Gastric emptying during lumbar extradural analgesia in labour: effect of fentanyl supplementation

Gastric Emptying Velocity After Labor Analgesia Assessed by Sonography: A Prospective Controlled Observational Study

Objective

The effect of labor analgesia on gastric emptying rate will affect the management of fasting during the perinatal period. To evaluate gastric emptying after labor analgesia using the gastric antrum ultrasound examination.

Methods

From September 2022 to January 2023, a prospective controlled observational study was conducted. The Study group (epidural analgesia group) and Observation group (pharmacological and non-pharmacological interventions group) were successively enrolled and grouped using the random envelope method. However, labor analgesia was supplied according to maternal women's wishes, and intention-to-treat (ITT) and per-protocol (PP) analyses were performed to establish its effect on stomach emptying. The gastric emptying rate during the first stage of labor was considered to be the primary outcome.

Results

From September 2022 to January 2023, 120 persons were studied, 90 in the Study group and 30 in the Observation group. 33 people's analgesic selection was discordant with the grouped one. ITT analysis showed that the Study group's cross-sectional area (CSA) fell from baseline (624.19 ± 92.70 mm²) to 334.64 ± 46.32 mm² after 1 hour and to 217.26 ± 29.90 mm² after 2 hours. In the Observation group, the CSA similarly dropped from 620.10 ± 100.73 mm² to 331.30 ± 51.19 mm² and 214.70 ± 28.73 mm², p<0.001. CSA was not significantly different between groups, p>0.05. The PP analysis also indicated no significant changes in the CSA between the two groups at 3 time-points, p>0.05. At the first hour, the Study and Observation group had stomach emptying speeds of 300.05 ± 103.74 mm²/h and 259.50 ± 125.25 mm²/h, respectively, which were greater than those at the second hour (115.75 ± 43.51 mm²/h vs 124.36 ± 58.98 mm²/h), p<0.001.

Conclusion

Epidural analgesia, pharmacological, and non-pharmacological labor analgesia had little effect on gastric emptying, and gastric antrum ultrasonography can be utilized to monitor maternal gastric volume changes.

Pregnancy and Labor Epidural Effects on Gastric Emptying: A Prospective Comparative Study

BACKGROUND

The lack of reliable data on gastric emptying of solid food during labor has led to some discrepancies between current guidelines regarding fasting for solid food in the parturient. This prospective comparative study aimed to test the hypothesis that the gastric emptying rate of a light meal would be reduced in parturients receiving epidural analgesia and with no labor analgesia compared with nonpregnant and pregnant women.

METHODS

Ten subjects were enrolled and tested in each group: nonpregnant women, term pregnant women, parturients with no labor analgesia, and parturients with epidural labor analgesia. After a first ultrasound examination was performed to ensure an empty stomach, each subject ingested a light meal (125 g yogurt; 120 kcal) within 5 min. Then ultrasound measurements of the antral area were performed at 15, 60, 90, and 120 min. The rate of gastric emptying at 90 min was calculated as [(antral area90 min / antral area15 min) - 1] × 100, and half-time to gastric emptying was also determined. For the Parturient-Epidural group, the test meal was ingested within the first hour after the induction of epidural analgesia.

RESULTS

The median (interquartile range) rate of gastric emptying at 90 min was 52% (46 to 61), 45% (31 to 56), 7% (5 to 10), and 31% (17 to 39) for nonpregnant women, pregnant women, parturients without labor analgesia, and parturients with labor epidural analgesia, respectively (P < 0.0001). The rate of gastric emptying at 90 min was statistically significant and lower in the Parturient-Epidural group than in the Nonpregnant and Pregnant Control groups. In addition, the rate of gastric emptying at 90 min was statistically significant and lower in the Parturient-No-Epidural group than in the Parturient-Epidural group.

CONCLUSIONS

Gastric emptying in parturients after a light meal was delayed, and labor epidural analgesia seems not to worsen but facilitates gastric emptying. This should be taken into consideration when allowing women in labor to consume a light meal.

EDITOR’S PERSPECTIVE

The effect of high-dose versus low-dose epidural fentanyl on gastric emptying in nonfasted parturients: A double-blinded randomised controlled trial

BACKGROUND

Epidural fentanyl doses above 100 μg have been shown, using the paracetamol absorption test, to reduce gastric emptying in fasted labouring women.

