Effect of body position on qualitative and quantitative ultrasound assessment of gastric fluid contents

Ultrasonic assessment of gastric solid contents in patients undergoing upper endoscope with sedation

BACKGROUND

Perioperative reflux aspiration presents a grave concern during sedation or general anesthesia, particularly when solid gastric contents prompt acute upper respiratory obstruction, potentially resulting in fatal consequences for patients. Currently, there are limited means for promptly assessing solid gastric contents in clinical settings. Therefore, this study examined the efficacy of ultrasound assessment for solid gastric contents, offering a rapid and non-invasive approach for early detection and decision-making regarding interventions.

METHODS

The study included 400 patients scheduled for upper endoscopy procedures, which encompassed both gastroscope and gastroscope combined colonoscopy examinations with sedation. Ultrasound scanning of the antrum was performed while patients were positioned semi-sitting or in the right lateral decubitus (RLD) posture. The evaluation of solid gastric contents relied on direct visual observation during endoscopy. Gastric volume measurement occurred subsequent to endoscopic suction of gastric contents. Receiver operating characteristic curves were utilized to assess the effectiveness of ultrasonography in discerning solid contents.

RESULT

Seven patients undergoing gastroscope with sedation were found to have solid gastric contents. The sensitivity, specificity, positive predictive value, and negative predictive value of the ultrasound qualitative evaluation of solid contents were 85.7%, 99%, 60%, and 99.7%, respectively.

CONCLUSION

Solid stomach contents can be evaluated qualitatively with reasonable accuracy using ultrasonography. Additionally, in patients undergoing upper endoscopy and assessed to have solid gastric contents with ultrasound, administration of mild sedation is recommended.

TRIAL REGISTRATION

www.chictr.org.cn (ChiCTR2100048994); registered 19/07/2021.

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.

Preoperative gastric point-of-care ultrasound in nonelective surgical procedures in pediatric-aged patients

Background

Airway management for nonelective surgical procedures in the setting of trauma, pain, and opioid use can be complicated by the potential for aspiration due to delayed gastric emptying. Point-of-care ultrasound (POCUS) remains a useful tool for evaluating gastric content and volume in various clinical settings. The authors evaluated gastric volume and content in children scheduled for urgent and semi-urgent procedures to assess their aspiration risk.

Methods

After obtaining consent, gastric POCUS was performed in the preoperative holding area for pediatric patients scheduled for both elective and nonelective surgery. Qualitative and quantitative measurements of the gastric antrum were taken, and the risk of gastric aspiration was calculated. Additional data collected included patient demographics, the type of surgery, nil per os (NPO) status at the time of surgery, NPO status at the time of injury, and administration of opioids.

Results

The study cohort included 100 patients ranging in age from 3 to 17 years old (mean age 9.2 years). Out of these 100 patients, gastric scanning was successfully conducted in 98 patients. Sixteen of fifty-nine nonelective patients (27%) had received opioids for pain control prior to surgery. Among the 34 patients who had suffered an acute injury, 7 (21%) had been NPO for <8 hours at the time of the injury. Ninety-nine out of hundred patients had been NPO for at least 6 hours at the time of the gastric ultrasound. Based on our gastric ultrasound findings, all patients who were appropriately NPO had either Grade 0 or Grade 1 risk for aspiration, indicating a low risk of aspiration.

Conclusions

The preliminary data show that when patients presenting for nonelective surgery are appropriately NPO, they may have a low risk of aspiration. This information may help guide the choice of anesthetic induction technique, particularly when concerns exist about the safety of a rapid sequence induction. It allows for a more stable and controlled induction of anesthesia.

Diagnostic accuracy of a simple qualitative ultrasound assessment for the diagnosis of empty stomach in the adult: A supplementary analysis of a prospective observer-blind randomized crossover study

BACKGROUND

It has been reported that qualitative ultrasound assessment performed in the semi-upright position had high sensitivity to detect gastric fluid volume >1.5 mL.kg-1 . Nevertheless, the diagnostic accuracy of qualitative assessment for the diagnosis of empty stomach (fluid volume <0.8 mL.kg-1 ) has not been assessed. We aimed to assess the diagnostic accuracy of simple qualitative ultrasound assessment with and without head-of-bed elevation to 45° for the diagnosis of an empty stomach. We also aimed to determine the diagnostic accuracy of a composite ultrasound scale and clinical algorithm.

