Onset and duration of action of escalating doses of atracurium in anesthetized healthy goats

OBJECTIVE

The aim of this study was to describe the onset and duration of action of escalating doses of atracurium in healthy, anesthetized goats.

STUDY DESIGN

Randomized, blinded, triple crossover study. Animals A total of eight (five males and three females) healthy goats weighing 42.7-123.5 kg and aged from 11 months to 8 years.

METHODS

Goats were anesthetized three times with propofol and anesthesia was maintained with isoflurane. One of three doses of atracurium was administered intravenously 30 minutes after induction: 0.25 mg kg-1 (AT25), 0.5 mg kg-1 (AT50) or 0.75 mg kg-1 (AT75). Acceleromyographic train-of-four ratio (TOFR) followed by train-of-four counts (TOFC) were recorded at 30 second intervals after atracurium administration to determine blockade onset (TOFC = 0). The TOFR followed by TOFC were recorded at 5 minute intervals until return to pre-atracurium baseline (TOFR = 1.0). Normally distributed data were analyzed with repeated measures anova and a Tukey multiple comparison test. Data not normally distributed were analyzed with a Friedman test and a Dunn's multiple comparison test.

RESULTS

For AT50 and AT75, 100% of goats achieved TOFC = 0 after atracurium administration. For AT25, however, 87.5% of goats achieved TOFC = 0 after atracurium administration. The onset time was shorter for AT75 [1.5 (0.5-1.5) minutes; median (range)] than for AT25 [2 (1-4) minutes] (p = 0.048). The duration of action [from onset time to complete reversal (TOFR = 1.0)] was significantly shorter for AT25 (52 ± 12 minutes, mean ± SD) than for AT50 (77 ± 18 minutes) (p < 0.001) and AT75 (85 ± 16 minutes) (p < 0.001). There was no significant difference in duration between AT50 and AT75 (p = 0.238).

CONCLUSIONS AND CLINICAL RELEVANCE

Doses of 0.5 and 0.75 mg kg-1 atracurium may produce complete neuromuscular blockade in healthy, anesthetized goats.

Generalised neuromuscular blockade after intraurethral administration of atracurium besilate in a male cat with urethral obstruction

A 4-year-old, entire, male, domestic long-haired cat was presented with an acute history of stranguria and dysuria and diagnosed with urolithiasis causing urethral obstruction. The patient was induced to general anaesthesia and several unsuccessful attempts to flush the uroliths retrogradely towards the bladder were made. An intraurethral administration of the neuromuscular blocking agent atracurium was performed as it has been reported to facilitate urethral catheterisation without any side effects. Respiratory arrest developed after 15 minutes from atracurium administration, which was promptly recognized and treated with mechanical ventilation. The absence of muscle contraction in response to a nerve stimulation confirmed a generalised muscle blockade. Approximately 35 minutes after, a muscle response to nerve stimulation appeared. Neostigmine combined with glycopyrrolate was administered resulting in complete recovery from neuromuscular blockade. In conclusion, the use of intraurethral atracurium can result in systemic absorption of the drug with subsequent generalised neuromuscular blockade.

Comparison of the Onset of Action, Maintenance, and Recovery of Three Weight-based Dosing of Cisatracurium in Patients with Morbid Obesity in Laparoscopic Bariatric Surgery: A Randomized Clinical Trial

Background

For patients with morbid obesity, different cisatracurium dosage regimens are recommended. This study aimed to compare the onset of action, the sufficiency of neuromuscular blockade during infusion, and the recovery of the three distinct cisatracurium dosage scalars in patients with morbid obesity undergoing laparoscopic bariatric surgery.

Methods

In this randomized clinical trial, 55 patients were scheduled for bariatric surgery at Firoozgar Hospital from March 2020 to August 2021. Using a block randomization method, they were randomly divided into three groups, based on total body weight (TBW group), fat-free mass (FFM group), or ideal body weight (IBW group), to receive a bolus of cisatracurium 0.2 mg/Kg, followed by an infusion of 2 µg/Kg, to maintain a train-of-four (TOF) count≤2. Data were analyzed using SPSS software. P<0.05 was considered statistically significant.

Results

The mean time (seconds) to reach TOF0 in the TBW group was significantly shorter (201.89, 95%CI=192.99-210.79; P=0.004) than the IBW group (233.53, 95%CI=218.71-248.34; P=0.01). However, this difference was not statistically significant between TBW and FFM groups (220.83, 95%CI=199.73-241.94; P=0.81) or between FFM and the IBW groups (P=0.23). The rescue dose and increments of cisatracurium infusion were not required in the TBW group, whereas their probability was 4.81 times higher in the IBW group than the FFM group. Furthermore, the TBW and FFM groups had higher mean surgical condition scores than the IBW group (P<0.001, and P=0.006, respectively).

Conclusion

Cisatracurium loading and infusion dosing based on FFM provide a comparable onset of action and surgical field condition to the TBW-based dosing with a shorter recovery time. However, IBW-based dosing of cisatracurium was insufficient for laparoscopic bariatric surgery.Trial Registration Number: IRCT20151107024909N9.A preprint of this study was published at . doi: .

Duration of neuromuscular block is more variable and recovery time is shorter with rocuronium than cisatracurium in anesthetized dogs

OBJECTIVE

To compare the variability in the duration of action of a single dose of rocuronium or cisatracurium, and duration of subsequent top-up doses in anesthetized dogs.

ANIMALS

Thirty dogs requiring ophthalmic surgery with neuromuscular block.

PROCEDURES

Neuromuscular function was monitored with train-of-four (TOF) and acceleromyography. Dogs received an initial dose of rocuronium 0.6 mg/kg, or cisatracurium 0.15 mg/kg IV, which produced complete neuromuscular block. Upon return of the first response (T1) of TOF, a third of the initial dose was repeated. The duration of the initial dose and its variability were compared between agents. Duration of subsequent top-up doses was assessed with mixed effect models. Spontaneous (from last return of T1) or neostigmine-enhanced (from administration to complete recovery) recovery times were measured for each agent.

RESULTS

Duration of action of the initial dose was [median (range)] 25 (10-60) min with rocuronium and 35 (15-45) min with cisatracurium (p = .231). The variability of rocuronium was 3.25 times larger than cisatracurium (p = .034). Duration of top-up doses did not vary for either agent. Spontaneous recovery was shorter for rocuronium [15 (10-20) min] than cisatracurium [25 (15-45) min] (p = .02). Neostigmine-enhanced recovery times were 5 (5-25) for rocuronium and 10 (5-10) for cisatracurium (p = .491).

CONCLUSIONS

Duration of action for a single dose is significantly more variable with rocuronium than cisatracurium. Time to spontaneous recovery was longer for cisatracurium, and cases of unexpectedly long recovery times were observed with both agents. Objective monitoring is recommended.

Cisatracurium regulates the CXCR4/let-7a-5p axis to inhibit colorectal cancer progression by suppressing TGF-β/SMAD2/3 signalling

OBJECTIVE

To reveal the effects and related mechanism of cisatracurium on colorectal cancer (CRC) development.

METHODS

HCT116 and SW480 cells were treated with various concentrations of cisatracurium or transforming growth factor-β (TGF-β). Chemokine C-X-C-Motif Receptor 4 (CXCR4) was overexpressed and let-7a-5p was silenced in cells by transfection with pcDNA3.1-CXCR4 or let-7a-5p inhibitor. Cell Counting Kit-8 (CCK-8) assay measured cell viability, and transwell and wound healing assays evaluated cell invasion and migration, respectively. The expression levels of let-7a-5p and CXCR4 were measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Western blotting was conducted to test the levels of CXCR4, TGF-β/SMAD2/3 signalling and metastasis-related proteins. A tumour xenograft assay was performed to assess tumour growth.

RESULTS

Cisatracurium treatment suppressed the viability and metastasis of HCT116 and SW480 cells in a concentration-dependent manner, whereas activating TGF-β/SMAD2/3 signalling significantly reversed these effects. Cisatracurium treatment markedly reduced CXCR4 expression by inhibiting TGF-β/SMAD2/3 signalling. Besides, let-7a-5p was identified as a target of CXCR4 and could be upregulated by cisatracurium. Both CXCR4 overexpression and let-7a-5p knockdown alleviated the biological roles of cisatracurium in CRC cells. Moreover, a tumour xenograft assay further confirmed that cisatracurium inhibited tumour growth and metastasis by increasing let-7a-5p expression.

CONCLUSION

Cisatracurium suppressed the viability, metastasis and tumour growth of CRC by regulating the CXCR4/let-7a-5p axis via inhibiting TGF-β/SMAD2/3 signalling. These findings provide a theoretical basis for the role of cisatracurium in the prognosis of CRC patients.

