Ultrasonographic evaluation of gastric content during labour under epidural analgesia: a prospective cohort study

Ultrasound assessment of gastrointestinal luminal contents: a narrative review

Gastro-intestinal ultrasound (GIUS) is a non-invasive and cost-effective tool, widely used as a first-line diagnostic method in patients presenting with abdominal complaints, especially in patients affected by inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis. In this setting, gastro-intestinal ultrasound has been especially used to evaluate the bowel wall features (thickening, stratification, vascularization) and complications related to IBD (fistulas, abscesses). Nevertheless, gastro-intestinal ultrasound can be also used to detect and evaluate the content of several segments of the gut. In fact, there is a growing interest in utilizing GIUS for suspected functional disorders, where assessing intestinal content may play a significant diagnostic role, as well as directing therapy. In our review, we provided a sonographic description of GIUS appearances of bowel content in various pathological and physiological conditions, offering potential applications in clinical practice and providing insights for further research.

Gastric emptying in pregnancy and its clinical implications: a narrative review

Delayed gastric emptying increases the risk of pulmonary aspiration during anaesthesia for Caesarean delivery. Our aim in conducting this narrative review was to consider the effect of pregnancy on gastric emptying. The indices of gastric emptying after liquids, solids, or both and when fasted in the various trimesters of pregnancy, at the time of Caesarean delivery, in labour, and the postpartum period were assessed. We considered 32 observational studies, one nonrandomised controlled study, and 22 randomised controlled trials. The evidence indicates that, compared with the nonpregnant state, gastric emptying is decreased in the first but not the second and third trimesters. Before elective Caesarean delivery, carbohydrate drink or tea with milk leads to no difference in gastric cross-sectional area at 2 h relative to fasting or water. Following a standard fast for elective Caesarean delivery, patients may still have high-risk gastric contents. Compared with the nonpregnant state and third trimester, gastric emptying is delayed in labour, although the choice of analgesia has modifying effects. Systemic opioids delay gastric emptying. Epidural analgesia increases gastric emptying, but not back to baseline. Intrathecal analgesia delays gastric emptying relative to epidural analgesia. Women in labour who have eaten solids in the last 8 h still have high-risk gastric contents present in the stomach. The evidence with respect to the postpartum period is conflicting. In conclusion, inconsistencies in the literature reflect the unpredictability of gastric emptying in pregnancy and underline the potential value of gastric ultrasound in women who are pregnant.

Diagnostic accuracy of a simple qualitative ultrasound assessment for the diagnosis of high-risk gastric contents in the parturient. A prospective observational cohort study

STUDY OBJECTIVE

Interpretation of gastric ultrasound relies on the use of a clinical algorithm that combines qualitative analysis of the gastric antrum contents with the calculation of the volume of fluid contents. This reference method may be difficult to apply in the parturient. We therefore aimed to assess the diagnostic accuracy of a simple qualitative assessment in the supine position for the diagnosis of high-risk gastric contents in the parturient. We also assessed the diagnostic accuracy of a composite scale and another clinical algorithm based on a mathematical model different to that used in the reference method.

DESIGN

Prospective observational cohort study.

SETTING

University hospital, Lyon, France.

PATIENTS

Adult women admitted to the delivery room.

INTERVENTIONS

Qualitative and quantitative gastric ultrasound examination within the first hour following admission.

MEASUREMENTS

With respect to the reference method, the diagnostic accuracy of a simple qualitative assessment for the diagnosis of high-risk gastric contents was assessed. The diagnostic accuracy of a composite scale and another clinical algorithm, and the agreement between each approach were also assessed.

MAIN RESULTS

A total of 235 parturients were included and analyzed. The simple qualitative assessment led to conclusive ultrasound assessment in 233 (99%) women, while the reference method led to conclusive assessment in 213 (91%) women (P < 0.05). The sensitivity and the specificity of the simple qualitative assessment were 97% (95%CI: 93 to 99%) and 96% (95%CI: 90 to 99%), respectively. These were not significantly different from those of the composite scale and the clinical algorithm. The four approaches showed almost perfect agreement with each other.

CONCLUSIONS

These results suggest that simple qualitative assessment may be useful in clinical practice to help the anesthesiologist in the assessment of gastric contents status and risk of aspiration.

Gastric Volume and Antral Area in the Fasting State: A Meta-analysis of Individual Patient Data

BACKGROUND

Pulmonary aspiration of gastric content is a serious anesthetic complication. Gastric point-of-care ultrasound can determine the type and volume of gastric content when clinical information is equivocal. However, a cutoff value of either antral cross-sectional area or volume that may be considered as the upper limit of normal in fasting subjects is still controversial. The aim of this study is to characterize the distribution of baseline antral area and volume in fasting adult subjects and to identify an upper limit (95th percentile) of these distributions.

