Smoking increases the requirement for rocuronium

Purpose

To compare the potency of rocuronium in non-smokers and smokers during general anaesthesia.

Methods

In a randomized, open clinical study, 40 patients, 17–62 yr of age, were anaesthetized with propofol, alfentanil and nitrous oxide in oxygen. After obtaining individual dose-response curves for rocuronium, bolus doses of rocuronium were given to maintain neuromuscular block at 90–99% for 60 min. Evoked adductor pollicis electromyography (EMG) was used to monitor neuromuscular block.

Results

The ED₉₅ values (± SEM) for rocuronium were 460.5 ± 28.9 and 471.5 ± 22.1 μg·kg^?1 for nonsmokers and smokers, respectively (P:NS). However, doses of rocuronium to maintain 90–99% neuromuscular block (± SEM) were 620.1 ± 46.7 and 747.4 ± 56.0 μg·kg^?1·hr^?1 for non-smokers and smokers, respectively (P = 0.0504).

Conclusion

The results may indicate increased metabolism of rocuronium in smokers rather than increased requirement of rocuronium at the receptor site.     

Neuromuscular blocking effects of rocuronium during desflurane, isoflurane, and sevoflurane anaesthesia

Purpose

To determine the magnitude of the potentiation of rocuronium by desflurane, isoflurane and sevoflurane 1.5 MAC anaesthesia.

Methods

In a prospective, randomised, study in 80 patients, the cumulative dose-effect curves for rocuronium were determined during anaesthesia with desflurane, sevoflurane and isoflurane (with N₂O 70%, 15 min steady state) or total intravenous anaesthesia (TIVA) using propofol/fentanyl. Neuromuscular block was assessed by acceleromyography (TOF-Guard®) after train-of-four (TOF) stimulation of the ulnar nerve (2Hz every 12sec, 200 μsec duration), Rocuronium was administered in increments of 100 μg·kg^?1 until first twitch (T₁) depression > 95%.

Results

Rocuronium led to more pronounced T₁ depression with desflurane or sevoflurane anaesthesia than with TIVA. The ED₅₀ and ED₉₅ were lower during desflurane (95 ± 25 and 190 ± 80 μg·kg^?1) and sevoflurane (120 ±30 and 210 ± 40 μg·kg^?1) than with TIVA (150 ± 40 and 310 ± 90 μg·kg^?1) (P < .01), while the difference was not significant for isoflurane (130 ± 40 and 250 ± 90 μg·kg^?1). Following equi-effective dosing (T₁ > 95%) the duration to 25% T₁ recovery, recovery index (25/75), and TOF_0.70 was: 13.2 ± 1.8, 12.7 ± 3.4, and 26.9 ± 5.7 min during anaesthesia with desflurane; 15.5 ± 5.0, 11.4 ± 3.8, and 31.0 ± 6.0 min with sevoflurane; 13.9 ± 4.7, 10.7 ± 3.3, and 26.3 ± 8.9 min with isoflurane; and 13.9 ± 3.9, 11.3 ± 5.7, and 27.5 ± 8,2 min with TIVA anaesthesia (P: NS).

Conclusion

Interaction of rocuronium and volatile anaesthetics resulted in augmentation of the intensity of neuromuscular block but did not result in significant effects on duration of or recovery from the block.     

Comparison of neuromuscular effects, efficacy and safety of rocuronium and atracurium in ambulatory anaesthesia

Purpose

To compare the neuromuscular effects, efficacy, and safety of equi-effective doses of rocuronium and atracurium in ambulatory female patients undergoing surgery.

Methods

Forty-one patients undergoing laparoscopic gynaecological surgery were randomized to receive 2 × ED₉₀ rocuronium (0.6 mg·kg^?1; n = 20) or atracurium (0.5 mg·kg^?1; n = 21) during intravenous propofol/alfentanil anaesthesia with N₂O/O₂ ventilation. Neuromuscular block was measured with a mechanomyogram eliciting a train-of-four (TOF) response at the wrist. Intubation conditions 60 sec after administration of muscle relaxant and immediate cardiovascular disturbances or adverse events during the hospital stay were noted by blinded observers.

Results

Compared with atracurium, rocuronium was associated with a shorter onset time (59.0 ± 22.2vs 98.6 ± 41.4 sec;P < 0.001) and clinical duration of action (33.3 ± 7.1vs 44.7 ± 7.2 min;P < 0.001), but longer spontaneous recovery index (9.6 ± 2.41vs 6.9 ± 1.89 min;P = 0.023) and a similar time to spontaneous recovery to TOF 70%; 53 ± 6.31vs 59.2 ± 7.59 min;P =0.139). Tracheal intubation was accomplished in < 90 sec in all patients receiving rocuronium but in only 14 of 21 patients receiving atracurium. The incidence of adverse events and the cardiovascular profiles for the two drugs were similar, although one patient receiving atracurium experienced transient flushing of the head and neck.

