BACKGROUND: Cisatracurium is a nondepolarizing muscle relaxant. It less likely release histamine and has better cardiovascular stability. It presumably undergoes pH and temperature- dependent, nonenzymatic chemical process, Hofmann reaction. In vitro studies, Hofmann reaction was enhanced with increasing pH, but, in vivo the influence of acid-base imbalance is not well defined. METHODS: To evaluate the effects of acid-base imbalance on the neuromuscular blockade of cisatracurium in the cat, we induced acid-base imbalance and performed cumulative dose-response studies. RESULTS: ED50 of the cisatracurium was significantly reduced in all groups. Dose-response curves from all acid-base imbalance groups did not have significant differences in slopes. But, all showed shift-to-left when compared with control curve, showing decreased ED50. Duration of action was not affected. Recovery index was significantly changed in respiratory and metabolic alkalosis. CONCLUSIONS: It may be concluded that acid-base imbalance significantly augmented the potency of cisatracurium, but, changes of recovery index in this study may be resulted from systemic instability such as unstable hemodynamic state by the prolonged experiment.
Acid-Base Imbalance* ; Alkalosis ; Animals ; Cats* ; Chemical Processes ; Hemodynamics ; Histamine ; Hydrogen-Ion Concentration ; Neuromuscular Blockade*