Yvonne Lim

A118G single nucleotide polymorphism of human μ-opioid receptor gene influences pain perception and patient-controlled intravenous morphine consumption after intrathecal morphine for postcesarean analgesia

Background:Previous studies have shown that genetic variability at position 118 of the human &mgr;-opioid receptor gene altered patients’ response to intravenous morphine. The purpose of this study was to investigate whether this polymorphism contributes to the variability in response to morphine for postcesarean analgesia. Methods:After investigators obtained informed consent, 588 healthy women received 0.1 mg intrathecal morphine for postcesarean analgesia. Their blood samples were genotyped for the A118G polymorphism—A118 homozygous (AA), heterozygous (AG), or homozygous for the G allele (GG). Pain scores, the severity of nausea and vomiting, the incidence of pruritus, and the total self-administered intravenous morphine were recorded for the first 24 postoperative hours. Results:Two hundred seventy women (46%) were AA, 234 (40%) were AG, and 82 (14%) were GG. The 24-h self-administered intravenous morphine consumption was lowest in the AA group (P = 0.001; mean, 5.9; 95% confidence interval, 5.1–6.8) versus the AG (8.0; 6.9–9.1) and GG groups (9.4; 7.3–11.5). Pain scores were lowest in the AA group and highest in the GG group, with a statistically significant difference detected between AA, AG, and GG (P = 0.049). Total morphine consumption was also influenced by patients’ age and paying status. AA group was associated with the highest incidence of nausea (26 of 272 [9.6%]; P = 0.02) versus the other two groups (13 of 234 [5.6%] and 1 of 82 [1.2%] for AG and GG, respectively). Conclusion:Genetic variation at position 118 of the &mgr;-opioid receptor is associated with interindividual differences in pain scores, self-administered intravenous morphine, and the incidence of nausea postoperatively.

Evaluation of ease of intubation with the GlideScope® or Macintosh laryngoscope by anaesthetists in simulated easy and difficult laryngoscopy

The GlideScope® is a new video laryngoscope developed for management of the difficult airway. We compared the GlideScope with the Macintosh laryngoscope in simulated easy and difficult laryngoscopy. Twenty anaesthetists were allowed three attempts to intubate in each of four laryngoscopy scenarios in a high fidelity simulator. In the simulated easy laryngoscopy scenarios, the anaesthetists took longer to intubate using the GlideScope than the Macintosh laryngoscope (mean (SD) 19.0 (9.7) s vs. 12.7 (5.9) s, respectively; p = 0.006). There was no difference in the number of successful intubations, ease of intubation or choice of intubating device. In the simulated difficult laryngoscopy scenarios, the anaesthetists took less time to intubate using the GlideScope (23.5 (12.7) s vs. 70.5 (101.2) s, respectively; p = 0.001). The slightly higher success rate with the GlideScope was not statistically significant (20/20 vs. 18/20, respectively; p = 0.5). However, the anaesthetists found it easier to intubate using the GlideScope (median (interquartile range [range]) 1 (1–2 [1–2]) vs. 2 (2–3 [1–3]), respectively; p < 0.0001).

Ethnicity and OPRM variant independently predict pain perception and patient-controlled analgesia usage for post-operative pain

BackgroundMorphine consumption can vary widely between individuals even for identical surgical procedures. As mu-opioid receptor (OPRM1) is known to modulate pain perception and mediate the analgesic effects of opioid compounds in the central nervous system, we examined the influence of two OPRM polymorphisms on acute post-operative pain and morphine usage in women undergoing elective caesarean delivery.ResultsData on self-reported pain scores and amount of total morphine use according to patient-controlled analgesia were collected from 994 women from the three main ethnic groups in Singapore. We found statistically significant association of the OPRM 118A>G with self-administered morphine during the first 24-hour postoperative period both in terms of total morphine (p = 1.7 × 10-5) and weight-adjusted morphine (p = 6.6 × 10-5). There was also significant association of this OPRM variant and time-averaged self-rated pain scores (p = 0.024). OPRM 118G homozygotes used more morphine and reported higher pain scores than 118A carriers. Other factors which influenced pain score and morphine usage include ethnicity, age and paying class.ConclusionOur results suggest that ethnicity and OPRM 118A>G genotype are independent and significant contributors to variation in pain perception and postoperative morphine use in patients undergoing cesarean delivery.

Ethnic differences in pain perception and patient-controlled analgesia usage for postoperative pain.

