Ultrasound Assessment Of Gastic Residual Volume and Contents in Diabetic Surgical population – A Prospective Observational Study

Method of collection of data (Including sampling procedure, if any)

·     Surgical diabetic patients will be explained about the procedure and informed / written consent will be obtained.

·     Thorough pre anaesthetic evaluation is performed and routine investigations will be obtained.

·     They are advised to be nil per oral for both solids and liquids on the previous night of day of scheduled surgery as per ISA fasting recommendations, 6 hours fasting for solid food and non-human milk, 2 hours  for  clear fluids.

·     All the patients will be scanned in recovery room using portable ultrasound machine (Sonosite) with curvilinier probe of low frequency(2-5mhz) set in abdominal scan mode to assess basal gastric volume  and  contents, at around 7AM on the day of surgery before shifting to operating room.

·     Patient will be first scanned in a semi-recumbent (45 degrees head up) supine position, followed by right lateral position (RLP) by keeping the probe in sagittal plane in epigastric region. In both positions, the gastric antrum will be identified above the aorta or inferior vena cava, left lobe of liver anteriorly as reference points. The ultrasonographic examination will be done by the post graduate under the supervision of the guide.

·     A qualitative assessment will be performed to identify content in the stomach (solid or liquid) and gastric antral grading will be done as described by Perlas et alas follows:

Grade 0= absence of fluid in both supine and RLP; (Bull’s eye sign)

Grade 1=fluid in RLP only; (starry sky appearance)

Grade 2=fluid in both supine and RLP/ solid content (ground glass appearance)

Quantitative assessment will be done by measuring antral cross-section area (CSA).

The antral CSA will be calculated by measuring two perpendicular diameters in longitudinal (d1) and anteroposterior (d2) plane from serosa to serosa and using the formula CSA=π[d1×d2]/4 in supine and RLP.

The following mathematical model will be used to calculate the gastric volume(GV) in ml/kg.

Volume=27.0+ (14.6×right-lateral CSA) - (1.28×age).

Patients are categorized into low-risk group for aspiration (empty antrum or residual GV Ë‚1.5ml/kg) and high-risk group (solid contents or GV˃1.5ml/kg)

Detailed history related to duration of diabetes mellites, diabetic medications (oral hypoglycemics or insulin, dose and schedule) symptoms of gastropathy (fullness, heart burn and abdominal bloating), type of last meal, number of fasting hours for solid and liquid diet (previous night) will be obtained. Type of diabetes mellitus, BMI, HbA1C levels, are noted down by the patient clinical records. In the absence of HbA1C level, fasting blood sugar will be noted. The gastric volume and contents are correlated with all these parameters.

      Design of study

Prospective Observational study

 Mention Sample Size with details

The mean right lateral position gastric volume was 58.63+/- 37.62 in a study conducted by asiye demirel et al. By considering standard deviation [SD] of 37, absolute error or precision [d] of 5 ml with type 1 error 5% and the confidence interval of 95%.

 Sample size for our study is calculated by the following formula:

SAMPLE SIZE = Z1-α/22 SD2 /d2                           [ Z1-α/2 = 1.96 AT CI OF 95%]

The calculated sample size is 208

By adding the drop outs of 10% [208 + 28 = 228]

The final sample size will be 230