METHODS

The authors conducted a meta-analysis of individual participant data of primary studies from an academic research network of investigators collaborating in gastric ultrasound. Studies between January 2009 and December 2020 were included.

RESULTS

Twelve primary studies met inclusion criteria and were included in the analysis with a sample size of 1,203 subjects. The 95th percentile of area values (measured in the right lateral decubitus) was 9.9 cm2 (95% CI, 9.4 to 10.4), and of volume, 2.3 ml/kg (95% CI, 2.3 to 2.4). In addition, an antrum grade 0 or 1 indicates a 98% probability of an antral area below the 95th percentile.

CONCLUSIONS

An area of 10 cm2 measured in the right lateral decubitus could be a simple, data-driven upper limit of antral area that could serve as a surrogate of upper limit of normal gastric volume values in fasting adults. These results are limited by the highly selected sampling of the studies included.

EDITOR’S PERSPECTIVE

Prevalence and factors associated with high-risk gastric contents in women admitted to the maternity unit for childbirth: a prospective multicentre cohort study

BACKGROUND

This multicentre prospective observational study sought to determine the prevalence and the factors associated with high-risk gastric contents in women admitted to the maternity unit for childbirth, and to identify the clinical situations in which ultrasound assessment of gastric contents would be most helpful (i.e. when the prevalence of high-risk gastric contents is close to 50%).

METHODS

Ultrasound assessments of gastric contents were performed within the first hour after admission to the maternity unit. The prevalence of high-risk gastric contents was calculated and variables associated with high-risk gastric contents were identified using logistic regression analyses.

RESULTS

A total of 1003 parturients were analysed. The prevalence of high-risk gastric contents was 70% (379/544; 95% confidence interval: 66-74%) in women admitted in spontaneous labour and 65% (646/1003; 95% confidence interval: 61-67%) in the whole cohort. Lower gestational age, increased fasting duration for solids, and elective Caesarean delivery were independently associated with reduced likelihood of high-risk gastric contents. In women admitted in spontaneous labour and in the whole cohort, the prevalence of high-risk gastric contents ranged from 85% to 86% for fasting duration for solids <6 h, 63%-68% for fasting 6-8 h, 54%-55% for fasting 8-12 h, and 47%-51% for fasting ≥12 h.

CONCLUSIONS

Around two-thirds of parturients had high-risk gastric contents within the first hour after admission to the maternity unit. Our results suggest that gastric emptying for solids continues in labouring women, and that gastric ultrasound would be most helpful when fasting duration is ≥8 h.

An observational study of gastric content in women scheduled for cesarean section or operative hysteroscopy

BACKGROUND

The estimation of gastric content in third trimester pregnant women has already been studied, conclusions remain contradictory. The aim of this study was to compare gastric content in pregnant and non-pregnant women using gastric ultrasound. We performed an observational two-center study of women scheduled for a cesarean section (CS group) and of non-pregnant women scheduled for hysteroscopy (HS group).

METHODS

Ultrasound evaluation was performed before surgery with measurement of antral cross-sectional area (CSA) in the semi-recumbent position (SRP), primary outcome, and in the right lateral position (RLD). Gastric fluid volume (GFV) was calculated. Results are expressed as medians (25th and 75th percentiles). Perlas Score was evaluated and expressed as number (percentage).

RESULTS

Sixty patients in the CS group and 64 in the HS group were analyzed. Antral CSA (SRP) was greater in the CS group (350 mm2 [236-415] vs. 247 mm2 [180-318]; P=0.001). Antral CSA (RLD) was also significantly greater in the CS group (P=0.027). GFV was not different between groups whether expressed in absolute value (P=0.516) or relative to weight (P=0.946) mL.kg-1. Perlas Score repartition was similar in both groups (P=0.860). Kappa coefficients of concordance between CSA, GFV and Perlas Score were slight or at best fair.

CONCLUSIONS

Our study confirmed that antral CSA is increased among pregnant women and outlined that antral CSA should not be used alone in the decision-making process especially when the results of indicators (antral CSA, GFV, and Perlas Grading Score) are discordant.

Effect of early oral carbohydrate intake after elective Cesarean delivery on maternal body temperature and satisfaction: a randomized controlled trial

PURPOSE

Although the Enhanced Recovery After Cesarean Delivery (ERAC) consensus statement provides recommendations for early postoperative drinking and eating, evidence from high-quality clinical research directly addressing parturients is sparse. Our objective was to assess if early oral carbohydrate intake after elective Cesarean delivery improves maternal recovery.