OBJECTIVE

To investigate the effect of fentanyl dose on gastric emptying in nonfasted labouring women using gastric ultrasonography.

DESIGN

A double-blinded randomised controlled study.

SETTING

A tertiary medical centre in Tel Aviv, Israel between 30 July 2020 and 11 October 2020.

PATIENTS

Eighty labouring women with cervical dilation 5 cm or less, at least 18 years age, at least 37 weeks gestation with a singleton pregnancy and cephalad foetus.

INTERVENTIONS

Women randomised to high (>100 μg) or low (<100 μg) cumulative epidural fentanyl had ultrasound gastric content assessment, measuring antral cross-sectional area (CSA) at epidural placement and 2 h thereafter (T2  h).

MAIN OUTCOME MEASURES

The primary outcome was CSA at T2  h comparing high-dose versus low-dose fentanyl. Secondary outcomes included change in CSA between baseline and T2  h. Sub-group analysis compared stomach content at T2  h according to baseline stomach content, empty (CSA <381 mm2) or full (CSA ≥381 mm2), and high-dose versus low-dose fentanyl.

RESULTS

Data from 80 women were analysed; 63 had empty and 17 had full stomach at baseline. There was no significant difference in CSA at T2  h between high-dose, mean 335 ± SD 133 mm2, versus low-dose fentanyl, mean 335 ± SD 172 mm2, P = 0.991. Change in CSA baseline to T2  h was 46 ± SD 149 mm2 for high and 49 ± SD 163 mm2 for low-dose group, P = 0.931. The subgroup analysis according to baseline stomach content showed no statistically significant differences in CSA at T2  h.

CONCLUSION

The CSA at T2  h was similar for women who received high-dose versus low-dose epidural fentanyl, measured by ultrasound, in our nonfasted labouring cohort.

TRIAL REGISTRATION

Clinicaltrials.gov number: NCT04202887.

Prevalence and prediction of higher estimated gastric content in parturients at full cervical dilatation: A prospective cohort study

BACKGROUND

Emergent obstetrical procedures may require general anaesthesia in parturients at full cervical dilatation or immediately after vaginal birth. This study aimed to determine the prevalence and the predictive factors of higher estimated gastric content in parturients at full cervical dilatation with epidural analgesia and allowed to drink during the labour, and to assess the ability of the antral area measured in the semirecumbent position (SR-CSA) to identify higher estimated gastric content in this setting.

METHODS

This prospective observational study was conducted between December 2016 and July 2017. Ultrasonographic examination of the antrum was performed at full cervical dilatation, within the hour preceding the beginning of expulsive efforts. Higher estimated gastric content was defined when solid content was observed and/or if the calculated gastric fluid volume was >1.5 mL/kg.

RESULTS

Seventeen of 62 parturients (27%) presented higher estimated gastric content. Maximal pain intensity during the last hour of labour and time interval between the insertion of the epidural catheter and ultrasonographic examination were significantly increased in parturients with higher estimated gastric content. The threshold value of the SR-CSA to identify a higher estimated gastric content was 393 mm² , with sensitivity = 88% and specificity = 87%.

CONCLUSION

Around a quarter of parturients with epidural analgesia and free access to clear fluids during labour presented higher estimated gastric content at full cervical dilatation. The SR-CSA may be of interest for the fast ultrasound assessment of the gastric content status in case of emergent obstetrical procedures at full cervical dilatation.

Postpartum tubal ligation: A retrospective review of anesthetic management at a single institution and a practice survey of academic institutions

STUDY OBJECTIVE

The primary aim was to evaluate institutional anesthetic techniques utilized for postpartum tubal ligation (PPTL). Secondarily, academic institutions were surveyed on their clinical practice for PPTL.

DESIGN

An institutional-specific retrospective review of patients with ICD-9 procedure codes for PPTL over a 2-year period was conducted. Obstetric anesthesia fellowship directors were surveyed on anesthetic management of PPTL.

SETTING

Labor and delivery unit. Internet survey.

PATIENTS

202 PPTL procedures were reviewed. 47 institutions were surveyed; 26 responses were received.

MEASUREMENTS

Timing of PPTL, anesthetic management, postoperative pain and length of stay.

