Cynthia A. Wong

A randomized comparison of programmed intermittent epidural bolus with continuous epidural infusion for labor analgesia.

Bolus injection through an epidural catheter may result in better distribution of anesthetic solution in the epidural space compared with continuous infusion of the same anesthetic solution. In this randomized, double-blind study we compared total bupivacaine consumption, need for supplemental epidural analgesia, quality of analgesia, and patient satisfaction in women who received programmed intermittent epidural boluses (PIEB) compared with continuous epidural infusion (CEI) for maintenance of labor analgesia. The primary outcome variable was bupivacaine consumption per hour of analgesia. Combined spinal epidural analgesia was initiated in multiparas scheduled for induction of labor with cervical dilation between 2 and 5 cm. Subjects were randomized to PIEB (6-mL bolus every 30 min beginning 45 min after the intrathecal injection) or CEI (12-mL/h infusion beginning 15 min the after the intrathecal injection). The epidural analgesia solution was bupivacaine 0.625 mg/mL and fentanyl 2 &mgr;g/mL. Breakthrough pain in both groups was treated initially with patient-controlled epidural analgesia (PCEA) followed by manual bolus rescue analgesia using bupivacaine 0.125%. The median total bupivacaine dose per hour of analgesia was less in the PIEB (n = 63) (10.5 mg/h; 95% confidence interval, 9.5–11.8 mg/h) compared with the CEI group (n = 63) (12.3 mg/h; 95% confidence interval, 10.5–14.0 mg/h) (P < 0.01), fewer manual rescue boluses were required (rate difference 22%, 95% confidence interval of difference 5% to 38%), and satisfaction scores were higher. Labor pain, PCEA requests, and delivered PCEA doses did not differ. PIEB combined with PCEA provided similar analgesia, but with a smaller bupivacaine dose and better patient satisfaction compared with CEI with PCEA for maintenance of epidural labor analgesia.

Incidence of postpartum lumbosacral spine and lower extremity nerve injuries.

OBJECTIVE Neurological injury associated with present day labor and delivery is thought to be unusual. The purpose of this study was to estimate the incidence, severity, and duration of postpartum lumbosacral spine and lower extremity nerve injury and identify factors related to nerve injury. METHODS All women who delivered a live born infant from July 1997 through June 1998 were asked about symptoms of lumbosacral spine and lower extremity nerve injury the day after delivery. Women with symptoms were examined by a physiatrist to confirm injury, and their cases were then followed by telephone until the symptoms resolved. Maternal variables (including prospective documentation of time spent pushing in various positions) and fetal variables that might be associated with risk of nerve injury were compared between women with injury and those without. RESULTS Six thousand fifty-seven women delivered live born infants; 6048 were interviewed and 56 had a confirmed new nerve injury, an incidence of 0.92%. Factors found by logistic regression analysis to be associated with nerve injury were nulliparity and prolonged second stage of labor. Women with nerve injury spent more time pushing in the semi-Fowler–lithotomy position than women without injury. The median duration of symptoms was 2 months. CONCLUSION The estimated incidence of postpartum nerve injury was greater than reported from previous studies and is associated with nulliparity and prolonged second stage of labor.

Gastric Emptying of Water in Term Pregnancy

Background Healthy nonpregnant patients may ingest clear liquids until 2 h before induction of anesthesia without adversely affecting gastric volume. The purpose of this study was to compare gastric emptying in term, nonlaboring pregnant women after ingestion of 50 ml water (control) with that after ingestion of 300 ml water. Methods Gastric emptying was assessed in healthy, nonobese, term pregnant volunteers using both serial gastric ultrasound examinations (n = 9) and acetaminophen absorption (n = 11) in a crossover study design. After an overnight fast, volunteers ingested 1.5 g acetaminophen and 50 or 300 ml water (assigned in random order) on two occasions separated by at least 2 days. Serial gastric antrum cross-sectional areas were determined using gastric ultrasound imaging, and the half-time to gastric emptying was calculated. Serial plasma acetaminophen concentrations were measured. Areas under the plasma acetaminophen concentration versus time curve, peak concentrations, and time to peak concentration for 50- and 300-ml ingestions were compared. Results Gastric emptying half-time was significantly shorter after ingestion of 300 ml water than after ingestion of 50 ml (24 ± 6 vs. 33 ± 8 min). There were no differences in acetaminophen areas under the curve at 60, 90, or 120 min, or in acetaminophen peak concentration. Time to peak concentration of acetaminophen was significantly shorter after ingestion of 300 ml water than after ingestion of 50 ml (25 ± 12 vs. 41 ± 19 min). Conclusions Gastric emptying in healthy, term, nonobese, nonlaboring pregnant women is not delayed after ingestion of 300 ml water compared with that after an overnight fast.

Efficacy of a prophylactic epidural blood patch in preventing post dural puncture headache in parturients after inadvertent dural puncture.