METHODS

We performed a supplementary analysis of a prospective observer-blind randomized crossover trial in which adult fasting volunteers attended two distinct sessions, with the head-of-bed angled either at 0° or 45°, in a randomized order. Three tests were performed within each session, each corresponding to a different (either 0, 50, 100, 150 or 200 mL) and randomized volume of water; the same volumes were ingested in both sessions, in a randomized order. Ultrasounds were performed 3 min after water ingestion, blindly to the volume ingested.

RESULTS

We included 20 volunteers in whom 120 measurements were analyzed. The sensitivity and specificity of the qualitative assessment in the semirecumbent position were 93% (95% CI: 68-100) and 89% (95% CI: 76-96), respectively. The composite scale and clinical algorithm did not have better diagnostic accuracy than the qualitative assessment performed with head-of-bed elevation. Without head-of-bed elevation, the clinical algorithm had significantly higher specificity (98% [95% CI: 88-100]) than qualitative assessment (67% [95% CI: 51-80]; p < 0.05).

CONCLUSION

These results suggest that qualitative assessment in the semirecumbent position had high diagnostic accuracy for the diagnosis of fluid volume <0.8 mL.kg-1 ; this method can be used in clinical practice for reliable diagnosis of empty stomach.

Ultrasonographic Assessment of Gastric Volume in Fasted Patients Undergoing Gastrointestinal Endoscopy Under Sedation

Purpose

In this prospective observational study, an ultrasonographic measurement of antral cross-sectional area (ACSA) was conducted to evaluate the gastric content and volume as well as to identify high-risk stomach in non-pregnant adult surgical patients adhering to preanesthetic fasting guidelines.

Patients and Methods

Fasted patients undergoing gastrointestinal endoscopy under sedation were included. Ultrasonographic measurements of ACSA were conducted in both semi-recumbent and right lateral decubitus positions before endoscopic procedures. Gastroscopy was employed to guide the measurement of suctioned gastric volume (GV). Ultrasonography was performed to assess gastric contents and identify patients with high-risk stomach. The relationship between ACSA and suctioned GV was also evaluated.

Results

ACSA was evaluated in 736 out of 782 patients. A significant positive correlation was discovered between ACSA in the right lateral decubitus position and suctioned GV, which was more reliable than in the semi-recumbent position. To analyze high-risk stomach with a GV > 100 mL, the cutoff value of ACSA in the right lateral decubitus was found to be 7.5 cm2, with the AUC, sensitivity and specificity of 0.80 (95% CI, 0.76-0.82; P<0.001), 82.4% and 67.3%, respectively. A novel mathematical model based on ACSA to estimate GV in non-pregnant fasted adults was presented.

Conclusion

Ultrasonographic measurement of ACSA can assist anesthesiologists in estimating the risk of pulmonary aspiration of gastric contents during general anesthesia and sedation.

Preoperative ultrasound evaluation of gastric contents in children one hour after ingestion of clear liquid: An observational study

Background

Gastric ultrasound is an effective, non-invasive method to assess the nature and volume of gastric content in the pediatric population. Recently, the UK, European, and French Pediatric Anesthesia Societies recommend fast for clear fluids in children for 1 h. However, studies showing that 1 h of fasting is safe in the pediatric population are still scarce. This study aims to verify by ultrasound evaluation if 1 h of fasting for clear liquids is sufficient to have an empty stomach before anesthetic induction.

Methodology

Patients between 11 months and 16 years of age scheduled for elective outpatient surgery were included. A qualitative and quantitative ultrasound evaluation was performed by calculating the cross-sectional area (CSA) of the gastric antrum, 1 h after ingesting a volume of 3 mL/kg of a non-carbonated sports drink, before anesthetic induction.

Results

Fifty patients were included. The average CSA measured by ultrasound was 2.85 ± 1.64 cm2 with an average calculated total volume of 12.9 ± 11.06 mL. All patients had an empty stomach criterion (calculated volume ≤1.5 mL/kg) during the ultrasound evaluation, with an average of 0.40 ± 0.23 mL/kg. With the qualitative assessment of gastric volume, 19 patients (38%) were classified as grade 0, 31 patients (62%) as grade 1, and none as grade 2.