MAIN RESULTS

There was an epidural catheter reactivation failure rate of 26% (18/69 epidural catheter reactivation attempts). Time from epidural catheter insertion to PPTL was a significant factor associated with failure: median [IQR; range] time for successful versus failed epidural catheter reactivation was 17h [10-25; 3-55] and 28h [14-33; 5-42], respectively (P=0.028). Epidural catheter reactivation failure led to significantly longer times to provide surgical anesthesia than successful epidural catheter reactivation or primary spinal technique: median [IQR] 41min [33-54] versus 15min [12-21] and 19min [15-24], respectively (P<0.0001). Fifty-eight percent (15/26) of respondents routinely leave the labor epidural catheter in-situ if PPTL is planned. Sixty-five percent (17/26) and 7% (2/26) would not attempt to reactivate the epidural catheter for PPTL if >8h and >24h post-delivery, respectively.

CONCLUSIONS

Epidural catheter reactivation failure increases with longer intervals between catheter placement and PPTL. Failed epidural catheter reactivation increases anesthetic and operating room times. Our results and the significant variability in practice from our survey suggest recommendations on the timing and anesthetic management are needed to reduce unfulfilled PPTL procedures.

Epidural local anaesthetics versus opioid-based analgesic regimens for postoperative gastrointestinal paralysis, vomiting and pain after abdominal surgery

BACKGROUND

Gastrointestinal paralysis, nausea and vomiting and pain are major clinical problems following abdominal surgery. Anaesthetic and analgesic techniques that reduce pain and postoperative nausea and vomiting (PONV), while preventing or reducing postoperative ileus, may reduce postoperative morbidity, duration of hospitalization and hospital costs. This review was first published in 2001 and was updated by new review authors in 2016.

OBJECTIVES

To compare effects of postoperative epidural analgesia with local anaesthetics versus postoperative systemic or epidural opioids in terms of return of gastrointestinal transit, postoperative pain control, postoperative vomiting, incidence of anastomotic leak, length of hospital stay and costs after abdominal surgery.

SEARCH METHODS

We identified trials by conducting computerized searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 12), MEDLINE (from 1950 to December 2014) and EMBASE (from 1974 to December 2014) and by checking the reference lists of trials retained. When we reran the search in February 2016, we added 16 potential new studies of interest to the list of 'Studies awaiting classification' and will incorporate these studies into formal review findings during the next review update.

SELECTION CRITERIA

We included parallel randomized controlled trials comparing effects of postoperative epidural local anaesthetic versus regimens based on systemic or epidural opioids.

DATA COLLECTION AND ANALYSIS

We rated the quality of studies by using the Cochrane 'Risk of bias' tool. Two review authors independently extracted data and judged the quality of evidence according to the GRADE (Grades of Recommendation, Assessment, Development and Evaluation Working Group) scale.

MAIN RESULTS

We included 128 trials with 8754 participants in the review, and 94 trials with 5846 participants in the analysis. Trials included in the review were funded as follows: charity (n = 19), departmental resources (n = 8), governmental sources (n = 15) and industry (in part or in total) (n = 15). The source of funding was not specified for the other studies.Results of 22 trials including 1138 participants show that an epidural containing a local anaesthetic will decrease the time required for return of gastrointestinal transit as measured by time to first flatus after an abdominal surgery (standardized mean difference (SMD) -1.28, 95% confidence interval (CI) -1.71 to -0.86; high quality of evidence; equivalent to 17.5 hours). The effect is proportionate to the concentration of local anaesthetic used. A total of 28 trials including 1559 participants reported a decrease in time to first faeces (stool) (SMD -0.67, 95% CI -0.86 to -0.47; low quality of evidence; equivalent to 22 hours). Thirty-five trials including 2731 participants found that pain on movement at 24 hours after surgery was also reduced (SMD -0.89, 95% CI -1.08 to -0.70; moderate quality of evidence; equivalent to 2.5 on scale from 0 to 10). From findings of 22 trials including 1154 participants we did not find a difference in the incidence of vomiting within 24 hours (risk ratio (RR) 0.84, 95% CI 0.57 to 1.23; low quality of evidence). From investigators in 17 trials including 848 participants we did not find a difference in the incidence of gastrointestinal anastomotic leak (RR 0.74, 95% CI 0.41 to 1.32; low quality of evidence). Researchers in 30 trials including 2598 participants noted that epidural analgesia reduced length of hospital stay for an open surgery (SMD -0.20, 95% CI -0.35 to -0.04; very low quality of evidence; equivalent to one day). Data on costs were very limited.

