ผลของการเปลี่ยนแปลงภาวะความเป็นกรดและด่างของร่างกายต่อการออกฤทธิ์คลายกล้ามเนื้อของ atracurium ในแมว

Abstract

This study was to assess the effects of respiratory acidosis, respiratory alkalosis, metabolic acidosis and metabolic alkalosis on the neuromuscular blocking action of atracurium (BW 333A) in anaesthetized cats. After a slow infusion of atracurium until a constant depression of muscle contraction was obtained, the inhalation of 5 % CO₂ ± 95 % O₂ for 10 munites which induced respiratory acidosis (pH 7.086 ± 0.19, PaCO₂ 49.22 ± 0.27 mmHg, n=6) significantly increased the atracurium steady state block, by 16.63 ± 2.33 % (P<0.05) in the tibialis anterior, and 15.50 ± 1.12 % (P<0.05) in the soleus whereas increasing minute ventilation 2-3 folds (hyperventilation) for 10 minutes which induced respiratory alkalosis (pH 7.503 ± 0.016, PaCO₂ 17.57 ± 1.06 mmHg, n=6) non-significantly decreased the atracurium steady state block by 4.57 ± 1.05 % (p>0.05) in the tibialis anterior and 9.84 ± 1.09 % (p>0.05) in the soleus. At the same constant block induced by atracurium pretreatment, infusion of 0.15 mmol/kg/min of 0.5 mol/l ascorbic acid for 10 minutes which produced metabolic acidosis (pH 7.082 ± 0.021, Paco2 24.75 ± 1.34 mmHg, n=6) Significantly increased the atracurium steady state block by 21.73 ± 3.99 % (p<0.001) in the tibialis anterior and 18.34 ± 1.64 % (p<0.05) in the soleus, whereas infusion of 0.80 mmol/kg/min of 0.5 mol/l sodium carbonate for 10 minutes, which produced metabolic alkalosis (pH 7.634 ± 0.009, PaCO₂ 21.4 ± 1.61 mmHg, n = 6 ) non-sjgnificantly decreased the atracurium steady state block by 7.70 ± 2.13 % (p>0.05) in the tibialis anterior and 8.39 ± 3.06 % (p>0.05) in the soleus.