Up-Down Determination of the ED90 of Metaraminol to Treat Hypotension During Cesarean Section

Up-Down Determination of the ED90 of Metaraminol to Treat Hypotension During Elective Cesarean Section

The purpose of this study is to find the best dose of metaraminol to be used in patients during elective cesarean sections.

The purpose of this study is to determine the effective dose 90% (ED90) of metaraminol to treat hypotension after spinal anesthesia in elective cesarean sections (CS). It is a double-blind study that uses the biased-coin up-down sequential allocation method to determine the ED90 of metaraminol.

Baseline systolic blood pressure (SBP) will be determined by three automated measures 3 minutes apart just before CS. During the period from induction of spinal anesthesia to fetal delivery SBP will be monitored every minute and metaraminol will be administered every time it is lower than baseline value. If SBP falls below 80% of baseline value, the treatment will be considered a failure. An adequate response will be defined as the absence of hypotension during the study period.

Inclusion Criteria:

• Elective CS under spinal anesthesia
• Normal singleton pregnancy beyond 36 weeks gestation
• ASA physical status I/II
• Age over 18 years

Exclusion Criteria:

• Patient refusal
• Allergy to metaraminol
• Preexisting or pregnancy-induced hypertension
• Cardiovascular or cerebrovascular disease
• Fetal abnormalities