Increased potency of nondepolarizing relaxants after poliomyelitis.

The pathophysiology of poliomyelitis and the recognition of the "post-polio syndrome" suggest that susceptibility to muscle relaxants of patients previously affected by this disease, may be altered. We compared the effects of d-tubocurarine (dTc), pancuronium (P), and gallamine (G) on two pediatric surgical patient groups: one with a previous history of polio disease, occurring 6 to 12 years prior admission (N = 30, average age: 13 yrs, weight: 43 kg) and another without history of this disease (N = 51, average age: 11 yrs, weight: 39 kg). Following uniform premedication, thiopental, N2O/O2 + narcotic (fentanyl) anesthesia was given for reconstructive surgeries. For orotracheal intubation the patients were briefly paralyzed with 0.7 mg/kg suxamethonium. The thumb adductor responses to supramaximal 1/5 Hz impulses (continuous mode) and to 50 Hz tetanic stimuli (periodically) were recorded. After full recovery from the effect of suxamethonium (100% return of the neurally evoked muscle response) cumulative ED50 values and the recovery index (minutes elapsed from 90% to 50% block of the twitch response) of the three nondepolarizing muscle relaxants were determined. The ED50 of dTc and P were significantly lower with both neuromuscular responses in the post-polio groups (dTc, N = 12 and P, N = 10) as compared to the controls (N = 24 and 18). A tendency toward lower ED50 values in the polio group was also observed with G (N = 6). The differences, however, as compared to the control group (N = 9) were not significant (P less than .2). Recovery times were identical in the polio versus non-polio groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the onset, spontaneous recovery and train of four fade of the clinical neuromuscular block produced by pancuronium and pipecuronium.

The following study was performed to delineate the possible differences in the onset, recovery and "train of four" (TOF) fade characteristics of pancuronium (Pan) and pipecuronium (Pip). Eighty adult American Society of Anesthesiologists (ASA) class I and II surgical patients were studied with institutional approval. After premedication, general anesthesia was induced with thiopental sodium i.v. followed by N2/O2 halothane and fentanyl. The lungs were ventilated. Normocarbia and normothermia were maintained. Two groups of 40 patients received pancuronium (0.1 mg/kg i.v.) or pipecuronium (0.07 mg/kg i.v.). Neuromuscular block (NMB) was measured simultaneously by mechanomyography (MMG) and electromyographically (EMG) on the thumb adductor muscle. Supramaximal (TOF) stimuli were applied to the ulnar nerve every 20 seconds. The onset of neuromuscular blocking action, duration of action (to 25% recovery of twitch response). TOF fade during onset and up to 25% T1 response recovery, hemodynamic changes following induction of anesthesia and after the muscle relaxant and subsequent oral intubation were determined. Mean values and the differences in the two treatments groups were statistically analyzed. The onset of action of the two agents were similar: 3.62 +/- 0.02 minutes (MMG) and 4.94 +/- 0.05 minutes (EMG, Pan) and 3.74 +/- 0.02 minutes (MMG) and 4.36 +/- 0.012 minutes (EMG, Pip). TOF fade ratios during the onset phase were similar. TOF fade at the 25% twitch responses recovery level was 100% with the MMG responses and (96% (Pan) and 94.8% (Pip) with the EMG responses at the 25% twitch response recovery level. Hemodynamic changes were similar after the single dose administration of the bolus administration of the two NMB agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of the Datex 221 neuromuscular transmission monitor for recording posttetanic electromyographic responses.

The assessment of deep neuromuscular blockade produced by nondepolarizing neuromuscular blocking agents is not possible with the conventional use of the Datex NMT-221 "relaxograph" (Datex NMT-221 monitor, Datex Instrumentarium, Helsinki, Finland), an otherwise useful electromyographic (EMG) monitoring device. A method whereby the relaxograph can be adapted to quantitatively measure posttetanic responses is described here. In anesthetized adult patients, neuromuscular blockade was monitored simultaneously on both hands with two relaxographs. On one hand, EMG responses of hypothenar muscles to the built-in 1/20-second sequence of train-of-four stimuli of the monitor were used. On the other hand, similar recordings were made with the addition of periodically superimposed supramaximal tetanic stimuli of 100 Hz to the ulnar nerve. Neuromuscular block was provided with pancuronium. The time courses of the spontaneous recovery of the first of the train-of-four EMG responses were compared in the stimulated and control arms. At the end of the surgery, the neuromuscular block was pharmacologically reversed with atropine and neostigmine. If no tetanic stimuli were applied, the EMG responses were identical in both arms during the spontaneous recovery from the neuromuscular blockade. If tetanic stimuli were applied every 4 or 7 minutes, the rate of recovery in the stimulated hand usually exceeded that of the control hand. However, no significant difference was observed in the recovery rate when the tetanic stimuli were spaced at 15-minute intervals. Pharmacologic reversal by atropine and neostigmine was found to be identical in all patient groups. The author concludes that the Datex relaxograph is suitable for the quantitative assessment of profound surgical neuromuscular blockade with the described modification.

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.

Antagonism of pancuronium- and pipecuronium-induced neuromuscular block.

We have compared the antagonism of neuromuscular block produced by pipecuronium with pancuronium in 80 anaesthetized surgical patients using mechanomyography and electromyography. Pancuronium 0.1 mg kg-1 or pipecuronium 0.07 mg kg-1 was given after induction of anaesthesia and neuromuscular block was adjusted to 75% twitch depression at the time of antagonism. The following regimens were used: edrophonium 0.5 and 1.0 mg kg-1, neostigmine 0.04 mg kg-1, pyridostigmine 0.3 mg kg-1 and edrophonium 0.25 mg kg-1 with pyridostigmine 0.15 mg kg-1. Antagonism was evaluated also by the head lift test. There was no difference between the reversibility of neuromuscular block produced by pancuronium or pipecuronium. Edrophonium produced a significantly faster antagonism than neostigmine or pyridostigmine but onset of action was not significantly faster than that of edrophonium with pyridostigmine. All regimens produced 100% (or near 100%) antagonism of twitch response within 15 min. However, TOF fade antagonism was more complete with pyridostigmine, neostigmine and edrophonium 1.0 mg kg-1 than with edrophonium 0.5 mg kg-1. The head lift test indicated somewhat less antagonism with edrophonium 0.5 and 1.0 mg kg-1. Using five monitoring methods, the rank order of reversal potency was: pyridostigmine approximately neostigmine > edrophonium 1.0 mg kg-1 > edrophonium+pyridostigmine > edrophonium 0.5 mg kg-1.