Conclusion

One hour of fasting after ingestion of 3 mL/kg of a non-carbonated sports drink is sufficient to meet ultrasound criteria for an empty stomach in a pediatric population undergoing elective outpatient surgery.

Differences in preoperative gastric ultrasound findings in elderly compared to the mid-aged surgical patients: A retrospective observational study

This study aimed to compare gastric ultrasound assessments between young and elderly patients, to determine whether the cross-section area (CSA) cutoff values for elderly and young patients should be different, and to suggest CSA cutoff values for elderly patients. This study evaluated the data of 120 patients who underwent elective surgery under general anesthesia between July 2019 and August 2020. Demographic and gastric ultrasound assessment data were retrieved. Patients were divided into the elderly group (n = 58, age: ≥65 years) and young group (n = 62, age: <65 years). The CSAs in the supine and right lateral decubitus positions (RLDP), semiquantitative 3-point Perlas grade (grades 0, 1, and 2), and gastric volume (GV) were determined. CSAs according to different Perlas grades were compared between the 2 groups. To compare normally and non-normally distributed continuous data, Student t test and the Mann-Whitney U test were used, respectively. Categorical data were compared using the chi-square test or Fisher exact test, as appropriate. The receiver operating characteristic (ROC) curves were built for the CSAs to predict pulmonary aspiration. The CSA cutoff values for predicting a high risk of pulmonary aspiration in both the groups were determined. Among patients with Perlas grade 0, the CSAsupine (P = .002) and CSARLDP (P = .002) were greater in the elderly group than in the young group. The specificity, positive predictive value, and accuracy of the CSA decreased when the CSA cutoff value for the young group was applied to the elderly group. The CSA cutoff values for the elderly group were: CSAsupine, 6.92 cm2 and CSARLDP, 10.65 cm2. The CSA of the empty stomach was greater in elderly patients than in young patients. We suggest that the following CSA cutoff values should be used for predicting pulmonary aspiration risk in elderly patients: CSAsupine, 6.92 cm2 and CSARLDP, 10.65 cm2.

Ultrasound assessment of residual gastric volume in older adults undergoing staged-bilateral total knee arthroplasty after consuming carbohydrate-containing fluids: a prospective observational study

BACKGROUND

We compared preoperative residual gastric volume (GV) between the first and second stages of total knee arthroplasty (TKA) in older adults after drinking carbohydrate-containing fluid 2 h prior to surgery.

METHODS

In this study, 36 patients, aged > 65 years, scheduled for staged bilateral TKA with one-week interval, were enrolled. The patients consumed 400 ml of carbohydrate-containing fluid 2 h prior to surgery. Before the induction of spinal anesthesia, the gastric antral cross-sectional area was measured at the first and second TKA using ultrasound, and the residual GV was calculated. The primary outcome was the residual GV. Qualitative GV (grades 0, 1, and 2) and analgesic consumption after the first TKA were assessed as secondary outcomes.

RESULTS

The GV (median [Q1, Q3]) was greater in the second-stage TKA (41.1 [22.5, 62.8] ml) than in the first-stage TKA (10.3 [0.0, 27.1] ml) (P < 0.001). In the qualitative assessment, the distribution was not different between the two stages of TKA (P = 0.219) and only one patient showed grade 2 gastric content in the second TKA. When opioid consumption was converted to an equivalent dose of morphine, an average of 53.9 mg of morphine was required after the first TKA.

CONCLUSIONS

Residual GV after drinking carbohydrate-containing fluid differed according to the stage of TKA, showing a larger residual GV in the second TKA than in the first one. In older adults scheduled to undergo bilateral staged TKA, caution is required in preoperative fasting practice, especially in second-stage surgery.