AUTHORS' CONCLUSIONS

An epidural containing a local anaesthetic, with or without the addition of an opioid, accelerates the return of gastrointestinal transit (high quality of evidence). An epidural containing a local anaesthetic with an opioid decreases pain after abdominal surgery (moderate quality of evidence). We did not find a difference in the incidence of vomiting or anastomotic leak (low quality of evidence). For open surgery, an epidural containing a local anaesthetic would reduce the length of hospital stay (very low quality of evidence).

Eat, drink, and be labouring?

The practice of restricting oral intake during labour has been and remains controversial. Overall, the nutritional needs of labouring women are poorly understood. This literature review reveals that little evidence exists to support the general restriction of oral intake for all labouring women. Education of health professionals and pregnant women regarding intake in labour is required to encourage collaboration in the development and institution of appropriate policies in keeping with the available evidence for best practice.

Perioperative fasting in adults and children: guidelines from the European Society of Anaesthesiology

This guideline aims to provide an overview of the present knowledge on aspects of perioperative fasting with assessment of the quality of the evidence. A systematic search was conducted in electronic databases to identify trials published between 1950 and late 2009 concerned with preoperative fasting, early resumption of oral intake and the effects of oral carbohydrate mixtures on gastric emptying and postoperative recovery. One study on preoperative fasting which had not been included in previous reviews and a further 13 studies published since the most recent review were identified. The searches also identified 20 potentially relevant studies of oral carbohydrates and 53 on early resumption of oral intake. Publications were classified in terms of their evidence level, scientific validity and clinical relevance. The Scottish Intercollegiate Guidelines Network scoring system for assessing level of evidence and grade of recommendations was used. The key recommendations are that adults and children should be encouraged to drink clear fluids up to 2 h before elective surgery (including caesarean section) and all but one member of the guidelines group consider that tea or coffee with milk added (up to about one fifth of the total volume) are still clear fluids. Solid food should be prohibited for 6 h before elective surgery in adults and children, although patients should not have their operation cancelled or delayed just because they are chewing gum, sucking a boiled sweet or smoking immediately prior to induction of anaesthesia. These recommendations also apply to patients with obesity, gastro-oesophageal reflux and diabetes and pregnant women not in labour. There is insufficient evidence to recommend the routine use of antacids, metoclopramide or H2-receptor antagonists before elective surgery in non-obstetric patients, but an H2-receptor antagonist should be given before elective caesarean section, with an intravenous H2-receptor antagonist given prior to emergency caesarean section, supplemented with 30 ml of 0.3 mol l(-1) sodium citrate if general anaesthesia is planned. Infants should be fed before elective surgery. Breast milk is safe up to 4 h and other milks up to 6 h. Thereafter, clear fluids should be given as in adults. The guidelines also consider the safety and possible benefits of preoperative carbohydrates and offer advice on the postoperative resumption of oral intake.

Prophylactic acetaminophen does not prevent epidural fever in nulliparous women: a double-blind placebo-controlled trial

OBJECTIVE

Epidural analgesia is associated with a four- to five- fold increase in noninfectious maternal fever in nulliparous women. Fever prophylaxis may safely reduce both unnecessary neonatal sepsis evaluations and the potential effect of fever on the fetus.

STUDY DESIGN

We performed a randomized double-blind placebo-controlled study. Immediately after epidural placement, full-term nulliparas with a temperature of <99.5 degrees F received acetaminophen 650 mg or placebo, per rectum, every 4 hours. Tympanic membrane temperatures were measured hourly. Our power to detect an effect of acetaminophen treatment on maternal temperature over time was 90%.

RESULTS

In all, 21 subjects were randomized to each arm. Treatment with acetaminophen did not impact maternal temperature curves. Fever >100.4 degrees F was identical in the acetaminophen and placebo groups (23.8%, p=1.0). Neonatal surveillance blood cultures did not reveal occult infection.

CONCLUSIONS

Acetaminophen prophylaxis prevented neither maternal hyperthermia nor fever secondary to epidural analgesia, suggesting that the mechanism underlying fever does not include centrally mediated perturbations of maternal thermoregulation.

