Effect of Doxapram on the Recovery from Vecuronium from Vecuronium of Mivacurium-induced Neuromuscular block in the Rabbit

Choi, Jong Ho; Jung, Eun Yong

Abstract

Doxapram as a potent respiratory stimulant is one of attempts to solve respiratory problem and has been known to be effective for many years. But one study suggested that the presence of doxapram retarded neostigmine-induced antagonism of vecuronium effect. So we studied the effect of doxapram on the reverse of neuromuscular block when doxapram was injected with different dose. 60 rabbits were divided into 6 groups. Vecuronium was used in Group 1~3 and Mivacurium was used in Group 4~6 as a muscle relaxant. When the first twitch of TOF response reappeared from the complete block with a muscle relaxant (T1 onset), we administered neostigmine 0.05 mg/kg and saline 0.3 ml i.v. in Group 1, 4(VS, MS), neostigmine 0.05 mg/kg and doxapram 0.5 mg/kg i.v. in Group 2, 5(VDP1, MDP1), and neostigmine 0.05 mg/kg and doxapram 3 mg/kg i.v. in Group 3, 6(VDP2, MDP2). Two recovery time, from T1 onset to T1 25% and from T1 25% to T1 75%, and TR(ratio ; T4 twitch/T1 twitch) at T1 75% were measured. For the hemodynamic effect of doxapram, Blood pressure, heart rate and arrythmia were observed before and after doxapram injection too. The results are as follows. 1) Recovery time from T1 onset to T1 25% are 2'30"+/-0'29"(min'sec") in VS, 3'07"+/-0'4l"(minsec") in VDPl, 1'49"+/-0'17"(min'sec") in VDP2, 2'34"+/-0'17"(min'sec") in MS, 2'41"+/-0'25"(min'sec") in MDP1, 1'52"+/-0'39"(min'sec") in MDP2. 2) Recovery time from T1 25% to T1 75% are 4'58"+/-0'52"(min'sec") in VS, 6'10"+/-1'17"(min'sec") in VDP1, 3'38"+/-0'33"(min'sec") in VDP2, 4'38"+/-'0'57"(min'sec") in MS, 5'10"+/-0'55"(min'sec") in MDP1, 3'15"+/-0'38"(min'sec") in MDP2. 3) TR at T1 75% are 76.6+/-7.7% in VS, 82.4+/-3.4% in VDP1, 83.8+/-4.5% in VDP2, 81.4+/-2.3% in MS, 89.8+/-2.3% in MDP1, 89.8+/-1.5% in MDP2. 4) Heart rate, cardiac rhythm, systolic and diastolic pressure before and after doxapram injection were not significantly changed. In conclusion, simultaneous administration of neostigmine and low dose doxapram delayed recovery from the neuromuscular block, but high dose doxapram did not.