Phenylephrine in Spinal Anesthesia in Preeclamptic Patients

Summary

Hypotension remains a common clinical problem after induction of spinal anesthesia for cesarean delivery. Maternal hypotension has been associated with considerable morbidity (maternal nausea and vomiting and fetal/neonatal acidemia). Traditionally, ephedrine has been the vasopressor of choice because of concerns about phenylephrine's potential adverse effect on uterine blood flow. This practice was based on animal studies which showed that ephedrine maintained cardiac output and uterine blood flow, while direct acting vasoconstrictors, e.g., phenylephrine, decreased uteroplacental perfusion. However, several recent studies have demonstrated that phenylephrine has similar efficacy to ephedrine for preventing and treating hypotension and may be associated with a lower incidence of fetal acidosis. All of these studies have been performed in healthy patients undergoing elective cesarean delivery.

Preeclampsia complicates 5-6% of all pregnancies and is a significant contributor to maternal and fetal morbidity and mortality. Many preeclamptic patients require cesarean delivery of the infant. These patients often have uteroplacental insufficiency. Given the potential for significant hypotension after spinal anesthesia and its effect on an already compromised fetus, prevention of (relative) hypotension in preeclamptic patients is important. Spinal anesthesia in preeclamptic patients has been shown to have no adverse neonatal outcomes as compared to epidural anesthesia when hypotension is treated adequately. Due to problems related to management of the difficult airway and coagulopathy, both of which are more common in preeclamptic women, spinal anesthesia may be the preferred regional anesthesia technique. Recent studies have demonstrated that preeclamptic patients may experience less hypotension after spinal anesthesia than their healthy counterparts. To our knowledge, phenylephrine for the treatment of spinal anesthesia-induced hypotension has not been studied in women with preeclampsia. The aim of our study is to compare intravenous infusion regimens of phenylephrine versus ephedrine for the treatment of spinal anesthesia induced hypotension in preeclamptic patients undergoing cesarean delivery. The primary outcome variable is umbilical artery pH.

Conditions

• Preeclampsia
• Hypotension

Interventions

DRUG

Ephedrine

Ephedrine concentration: 8 mg/mL. The infusion will be initiated immediately after completion of the spinal injection at a rate of 1 mL/min and continued for a minimum of 2 min after which the infusion will be stopped, continued or increased based on the SBP each minute. After each SBP measurement the infusion will be stopped if SBP \> 80% baseline, and the infusion will be continued or restarted if the SBP is approximately equal to 80% baseline. The infusion will be increased by 1 mL/min if the SBP \< 80% baseline. Each time there is hypotension the patient will receive a 1 mL IV bolus of the study solution and the infusion will be increased by 1 mL/min until delivery.

DRUG

Phenylephrine

Phenylephrine concentration: 100 mcg/mL. The infusion will be initiated immediately after completion of the spinal injection at a rate of 1 mL/min and continued for a minimum of 2 min after which the infusion will be stopped, continued or increased based on the SBP each minute. After each SBP measurement the infusion will be stopped if SBP \> 80% baseline, and the infusion will be continued or restarted if the SBP is approximately equal to 80% baseline. The infusion will be increased by 1 mL/min if the SBP \< 80% baseline. Each time there is hypotension the patient will receive a 1 mL IV bolus of the study solution and the infusion will be increased by 1 mL/min until delivery.

Sponsors & Collaborators

• Northwestern University

  lead OTHER

Principal Investigators

• David Walega, M.D. · Northwestern University

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

60 Years

Sex

FEMALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2006-07-31

Primary Completion

2016-12-31

Completion

2016-12-31

Countries

• United States

Study Locations