Cisatracurium inhibits the proliferation, migration and invasion of breast cancer cells by regulating the expression of miR-3174

Breast cancer is a type of cancer that begins in the breast tissue. Being a woman is the most important factor in the risk of breast cancer. Although men also get the cancer, women are much more likely to get it. This experiment was founded to investigate the effect and mechanism of Cisatracurium on breast cancer cell proliferation, migration and invasion. Breast cancer cells MDA-MB-231 were cultured in vitro. MDA-MB-231 cells were treated with cisatracurium of different concentrations for 48 h. CCK-8method detected cell proliferation, Transwell detected cell migration and invasion, Western Blot method detected the expression levels of CyclinD1, p21, MMP-2andMMP-9protein in cells, RT-qPCR) detected the expression level of miR-3174in cells. After miR-3174 inhibitor was transfected into MDA-MB-231 in order to down-regulate the expression of miR-3174, the same methods as above were used to observe the effect of the down-regulating miR-3174 expression on MDA-MB-231 cell proliferation, migration and invasion as well as the expression levels of CyclinD1, p21, MMP -2 andMMP-9 protein. After different concentrations of Cisatracurium acted on MDA-MB-231 cells, the cell inhibition rate and p21 protein expression were significantly increased (p&lt;0.05), the number of cell migration and invasion and the expression levels of CyclinD1, MMP-2 and MMP-9 were significantly reduced (p&lt;0.05), and the expression of miR-3174 in cells was significantly reduced (p&lt;0.05). After down-regulating the expression of miR-3174, the cell inhibition rate and p21 protein expression were significantly increased (p&lt;0.05), the number of cell migration and invasion and the expression levels of CyclinD1, MMP-2 and MMP-9 were significantly reduced (p&lt;0.05). Up-regulating miR-3174 expression could reverse the effect of Cisatracurium on the proliferation, migration and invasion of MDA-MB-231 cells. Cisatracurium can inhibit the proliferation, migration and invasion of breast cancer MDA-MB-231 cells, and its mechanism is related to the down-regulation of miR-3174 expression in cells.

Effect of Atropine With Propofol vs Atropine With Atracurium and Sufentanil on Oxygen Desaturation in Neonates Requiring Nonemergency Intubation: A Randomized Clinical Trial

IMPORTANCE

Propofol or a combination of a synthetic opioid and muscle relaxant are both recommended for premedication before neonatal intubation but have yet to be compared.

OBJECTIVE

To compare prolonged desaturation during neonatal nasotracheal intubation after premedication with atropine-propofol vs atropine-atracurium-sufentanil treatment.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blind, randomized clinical trial (2012-2016) in 6 NICUs in France that included 173 neonates requiring nonemergency intubation. The study was interrupted due to expired study kits and lack of funding.

INTERVENTIONS

Eighty-nine participants were randomly assigned to the atropine-propofol group and 82 to the atropine-atracurium-sufentanil group before nasotracheal intubation.

MAIN OUTCOMES AND MEASURES

The primary outcome was prolonged desaturation (Spo2 <80% lasting > 60 seconds), using intention-to-treat analysis using mixed models. Secondary outcomes assessed the characteristics of the procedure and its tolerance.

RESULTS

Of 173 neonates randomized (mean gestational age, 30.6 weeks; mean birth weight, 1502 g; 71 girls), 171 (99%) completed the trial. Of 89 infants, 53 (59.6%) in the atropine-propofol group vs 54 of 82 (65.9%) in the atropine-atracurium-sufentanil group achieved the primary outcome (adjusted RD, -6.4; 95% CI, -21.0 to 8.1; P = .38). The atropine-propofol group had a longer mean procedure duration than did the atropine-atracurium-sufentanil group (adjusted RD, 1.7 minutes; 95% CI, 0.1-3.3 minutes; P = .04); a less frequent excellent quality of sedation rate, 51.7% (45 of 87) vs 92.6% (75 of 81; P < .001); a shorter median time to respiratory recovery, 14 minutes (IQR, 8-34 minutes) vs 33 minutes (IQR, 15-56 minutes; P = .002), and shorter median time to limb movement recovery, 18 minutes (IQR, 10-43 minutes) vs 36 minutes (IQR, 19-65 minutes; P = .003). In the 60 minutes after inclusion, Spo2 was preserved significantly better in the atropine-propofol group (time × treatment interaction P  = .02). Of the atropine-propofol group 20.6% had head ultrasound scans that showed worsening intracranial hemorrhaging (any or increased intraventricular hemorrhage) in the 7 days after randomization vs 17.6% in the atropine-atracurium-sufentanil group (adjusted RD, 1.2; 95% CI, -13.1 to 15.5, P = .87). Severe adverse events occurred in 11% of the atropine-propofol group and in 20% of the atropine-atracurium-sufentanil group.

CONCLUSIONS AND RELEVANCE

Among neonates undergoing nonemergency nasotracheal intubation, the frequency of prolonged desaturation did not differ significantly between atropine used with propofol or atropine used with atracurium and sufentanil. However, the study may have been underpowered to detect a clinically important difference, and further research may be warranted.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01490580, EudraCT number: 2009-014885-25.

Influences of cisatracurium besylate and vecuronium bromide on muscle relaxant effects and electromyography of tracheal intubation under general anesthesia

OBJECTIVE

To observe the influences of atracurium besylate and vecuronium bromide on muscle relaxant effects and electromyography of patients with tracheal intubation under general anesthesia in thyroid surgery.

PATIENTS AND METHODS

120 patients treated with thyroid surgery were randomly divided into group A and group V. Patients in group A were administered with cisatracurium besylate combined with propofol and fentanyl for induction of tracheal intubation under general anesthesia. Patients in group V were administered with 0.10 mg/kg vecuronium bromide combined with propofol and fentanyl for induction of tracheal intubation under general anesthesia. Then, the amplitude in electromyography was observed 30-70 min after I.V. muscle relaxant medicine to record the time for patients to reach 0% TW convulsion in abductor pollicis muscle and to observe the muscle relaxant effects.

RESULTS

There was no statistical difference in the time to reach 0% TW in two groups (p>0.05). After 30 min of injection of muscle relaxants, EMG positive rate and TW value in group A were significantly higher than those in group V (p<0.05). After 50-70 min of injection of muscle relaxants, EMG positive rate of patients in two groups was up to 100%, and EMG amplitude in group A was significantly higher than that in group V (p<0.05). The time of taking muscle relaxant effects in group A was significantly faster than that in group V (p<0.05), while the recovery time of autonomous respiration and the time of autonomous body activity in group A were slightly lower than those in group V (p>0.05). There was no statistical difference in the time of eye-opening of both groups (p>0.05). MAP and HR of patients in both groups showed no statistical difference before and after injection (p>0.05).

CONCLUSIONS

Average EMG amplitude and the positive rate of effective EMG amplitude of cisatracurium besylate are all higher than those of vecuronium bromide. With faster effects and shorter action time, cisatracurium besylate is more suitable in thyroid surgery IONM (intraoperative neurophysiological monitoring).

The effect of general anaesthesia and neuromuscular blockade on Eustachian tube compliance: a prospective study

OBJECTIVE

The most common complications of hyperbaric oxygen treatment (HBOT) are related to pressure changes on gas-containing cavities. Therefore, inability to auto-inflate the middle ear may result in transient or permanent hearing loss. However, it seems that middle ear barotrauma (MEBt) does not develop more often in mechanically ventilated patients than in ambulatory patients. This might be explained by deep sedation of these patients. Therefore, the aim of this study was to determine whether anaesthesia and/or neuromuscular blockade can influence Eustachian tube (ET) function.

METHODS

Forty patients who were undergoing surgery under general anaesthesia were enrolled in this prospective study. ET function was evaluated by tympanography performed three times: before induction of general anaesthesia (baseline), after induction with sufentanyl/propofol and after full blockade was achieved with a long-acting neuromuscular blocking agent.

RESULTS

There were no differences in ear volume (P = 0.19) and ear pressure (P = 0.07). There was a significant variation in compliance on tympanography after the induction of general anaesthesia (P = 0.009). Compared to the baseline, this variation was characterized by an increase after induction of anaesthesia (24 ± 7.13%, P 〈 0.01) and neuromuscular blockade (23 ± 8.9%, P 〈 0.05). The difference between after induction and after neuromuscular blockade was not statistically significant (P = 0.13).

DISCUSSION

The findings of this trial suggest that the administration of hypnotic drugs associated with opioids improves ET compliance. Therefore it may have favourable prophylactic effects on MEBt in ventilated intensive care unit patients scheduled for HBOT.

[Impact of gender on the dose-effect relationship of cisatracurium]

OBJECTIVE

To evaluate the impact of gender differences on the dose-effect relationship of cisatracurium.

METHODS

Eighty ASA class I or II patients (40 male and 40 female patients) undergoing elective abdominal surgeries received a single-dose intravenous injection of midazolam and fentanyl. The male and female patients were subdivided into 4 equal groups to receive a intravenous bolus of 20, 30, 40, or 50 µg/kg of cisatracurium. The neuromuscular block was measured using a neuromuscular transmission monitor, and the responses were defined in terms of the percentages of maximum suppression in T1 of TOF of the adductor pollicis muscle. According to log-probit transformation of the data of the dose and response, the dose-response curve of cisatracurium was established through linear regression. The onset time of vecuronium was also observed.

