sodium into the nerve terminal which slows the rate of refilling of the store. This effect is due to the quaternary ammonium head. The presence of a phenolic group increases fractional release due either to an increased influx of calcium into the nerve terminal or to a potentiation of the actions of calcium.

Interaction of competitive antagonists: the anti-curare action of hexamethonium and other antagonists at the skeletal neuromuscular junction.

1. In the rat isolated diaphragm preparation hexamethonium and other low potency competitive antagonists of acetylcholine (ACh), including gallamine and hyoscine butylbromide, reverse block by the potent antagonists tubocurarine, pancuronium and alcuronium. 2. In the presence of tubocurarine, hexamethonium increases the amplitude of the end-plate potential without increasing the quantal content. It enhances the response to ACh applied iontophoretically to the end-plate but does not enhance the response to ACh applied in the bath. 3. The anti-curare effect of hexamethonium is abolished in the diaphragm of the rat, guinea-pig and mouse by inhibitors of acetylcholinesterase. The effect is not observed in the indirectly stimulated toad sartorius muscle. 4. The effect is explained if tubocurarine does not dissociate appreciably in the time taken for ACh to achieve high occupancy of receptors, so that a fraction of receptors is completely excluded from occupation by ACh. Equilibration with hexamethonium reduces the fraction excluded by tubocurarine and the transmitter now competes with hexamethonium for more receptors and produces a larger response. 5. On the basis of this explanation the half-time for dissociation of tubocurarine must be about 1 millisecond. It follows that tubocurarine does not act competitively with ACh at synapses when transmitter action is sufficiently brief, and that its binding to the receptor is probably diffusion-limited.

Intravenous pancuronium bromide for fetal neuromuscular blockade during intrauterine transfusion for red-cell alloimmunization.

Intravenous pancuronium bromide was administered into the umbilical cord by funipuncture to effect temporary fetal paralysis. Neuromuscular blockade was achieved in 12 fetuses undergoing a total of 34 intrauterine procedures for the treatment of severe red-cell alloimmunization. The same initial dose of 0.2 mg/kg fetal weight estimated by ultrasound was used in all cases, but anemic fetuses did not resume movement for prolonged periods. A relationship among fetal hematocrit, adjusted dose, and duration of paralysis was described by the equation: Duration (hours) = 5.24 + 10.30 adjusted dose (mg/kg) - 0.16 hematocrit (%) (R2 = 0.49; P less than .001). Intravenous pancuronium was found to be a safe and effective method for cessation of fetal movement during intrauterine procedures.

Neuronal peptide (enkephalin) receptors in the ear artery of the rabbit.

Methionine-enkephalin methylester (MEM) and leucine-enkephalin (LE) inhabit the vasoconstrictor responses of the rabbit ear artery to nerve stimulation by acting on a specific neuronal peptide (enkephalin)-receptor insensitive to opiate agonists. The tetrapeptide: H-Tyr-Gly-Phe-Leu-OCH3 is ineffective. This is the first instance of enkephalins acting in an organ devoid of receptors. In a new test for the analysis of opiate receptors, MEM (ID50=6.9 X 10(-9) M) was a potent inhibitor of transmission. The presence was shown of opiate receptors in the brain which were insensitive to high i.v. or intraventricular doses of enkephalins. It is concluded that enkephalins are not natural ligands to the opiate receptors, but that some of the receptors confuse these structures because of similar characteristics which determine the binding of both opiates and peptides.

Atracurium resistance in a critically Ill patient.

A previously healthy 25-year-old man with metastatic testicular teratocarcinoma became resistant to atracurium-induced neuromuscular blockade as evidenced by train-of-four (TOF) monitoring combined with clinical assessment. Subsequently he had an adequate response with a standard dosage of pancuronium. During the first 10 days of neuromuscular blockade, the atracurium requirements escalated from 0.31 to 1.7 mg/kg/hour, guided by TOF monitoring, movement, and spontaneous respirations. The infusion was discontinued but later reinstituted. Despite a total atracurium loading dose of 1.4 mg/kg followed by an infusion rate titrated to 1.7 mg/kg/hour, inadequate paralysis persisted. Atracurium was terminated and an intravenous infusion of pancuronium 0.10 mg/kg/hour was started. Over the next 3 days the pancuronium infusion was titrated down to a range of 0.04-0.06 mg/kg/hour, followed by a maintenance infusion of 0.01-0.05 mg/kg/hour for 5 days. A pharmacokinetic alteration, such as increased metabolism or elimination, may have caused the atracurium resistance.

Prolonged neuromuscular blockade in two critically ill patients treated with atracurium.

Recent literature suggests that the risk of prolonged neuromuscular blockade associated with atracurium compared with other nondepolarizing neuromuscular blocking agents may be minimal. Two patients experienced prolonged weakness associated with the administration of atracurium. Both received atracurium 0.5-0.7 mg/kg/hour in combination with methylprednisolone 500-600 mg/day. Electromyographic results and creatine kinase levels were suggestive of muscular weakness in both patients. Despite high-dose corticosteroid therapy, the electromyographic evidence supporting prolonged weakness did not suggest typical corticosteroid myopathy. Although some clinicians advocate routine administration of atracurium in critically ill patients due to the relative lack of reports of prolonged weakness, this may be premature. Although there are fewer reports of atracurium-associated prolonged weakness compared with pancuronium and vecuronium, the patients we describe suggest that it may occur.

Comparative evaluation of the neuromuscular and cardiovascular effects of pipecuronium, pancuronium, atracurium, and vecuronium under isoflurane anesthesia.

The neuromuscular and cardiovascular effects of intubating doses of pipecuronium 80 micrograms/kg, pancuronium 100 micrograms/kg, atracurium 500 micrograms/kg, and vecuronium 100 micrograms/kg were compared in 62 patients under isoflurane (end-tidal concentration = 0.5-1%) anesthesia. Pipecuronium, pancuronium, and vecuronium had no significant effect on systolic or diastolic blood pressure. In one patient the administration of atracurium resulted in significant hypotension. Heart rate was significantly increased only after the administration of pancuronium. The neuromuscular-blocking effect of pipecuronium and pancuronium appears to be twice as long as that of vecuronium and atracurium. Administration of neostigmine resulted in significantly faster recovery of muscle function in patients receiving vecuronium or atracurium. Although pipecuronium's neuromuscular-blocking effect is similar to that of pancuronium, its lack of cardiovascular effects more closely resembles that of vecuronium.