Conclusion

Rocuronium has minimal side effects, provides conditions more suitable for rapid tracheal intubation, and is associated with a shorter clinical duration than atracurium. Once begun, the spontaneous recovery profile of rocuronium is slightly slower than that of atracurium.     

Pharmacodynamics of doxacurium during cardiac surgery with hypothermic cardio-pulmonary bypass

Purpose

To determine the characteristics of neuromuscular block produced by two and three times the 95% effective dose (ED₉₅) of doxacurium in patients undergoing coronary artery surgery with hypothermic cardiopulmonary bypass.

Methods

In a prospective non randomized study, ten patients received doxacurium 0.05 mg·kg^?1 (Group 1) and ten others received 0.075 mg · kg^?1 (Group 2) with midazolam and sufentanil. The mechanomyographic response of the adductor pollicis muscle after supramaximal train-of-four (TOF) stimulation of the ulnar nerve was recorded intraoperatively and postoperatively. Additional doxacurium (10% of the initial dose) was administered until sternal closure whenever the first twitch (T₁) had recovered to 25% of control.

Results

The onset time (time to maximal T₁ depression) of doxacurium was 390 ± 148 sec in Group 1 and 370 ± 74 sec in Group 2 (P = 0.71). The clinical duration of neuromuscular block (time to 25% T₁ recovery) was 165 ± 90 min in Group 1 and 258 ± 86 min in Group 2 (P = 0.03). On arrival to recovery room the mean T₁ was 57 ± 23% in Group 1 and 24 ± 21% in Group 2(P = 0.003); the mean T₄/T₁ ratio was 0.25 ± 0.15 for five patients of Group 1 with four responses to TOF stimulation and 0.10 for the only patient of Group 2 with four twitches.

Conclusion

In contrast with findings in patients without cardiac disease, this study shows comparable onset times of doxacurium with doses of two and three times ED₉₅. The clinical duration of doxacurium is 60 to 100% longer than previously reported in noncardiac surgery.     

Early neuromuscular recovery characteristics following administration of mivacurium plus vecuronium

Purpose

This study was designed to describe the early recovery characteristics, as well as the speed of onset of neuromuscular block, after a combination of mivacurium and vecuronium.

Methods

In this controlled, randomized study, 30 consenting ASA I–III patients were assigned to three treatment groups. The “2M2V” group received twice the dose necessary to cause 95% depression of the evoked twitch response (2 × ED₉₅) of mivacurium (0.15 mg · kg^?1) plus 2 × ED₉₅ of vecuronium (0.1 mg · kg^?1); the “2V” group received 2 × ED₉₅ of vecuronium; and the “4V” group received 4 × ED₉₅ of vecuronium. Evoked neuromuscular responses of the adductor pollicis were assessed with an adductor pollicis force transducer. The time until maximum block and times to 10% and 25% recovery (T₁₀ and T₂₅) in each group were expressed as mean ± standard deviation and compared using ANOVA.

Results

Onset of block in the 2M2V group was 27% faster than in the 2V group (2.0 ± 0.6 vs. 2.7 ± 0.8 min respectively, P < 0.05) and was similar to the 4V group (1.95 ± 0.3 min, P = NS). The times until 10% recovery were similar in the 2M2V and 4V groups (59.9 ± 12 vs 68.2 ± 25 min, P = NS) and were slower than in the 2V group (37.2 ± 9 min, P < 0.05). Between T₁₀ and T₂₅, recovery after 2M2V resembled that after 2V (6.7 ± 3 vs 5.7 ± 1 min, P = NS) and was faster than after 4V (10.9 ± 7 min, P<0.05).

Conclusions

When 2 × ED₉₅ of mivacurium is added to 2 × ED₉₅ of an intermediate or long-acting relaxant, recovery after T₁₀ will proceed as if one had administered the longeracting agent alone.     

Residual neuromuscular blockade after cardiac surgery: pancuroniumvs rocuronium

Purpose

To determine the incidence of residual neuromuscular blockade after cardiac surgery in patients receiving either rocuronium or pancuronium for muscle relaxation.

