A randomized comparison of automated intermittent mandatory boluses with a basal infusion in combination with patient-controlled epidural analgesia for labor and delivery

BACKGROUND

Automated mandatory boluses (AMB), when used in place of a continuous basal infusion, have been shown to reduce overall local anesthetic consumption without compromising analgesic efficacy in patient-controlled epidural analgesia (PCEA). We hypothesized that our PCEA+AMB regimen could result in a reduction of breakthrough pain requiring epidural supplementation in comparison with PCEA with a basal infusion (PCEA+BI).

METHODS

We recruited sixty-two healthy ASA I nulliparous parturients in early labor. The parturients were randomized to receive 0.1% ropivacaine+fentanyl 2 μg/mL either via PCEA+BI (PCEA with basal continuous infusion of 5mL/h) or PCEA+AMB (PCEA with AMB of 5 mL every hour instead of a basal infusion) immediately following successful induction of combined spinal-epidural (CSE) analgesia. Block characteristics, incidence of breakthrough pain requiring epidural supplementation, side effects, obstetric outcomes, Apgar scores and overall maternal satisfaction with analgesia were noted.

RESULTS

The time-weighted hourly consumption of ropivacaine (PCEA and clinician supplementation for breakthrough pain) was significantly lower in the PCEA+AMB group (mean=7.6 mL, SD 3.2) compared to the PCEA+BI group (mean=9.3 mL, SD 2.5; P<0.001). The mean time to first PCEA self-bolus following CSE was significantly longer in the PCEA+AMB group compared to the PCEA+BI group (268 min vs. 104 min; P<0.001). Parturients in Group PCEA+AMB also gave higher satisfaction scores. The incidence of breakthrough pain was similar in both groups.

CONCLUSION

PCEA+AMB, when compared to PCEA+BI, confers greater patient satisfaction and a longer duration of effective analgesia after CSE despite reduced analgesic consumption.

Comparison of Automated Intermittent Low Volume Bolus with Continuous Infusion for Labour Epidural Analgesia

Delivery of local anaesthetics via automated intermittent bolus has been shown to improve epidural analgesia compared to delivery via continuous epidural infusion. However, the optimal bolus volume has not been investigated. This randomised, double-blind study compared the analgesic efficacy of automated intermittent bolus (volume 2.5 ml every 15 minutes) with that of a continuous epidural infusion (10 ml/hour) for the maintenance of labour epidural analgesia, to determine whether the advantages previously demonstrated for automated intermittent bolus over continuous epidural infusion are retained at this low bolus volume. With the approval of the Hospital Ethics Committee, we recruited 50 parturients who received combined spinal epidural analgesia with intrathecal ropivacaine 2 mg and fentanyl 15 μg. For epidural maintenance, participants were randomised to either the automated intermittent bolus group (2.5 ml automated intermittent epidural boluses of ropivacaine 0.1% plus fentanyl 2 μg/ml delivered over a two-minute period every 15 minutes) or the continuous epidural infusion group (continuous epidural infusion of ropivacaine 0.1% plus fentanyl 2 μg/ml at 10 ml/hour). The primary study outcome was the incidence of pain during labour that required management with supplemental epidural analgesia. There were no significant differences between the two regimens in terms of breakthrough pain (automated intermittent bolus 36% [9/25] vs continuous epidural infusion 32% [8/25], P=0.77). At the doses used in this study, maintenance of labour analgesia using automated intermittent bolus at a bolus volume of 2.5 ml every 15 minutes does not decrease the incidence of breakthrough pain or improve analgesic efficacy compared to continuous epidural infusion.

A randomised controlled trial of hyperbaric bupivacaine with opioids, injected as either a mixture or sequentially, for spinal anaesthesia for caesarean section

It is common practice to mix opioids with hyperbaric bupivacaine in a single syringe before intrathecal injection of the mixture. Mixing these drugs may alter the density of the hyperbaric solution, affecting the spread of local anaesthetic and opioid. Forty-eight women having elective caesarean section under spinal anaesthesia were recruited to this double-blind, randomised trial. Group M (n=24) received 2 ml of 0.5% hyperbaric bupivacaine plus morphine 100 microg plus fentanyl 15 microg, mixed in a syringe prior to administration. Group S (n=24) received 2 ml of 0.5% bupivacaine through one syringe, followed by morphine 100 microg plus fentanyl 15 microg through a separate syringe. All patients received patient-controlled intravenous morphine for 24 hours postoperatively. Block characteristics, postoperative pain scores and morphine use were noted. The patients in Group M had higher levels of sensory block to cold than those in Group S (median T2 vs. T3) (P = 0.003). Five patients in Group M and none in Group S had a block to cold > or = T1 (P = 0.02). There was no difference between groups in the incidence of hypotension, need for vasopressor or side-effects. Morphine consumption was significantly higher in group M (13.3 +/- 11.2 vs. 6.2 +/- 7.2 mg, P = 0.015). Mixing of fentanyl and morphine with hyperbaric bupivacaine results in a higher level of sensory block than sequential administration of bupivacaine then opioid and may be associated with higher postoperative opioid requirement.