Diagnostic performance of qualitative ultrasound assessment for the interpretation of point-of-care gastric ultrasound to detect high gastric fluid volume: A prospective randomized crossover study

STUDY OBJECTIVE

This study aimed to assess whether elevating the head of the bed to 45° was associated with sensitivity >90% of the qualitative ultrasound assessment for the diagnosis of gastric fluid volume > 1.5 ml.kg^-1. We also assessed the performance of qualitative assessment, composite ultrasound scale, and clinical algorithm, for the diagnosis of fluid volume > 1.5 ml.kg^-1 according to whether the head of the bed was elevated to 45° or not.

DESIGN

Prospective randomized observer-blind crossover trial.

SETTING

Hospices Civils de Lyon, France.

PATIENT

Healthy adult volunteers.

INTERVENTIONS

Two separate study sessions in fasting volunteers: with and without head-of-bed elevation to 45°, in a randomized order. Each session consisted of three tests, each corresponding to a randomized and different volume of water (either 0, 50, 100, 150 or 200 ml); the same volumes were used in both sessions and in a randomized order. Gastric ultrasounds were performed three minutes after the ingestion of water by an investigator blinded to the volume ingested.

MEASUREMENTS

Diagnostic performance of each approach for the diagnosis of gastric fluid volume > 1.5 ml.kg^-1.

MAIN RESULTS

Twenty volunteers were included, and 120 measurements were analyzed. The sensitivity of the qualitative assessment for the diagnosis of gastric fluid volume > 1.5 ml.kg^-1 with and without head-of-bed elevation was 91% (95%CI: 75-98) and 75% (95%CI: 57-89), respectively. The clinical algorithm with head-of-bed elevation had significantly better sensitivity than the qualitative assessment with no head-of-bed elevation; there was no significant difference for other comparisons.

CONCLUSIONS

The results suggest that qualitative examination of gastric antrum in the supine position with head-of-bed elevation to 45° can discriminate between low and high gastric fluid volume with high sensitivity, while neither the composite ultrasound scale nor the clinical algorithm improved the diagnostic performance of gastric ultrasound for the diagnosis of gastric fluid volume > 1.5 ml.kg^-1.

Ultrasound assessment of gastric volume in older adults after drinking carbohydrate-containing fluids: a prospective, nonrandomized, and noninferiority comparative study

PURPOSE

The aim of this study was to evaluate the safety of drinking carbohydrate-containing fluids two hours prior to surgery in older adults using ultrasonography.

METHODS

We conducted a nonrandomized and noninferiority comparative study in 60 patients aged over 65 yr who were scheduled for total knee arthroplasty. Patients who were fasted from midnight (fasting group) or who drank 400 mL of a carbohydrate-containing fluid (carbohydrate ingestion group) two hours prior to surgery were matched for age, sex, and body mass index. We measured the cross-sectional area (CSA) of gastric antrum using ultrasound and estimated the gastric fluid volume as the study's primary outcome measure. The noninferiority margin (δ) for the mean difference was predefined as 50 mL. The secondary outcome measures included CSA of the antrum and qualitative gastric volume.

RESULTS

The mean (standard deviation) gastric volume was not significantly different between the fasting group and the carbohydrate ingestion group (30.2 [25.4] mL vs 28.4 [35.8] mL; each group, n = 30; P = 0.81). The mean difference in gastric volume was -1.9 mL (95% confidence interval [CI], -17.9 to 14.2), and the upper limit of the 95% CI was lower than the prespecified noninferiority limit (δ = 50 mL). Secondary outcomes were not significantly different between the two groups.

CONCLUSION

Drinking of carbohydrate-containing fluid two hours prior to surgery was noninferior to overnight fasting with respect to residual gastric volume at induction of anesthesia in healthy older adults who undergoing total knee arthroplasty.

STUDY REGISTRATION

ClinicalTrials.gov (NCT04514380); registered 14 August 2020.