Methods

In a prospective, controlled, double-blind study, 20 patients undergoing coronary artery bypass were randomized to receive either rocuronium (n= 10) or pancuronium (n = 10) dunng surgery. Anaesthesia was induced with sufentanil, benzodiazepine and propofol or ketamine, and maintained with air/O₂/sufentanil/isoflurane. Neuromuscular blockade was induced with 0.1 ml·kg^?1 from blinded synnges containing rocuronium (6 mg·ml^?1) (Group R) or pancuronium (I mg·ml^?1) (Group P). Relaxants were administered according to clinical criteria and reversal agents were not given. After surgery, neuromuscular transmission was assessed by train-of-four stimulation of the ulnar nerve/adductor pollicis EMG (Datex Relaxograph). Mean values from three trains of stimuli were recorded and repeated 30 min later if TOF ratio was < 0.7. Time to extubation was recorded.

Results

On arrival in the ICU, nine of 10 patients in group R but only three of 10 patients in group P demonstrated four visible responses (P < 0.05). Mean TOF ratio in group P, 0.03 ± 0.05, was less than in group R, 0.68 ± 0.34 (P < 0.001). All patients in group P and 4 of 10 patients in group R had TOF ratio < 0.7 (P = 0.01). Time to extubation in group P (median 18, range 6–48 hr) was not statistically different from that in group R (14, 5–44 hr).

Conclusion

Residual neuromuscular block, TOF ratio < 0.7, is common after cardiac surgery but the incidence is less when pancuronium is replaced by rocuronium.     

Epinephrine decreases the dose of hyperbaric bupivacaine necessary for tourniquet pain blockade during spinal anesthesia for total knee replacement arthroplasty

Purpose

We quantified the dose-sparing effect of epinephrine by comparing the median effective dose (ED₅₀) of intrathecal hyperbaric bupivacaine co-administered with epinephrine with the ED₅₀ of intrathecal hyperbaric bupivacaine alone.

Methods

Three groups were randomly generated from 162 patients undergoing total knee replacement arthroplasty under combined spinal and epidural anesthesia: Group B (bupivacaine), Group BE1 (bupivacaine plus epinephrine 100 μg), and Group BE2 (bupivacaine plus epinephrine 200 μg). Each group was further divided by bupivacaine doses of 6, 7, 8, 9, 10, or 11 mg. The anesthesia was defined as successful if a bilateral T12 sensory block occurred within 15 min, and no intraoperative epidural supplement was required. The ED₅₀ and ED₉₅ for successful anesthesia and successful tourniquet pain blockade were determined separately by probit regression analysis.

Results

The ED₅₀ and ED₉₅ of intrathecal hyperbaric bupivacaine for successful anesthesia were not different among the groups: the ED₅₀ values were 7.1 mg [95 % confidence interval (95 % CI) 6.0–8.0 mg] in Group B, 6.2 mg (95 % CI 4.8–7.2 mg) in Group BE1, and 6.3 mg (95 % CI 4.9–7.2 mg) in Group BE2. However, the ED₅₀ and ED₉₅ values for tourniquet pain control were significantly smaller in Groups BE1 and BE2 than in Group B: the ED₅₀ values were 7.2 mg (95 % CI 6.3–7.9 mg), 5.5 mg (95 % CI 4.1–6.3 mg), and 5.3 mg (95 % CI 3.7–6.2 mg) in Groups B, BE1, and BE2, respectively. The incidence of tourniquet pain was significantly lower in Groups BE1 and BE2 than in Group B. The time to patients’ requests for supplemental analgesia was significantly longer in Groups BE1 and BE2 than in Group B.

Conclusions

Intrathecal epinephrine did not decrease the dose of intrathecal hyperbaric bupivacaine required for successful anesthesia. However, it reduced the dose required for tourniquet pain blockade.     

Intubationsbedingungen und Verlauf der neuromuskulären Blockade nach Rocuronium bei endoskopischen Operationen in der HNO-Heilkunde

