Comparison of Onset and Duration of Rocuronium Induced Neuromuscular Block Between 2nd Trimester Pregnant and Non-pregnant Women

Pregnancy is associated with major changes of the body's physiological status and composition.

These changes may modify the pharmacologic and/or pharmacokinetic profile of some drugs. Pharmacodynamic and pharmacokinetic changes in the 1st trimester during pregnancy are attributed to the following factors; Increase in plasma volume, heart rate and cardiac output; decrease in blood pressure due to decrease of systemic resistance and relative decrease of hepatic circulation and the aggravation of hepatic dysfunction. These changes intensify as pregnancy progresses into the 3rd trimester and take their effect on the onset time and duration of muscle relaxants.

Rocuronium and the steroidal non-depolarizing muscle relaxant like vecuronium is mostly excreted with bile by hepatic metabolism and classified as the FDA pregnancy category B, and is widely used in general anesthesia of pregnant women. Previous studies reported onset time of rocuronium is affected by cardiac output, blood circulation time of the whole body, and muscle perfusion. Accordingly, many researches were conducted under the assumption of onset time and duration being affected by physiologic changes during pregnancy. For example, in the research where vecuronium was used as muscle relaxant for pregnant woman undergoing C-sec, onset of vecuronium was significantly shorter than that of the control group and duration was longer. In a study investigating rocuronium used for patients right after delivery, onset time was shorter and duration was longer than that of the control group.

However, previous research mostly focused on the 3rd trimester, while there have been only a few studies of onset time and duration of rocuronium in non-obstetric surgery such as the transabdominal cervicoisthmic cerclage (TCIC) or Mcdonald surgery which are performed under general anesthesia during 2nd trimester. In this research, onset time and duration of rocuronium, which is widely used for general anesthesia in 2nd trimester pregnant females, will be compared with those of patients in the control group.