An intravenous fluid bolus is not necessary before administration of intrathecal fentanyl for labor analgesia

Abstract

Study objective: To determine if an intravenous (i.v.) fluid bolus is necessary to prevent any possible hemodynamic sequelae after administration of intrathecal fentanyl in laboring parturients.

Design: Prospective, randomized study.

Setting: Labor suite of a women's tertiary care hospital.

Patients: 30 ASA physical status I and II parturients in active labor requesting labor analgesia.

Interventions: Patients were randomly divided into two groups of 15. One group received no i.v. fluid prior to the administration of 25 micrograms of intrathecal fentanyl, and the other group received 500 ml of lactated Ringer's solution before the block.

Measurements and main results: Blood pressures [systolic (SBP), diastolic (DBP), mean (MAP)], heart rate (HR), cardiac index (CI; using impedance cardiography), and visual analog scores were measured before the block, after fluids, and then every 5 minutes for 45 minutes after the block. Prenatal baseline blood pressures before the onset of labor were obtained from the obstetrician's office records. Results were analyzed using analysis of variance. All patients reported good pain relief. No patient from either group required treatment for hypotension. In the no fluid group, SBP and MAP decreased 10% and 14%, respectively (p = 0.05), following intrathecal fentanyl administration compared with preblock values obtained during labor but not when compared with prelabor prenatal values. In the fluid group, no significant changes occurred in SBP after intrathecal fentanyl but MAP decreased approximately 12% only in comparison to preblock values. No significant changes were noted in CI in either group. Fluid infusion itself caused an increase in HR and CI of approximately 12% and 9.4%, respectively.

Conclusion: Intrathecal fentanyl produces only minimal hemodynamic changes with or without prior fluid administration.