Rocuronium is a new nondepolarizing muscle relaxant for which a fast onset has been described. The goal of this study was to examine whether the characteristics of rocuronium could make it an appropriate relaxant for the anaesthetic management of operations of intermediate duration such as endoscopic upper airway surgery. These operations, which require the anaesthesiologist and surgeon to ”share” the patient’s airway, require good muscle relaxation for endotracheal intubation and placement of endoscopic instruments. In addition, the time course of neuromuscular blockade and its relation to the quality of intubating conditions were analysed. Methods: The study was approved by the local ethics committee; 30 patients (ASA status 1–3) scheduled for elective endoscopic upper airway surgery were included after written informed consent. Exclusion criteria were suspected difficult intubating conditions, neuromuscular disease, or antibiotic therapy with aminoglycosides during the last 24?h. Anaesthesia was induced by propofol 2?mg/kg and alfentanil 1?mg after volume loading with 500?ml Ringer’s lactate and preoxygenation, and was maintained by propofol infusion 5–8?mg/kg/h and repetitive alfentanil injections according to clinical needs. Endotracheal intubation was performed by a senior anaesthesiologist 90?s after injection of rocuronium 0.6?mg/kg (2×ED₉₅). Intubating conditions were graded 1 to 4 (1=excellent, 2=good, 3=sufficient, 4=inadequate). Acceleromyography was used for neuromuscular monitoring by means of the TOF-guard (Organon Teknika/Biometer). The adduction movement of the thumb was measured by an acceleration transducer while stimulating the ulnar nerve at the wrist via surface electrodes in a supramaximal train-of-four (TOF) mode (2?Hz every 15?s). Twitch height and TOF ratio were documented during the course of neuromuscular blockade. Data are presented as mean±standard deviation. Results: Patients were aged 37 to 64 years (mean 54±7). Intubating conditions were excellent in 17 cases and good in 7. In 2 cases intubating conditions were graded sufficient, as patients could be easily intubated but showed clear diaphragmatic movements at intubation. In 4 patients intubating conditions could not be judged, as a laryngoscopic view of the glottic structures was impossible for anatomic reasons. Neuromuscular block at intubation was 78±22%, onset time 152±62?s, clinical duration 30±8?min, and recovery index 11±4?min. The TOF ratio required 51±14?min to return to 0.7. Conclusions: Good to excellent intubating conditions can be expected 90?s after injection of rocuronium 0.6?mg/kg. Diaphragmatic reactions cannot be excluded. Complete relaxation of the adductor pollicis muscle is not necessary for endotracheal intubation. Intubation at a certain time interval, for example, 90?s after injection of rocuronium 0.6?mg/kg, can be recommended. Onset and recovery characteristics of rocuronium make it an appropriate relaxant for the anaesthetic management of operations of intermediate duration such as endoscopic upper airway surgery. Care should be given, however, to detect inadequate recovery of neuromuscular transmission, as there are considerable interindividual differences in recovery.     

ED50 and ED90 of intrathecal hyperbaric 2% prilocaine in ambulatory knee arthroscopy

Purpose

Hyperbaric 2% prilocaine (HP) is increasingly used for spinal anesthesia in day-case surgery. The aim of this prospective double-blind study was to determine the effective dose (ED)₅₀ and the ED₉₀ of HP for patients undergoing knee arthroscopy.

Methods

Doses of HP were determined using an up-and-down sequential allocation technique. Sequences were analyzed by isotonic regression analysis. A subsequent observational study was performed with the calculated ED₉₀ in 50 patients to confirm the initial result and to describe the induced blockade effects and side effects. Times corresponding to onset and duration of sensory and motor block, surgical data, and side effects were recorded.

Results

The ED₅₀ was estimated at 28.9 mg (95% confidence interval [CI]: 26.5 to 35.3) and the ED₉₀ was estimated to be 38.5 mg (95% CI: 35.7 to 39.5). A 40 mg dose of HP provided efficient anesthesia in 46 patients (92%, 95% CI: 82 to 98). The average (SD) time to effective anesthesia was 14.5 (3.9) min. Complete sensory block at level T12 was obtained after ten minutes in 44 of 50 patients. The average (SD) duration of the sensory block was 205 (36.1) min. Maximal level of sensory block was obtained at the T8-T11 levels in 41 of 50 patients without hemodynamic instability. A Bromage 3 score was obtained in 40 of the 46 patients who achieved successful anesthesia after 30 min. Patients did not experience urinary retention, nor were any signs of transient neurologic symptoms observed.

Conclusion

This study determined the ED₅₀ of HP is 28.9 mg and suggests that a 40-mg dose of HP is adequate to provide successful spinal anesthesia for outpatient knee arthroscopy.     

Monitoring of neuromuscular blockade in one muscle group alone may not reflect recovery of total muscle function in patients with ocular myasthenia gravis

Purpose

We report on two patients with ocular myasthenia gravis who received rocuronium, followed later by sugammadex to reverse neuromuscular blockade. Recovery was monitored simultaneously at the adductor pollicis muscle (APM) and the corrugator supercilii muscle (CSM).

