The Effects of Magnesium on Pipecuronium-induced Neuromuscular Blockade and its Reversal in the Isolated Rat Phrenic Nerve-Hemidiaphragm.

Kim,  Jong Sool; Ryu,  Tae Gan; Kong,  Myoung Hoon; Lee,  Mi Kyeong; Yoon,  Suk Min

doi:1996.31.2.150

Korean Journal of Anesthesiology 1996;31(2):150-155.
DOI: https://doi.org/10.4097/kjae.1996.31.2.150

Jong Sool Kim, Tae Gan Ryu, Myoung Hoon Kong, Mi Kyeong Lee, Suk Min Yoon

Department of Anesthesiology, Korea University, College of Medicine, Seoul, Korea.

Abstract

BACKGROUND
Magnesium sulfate (MgSO4) is widely utilized in the treatment of preeclamptic hyperreflexia. It is well known that magnesium enhances nondepolarizing neuromuscular blockade. Eclamptic convulsions are almost always prevented by magnesium in plasma concentrations of 4 to 7 mEq/L.
METHODS
The effects of various concentration of magnesium on the potency and reversibility of pipecuronium were investigated in vitro rat phrenic nerve-hemidiaphragm. The phrenic nerve-hemidiaphragm was dissected and suspended in organ bath containing modified Krebs' solution. Forty samples were divided into 4 groups (n=10 in each group). Group I was studied at the physiologic magnesium concentration(2.4 mEq/L, control group). Group II, III, IV were studied at the concentration of 4, 5.5, and 7 mEq/L, respectively. In each group, we added pipecuronium until twitch height decreased more than 90% of initial level. To compare the recovery, we added neostigmine and calcium, and then, measured TOF ratio.
RESULTS
The amounts of added pipecuronium were 73.8+/-15.2 microgram (mean+/-S.D.) in Group I, 38.1+/-5.0 microgram in Group II, 33.0+/-4.1 microgram in Group III and 16.1+/-1.7 microgram in Group IV. The amounts of pipecuronium in Group II, III, IV were significantly less than Group I. After the addition of neostigmine, the values of TOF ratio were under 0.6 in all groups. But after the addition of calcium, all groups were recovered with TOF ratio over 0.85 except Group I.
CONCLUSIONS
This study indicated that the increased magnesium concentration potentiated pipecuronium-induced neuromuscular blockade and at higher level, it was more apparent. Neostigmine was not significantly effective to reverse the pipecuronium-induced neuromuscular blockade potentiated with magnesium. But calcium was significantly effective.

Key Words: Antagonist; neuromuscular relaxants neostigmine; Ion magnesium; calcium; Neuromuscular relaxants pipecuronium