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The aim of this study was to investigate whether monitoring neuromuscular block at the masseter muscle (MM) would allow faster tracheal intubation when compared with that at the adductor pollicis muscle (APM).Twenty female patients undergoing gynecological surgery were enrolled into this study. Immediately after inducing anesthesia with fentanyl and propofol, both the left masseter and ulnar nerves were stimulated in a 2 Hz train-of-four (TOF) mode using peripheral nerve stimulators. Contractions of the MM were felt with the anesthesiologist's left hand lifting the patient's jaw and holding an anesthesia facemask, while those of the APM were visually observed. Immediately after the contracting responses of the muscles were confirmed, all of the patients received an iv bolus of vecuronium 0.1 mg kg(-1). Onset times after vecuronium were defined as the duration until the contractions became impalpable at the MM or invisible at the APM. When the contraction of the MM could no longer be felt, the conditions for laryngoscopy and tracheal intubation were assessed.Onset time evaluated tactually at the MM (mean +/- SD, 108.4 +/- 27.7 s) was significantly shorter than that evaluated visually at the APM (181.2 +/- 32.1 s, P0.0001). The intubating conditions for all patients were graded as either excellent or good.Tactual evaluation of muscle paralysis of the MM during induction of anesthesia is clinically useful since it leads to faster tracheal intubation.

The main aim of this study was to compare the onset times of rocuronium evaluated subjectively and by acceleromyography at the masseter muscle (MM). Forty female patients were sequentially enrolled in this study. In the first 20 patients, neuromuscular block was evaluated subjectively. After induction of anesthesia with fentanyl and propofol, both the left masseter and ulnar nerves were stimulated in 2-Hz train-of-four (TOF) mode using peripheral nerve stimulators. Contractions of the MM were felt with an anesthesiologist’s left hand holding an anesthesia facemask; those of the adductor pollicis (APM) were visually observed. All the patients received a bolus of rocuronium, 0.6 mg/kg. Onset times after rocuronium were defined as the duration until the contractions became impalpable at the MM or invisible at the APM. At the time contraction of the MM had not been felt, intubating conditions were assessed. In the next 20 patients, contractions of the MM and the APM were concurrently quantified using acceleromyography after induction of anesthesia and laryngeal mask insertion. Following 0.6 mg/kg rocuronium, onset of the action was recorded. Onset of the action of rocuronium at the MM evaluated subjectively [mean (SD), 70.3 (17.7) s] was similar to that monitored acceleromyographically [73.3 (27.6) s, P > 0.05], and significantly shorter than that at the APM acceleromyographically [111.0 (34.8) s, P = 0.016]. Intubating conditions of 20 patients were graded either excellent or good. Subjective evaluation of contractions of the MM by an anesthesiologist’s hand may be reliable to determine faster timing for safe tracheal intubation.

The main purpose of this study was to examine the effectiveness of the timing principle with 1 mg kg(-1) rocuronium for rapid sequence intubation. As secondary outcomes, propofol and lidocaine with or without remifentanil were examined to note their effects on the cardiovascular responses to laryngoscopy and intubation.Thirty patients were randomly allocated to one of two groups of 15 patients each: a lidocaine-treated group (L) and a lidocaine/remifentanil-treated group (LR). Thirty seconds after lidocaine 1 mg kg(-1) with or without infusion of remifentanil 1 microg kg(-1) min(-1), all patients received a bolus of rocuronium 1 mg kg(-1). Shortly afterwards, patients were given propofol 2-2.5 mg kg(-1). Intubating conditions and cardiovascular responses were observed 60 s after rocuronium. The time to spontaneous recovery of visible train-of-four (TOF) counts of 4 was observed at the thumb during 1.0-1.5% end-tidal sevoflurane and remifentanil anesthesia.All patients had excellent or good intubating conditions. Hypertension and tachycardia during laryngoscopy were well prevented in group LR, whereas they were significantly observed in group L. The times to reappearance of TOF counts of 4 were comparable in all groups [mean (SD); 63.6 (8.6) min in group L and 63.5 (11.6) min in group LR].Application of the timing principle with 1 mg kg(-1) rocuronium is beneficial for rapid tracheal intubation. Co-administered lidocaine, remifentanil and propofol can definitely suppress cardiovascular responses during laryngoscopy and intubation.