Clinical features

Two patients with ocular myasthenia gravis (case 1: 74 yr-old female, 54 kg; case 2: 71 yr-old male, 72 kg) were scheduled for surgery under general anesthesia. Neuromuscular blockade was induced with rocuronium 0.3 mg·kg^?1 after placing two separate monitors at the APM and the CSM, respectively. Additional doses of rocuronium 0.1-0.2 mg·kg^?1 were given to maintain neuromuscular blockade at fewer than two twitches at the APM during surgery. Train-of-four response at the CSM did not show recovery of the twitch after its initial disappearance. At the end of surgery, sugammadex was administered. Twitch height at the APM recovered to the control value in 12 min (case 1) and 13 min (case 2) after sugammadex administration; however, twitch height at the CSM took 26 min (case 1) and 14 min (case 2) to recover to the control value.

Conclusion

After rocuronium-induced paralysis in both patients with ocular myasthenia, spontaneous recovery and sugammadex-assisted recovery were slower at the CSM than at the APM. In patients without the disorder, CSM recovery is faster than APM recovery. Thus, in ocular myasthenia gravis, neuromuscular recovery at the APM may not reflect recovery of all muscles.     

Ketamine, but not priming, improves intubating conditions during a propofol–rocuronium induction

Purpose

Both ketamine and priming may shorten the onset time of rocuronium. This study investigates the effects of ketamine and priming as components of a propofol induction on intubating conditions and onset of neuromuscular block.

Methods

This prospective randomized double-blind study was performed in 120 American Society of Anesthesiologists (ASA) I–II patients who were assigned to one of four groups of 30 patients each: control, priming, ketamine, and ketamine-priming. Ketamine 0.5 mg ? kg^?1 or saline was given before priming and induction. Rocuronium 0.06 mg ? kg^?1 or saline was injected 2 min before propofol 2.5 mg ? kg^?1. This was followed by rocuronium 0.6 mg ? kg^?1 or by rocuronium 0.54 mg ? kg^?1 if priming was given. Intubation was performed one minute later. Intubating conditions were graded as excellent, good, or poor. Heart rate, noninvasive blood pressure, and train-of-four (TOF) response were monitored.

Results

Intubating conditions were graded excellent in 20% of the control group, 30% of the priming group, 47% of the ketamine group, and 57% of the ketamine-priming group. Analysis using forward stepwise regression indicated that ketamine improved intubating conditions (P = 0.001) but priming did not (P = 0.35). Time to reach a TOF count of zero was shortened by ketamine (P = 0.001) but not by priming (P = 0.94): 216 ± 20 s in the control group, 212 ± 27 s in the priming group, 162 ± 18 s in the ketamine group, and 168 ± 22 s in the ketamine-priming group.

Conclusion

A low-dose ketamine used with a propofol–rocuronium induction improved intubating conditions and shortened onset time. Priming did not influence intubating conditions or onset time.     

Effect of lung-protective ventilation-induced respiratory acidosis on the duration of neuromuscular blockade by rocuronium

Purpose

The purpose of this study was to elucidate whether lung-protective ventilation-induced respiratory acidosis increased the duration of neuromuscular blockade by rocuronium.

Methods

A total of 72 patients were enrolled. After the induction of general anesthesia, rocuronium 0.6 mg/kg real body weight was administered. Tidal volume and positive end-expiratory pressure were randomly assigned as either 10 ml/kg predicted body weight and 0 cmH₂O (group S) or 6 ml/kg and 5 cmH₂O (group L), respectively. Respiratory rate was started at 10/min. Neuromuscular blockade was monitored by acceleromyography at the adductor pollicis with train-of-four stimulation. The time from the initial bolus injection of rocuronium to first recovery of the first twitch was defined as DUR1. Immediately, rocuronium 0.15 mg/kg was administered. The time from first recovery of the first twitch to second recovery of the first twitch was defined as DUR2. We also measured arterial pH (pH1 and pH2, respectively).

Results

Data from 66 patients (33 each in groups L and S) were eventually available. pH1 and pH2 were significantly lower in group L compared with group S [pH1: 7.308 (7.288–7.334) vs. 7.439 (7.423–7.466); p < 0.01, pH2: 7.306 (7.285–7.330) vs. 7.453 (7.436–7.476); p < 0.01]. DUR1 and DUR2 were significantly prolonged in group L compared with group S [DUR1: 31 (24–36) vs. 24 (20–30) min; p = 0.029, DUR2: 19 (15–22) vs. 15 (12–17) min; p = 0.020].

Conclusions

Lung-protective ventilation-induced respiratory acidosis increased the duration of neuromuscular blockade by rocuronium.

