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Diabetes and Preoperative Fasting: Examining Gastric Volumes and Aspiration Risk


Core Concepts
Patients with diabetes do not have significantly higher gastric volumes compared to non-diabetic patients after following standard preoperative fasting instructions, suggesting that different fasting guidelines may not be necessary.
Abstract
The study examined 84 people with diabetes (85% with type 2) and 96 without diabetes, all with a BMI < 40, who were undergoing elective surgery. After following standard preoperative fasting guidelines, a gastric ultrasound was used to assess their gastric contents. The key findings are: There was no significant difference in gastric volume between the two groups (0.81 mL/kg with diabetes vs 0.87 mL/kg without). The proportion with "full stomach" (any solid content or > 1.5 mL/kg of clear fluid) was also similar (15.5% with diabetes vs 11.5% without). The lead author suggests that the standard fasting instructions seem to be effective in assuring an empty stomach for most diabetic patients, and different fasting guidelines are generally not needed. However, an expert endocrinologist disputed the study's conclusions, noting that the participants were healthier than the general diabetes population and may not be representative. The expert also criticized the current ASA fasting guidelines for allowing clear liquids up to 2 hours before surgery, as this can still leave some residual stomach contents. Additionally, the widespread use of GLP-1 receptor agonists for diabetes and weight loss, which can delay gastric emptying, was not addressed in the study. The experts suggest that this new factor may require re-evaluation of the current fasting guidelines, particularly for patients taking these medications.
Stats
0.81 mL/kg gastric volume in patients with diabetes 0.87 mL/kg gastric volume in patients without diabetes 15.5% of patients with diabetes had "full stomach" 11.5% of patients without diabetes had "full stomach"
Quotes
"We never change practice completely based on a single study, but I think in general, based on our findings, that most diabetic patients aren't any different from nondiabetics when it comes to their gastric content after fasting, and our standard fasting instructions seem to be just as effective in assuring an empty stomach." "They've picked the wrong group of diabetics. This is not a group where you would expect a very high prevalence of delayed emptying." "Whether you have diabetes or not, if you are allowed to have a sugar drink up to 2 hours before your operation, the majority of people empty at about 4 kcal/min, so they will still have some of that drink in their stomach. If you want an empty stomach, the ASA guidelines are wrong."

Deeper Inquiries

How do the fasting guidelines need to be updated to account for the widespread use of GLP-1 receptor agonists, which can delay gastric emptying?

The fasting guidelines should be updated to address the impact of GLP-1 receptor agonists on gastric emptying. Given that these medications can delay gastric emptying times, there is an increased risk of pulmonary aspiration if patients have preoperative gastric contents. One approach to updating the guidelines could involve differentiating between liquids with and without calories. Currently, the ASA guidelines allow clear liquids, including those with calories, up to 2 hours before surgery. This poses a risk as most people empty at about 4 kcal/min, meaning they may still have liquid in their stomach at the time of the procedure. Therefore, a more nuanced approach that considers the specific effects of GLP-1 agonists on gastric emptying is necessary. Anesthesiologists may need to adjust fasting instructions based on the type and timing of GLP-1 agonist use to minimize the risk of perioperative pulmonary aspiration.

What are the potential risks and implications of the current ASA fasting guidelines allowing clear liquids up to 2 hours before surgery, even for non-diabetic patients?

The current ASA fasting guidelines allowing clear liquids up to 2 hours before surgery pose several risks and implications, especially for non-diabetic patients. Allowing liquids with calories close to the time of surgery can result in incomplete gastric emptying, increasing the risk of pulmonary aspiration during anesthesia. As most individuals do not completely empty their stomachs within 2 hours of consuming liquids, there is a higher likelihood of regurgitation and subsequent aspiration of gastric contents. This can lead to serious complications such as aspiration pneumonia, respiratory distress, and even death. Therefore, the current guidelines may not adequately ensure an empty stomach before surgery, putting patients at risk of perioperative pulmonary aspiration.

What other patient factors or comorbidities, beyond diabetes, should be considered when determining appropriate preoperative fasting protocols to minimize the risk of pulmonary aspiration?

In addition to diabetes, several other patient factors and comorbidities should be taken into account when establishing preoperative fasting protocols to reduce the risk of pulmonary aspiration. Patients with conditions such as gastroparesis, obesity, gastrointestinal motility disorders, and neurological conditions affecting gastric function may have delayed gastric emptying, increasing the risk of aspiration during anesthesia. Individuals with a history of reflux, hiatal hernia, or esophageal abnormalities are also at higher risk of regurgitation and aspiration. Furthermore, medications that affect gastric motility, such as opioids, anticholinergics, and certain psychiatric drugs, can impact the rate of gastric emptying and should be considered when determining fasting guidelines. By considering these additional factors and tailoring fasting instructions based on individual patient characteristics, healthcare providers can better mitigate the risk of perioperative pulmonary aspiration.
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