Observation on Application Effect of Arterial Puncture and Catheterization under Guidance of Intelligent Medical Care Ultrasound in Clinical Anesthesia

In clinical anesthesia and the rescue of critically ill patients, arterial puncture and catheterization are the most commonly chosen ways to establish central arterial access for patients. Invasive arterial puncture and catheterization facilitate the grasp of real-time vital sign information of patients during surgery, which strengthens patient monitoring during surgery and improves safety. However, the traditional method of arterial puncture and cannulation through palpation of the radial artery is often prone to complications related to mechanical injury, such as hemorrhage, hematoma, and accidental perforation of the artery. Studies have shown that ultrasound-guided radial artery puncture and cannulation can shorten the puncture cannulation time, reduce the incidence of complications related to puncture cannulation, and improve the success rate of puncture cannulation. In order to verify it, this paper uses the experimental group and the control group to conduct comparative experiments and uses the neural network method to evaluate the effects of the two methods. As a more mature method of artificial intelligence, BP neural network is widely used in a wide range of applications and has the characteristics of strong generalization ability and fast convergence, so we choose it as the base model. The specific work of this paper is as follows: (1) in-depth study of the relevant theory of BP neural network (BPNN), focusing on the structure of BPNN and the working principle of algorithm; the problems to be solved in the clinical anesthesia effect evaluation have laid a theoretical foundation for the establishment of an improved BPNN evaluation model in the following chapters. (2) introduce the basic principle of genetic neural network, analyze the benefits of combining genetic neural network and BPNN; introduce in detail the process of genetic algorithm to optimize the weights and thresholds of BPNN, and establish a GA-BP evaluation model. The test proves the feasibility and superiority of the model.

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.

Fasting does not guarantee empty stomach in the intensive care unit: A prospective ultrasonographic evaluation (The NUTRIGUS study)

BACKGROUND

In the intensive care unit (ICU), a fasting period is usually respected to avoid gastric aspiration during airway management procedures. Since there are no recognised guidelines, intensive care physicians balance the aspiration risk with the negative consequences of underfeeding. Our objective was to determine the impact of fasting on gastric emptying in critically ill patients by using gastric ultrasound.

MATERIAL AND METHODS

Among the 112 patients that met the inclusion criteria, 100 patients were analysed. Gastric ultrasonography was performed immediately before extubation. Patients with either 1/ an absence of visualised gastric content (qualitative evaluation) or 2/ a gastric volume < 1.5 mll/kg in case of clear fluid gastric content (quantitative evaluation) were classified as having an empty stomach.

MAIN FINDINGS

In our study, twenty-six (26%) patients had a full stomach at the time of extubation. The incidence of full stomach was not significantly different between patients who fasted < 6 h or patients who fasted ≥ 6 h. Among the 57 patients receiving enteral nutrition (EN) within the last 48 h, there was no correlation between the duration of EN interruption and the GAA. The absence of EN was not associated with an empty stomach.

CONCLUSION

At the time of extubation, the incidence of full stomach was high and not associated with the fasting characteristics (duration/absence of EN). Our results support the notions that fasting before airway management procedures is not a universal paradigm and that gastric ultrasound might represent a useful tool in the tailoring process. CLINICALTRIALS.GOV: NCT04245878.

A protocol implementation to determine aspiration risk in patients with multiple risk factors for gastroparesis

Patients with risk factors for gastroparesis are at increased risk for aspiration into the tracheobronchial tree. Current American Society of Anesthesiologists fasting guidelines use subjective measures to determine aspiration risk. A gastric ultrasound protocol can identify patients with risk factors for gastroparesis and determine the need to perform a point-of-care gastric ultrasound to objectively assess gastric antral contents. This enables the anaesthesia provider to assess patients at increased risk for aspiration. Additionally, many patients who present for surgery with risk factors for gastroparesis have an empty gastric antrum. Thus, the gastric ultrasound protocol checklist saves time and manpower requirements of anaesthesia staff without impacting patient safety or perioperative efficiency. A convenience sample of 40 patients consented for surgery was assessed using a screening tool to identify those at risk for gastroparesis and possible aspiration. Patients deemed at risk received a gastric ultrasound examination to evaluate for the presence of gastric contents. Over 12% of these patients had solid food gastric contents on exam. All patients with solid food gastric contents had an American Society of Anesthesiologists Physical Status Classification of 3 or higher, and two or more risk factors for gastroparesis.

