Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: Low-dose droperidol has been reported to suppress the amplitude of transcranial electrical motor-evoked potentials (TCE-MEPs), but no randomized controlled trials have been conducted to assess this. This randomized, double-blinded, placebo-controlled trial aimed to test the hypothesis that low-dose droperidol reduced TCE-MEP amplitudes. METHODS: Twenty female patients with adolescent idiopathic scoliosis, aged between 12 and 20 years, and scheduled to undergo corrective surgery were randomly allocated to receive droperidol (20 µg/kg) or 0.9% saline. After recording baseline TCE-MEPs, the test drug was administered, following which TCE-MEP recordings were carried out every 2 minutes for up to 10 minutes. The primary outcome was the minimum relative TCE-MEP amplitude (peak-to-peak amplitude, percentage of baseline value) recorded in the left tibialis anterior muscle. Secondary outcomes included minimum relative MEP amplitudes recorded from all other muscle groups monitored in the study. Data are expressed as medians (interquartile range). RESULTS: The TCE-MEP amplitude of the left tibialis anterior muscle was significantly reduced following droperidol administration compared with saline (37% [30% to 55%] vs. 76% [58% to 93%], respectively, P<0.01). In the other muscles, the amplitudes were reduced in the droperidol group, except for the bilateral abductor pollicis brevis and the left quadriceps femoris muscles. The relative amplitude of the bilateral F waves recorded from the gastrocnemius was decreased in the droperidol group. CONCLUSIONS: Low-dose droperidol (20 µg/kg) reduced TCE-MEP amplitudes. Anesthesiologists should pay attention to the timing of droperidol administration during intraoperative TCE-MEP recordings, even if used in a low dose.

DOI： 10.1097/ANA.0000000000000784

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Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: A low-dose bolus or infusion of ketamine does not affect transcranial electrical motor-evoked potential (MEP) amplitude, but a dose ≥1 mg/kg may reduce MEP amplitude. We conducted a randomized, double-blinded, placebo-controlled study to evaluate the effect of ketamine (1 mg/kg) on transcranial electrical MEP. METHODS: Twenty female patients (aged 12 to 18 y) with adolescent idiopathic scoliosis scheduled to undergo posterior spinal fusion were randomly allocated to receive ketamine or saline. General anesthesia was induced and maintained with continuous infusions of propofol and remifentanil. MEP was elicited by supramaximal transcranial electrical stimulation. MEP recordings were obtained at baseline and then at 2, 4, 6, 8, and 10 minutes after administration of ketamine (1 mg/kg) or saline (0.1 ml/kg). The primary endpoint was the minimum relative MEP amplitude (peak-to-peak amplitude, % of baseline value) recorded from the left tibialis anterior muscle. The baseline amplitude recorded before test drug administration was defined as 100%. RESULTS: Medians (interquartile range) minimum MEP amplitudes in the left tibialis anterior muscle in the ketamine and saline groups were 26% (9% to 34%) and 87% (55% to 103%) of the baseline value, respectively (P<0.001). MEP amplitudes in other muscles were significantly reduced by ketamine. The suppressive effect of ketamine lasted for at least 10 minutes in each muscle. CONCLUSION: A 1-mg/kg bolus dose of ketamine can reduce MEP amplitude. Anesthesiologists should consider the dosage and timing of intravenous ketamine administration during MEP monitoring.

DOI： 10.1097/ANA.0000000000000653

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Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: Propofol inhibits the amplitudes of transcranial electrical motor-evoked potentials (TCE-MEP) in a dose-dependent manner. However, the mechanisms of this effect remain unknown. Hence, we investigated the spinal mechanisms of the inhibitory effect of propofol on TCE-MEP amplitudes by evaluating evoked electromyograms (H-reflex and F-wave) under general anesthesia. METHODS: We conducted a prospective, single-arm, interventional study including 15 patients scheduled for spine surgery under general anesthesia. Evoked electromyograms of the soleus muscle and TCE-MEPs were measured at three propofol concentrations using target-controlled infusion (TCI: 2.0, 3.0, and 4.0 µg/mL). The primary outcome measure was the left H-reflex amplitude during TCI of 4.0- compared to 2.0-µg/mL propofol administration. RESULTS: The median [interquartile range] amplitudes of the left H-reflex were 4.71 [3.42-6.60] and 5.6 [4.17-7.46] in the 4.0- and 2.0-μg/mL TCI groups (p = 0.4, Friedman test), respectively. There were no significant differences in the amplitudes of the right H-reflex and the bilateral F-wave among these groups. However, the TCE-MEP amplitudes significantly decreased with increased propofol concentrations (p < 0.001, Friedman test). CONCLUSION: Propofol did not affect the amplitudes of the H-reflex and the F-wave, whereas TCE-MEP amplitudes were reduced at higher propofol concentrations. These results suggested that propofol can suppress the TCE-MEP amplitude by inhibiting the supraspinal motor pathways more strongly than the excitability of the motor neurons in the spinal cord.

DOI： 10.1007/s00540-021-02927-7

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Publishing type：Research paper (scientific journal)   Publisher：Ovid Technologies (Wolters Kluwer Health)  

DOI： 10.1213/ane.0000000000005236

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Low-dose droperidol has been widely used as an antiemetic during and after surgery. Although high-dose droperidol affects motor-evoked potential, the effects of low-dose droperidol on motor-evoked potential amplitude are unclear. The aim of this study was to investigate whether low-dose droperidol affects motor-evoked potential amplitude. We retrospectively reviewed the data of patients who underwent spine surgery under general anesthesia with motor-evoked potential monitoring from February 2016 to 2017. The outcome was the motor-evoked potential amplitude of the bilateral abductor pollicis brevis muscle, tibialis anterior muscle, and abductor hallucis muscle within 1 and 1-2 h after droperidol administration, compared with the baseline motor-evoked potential value. Thirty-four patients were analyzed. The median dose of droperidol was 21 µg/kg. The motor-evoked potential amplitudes of all muscles were significantly reduced after droperidol administration and recovered to baseline values within 2 h. The reduction of all motor-evoked potential amplitudes after droperidol administration was 37-45% of baseline values. There were no significant differences in other drugs administered. There were no serious adverse effects of droperidol administration. Motor-evoked potential amplitude was suppressed by low-dose droperidol. During intraoperative motor-evoked potential monitoring in spine surgery, anesthesiologists should pay careful attention to the timing of administration of droperidol, even at low doses. Based on the results of this study, we are conducting a randomized controlled trial.

DOI： 10.1007/s10877-020-00464-4

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Other Link： http://link.springer.com/article/10.1007/s10877-020-00464-4/fulltext.html