Effect of Intravenous Vasopressor on Spread of Spinal Anesthesia and Fetal Acid-base Equilibrium

Abstract

Patients were similar in baseline characteristics and the risk for PONV, intraoperative management, and intraoperative symptoms of nausea and vomiting. Intraoperative use of fentanyl, antiemetics, or vasopressors did not differ among the three groups. Fetal status at delivery did not differ among groups, nor did postoperative analgesic requirements. The VAS for nausea in those with the TDS patch at the 2 to 6 hours time period (7 mm) and the incidence of vomiting and all emesis in the TDS patch group at the 6 to 24 hours time period (5% and 6%, respectively) were significantly lower in women in the scopolamine group compared with those receiving placebo (15 mm and 17% and 20%, respectively). Retching did not differ among the groups. Overall rates of all emesis were 59.3% in the placebo group, 40% in the TDS group, and 41.8% in the ondansetron group (P = 0.25). Rescue antiemetics were used in 35% to 45% of patients overall in the first 24 hours postoperatively, with a trend toward less use in the TDS group at 2 to 6 hours and 6 to 24 hours (0.05<P<0.1). No patient discontinued drug use because of side effects. Dry mouth and blurry vision were more common (19% and 6% respectively) in the TDS group at 6-24 hours compared to the placebo group but not in the early time periods.Overall rates for all emesis were reduced by one-third when scopolamine patches or prophylactic ondansetron were used to prevent PONV after cesarean section. TDS patches are less costly than IV ondansetron and the antiemetic effect may last for up to 72 hours compared to a much shorter time with ondansetron. The low cost and long duration of TDS may make it an attractive therapy for PONV prevention following cesarean section. COMMENTIn the September edition of Anesthesia and Analgesia, Miriam Harnett and her colleagues present an elegant study evaluation of the use of TDS on the incidence of PONV after cesarean delivery. Their study confirms findings from other studies, which evaluated patients undergoing gynecologic, laparoscopic, and outpatient procedures, where TDS was an effective agent, decreasing the incidence of PONV between 30% and 60%.Scopolamine has been used for many years as a bonafide antiemetic. It is a belladonna derivative, which acts as a postganglionic muscarinic receptor antagonist. It works as an antiemetic by blocking the cholinergic transmission from the vestibular nucleus, reticular formation and chemoreceptor trigger zone. Its activity for PONV is dose dependant. Historically, scopolamine was used as an oral or parenteral medication. Several studies advocated a subcutaneous route of administration to reduce its side effects, but even so, scopolamine lost favor in obstetric anesthesia because of its side effects of blurred vision, sedation, and memory loss. These side effects were amplified when women who had recently given birth would say, ''I can't focus on my baby's face.'' By altering the pharmacokinetics of scopolamine, it is now possible to deliver it in lower doses via the transdermal route. This lower dose decrease...