RESULTS

The ED95 value of cisatracurium in male patients was 67.4±4.4 µg/kg, significantly higher than that in female patients (48.7±1.0 µg/kg, P<0.05). No significant variation in the onset time was found in the 4 dose groups of either male or female patients (P>0.05).

CONCLUSION

Female patients are more sensitive to cisatracurium than male patients.

Merging PK/PD information in a minimally parameterized model of the neuromuscular blockade

A recursive system identification algorithm that merges PK/PD information in a minimally parameterized Wiener model for the NMB level is presented. The results show that the coupling between one parameter from the linear block and one from the static nonlinearity is advantageous, when evaluated on a database of 60 real collected NMB cases.

[Effect of sevoflurane versus propofol-remifentanil anesthesia on neuromuscular blockade by continuous cisatracurium infusion]

OBJECTIVE

To compare the effects of sevoflurane and propofol-remifentanil anesthesia on neuromuscular blockade produced by continuous cisatracurium infusion.

METHODS

Forty ASA I or II patients undergoing selective surgery were randomly divided into sevoflurane and propofol-remifentanil anesthesia groups (n=20). Neuromuscular blockade was monitored using train-of-four (TOF) stimulation by recording the contraction force of the adductor pollicis muscle with a muscle relaxation monitor. A bolus dose of cisatracurium of 0.15 mg/kg was administered to facilitate endotracheal intubation, followed by continuous infusion adjusted manually to maintain the first twitch (T1) < or = 5% of the control level. The following variables were recorded including the infusion rate, total amount of cisatracurium, spontaneous recovery index (RI), and the time interval from termination of infusion cisatracurium to recovery of TOF ratio (TOFR) to 0.9.

RESULTS

With the maintenance of a 95%-99% neuromuscular blockade, the infusion rate was significantly lower in sevoflurane group than in propofol-remifentanil group (P<0.05), and stabilized in both groups after 120 min. No significant differences were found in RI or the time to TOFR of 0.9 between the two groups (P>0.05).

CONCLUSION

During the maintenance of stable neuromuscular blockade by continuous cisatracurium infusion, both sevoflurane and propofol-remifentanil anesthesia can time-dependently enhance the effect of cisatracurium without producing significant differences in the recovery properties.

Clinical predictors of duration of action of cisatracurium and rocuronium administered long-term

BACKGROUND

The duration of action of neuromuscular blocking drugs (NBDs) varies between individuals and even within individuals in different settings.

OBJECTIVES

To define predictors of variance in duration of action of rocuronium and cisatracurium administered long-term.

METHODS

A prospective, double-blind, multicenter trial that included 113 patients scheduled for major abdominal surgery and postoperative admission to the intensive care unit. Patients received repetitive (median, 7) equipotent doses of rocuronium or cisatracurium to maintain deep relaxation (twitch height of the adductor pollicis muscle <25% of baseline). Effects of weight, age, sex, American Society of Anesthesiologists risk score, lowest core temperature, duration of NBD administration, and tobacco smoking history on duration of action of cisatracurium and rocuronium were determined via multiple regression analysis.

RESULTS

Only duration of NBD administration was predictive of the duration of action of rocuronium. The predicted increase in time to recovery of the train-of-4 ratio to 0.9 (duration TOF 0.9) per hour of continuous NBD treatment was 12.4 minutes. In contrast, only lowest core body temperature was predictive of cisatracurium's duration of action, and the predicted increase in duration TOF 0.9 per degree Celsius decrease was 9.8 min.

CONCLUSION

Duration of NBD treatment is strongly predictive of the duration of action of rocuronium, and body temperature is predictive of the duration of action of cisatracurium. These data may help decrease the incidence of drug-induced muscle weakness in recovery rooms and surgical intensive care units, particularly if neuromuscular transmission monitoring is not available.

[Effects of atracurium pretreatment with magnesium on speed of onset, duration, and recovery of neuromuscular blockade]

OBJECTIVE

To determine the effects of atracurium pretreatment with magnesium on speed of onset, duration, and recovery of neuromuscular block.

METHODS

Thirty patients who were undergoing elective gynecologic laparoscopic examination and treatments under general anesthesia were randomized into magnesium group (n = 15) and control group (n = 15). Before induction of general anesthesia, patients in magnesium group intravenously received MgSO4 30 mg/kg in saline within 5 minutes, and patients in control group received the same volume of saline without MgSO4. In both groups, the train-of-four (TOF) responses to stimuli of the ulnar nerve were measured at intervals of 12 seconds. Anesthesia was induced with Fentanyl and Propofol through target controlled infusion (TCI), and tracheal intubation was performed with 0.5 mg/kg atracurium after stabilization of the electromyography recording. The onset time of muscle relaxation, clinical duration of action, recovery index, and recovery time were recorded. To determine serum magnesium and calcium levels, blood samples were collected before MgSO4/saline infusion and at the end of operation. Haemodynamic changes and other responses during induction were also recorded.

RESULTS

The onset time from the end of injection to maximum neuromuscular blockade was significantly shorter in magnesium group than in control group (P < 0.01). Duration of relaxant action, recovery index, and recovery time in magnesium group were significantly prolonged than in control group (P < 0.01). Serum magnesium level significantly decreased after management (P < 0.01), and there was also a decrease trend in magnesium group. No change of serum calcium levels in both groups was observed. No adverse event was reported.

CONCLUSION

Prior administration of magnesium sulphate can increase the onset speed of atracurium and prolong the duration of atracurium-induced neuromuscular blockade.

Comparative study of neuromuscular blocking and hemodynamic effects of rocuronium and cisatracurium under sevoflurane or total intravenous anesthesia

Neuromuscular blockers (NMB) are important adjuvant to general anesthesia. Rocuronium bromide and cisatracurium besylate are considered relatively recently introduced non-depolarizing muscle relaxants.

OBJECTIVES

This study evaluates the enhancement of cisatracurium and rocuronium-induced neuromuscular block during anesthesia with 1.5 MAC sevoflurane or total i.v. anesthesia (TIVA), hemodynamic effects and side effects.

METHODOLOGY

80 patients were randomly allocated into one of four equal Groups to receive either rocuronium (under sevoflurane or propofol TIVA) or cisatracurium (under sevoflurane or propofol TIVA). The NMB effects ofrocuronium and cisatracurium were studied by constructing dose-effect curves. Acceleromyography (TOF-Guard) and train-of-four (TOF) stimulation of the ulnar nerve were used (2 Hz every 15 sec). Cisatracurium and rocuronium were administered in increments until depression of T1/T0 > 95% was reached. Hemodynamic effects of both muscle relaxants together with sevoflurane or propofol were assessed using thoracic bioimpendance.

RESULTS

Depression ofT1/T0 was enhanced under sevoflurane compared to TIVA. ED50 and ED95 values of both drugs were significantly lower under sevoflurane more than TIVA. Recovery index 25-75% and time to a TOF ration of 0.70 were prolonged significantly by sevoflurane compared to TIVA. Hemodynamically, rocuronium and cisatracurium did not exert significant changes, but the interaction of the relaxants and the anesthetic agents resulted in statistically significant decline in some hemodynamic parameters at certain periods which are not clinically significant and required no medications.

CONCLUSION

We conclude that the effects of rocuronium and cisatracurium are significantly enhanced during sevoflurane compared with propofol anesthesia and the recovery is lower.

Priming with rocuronium to accelerate the onset time of cisatracurium during intubation

BACKGROUND

The priming technique, in which a small dose of nondepolarizing muscle relaxant is administered 3-6 minutes before giving the intubation dose, can speed up the onset of muscle relaxation in patients with paralysis during intubation. We investigated the priming technique and compared 2 different priming agents (rocuronium and cisatracurium) at a priming time of 3 minutes and its effect on decreasing the onset time of cisatracurium.

METHODS

A total of 60 patients with ASA physical status I-II scheduled for elective surgery were enrolled. After induction with propofol and fentanyl, the patients were randomized into 1 of 3 groups. Group 1 received rocuronium 0.06 mg/kg as a priming dose. Group 2 received cisatracurium 0.01 mg/kg as a priming dose. Group 3 received normal saline and constituted the control group. After a 3-minute priming time, intubation doses of cisatracurium were given (Groups 1 and 2, 0.14 mg/kg; Group 3, 0.15 mg/kg). First twitch height percentage (T1/T0%; % of control) and train-of-four percentage (T4/T1%) were recorded every 10 seconds from baseline until T1/T0% reached 0.

RESULTS

Rocuronium (Group 1) and cisatracurium (Group 2) significantly accelerated the onset of cisatracurium (Group 1, 117.0 +/- 29.0 seconds; Group 2, 151.0 +/- 37.5 seconds; Group 3, 221.5 +/- 36.6 seconds; all p < 0.001).

CONCLUSION

Priming with rocuronium or cisatracurium for 3 minutes significantly accelerated the onset of cisatracurium. Priming with rocuronium for 3 minutes improved the onset time of cisatracurium even more than priming with cisatracurium itself.