METHODS

In this randomized controlled trial, we enrolled parturients undergoing elective Cesarean delivery under spinal anesthesia with tympanic membrane temperatures ≤ 36.5 °C immediately upon arrival at the postanesthesia care unit. Parturients were randomized to either 100 mL of oral complex carbohydrate intake (group CC) or 10 mL of water (group C). The primary outcome was maternal tympanic membrane temperature. Other outcomes included maternal thermal comfort score, degree of shivering, satisfaction, degree of thirst and hunger, and gastric emptying assessed by ultrasonography.

RESULTS

We included 90 participants in the final analysis. The mean (standard deviation [SD]) maternal body temperature at 120 min after ingestion was 36.7 (0.3) °C in group CC and 36.6 (0.3) °C in group C (difference in means, 0.14 °C; 95% confidence interval, 0.02 to 0.26; P = 0.02). Furthermore, using repeated measure models, the linear trends of temperature changes over time between groups CC and C were significantly different (P = 0.04). The thermal comfort scores at 120 min after ingestion were higher in group CC than in group C (P = 0.02), and the linear trends of shivering score changes over time between groups CC and C also were different (P = 0.003). The mean (SD) visual analogue scale scores for maternal satisfaction were 84 (13) mm in group CC and 47 (20) mm in group C (P < 0.001). Nevertheless, at 90 and 120 min after ingestion, there were no differences between the two groups in the number of participants with a gastric antrum cross-sectional area > 10.3 cm2.

CONCLUSIONS

Early oral carbohydrate intake after Cesarean delivery helped to restore maternal body temperature postoperatively and improve maternal satisfaction. Nevertheless, the clinical importance of these finding is unclear, given that most of the differences were small. In addition, there was no delay in maternal gastric emptying after consumption of a complex carbohydrate beverage in the early post-Cesarean period.

STUDY REGISTRATION

www.chictr.org.cn (ChiCTR2000031085); first submitted 13 November 2022.

Prevalence of risk stomach in laboring women allowed to unrestrictive oral intake: a comparative cross-sectional study

Background

Although restricting food intake during labor is recommended by guidelines, intrapartum starvation has not been popular in some regions. We conducted this comparative cross-sectional study to determine the prevalence of risk stomach in non-fasted laboring women compared with fasted non-laboring women using gastric ultrasound.

Methods

Ultrasound examination of the antrum was performed in 50 term fasted non-laboring women before elective cesarean delivery and 50 laboring women allowed to eat and drink during active labor. Examinations consisted of the qualitative (antral grades, 0–3) and quantitative evaluation (antral cross-sectional area and calculated gastric volume) in the supine and right lateral decubitus (RLD) position. A risk stomach was defined as an antral grade ≥ 2 or grade 1 with gastric volume ≥ 1.5 ml· kg^− 1.

Results

No non-laboring women had grade ≥ 2, while 34 (68%) laboring women had grade ≥ 2. Nine (18%) non-laboring and 40 (80%) laboring women presented risk stomach (P < 0.001) (risk ratio: 4.4, 95% CI 2.4–8.2). Compared with non-laboring women, laboring women had larger antral area at “empty” stomach (grade 0) (437 mm² vs.350 mm² in supine, 571 mm² vs.480 mm² in RLD, P < 0.05) and cut-off values of antral area to discriminate a risk stomach (510 mm² vs. 453 mm² in supine, 670 mm² vs. 605 mm² in RLD).

Conclusions

This study confirms a higher prevalence of risk stomach presents in laboring women under a liberal eating policy, gastric ultrasound is therefore useful for this risk population if general anesthesia is required unexpectedly.

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.

Ultrasound assessment of gastric contents prior to placental delivery: A prospective multicentre cohort study

BACKGROUND

There is ongoing debate regarding the optimal general anaesthetic technique for manual removal of the placenta after vaginal delivery. Using ultrasound examination of the gastric antrum, this study aimed to assess the change in gastric contents during vaginal delivery and to determine the prevalence of stomach at risk for pulmonary aspiration in the immediate postpartum period before placental delivery.

METHODS

In this prospective multicentre cohort study, antral ultrasonography was performed at full cervical dilatation within the thirty minutes preceding the beginning of expulsive efforts and after vaginal birth, before placental delivery. High-risk gastric content was defined as the visualisation of any solid content in the antrum or antral cross-sectional area in the semi-recumbent position (SR-CSA) > 608 mm².

RESULTS

Twenty-six women were included and analysed. There was a significant decrease in both the proportion of patients with solid gastric content and the SR-CSA between the two-ultrasound examinations. Twenty-one patients (80.8%) exhibited a decrease in the SR-CSA during vaginal delivery. The prevalence of stomach at risk for pulmonary aspiration was significantly lower after vaginal delivery than before vaginal delivery (23.1% vs. 57.7%, P = 0.0004).

CONCLUSION

Our results suggest that gastric emptying is at least partially preserved during vaginal birth. Nevertheless, almost a quarter of women did have high-risk gastric content in the immediate postpartum period. Point-of-care antral ultrasonography may be of interest for the fast assessment of the gastric content status when a general anaesthesia is required for manual removal of retained placenta.

