|Year : 2019 | Volume
| Issue : 11 | Page : 1483-1488
Sonographic gastric content evaluation in patients undergoing cataract surgery
A Kaydu, E Gokcek
Department of Anesthesiology, Diyarbakır State Hopital, Diyarbakır, Turkey
|Date of Submission||05-Jul-2018|
|Date of Acceptance||31-May-2019|
|Date of Web Publication||13-Nov-2019|
Dr. A Kaydu
Department of Anesthesiology, Diyarbakir State Hospital, Diyarbakir - 21100
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Perioperative pulmonary aspiration of gastric contents is a serious complication and causes mortality and morbidity. The study aimed to assess the gastric content of patients undergoing cataract surgery by performing bedside ultrasonography. The secondary aim was to conduct a survey of hospital staff about fasting for cataract surgery. Subjects and Methods: This single-center, cross-sectional study included 65 patients who underwent cataract surgery. The quantitative and qualitative measurements of the gastric content and antral area were performed by gastric ultrasonography in the right lateral decubitus position. The incidence of risk to the stomach was defined according to different threshold levels: content >0.8 ml/kg and 1.5 ml/kg and cross-sectional antral area >340 mm2. A questionnaire was provided to anesthesiologists and ophthalmologists about fasting for cataract surgery. Results: The mean age was 69.48 ± 11.10 years. The mean gastric antrum cross-sectional area (CSA) was 11.08 ± 6.42 cm2. The predicted gastric volume was 103.39 ± 94.79 ml and 1.37 ± 1.20 ml/kg. The antral area CSA and gastric volume/kg decreased as the fasting time increased. About 98.5% of the patients exceeded the high-risk stomach antral cut-off CSA defined as 340 mm2. Gastric content exceeded 0.8 ml/kg in 58.33% of patients and exceeded 1.5 ml/kg in 41.67% of patients. Gastric content in patients was found to be 65.0% solid, 20.0% liquid, and 15.0% empty. All seven ophthalmologists did not apply fasting protocols for cataract surgery. Conclusion: Point of care ultrasonography is a useful, noninvasive tool in determining gastric content and volume. As majority of the patients presented with a full stomach for cataract surgery, we recommend that ophthalmologists and anesthesiologists follow preoperative fasting guidelines for cataract surgery.
Keywords: Cataract surgery, gastric antrum, gastric content, ultrasonography
|How to cite this article:|
Kaydu A, Gokcek E. Sonographic gastric content evaluation in patients undergoing cataract surgery. Niger J Clin Pract 2019;22:1483-8
| Introduction|| |
Cataract is a major cause of blindness and impaired visual acuity and, hence, cataract surgery is one of the most common surgical procedures performed in the world.
The prevalence of cataracts increases with age and a majority of the patients have comorbidities such as hypertension, diabetes mellitus, cardiorespiratory diseases, respiratory diseases, neurological problems, and dementia. Therefore, these comorbidities and mental status should be considered in management of anaesthesia. With the development of the open corneal phacoemulsification method, operations have been performed with reliable ocular and topical anesthesia. Despite the many advantages of topical anesthesia, there are some limitations. The patient must be sufficiently cooperative to successfully complete eye surgery under topical anaesthesia. Since many physicians allow patients to eat or drink before cataract surgery, these patients are at risk for gastric content aspiration.
Pulmonary aspiration of gastric content is a serious complication that causes mortality and morbidity. It has been reported as a major cause of mortality related to anesthesia. Factors such as volume, content, and acidity of the aspirated gastric contents can affect patient outcome. For this reason, preoperative fasting is crucial for patient safety. In anesthesiology societies, preoperative fasting guidelines for patients have been developed for local, general, and regional anaesthesia and sedative procedures. According to the fasting guidelines by the American Society of Anesthesiology (ASA), 2 hours for liquids, 6 hours for light meals, 8 hours for high-calorie or high-fat meals are recommended.
