Impact of Prophylactic Ephedrine on Fetal Heart Tracing and Uterine Tetanic Contraction After CSE

Labor analgesia is an important component of the care of laboring patients. A known side effect of combined spinal and epidural anesthesia (a type of labor analgesia) is an increased incidence of category II fetal heart rate tracing (defined below) and low blood pressure. The study team aims to study if a prophylactic dose of ephedrine will decrease the occurrence of this type of tracing after combined spinal epidural (CSE) anesthesia placement. Ephedrine is not currently routinely used as prevention for category II tracings or low blood pressure. The use of Ephedrine in this study is investigational (this is the first time that the drug has been studied for its effect on these conditions).

Fetal heart rate (FHR) tracings are classified into three categories. In clinical practice, FHR tracing categories are used as a guide to obstetric management and suggest the following approach:

• Category I tracing is "reactive" and reassuring → may continue labor
• Category II tracing is neither category I nor category III. For obvious reasons, category II is the broadest and largest category, consisting of various FHR tracing patterns that do not fit into either category I or category III.
• Category III tracing is non-reassuring → expedited vaginal or cesarean delivery recommended.

A Category II tracing is not diagnostic. Most pregnancies have at least one Category II tracing. There is not always an identifiable reason for a Category II tracing.

Ephedrine is a medication that causes an increase in heart rate and blood pressure while also causing some degree of relaxation of the uterus therefore improving uterine blood flow. It has been used in the obstetric population for over 50 years without issues. The dose that the research team will administer, 7.5 mg, is below the dose the research team will often administer to treat hypotension (low blood pressure).