Influence of a continuous prednisolone medication on the time course of neuromuscular block of atracurium in patients with chronic inflammatory bowel disease

BACKGROUND

Corticosteroids interact with neuromuscular blocking agents. However, experimental data are contradictory: enhancement and attenuation of the neuromuscular block has been observed. This study tested the influence of long-term medication with prednisolone on atracurium-induced neuromuscular block.

METHODS

Sixty patients with chronic inflammatory bowel disease undergoing elective abdominal surgery were investigated. Thirty patients received a long-term medication with prednisolone (Group A) and 30 were without corticoid medication (Group B). Additionally, another 30 patients without inflammatory bowel disease and without corticoid medication served as control (Group C). The following parameters of an atracurium-induced neuromuscular block (0.25 mg kg(-1)) were measured: onset time, maximum block, recovery to 25% first twitch height, recovery index (time from 25% until 75% recovery of first twitch), duration to recovery to a train-of-four (TOF) rate of 0.7 and 0.9.

RESULTS

The groups did not differ with regard to onset time, maximum block, and recovery index. The duration to 25% twitch height was significantly lower in Group A [18.1 (0-30.7) min] compared with Group B [23.5 (0-36.7) min; P<0.05]. Duration to a TOF rate of 0.7 and 0.9, respectively, were significantly reduced in Group A [36.1 (7.9) and 40.9 (9.0 min)] compared with Group B [47.9 (7.6) and 53.4 (9.2) min; P<0.001].

CONCLUSIONS

Long-term medication with prednisolone resulted in a shorter duration of an atracurium-induced neuromuscular block in patients with Crohn's disease or ulcerative colitis. The presence of the inflammatory bowel disease did not influence the time course of the neuromuscular block.

Primingtechnik mit Cisatracurium

OBJECTIVE

Priming can significantly shorten the onset of nondepolarizing neuromuscular blocking agents (NNBA) measured at the adductor pollicis muscle (APM). In spite of the known risks, priming is very popular especially in cases where NNBAs with a long onset time are used. However, there are no data regarding the onset of action for a priming technique measured at the laryngeal muscles although these muscles are of great importance for conditions of intubation and patient safety. The aim of this study was to compare a bolus application and a priming technique with respect to the laryngeal onset time and peak effect.

PATIENT AND METHODS

After approval of the local ethics committee and written informed consent, 36 patients undergoing elective thyroid surgery were enrolled in the study. Anesthesia was induced and maintained with a target controlled infusion of propofol (target concentration 2.7-6.0 microg/ml) and infusion of remifentanil (0.25-0.75 microg/kgbw/min). After loss of consciousness, a tube with a surface electrode was placed into the trachea without the application of any neuromuscular blocking agent. Neuromuscular monitoring consisted of evoked electromyography (EMG) of the laryngeal adductor muscles via the surface electrode and evoked acceleromyography (TOF Guard) of the right adductor pollicis muscle (APM). After transcutaneous stimulation of the recurrent laryngeal nerve and ulnar nerve, either 0.9% NaCl followed by 0.1 mg/kgbw cisatracurium after 3 min (bolus group, n=12), a priming dose of 0.01 mg/kgbw cisatracurium followed by 0.09 mg/kgbw 3 min later (low dose priming group, n=12) or a priming dose of 0.015 mg/kgbw cisatracurium followed by cisatracurium 0.085 mg/kgbw 3 min later (high dose priming group, n=12) were injected. Lag time, onset time and peak effect of NMB were recorded and compared between the groups.

RESULTS

Demographic data, lag time and peak effect were comparable between the three groups. Onset time at the laryngeal muscles was significantly shorter in the high dose priming group (80+/-17 s), when compared to the low dose priming group (128+/-23 s) and bolus group (142+/-29 s). Onset time at the APM was also significantly shorter in the high dose priming group (154+/-35 s), when compared with the bolus group (226+/-76 s). The recovery of the neuromuscular function measured at the APM showed no differences between the groups.

CONCLUSION

Our results show that only high dose priming of cisatracurium can significantly shorten the laryngeal onset time. However, clinical routine use is not recommended due to possible side-effects.

[Influence of neostigmine on the course of neuromuscular blockade with rocuronium or cisatracurium: a randomized, double-blind trial]

OBJECTIVES

To compare the time-course of neuromuscular blockade with rocuronium or cisatracurium during intravenous anesthesia, in terms of both the time to spontaneous recovery or time to reversal after administration of neostigmine.

MATERIAL AND METHODS

Patients classified as ASA 1-2 were randomized to receive blinded administration of a single injection of twice the 95% effective dose of rocuronium or cisatracurium for general anesthesia, and then neostigmine plus atropine at recovery of the first train-of-4 (TOF) twitch at 5% or 25%, or normal saline solution as placebo at recovery of the first TOF twitch at 25%. The neuromuscular blockade was monitored by acceleromyography. Intergroup comparisons were carried out by Student t test and analysis of variance.

RESULTS

Sixty patients were enrolled. Mean (SD) time to onset was faster with rocuronium at (1.04 [0.32] minutes) compared with cisatracurium at (2.58 [0.81] minutes) and duration was shorter: time to the first twich at 5% was 30 (6.4) minutes with rocuronium and 38.1 (9.7) minutes with cisatracurium. The total duration of blockade (time to the 80% TOF ratio) was also shorter with rocuronium when the neuromuscular blockade was reversed, but there were no differences in the time to block reversal when neostigmine was not used: 62 (18.9) minutes to recovery from the rocuronium blockade vs 66.96 (15.9) minutes to recover from a cisatracurium blockade. A high percentage of patients had less than an 80% TOF ratio at 60 and 90 minutes of administration of the neuromuscular blockerswhen reversal was not used (patients receiving rocuronium, 60% at 60 minutes, and 20% at 90 minutes; patients receiving cisatracurium, 80% at 60 minutes, and 40% at 90 minutes).

CONCLUSION

Not antagonizing a rocuronium- or cisatracurium-induced neuromuscular blockade in surgical procedures lasting less than 90 minutes can lead to a high percentaje of residual blockade (TOF ratio <80%).

Long-term effects of botulinum toxin on neuromuscular function

BACKGROUND

Recent reports indicate increased incidence of Clostridium botulinum infections, particularly among drug abusers and tissue allograft recipients. Botulinum toxin also has potential application in biochemical warfare. The neurotoxin-induced paralysis often requires mechanical ventilation with and without muscle relaxants. The authors investigated the long-term effects of botulinum toxin on muscle function, expression of nicotinic acetylcholine receptors (nAChRs), and their interaction with muscle relaxant, atracurium.

METHODS

Rats (n=30) were injected with varying doses (0.625, 2.5, and 10 U) of botulinum toxin into the tibialis muscle. Control animals (n=9) received an equivalent volume of saline. At 128 days after injection, neuromuscular function, pharmacodynamics of atracurium, and nAChRs were evaluated.

RESULTS

Nerve-evoked tensions, including tetanic tension and muscle mass, were decreased on the toxin-injected side in a dose-dependent manner relative to saline-injected controls as well as the contralateral side. Specific muscle tension and specific tetanic muscle tension (tensions/muscle mass) were not reduced. The ED10 of atracurium was reduced, the ED50 was unchanged, and the ED90 was increased in the highest (10-U) dose of toxin group. The atracurium plasma concentration to maintain a steady state 50% paralysis was significantly reduced in the 10-U toxin group. The nAChR concentrations in the tibialis muscle were significantly increased in a dose-dependent manner in all experimental groups.

CONCLUSION

Botulinum toxin causes dose-dependent long-term neuromuscular changes. The loss of tension generating capacity is almost exclusively related to muscle atrophy, because the specific tension did not change. The decreased ED10, unaltered ED50, and increased ED90 to atracurium suggest its interactions with different isoforms of receptors having varying sensitivity to atracurium. The absence of fade, despite the persistent botulinum toxin-induced denervation (increased nAChRs), suggests that the up-regulated nAChRs may have compensated for the prejunctional effects of botulinum toxin.

Muscle relaxation does not influence venous oxygen saturation during cardiopulmonary bypass

STUDY OBJECTIVE

To examine whether the omission of neuromuscular blocking drugs during cardiopulmonary bypass (CPB) is associated with increased anesthetic requirements, higher frequency of intraoperative movements, and lower venous oxygen saturation (SvO(2)).

DESIGN

Prospective, randomized study.

SETTING

Large community hospital.

PATIENTS

30 ASA physical status III and IV patients scheduled for cardiac surgery.

INTERVENTIONS

Patients were randomized to one of two groups: group 1 (n = 15) received a 3xED(95) bolus dose of cisatracurium at induction and thereafter no more neuromuscular blocking drug; group 2 (n = 15) received a continuous infusion of cisatracurium during the entire procedure.

INTERVENTIONS

Both groups received a standardized anesthetic with bispectral index-guided propofol target-controlled infusion and a remifentanil infusion steered by hemodynamic changes. Venous oxygen saturation was continuously determined during CPB.