Incidence and risk factors for chronic pain after caesarean section under spinal anaesthesia

This study investigated the incidence and risk factors associated with chronic pain after elective caesarean section under spinal anaesthesia in an Asian population. A prospective cohort study was conducted among subjects who underwent elective caesarean section under spinal anaesthesia, with morphine patient-controlled analgesia administered for 24 hours postoperatively. Perioperative, surgical and obstetric factors were investigated prospectively. Phone surveys were conducted to identify risk factors associated with chronic pain. A total of 857 subjects completed both the perioperative study and phone survey. The incidence of wound scar pain for three months after surgery was 9.2% (79). Of the 51 subjects with persistent pain at the time of subsequent survey, 9.8% (n = 5) had constant pain, 9.8% (n = 5) had daily pain and 23.5% (n = 12) had pain intermittently, at an interval of days. The independent risk factors for development of chronic pain were higher pain scores recalled in the immediate postoperative period (odds ratio [OR, 95% confidence interval] 1.348 [1.219 to 1.490], P = 0.0001), pain present elsewhere (OR 2.471 [1.485 to 4.112], P = 0.001) and non-private insurance status (OR 1.679 [1.034 to 2.727], P = 0.036). The two most common sites of pain other than wound pain were back pain (n = 316) and migraine (n = 87).

Baseflow contribution to nitrates in an urban stream in Daejeon, Korea

It is a well-known fact that baseflow discharge of rainfall runoff significantly impacts the quality of surface water. In this paper, the impact of nitrates discharged as baseflow on stream water quality were studied using PULSE, a hydrograph separation software developed by USGS, to calculate the monthly baseflow discharge. We took water quality and flow rate data from a monitoring station site (code: Ghapcehon2) in Daejeon city and acquired 2005 groundwater quality data in the watershed from government agencies. Agricultural and forestry land use are dominant in the area. The baseflow contributes 85%-95% of stream flows during the spring and fall, 25%-38% during the summer and winter. The monthly nitrate loading discharged as baseflow for Ghapcheon2 was estimated by using monitored nitrate concentrations of groundwater in the watershed. Nitrate loading induced by baseflow at Ghapcheon2 was estimated as 5.4 tons of NO3(-)-N/km(2), which is about 60% of nitrate loading of surface water, or 9.2 tons of NO3(-)-N/km(2). This study shows that groundwater quality monitoring is important for proper management of surface water quality.

Comparison of the Single-use LMA Supreme with the Reusable ProSeal LMA for Anaesthesia in Gynaecological Laparoscopic Surgery

The Laryngeal Mask Airway Supreme (LMAS) is a new, single-use laryngeal mask airway with gastric access. We conducted a randomised controlled study comparing the LMAS with the reusable ProSeal Laryngeal Mask Airway (PLMA) in 70 patients undergoing general anaesthesia with paralysis for gynaecological laparoscopic surgery. Our primary outcome measure was the oropharynegal leak pressure. We also compared the two devices for ease of insertion, adequacy of ventilation and incidence of complications. Both devices had similar rates of successful insertion at the first attempt (LMAS 94% vs PLMA 91%). There was no difference in the time to establish an effective airway (LMAS 25±22 vs PLMA 24±9 seconds), although gastric tube insertion was faster for the LMAS (5±1 vs 7±3 seconds, P <0.001). The mean oropharyngeal leak pressure in the LMAS was significantly lower than in the PLMA (27.9±4.7 vs 31.7±6.3 cmH2O, P=0.007). This was consistent with a lower maximum tidal volume achieved with the LMAS (481±76 vs 515±63 ml, P=0.044). We found that after 60 minutes the cuff pressure was significantly higher in the PLMA (110±21 vs 57±8 cmH2O, P <0.001). There was no difference in the ability to provide adequate ventilation and oxygenation during anaesthesia. Complication rates were similar. We conclude that the oropharyngeal leak pressure and the maximum achievable tidal volume are lower with the LMAS than with the PLMA.