Analgesia, Pruritus, and Ventilation Exhibit a Dose-Response Relationship in Parturients Receiving Intrathecal Fentanyl During Labor

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Abstract
Inically relevant doses are unclear. We performed this study to establish the dose-response relationship of intrathecal fentanyl for both analgesia and ventilatory depression. Ninety parturients in active early labor (<or=to5 cm dilation) received intrathecal fentanyl 5, 7.5, 10, 15, 20, or 25 [micro sign]g in a double-blinded, randomized fashion (n = 15 patients in each group). Parturients were monitored for degree of pain (measured using a 100-mm visual analog pain scale), blood pressure, arterial oxygen saturation (Sao2), respiratory rate, ETCO2, and fetal heart rate 0, 1, 5, 10, 15, 20, 25, and 30 min after the administration of intrathecal fentanyl. An absolute visual analog pain scale score or=to15 [micro sign]g, without concomitant changes in respiratory rate or Sao2, which suggests a decrease in tidal volume. Even in the absence of overt signs or symptoms of somnolence, intrathecal fentanyl at doses within the effective analgesic range induced a change in ventilation that may last longer than the 30-min period we studied. Implications: Intrathecal fentanyl induces rapid and satisfying dose-dependent analgesia in early labor; however, it also produces dose-related decreases in ventilation in the absence of overt somnolence. (Anesth Analg 1999;89:378-83)...