Background:Postdural puncture headache (PDPH) occurs in up to 80% of parturients who experience inadvertent dural puncture during epidural catheter placement. The authors performed a randomized double blind study to assess the effect of prophylactic epidural blood patch on the incidence of PDPH and the need for therapeutic epidural blood patch. Methods:Sixty-four parturients who incurred inadvertent dural puncture were randomized to receive a prophylactic epidural blood patch with 20 ml autologous blood (prophylactic epidural blood patch group) or a sham patch (sham group). Subjects were evaluated daily for development of PDPH for a minimum of 5 days after dural puncture. Those who developed a PDPH were followed daily for a minimum of 3 days after resolution of the headache. Subjects with moderate headaches who reported difficulties performing childcare activities and all those with severe headaches were advised to receive a therapeutic epidural blood patch. Results:Eighteen of 32 subjects in each group (56%) developed PDPH. Therapeutic blood patch was recommended in similar numbers of patients in each group. The groups had similar onset time of PDPH, median peak pain scores, and number of days spent unable to perform childcare activities as a result of postural headache. The median duration of PDPH, however, was shorter in the prophylactic epidural blood patch group. Conclusions:A decrease in the incidence of PDPH or the need for criteria-directed therapeutic epidural patch was not detected when a prophylactic epidural blood patch was administered to parturients after inadvertent dural puncture. However, prophylactic epidural blood patch did shorten the duration of PDPH symptoms.

The accuracy of blood loss estimation after simulated vaginal delivery.

BACKGROUND:Visual blood loss estimation often underestimates blood loss. In this study we sought to determine the effect of calibrated drape markings on blood loss estimation in a simulated vaginal delivery. METHODS:Subjects were randomized to estimate simulated blood loss (300, 500, 1000, and 2000 mL) in calibrated or noncalibrated vaginal delivery drapes and then crossover. RESULTS:Visual blood loss estimation with noncalibrated drapes underestimated blood loss, with worsening accuracy at larger volumes (16% error at 300 mL to 41% at 2000 mL). The calibrated drape error was <15% at all volumes. CONCLUSIONS:Calibrated vaginal delivery drapes improve blood loss estimation.

Development of an Objective Scoring System for Measurement of Resident Performance on the Human Patient Simulator

Background:The decrease in the percentage of patients having cesarean delivery during general anesthesia has led some educators to advocate the increased use of simulation-based training for this anesthetic. The authors developed a scoring system to measure resident performance of this anesthetic on the human patient simulator and subjected the system to tests of validity and reliability. Methods:A modified Delphi technique was used to achieve a consensus among several experts regarding a standardized scoring system for evaluating resident performance of general anesthesia for emergency cesarean delivery on the human patient simulator. Eight third-year and eight first-year anesthesiology residents performed the scenario and were videotaped and scored by four attending obstetric anesthesiologists. Results:Third-year residents scored an average of 150.5 points, whereas first-year residents scored an average of 128 points (P = 0.004). The scoring instrument demonstrated high interrater reliability with an intraclass correlation coefficient of 0.97 (95% confidence interval, 0.94–0.99) compared with the average score. Conclusions:The developed scoring tool to measure resident performance of general anesthesia for emergency cesarean delivery on the patient simulator seems both valid and reliable in the context in which it was tested. This scoring system may prove useful for future studies such as those investigating the effect of simulator training on objective assessment of resident performance.

Early compared with late neuraxial analgesia in nulliparous labor induction: a randomized controlled trial.

OBJECTIVE: To determine whether early initiation of neuraxial analgesia (anesthetic[s] placed around the nerves of the central nervous system) compared with systemic opioid analgesia, followed later in labor by epidural analgesia, increases the rate of cesarean delivery in nulliparas undergoing induction of labor. METHODS: Nulliparas undergoing induction of labor who requested analgesia when cervical dilation was less than 4 cm participated in the study. Patients were randomized to neuraxial (early) or systemic opioid (late) analgesia at the first analgesia request. Patient-controlled epidural analgesia was initiated in the early group at the second analgesia request and in the late group at cervical dilation of 4 cm or greater or at the third analgesia request. The primary outcome was the rate of cesarean delivery. RESULTS: The rate of cesarean delivery was not different between groups (neuraxial [early] 32.7% compared with systemic [late] 31.5%, 95% confidence interval of the difference -3% to 6%, P=.65). A sample size of 30,500 would be required to detect a difference at the observed rate. There were no differences in the mode of vaginal delivery or Apgar scores. Pain scores were significantly lower (median 1 compared with 5 on a 0–10 scale, P<.001) and labor duration shorter (median 528 minutes compared with 569 minutes, P=.047) in the early group. The incidence of reassuring fetal heart rate tracings after analgesia was not different between groups. CONCLUSION: Early-labor neuraxial analgesia does not increase the cesarean delivery rate compared with late epidural analgesia in nulliparas undergoing induction of labor. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, www.clinicaltrials.gov, NCT00380978 LEVEL OF EVIDENCE: I

Labour analgesia and obstetric outcomes

Neuraxial analgesic techniques are the gold standards for pain relief during labour and delivery. Despite the increased use and known benefits of neuraxial labour analgesia, there has been significant controversy regarding the impact of neuraxial analgesia on labour outcomes. Review of the evidence suggests that effective neuraxial labour analgesia does not increase the rate of Caesarean delivery, even when administered early in the course of labour; however, its use is associated with a prolonged second stage of labour. Effective second-stage analgesia might also be associated with an increased rate of instrumental vaginal delivery.