Despite these preoperative fasting guidelines, a truly empty stomach cannot be guaranteed, especially in patients with diabetes mellitus, esophageal hernias, and gastrointestinal system passage problems. As a result, several devices and methods have been used to ascertain gastric contents preoperatively. Bedside gastric ultrasonography is a tool used to measure gastric contents to determine the risk of pulmonary aspiration. Qualitative (solid, liquid, and empty) information about gastric content can be obtained and the gastric volume can be derived by determining the cross-sectional area.,,
In our study, we aimed to determine the preoperative aspiration risk by performing gastric antral measurements via gastric ultrasonography in patients undergoing cataract surgery.
| Materials and Methods|| |
Ethics, consent and permissions
This observational, prospective study was reviewed and approved by the institutional review board at the Diyarbakir Gazi Yasargil Training and Education Hospital, ID: 100, 2017, Diyarbakir/Turkey. Written informed consent was obtained from all patients.
The criteria for inclusion in the study were age >18 years, height >150 cm, BMI <40 kg/m 2, patients undergoing elective cataract surgery, and patients who understood the study protocol. Patients with upper gastrointestinal pathologies, hiatal hernia, gastric tumors, and history of esophageal gastric surgery were excluded. However, patients with gastrooesophageal reflux were not excluded from the study.
Gastric examinations of the patients were performed by experienced sonographers (at least 5 years of USG experience and at least 100 gastric USGs and gastric antrum counting experience) who were not aware of the patients' fasting time. Sonographic scanning was performed according to the protocol described by Perlas et al.
A 2–5 MHz curvilinear array low-frequency transducer (Sonosite ® M-Turbo Bothell WA, USA) was used for USG measurements. Patients' quantitative and qualitative examinations were performed in the right lateral decubitus (RLD) position. To enable visualization of the gastric antrum, body, and fundus with the transducer, the sagittal plane was scanned along the parasagittal line from the epigastric region. The left lobe or caudal lobe of liver anteriorly, the pancreas, the inferior vena cava or aorta were taken as reference points., Three serial images of the gastric antrum were obtained at rest when there were no peristaltic contractions. The probe was tilted to obtain the optimal transverse cross section of the antrum and exclude the oblique cross section. The whole thickness of the antral area was obtained. The antrum was empty (when the anterior and posterior walls were juxtaposed) [Figure 1]a. The hypoechoic content and the distended wall appearance of the gastric antrum proved that the cavitary lumen contained “liquid”. After consumption of solid food, the posterior wall of the antrum is blurred because of air mixing with food during chewing and swallowing. Therefore, the scan had to be repeated after the air content in the stomach diminished. As the air moved away from stomach, the solid material appeared as a mixture of echogenicity referred to as a “frosted-glass” appearance., [Figure 1]b In the RLD position, as fluid and solid contents descend toward the antrum via the gravitational effect, the air in the antrum moves away toward the body and the fundus region, resulting in better image optimization.
|Figure 1: (a) Sonographic image of the gastric antrum in the epigastric area with empty stomach. The muscularis propriae is seen as a hypoechoic layer within the gastric wall. SMA = superior mesenteric artery. (b) Gastric ultrasound images of the antrum of solid content. The mixture of echogenicity called “frosted-glass” appearance. The antral cross-sectional area is calculated using the Free tracing method|
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The free tracing method (FTM) was used to measure the cross-sectional antral area by drawing lines manually determined by the ultrasound calliper section. In a study by Kruisselbrink et al. comparing the FTM and traditional methods, (CSA = AP × CC × ð ÷ 4), a simple and practical method described by Bolondi et al. showed similar results. After CSA was calculated, the total gastric volume was measured by a mathematical model tested and validated by Perlas et al.
Stomach volume (mL) = 27+14.6 × CSA (cm 2)− 1.28 × age (in years)
In our study, we used a cut-off value of 340 mm 2 for antral cross-sectional area to define a “risk stomach,” according to Bouvet et al. Furthermore, a “risk stomach” was also defined by the presence of solid particles orgastric fluid volume >0.8 ml/kg  or >1.5 ml/kg.
A short questionnaire looking into preoperative fasting in patients undergoing cataract surgery was provided to 12 anesthesiologists and 7 ophthalmologists.