A comparison of gastric gas volumes measured by computed tomography after high-flow nasal oxygen therapy or conventional facemask ventilation. Anaesthesia 2021;76:1184-1189. [PMID: 33651914 DOI: 10.1111/anae.15433]

High-flow nasal oxygen therapy is increasingly used to improve peri-intubation oxygenation. However, it is unknown whether it may cause or exacerbate insufflation of gas into the stomach. High-flow nasal oxygen therapy is now standard practice in our hospital for adult patients undergoing percutaneous thermal ablation of liver cancer under general anaesthesia with tracheal intubation. We compared gastric gas volumes measured from computed tomography images that had been acquired immediately after intubation in two series of patients: 50 received peri-intubation high-flow nasal oxygen therapy and another 50 received conventional facemask pre-oxygenation and ventilation before intubation and before high-flow nasal oxygen therapy became standard practice in our unit. Median (IQR [range]) gastric gas volume was 24.0 (14.2-59.9 [3-167]) cm³ in the high-flow nasal oxygen therapy group and 23.8 (12.6-38.8 [0-185]) cm³ in the facemask group. There was no difference between the two groups in the volume of gastric gas measured by computed tomography imaging (Mann-Whitney U-test, U = 1136, p = 0.432, n₁  = n₂  = 50). Our results demonstrate that a small volume of gastric gas is commonly present after induction of anaesthesia, but that the use of peri-intubation high-flow nasal oxygen therapy for pre-oxygenation and during apnoea does not increase this volume compared with conventional facemask pre-oxygenation and ventilation. This is clinically relevant, as high-flow nasal oxygen therapy is increasingly being used in a peri-intubation context and in patients at higher risk of aspiration.

American Society of Regional Anesthesia and Pain Medicine expert panel recommendations on point-of-care ultrasound education and training for regional anesthesiologists and pain physicians-part I: clinical indications

Point-of-care ultrasound (POCUS) is a critical skill for all regional anesthesiologists and pain physicians to help diagnose relevant complications related to routine practice and guide perioperative management. In an effort to inform the regional anesthesia and pain community as well as address a need for structured education and training, the American Society of Regional Anesthesia and Pain Medicine (ASRA) commissioned this narrative review to provide recommendations for POCUS. The guidelines were written by content and educational experts and approved by the Guidelines Committee and the Board of Directors of the ASRA. In part I of this two-part series, clinical indications for POCUS in the perioperative and chronic pain setting are described. The clinical review addresses airway ultrasound, lung ultrasound, gastric ultrasound, the focus assessment with sonography for trauma examination and focused cardiac ultrasound for the regional anesthesiologist and pain physician. It also provides foundational knowledge regarding ultrasound physics, discusses the impact of handheld devices and finally, offers insight into the role of POCUS in the pediatric population.

Real-Time Ultrasound Detection of Left Paratracheal Esophagus on Air Entry into the Gastric Antrum in the Induction Period of General Anesthesia: A Prospective, Randomized Study

Background

Positive-pressure ventilation (PPV) delivered via a facemask during anesthesia induction can result in gastric content being inhaled into the lungs. We hypothesized that the real-time ultrasound left paratracheal esophagus monitoring could more effectively reduce air entry into the stomach than real-time ultrasound monitoring of the gastric antrum (GA).

Methods

Patients were divided into two groups: study (S; n=30) and control (C; n=30) groups. During the induction of general anesthesia, mask ventilation adopts a pressure control mode. The initial ventilation pressure of both groups was 15 cmH₂O. Before anesthesia induction, an ultrasonic probe was used to monitor the cross-sectional area (CSA) of the GA and the presence of gas in the stomach. During and after anesthesia induction, group S used a high-frequency ultrasound probe to observe the entry of air from the left paratracheal esophagus into the GA. The ventilation pressure was gradually reduced over time until no esophageal air was found. In group C, the ventilatory pressure was set maintained at 15 cmH₂O and the CSA of the GA and air intake were monitored using an ultrasonic probe.

Results

Before and after PPV, the CSA of the GA in group S decreased (P<0.001), whereas the CSA in group C increased (P=0.002). The GA CSA in group C after PPV was larger than in group S after PPV (P=0.002). The proportion of patients who experienced intragastric air intake in group S (23.3%) was significantly lower than that in group C (66.7) (P=0.001).

Conclusion

Compared with ultrasound monitoring of the GA, real-time ultrasound detection of LPEOAE into the GA during anesthesia induction was more effective, more sensitive, significantly reduced the prevalence of intragastric air intake, and provided sufficient tidal volume and oxygen for patients.