Prediction of postoperative nausea and vomiting by point-of-care gastric ultrasound: can we improve complications and length of stay in emergency surgery? A cohort study

Background

Postoperative nausea and vomiting and postoperative ileus are common after major digestive surgery and represent one of the significant problems in Acute Care Surgery.

The delivery model of emergency surgery needs to be improved in order to foster a patient-centered care.

The multimodal approach suggested by Enhanced Recovery After Surgery (ERAS®) Guidelines is gaining widespread acceptance but is difficult to apply to emergency surgery.

Ultrasound examination of the gastric antrum allows a reliable assessment of gastric contents and volume and might help contribute to improve perioperative care in the emergency setting.

Methods

Gastric ultrasound examinations were performed preoperatively and postoperatively on forty-one patients undergoing emergency abdominal surgery. Gastric cross-sectional area (CSA) was measured, in order to estimate the gastric volume. The data obtained were used to evaluate a possible relationship between delayed gastric emptying and postoperative adverse event.

Results

Gastric antrum detection rate varied from 31.8% in open up to 78.9% in laparoscopic surgeries (p = 0.003). Six patients experienced adverse outcomes, had an antiemetic therapy administered and/or a nasogastric tube inserted. Mean CSA was significantly higher in this group (12.95 cm² vs 6.12 cm²; p = 0.040).

Conclusions

Sensitivity of gastric ultrasound varies depending on surgical technique. A dilated gastric antrum is significantly related to postoperative adverse outcomes and a careful ultrasound follow-up might help tailor postoperative nutrition and antiemetic therapy. In patients who experienced adverse events, antral CSA showed an average increase of more than 50% over a period of 72 h after surgery. A relative measure could be used to predict the risk of postoperative ileus. Overall, gastric ultrasound seems to be a promising diagnostic tool and a useful way to integrate ERAS® protocol in emergency abdominal surgery.

Oral fluid intake during the first stage of labour: A randomised trial

BACKGROUND

Obstetric anaesthesia has been associated with concern for the inhalation of gastric contents for many years, justifying fasting during labour. However, many anaesthesiologists and obstetricians now allow fluid intake during labour.

OBJECTIVE(S)

We hypothesised that allowing oral fluid intake during labour is not associated with increased gastric contents. We used ultrasound assessment of gastric contents to evaluate this hypothesis.

DESIGN

A randomised, single-blind and intention-to-treat noninferiority trial comparing antral area measured by ultrasound in fasting parturients and in those who were allowed to drink fluid for 90 min after randomisation.

SETTING

Tenon University Hospital, Assistance Publique Hôpitaux de Paris, Paris, France.

PATIENTS

Pregnant women, aged from 18 to 40 years and from week 36 of an uncomplicated singleton gestation, were randomised into a fasting group and a fluid intake group after admission to the delivery room. Of the 184 patients screened, data from 125 were analysed: fasting group (62), fluid intake group (63).

INTERVENTION

Women in the fluid intake group were allowed to drink up to 400 ml of apple juice for 90 min after randomisation.

MAIN OUTCOME MEASURE

We compared the percentage of women with an 'empty stomach' between the two groups: empty stomach was defined as an antral cross-sectional area (CSA) less than 300 mm assessed in a semirecumbent position with a 45-degree head-up tilt.

RESULTS

At full cervical dilatation an antral CSA less than 300 mm was measured in 76 and 79% of the parturients in the fasting group and the fluid intake groups respectively (P = 0.633).

CONCLUSION

The current study reveals that the percentage of pregnant women with an 'empty stomach', defined by an antral CSA less than 300 mm in a semirecumbent position with a 45-degree head-up tilt, was comparable at full cervical dilation among those who remained nil by mouth and those allowed to drink up to 400 ml for 90 min after their randomisation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02362815.

[Normal childbirth: physiologic labor support and medical procedures. Guidelines of the French National Authority for Health (HAS) with the collaboration of the French College of Gynaecologists and Obstetricians (CNGOF) and the French College of Midwives (CNSF) - Mother's wellbeing and regional or systemic analgesia for labor]

INTRODUCTION

These guidelines deal with the parturient wellbeing in terms of hydration and regional and systemic pain management during labour.

METHOD

Guidelines were established based on literature analysis and experts consensus.