A descriptive analysis of the demographic data (age, weight, height and BMI), gender, and ASA classification was performed. The data were summarized using mean and standard deviation. The Shapiro–Wilk test was used to verify the assumption of normal distribution of continuous variables. The Pearson method was used for the coefficient of correlation. If variables were normally distributed, central tendency was expressed as the mean (SD). Categorical data were expressed as count and percentages or ratios. Differences were considered significant if P < 0.05. Statistical analysis was performed using SPSS 20 software (IBM, Armonk NY, USA).
| Results|| |
A total of 65 patients were enrolled. Detailed sonographic imaging could not be obtained due to body habitus in three patients and due to a BMI >40 ml/kg 2 in two other patients. Therefore, these five patients were excluded from the study [Figure 2]. The study was completed with 60 patients; 40 males and 20 females (M/F: 2:1). Demographic data is shown in [Table 1]. The mean age was 69.48 ± 12.58 (34–96) years. Findings for preoperative comorbidities are as follows; 40.0% patients had hypertension, 23.3% patients had cardiovascular diseases, 16.7% patients had diabetes mellitus, and respiratory diseases were recorded in 8.3% of patients. The mean BMI value was 26.79 ± 4.20 kg/m 2 (16.85–36.26).
The quality of the patients'stomach contents and the mean CSA ratios are shown in [Table 2]. The mean RLD CSA of the patients was 11.08 ± 6.42 (1.21–29.50) cm 2. The predicted gastric volume was 103.39 ± 94.79 ml. and 1.37 ± 1.20 ml/kg. The composition of the patients' gastric contents was found to be 65.0% solid, 20.0% liquid, and 15.0% empty.
|Table 2: Quantitative and qualitative characterisitcs of gastric content|
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Patients were assigned two different cut-off values for “risk stomach” classification and high rates were detected in both classifications. (0.8 ml/kg, 58.33% of patients; 1.5 ml/kg, 33% of patients). In addition, a CSA of >340 mm 2 was detected in 98.5% of patients [Table 3].
|Table 3: Characteristics of the “Risk Stomach” according to different threshold levels|
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As expected, the antral area CSA and gastric volume/kg both decreased as the fasting time increased (r = −0.573, P < 0.001; r = −0.539, P < 0.001) [Figure 3]a, [Figure 3]b.
|Figure 3: (a) Correlation of the antral cross-sectional area with fasting time. (b) Correlation of gastric volume (ml/kg) with fasting time|
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All patients were asked if they had been informed about preoperative fasting. Of all patients, 15% were found to have undergone at least 6 hours of fasting. However, th is time was related to the expected waiting time for surgery at service, not due to preoperative fasting guidelines. The short questionnaire survey conducted reported that all ophthalmologists thought that preoperative fasting is not necessary for cataract surgery with topical anesthesia. All ophthalmologists planned preoperative fasting in patients who are planning sedation or general anesthesia. Of the 12 anesthesiologists surveyed, nine (75%) thought that preoperative fasting guidelines should be applied prior to cataract surgery under topical anesthesia while 10 anesthesiologists (83.3%) replied that preoperative fasting is necessary for sedation in cataract surgery.
| Discussion|| |
In our study of sonographic evaluation of gastric content and gastric antral size in patients who underwent cataract surgery, we found that the majority of patients' gastric contents were above the “risk stomach” classifications (>0.8 ml/kg and 1.5 ml/kg). We also found that ophthalmologists did not prescribe preoperative fasting before surgery to patients.
Cataract surgery improves visual functions, thus reducing mortality, falls, and depression., In comparison with our study, patients who undergo cataract surgery are mostly elderly and have systemic diseases. A significant proportion of patients also present with comorbidities undiagnosed prior to their cataract surgeries. The majority of cataract surgeries are elective. Therefore, the medical condition of the patient should be optimized until the surgery is performed. Anesthesia in cataract surgery is performed mostly under topical anesthesia, followed by regional anesthesia (retrobulbar and peribulbar block). Sedation is performed in less than 1% of patients and general anesthesia is rarely required. Preoperative fasting protocols for cataract surgeries vary among countries and centers. Although many hospitals have fasting protocols for cataract surgery, these protocols are often not applied. Patients consume food and drinks for reasons including thirst, hypoglycemia, nausea and vomiting. They are advised to make breakfasts before surgery and take medications. There is no change in daily life routine.
In a study conducted in 50 UK hospitals via mail and telephone, 86% of the patients were given a preoperative fasting protocol as official policy, but 44% of patients were allowed to eat and drink up to the operation which was conducted under regional ophthalmic anesthesia. In our hospital, seven ophthalmologists indicated in our questionnaire that they did not apply the preoperative fasting protocols. Of the 12 anesthesiologists in our center, nine thought that preoperative fasting guidelines should be applied prior to cataract surgery under local anesthesia. The majority of anesthesiologists (83.3%) commented that they would never give supplemental sedation to nonfasted patients.