     

Sevoflurane and isoflurane impair edrophonium reversal of vecuronium-induced neuromuscular block

Purpose

A dose-response relationship study for edrophonium to examine the modification of volatile anaesthetics on reversal of vecuronium block.

Methods

One hundred and twenty ASA (I–II) patients were anaesthetized with sevoflurane, isoflurane (I minimum alveolar anaesthetic concentration [MAC] end-tidal concentration), or fentanyl-diazepam anaesthesia, in combination with 66% nitrous oxide (n = 40 for each group). The evoked electromyogram (EMG) response of the abductor digiti minimi was monitored at 20 sec intervals following train-of-four (TOF) stimulation of the ulnar nerve. The initial neuromuscular block was produced by vecuronium 100 μg · kg^?1. When the amplitude of the first response (T₁) had spontaneously recovered to 10% of the control, edrophonium (0, 125, 400, 700 or 1000 μg · kg^?1; eight patients each) was randomly administered, and the ratio of the fourth TOF to the first response (TOFR ) was monitored at one minute intervals for 10 min.

Results

Sevoflurane and isoflurane impaired the edrophonium-assisted TOFR recovery in an edrophonium dose and time dependent manner. The dose-response curves at 10 min exhibited a greater shift to the right in the sevoflurane and isoflurane groups than in the fentanyl-diazepam-nitrous oxide group (P < 0.05). Higher ED₅₀ values (the edrophonium dose required to obtain TOFR value of 50%) in the sevoflurane (> 1000 μg · kg^?1) and isoflurane groups (851 · μg · kg^?1) were observed than in the fentanyl-diazepam-nitrous oxide group (339 μg · kg^?1) (P < 0.05).

Conclusion

One MAC sevoflurane and isoflurane anaesthesia impair edrophonium reversal of vecuronium block to a similar degree.     

Acceleromyography improves detection of residual neuromuscular blockade in children

Purpose

To determine whether detection of residual blockade is improved by using the accelerograph. A secondary objective was to compare acceleromyographic measurements with those obtained by electromyography.

Methods

In a prospective, randomized, double-blind investigation, 22 anaesthetized children were studied during recovery from neuromuscular blockade following 0.1 mg· kg^?1 vecuronium iv. Assessments of depth of block began 10 min after injection and were repeated at one minute intervals using electromyography (Datex, Relaxograph) in one hand, and acceleromyography (Biometer, Tofguard) in the other, to measure responses of the adductor pollicis to train-of-four (TOF) stimulation of the ulnar nerve. Monitoring was stopped when no fade was visible and TOF ratio ≥0.7. The electromyographic (EMG) and acceleromyographic (AMG) data were compared with corresponding observations of the number of twitches and TOF fade in the visible responses of the thumb, made by the attending anaesthetist. The method of Bland and Altman was used to compare differences between AMG and EMG data.

Results

During recovery from neuromuscular blockade, fade was no longer visible clinically 38.6 ± 10.4 min (mean ± SD) after the administration of vecuronium. This corresponded to TOF ratios of 0.40 ± 0.23 by AMG and 0.34 ± 0.21 by EMG. Usually, two twitches were visible before AMG detected the first twitch. The time to TOF ratio ≥0.7 by AMG and EMG was similar at 49.1 ± 10.5 and 50.9 ± 9.0 min, respectively. The bias between AMG and EMG was one minute, with limits of agreement from ?10 to nine min.

Conclusion

AMG is superior to visual assessment in detecting residual neuromuscular block and provides similar estimates of recovering block as the more cumbersome EMG.     

Determination of endtidal sevoflurane concentration for tracheal intubation in children with the rapid method

Purpose

Using the conventional method of determining the end-tidal concentration of inhalational anaesthetics for tracheal intubation, a constant end-tidal anaesthetic concentration is maintained for at least 15 min. As sevoflurane has a low tissue/gas partition coefficient, it seems possible in paediatric patients to determine end-tidal concentrations for tracheal intubation more rapidly by using a high inspired concentration. We determined ED₅₀ and ED₉₅ of sevoflurane for tracheal intubation, the end-tidal concentrations that prevented 50% and 95% of patients from coughing and gross purposeful muscular movements after intubation.

Methods

Twenty-nine, ASA I, unpremedicated patients, aged two to eight years, were enrolled. Anaesthesia was induced using a mask and 5% sevoflurane, inspired, in oxygen. When end-tidal sevoflurane concentration attained a predetermined value, laryngoscopy and tracheal intubation were performed using an uncuffed tracheal tube without neuromuscular relaxants or adjuvants. Each concentration at which laryngoscopy and tracheal intubation were attempted was randomly predetermined (with 0.5% as a step size). When tracheal intubation was accomplished without gross purposeful muscular movements, it was considered a smooth tracheal intubation.