An evaluation of isotonic "sport drinks" during labor

We compared the metabolic effects of allowing women isotonic "sport drinks" rather than water to drink during labor. The effect of these drinks on gastric residual volume was also evaluated. Sixty women in early labor (cervical dilation <5 cm) were randomized to receive either isotonic sport drinks or water only. Plasma beta-hydroxybutyrate, nonesterified fatty acids, and glucose were measured in early labor and at the end of the first stage of labor. Residual gastric volume was assessed within 45 min of delivery by use of an ultrasound scanner. The incidence and volume of vomiting was recorded. At the end of the first stage of labor, plasma beta-hydroxybutyrate (P = 0.000) and nonesterified fatty acids (P = 0.000) had increased and plasma glucose (P = 0.007) had decreased significantly in the Water-Only group. Gastric antral cross-sectional area after delivery was similar in the two groups. The incidence of vomiting and the volume vomited during labor and within the hour of delivery were also similar. There was no difference between the groups in any maternal or neonatal outcome of labor. In conclusion, isotonic drinks reduce maternal ketosis in labor without increasing gastric volume.

IMPLICATIONS

Solid foods may endanger a woman's life if consumed during labor. Isotonic sport fluids were evaluated as a nutritional alternative. Results demonstrate that mothers who have not received parenteral opioids can safely drink isotonic drinks in active labor.

Policy or tradition: oral intake in labour

Oral intake restrictions have varied over time and around the world with written hospital policies for this issue often being non-existent. As there are differing views on this issue within hospitals overseas, a survey was conducted of 109 maternity units in New South Wales, Australia during early 2000 to identify the trends across the state. In New South Wales 81.7% of hospitals did not have a written policy for oral intake in labour. The remaining 18.3% had written policies which varied in their oral intake allowances from ice only to whatever women feel like eating and drinking. Of the 109 hospitals in this survey 60.5% leave food and fluid requirements to the individual woman's discretion, providing they have no increased risk of general anaesthetic.

Epidural local anaesthetics versus opioid-based analgesic regimens on postoperative gastrointestinal paralysis, PONV and pain after abdominal surgery

BACKGROUND

Gastrointestinal paralysis, nausea and vomiting, and pain, are major clinical problems following abdominal surgery. Anaesthetic and analgesic techniques that reduce pain and postoperative nausea and vomiting (PONV), and prevent or reduce postoperative ileus, may reduce postoperative morbidity, duration of hospitalisation and hospital costs.

OBJECTIVES

To compare effects of postoperative epidural local anaesthetic with regimens based on systemic or epidural opioids, on postoperative gastrointestinal function, postoperative pain, PONV and surgical/anaesthetic complications.

SEARCH STRATEGY

Trials were identified by computerised searches of the Cochrane Controlled Trials Register, MEDLINE, EMBASE and by checking the reference lists of trials and review articles.

SELECTION CRITERIA

Randomised controlled trials comparing the effects of postoperative epidural local anaesthetic with systemic or epidural opioids.

DATA COLLECTION AND ANALYSIS

Collected data included treatment in active (local anaesthetic) and control (opioid based) groups, time to first postoperative stool, time to first postoperative flatus, gastric emptying measured by the paracetamol absorption test, duration of the passage of barium sulphate, pain assessments, use of supplementary analgesics, nausea, vomiting and surgical/anaesthetic complications.

MAIN RESULTS

Most studies in this review involved a small number of patients. Furthermore half of the studies indicated a poor level of methodology in particular regarding blinding and report of withdrawals. Heterogeneity of included studies was substantial. Results consistently showed reduced time to return of gastrointestinal function in the epidural local anaesthetic group compared with groups receiving systemic or epidural opioid (37 hours and 24 hours, respectively). Postoperative pain was comparable. Two studies compared the effect of epidural local anaesthetic with a combination of epidural local anaesthetic and opioid on gastrointestinal function. One study favoured epidural local anaesthetic and one study was indifferent. A meta analysis of five of eight studies comparing the effect of epidural local anaesthetic with a combination of epidural local anaesthetic and opioid on postoperative pain, yielded a reduction in VAS pain scores (0-100 mm) on the first postoperative day of 15 mm, in favour of the combination. No significant differences in PONV were observed between epidural local anaesthetic and opioid based regimens.

