Background and Goal of Study: Resistance to the actions of non-depolarizing neuromuscular blocking agents (NMBAs) are commonly associated with chronic exposure to glucocorticoid. It is known that chronic dexamethasone treatment induces alteration in immature subunits of nicotinic acetylcholine receptor (nAChR) and upregulation of nAChR. Furthermore, upregulation and spreading of acetylcholine receptors also induces the resistance to NMBAs. For this reason, we can assume that sugammadex-induced recovery in subjects with long term treatment of dexamethasone is faster than in subjects without dexamethasone exposure. The goal of this study is to evaluate the recovery profile of the rocuronium- induced neuromuscular blockade after sugammadex administration.

Materials and Methods: Thirty adult male Sprague-Dawley rats (180-220 g) were randomized into three groups (n=10 per group). The Dexa group received a daily IP injection of dexamethasone (500 μg/kg) suspended in 0.9% normal saline for 15 days. The Control group received an equivalent volume of 0.9% normal saline daily for 15 days. The same amount of food consumed by the Dexa group was provided daily to the Pair-fed group. Rats were anesthesized with AlfaxanTM and then tracheostomy and internal jugular catheterization were done. Both sciatic nerves were exposed and stimulated for twitch tension of the tibialis anterior muscle. Train-of-four (TOF) stimulations were applied every 12 seconds. After administering rocuronium of 3.5 mg/kg, the time to T2 (The second twitch of TOF) recovery was recorded. When T2 appeared, sugammadex of 0.5 mg/kg was administered, then the recovery time of TOF ratio to 0.9 was recorded.

Results and Discussion: The time to T2 recovery was significantly shortened in the Dexa group compared with the Control group and the Pair-fed group (2.9 min [95% confidence intervals, 2.2-3.6 min] vs. 5.0 [4.2-5.8] and 5.1 [4.1-6.1], P = 0.001, respectively) while no significant difference was observed between the Control group and the Pair-fed group (P = 0.996). There were no significant differences in the recovery time to TOF ratio to 0.9 among groups (3.1 min [1.8-4.4 min], 4.3 [2.6-5.9], and 4.0 [1.9-6.1], P = 0.531).

Conclusion: As previous studies reported, resistance to rocuronium was observed in rats with chronic exposure to dexamethasone. However, the neuromuscular recovery time after the use of sugammadex was not significantly different among the groups.



03 / The effect of chronic exposure to dexamethasone on rocuronium-induced neuromuscular blockade and sugammadex reversal in in vivo study of rats.