Influence of mu-opioid receptor variant on morphine use and self-rated pain following abdominal hysterectomy.

UNLABELLED: A common variant in the mu-opioid receptor gene (OPRM1) has been associated with response to opioid analgesia. Our previous data revealed significantly higher amounts of morphine self-administered by patients carrying the 118G allele compared to those with the 118A allele after elective cesarean section. In this study, the association of this genetic variation with pressure pain, postoperative pain scores, and amount of morphine used was investigated in 973 patients undergoing scheduled total hysterectomy under general anesthesia. Preoperative pressure pain threshold and tolerance were also measured for most patients. For pressure pain, OPRM1 genotype was not significantly associated with either pain threshold or pain tolerance. Statistically significant associations were found for postoperative pain and the total amount of morphine used, with the GG group reporting higher pain scores and using the most morphine. When analysis was stratified by ethnic group, differences in weight-adjusted morphine for the 3 genotypic groups were also significant for the Chinese and Asian Indians. These results extend our previous finding on the association of higher self-reported pain and morphine use for acute postoperative pain with OPRM1 118G to patients who had total hysterectomy under general anesthesia. PERSPECTIVE: In a large cohort of patients undergoing hysterectomy, we found large variability in the self-rated pain scores and the amount of morphine required for pain relief. Both are associated with OPRM1 genotypes and preoperative experimental pressure pain threshold. Experimental pressure pain tolerance is also associated with postoperative pain.

A randomised trial of the analgesic efficacy of ultrasound-guided transversus abdominis plane block after caesarean delivery under general anaesthesia.

CONTEXT: Previous studies examining the efficacy of transversus abdominis plane block after caesarean section have mostly been in parturients under spinal anaesthesia. OBJECTIVES: We postulated that the advantage of performing transversus abdominis plane block after caesarean section might be even more obvious after general anaesthesia, resulting in reduced 24-h consumption of morphine. DESIGN, SETTING, PATIENTS AND INTERVENTIONS: In this single centre, randomised double-blind controlled trial, 40 women who underwent caesarean delivery under general anaesthesia were allocated randomly to receive a transversus abdominis plane block or no block. In those who received the block, 20 ml of levobupivacaine 2.5 mg ml was deposited bilaterally into the transversus abdominis plane under ultrasound guidance using a Sonosite Titan (SonoSite, Bothell, Washington, USA) 7-13 MHz linear transducer at the end of surgery when the patient was still anaesthetised. MAIN OUTCOME MEASURES: We recorded patient-controlled intravenous morphine use for 24 h, pain scores at rest and activity, sedation, nausea and vomiting, use of antiemetic medication and overall maternal satisfaction. The primary outcome was 24-h morphine consumption. RESULTS: Patients who received the transversus abdominis plane block used significantly less morphine in 24 h than those in the control group [12.3 (2.6) vs. 31.4 mg (3.1), P<0.001) and had higher satisfaction scores [16 (80%) vs. 5 (25%), P = 0.012). There were no differences between groups in the visual analogue pain scores, sedation level, nausea and vomiting or the use of antiemetic medication. CONCLUSION: Ultrasound-guided transversus abdominis plane block reduced morphine consumption following caesarean section under general anaesthesia, with increased maternal satisfaction.

A randomized controlled trial of three patient-controlled epidural analgesia regimens for labor.

BACKGROUND: Patient-controlled epidural analgesia (PCEA) is a safe and effective mode of maintaining labor analgesia; however, the ideal PCEA regimen is controversial. METHODS: In this prospective, randomized, double-blind study, we examined the analgesic efficacy of demand-only PCEA and PCEA with background infusion. We recruited 300 nulliparous parturients. Analgesia was initiated with intrathecal ropivacaine 2 mg and fentanyl 15 microg and maintained with epidural ropivacaine 0.1% with fentanyl 2 microg/mL. Parturients were randomized to one of three groups. Group 0: demand-only PCEA, bolus of 5 mL, lockout interval of 15 min. Group 5: background infusion of 5 mL/h, bolus of 5 mL, lockout interval of 12 min. Group 10: background infusion of 10 mL/h, bolus of 5 mL, lockout interval of 10 min. The maximum dose of all groups was 20 mL/h. The primary outcome was incidence of breakthrough pain. Secondary outcomes included intrapartum pain scores, neuraxial blockade characteristics, side effects, the total and hourly volume of ropivacaine, neonatal outcomes, and obstetric outcomes. RESULTS: The incidence of breakthrough pain and the maximum visual analog scale (0-100 mm scale) pain scores were higher in Group 0 versus Groups 5 and 10 (43% vs 17% and 11%, P < 0.001 and 37 +/- 28 vs 22 +/- 26 and 16 +/- 25 [mean +/- SD], P < 0.001), respectively. Group 10 had a longer duration of effective analgesia compared with Group 0 (mean 895 min, 95% CI 823-966 vs 565 min, 95% CI 454-677, P < 0.001) and increased ropivacaine consumption, and was associated with a longer duration of the second stage of labor. CONCLUSION: Demand-only PCEA (5-mL bolus, 15-min lockout interval) resulted in less local anesthetic consumption but an increased incidence of breakthrough pain, higher pain scores, shorter duration of effective analgesia, and lower maternal satisfaction, when compared with PCEA with background infusion (5-mL bolus, 10-12-min lockout interval, and 5-10 mL/h infusion).