MEASUREMENTS AND MAIN RESULTS

Propofol consumption was 5.4 +/- 1.7 and 4.4 +/- 1.0 mg/(kg/h) in groups 1 and 2, respectively (P = 0.07). Remifentanil consumption was 0.15 +/- 0.05 and 0.17 +/- 0.05 mug/(kg/min) in groups 1 and 2, respectively (P = 0.19). In groups 1 and 2, no patient recalled any intraoperative phenomena; none moved or had diaphragmatic contractions. During CPB, SvO(2) was 81.3 +/- 3.2% (76%-85%) in group 1 and 80.6 +/- 3.1% (73%-85%) in group 2 (P = 0.53).

CONCLUSIONS

Omitting the continuous administration of neuromuscular blocking drugs during CPB did not increase anesthetic requirements. No intraoperative movements occurred, nor was there decreased SvO(2).

Efeito do propofol associado à efedrina no tempo de latência do cisatracúrio

OBJECTIVE

The onset time of neuromuscular blocking drugs is partially determined by circulatory factors, including muscle blood flow and cardiac output. The aim of the present paper was to: 1) compare the haemodynamic effects of adding different doses of ephedrine to an induction dose of propofol and remifentanil. 2) onset time of cisatracurium.

METHODS

Sixty patients were randomly allocated into three groups: G1 - 1% propofol; G2 - 1% propofol + 0.5 mg.ml-1 ephedrine and G3 - 1% propofol + 1.0 mg.ml-1 ephedrine. All patients received continuous infusion of remifentanil (0.5 mg.kg-1.min-1). The rate of propofol infusion was 180 ml.h-1 until loss of consciousness and a loading dose of cisatracurium (0.15 mg.kg-1) was then given. After induction of anesthesia, the ulnar nerve was stimulated supramaximally every 10s, and the evoked twitch response of the adductor pollicis was recorded by accelerometry.

RESULTS

There was no statistical difference between groups with respect to age, weight, dose of propofol administered and onset time of cisatracurium. Heart rate, SpO2, systolic, diastolic and mean blood pressures were compared at 1 and 3 min post-induction. There were statistical differences in HR, SAP, DAP and MAP, without significant adverse clinical effects.

CONCLUSIONS

There were no clinically important decreases in the hemodynamic parameters evaluated in the groups receiving ephedrine or not, and the onset time of cisatracurium was the same for all groups.

Infusions of rocuronium and cisatracurium exert different effects on rat diaphragm function

OBJECTIVE

Aminosteroidal and benzylisoquinoline neuromuscular blocking agents are used in the intensive care unit to facilitate mechanical ventilation. The use of these agents has been associated with development of critical illness myopathy; however, the relative frequency of myopathy development among agents is not known. The aim of our study was to compare the effects of 24 h infusion of rocuronium or cisatracurium on the diaphragm in mechanically ventilated rats.

DESIGN

Randomized, controlled experiment.

SETTING

Basic animal science laboratory.

SUBJECTS

Male Wistar rats, 14 weeks old.

INTERVENTIONS

Rats were divided into four groups to receive either saline, rocuronium (low dose) or cisatracurium (low or high dose).

MEASUREMENTS AND RESULTS

After 24 h, in vitro diaphragm tetanic force was decreased after rocuronium (-33% vs. saline), while the force was more preserved after cisatracurium, even in the high-dose group. Cross-sectional areas of the different diaphragm and gastrocnemius fibers were unaltered. Diaphragmatic MURF-1 mRNA was increased after rocuronium (+44% vs. saline), while unchanged in both cisatracurium groups. Calpain activity was increased after rocuronium (+75% vs. saline) and unchanged in the cisatracurium groups. MURF-1 mRNA expression and calpain activity were negatively correlated with diaphragm force.

CONCLUSIONS

Cisatracurium infusion during controlled mechanical ventilation exerted less detrimental effects on diaphragm function and proteolytic activity than infusion of rocuronium, even with the higher effective dose. These data suggest that increased calpain activity and increased activation of the ubiquitin proteasome system play a role in the different effects of these agents.

Comparisons of the dose-response and recovery time course of vecuronium and atracurium in anesthetized chinese adult patients

BACKGROUND

The authors found no study comparing potency and duration of action of vecuronium and atracurium in healthy Chinese, so they compared the dose-response relations of vecuronium and atracurium in anesthetized Chinese adult patients and evaluated the time-course of action of two drugs following administration of equipotent doses.

METHODS

Sixty patients, ASA grade 1, aged from 17 to 50 yr, scheduled for elective plastic surgery were randomly distributed to either the vecuronium or the atracurium group. General anesthesia was maintained with 60% nitrous oxide in oxygen (N2O-O2), thiopental and fentanyl. Neuromuscular function was assessed using a accelerometer with train-of-four (TOF) stimulation at the wrist every 12 sec, and the percentage of depression of first twitch (T1) was used as the study parameter. The dose-response relations of vecuronium and atracurium were determined using the cumulative dose-response technique.

RESULTS

The cumulative dose-response curve of vecuronium was shifted to the left in a parallel fashion compared with that of atracurium. As assessed by linear regression, the potency ratio of vecuronium:atracurium was 6:1. There were significant differences in the ED50, ED90, and ED95 between the two drugs. After the intravenous administration of equipotent doses of both drugs (1.5 x ED95), the duration of peak effect, clinical duration, recovery index, and total duration were not significantly different between the two drugs.

CONCLUSIONS

The neuromuscular blocking potency of atracurium is approximately 17% that of vecuronium in anesthetized Chinese adult patients. Following equipotent doses, the time course of action of atracurium is similar to that of vecuronium.

[Bispectral index monitoring during intrahospital transport]

BACKGROUND AND OBJECTIVE

Risk of morbidity and mortality increases for critically ill patients during transfers within the hospital. Such patients often require sedation, and suboptimal sedation is associated with hypertension, tachycardia, and ventilator dyssynchrony. The aim of this study was to assess level of sedation as indicated by monitoring of the bispectral (BIS) index during intrahospital transport of critical patients.

PATIENTS AND METHODS

Thirty patients who required transport to the critical care unit within the hospital were studied prospectively. We recorded time in transport, the agent used for sedation and the dosage, the BIS index, mean arterial pressure (MAP), and heart rate before starting transport and upon arrival at the critical care unit. The data were recorded by an observer who was not assigned to patient care.

RESULTS

The mean (SD) transport time was 13.9 (4.2) minutes. Midazolam was used in 26 patients and propofol in 4. Ten patients were given a bolus dose of cisatracurium before transfer started. Significant increases were observed in the BIS index (from 47 to 78, (P < .001), MAP (from 73 to 91 mmHg, P < .001), and heart rate (from 72 to 97 beats/min, P < .001) between the moment of starting transport and arrival at the critical care unit. Changes in the BIS index correlated significantly with changes in heart rate (r = 0.418, P = .024) but not with changes in MAP (r = 0.249, P = .19).

CONCLUSIONS

Monitoring the BIS index during intrahospital transport of sedated, mechanically ventilated patients may be useful for detecting inadequate sedation.

Pharmacological dissection of the human gastro-oesophageal segment into three sphincteric components

Quantifications of gastro-oesophageal anatomy in cadavers have led some to identify the lower oesophageal sphincter (LOS) with the anatomical gastric sling-clasp fibres at the oesophago-cardiac junction (OCJ). However, in vivo studies have led others to argue for two overlapping components proximally displaced from the OCJ: an extrinsic crural sphincter of skeletal muscle and an intrinsic physiological sphincter of circular smooth-muscle fibres within the abdominal oesophagus. Our aims were to separate and quantify in vivo the skeletal and smooth muscle sphincteric components pharmacologically and clarify the description of the LOS. In two protocols an endoluminal ultrasound-manometry assembly was drawn through the human gastro-oesophageal segment to correlate sphincteric pressure with the anatomic crus. In protocol I, fifteen normal subjects maintained the costal diaphragm at inferior/superior positions by full inspiration/expiration (FI/FE) during pull-throughs. These were repeated after administering atropine to suppress the cholinergic smooth-muscle sphincter. The cholinergic component was reconstructed by subtracting the atropine-resistant pressures from the full pressures, referenced to the anatomic crus. To evaluate the extent to which the cholinergic contribution approximated the full smooth-muscle sphincter, in protocol II seven patients undergoing general anaesthesia for non-oesophageal pathology were administered cisatracurium to paralyse the crus. The smooth-muscle sphincter pressures were measured after lung inflation to approximate FI. The cholinergic smooth-muscle pressure profile in protocol I (FI) matched closely the post-cisatracurium smooth-muscle pressure profile in protocol II, and the atropine-resistant pressure profiles correlated spatially with the crural sling during diaphragmatic displacement. Thus, the atropine-resistant and cholinergic pressure contributions in protocol I approximated the skeletal and smooth muscle sphincteric components. The smooth-muscle pressures had well-defined upper and lower peaks. The upper peak overlapped and displaced rigidly with the crural sling, while the distal peak separated from the crus/upper-peak by 1.1 cm between FI and FE. These results suggest the existence of separate upper and lower intrinsic smooth-muscle components. The 'upper LOS' overlaps and displaces with the crural sling consistent with a physiological LOS. The distal smooth-muscle pressure peak defines a 'lower LOS' that likely reflects the gastric sling/clasp muscle fibres at the OCJ. The distinct physiology of these three components may underlie aspects of normal sphincteric function, and complexity of sphincter dysfunction.