REVIEWER'S CONCLUSIONS

Administration of epidural local anaesthetics to patients undergoing laparotomy reduce gastrointestinal paralysis compared with systemic or epidural opioids, with comparable postoperative pain relief. Addition of opioid to epidural local anaesthetic may provide superior postoperative analgesia compared with epidural local anaesthetics alone. The effect of additional epidural opioid on gastrointestinal function is so far unsettled. Randomized, controlled trials comparing the effect of combinations of epidural local anaesthetic and opioid with epidural local anaesthetic alone on postoperative gastrointestinal function and pain are warranted.

Fasting in labor: relic or requirement

OBJECTIVE

To evaluate the scientific literature on restrictions of eating and drinking during labor.

DATA SOURCES

Computerized searches in MEDLINE and CINAHL, as well as historical articles, texts, and references cited in published works. Key words used in the searches included anesthesia in labor, childbirth, eating and drinking, epidural, fasting, fasting in labor, fasting and pregnancy, gastric aspiration, gastric emptying, intrapartum, intravenous fluids, i.v.s in labor, ketonuria, ketonuria in labor, parturition, pregnancy, and stomach contents in labor.

STUDY SELECTION

Articles from indexed journals, excluding single-person case studies.

DATA EXTRACTION

Data were extracted and organized under the following headings: historical review, effects of fasting on labor, research on maternal mortality/morbidity from aspiration, research on gastric emptying in labor, intravenous hydration in labor, and implications for nursing research.

DATA SYNTHESIS

Research does not support restricting food and fluids in labor to prevent gastric aspiration. Restricting oral intake during labor has unexpected negative outcomes.

CONCLUSIONS

Little is known about the differences in labor progress, birth outcomes, and neonatal status between mothers who consume food and/or fluids during labor and women who fast during labor. Research also is needed on the effects of epidural opioids on gastric emptying, nutritional requirements during labor, and the physiologic implications of fasting during labor. Fasting during labor is a tradition that continues with no evidence of improved outcomes for mother or newborn. Many facilities (especially birth centers) do not restrict eating and drinking. Across the United States, most hospitals restrict intake, usually to ice chips and sips of clear liquids. Anesthesia studies have focused on gastric emptying, measured by various techniques, presuming that delayed gastric emptying predisposes women to aspiration. Narcotic analgesia delays gastric emptying, but results are conflicting on the effect of normal labor and of epidural anesthesia on gastric emptying. The effect of fasting in labor on the fetus and newborn and on the course of labor has not been studied adequately. Only one study evaluated the probable risk of maternal aspiration mortality, which is approximately 7 in 10 million births.

Neuraxial opioids in labour

Neuraxial opioids were first used for labour analgesia in 1980 following the description of spinal cord opioid receptors in 1979. Via these receptors in the dorsal horn, opioids modulate both the visceral and the somatic pain of labour. The onset and duration of action of the individual opioid are determined primarily by its relative lipid solubility. Neuraxial opioids have a local anaesthetic sparing effect, allowing the use of lower concentrations of both agents while maintaining analgesia. As a sole agent, intrathecal opioids can be used to provide analgesia during the first stage of labour, especially in the high-risk parturient. They also have a role in the management of perineal pain and the provision of rapid-onset analgesia. Unfortunately maternal and neonatal side-effects can occur, the most important being respiratory depression.

A comparison of the effect of intrathecal and extradural fentanyl on gastric emptying in laboring women

We studied gastric emptying, using acetaminophen absorption, in 105 women in labor divided into three equal groups of 35 each, after intrathecal (i.t.) (25 micrograms, Group S) or extradural (50 micrograms, Group E) fentanyl in combination with bupivacaine and compared with a control group (Group C) receiving extradural bupivacaine only. The time to maximal acetaminophen concentration (tCamax), maximal acetaminophen concentration (Camax), and areas under the acetaminophen concentration-time curve at 90 and 120 min (AUC90 and AUC120, respectively) were determined. Median (range) tCamax values were 120 (15-180), 82.5 (15-180), and 90 (15-180) min in Groups S, E, and C, respectively (P < 0.05). Mean +/- SD Camax was 13.4 +/- 8.82, 17.9 +/- 8.06, and 15.0 +/- 6.22 micrograms/mL in Groups S, E, and C, respectively (P < 0.05). Mean +/- SD AUC90 and AUC120 were also significantly smaller in Group S than in the other two groups (430 +/- 616, 736 +/- 504, and 672 +/- 453; and 649 +/- 592, 1063 +/- 627, and 1053 +/- 616 micrograms.mL-1.min-1 in Groups S, E, and C, respectively). We conclude that the administration of fentanyl 25 micrograms i.t. delays gastric emptying in labor compared with both extradural fentanyl 50 micrograms with bupivacaine and extradural bupivacaine alone.

