Variable Rate Phenylephrine Infusion for Prevention of Spinal-induced Hypotension for Cesarean Delivery
Status:
Completed
Trial end date:
2013-01-01
Target enrollment:
Participant gender:
Summary
Rapid administration of crystalloid immediately after induction of spinal anesthesia (coload)
to be more effective in terms of managing hypotension as compared to administering
crystalloid before spinal anesthesia (preload).
Phenylehrine infusion is a safe and effective way to reduce incidence and frequency of
hypotension during SA for cesarean delivery. Hypotension was virtually eliminated by use of
high-dose prophylactic phenylephrine infusion at a rate of 100 µg/min and rapid crystalloid
coload up to two liters (administration at the time of SA). However, incidence of reactive
hypertension was frequent up to 47% with decrease in maternal heart rate (HR). This may raise
concern in patients in whom increase of blood pressure may be detrimental, like chronic
hypertension and in the presence of a compromised uteroplacental blood flow. A recent study
found that infusing phenylephrine at a fixed rate of 75 and 100 ug/min is associated with
more episodes of hypertension than placebo or the lower infusion rates of 25 and 50 ug/min
respectively. However, there was no reduction in the number of physician interventions
(phenylephrine boluses and stopping the infusion) needed to maintain maternal systolic blood
pressure within 20% of baseline among all groups. Prophylactic fixed rate infusions may have
limited application in clinical practice, and a variable rate (i.e. modifying the rate
according to hemodynamics) has been advocated. The bolus administration of phenylephrine to
treat hypotension is still commonly used, but requests multiple interventions from the
anesthesiologists and is time consuming.
Eighty patients scheduled for cesarean delivery under spinal anesthesia will be assigned to
one of two groups. Immediately after spinal injection, rapid crystalloid colaod of lactated
Ringer of 15 mL/kg over a period of 10-15 min will be initiated. Patients in Group I will
receive infusion of normal saline (placebo) and patients in group II variable infusion rate
of phenylephrine started at 0.75 ug/kg (close to the dose of 50 ug/min recommended for fixed
infusion rate). The number of interventions needed to maintain maternal systolic blood
pressure within 20% of baseline, hemodynamic performance, intraoperative nausea and vomiting,
and umbilical cord blood gases will be compared between the two groups.
We will define a reliable and safe method to ensure maternal hemodynamic stability during
spinal anesthesia for cesarean delivery with the least physician interference.