Tracheal intubating conditions and pharmacodynamics following cisatracurium in infants and children undergoing halothane and thiopental-fentanyl anesthesia

BACKGROUND

The aims of the present study were to determine the tracheal intubating conditions, onset time, duration of action, and hemodynamic responses following the administration of cisatracurium 0.15 mg x kg(-1) to infants and children.

METHODS

One hundred and eighty-one infants and children aged 1 month to 12 years were randomized to two groups to receive anesthesia with nitrous oxide-oxygen-halothane (group H) or nitrous oxide-oxygen-thiopental-fentanyl (group TF). Intubation conditions were assessed 120 s after cisatracurium administration using a 4-part scale. Neuromuscular transmission was monitored by recording the evoked compound electromyogram of the adductor pollicis.

RESULTS

The proportion of patients with excellent or good intubating conditions was similar in both groups (88 of 90, 98% in group H; 85 of 90, 94% in group TF). However, there was a significantly greater proportion of excellent intubating conditions in group H (79 of 90, 88%) compared with group TF (65 of 90, 72%) (P = 0.01) and recovery time was significantly longer in group H compared with group TF (P < 0.001). There was also a higher proportion of excellent intubating conditions in infants compared with older subjects (P = 0.02) and a shorter onset time (P < 0.001) and longer recovery time (P < 0.001) in younger compared with older patients. Changes in heart rate and arterial pressure were negligible 1 min following the cisatracurium administration.

CONCLUSIONS

Cisatracurium 0.15 mg x kg(-1) produces acceptable intubating conditions at 120 s in the great majority of infants and children. Anesthesia background and age have significant effects on intubating conditions and duration of action of cisatracurium.

Influence of acute normovolaemic haemodilution on the dose-response relationship and time course of action of cisatracurium besylate

BACKGROUND

Acute normovolaemic haemodilution (ANH) is an efficacious blood conservation strategy aiming at avoiding allogeneic blood transfusion. ANH was shown to increase the potency of vecuronium, atracurium, and rocuronium. The aim of our study was to investigate whether cisatracurium potency is altered with ANH.

METHODS

Using the Relaxometer mechanomyograph, we compared cisatracurium dose-response relationship and time course of action in 60 patients randomly allocated to the ANH or control groups. Patients in each group were randomly allocated to receive one of three cisatracurium doses (30, 40, 50 microg kg(-1)) followed by a second supplemental dose to reach a total of 100 microg kg(-1).

RESULTS

ANH did not result in a significant shift in cisatracurium log dose-probit dose-response curve. There was no significant difference in mean (95% confidence intervals) ED(50), ED(90), and ED(95) (effective doses required for 50, 90, and 95% first twitch depression) between the ANH group [29.5 (27-32), 50.4 (47.4-53.4), 58.7 (55.3-62) microg kg(-1)] and the control group [28.2 (25.3-31), 47.6 (44.9-50.3), 55.3 (52.5-58.1) microg kg(-1)], whereas there was no difference in mean (SD) Dur(25) and Dur(0.8) (time until 25% first twitch and 0.8 train-of-four ratio recoveries) between the ANH group [40.8 (5.9), 64.7 (8.4) min] and the control group [42.2 (7.6), 66.5 (10.7) min].

CONCLUSIONS

Our results demonstrated that unlike other previously reported neuromuscular blocking drugs, ANH did not alter cisatracurium potency. Thus, cisatracurium would be the neuromuscular blocking drug of choice in patients who undergo surgery with ANH, as no dose adjustments are required.

Neuromuscular block

Descriptions of the South American arrow poisons known as curares were reported by explorers in the 16th century, and their site of action in producing neuromuscular block was determined by Claude Bernard in the mid-19th century. Tubocurarine, the most important curare alkaloid, played a large part in experiments to determine the role of acetylcholine in neuromuscular transmission, but it was not until after 1943 that neuromuscular blocking drugs became established as muscle relaxants for use during surgical anaesthesia. Tubocurarine causes a number of unwanted effects, and there have been many attempts to replace it. The available drugs fall into two main categories: the depolarising blocking drugs and the nondepolarising blocking drugs. The former act by complex mixed actions and are now obsolete with the exception of suxamethonium, the rapid onset and brief duration of action of which remain useful for intubation at the start of surgical anaesthesia. The nondepolarising blocking drugs are reversible acetylcholine receptor antagonists. The main ones are the atracurium group, which possess a built-in self-destruct mechanism that makes them specially useful in kidney or liver failure, and the vecuronium group, which are specially free from unwanted side effects. Of this latter group, the compound rocuronium is of special interest because its rapid onset of action allows it to be used for intubation, and there is promise that its duration of action may be rapidly terminated by a novel antagonist, a particular cyclodextrin, that chelates the drug, thereby removing it from the acetylcholine receptors.

Addition of cisatracurium to lidocaine for intravenous regional anesthesia

STUDY OBJECTIVE

To determine the onset and regression time of motor and sensory block, and the quality of anesthesia and postoperative analgesia by the addition of cisatracurium to local anesthetic solution in small doses in intravenous regional anesthesia.

DESIGN

Prospective, randomized, double-blind study.

SETTING

University hospital.

PATIENTS

40 ASA physical status I and II patients undergoing elective hand surgery.

INTERVENTIONS

Intravenous regional anesthesia was achieved using 3 mg/kg lidocaine diluted with saline to a total volume of 40 mL in the control group or 0.01 mg/kg of cisatracurium plus 3 mg/kg lidocaine diluted with saline to a total volume of 40 mL in the cisatracurium group.

MEASUREMENTS

The onset and the regression time for sensory and motor block were recorded. Quality of anesthesia, intraoperative, and postoperative analgesic requirements were noted. Mean arterial pressure and heart rate were recorded every 5 minutes.

MAIN RESULTS

The onset time of sensory and motor block in the cisatracurium group was shorter than in the control group, and the difference was statistically significant. The quality of anesthesia was better in the cisatracurium group than in the control group, and the difference was statistically significant. There was no difference between the two groups with respect to sensory block regression time. Motor block regression time was statistically longer in the cisatracurium group than in the control group. Analgesic requirement was greater in the control group than in the cisatracurium group.

CONCLUSION

The addition of cisatracurium to lidocaine in intravenous regional anesthesia shortened the sensory and motor block onset times, improved the quality of anesthesia, and decreased analgesic requirements without causing clinical side effects.

Acute desflurane or sevoflurane exposure on a previously stabilized atracurium-induced neuromuscular block

BACKGROUND AND OBJECTIVE

The aim of this prospective study was to compare the effect of the administration of desflurane or sevoflurane to a fixed neuromuscular block.

METHODS

After written consent, 12 patients were anaesthetized with propofol and sufentanil. Atracurium was administered via a continuous infusion in order to obtain 85% twitch depression of the control value assessed by repeated accelerometric stimulation at the adductor pollicis. Once stabilized over the course of 30 min, propofol was discontinued and either desflurane (n = 6) or sevoflurane (n = 6) was delivered at 1 MAC in a mixture of 50% O(2) in air. Study parameters were the magnitude and the time of twitch height variations. Results are presented in mean +/- SD.

RESULT

Exposure to halogenated agents led to a significant reduction in twitch height with similar magnitude between the two agents. However, interaction with desflurane showed an initial and transient rise (35 +/- 22%) in twitch height before subsequent depression occurred. The time to reach 50% of the signal depression in the desflurane group was significantly delayed (25 +/- 7 vs. 11 +/- 4 min in the sevoflurane group; P < 0.01).

CONCLUSIONS

On a stable neuromuscular block elicited by continuous infusion of atracurium, the abrupt administration of desflurane or sevoflurane reduces the accelerometric responses of the adductor pollicis in a similar way. This potentiating effect is produced faster after sevoflurane than after desflurane. With desflurane, a biphasic effect (of a transient and moderate increase followed by depression of the signal) was recorded.

Modeling of Twitch Fade Based on Slow Interaction of Nondepolarizing Muscle Relaxants with the Presynaptic Receptors

Nondepolarizing muscle relaxants (MRs) diminish the indirectly evoked single twitch due to their binding to the postsynaptic receptors. Additionally, the MRs produce progressive diminution of successive twitches upon repetitive stimulation (fade). Our study addresses the generation of fade as observed under clinical situation. The study was conducted in two phases. In the clinical part, we have evaluated the time course of twitch depression and fade following the administration of several doses of three MRs (rocuronium, pancuronium, and cisatracurium). In the second part, we have modified our model of neuromuscular transmission to simulate the time course of twitch depression and fade. The MR was assumed to bind to a single site on the presynaptic receptor to produce fade. The rates of interaction with the presynaptic receptors were characterized in terms of the arbitrarily assigned equilibrium dissociation constant and the half-life for dissociation of the presynaptic complex. A method was developed to relate the release of acetylcholine to the occupancy of the presynaptic receptors. The strength of the first and the fourth twitch was calculated from the peak concentration of the activated postsynaptic receptors, i.e., of those receptors with both sites occupied by acetylcholine. Our results indicate that, while the affinity of the MR for the presynaptic receptor plays little role in the time course of fade, the rate of dissociation of the complex between the presynaptic receptors and the muscle relaxant may be critical in determining the time course of fade. Tentative estimates of this parameter are offered.