Combined spinal epidural causes higher level of block than equivalent single-shot spinal anesthesia in elective cesarean patients.

Combined spinal epidural (CSE) is an established technique for lower segment cesarean delivery. In this study we tested the hypothesis that the spinal block from a CSE technique results in a more extensive spread of local anesthetic in the subarachnoid space than the single-shot spinal (SSS) technique. We recruited 30 ASA physical status I parturients admitted for elective lower segment cesarean delivery into our randomized, controlled, double-blind study. All patients intrathecally received 2 mL of 0.5% hyperbaric bupivacaine. The patients were randomized into one of the two groups using sealed opaque envelopes. Group S (n = 15) received a SSS technique. Group CS (n = 15) received a CSE technique using loss of resistance to 2 mL of air, but the epidural catheter was not inserted after the intrathecal drug administration. The maximal sensory block achieved in group CS was statistically higher than that in Group S (median C6 interquartile range, C5 to C8 versus median T3, T2 to T4, P < 0.001). Time taken to reach maximal sensory block was significantly longer in group CS. There were no differences in the time taken for the block to recede to T10, hemodynamic profile, or side effects. In conclusion, the CSE technique without placing an epidural catheter or administering epidural medication resulted in a significantly higher level of sensory block when compared with the SSS technique when the same dose of local anesthetic was given intrathecally.

A comparison of median effective doses of intrathecal levobupivacaine and ropivacaine for labor analgesia.

BACKGROUND: The study was designed to determine and compare the median effective doses (MEDs) of intrathecal ropivacaine with levobupivacaine for labor analgesia. METHODS: In this double-blind study, 100 parturients in early labor were randomized to receive either intrathecal ropivacaine or levobupivacaine. For each drug, the patients were assigned to receive one of the five doses studied, namely 1, 1.5, 2, 2.5, or 3 mg. Effective analgesia was defined as a pain score (0-100 visual analog scale) of less than 10 within 15 min of injection, lasting for 45 min or more after the induction of analgesia. MEDs were derived from probit analysis. The duration of analgesia rendered by the two drugs at 2.5 and 3 mg was also compared. RESULTS: The MED for levobupivacaine was 1.07 mg (95% confidence interval, 0.88-1.25 mg), and the MED for ropivacaine was 1.40 mg (95% confidence interval, 1.20-1.61 mg). Levobupivacaine was found to be 1.31 (95% confidence interval, 1.04-2.01) times more potent than ropivacaine. At doses of 2.5 mg or greater, there was no significant difference in duration of analgesia between levobupivacaine (median, 63.5 min; range, 46-123 min) and ropivacaine (median, 59.0 min; range, 47-93 min; P = 0.18). We detected no difference in the incidence of hypotension, nausea and vomiting, motor block, or abnormal fetal heart tracing between the two drugs. CONCLUSIONS: The MED of intrathecal ropivacaine for labor analgesia was significantly greater than levobupivacaine experimentally, but this significance was reduced when the comparison was based on molar potency. There was no difference in the duration of analgesia or adverse effects between the two drugs at higher doses (2.5 mg or greater).

0.2% Ropivacaine and levobupivacaine provide equally effective epidural labour analgesia.