The effect of manipulation of the programmed intermittent bolus time interval and injection volume on total drug use for labor epidural analgesia: A randomized controlled trial

BACKGROUND:Programmed intermittent bolus administration of epidural anesthetic solution compared with continuous infusion results in decreased anesthetic consumption and increased patient satisfaction. In this randomized and blinded study, we evaluated bupivacaine consumption and other analgesic outcomes when the programmed intermittent bolus time interval and volume were manipulated during the maintenance of epidural labor analgesia. METHODS:Healthy, term, nulliparous women in spontaneous labor had combined spinal-epidural labor analgesia initiated with intrathecal bupivacaine 1.25 mg and fentanyl 15 &mgr;g, followed by an epidural test dose (lidocaine 45 mg with epinephrine 15 &mgr;g). Subjects were randomized to 1 of 3 programmed intermittent bolus dose regimens for maintenance of analgesia: 2.5 mL every 15 minutes (2.5/15), 5 mL every 30 minutes (5/30), or 10 mL every 60 minutes (10/60). The maintenance epidural solution consisted of bupivacaine 0.625 mg/mL with fentanyl 1.95 &mgr;g/mL. Breakthrough pain was treated initially with patient-administered epidural bolus doses, followed by manual boluses administered by the anesthesiologist if necessary. The primary outcome was total bupivacaine consumption per hour of labor. A linear mixed-effects model was used to model each patients overall bupivacaine consumption per hour; the fixed effect was basal bupivacaine administration rate and the random effect was the area under the pain score versus time curve. RESULTS:One hundred ninety women were studied. The median (interquartile range) adjusted bupivacaine consumption per hour of labor was 8.8 mg (8.0–9.7 mg) in group 10/60 compared with 10.0 mg (9.3–10.8 mg) in group 5/30 and 10.4 mg (9.6–11.2 mg) in group 2.5/15 (P = 0.005). There were no differences in area under the pain score versus time curve, pain scores at delivery, patient-controlled epidural analgesia requests or administrations, number of manual bolus doses for breakthrough pain, time to first patient-controlled epidural analgesia or manual bolus dose, or patient satisfaction with labor analgesia. CONCLUSIONS:Extending the programmed intermittent bolus interval and volume from 15 minutes to 60 minutes, and 2.5 mL to 10 mL, respectively, decreased bupivacaine consumption without decreasing patient comfort or satisfaction.

The dose-response of intrathecal sufentanil added to bupivacaine for labor analgesia.

Background Regional analgesia for labor often is initiated with an intrathecal injection of a local anesthetic and opioid. The purpose of this prospective, randomized, blinded study was to determine the optimal dose of intrathecal sufentanil when combined with 2.5 mg bupivacaine for labor analgesia. Methods One hundred seventy parous parturients with cervical dilation between 3–5 cm were randomized to receive intrathecal 0 (control), 2.5, 5.0, 7.5, or 10.0 &mgr;g sufentanil combined with 2.5 mg bupivacaine, followed by a lidocaine epidural test dose, for initiation of analgesia (34 patients in each group). Visual analog scores and the presence of nausea, vomiting, and pruritus were determined every 15 min until the patient requested additional analgesia. Fetal heart rate tracings were compared between groups. Results Groups were similar for age, height, weight, oxytocin dose, duration of labor, and baseline visual analog scores. Duration of action was significantly shorter for control patients (39 ± 25 min [mean ± SD]) compared with those administered sufentanil, all doses (93 ± 32, 93 ± 47, 94 ± 33, 97 ± 39 min), but was not different among groups administered 2.5, 5.0, 7.5, or 10.0 &mgr;g sufentanil. More patients who received 10 &mgr;g sufentanil reported nausea and vomiting than did control patients. The severity of pruritus increased with administration of 7.5 and 10.0 &mgr;g sufentanil. There was no difference in fetal heart rate changes among groups. Conclusions Intrathecal bupivacaine (2.5 mg) without sufentanil did not provide satisfactory analgesia for parous patients. However, bupivacaine combined with 2.5 &mgr;g sufentanil provided analgesia comparable to higher doses, with a lower incidence of nausea and vomiting and less severe pruritus.