ED50 of remifentanil for providing excellent intubating conditions when co-administered with a single standard dose of propofol without the use of muscle relaxants in children: dose-finding clinical trial.

PURPOSE: Previous studies evidenced that orotracheal intubation without neuromuscular blockers is feasible in children and has some potential advantages. Remifentanil has favorable pharmacodynamic and pharmacokinetic properties as an opioid for orotracheal intubation, but its dose for excellent intubation conditions when co-administered with propofol has not been established. This study was designed to find the minimum effective dose of remifentanil for excellent intubation conditions of children when co-administered with propofol, without neuromuscular relaxant drugs. METHOD: Blinded adaptive clinical trial, with sequential allocation of 27 children between 2 and 9 years-old, American Society of Anesthesiologists' physical status PI or PII, scheduled for elective surgery under general anesthesia. Remifentanil dose began at 2 µg/kg and varied by 0.25 µg/kg according to the sequential allocation up-and-down rule designed by Dixon and Massey. Remifentanil was infused in 30 s and followed by propofol (3 mg/kg) in 20 s. Laryngoscopy and intubation were performed and assessed using Viby-Mogensen criteria, 90 s after the end of opioid administration. Inclusion of patients stopped after six crossovers, and remifentanil effective dose was estimated using pooled adjacent-violators algorithm. RESULTS: Remifentanil effective dose for 50% was established in 3.04 µg/kg (IC 95% 2.68-3.11, p < 0.05). The most frequent adverse effect was difficult positive pressure facial mask ventilation, which occurred in four children (15%). CONCLUSION: Minimum remifentanil effective dose for providing excellent intubating conditions when co-administered with a single standard dose of propofol without the use of neuromuscular blockers in children is 3.04 µg/kg. TRIAL REGISTRATION: NCT02454868.

Ephedrine versus phenylephrine: prevention of hypotension during spinal block for cesarean section and effects on the fetus.

BACKGROUND AND OBJECTIVES: Hypotension during spinal block for cesarean section is secondary to the sympathetic blockade and aorto-caval compression by the uterus and it can be deleterious to both the fetus and the mother. Ephedrine and phenylephrine improve venous return after sympathetic blockade during the spinal block. The objective of this study was to compare the efficacy of ephedrine and phenylephrine in the prevention and treatment of maternal hypotension during spinal block and to evaluate their side effects and fetal changes. METHODS: Sixty patients undergoing spinal block with bupivacaine and sufentanil for cesarean section were randomly divided in two groups to receive prophylactic ephedrine (Group E, n = 30, dose = 10 mg) or phenylephrine (Group P, n = 30, dose = 80 microg). Hypotension (blood pressure equal or lower than 80% of baseline values) was treated with bolus administration of the vasoconstrictor at 50% of the initial dose. The incidence of hypotension, reactive hypertension, bradycardia, and vomiting, and Apgar scores on the 1st and 5th minutes, and blood gases of the umbilical cord blood were evaluated. RESULTS: The mean dose of ephedrine used was 14.8 +/- 3.8 mg and of phenylephrine was 186.7 +/- 52.9 microg. Demographic parameters and the incidence of vomiting, bradycardia, and reactive hypertension were similar in both groups. Hypotension had an incidence of 70% in Group E and 93% in Group P (p < 0.05). The mean arterial pH of the umbilical cord blood and the Apgar score in the 1st minute were lower in Group E (p < 0.05). Differences in the Apgar score in the 5th minute were not observed. CONCLUSIONS: Ephedrine was more effective than phenylephrine in the prevention of hypotension. Both drugs had similar incidence of side effects. Fetal repercussions were less frequent with phenylephrine and were transitory with the use of ephedrine.