BACKGROUND: Dosage influences distribution of a local anesthetic solution in cerebrospinal fluid. The dose of intrathecal local anesthetic was investigated, taking into account the patient's weight and height, to see whether this would stabilize the hemodynamics and provide adequate spinal anesthesia for Cesarean section.

METHODS: In this double-blind prospective study, 60 patients undergoing elective Caesarean delivery were randomized to receive either fentanyl 25µgram in hyperbaric 0.5% bupivacaine 2.5 ml (Group 1) or fentanyl 25µgram and 0.9% normal saline in a volume of hyperbaric 0.5% bupivacaine, taking into account the patient's weight and height (Group 2). The patient's hemodynamics, time to sugical incision, supplementary analgesia and conversion to general anesthesia, etc were recorded.

RESULTS: The incidence of hypotension and use of ephedrine were decreased, and the administration of fluid and the duration of motor blockade were significantly shorter in Group 2. The time to surgical incision was faster and the peak sensory level was higher in Group 1. Others effects were similar in both groups.

CONCLUSIONS: The dose of intrathecal local anesthetic, taking into account the patient's weight and height stabilized the hemodynamics and provided adequate spinal anesthesia for elective Cesarean section.