Prophylactic Phenylephrine Administration between 50 and 100 Micrograms Intravenous Slow Injection on Hypotension and Bradycardia after Spinal Anesthesia in Patients Undergoing Cesarean Section: A Randomized, Single-Blind Study
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Abstract
Introduction: According to the international recommendation, phenylephrine should be used routinely and preferably prophylactically via single-dilution technique, and/or prefilled syringes with or without a smart pump for management of hypotension after spinal anesthesia during cesarean section. However, there are several limitations of the use of phenylephrine, equipment and routine administration of this drug is not popular in Thailand. Objectives: To compare the incidence of hypotension, bradycardia and the other side effects after prophylactic phenylephrine administration between 50 and 100 micrograms (mcg) intra- venous slow injection after spinal anesthesia in patients undergoing cesarean section. Methods: Sixty-two patients undergoing elective cesarean section during October to December 2021. Coloading with 0.9% NaCl intravenous during performing spinal anesthesia with 0.5% hyperbaric bupivacaine 2.2 ml. plus preservative-free morphine 0.2 mg. After finishing spinal anesthesia, the patients were randomized into two groups. P50 (n=31) and P100 (n=31) groups which were prophylactic administered by IV slow injection of phenylephrine 50 and 100 mcg in 10 ml within 30 seconds with opening three ways of 3-way stopcock to imitate the function of a smart pump, respectively. Hypotension (SBP <10% of baseline) was rescued with phenylephrine 100 mcg and bradycardia was treated with atropine 0.6 mg. The other side effects were recorded. Results: The incidence of hypotension in P100 group was significantly lower than in P50 group (P=0.04). There were no statistically significant differences in bradycardia, arrhythmia, total dose of phenylephrine, reactive hypertension (SBP >10% of baseline), maternal nausea and vomiting score as well as Apgar score between the two groups. Conclusions: Prophylactic phenylephrine administration 100 mcg. IV slow injection within 30 seconds with opening three ways of 3-way stopcock to imitate the function of a smart pump is effective to lower the incidence of hypotension than 50 mcg and severe side effects were not found after spinal anesthesia for cesarean section.
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