IMPLICATIONS

We examined emptying of the stomach in women in labor after administration of analgesics by the spinal or the epidural route. We observed that the analgesic, fentanyl, administered by the spinal route, although relieving pain rapidly, may delay emptying of the stomach. In theory, delayed gastric emptying may increase the chance of vomiting and aspiration of gastric contents.

Preanaesthetic management of the obstetric patient

The obstetric patient presents unique challenges to the anaesthesiologist. The physiologic changes in the mother during pregnancy and the anaesthetic implications of these changes, associated with the pathophysiologic conditions frequently superimposed on the pregnancy, distinguish the parturient from the other patients about to undergo anaesthesia and surgery. Furthermore, the obstetric patient may be in acute pain from labour and frequently needs urgent surgical intervention because of sudden changes in the condition of the mother or the fetus.

Adding fentanyl 0.0002% to epidural bupivacaine 0.125% does not delay gastric emptying in laboring parturients

Previous studies have shown that bolus doses of fentanyl (50 and 100 micrograms) with epidural bupivacaine delay gastric emptying by up to 45 min. We studied the effect of the addition of small-dose fentanyl to epidural bupivacaine infusions on gastric emptying during labor. The acetaminophen absorption technique was used to infer gastric emptying. Twenty-eight patients in established labor consented to participate in the study. They were randomized to receive either 1) 10 mL bupivacaine 0.125% followed by an infusion of 0.125% bupivacaine at 10 mL/h or 2) 10 mL bupivacaine 0.125% with 50 micrograms fentanyl followed by an infusion of 0.125% bupivacaine and 0.0002% fentanyl at 10 mL/h. Two hours after initiation of epidural analgesia, each patient ingested 20 mg/kg acetaminophen in a suspension of 150 mL water. Venous blood samples were drawn for a baseline and then every 15 min for 2 1/2 h. There were no significant demographic differences between the groups. There were no differences detected between groups in the peak plasma concentrations of acetaminophen, the time to achieve the peak plasma concentrations, or the area under the curve at 45 and 90 min. Our results indicate that epidural infusions for labor analgesia using 0.125% bupivacaine and 0.0002% fentanyl do not delay gastric emptying compared to infusions of bupivacaine 0.125% alone.

Effect of epidural opioids on gastric emptying in labour

The effect of epidural opioids on gastric emptying was studied in 36 women in labour. Women who had received one dose of epidural bupivacaine were randomised to receive 10 ml of bupivacaine 0.25% alone (n = 8) with fentanyl 50 microg (n = 8) or with diamorphine 2.5 mg (n = 8), or 10 ml of bupivacaine 0.125% alone (n = 4) or with fentanyl 100 microg (n = 4) or with diamorphine 5 mg (n = 4) when they first requested a top-up. Mean+/-SD fentanyl concentrations measured at delivery were, in maternal venous plasma (MV) 0.72+/-0.19 ng/ml and in umbilical venous plasma (UV) 0.75+/-0.3 ng/ml. The mean dose-delivery interval was 280 min (range 107-608 min) and there was a negative correlation between UV/MV and dose-delivery interval. Gastric emptying was assessed by measuring paracetamol absorption following an oral dose of 1.5 g given 30 minutes after the study top-up. Time to peak plasma paracetamol concentration was significantly delayed in the groups given fentanyl 50 and 100 microg and diamorphine 5 mg, compared to the groups given bupivacaine alone, and peak concentration was significantly reduced in the group given diamorphine 5 mg. It is concluded that epidural fentanyl 50 and 100 mg and epidural diamorphine 5 mg delay gastric emptying. The addition of 2.5 mg diamorphine has no significant effect.