The aim of this study was to examine the effect of landiolol hydrochloride, an ultrashort-acting beta(1)-blocker, on suxamethonium-induced neuromuscular block.Thirty patients were randomly allocated to receive a loading dose of landiolol, 0.125 mg x kg(-1) x min(-1) for 1 min, followed by an infusion at 0.04 mg x kg(-1) x min(-1), or placebo. Twenty minutes after the infusion of landiolol or placebo, suxamethonium 1 mg x kg(-1) was administered during propofolfentanyl-nitrous oxide anesthesia. Neuromuscular block was monitored by train-of-four (TOF) responses of the adductor pollicis muscle, applying acceleromyographic stimuli to the ulnar nerve.The onset of neuromuscular block did not differ between the groups. The time from administration of suxamethonium to spontaneous recovery to the first twitch of TOF (T1) of control was significantly longer in the landiolol group (mean [SD]; 12.2 [2.5] min), when compared with the control group (9.8 [2.6] min). However, the TOF ratios measured when the T1 had spontaneously recovered to 10%, 25%, 50%, 75%, 90%, and 100% of control was comparable between the groups.Landiolol delayed recovery from suxamethonium-induced paralysis. However, the interaction between the drugs seemed to be small in the clinical setting.

The purpose of this study was to clarify the relationship between skin temperature over the thenar muscles and the duration of action of vecuronium measured acceleromyographically at the thumb in anesthetized patients.In 15 patients undergoing elective open abdominal surgery under propofol, fentanyl, and nitrous oxide anesthesia, train-of-four (TOF) stimuli were delivered over the ulnar nerve at 2 Hz every 15 s, and the degree of neuromuscular block was measured acceleromyographically at the thumb. Each patient received an intubating dose of vecuronium 0.1 mg x kg(-1), followed by maintenance doses of 0.02 mg x kg(-1) administered repeatedly whenever the first twitch of TOF responses had recovered to 25% of control. The interval between maintenance doses was defined as the clinical duration (DUR25). The median values of skin temperature (ST) over the ipsilateral thenar muscles and esophageal temperature (ET) were recorded during the action of the first and all subsequent maintenance doses. The relationships between change in temperature and change in DUR25 were analyzed.Whereas ET showed only minor changes (median, -0.3 degrees C), ST fluctuated markedly between +0.9 degrees and -6.3 degrees C (median, -1.4 degrees C). Increase and decrease were also seen in a series of DUR25s, as expected from the changes in ST. The median values of DUR25 produced by the first and last maintenance vecuronium doses were 21.5 and 32.3 min, respectively. A negative linear correlation was found between the change in DUR25 and that in ST, demonstrating that DUR25 increased by 20% of baseline with each 1 degrees C decrease in ST.Our results show that peripheral ST decreases considerably during open abdominal surgery without reduction in core temperature, and the decrease contributes to the potentiation of neuromuscular block in the periphery during propofol, fentanyl, and nitrous oxide anesthesia.

Recently, heart rate spectral analysis has become recognized as a powerful tool for quantitatively evaluating autonomic nervous system activity. The purpose of this study was to analyze parasympathetic nervous activity by heart rate spectral analysis after administration of atropine and neostigmine for reversal of residual neuromuscular blockade. For our study, 36 female patients (26–37 years of age), ASA physical status (PS) I, who were scheduled for laparoscopic examination, were randomly allocated to one of the following four groups: In group A (1∶1), 9 patients received 1.0mg atropine followed 4 min later by 1.0 mg neostigmine. In group B (1∶2), 9 patients received 0.5 mg atropine followed 4 min later by 1.0 mg neostigmine. In group C (1∶2.5), 9 patients received 1.0 mg atropine followed 4 min later by 2.5 mg neostigmine. In group D (1∶2 mix), 9 patients received a mixed solution of atropine 0.5 mg and neostigmine 1.0mg. After finishing the laparoscopic examination, additional anesthesia was maintained with 70% nitrous oxide, 30% oxygen, and 0.5% isoflurane. The control data were obtained 10 min after finishing the laparoscopic examination. After that, the data on atropine were obtained between 2 and 4min after administration of atropine, and the data on neostigmine were obtained between 5 and 7 min after administration of neostigmine. We selected power spectral density of the high-frequency component (HF-p) in heart rate spectral analysis as an index to assess parasympathetic activity. In groups A, B, and C, the HF-p decreased after administration of atropine. In groups B and C, the HF-p increased after administration of neostigmine as compared to the control. In group A, the HF-p increased after neostigmine but did not differ from the control. The difference between groups D and B was not statistically significant. From the results of this study, we concluded that the muscarinic effect of neostigmine could not be sufficiently blocked by atropine at 1/2 dosages of neostigmine, but could be sufficiently blocked by atropine at equivalent dosages of neostigmine, under light isoflurane anesthesia.