RESULTS

Clear liquids consumption is permitted all along labor and postpartum, without volume limitation, in patients at low risk of general anesthesia (grade B). The consumption of solid foods is not recommended during the active stage of labor (consensus agreement). It is recommended to promote on regional analgesia to prevent inhalation (grade A). Pain relief using regional analgesia is a part of normal childbirth. It is recommended to provide regional analgesia to parturient who wish these technics. Regional analgesia is the safest and most effective analgesic method for the mother (grade A) and the child (grade B). It is recommended to inform women on the analgesic technics, to respect their choice and consider the right for a parturient to change her strategy in obstetrical circumstances or in cases of untractable pain (consensus agreement). It is recommended to perform a "low-dose" regional analgesia that respects the experience of childbirth (grade A) and maintain it with a patient controlled epidural analgesia technics (grade A). There is no minimum cervical dilation to allow epidural analgesia (grade A). In cases of rapid labor or after delivery for revision, spinal or combined spinal epidural can be used (grade C). Epidural has not to be ended before birth (consensus agreement). Blood pressure and fetal heart rate must be monitored every 3minutes after induction and/or each 10mL bolus then hourly (consensus agreement). Systematic and preventive fluid loading is not needed if only due to regional analgesia (grade B). Deambulation or postures are allowed in the absence of motor block and must be traced and do not alter the distribution of the regional analgesia (grade C). The postures of childbirth do not alter regional analgesia spread (NP2). There is no effect low dose regional analgesia on the duration of obstetric labor, nor the rate of instrumental births or caesarean section (NP1). Systematic use of oxytocin due to epidural analgesia is neither useful nor recommended (AE). Regional analgesia has no side effect on the fetus or newborn (NP1). If regional analgesia is contraindicated or during the waiting time, alternatives analgesic drugs (entonox, nalbuphine and tramadol or pudendal block) can be used but their analgesic efficiency remains mediocre to moderate and they are associated with adverse maternal and especially neonatal side effects (NP2). Remifentanil, ketamine and volatile anesthetics are excluded from these recommendations.

CONCLUSION

The present guidelines were established to update wellbeing of normal parturient during normal labor: hydration is recommended and low dose patient-controlled regional (epidural and spinal) analgesia is the most effective and safest analgesic method.

The effects of labor on airway outcomes with Supreme™ laryngeal mask in women undergoing cesarean delivery under general anesthesia: a cohort study

BACKGROUND

Pregnancy is associated with higher incidence of failed endotracheal intubation and is exacerbated by labor. However, the influence of labor on airway outcomes with laryngeal mask airway (LMA) for cesarean delivery is unknown.

METHODS

This is a secondary analysis of a prospective cohort study on LMA use during cesarean delivery. Healthy parturients who fasted > 4 h undergoing Category 2 or 3 cesarean delivery with Supreme™ LMA (sLMA) under general anesthesia were included. We excluded parturients with BMI > 35 kg/m2, gastroesophageal reflux disease, or potentially difficult airway (Mallampati score of 4, upper respiratory tract or neck pathology). Anesthesia and airway management reflected clinical standard at the study center. After rapid sequence induction and cricoid pressure, sLMA was inserted as per manufacturer's recommendations. Our primary outcome was time to effective ventilation (time from when sLMA was picked up until appearance of end-tidal carbon dioxide capnography), and secondary outcomes include first-attempt insertion failure, oxygen saturation, ventilation parameters, mucosal trauma, pulmonary aspiration, and Apgar scores. Differences between labor status were tested using Student's t-test, Mann-Whitney U test, or Fisher's exact test, as appropriate. Quantitative associations between labor status and outcomes were determined using univariate logistic regression analysis.

RESULTS

Data from 584 parturients were analyzed, with 37.8% in labor. Labor did not significantly affect time to effective ventilation (mean (SD) for labor: 16.0 (5.75) seconds; no labor: 15.3 (3.35); mean difference: -0.65 (95%CI: - 1.49 to 0.18); p = 0.1262). However, labor was associated with increased first-attempt insertion failure and blood on sLMA surface. No reduction in oxygen saturation or pulmonary aspiration was noted.

CONCLUSIONS

Although no significant increase in time to effective ventilation was noted, labor may increase the number of insertion attempts and oropharyngeal trauma with sLMA use for cesarean delivery in parturients at low risk of difficult airway. Future studies should investigate the effects of labor on LMA use in high risk parturients.

TRIAL REGISTRATION

The study was prospectively registered at clinicaltrials.gov ( NCT02026882 ) on 3 January 2014.