Cisatracurium: myographical and electrophysiological studies in the isolated rat muscle

Myographical and electrophysiological studies of cisatracurium were performed, in vitro, in the isolated sciatic nerve-extensor digitorum longus muscle preparation of the rat. Indirect twitches were generated at 0.1 Hz and tetanic contractions at 50 Hz. endplate potentials (epps) were generated in trains of 50 Hz. The electrophysiological variables used in the analysis of the epps were: amplitude of the first epp in the train, average amplitude of the 30 degrees to the 59 degrees epp in the train (epps-plateau), tetanic rundown (percent loss in amplitude of epps-plateau relative to the first epp in the train), quantal size and quantal content. The myographical results showed that the inhibitory concentration 50% (IC(50)) of cisatracurium for the blockade of twitches (0.48 microm) is 12 times its IC(50) for the induction of tetanic fade (0.04 microm). The electrophysiological results showed a concentration dependent decrease in the amplitudes of first epps in the trains and of epps-plateau in the two used concentrations (0.13 microm and 0.38 microm). The tetanic rundown was intensified only in the presence of the higher (0.38 microm) concentration of cisatracurium. In cisatracurium 0.13 microm (a concentration which affects only tetanic contractions, inducing their fade, while leaving the twitch unaffected) there was a decrease in the quantal content of the first epp and of epps-plateau in the train. In cisatracurium (0.38 microm), a concentration, which affects the twitch, there was a decrease of the quantal size and of quantal content of epps-plateau, but not of the quantal content of the first epp in the train. The results indicate that the fade of the tetanic contraction induced by cisatracurium at the concentration of 0.13 microm is entirely because of a pre-synaptic blocking effect while the decrease in the twitch induced by cisatracurium at the concentration of 0.38 microm is due to a post-synaptic blocking effect.

[Intracranial pressure response during secretion aspiration after administration of a muscle relaxant]

Aspiration of secretions is a usual nursing technique in patients undergoing mechanical ventilation that may be the cause of increased Intracranial Pressure (ICP).

OBJECTIVE

This study aims to evaluate the repercussion of a muscle relaxant on ICP with secretion aspiration.

METHOD

Clinical trial using the same patient as case and control, performing two endotracheal aspirations in each patients, on of them after administration of a muscle relaxant (Cis-Atracurium) and another no. The bolus administration of the relaxant in the first or second aspiration was done randomly. Thirteen patients with intraparenchymatous ICP measurement catheter were studied within the first 36 hours post-placement and with sedoanalgesia for a score of 6 on the Ramsay scale. ICP and CPP were measured before, during and after each aspiration.

STATISTICAL METHOD

SPSS 11.0 program was used. Data analysis by Student's t test for paired data. Statistical significance level accepted was 95%.

RESULTS

On comparing the cases in which muscle relaxant was administered with those in which it was not administered, statistically significant differences were found in the ICP and CCP values during secretion aspiration.

CONCLUSIONS

According to the data obtained in the study, a lower increase of ICP was observed during secretion aspiration in those cases in which muscle relaxant was administered prior to the aspiration.

The Influence of a Muscle Relaxant Bolus on Bispectral and Datex-Ohmeda Entropy Values During Propofol-Remifentanil Induced Loss of Consciousness

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

Nitric oxide is not a mediator of inflammation-induced resistance to atracurium

Resistance to atracurium as a result of increased drug binding to alpha1-acid glycoprotein is associated with increased inducible nitric oxide synthase activity and increased nitric oxide levels in plasma. We investigated if the inhibition of inducible nitric oxide synthase and suppression of nitric oxide can reverse the resistance to atracurium. As a model of alpha1-acid glycoprotein and nitric oxide increase, 84 male Sprague-Dawley rats received an IV injection of either 60 mg/kg Corynebacterium parvum (CP) or saline (control). The 2 groups (CP/Control) were further divided into subgroups, receiving the selective inducible nitric oxide synthase inhibitor, N-Iminolysine, via drinking water at different concentrations. On day 4 post-CP injection, the pharmacodynamics of atracurium were determined. Plasma concentrations of nitric oxide, atracurium, and alpha1-acid glycoprotein were measured and acetylcholine receptor numbers were quantified. In the CP groups, N-Iminolysine suppressed nitric oxide levels in a dose-dependent manner. Resistance to atracurium persisted. alpha1-acid glycoprotein serum levels remained increased in all CP groups with no differences in acetylcholine receptor expression. Our results suggest that the mechanism leading to increased expression of alpha1-acid glycoprotein and consecutive increased protein binding of atracurium is not mediated by inducible nitric oxide synthase induction and nitric oxide expression.

Does pancuronium or cisatracurium delay the rate of arousal following remifentanil-based anesthesia?

STUDY OBJECTIVE

The present report investigates the rate of arousal following remifentanil-based anesthesia associated with the coadministration of pancuronium, which inhibits butyrylcholinesterase, or cisatracurium, which is partially metabolized by nonspecific esterases, versus vecuronium that is eliminated independently of ester hydrolysis.

DESIGN, SETTING AND PATIENTS

Sixty patients, ASA I-II, scheduled for elective abdominal surgeries were enrolled in a double-blinded prospective study. In fact, patients were equally divided into three Groups with each Group receiving remifentanil and either one of the following three muscle relaxants: pancuronium, vecuronium or cisatracurium.

MEASUREMENTS

The rate of arousal following discontinuation of anesthesia was assessed by Modified Aldrete Score. Time to eye opening on verbal command, tracheal extubation, Modified Aldrete Score >9, and time to discharge from the recovery room were recorded.

MAIN RESULTS

Time to eye opening on verbal command, tracheal extubation, Modified Aldrete Score >9, and time to discharge from the recovery room were not significantly different between the three groups.

CONCLUSION

The results suggest that recovery following remifentanil-based anesthesia is not delayed by the coadministration of pancuronium, cisatracurium versus vecuronium; and by the use of neostigmine for reversal of neuromuscular blockade.

Neuromuscular blocking properties of atracurium during sevoflurane or propofol anaesthesia in dogs

OBJECTIVE

To quantify the neuromuscular blockade (NMB) produced by atracurium in either sevoflurane or propofol-anaesthetized dogs.

ANIMALS

Twelve healthy, female adult mixed-breed dogs weighing 13 +/- 3 kg (range 10-22 kg).

MATERIALS AND METHODS

Three doses of atracurium (0.1, 0.2 and 0.3 mg kg(-1)) were tested at 1-week intervals. Anaesthesia was induced with inhaled sevoflurane or intravenous propofol and maintained with end-tidal sevoflurane concentrations of 1.95% (1.25 x MAC) or propofol 0.6 mg kg(-1) minute(-1) respectively. Acceleromyography and train-of-four stimulation of the fibular nerve were used for the assessment of NMB. The percentage depression of the first twitch (T1) and the fourth to the first twitch ratio (T4/T1), the maximum degree of neuromuscular block achieved and surgical muscle relaxation were recorded. Before and during neuro muscular blockade (at 10 minute intervals) body temperature, ECG, arterial blood pressure, inspired and expired CO2 concentrations and SpO2 were recorded.

RESULTS

Atracurium produced a dose-dependent duration of NMB in both propofol and sevoflurane-anaesthetized dogs. Duration of block was longer in dogs anaesthetized with sevoflurane. All studied doses of atracurium caused twitch depression > or =95% with little or no cardiovascular changes.

CONCLUSIONS

Sevoflurane produces a clinically relevant potentiation of atracurium-induced NMB in dogs compared with propofol.

CLINICAL RELEVANCE

Significant differences in the potentiation of NMB drugs are encountered with commonly used anaesthetics in the dog.

Cisatracurium, but not mivacurium, induces apoptosis in human umbilical vein endothelial cells in vitro

BACKGROUND AND OBJECTIVE

Cisatracurium is an intermediate acting, non-depolarizing neuromuscular blocking agent. Previous reports have indicated a growth-inhibitory effect of the isoforms cisatracurium and atracurium on two human cell lines in vitro. These effects were ascribed to oxidative stress elicited by acrylate esters formed during cisatracurium breakdown. Oxidative stress is a potent precipitator of apoptosis. Therefore, the aim of the present study was to investigate whether the growth-inhibitory effects of cisatracurium could be explained by initiation of apoptosis.

