Intubating conditions after vecuronium and atracurium given in divided doses (the priming technique)

Abstract

Intubating conditions have been assessed at 60 s following administration of vecuronium 0.1 mg kg-1 or atracurium 0.5 mg kg-1 given either as a single dose after induction of anaesthesia with thiopentone or in divided doses; vecuronium 0.015 mg kg-1 followed 4 or 6 min later by 0.085 mg kg-1, or atracurium 0.075 mg kg-1 followed 4 or 6 min later by 0.425 mg kg-1. In the divided dose groups the smaller initial (priming) dose was given prior to induction of anaesthesia. Onset and duration of clinical relaxation were assessed using a peripheral nerve stimulator. The intubating conditions at 60 s improved significantly, with the use of relaxants in divided doses being acceptable in 80 and 70% of patients, respectively, with vecuronium and atracurium, but the conditions are not as good as those commonly found using suxamethonium. Priming at 6 min has no advantage over priming at 4 min. The onset of complete block was accelerated with priming, but the difference was not significant. The duration of clinical relaxation of vecuronium was significantly prolonged by giving it in divided doses. Unpleasant awareness of muscle weakness was observed in 15 patients, requiring early induction of anaesthesia in five of them.

Dose preparatória versus injeção única: estudo comparativo entre diferentes doses de cisatracúrio

“…Some authors [14][15][16][17][18] have reported that the priming dose is unable to induce undesirable effects in awaken patients before anesthetic induction, but may, however, uncover their sensitivity to neuromuscular blockers (NMBs). These findings are opposed to those observed in other studies where, although neuromuscular blockers fractional doses allowed for a faster blockade onset as compared to bolus administration, this technique was not risk-free 13,[19][20][21][22][23][24][25][26] . Among priming dose-related side-effects, there are muscle weakness (ptosis, diplopia, difficult swallowing), pulmonary function tests depression, hypoventilation, decreased ability to cough, pulmonary volume decrease and potential oxygenation deterioration, pharyngeal muscles relaxation with a higher risk for gastric content regurgitation [21][22][23][24][25][26][27] .…”

“…These findings are opposed to those observed in other studies where, although neuromuscular blockers fractional doses allowed for a faster blockade onset as compared to bolus administration, this technique was not risk-free 13,[19][20][21][22][23][24][25][26] . Among priming dose-related side-effects, there are muscle weakness (ptosis, diplopia, difficult swallowing), pulmonary function tests depression, hypoventilation, decreased ability to cough, pulmonary volume decrease and potential oxygenation deterioration, pharyngeal muscles relaxation with a higher risk for gastric content regurgitation [21][22][23][24][25][26][27] . Due to partial neuromuscular block after the priming dose, including awaken patients, with a consequent discomfort and respiratory failure evidenced by significant oxygen saturation decrease and severe muscle weakness, monitoring is mandatory 19 .…”

“…Alguns autores 14,18 relataram que a dose preparatória não é capaz de ocasionar efeitos indesejáveis no paciente acordado, antes da indução anestésica, podendo, no entanto, revelar sensibilidade destes aos BNM. Estes achados são contrários aos observados em outros estudos, que relataram que, embora o emprego de doses fracionadas de bloqueadores neuromusculares proporcione instalação mais rápida do bloqueio do que quando a mesma dose é administrada em bolus, esta técnica não é isenta de riscos 13,[19][20][21][22][23][24][25][26] . Entre os efeitos indesejáveis atribuídos a dose preparatória, encontram-se fraqueza muscular (ptose, diplopia, dificuldade de deglutição), depressão dos testes de função pulmonar, hipoventilação, redução da habilidade para tossir, redução do volume pulmonar e potencial deteriorização na oxigenação, relaxamento dos músculos da faringe com maior risco de regurgitação gástrica [21][22][23][24][25][26][27] .…”

Priming with nondepolarizing relaxants for rapid tracheal intubation: a doubleblind evaluation

“…This is consistant with the results of Mirakhur et al 7 Our data suggezt that a four-minute priming interval is at least as effective (and perhaps superior) to a seven-minute interval. Our conclusion concerning priming intervals must remain qualified since our study was conducted in separately randomized phases.…”

The dose effect of ephedrine on the onset time and intubating conditions after cisatracurium administration

“…67, No. 1, July 2014 Pretreated ephedrine to cisatracurium ficulty swallowing, and voice disorders during the relatively long priming interval [13]. Additionally, this previous study did not simultaneously evaluate the degree of NMB after atracurium administration.…”