Gastric point-of-care ultrasound (PoCUS) during pregnancy and the postpartum period: a systematic review

Personalised risk assessment of the likelihood of pulmonary aspiration is recommended for pregnant women undergoing general anaesthesia and gastric point-of-care ultrasound (PoCUS) may help to achieve this. Traditionally, risk assessment is based upon adherence to fasting times, but gastric emptying may vary during pregnancy and surgery often needs to be expedited. We systematically reviewed the evidence for gastric PoCUS up to August 2018 in pregnant and postpartum women to determine whether it can identify and quantify stomach contents, provide aspiration risk assessment via qualitative or quantitative means, and determine how gastric emptying is affected by pregnancy. Twenty-two articles comprising 1050 participants were included and studies were classified by qualitative or quantitative findings. The evidence suggests that gastric PoCUS is a reliable and feasible method of imaging the stomach in pregnancy in clinical practice. Qualitative assessment via the Perlas grading system can provide rapid assessment of gastric volume states. If fluid is visible, identification of patients at high risk of pulmonary aspiration requires measurement of antral cross-sectional area. Cut-off values of 608 mm² and 960 mm² are recommended in the semi-recumbent and right lateral semi-recumbent positions, respectively. Validated methods to quantify stomach volumes are available, however their usefulness is currently restricted to research. Gastric PoCUS also provides evidence that gastric emptying of ingested food is delayed by term pregnancy, labour and during the early postpartum period. However, the passage of fluids through the stomach appears unaffected throughout the peripartum period.

Prediction of Maternal and Fetal Pharmacokinetics of Dolutegravir and Raltegravir Using Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Predicting drug pharmacokinetics in pregnant women including placental drug transfer remains challenging. This study aimed to develop and evaluate maternal-fetal physiologically based pharmacokinetic models for two antiretroviral drugs, dolutegravir and raltegravir.

Effect of facemask ventilation with different ventilating volumes on gastric insufflation during anesthesia induction in patients undergoing laparoscopic cholecystectomy

Objectives:

To compare the occurrence of gastric insufflation during anesthesia induction in patients undergoing laparoscopic cholecystectomy, using facemask ventilation with different ventilation volumes.

Methods:

This is a prospective study of 54 patients undergoing laparoscopic cholecystectomy under general anesthesia between January 2018 and June 2018. Facemask ventilation with volume mode controlled at 6 ml/kg (group V6), 8 ml/kg (group V8) or 10 ml/kg (group V10) was applied for 120 seconds (sec) during anesthesia induction. Before facemask ventilation and at 120 sec of facemask ventilation, gastric insufflation was determined by ultrasonography. Gastric insufflation was also evaluated using direct vision of laparoscopy. Respiratory parameters were monitored.

Results:

The incidence of gastric insufflation in group V10 (55.6%) was significantly higher than that in groups V6 (11.1%) and V8 (16.7%). However, it showed no significant difference between groups V6 and V8. During facemask ventilation for 120 sec, carbon dioxide accumulation trend occurred in group V6, and group V10 exhibited evidence of hyper-ventilation. Group V8 might be considered the best balance between low gastric insufflation and effective lung ventilation.

Conclusion:

Facemask ventilation with a ventilation volume of 8 ml/kg seems to have adequate preoxygenation and avoid excessive gastric insufflation during anesthesia induction in laparoscopic cholecystectomy.

Ultrasound assessment of gastric antrum in term pregnant women before elective cesarean section

Background and objectives

Pregnant women are considered patients at risk for pulmonary aspiration of gastric contents. The study aim was to evaluate the gastric antral cross-sectional area using ultrasound.

Method

In this prospective study, 85 scheduled term pregnant women underwent gastric ultrasound. The outcomes were the measurement of the gastric antral cross-sectional area (main outcome), the estimated gastric volume, the incidence of pregnant women at risk for pulmonary aspiration, and the association between gastric antral cross-sectional area and clinical-demographic characteristics. Gastric antral cross-sectional area and gastric volume were compared according to body mass index <30 or ≥30.

Results

The median (IIQ) for gastric antral cross-sectional area was 4 cm² (2.8–6.3), for the estimated gastric volume it was 49.8 mL (33.7–87.2), and for the gastric volume estimated in mL.kg⁻¹ it was 0.62 mL.kg⁻¹ (0.39–0.95). The 95^th percentile [95% confidence interval (CI)] of the gastric antral cross-sectional area and the estimated gastric volume were ≤10.3 cm² (95% CI: 7.6–15.6) and 1.42 mL.kg⁻¹ (95% CI: 1.20–2.64), respectively. The incidence of pregnant women at risk for pulmonary aspiration was 3.5% (CI: 3.5 (1.2–9.8)). There was a positive correlation between gastric antral cross-sectional area and weight, p < 0.001 and body mass index <0.001. Patients with a body mass index ≥30 had a gastric antral cross-sectional area and an estimated gastric volume greater than those with a body mass index <30, respectively, p < 0.01 and p < 0.02.

Conclusion

Measuring the gastric antral cross-sectional area of pregnant women is feasible and easy. There was positive correlation between gastric antral cross-sectional area, body weight and body mass index. The estimation of gastric volume by measuring the gastric antral cross-sectional area can identify patients at risk for pulmonary aspiration. Obese patients had a gastric antral cross-sectional area and an estimated gastric volume greater than non-obese patients.