The Obese Patient: Facts, Fables, and Best Practices

The prevalence of obesity continues to rise worldwide, and anesthesiologists must be aware of current best practices in the perioperative management of the patient with obesity. Obesity alters anatomy and physiology, which complicates the evaluation and management of obese patients in the perioperative setting. Gastric point-of-care ultrasound (PoCUS) is a noninvasive tool that can be used to assess aspiration risk in the obese patient by evaluating the quantity and quality of gastric contents. An important perioperative goal is adequate end-organ perfusion. Standard noninvasive blood pressure (NIBP) is our best available routine surrogate measurement, but is vulnerable to greater inaccuracy in patients with obesity compared to the nonobese population. Current NIBP methodologies are discussed. Obese patients are at risk for wound and surgical site infections, but few studies conclusively guide the exact dosing of intraoperative prophylactic antibiotics for them. We review evidence for low-molecular-weight heparins and weight-based versus nonweight-based administration of vasoactive medications. Finally, intubation and extubation of the patient with obesity can be complicated, and evidence-based strategies are discussed to mitigate danger during intubation and extubation.

Ultrasonographic evaluation of gastric content and volume: a systematic review

SUMMARY OBJECTIVE: Bronchoaspiration of gastric content is associated with high morbidity and mortality, but evaluating this complication is a difficult task. However, gastric ultrasonography can safely assess gastric content and prevent bronchoaspiration. Therefore, a systematic review was performed in order to verify the efficacy of ultrasonography in the qualitative and quantitative analyses of gastric content. METHODS: A literature review of articles published between 2009 and 2019 in the PubMed and LILACS databases was conducted using combinations of the keywords “gastric ultrasound,” “gastric emptying,” and “gastric content.” RESULTS: Of the 20 articles found, 19 chose the antral region as the best site for qualitative analysis of the gastric content. Regarding quantitative measurement, the most commonly used method to calculate the gastric volume in eight articles was the formula “Gastric Volume = 27 + (14.6 × ATAG) − (1.28 × Age),” in which the area of the transverse section of the gastric antrum (ATAG) could also be calculated by the largest antral diameters or by free tracing. CONCLUSION: An efficient evaluation of the gastric content can be performed by ultrasonography of the antral region, contributing to greater safety in the clinical management of patients with increased risk for bronchoaspiration during airway management.

Effects of a Preoperative Carbohydrate-Rich Drink Before Ambulatory Surgery: A Randomized Controlled, Double-Blinded Study

Background

The guidelines recommend oral carbohydrates up to 2 hr before elective surgery. The objective of this study was to explore the safety and feasibility of preoperative carbohydrate drink in patients undergoing ambulatory surgery.

Material/Methods

Patients undergoing ambulatory surgery under general anesthesia were enrolled. They were fasted from midnight and randomly assigned to a study group (200 mL of a carbohydrate beverage) or the control group (pure water) and received the assigned drink 2 hr before surgery. Bedside ultrasonography was performed to monitor gastric emptying at T₀ (before liquid intake), T₁ (5 min after intake), T₂ (1 hr after intake), and T₃ (2 hr after intake). Subjective feelings of thirst, hunger, anxiety, and fatigue were assessed 1 hr after liquid intake using the visual analogue scale (VAS).

Results

In both groups, gastric antrum cross-sectional area, gastric content volume, and weight-corrected gastric content volume increased at T₁ and returned to baseline at T₃. These parameters were significantly higher in the study group at T₂ (6.28±1.38 vs. 4.98±0.78, 67.22±29.49 vs. 49.04±15.4, 1.10±0.51 vs. 0.85±0.37, P<0.05). Thirst and hunger VAS scores were reduced in both groups. The study group suffered significantly less hunger (28.44±10.41 vs. 36.03±14.42, P<0.05). Blood electrolytes (sodium, potassium, calcium) and glucose concentration levels were similar in both groups at T₂. No gastric regurgitation or pulmonary aspiration was recorded.

Conclusions

Administration of 200 mL of oral carbohydrate beverage 2 hr before ambulatory surgery is safe, effective, and can be used for preoperative management of fasting patients.