Residual gastric volumes in patients receiving chronic haemodialysis after an overnight fast - a pilot study
Patients with chronic renal failure are considered to be at risk of perioperative pulmonary aspiration and consequently the recommendation is to perform a rapid sequence induction on such patients. Rapid sequence induction is not without its risks and may not be necessary. The aim of this study was to determine whether patients who are on a chronic haemodialysis program have sufficient residual gastric contents after an overnight fast, to place them at risk of pulmonary aspiration of gastric contents during anaesthesia. The presence and volume of gastric content was ascertained by ultrasound examination of the stomachs of twenty patients. Patients were asked to fast overnight and an ultrasound was scheduled for a morning on which the patient was due to come in for a dialysis session. The appearance of the stomach and the contents were graded by the radiologist and the diameters of the gastric antrum were then measured so that the cross sectional area could be calculated. Once the cross sectional area was known the gastric volume was calculated using a validated equation. The risk of perioperative pulmonary aspiration was then assessed according to the graded appearance as well as calculated gastric volumes. If the stomach was found to contain fluid a cut off value of 0.8ml/kg was used as a relative gastric volume that would place the patient at increased risk of perioperative pulmonary aspiration. Any patient with a gastric antrum found to be distended with fluid in both the supine and lateral positions or seen to contain solid contents was assessed as being at increased risk of perioperative pulmonary aspiration. Gastrointestinal symptoms were assessed and compared to residual gastric volumes. Urea and creatinine concentrations were also correlated to residual gastric volumes. In this study none of the patients with chronic renal failure on a chronic haemodialysis program were considered to be increased risk of perioperative pulmonary aspiration, after an overnight fast. Gastrointestinal symptoms were found in 60% of patients. There was no association between gastrointestinal symptoms and residual gastric volumes. There was no correlation between either urea or creatinine levels and residual gastric volumes.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Medicine in Anaesthesia Johannesburg, 2015