Effects of arterial carbon dioxide on recovery from rocuronium-induced neuromuscular blockade in anesthetized patients

Background: Respiratory function can be impaired during general anesthesia involving neuromuscular blockers such as rocuronium. However, the magnitude of the problems and the efficacy of their reversal with antagonistic drugs are not known. Objective: To investigate the effects of arterial carbon dioxide (PaCO2) on recovery from rocuronium-induced neuromusuclar blockade with or without antagonism by neostigmine. Methods: Ninety patients were randomly divided into six groups; group I and A, normal PaCO2 (35-45mmHg), group II and B, low PaCO2 (30-35mmHg), group III and C, high PaCO2 (45-50mmHg). The extent of neuromuscular blockade was evaluated by train-of-four (TOF) -watch accelerograph. Anesthesia was induced with intravenouspropofol, fentanyl, and rocuronium 0.6mg/kg. Additional injection of rocuronium 0.15mg/kg per time was given whenever the first twitch of TOF (T1) recovered to 25%. The residual neuromuscular blockade was antagonized with neostigmine 0.02mg/kg in the groups I, II and III, when T1 reached 25%. The duration from T1 25% to 75%was recorded and defined as the recovery index and that from T1 25% to TOFR 0.9 was the recovery time.