Although cataract surgery with topical anesthetics is safe in elderly and in firm patients, complications can develop. The most common adverse events in cataract surgeries were hypertension and preoperative arrhythmias. In a study of 30,000 cataract surgeries, Maltby et al. stated that pulmonary aspiration of gastric contents was not observed in any patients, although eight patients lost conciousness. Sanmugasundam et al. retrospectively analyzed 5,125 patients who underwent cataract surgery and detected no complications related to aspiration of gastric contents. However, they stated that the methodology of their study was inconclusive because the results depended on the recall of the anesthesiologists and to the past medical records. Taylor et al. reported a case in which a 77-year-old female underwent cataract surgery under local anesthesia. She subsequently developed sudden pulmonary postoperative edema and was urgently intubated orotracheally. Preoperative fasting is an important issue that ensures patient safety. Postoperative emesis, a detrimental effect of ophthalmic surgery, can be reduced by preoperative fasting. Furthermore, given the potential for general anesthesia in patients who do not respond to regional anesthesia, fasting protocols should be considered.
Although there are several methods to evaluate gastric contents like paracetamol absorption, electrical impedance tomography, radiolabelled diet, polyethylene glycol dilution, and gastric content aspiration, none of these methods are effective. Gastric USG has been used by gastroenterologists to diagnose gastric wall lesions such as cancer and to study gastric motility. To evaluate perioperative pulmonary aspiration risk, recent studies have used gastric USG to measure gastric content and volume. The gastric antrum was evaluated in supine, sitting, semi-sitting, and RLD positions. The RLD position was preferred because the displacement of gastric contents due to the gravitational effect enabled more accurate calculations and lower detectable volumes.,, The gastric antrum is the preferred segment for ultrasonographic imaging because it reflects the entire organ content., Perlas et al. concluded that gastric antral CSA measurement in the RLD position best correlated with gastric volume. Similar to other studies, a linear positive correlation between gastric CSA and gastric fluid volume was detected in our study like other studies.,
Majority of the patients in our study had high full stomach rates. In addition, even in patients with a long fasting duration, a risk of gastric content was found. In animal studies, the amount of gastric content found to cause aspiration pneumonia was between 0.4 and 0.8 ml/kg (25–50 ml), which is not sufficient to cause damage. Bouvet et al. used 0.8 ml/kg gastric content as a threshold level. Moreover, they found that the cut-off value of 340 mm 2 for antral CSA can be accepted as “risk stomach” with a 91% sensitivity, a negative predictive value of 94%, a specificity 71%, and a positive predictive value of 63%. Putte et al. concluded in their retrospective cohort study of fasted surgical patients that a gastric volume of 1.5 ml/kg was a realistic threshold value. In our study, 98.5% of patients had an antral CSA value >340 mm 2. The predicted gastric volumes for most of our patients were above both threshold levels of 0.8 ml/kg (58.33% of patients) and 1.5 ml/kg (41.67% of patients).
These results suggest us that patients undergoing cataract surgery have a high volume of gastric contents which poses a great risk of negative outcomes such as pulmonary aspiration.
However, there are some limitations to our study. There was no control group due to the cross-sectional characteristic of the study. Therefore, controlled studies should be performed to determine how patients with different comorbidities are affected by volume of gastric contents. We also had no information about the patient groups such as obese patients (>40 kg/m 2), elderly patients (>95 years), and patients with memory disorders (Alzheimer's disease, dementia, etc.).
| Conclusion|| |
As a result of this study, sonographic gastric measurements of patients who underwent cataract surgery showed us that majority of patients presented with full stomach, which is a risk factor for poor outcomes such as pulmonary aspiration of gastric contents. Therefore, we recommend that ophthalmologists and anesthesiologists follow preoperative fasting guidelines for cataract surgery.
USG = Ultrasonography, FTM = Free tracing method, RLD = Righ lateral decubitus, CSA = Cross-sectional antral area
This study was reviewed and approved by the institutional review board at the Diyarbakir Gazi Yasargil Training and Education hospital, ID: 102, 2017. Written informed consent was obtained from all patients.
Financial support and sponsorship
The study was funded by departmental resources.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]