Results

The ED₅₀ end-tidal sevoflurane concentration for tracheal intubation was 3.10% (95% confidence limits: 2.43% and 3.78% ), and the ED₉₅ was 4.68% (95% confidence limits: 3.91% and 12.74% ). The times to end-tidal sevoflurane concentrations of 3.0% and 4.5% were 149 ± 15 sec (mean ± SD) and 213 ± 23 sec.

Conclusion

In paediatric patients, this method enabled determination of ED₅₀ and ED₉₅ end-tidal sevoflurane concentrations for tracheal intubation without obtaining a long stabilization period.     

Synergistic effect of sevoflurane and isoflurane on inhibition of the adult-type muscle nicotinic acetylcholine receptor by rocuronium

Purpose

Inhaled anesthetics increase the incidence of postoperative residual neuromuscular blockade, and the mechanism is still unclear. We have investigated the synergistic effect of low-concentration inhaled anesthetics and rocuronium on inhibition of the inward current of the adult-type muscle nicotinic acetylcholine receptor (ε-nAChR).

Methods

Adult-type mouse muscle ε-nAChR was expressed in HEK293 cells by liposome transfection. The inward current of the ε-nAChR was activated by use of 10 μmol/L acetylcholine alone or in combination with different concentrations of sevoflurane, isoflurane, or rocuronium. The concentration–response curves of five cells were constructed, and the data yielded the 5, 25, and 50 % inhibitory concentrations (IC₅, IC₂₅, and IC₅₀, respectively) for single-drug application. Subsequently, the functional channels were perfused by adding 0.5 IC₅ of either sevoflurane or isoflurane (aqueous concentrations 140 and 100 μmol/L, respectively) to the solution, followed by addition of IC₅, IC₂₅, or IC₅₀ rocuronium. The amount of inhibition was calculated to quantify their synergistic effect.

Results

The inhibitory effect of rocuronium was enhanced by sevoflurane or isoflurane in a concentration-dependent manner. Sevoflurane or isoflurane (0.5 IC₅) with rocuronium at IC₅, IC₂₅, and IC₅₀ synergistically inhibited the current amplitude of adult-type muscle ε-nAChR. When the IC₅ of rocuronium was used, isoflurane had a stronger synergistic effect than sevoflurane (p < 0.05). When rocuronium was applied at higher concentrations (IC₂₅ and IC₅₀), sevoflurane had an effect similar to that of isoflurane. For both inhaled anesthetics, the synergistic effect was more intense for rocuronium at IC₅ than for rocuronium at IC₂₅ or IC₅₀.

Conclusion

Residual-concentration sevoflurane or isoflurane has a strong synergistic effect with rocuronium at clinically relevant residual concentrations. A lower rocuronium concentration resulted in a stronger synergistic effect.     

Recurrent Laryngeal Nerve Monitoring and Rocuronium: A Selective Sugammadex Reversal Protocol

Background

The use of neuromuscular blocking agents may affect intraoperative neuromonitoring during thyroid surgery. A selective neuromuscular recovery protocol was evaluated in a retrospective cohort study during human thyroid neural monitoring surgery.

Methods

One hundred and twenty-five consecutive patients undergoing thyroidectomy with intraoperative neuromonitoring followed a selective neuromuscular block recovery protocol—single intubating dose of rocuronium followed by sugammadex if needed at the first vagal stimulation (V1).

Results

Data from 120 of 125 patients could be analysed. Fifteen (12.5%) patients needed sugammadex reversal to obtain an EMG response at the first vagal stimulation (V1). In the remaining 105 patients, spontaneous recovery of rocuronium-induced neuromuscular block was sufficient for a successful first vagal stimulation (V1).

Conclusions

In patients undergoing thyroid surgery, routine reversal of rocuronium block with sugammadex is not mandatory for reliable intraoperative neuromonitoring. A selective neuromuscular block recovery approach may be a valuable and more cost-efficient alternative to routine reversal.

     

Monitoring of vecuronium-induced neuromuscular block at the sternocleidomastoid muscle in anesthetized patients

Purpose

To assess the degree of neuromuscular block acceleromyographically at the sternocleidomastoid muscle.

