Ropivacaine 7.5 mg/ml for elective caesarean section. A clinical and pharmacokinetic comparison of 150 mg and 187.5 mg.
BACKGROUND
The new, long-acting local anaesthetic ropivacaine has shown less systemic toxicity than bupivacaine and a concentration of 7.5 mg/ml can therefore be used for epidural anaesthesia in Caesarean section. The present pilot study was undertaken to find indications for an optimal dosage by comparing the clinical effects, quality of anaesthesia and pharmacokinetics of ropivacaine 150 mg (lower dose = LD) vs 187.5 mg (higher dose = HD) for women undergoing elective Caesarean section under epidural anaesthesia.


METHODS
Sixteen full-term women scheduled for elective Caesarean section in two equal-sized consecutive groups received 20 or 25 ml ropivacaine epidurally in this non-randomised, open study. Study parameters included sensory and motor blockade, circulatory response, intraoperative pain and discomfort, neonatal evaluation and pharmacokinetic determinations.


RESULTS
Block height varied between T5 and T2 in the LD group, whereas the HD group produced 4 unnecessarily high blocks (C8 in 3 women and C7 in 1 woman). Surgical anaesthesia was excellent in both groups. Circulatory stability was pronounced in the LD group (no ephedrine given), while 4 women required ephedrine in the HD group. Neonatal outcome as judged by Apgar scores; umbilical blood gas determinations and NACS scores were excellent in both groups. The plasma concentration-time profiles indicated linearity in the concentration range studied, with similar clearance values to those reported previously. Placental drug equilibrium was rapid; however, the foetal drug exposure depended on intrauterine exposure time.


CONCLUSIONS
20-25 ml ropivacaine 7.5 mg/ml produced very satisfactory conditions for elective Caesarean section under epidural anaesthesia. In this small population, 150 mg ropivacaine seemed optimal, while 187.5 mg produced unnecessarily extended block height in 50% of the women.
Irestedt
L
L
Department of Anaesthesia and Intensive Care, Karolinska Hospital, Stockholm, Sweden.
Emanuelsson
B M
BM
Ekblom
A
A
Olofsson
C
C
Reventlid
H
H
D000328:Adult; D000577:Amides / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology; D000767:Anesthesia, Epidural; D000773:Anesthesia, Obstetrical; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D002585:Cesarean Section / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011597:Psychomotor Performance / Q000187:drug effects*; D000077212:Ropivacaine
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine