Neuromuscular effects of sevoflurane in patients with myasthenia gravis

The current study evaluated the neuromuscular responses following administration of sevoflurane in 14 patients with myasthenia gravis (MG) (I-IIb in Osserman's classification) scheduled for thymectomy and in 11 control patients (ASA I-II) who underwent elective surgery. The electromyographic (EMG) response of the abductor digiti minimi was measured following train-of-four (TOF) stimulation of the ulnar nerve every 20 s. After induction of anesthesia with a combination of 3-4 mg·kg(-1) thiopental and 1-2 μg·kg(-1) fentanyl with 66% N2O and oxygen, an inspired concentration of 4% sevoflurane was administered via a face mask for 7 min. Anesthesia was maintained during surgery with 66% N2O in oxygen and with 1 minimum alveolar concentration (MAC) of end-tidal concentration of sevoflurane. The T1 (the amplitude of the first response) values decreased more profoundly in the MG patients than in the control patients at the end of surgery (P<0.05). Following administration of 4% sevoflurane for 7 min, the TOFR (the ratio of the fourth TOF to the first response) values revealed depressions greater than 10% of preinhalation values in 11 of 14 MG patients with a marked individual variation. This attenuated response was followed by a further depression of the TOFR values with increasing time of 1 MAC sevoflurane anesthesia. On the other hand, no notable changes were observed in patients with normal neuromuscular functions. The most significant factor that correlated with the depression of the TOFR values induced by 1 MAC sevoflurane was the anti-AchR antibody titers (P=0.029). Our results indicate that MG patients have an increased neuromuscular sensitivity to sevoflurane.

Immunostimulatory oligodeoxynucleotide containing TTTCGTTT motif from Lactobacillus rhamnosus GG DNA potentially suppresses OVA-specific IgE production in mice

In a previous study of the immunoregulatory properties of commensal bacterial DNA, we identified the strong immunostimulatory oligodeoxynucleotide (ISS-ODN) ID35 in the genomic DNA of Lactobacillus rhamnosus GG (LGG). The observed effects of ID35 are because of the unique TTTCGTTT motif located at the 5' end of the ODN, which is different from the previously identified ISS motifs in humans and mice. In the present study, we used an ovalbumin (OVA)-sensitized mouse model to show that ID35 is a potent suppressor of antigen-specific immunoglobulin E (IgE) production in vivo. This effect was toll-like receptor 9-dependent, as GpC negID35 failed to suppress antigen-specific IgE production. ID35 activated the specific subset of CD11c+CD8a+ dendritic cells, which are associated with T-helper 1 (Th1)-type systemic responses, and effectively induced interferon-gamma (IFN-gamma) production by CD4+ T cells in OVA-challenged mice. These immunoregulatory effects of ID35 were comparable with those induced by the murine prototype ODN 1826. Thus, ID35 is the first ISS-ODN with such a strong immunostimulatory and IgE suppressor activity to be found in immunobiotic bacterial DNA.

Factors affecting neostigmine reversal of vecuronium block during sevoflurane anaesthesia

We examined the influence of the concentration of sevoflurane and the degree of muscle block at the time of reversal on the activity of neostigmine. Ninety ASA 1-2 patients were anaesthetised with 0.2, 0.7 or 1.2 MAC of sevoflurane (30 patients each) in 66% nitrous oxide in oxygen. The electromyographic (EMG) response of the adductor digiti minimi was monitored at 20-s intervals after train-of-four stimulation of the ulnar nerve. The initial neuromuscular block was produced by vecuronium 100 micrograms.kg-1. When the amplitude of the first response (T1) values had recovered to 10%, 25% or 40% of the control, neostigmine 40 micrograms.kg-1 was administered. The train-of-four ratio values were recorded at 1-min intervals during the subsequent 15-min period. Higher endtidal concentrations (p < 0.0001) and more pronounced block at the time of reversal (p < 0.0001) were associated with a delayed recovery in the train-of-four ratio. In addition, the train-of-four ratio 15 min after neostigmine administration was more dependent on the sevoflurane concentration than on the degree of block present (p < 0.0001). These results confirm that neostigmine (40 micrograms.kg-1) can reverse vecuronium-induced but not sevoflurane-induced neuromuscular block.

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 (1 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 micrograms.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 micrograms.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 micrograms.kg-1) and isoflurane groups (851 micrograms.kg-1) were observed than in the fentanyl-diazepam-nitrous oxide group (339 micrograms.kg-1) (P < 0.05).

CONCLUSION

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