Pharmacokinetics of bupivacaine after bilateral ultrasound-guided transversus abdominis plane block following cesarean delivery under spinal anesthesia.

BACKGROUND: Transversus abdominis plane block is an effective method of post-cesarean analgesia. There are no data available about plasma bupivacaine levels after this block in adults. This study aimed to assess bupivacaine pharmacokinetic parameters after ultrasound-guided transversus abdominis plane blocks following cesarean delivery under spinal anesthesia. METHODS: A prospective observational study in parturients undergoing elective cesarean delivery under hyperbaric bupivacaine spinal anesthesia was conducted. After surgery, patients received bilateral transversus abdominis plane block (50mg bupivacaine each side). Venous blood samples were collected immediately before performing the block and at 10, 20, 30, 45, 60, 90, 120, 180, 240, 720 and 1440minutes. High performance liquid chromatography was used to measure total plasma bupivacaine concentrations. Mean bupivacaine area under the curve (AUC) was calculated from 0 to 24hours. RESULTS: Data were collected from 17 parturients. Mean age and body mass index were 31±6y and 30±4kg/m2 respectively. Mean plasma bupivacaine concentration before the block was 171ng/mL. Mean peak concentration was 802.36ng/mL (range 231.8 to 3504.5ng/mL). Mean time to peak concentration was 30min and mean area-under-the-curve (0-24h) was 4505.4h.ng/mL. Mean elimination half-life was 8.75h. Three subjects had concentrations above the quoted toxic threshold and mild symptoms suggestive of neurotoxicity were reported by two subjects, but no treatment was required. CONCLUSION: Single-dose bilateral transversus abdominis plane block using 100mg of bupivacaine, after spinal anesthesia for cesarean delivery, can result in toxic plasma bupivacaine concentrations.

[Prevention of hypotension during spinal anesthesia for elective caesarean section: coloading with HAE 130/0.4 vs normal saline solution]. / Prévention de l'hypotension induite par la rachianesthésie au cours de la césarienne programmée : coremplissage par HEA 130/0,4 vs sérum salé isotonique.

OBJECTIVE: The aim of this study was to compare the efficacy of HES 130/0.4 coloading compared to normal saline solution for prevention of hypotension during spinal anesthesia for elective caesarean section. STUDY DESIGN: Prospective, randomized. PATIENTS AND METHODS: One hundred and twenty ASA I and II patients scheduled for elective caesarean section were recruited. Patients were randomized to receive either 500mL of HES 130/0.4 (Voluven(®)) coloading (GroupV) or 500mL of normal saline solution coloading (GroupC). Spinal anesthesia technique and ephedrine administration were standardized in both groups. The primary endpoint was the incidence of maternal hypotension during spinal anesthesia for elective caesarean section. RESULTS: Hypotension occurred in 43 patients in group C and 24 patients in group V (p=0.001). Ephedrine consumption was significantly lower in group V (P=0.005). Nausea, vomiting and headache incidence was higher in group C (p=0.006). Apgar scores and umbilical blood gazes were comparable between groups. CONCLUSION: HES 130/0.4 coload was more effective than normal saline solution to prevent hypotension following spinal anesthesia for elective cesarean section. HES 130/0.4 coload reduced the incidence, the duration of longest hypotension, the need for ephedrine and the adverse maternal effects.