Methods

Eighteen adult patients scheduled for air–oxygen–sevoflurane–fentanyl and epidural anesthesia were studied. In the patients, the right accessory nerve and the sternocleidomastoid muscle were stimulated and the contraction of the sternocleidomastoid muscle was evaluated acceleromyographically. Simultaneously, the response of the adductor pollicis muscle was measured electromyographically. Supramaximal stimulating current, degree of maximum neuromuscular block after vecuronium 0.1 mg/kg, and onset of or recovery from vecuronium-induced neuromuscular block were compared between the two muscles.

Results

The supramaximal stimulating current at the sternocleidomastoid muscle was significantly higher than that at the adductor pollicis muscle (54.8 ± 7.1 vs. 33.7 ± 10.3 mA, mean ± SD, P < 0.001). The onset of neuromuscular block at the sternocleidomastoid muscle did not significantly differ from that at the adductor pollicis muscle (214 ± 117 vs. 161 ± 87 s, P = 0.131). The degree of maximum neuromuscular block at the sternocleidomastoid muscle was significantly less than that at the adductor pollicis muscle (93.6 ± 3.1 vs. 99.2 ± 2.5%, P < 0.001). During recovery from neuromuscular block, T1/control and train-of-four ratio measured at the sternocleidomastoid muscle were significantly higher than those at the adductor pollicis muscle 10–30 and 40–120 min after vecuronium, respectively (P < 0.05).

Conclusion

The sternocleidomastoid muscle is more resistant to vecuronium than the adductor pollicis muscle. Recovery from neuromuscular block is faster at the sternocleidomastoid muscle than at the adductor pollicis muscle.     

Double burst stimulation2,3: a new stimulating pattern for residual neuromuscular block

Purpose

We present a new stimulating pattern: double burst stimulation_2,3 (DBS_2,3) for evaluating residual neuromuscular block.

Methods

Forty adult patients were studied. For DBS_2,3, two burst stimuli were applied every 750 msec. The first consisted of two tetanic stimuli of 0.2 msec duration and the second of three tetanic stimuli of 0.2 msec duration. At varying degrees of neuromuscular block induced by vecuronium, the presence or absence of fade, or the presence or absence of waxing (i.e., the feeling that the muscular contraction in response to the second burst was stronger than that to the first) was determined by an observer blinded to the depth of neuromuscular block. In addition, the relationship between the train-of-four (TOF) ratio and DBS_2,3 ratio was established at varying depths of neuromuscular block (TOF ratio 0.04–1.00).

Results

The probabilities of tactile detection of fade in response to DBS_2,3 were 100, 76, 15, 9, 3, 0, and 0% at a TOF ratio of 0–0.40, 0.41–0.50, 0.51–0.60, 0.61–0.70, 0.71–0.80, 0.81–0.90, and 0.91–1.00, respectively. Waxing in response to the DBS_2,3 was identified in 0, 6, 32, 84, and 98% of cases when the TOF ratios were 0.00–0.60, 0.61–0.70, 0.71–0.80, 0.81–0.90, and 0.91–1.00, respectively. A close linear relationship existed between the TOF ratio and DBS_2,3 ratio (r = 0.96, P < 0.000001).

Conclusion

DBS_2,3 is of clinical use because when residual neuromuscular block is clinically important, fade can be identified, but once neuromuscular function returns to a sufficient level, waxing can be detected.     

The effect of alfentanil versus ketamine on the intubation condition and hemodynamics with low-dose rocuronium in children

Purpose

We investigated the effect of alfentanil and ketamine on the intubation condition and hemodynamic parameters during propofol anesthesia with low-dose rocuronium in children.

Methods

Fifty-four children, aged 3–9 years undergoing tonsillectomy, were randomly allocated to receive either alfentanil 20 μg/kg (alfentanil group, n = 27) or ketamine 0.5 mg/kg (ketamine group, n = 27) 1 min before anesthesia induction. Anesthesia was induced with propofol 2.5 mg/kg and rocuronium 0.3 mg/kg and maintained with propofol infusion (6 mg/kg/h). The neuromuscular relaxation was monitored, and intubation conditions, hemodynamic changes, and recovery time were assessed.

Results

All patients were successfully intubated and there were no significant differences in the intubation conditions between alfentanil and ketamine groups. At the time of tracheal intubation, the median [inter-quartile range] twitch height was similar between two groups (37 [4–48] % in the alfentanil group vs. 29 [4–43.5] % in the ketamine group, p = 0.326).

Conclusions

This study showed that both ketamine 0.5 mg/kg and alfentanil 20 μg/kg provided adequate intubation condition during propofol induction with low-dose rocuronium in children. The mean arterial pressure and heart rate were higher in the ketamine group after propofol injection but they remained within the normal limit in both groups throughout the study period.