UNLABELLED There are reports suggesting that sensitivity to and tolerance of both clinical and experimental pain differ among ethnic groups. We examined self-rated pain score and morphine usage in 1034 women who underwent elective lower cesarian section (LSCS) for their deliveries. Data on pain scores and amount of total morphine use according to patient-controlled analgesia were collected every 4 hours. Overall, lowest pain scores were recorded 12 hours after surgery and highest at 24 hours. Morphine consumption was highest within the first 4 hours and lowest between 12 and 16 hours. There were statistically significant ethnic group differences in pain scores (P = 1.7 x 10(-7)) and morphine usage (P = 2.8 x 10(-15)) between ethnic groups, with Indians having the highest mean pain score and using the highest amount of morphine. The ethnic differences in pain score and morphine self-administration persisted after controlling for age, body mass index, and duration of operation. PERSPECTIVE Our findings of highly significant ethnic group difference in self-reported pain level and the amount of analgesia self-administered may have implications on optimal management of acute postoperative pain. Inadequate management of pain after cesarian deliveries might affect the emotional well-being and physical recovery of patients and affect mother-child bonding.

A comparison of a basal infusion with automated mandatory boluses in parturient-controlled epidural analgesia during labor.

BACKGROUND:The use of parturient-controlled epidural analgesia (PCEA) with a basal infusion is commonly used in laboring women. We compared a novel approach of providing basal intermittent boluses concurrently with PCEA: PCEA plus automated mandatory boluses (PCEA+AMB) versus PCEA plus basal continuous infusion (PCEA+BCI). We hypothesized that epidural local anesthetic consumption would be lower if basal intermittent boluses were used instead of a basal infusion. METHODS:We randomized 42 healthy parturients in early labor to receive 0.1% ropivacaine + fentanyl 2 &mgr;g/mL either via PCEA+BCI (n = 21,bolus 5 mL, lockout 10 min, basal infusion 5 mL/h) or via PCEA+AMB (n = 21, patient-activated bolus of 5 mL, lockout 10 min, basal automated boluses of 5 mL/h [omitted if a patient-activated bolus was successfully administered in the last 1 h]) after successful induction of combined spinal epidural analgesia. RESULTS:We found a reduction in the hourly consumption of ropivacaine with PCEA+AMB, i.e., the primary outcome measure (mean = 6.5 mL, sd = 3.4 in the PCEA+AMB group vs 7.5 mL, sd = 2.0 PCEA+BCI group, P = 0.011). A larger proportion of parturients in the PCEA+AMB group did not self-bolus (6/21 vs 1/21 in PCEA+BCI, P = 0.03). The time to the first self-bolus after combined spinal epidural was longer in the PCEA+AMB group (mean survival time 315 min vs 190 min in PCEA+BCI group, P = 0.04 by log rank test). There was no difference in pain scores or side effects. CONCLUSION:Our study showed that PCEA+AMB reduced analgesic consumption and could be useful as the mode of maintenance for epidural analgesia.

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 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.

Success of Tracheal Intubation with Intubating Laryngeal Mask Airways A Randomized Trial of the LMA Fastrach™ and LMA CTrach™

Background:The LMA CTrach™ system (The Laryngeal Mask Company, Singapore) is a development of the LMA Fastrach™ system (The Laryngeal Mask Company, Singapore), with integrated fiberoptic bundles and a detachable liquid crystal display viewer. This randomized study of 271 patients compared tracheal intubation with these two systems. Methods:In both groups, ventilation was optimized after insertion of the laryngeal mask conduit before proceeding further: intubation with the LMA Fastrach™, and optimizing the conduit placement and view and then intubation with the LMA CTrach™. The first-attempt and overall success rates of tracheal intubation, and the times required, were recorded. Results:Tracheal intubation was successful on the first attempt in 93.3% of patients with the LMA CTrach™ and 67.9% of patients with the LMA Fastrach™ (P < 0.001). The success rates within three attempts were 100% with the LMA CTrach™ and 96.4% with the LMA Fastrach™ (P = 0.06). The median (interquartile range) time for the complete tracheal intubation process was 116 (82–156) s with the LMA CTrach™ and 100 (74–121) s with the LMA Fastrach™ (P = 0.002). There was no correlation between the grade of conventional laryngoscopy and success of intubation with either system. Conclusions:The ability to view the glottis and optimize placement of the LMA CTrach™ under vision enabled a higher first-attempt success rate of tracheal intubation with the LMA CTrach™. However, more time is required with the LMA CTrach™, there are failed views in some patients, and its cost effectiveness remains unclear.

Failure of augmentation of labor epidural analgesia for intrapartum cesarean delivery: a retrospective review.

In this study, we aimed to identify the incidence and predictive factors associated with failed labor epidural augmentation for cesarean delivery. Data of parturients, who had received neuraxial labor analgesia and who subsequently required intrapartum cesarean delivery during an 18-mo period, were retrospectively studied. Predictors associated with failure of extension of epidural analgesia in the presence of adequate time for onset of epidural anesthesia were identified by univariate logistic regression. Of the 1025 parturients, 1.7% had failed epidural extension. Predictors of failed epidural anesthesia included initiation of labor analgesia with plain epidural technique (compared to combined spinal-epidural) (P = 0.001), ≥2 episodes of breakthrough pain during labor (P < 0.001) and prolonged duration of neuraxial labor analgesia (P = 0.02).

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 μg and maintained with epidural ropivacaine 0.1% with fentanyl 2 μg/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).