[Ultrasound assessment of gastric antrum in term pregnant women before elective cesarean section]

BACKGROUND AND OBJECTIVES

Pregnant women are considered patients at risk for pulmonary aspiration of gastric contents. The study aim was to evaluate the gastric antral cross-sectional area using ultrasound.

METHOD

In this prospective study, 85 scheduled term pregnant women underwent gastric ultrasound. The outcomes were the measurement of the gastric antral cross-sectional area (main outcome), the estimated gastric volume, the incidence of pregnant women at risk for pulmonary aspiration, and the association between gastric antral cross-sectional area and clinical-demographic characteristics. Gastric antral cross-sectional area and gastric volume were compared according to body mass index <30 or ≥ 30.

RESULTS

The median (IIQ) for gastric antral cross-sectional area was 4cm² (2.8-6.3), for the estimated gastric volume it was 49.8mL (33.7-87.2), and for the gastric volume estimated in mL.kg^-1 it was 0.62mL.kg^-1 (0.39-0.95). The 95^th percentile [95% confidence interval (CI)] of the gastric antral cross-sectional area and the estimated gastric volume were ≤ 10.3cm² (95% CI: 7.6-15.6) and 1.42mL.kg^-1 (95% CI: 1.20-2.64), respectively. The incidence of pregnant women at risk for pulmonary aspiration was 3.5% (CI: 3.5 (1.2-9.8). There was a positive correlation between gastric antral cross-sectional area and weight, p <0.001 and body mass index <0.001. Patients with a body mass index ≥ 30 had a gastric antral cross-sectional area and an estimated gastric volume greater than those with a body mass index <30, respectively, p <0.01 and p <0.02.

CONCLUSION

Measuring the gastric antral cross-sectional area of pregnant women is feasible and easy. There was positive correlation between gastric antral cross-sectional area, body weight and body mass index. The estimation of gastric volume by measuring the gastric antral cross-sectional area can identify patients at risk for pulmonary aspiration. Obese patients had a gastric antral cross-sectional area and an estimated gastric volume greater than non-obese patients.

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.

Term pregnant patients have similar gastric volume to non-pregnant females: a single-centre cohort study

BACKGROUND

The physiological changes of pregnancy can increase the risk of peri-partum pulmonary aspiration. There is limited objective information regarding gastric volumes in pregnant patients. The aim of this cohort study was to characterise prospectively the range of gastric-fluid volume in term non-labouring pregnant patients compared with a historical cohort of non-pregnant females.

METHODS

Fasted non-labouring term pregnant patients scheduled for elective Caesarean delivery underwent a standardised gastric ultrasound examination. Gastric content was evaluated qualitatively (type of content), semi-quantitatively (Perlas grades), and quantitatively (volume). The antral cross-sectional area and volume were compared with those of a retrospective cohort of non-pregnant females from the same institution. Descriptive statistics were used to describe the central tendency through mean and median values. Dispersion was evaluated with standard deviation and inter-quartile range, and the higher end of the distribution as 95th percentile.

RESULTS

Non-labouring pregnant (59) and non-pregnant (81) subjects were studied. The range of estimated total gastric-fluid volume (P=0.96) and volume per body weight (P=0.78) was not significantly different between cohorts. An estimated volume of 115 ml (102-143) vs 136 ml (106-149) and volume per body weight of 1.4 ml kg^-1 (1.2-2.8) vs 2.0 ml kg^-1 (1.5-2.7) corresponded to the 95th percentile (95% confidence interval) values in the pregnant and non-pregnant cohort, respectively.

CONCLUSIONS

Baseline gastric volume of non-labouring pregnant patients at term is not significantly different from that of non-pregnant females. This information will be helpful to interpreting findings of gastric point-of-care ultrasound in obstetric patients.

Ultrasound assessment of gastric content in the immediate postpartum period: a prospective observational descriptive study

INTRODUCTION

Pulmonary aspiration of gastric contents in pregnant women undergoing general anesthesia or sedation/analgesia in the peripartum period is a feared complication in obstetric anesthesia. We assessed the changes in antral cross-sectional area (CSA) with ultrasonography in laboring women and in the immediate postpartum period.

PATIENTS AND METHODS

In an observational study in a university-affiliated maternity, gastric ultrasonography examinations were performed in non-consecutive laboring women, after epidural analgesia insertion and after childbirth. Assessment of antral CSA, difficulty of performance on a numerical scale, and factors that could influence gastric content were noted. A cut-off value of 381 mm² was taken for the diagnosis of empty stomach.

RESULTS

One hundred women were enrolled in the study. Median antral CSA was 469 mm² [25th-75th] [324-591] after epidural insertion and 427 mm² [316-574] after delivery. Antral CSA was ≥ 381 mm² in 59 of 90 women (65%) after epidural insertion vs. 48 of 100 women (48%) after delivery (P = 0.59). Median variation of antral CSA between two measurements was 36 mm² [-42 to 114]. Gastric ultrasonography was significantly more difficult to perform during labor than immediately post-delivery (median difficulty score 5 [2-7] vs. 2 [1-4], P < 0.0001). No risk factors (pain, anxiety, diabetes, smoking) were significantly associated with the occurrence of full stomach post-delivery.

