Anesth Pain Med.  2018 Jan;13(1):34-39. 10.17085/apm.2018.13.1.34.

The effects of a loading dose of phenylephrine for the prevention of maternal hypotension under spinal anesthesia for Cesarean section

• Park SH
• Lee JY
• Kim ST

• KMID: 2436053
• DOI: http://doi.org/10.17085/apm.2018.13.1.34

Abstract

BACKGROUND
Phenylephrine is frequently used for the prevention and treatment of maternal hypotension in patients undergoing Cesarean section. But there are limited studies about the prophylactic effect on maternal hypotension with a loading dose, followed by a continuous infusion of phenylephrine. Therefore, we investigated the additional effect of a loading dose infusion of phenylephrine on the prevention of maternal hypotension, and compared it to a continuous infusion of phenylephrine without a loading dose.
METHODS
Following spinal anesthesia, sixty-four patients were randomly assigned to one of two groups according to the phenylephrine administration regimen: group L (n = 32; loading dose [200 µg/min] just before continuous infusion [20 µg/min]) and group C (n = 32; continuous infusion [20 µg/min] without a loading dose). We measured the blood pressure and heart rate, and assessed the incidence of hypotension, nausea, vomiting, dosage of used rescue drugs and fetal parameters.
RESULTS
At 2, 4 minutes after administration of phenylephrine, group L showed a higher systolic blood pressure and lower heart rate than group C. However, there were no significant differences in the incidence of hypotension, nausea, vomiting and the dosage of used rescue drugs. There were no significant differences in the fetal parameters such as Apgar scores and umbilical pH.
CONCLUSIONS
The loading dose infusion of phenylephrine had no beneficial positive effect on the prevention of maternal hypotension.

Keyword

Cesarean section; Hypotension; Phenylephrine

MeSH Terms

Anesthesia, Spinal*
Blood Pressure
Cesarean Section*
Female
Heart Rate
Humans
Hydrogen-Ion Concentration
Hypotension*
Incidence
Nausea
Phenylephrine*
Pregnancy
Vomiting
Phenylephrine

Figure

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  Fig. 1 Flow diagram of the patients. Sixty-four patients were randomized for the study. Group L: loading dose (200 μg/min) of phenylephrine followed by a continuous infusion (20 μg/min), Group C: continuous infusion of phenylephrine without a loading dose.

• 

  Fig. 2 Changes of (A) systolic blood pressure (SBP) and (B) heart rate (HR) of perianesthetic period. Values are expressed as mean ± SD. Group L: loading dose (200 μg/min) of phenylephrine followed by a continuous infusion (20 μg/min), Group C: continuous infusion of phenylephrine without a loading dose. SBPC: SBP before phenylephrine infusion, SBP0–20: SBP at 0–20 minutes after phenylephrine infusion. HRC: HR before phenylephrine infusion, HR0–20: HR at 0–20 minutes after phenylephrine infusion. *P < 0.05 between two groups.

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