Pulmonary aspiration of gastric contents is a rare but serious complication of anaesthesia. Significant pulmonary complications happen in almost half of patients who aspirate and almost 50% of deaths in anaesthesia are directly due to aspiration of gastric contents, which occurs more commonly in patients with risk factors, at the time of induction of anaesthesia or during airway instrumentation.1 The practice guidelines of American Society of Anesthesiologists (ASA) for healthy adults consider a minimum fasting duration of 2 hrs for clear fluids, 6 hrs for a light meal and 8 hrs for a fatty meal, fried foods or meat to be safe so as to reduce the risk of aspiration of gastric contents. However, uncertainty still exists regarding the exact gastric residual volume (GRV) that places the patients at increased risk of aspiration despite following standard fasting guidelines.2 Trauma patients are at increased risk of pulmonary aspiration of gastric contents, because trauma affects gastric motility and emptying, in addition to many of the trauma patients having inadequate fasting status. Gastric emptying is highly dependent on an intact central nervous system, and is decreased in spinal cord trauma. It is generally assumed that there is delayed gastric emptying early in the post-trauma period, but there is less quantitative data concerning this patient population.3 Point-of-care ultrasound (POCUS) has been used in other studies to qualitatively assess the gastric contents and the risk of aspiration, and to quantitatively estimate the gastric residual volume (GRV) by measuring the antral cross-sectional area (ACSA).4 POCUS is relatively cheaper and easier to use bedside modality for this purpose in comparison to other modalities like gastric content aspiration, electrical impedance tomography, MRI and gastric scintigraphy.5 Gastric antrum scanned first with the patient in supine position and then in right lateral decubitus (RLD) position, can be used to for the same. Risk of aspiration can be assessed using the antral grading system developed by Perlas et al where empty antrum in both supine and RLD positions would be grade 0 indicating an empty stomach and minimum risk of aspiration, clear fluid in RLD position but empty in supine position would be grade 1 indicating an intermediate stomach, and clear fluid in both supine and RLD positions would be grade 2 indicating a full stomach, and is associated with maximum risk of aspiration.6 POCUS can be used to measure gastric antral cross-sectional area (ACSA) in RLD position of the patient using the following formula:7 ACSA = (CC × AP) × p with p = 3.14, where CC and AP are the cranio-caudal and antero-posterior diameters of the antrum respectively. Gastric residual volume can then be estimated from ACSA using the following formula:8 Stomach volume (mL) = 27 + 14.6 ACSA (in cm2) - 1.28 age (in years) We hypothesized that trauma patients scheduled for elective surgery after standard fasting guidelines and satisfying inclusion and exclusion criteria, will have a significantly higher GRV in comparison to non-trauma patients. We thus aim to assess the gastric residual volume in trauma patients using POCUS as primary objective, and to compare GRV in trauma patients and non-trauma patients, to assess risk of aspiration using the antral grading system, and to correlate measured GRV with duration after trauma and underlying co-morbidities if any, as secondary objectives.
REFERENCES 1. Cook TM, Woodall N, Frerk C; Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth. 2011 May;106(5):617-31 2. Ohashi Y, Walker JC, Zhang F, Prindiville FE, Hanrahan JP, Mendelson R, Corcoran T. Preoperative gastric residual volumes in fasted patients measured by bedside ultrasound: a prospective observational study. Anaesth Intensive Care. 2018 Nov;46(6):608-613 3. Carlin CB, Scanlon PH, Wagner DA, Borghesi L, Geiger JW, Long CL. Gastric Emptying in Trauma Patients. Dig Surg 1999;16:192-196 4. Shorbagy MS, Kasem AA, Gamal Eldin AA, Mahrose R. Routine point-of-care ultrasound (POCUS) assessment of gastric antral content in traumatic emergency surgical patients for prevention of aspiration pneumonitis: an observational clinical trial. BMC Anesthesiol. 2021 May 8;21(1):140 5. Van de Putte P, Perlas A. Ultrasound assessment of gastric content and volume. Br J Anaesth. 2014 Jul;113(1):12-22 6. Perlas A, Davis L, Khan M, Mitsakakis N, Chan VW. Gastric sonography in the fasted surgical patient: a prospective descriptive study. Anesth Analg. 2011 Jul;113(1):93-7 7. Bolondi L, Bortolotti M, Santi V, Calletti T, Gaiani S, Labò G. Measurement of gastric emptying time by real-time ultrasonography. Gastroenterology. 1985 Oct;89(4):752-9 8. Perlas A, Mitsakakis N, Liu L, Cino M, Haldipur N, Davis L, Cubillos J, Chan V. Validation of a mathematical model for ultrasound assessment of gastric volume by gastroscopic examination. Anesth Analg. 2013 Feb;116(2):357-63
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