PURPOSE: To compare the duration of epidural analgesia induced by levobupivacaine and ropivacaine at clinically relevant doses. METHODS: Forty healthy nulliparous parturients with cervical dilatation of 3 to 5 cm and at least one contraction every two or three minutes were recruited. Patients were randomly assigned to receive either 10 mL of 0.2% ropivacaine or 10 mL of 0.2% levobupivacaine. Preblock visual analogue scale (VAS) score (0-100) and VAS score after five, ten, 15, 20, 25 and 30 min from time(0) and VAS at time of request for additional analgesia (time(end)) were recorded. During the first 30 min after the completion of epidural injection, the systolic blood pressure, highest sensory level to cold and the maximum degree of motor block based on a 0 to 3 modified Bromage scale were collected every five minutes. The duration of analgesia was defined as the time from time(0) to time(end). RESULTS: There was no difference in the duration of analgesia between the two groups; similarly, there was no significant difference found in the area under the curve (AUC) time(15)-time(0) and AUC time(30)-time(0) for VAS. The highest sensory block to cold and the degree of motor block were also indistinguishable between the two groups. No difference in the serial systolic blood pressures was found. CONCLUSION: Ten millilitres of either 0.2% ropivacaine or levobupivacaine can be used to induce epidural labour analgesia effectively without a difference in the duration of pain relief.

Comparison of intrathecal levobupivacaine with and without fentanyl in combined spinal epidural for labor analgesia.

BACKGROUND: The initiation of epidural infusion immediately after intrathecal (IT) injection to prolong labor analgesia has gained increasing popularity. The effect of additional intrathecal fentanyl on levobupivacaine for labor analgesia has not been fully investigated. We wished to determine if addition of IT fentanyl to IT levobupivacaine in combined spinal epidural (CSE) could prolong obstetric analgesia when epidural infusion is initiated promptly. MATERIAL/METHODS: In this randomized controlled trial, 40 nulliparous parturients in labor were recruited to receive either IT 2.5 mg levobupivacaine (L) or IT 2.5 mg levobupivacaine + 25 microg fentanyl (LF). A 10 ml/h epidural infusion of 0.125% levobupivacaine and 2 microg/ml fentanyl was immediately started. The proportion of parturients who delivered without breakthrough pain and the duration of analgesia were analyzed with the x2 test and Kaplan-Meier technique (using a log-rank test), respectively. Sensory block, motor block, pain scores, and post-block side effects were also evaluated. RESULTS: The percentage of parturients with "successful" blocks, i.e. parturients not requiring further analgesic supplementation, was significantly higher in LF (87.5% vs. 44%, p<0.05). The duration of analgesia was also significantly longer in group LF (mean 530 min +/- SE65 vs. 361 +/- 66, p<0.05). CONCLUSIONS: The addition of 25 microg intrathecal fentanyl to 2.5 mg levobupivacaine as part of CSE for labor analgesia decreased the incidence of labor breakthrough pain and resulted in a longer duration of labor pain relief. This may decrease the need for supplemental labor pain relief and the anesthetists' workload in the delivery suite.

A comparison of duration of analgesia of intrathecal 2.5 mg of bupivacaine, ropivacaine, and levobupivacaine in combined spinal epidural analgesia for patients in labor.

UNLABELLED: We assessed the duration of labor analgesia rendered by intrathecal (IT) local anesthetics as the sole drugs. In this randomized, controlled, and double-blinded study, labor analgesia was induced using combined spinal-epidural technique in 60 ASA physical status I nulliparous parturients with IT bupivacaine 2.5 mg (group B), ropivacaine 2.5 mg (group R), or levobupivacaine 2.5 mg (group L). Pain scores (0-100 visual analog scale) and blood pressure were recorded pre-block and for the first 30 min post-block. The degree of motor block and the highest sensory block were also monitored. The duration of analgesia (our primary outcome) was the longest in group B but was similar between groups R and L (mean +/- SE, 76.3 +/- 5.9 min versus 52.6 +/- 4.0 min and 51.5 +/- 3.4 min, respectively, P < 0.05). Group B had the most frequent incidence of lower limb motor block but there was no difference between groups R and L (5 of 20 parturients versus 2 of 20 and 0 of 20, respectively, P < 0.05). The profile of the other side effects was indistinguishable between the groups. With the current regimen, IT bupivacaine produced the longest duration of labor analgesia. IMPLICATIONS: Intrathecal 2.5 mg bupivacaine significantly prolongs the duration of analgesia in laboring patients compared with ropivacaine or levobupivacaine. This suggests that, at clinically relevant doses, bupivacaine may have greater potency.