Prophylactic infusion of phenylephrine is effective in attenuating the decrease in regional cerebral blood volume and...

Area of Science:

• Anesthesiology
• Obstetrics
• Neuroscience

Background:

• Spinal anesthesia for cesarean delivery can cause hypotension, reducing maternal cerebral blood volume and oxygenation.
• Near-infrared spectroscopy (NIRS) is utilized to monitor cerebral hemodynamics.
• Phenylephrine is a vasopressor used to manage hypotension.

Purpose of the Study:

• To evaluate the efficacy of prophylactic phenylephrine infusion in attenuating decreases in maternal regional cerebral blood volume and oxygenation during spinal anesthesia for cesarean section.
• To compare the effects of different phenylephrine infusion rates (25 µg/min and 50 µg/min) versus a saline placebo.

Main Methods:

• A randomized controlled trial involving 60 patients undergoing spinal anesthesia for cesarean section.
• Patients were assigned to receive intravenous infusions of saline (P0), phenylephrine 25 µg/min (P25), or phenylephrine 50 µg/min (P50).
• Mean arterial pressure, heart rate, and NIRS-derived parameters (oxyhemoglobin, deoxy-hemoglobin, total-hemoglobin, tissue oxygenation index) were measured at one-minute intervals for 20 minutes post-injection.

Main Results:

• Phenylephrine groups (P25, P50) exhibited significantly higher mean arterial pressure compared to the saline group (P0).
• Heart rate decreased dose-dependently with phenylephrine infusion.
• Total hemoglobin levels were significantly higher in phenylephrine groups, indicating increased cerebral blood volume. The P50 group showed the largest decrease in tissue oxygenation index, followed by P0 and P25.

Conclusions:

• Prophylactic phenylephrine infusion effectively suppresses decreases in regional cerebral blood volume and oxygenation following spinal anesthesia for cesarean section.
• Phenylephrine at 25 µg/min appears to be a particularly effective dose for maintaining cerebral hemodynamics.
• These findings support the use of phenylephrine to optimize maternal brain perfusion during cesarean delivery under spinal anesthesia.