METHODS

Human umbilical vein endothelial cells were incubated with cisatracurium at concentrations of 0.96, 3.2, 9.6, 32 and 96 micromol for 24 h. DNA fragmentation was measured using the Cell Death Detection ELISA Plus assay (Roche Diagnostics, Mannheim, Germany).

RESULTS

There was a dose dependency of cisatracurium with respect to the rate of apoptosis in human umbilical vein endothelial cells. Programmed cell death could be demonstrated at concentrations encountered in human plasma after single-bolus injections of cisatracurium. Apoptosis was attenuated by the concomitant administration of glutathione.

CONCLUSIONS

These findings strongly support the hypothesis that acrylate esters, breakdown products of cisatracurium, induce oxidative stress and, subsequently, apoptosis.

Antagonism of neuromuscular blockade but not muscle relaxation affects depth of anaesthesia

BACKGROUND

Conflicting effects of neuromuscular blocking drugs and anticholinesterases on depth of anaesthesia have been reported. Therefore we evaluated the effect of atracurium and neostigmine on bispectral index (BIS) and middle-latency auditory evoked potentials (AAI).

METHODS

We studied 40 patients (ASA I-II) aged 18-69 yr. General anaesthesia consisted of propofol and remifentanil by target-controlled infusion and neuromuscular function was monitored by electromyography. When BIS reached stable values, patients were randomly assigned to one of two groups. Group 1 received atracurium 0.4 mg kg(-1) and, 5 min later, the same volume of NaCl 0.9%; group 2 received saline first and then atracurium. When the first twitch of a train of four reached 10% of control intensity, patients were again randomized: one group (N) received neostigmine 0.04 mg kg(-1) and glycopyrrolate 0.01 mg kg(-1), and the control group (G) received only glycopyrrolate.

RESULTS

Injection of atracurium or NaCl 0.9% had no effect on BIS or AAI. After neostigmine-glycopyrrolate, BIS and AAI increased significantly (mean maximal change of BIS 7.1 [SD 7.5], P<0.001; mean maximal change of AAI 9.7 [10.5], P<0.001). When glycopyrrolate was injected alone BIS and AAI also increased (mean maximal change of BIS 2.2 [3.4], P=0.008; mean maximal change of AAI 3.5 [5.7], P=0.012), but this increase was significantly less than in group N (P=0.012 for BIS; P=0.027 for AAI).

CONCLUSION

These data suggest that neostigmine alters the state of propofol-remifentanil anaesthesia and may enhance recovery.

Variability of duration of action of neuromuscular-blocking drugs in elderly patients

BACKGROUND

Steroid-based, non-depolarizing neuromuscular-blocking (NMB) drugs (e.g. rocuronium, vecuronium) are characterized by organ-dependent elimination and significantly longer durations of action in elderly compared to young patients. Cisatracurium is a benzylisoquinolinium NMB drug with a duration of action not altered by ageing. The objective of the study was to determine if elderly patients had less variability in duration of action with 2 x ED95 of cisatracurium compared to equipotent doses of rocuronium or vecuronium.

METHODS

Informed consent was obtained from 66 elderly patients with normal renal and liver function. Preoperative midazolam (1 mg) was given IV. The anaesthestic induction was with 5 mg kg(-1) thiopental and 2 microg kg(-1) fentanyl. The patients received 0.6 mg kg(-1) rocuronium, 0.1 mg kg(-1) vecuronium or 0.1 mg kg(-1) cisatracurium. Anaesthetic maintenance was with sevoflurane in oxygen/nitrous oxide. Neuromuscular-blocking duration of action was defined as the return of T1 twitch height to 25% of control. Variability was determined by subtracting the actual duration of action from the mean duration of action for each drug.

RESULTS

The durations of action (range, min) were: cisatracurium, 37-81; vecuronium, 35-137; and rocuronium, 33-119. The median of the variability of duration was significantly less with cisatracurium (7 min) compared to vecuronium (18 min) and rocuronium (18 min) (P < 0.05).

CONCLUSION

When used with sevoflurane/N(2)O, there was a two-fold greater variability of duration of neuromuscular blockade in elderly patients receiving rocuronium or vecuronium compared with cisatracurium.

Assessment of neuromuscular and haemodynamic effects of cisatracurium and vecuronium under sevoflurane-remifentanil anaesthesia in elderly patients

BACKGROUND AND OBJECTIVE

Neuromuscular block times, quality of muscle relaxation for tracheal tube insertion, and the haemodynamic effects after cisatracurium and vecuronium under sevoflurane-remifentanil anaesthesia were compared in elderly patients.

METHODS

The study was performed in 40 patients over 65 yr of age. Anaesthesia was induced with thiopental, and maintained with sevoflurane in N2O/O2 and remifentanil. Cisatracurium 0.15 mg kg(-1) or vecuronium 0.1 mg kg(-1) were administered after induction. Intubation was attempted when neuromuscular block was 95%. Onset time, clinical duration of action, recovery index, spontaneous recovery time and tracheal intubation conditions were assessed. Haemodynamic parameters were also monitored.

RESULTS

The average ages of the patients were 72.5 +/- 5.1 and 73.6 +/- 6.3 in the cisatracurium and vecuronium groups, respectively. Onset time was significantly shorter after vecuronium, 158 +/- 34 s vs. 200 +/- 50s, respectively. Recovery index was significantly shorter after cisatracurium, 19.5 +/- 7.5 s vs. 33.7 +/- 18.6 s (P < 0.05). Clinical duration and spontaneous recovery time were similar in both groups as well as haemodynamic variables.

CONCLUSIONS

In elderly patients, vecuronium has a faster onset time while cisatracurium has a shorter recovery index under sevoflurane-remifentanil anaesthesia.

Cisatracurium-Induced Neuromuscular Blockade Is Affected by Chronic Phenytoin or Carbamazepine Treatment in Neurosurgical Patients

The effect of chronic anticonvulsant therapy (CAT) on the maintenance and recovery profiles of cisatracurium-induced neuromuscular blockade has not been adequately studied. In this study, we compared the pharmacokinetics and pharmacodynamics of cisatracurium after a prolonged infusion in patients with or without CAT. Thirty patients undergoing intracranial surgery were enrolled in the study: 15 patients under CAT (carbamazepine and phenytoin, Group A) and 15 controls receiving no anticonvulsant therapy (Group C). Anesthesia was standardized and both groups received a bolus of cisatracurium followed by an infusion to maintain a 95% twitch depression. A steady-state was obtained and the infusion was kept constant for 2 additional hours. Neuromuscular blockade was then allowed to spontaneously recover. Blood samples were taken for measurement of cisatracurium plasma concentration during the steady-state period (Cp(ss)95) and at various times during recovery. Demographic and intraoperative data were similar. CAT resulted in faster 25% and 75% recovery of the first twitch. The rate of infusion of cisatracurium needed to maintain a 95% twitch depression at steady-state was 44% faster in Group A (P < 0.001). The clearance of cisatracurium was significantly faster in Group A when compared with Group C (7.12 +/- 1.87 versus 5.72 +/- 0.70 L . kg(-1) . min(-1), P = 0.01). The Cp(ss)95 was also significantly larger in Group A (191 +/- 45 versus 159 +/- 36 ng/mL, P = 0.04). In addition, patients receiving CAT had a 20% increase in the clearance of cisatracurium that, in turn, resulted in a faster recovery of neuromuscular blockade after an infusion of the drug. Also, patients under CAT had a 20% increase in their Cp(ss)95, indicating an increased resistance to the effect of cisatracurium.

[Interaction between vecuronium and atracurium revisited by adapting an alternative method]

OBJECTIVES

Given that contradictory conclusions about the interaction between vecuronium and atracurium have been reached by previous investigators, the present study used an alternative method to analyze this interaction by way of the respective potencies of the two agents and the potency of their combination.

PATIENTS AND METHODS

Effective doses for each relaxant were first calculated by administering small amounts of the agents to 3 similar groups of patients anesthetized with intravenous drugs and ventilated with nitrous oxide. Depression of the first response to train-of-four stimulation was obtained during electromyographic monitoring. That information was used to estimate the mean potency for each individual by an alternative method based on prior knowledge of the slope of the dose-response curve. In another group of patients, fractions equipotent to the median effective dose (ED50) were administered and the same procedure was used to establish the theoretical and calculated potencies of fractionated doses. The algebraic sum of the ratios between the calculated and effective doses was used to define the type of interaction.

RESULTS

The ED50 and the doses giving 90% and 95% efficacy were 24, 38 and 45 microg x Kg(-1) for vecuronium and 144, 234 and 277 microg x Kg(-1) for atracurium. After combination, the new figures were 9, 14 and 17 microg x Kg(-1) for vecuronium and 57, 93 and 110 microg x Kg(-1) for atracurium. The algebraic sums of the ratios between calculated and effective doses were less than 1 for each level of effective dose (0.77, 0.76 and 0.77, respectively), denoting synergism.

CONCLUSIONS

The alternative method presented for analyzing the potency of the individual components of the vecuronium-atracurium interaction demonstrated that their effect is greater after combination and definitively synergistic.