Onset of action between bupivacaine 0.5% and bupivacaine 0.5% plus fentanyl 75 mcg

Epidural anesthesia with bupivacaine, bupivacaine and fentanyl, or bupivacaine and sufentanil during intravenous administration of propofol for ovariohysterectomy in dogs

OBJECTIVE

To compare cardiovascular and systemic effects and analgesia during the postoperative period of epidural anesthesia performed with bupivacaine alone or with fentanyl or sufentanil in bitches maintained at a light plane of anesthesia with continuous infusion of propofol.

STUDY DESIGN

Prospective randomized masked clinical trial.

ANIMALS

30 female dogs of various breeds.

PROCEDURES

Dogs were allocated into 3 groups of 10 each. One group received fentanyl (2 microg/kg [0.91 microg/lb]) and bupivacaine (1 mg/kg [0.45 mg/lb]), 1 group received sufentanil (1 microg/kg) and bupivacaine (1 mg/kg), and 1 group received bupivacaine (1 mg/kg). All dogs received acepromazine (0.1 mg/kg [0.045 mg/lb]) and continuous infusion of propofol for sedation. The agents were administered into the lumbosacral space and diluted in saline (0.9% NaCl) solution to a total volume of 0.36 mL/kg (0.164 mL/lb). Cardiac and respiratory rates, arterial blood pressures, pH, and blood gases were evaluated. Analgesia, sedation level, serum cortisol concentrations, and plasma catecholamine concentrations were measured regularly for 6 hours.

RESULTS

No important changes in cardiovascular, respiratory, or sedation variables were observed. Degree of analgesia in the postoperative period was higher in the sufentanil group, although use of fentanyl and bupivacaine also resulted in a sufficient level of analgesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of the 3 anesthetic techniques permitted ovariohysterectomy with sufficient analgesia and acceptable neuroendocrine modulation of pain with minimal adverse effects.

Neonatal effects of adding epidural fentanyl to 0.5% bupivacaine for caesarean section

Epidural injection of opioids has been introduced to improve analgesia during labour and caesarean section. This study was designed to quantify placental transfer of fentanyl and to evaluate neonatal effects of adding fentanyl to 0.5% bupivacaine for epidural anaesthesia in women undergoing elective caesarean section at term. The parturients were randomly allocated to one of four groups of 20, who received either saline (control) or 50, 75 or 100 microg of fentanyl added to 20 ml of 0.5% bupivacaine. Apgar scores, time to sustained respiration and umbilical acid-base values did not differ among the groups. The median (interquartile range) umbilical artery to maternal vein fentanyl concentration ratio was 0.34 (0.26-0.48) when the fentanyl groups were taken together. Neurologic and adaptive capacity scores were evaluated at 2 and 24 h. Neonates whose mothers received fentanyl had lower scores with regard to supporting reaction at 2 h and active tone at 24 h, when compared to controls (P<0.05), but there were no differences among the groups with regard to the other test criteria in the neurobehavioural test. In conclusion, epidural injection of fentanyl 50-100 microg did not produce depression of the term neonate.

Maternal effects of adding epidural fentanyl to 0.5% bupivacaine for caesarean section

Epidural injection of fentanyl added to 0.5% bupivacaine improves epidural anaesthesia during caesarean section. The present prospective randomized double-blind study sought to determine the lowest effective dose of fentanyl. Eighty healthy women at term were divided into four groups of 20, with each group receiving a different 2 ml study solution: saline (control) or 50, 75 or 100 microg of fentanyl added to 20 ml of 0.5% bupivacaine. Additional increments of 0.5% bupivacaine were administered as required at 30 min and onwards until a bilateral block to T4 was attained. The onset, duration and segmental level of analgesia, and degree and duration of motor block were not influenced by the addition of fentanyl. Peroperative quality of analgesia was improved, as the request for supplementary analgesics was less following the addition of 75 or 100 microg of fentanyl (P < 0.05). Postoperatively the time to first supplemental opioid request was prolonged and pain was reduced for at least 6 h from induction of anaesthesia when 75 or 100 microg of fentanyl had been added (P < 0.05). Pruritus was the only side-effect (P < 0.05). In conclusion, fentanyl 75 microg was the lowest effective dose for improving quality of analgesia. Onset time was not reduced by the addition of fentanyl.