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Revista Brasileira de Anestesiologia
Print version ISSN 0034-7094
SOUZA, Vinícius Pereira de; AMARAL, José Luiz Gomes do; TARDELLI, Maria Ângela and YAMASHITA, Américo Massafuni. Effects of prophylactic continuous infusion of phenylephrine on reducing the mass of local anesthetic in patients undergoing spinal anesthesia for cesarean section. Rev. Bras. Anestesiol. [online]. 2011, vol.61, n.4, pp.416-424. ISSN 0034-7094. http://dx.doi.org/10.1590/S0034-70942011000400003.
BACKGROUND AND OBJECTIVE: Reducing the mass of local anesthetic minimizes the effects of hypotension after spinal anesthesia for cesarean section and the incidence of maternal adverse events preserving fetal well-being, but it may result in insufficient anesthesia. Hypotension associated with greater masses of subarachnoid anesthesia can be controlled by prophylactic continuous infusion of phenylephrine. The effects of prophylactic continuous infusion of phenylephrine on pressure control on maternal and fetus results in cesarean sections with different doses of hyperbaric bupivacaine in spinal anesthesia. METHODS: A non-randomized prospective study of 60 gravidas at term scheduled for elective cesarean sections was undertaken. Patients were allocated into two groups depending on hyperbaric bupivacaine dose administered for spinal anesthesia, 12 or 8 mg, along with 5 µg of sufentanil and 100 µg of morphine. Patients were hydrated with 10 mL.kg-1 of Ringer's lactate before the anesthesia. Shortly after, continuous infusion of 100 µg.min-1 of phenylephrine was initiated to maintain blood pressure at baseline levels. The following parameters were evaluated: level of anesthetic blockade, consumption of vasopressors, incidence of maternal events, and conditions of the newborn. RESULTS: Maternal data was similar in both groups regarding the level of anesthetic blockade, phenylephrine consumption along time, incidence of hypotension, hypertension, bradycardia, nausea, vomiting, dyspnea, pain, and tremors. Conceptual data showed similarities between both groups regarding blood gases and umbilical vein lactate levels. The pH of all newborns was > 7.2. CONCLUSIONS: On maintaining the blood pressure with prophylactic continuous infusion of phenylephrine the incidence of maternal adverse events and conditions of birth do not differ whether spinal anesthesia is performed with 12 mg or 8 mg of hyperbaric bupivacaine.
Keywords : Phenylephrine; Anesthesia [Obstetrical]; Cesarean Section; Hypotension; Bupivacaine.