An ultrasonographic analysis of gastric volume in patients posted for elective gastrointestinal surgeries

Introduction

In anaesthesia practice, respiratory complications such as anaesthesia-related aspiration can be fatal. Incidence of respiratory complications is 1 in every 2–3,000 operations requiring anaesthesia. Almost half of all the patients who aspirate during surgery, develop an aspiration related lung-injury, such as pneumonitis or aspiration pneumonia(1).Preoperative fasting aims at prevention of such perioperative pulmonary aspiration. Preoperative fasting is defined as prescribed period of time before a procedure when patients are not allowed the oral intake of liquids or solids.The American Society of Anaesthesiologists’ (ASA) recommendations for preoperative fasting are followed to prevent this dreaded complication.

In our institute, we follow ERAS protocol in all patients who are posted for elective gastrointestinal surgeries.Our study is an audit of 200 patients to assess the residual gastric volume using ultrasonography and to retrospectively analyse if there is a correlation between residual volume and risk factors of gastroparesis and thereby assess if the fasting guidelines for these patients need to be revisited.

Aim and objective:

To assess gastric volume using ultrasound in patients posted for elective gastrointestinal surgeries.

Patients

The study will involve patients scheduled to undergo elective gastrointestinal surgery.

Sample size

A convenient sample size of 200 patients.

Inclusion criteria:

1. Age>18yr

2. Patients posted for elective gastrointestinal surgeries.

Exclusion criteria:

1. Refusal to consent

2. Age>85

3. Emergency surgery including gastric outlet obstruction , bowel obstruction

4. Indications for rapid sequence induction of anaesthesia

5. Pregnancy(13)

6. BMI of <19 or >40(13)

7. Large abdominal mass likely to interfere with US imaging

Methodology

After informed consent, patients will be recruited into the study. All the patients in the study would be given clear liquids according to the fasting guidelines.After routine anaesthetic checkup and review of laboratory investigation,we will record any risk factors for gastroparesis.The time since the last meal and last intake of clear liquids will be noted.

In our study, we will assess the gastric volume of patients posted for elective gastrointestinal surgeries by ultrasonography, post induction of anaesthesia. The method of induction will be as per the discretion of the OT anaesthetist.After quantitative assessment of gastric volume,we will do a retrospective analysis if there is any correlation of increased gastric volume with risk factors leading to gastroparesis. Also we will see if there is any negative correlation i.e. gastric volume <1.5ml/kg in the presence of risk factors for gastroparesis.

1 operator [intensivist experienced in abdomen ultrasonography(14)] will assess the gastric volume post induction with ultrasonography. After induction, the patient will be positioned in the right lateral decubitus position.A curved array low-frequency transducer (2– 5 MHz) with standard abdominal settings will be used to identify the relevant anatomic landmarks and a curvilinear high-frequency transducer will be used to obtain detailed images of the gastric wall. Our site of assessment will be gastric antrum.It is found superficially between the left lobe of the liver anteriorly and the pancreas posteriorly in a sagittal or para- sagittal scanning plane in the epigastrium. Important vascular landmarks including both the aorta or inferior vena cava (IVC) and either the superior mesenteric artery or vein can be used to standardize a scanning plane through the antrum.

Quantitative assessment will comprise of taking antral CSA (cross section area) by measuring 2 perpendicular diameters i.e. AP = antero-posterior diameter and CC = craniocaudal diameter and the formula of the area of an ellipse will be applied

CSA = (AP×CC ×π)/4

(AP = antero-posterior diameter and CC = craniocaudal diameter).

The model used for assessment will be: Perlas and colleagues(13)

Formula : Gastric Volume (ml)=27.0+14.6×right-lateral CSA(cm2)-1.28×age (yr)

Statistical analysis:

The gastric volume will be categorized into two groups. The group one is <=1.5ml/kg and other group is >1.5 ml/kg. Categorical data will be presented as counts and percentages. Correlation between gastric volume and risk factors of gastroparesis in patients posted for elective gastrointestinal surgeries will be compared using Chi-square test or Fisher-exact test as appropriate. Statistical significance will be defined as p<0.05.