Prolonged neuromuscular block after rocuronium in postpartum patients.
Postpartum patients have not completely lost the weight gained during pregnancy. Drug dosing according to total body weight (TBW) can cause exaggerated effects and dosing by lean body mass (LBM) may provide a more consistent response despite the increased weight. We compared the duration of a rocuronium neuromuscular block in 22 women undergoing postpartum tubal ligation 31--79 h after delivery, with that in 22 women undergoing gynecological surgery. Anesthesia was induced and maintained with propofol and alfentanil. Half of the patients in each of the Postpartum and Control groups received a bolus dose of rocuronium 0.6 mg/kg TBW and the remaining half received rocuronium 0.6 mg/kg LBM. Neuromuscular block was monitored by electromyography and the ulnar nerve was stimulated transcutaneously using a train-of-four pattern. When rocuronium was given by TBW, median (range) duration of neuromuscular block until 25% recovery of the first twitch response was longer in the Postpartum group, 35.3 (29.7--48.7) min, compared with the Control group, 24.8 (21.5--28.6) min (P < 0.001). After dosing by LBM, the duration of block was similar between groups. The prolonged block with rocuronium in the Postpartum patients can be explained by relative drug overdose when dose calculation is based on their temporarily increased body weight.


CONCLUSIONS
Neuromuscular block is prolonged in the postpartum period after standard doses of rocuronium. Drug administration according to lean body mass will produce a more consistent duration of block.
Gin
Tony
T
Departments of Anaesthesia and Intensive Care and Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong. tgin@cuhk.edu.hk
Chan
Matthew T V
MT
Chan
Ka Lai
KL
Yuen
Pong Mo
PM
D000328:Adult; D000732:Androstanols / Q000494:pharmacology*; D001835:Body Weight; D005260:Female; D006801:Humans; D009469:Neuromuscular Junction / Q000187:drug effects*; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology*; D049590:Postpartum Period / Q000502:physiology*; D011247:Pregnancy; D000077123:Rocuronium; D013997:Time Factors
D000732:Androstanols; D003473:Neuromuscular Nondepolarizing Agents; D000077123:Rocuronium