CONCLUSION

This study demonstrated that 48% of parturients in the immediate postpartum period presented an antral CSA ≥ 381 mm² , cut-off being accepted for diagnosis of empty stomach and emphasizes the need for re-assessing before any general anesthetic procedure.

Modified B-ultrasound method for measurement of antral section only to assess gastric function and guide enteral nutrition in critically ill patients

AIM

To establish a modified B-ultrasound method of measuring the antral section only to assess gastric motility in healthy people, and evaluate its application in guiding enteral nutrition (EN) in critically ill patients.

METHODS

First, 30 healthy volunteers were selected. The modified B-ultrasound method and the traditional B-ultrasound method were applied to assess gastric function. The correlation of indices of gastric function between the two groups was analyzed statistically. In addition, 64 critically ill patients were selected, and the modified B-ultrasound method and the gastric juice withdrawal method were applied to guide the implementation of EN. Daily caloric value, the time required to achieve complete EN, ICU stay, hospitalization time, and serum prealbumin and albumin levels were recorded and compared between the two groups. Kaplan-Meier survival curve was used to compare the complications of EN between the two groups.

RESULTS

In healthy subjects, there was a good correlation among gastric emptying time, antral contraction frequency and antral motility index between the two groups (r = 0.57, 0.61 and 0.54, respectively). The study on critically ill patients also revealed that a better effect of EN was achieved in the modified B-ultrasound method group, in which patients had shorter ICU stay and hospitalization time and higher levels of serum prealbumin and albumin. The Kaplan-Meier survival analysis revealed that the improved B-ultrasound method was associated with significantly fewer EN complications (P = 0.031).

CONCLUSION

The modified B-ultrasound method can provide a good real-time assessment of gastric function and has a better effect than the traditional method in guiding EN in critically ill patients.

The Use of Ultrasonography in Obstetric Anesthesia

This article provides an overview of the use of ultrasonography in obstetric anesthesia. It discusses the indications, benefits, and techniques of using ultrasonography to optimize the delivery of anesthesia and provide safe and efficacious clinical care. More specifically, it discusses the use of ultrasonography to facilitate neuraxial anesthesia, abdominal field blocks, central and peripheral vascular access, as well as the assessment of the lung fields and gastric contents, and identification of the cricothyroid membrane.

Managing anesthesia for cesarean section in obese patients: current perspectives

Obesity is a worldwide epidemic. It is associated with increased comorbidities and increased maternal, fetal, and neonatal complications. The risk of cesarean delivery is also increased in obese parturients. Anesthetic management of the obese parturient is challenging and requires adequate planning. Therefore, those patients should be referred to antenatal anesthetic consultation. Anesthesia-related complications and maternal mortality are increased in this patient population. The risk of difficult intubation is increased in obese patients. Neuraxial techniques are the preferred anesthetic techniques for cesarean delivery in obese parturients but can be technically challenging. An existing labor epidural catheter can be topped up for cesarean delivery. In patients who do not have a well-functioning labor epidural, a combined spinal epidural technique might be preferred over a single-shot spinal technique since it is technically easier in obese parturients and allows for extending the duration of the block as required. A continuous spinal technique can also be considered. Studies suggest that there is no need to reduce the dose of spinal bupivacaine in the obese parturient, but there is little data about spinal dosing in super obese parturients. Intraoperatively, patients should be placed in a ramped position, with close monitoring of ventilation and hemodynamic status. Adequate postoperative analgesia is crucial to allow for early mobilization. This can be achieved using a multimodal regimen incorporating neuraxial morphine (with appropriate observations) with scheduled nonsteroidal anti-inflammatory drugs and acetaminophen. Thromboprophylaxis is also important in this patient population due to the increased risk of thromboembolic complications. These patients should be monitored carefully in the postoperative period, since there is increased risk of postoperative complications in the morbidly obese parturients.

Ultrasound in obstetric anesthesia

Ultrasound has permeated the practice of anesthesiology and is becoming an essential tool for the obstetric anesthesiologist in the labor and delivery suite. The most common applications include guidance for neuraxial (epidural and spinal) anesthesia and acute pain nerve blocks, as well as guidance for central and peripheral vascular access. Obstetric anesthesiologists are becoming increasingly familiar with diagnostic applications, including transthoracic echocardiography (TTE) and lung and gastric ultrasound. There is intense interest in developing standard curricula for achieving competency in ultrasound skills during residency training and expanding the role of ultrasound in education and research.