Halogenated vapor anesthetics adversely influence edrophonium reversal.

Reversal of the pancuronium induced neuromuscular block by edrophonium was studied in different groups of male surgical patients. All groups received similar premedication and identical induction of anesthesia. Neuromuscular function was monitored by the transduced response of the thumb adductor muscle to different [e.g. 0.2, 2 and 50 counts per second (cps)] supramaximal electrical stimuli applied to the ulnar nerve. When the regimen of anesthesia maintenance included halogenated vapor anesthetics the reversal of neuromuscular block was of lesser degree than in the case of N2O/O2 + fentanyl anesthesia. The reversal of the "fade-type" (e.g. tetanic and "train of four") responses was particularly incomplete with halothane and isoflurane. Compared with edrophonium, pyridostigmine was found to be more effective under halothane anesthesia. Based on these results, edrophonium may not be the first choice in the clinical reversal of deep levels of nondepolarizing neuromuscular block in the presence of vapor anesthetics.

Reversal of pipecuronium bromide with pyridostigmine.

Pipecuronium Bromide (Arduan, Organon, Inc, West Orange) is a long-acting, nondepolarizing neuromuscular blocking agent. The efficacy of pyridostigmine 170 micrograms/kg intravenously (approximately 10 mg/70 kg) for reversing pipecuronium has not been reported. This study was performed to determine the time required to obtain a train-of-four (TOF) ratio of 0.7 after administration of pyridostigmine 140 micrograms/kg at 25% recovery of T1 after pipecuronium-induced neuromuscular blockade. Sixteen, American Society of Anesthesiology (ASA) I or II patients undergoing surgical procedures of at least 90 minutes, requiring intubation and muscle relaxation were included. Neuromuscular blockade was assessed using the Puritan-Bennett/Datex NMT 221 placed for ulnar nerve stimulation. Anesthesia was maintained with a nitrous oxide/narcotic technique and the use of potent inhalational anesthetics was avoided. The mean reversal time was found to be 16.14 minutes, with a minimum of 10.3 minutes and a maximum of 24.3 minutes. The standard error was +/- 1.05 minutes with a variance of 17.68 minutes.

Comparison of atropine and glycopyrrolate in a mixture with pyridostigmine for the antagonism of neuromuscular block.

Neuromuscular block was antagonized using pyridostigmine 250 micrograms kg-1 in two groups of 50 patients; one group received atropine 20 micrograms kg-1 and the other glycopyrrolate 10 micrograms kg-1 with the anticholinesterase drug. Atropine was associated with a greater initial tachycardia than was glycopyrrolate. The subsequent bradycardia was also greater in this group, although the decreases in heart rate were smaller than those generally observed following mixtures of atropine and neostigmine. Arrhythmias were transient and required no treatment in either group. Better control of secretions was achieved with glycopyrrolate.

Dose-response curves for edrophonium, neostigmine, and pyridostigmine after pancuronium and d-tubocurarine.

To determine the potencies of neostigmine, pyridostigmine, and edrophonium in reversing pancuronium and d-tubocurarine blockade, dose-response curves were established for first twitch height recovery and train-of-four ratio. One hundred and twenty ASA physical status I or II patients scheduled for elective surgery received either 0.06 mg/kg pancuronium or 0.36 mg/kg d-tubocurarine during a thiopental-nitrous oxide-enflurane anesthetic. Train-of-four stimulation was applied every 12 s, and the force of contraction of the adductor pollicis muscle was recorded. When first twitch height had recovered spontaneously to 10% of its initial value, neostigmine (0.005, 0.01, 0.02 or 0.05 mg/kg), pyridostigmine (0.02, 0.04, 0.1, or 0.2 mg/kg), or edrophonium (0.1, 0.2, 0.4 or 1 mg/kg) was injected by random allocation. Recovery was measured 10 min after the injection of the antagonist. First twitch ED50's were 0.013, 0.085, and 0.17 mg/kg after pancuronium, and 0.017, 0.11, and 0.27 mg/kg after d-tubocurarine, for neostigmine, pyridostigmine, and edrophonium, respectively. The ED50 for pyridostigmine and edrophonium obtained after d-tubocurarine was significantly larger (P less than 0.05) than that after pancuronium. The train-of-four dose-response curves were significantly flatter for edrophonium than for the other two agents, indicating a greater ability of edrophonium to antagonize fade at low doses. It is concluded that the potency of reversal agents may be different for different relaxants, and that potency ratios might depend upon the end-point chosen as full neuromuscular recovery.