A nasogastric (NG) tube is a flexible tube inserted through the nose, down the throat, and into the stomach, often used to deliver nutrition or medication when oral intake is not possible. Checking residual volume from an NG tube helps assess how well the stomach is emptying, playing a role in patient safety and the effectiveness of tube feeding.
Understanding Residual Volume
Residual volume refers to the amount of fluid remaining in the stomach from previous feedings or medications, typically consisting of administered formula, water, and natural digestive secretions. Measuring this volume helps determine if the stomach is processing contents effectively. Checking residual volume helps prevent complications such as aspiration, where stomach contents enter the lungs, and ensures that the patient is tolerating the feeding regimen. A high residual volume can indicate delayed gastric emptying, which increases the likelihood of discomfort, reflux, or vomiting. Proper nutrient absorption is also linked to appropriate gastric emptying.
What You Need to Check Residuals
Gathering all necessary supplies ensures a smooth and hygienic procedure. You will need a large syringe, typically with a capacity of 30 to 60 milliliters, for withdrawing stomach contents. Gloves should always be worn to maintain cleanliness and prevent the spread of germs. A clean container or a measuring cup is also essential for accurately measuring the aspirated fluid. Additionally, pH paper might be used to verify the tube’s placement by testing the acidity of the stomach contents.
Step-by-Step Guide to Checking Residuals
Before starting, wash your hands and put on gloves. Explain the procedure to the individual to help them understand and cooperate. Ensure the person is positioned comfortably, ideally with the head of the bed elevated to at least 30 to 45 degrees, which helps reduce the risk of aspiration.
Next, temporarily disconnect the NG tube from any feeding apparatus or clamp it to prevent leakage. Attach the large syringe (30-60 mL) to the end of the NG tube securely. Gently and slowly pull back on the plunger to withdraw the stomach contents into the syringe. It is important to aspirate slowly to avoid collapsing the tube or causing discomfort.
Observe the amount and characteristics of the aspirated fluid, noting its color and consistency. Measure the total volume of the residual contents in the syringe or by emptying the syringe into a clean measuring container. If the aspirated fluid appears to be gastric contents, a small amount can be placed on pH paper to confirm an acidic pH, typically between 1 and 5.5, which helps verify the tube’s placement in the stomach.
After measuring, most or all of the aspirated residual volume should be returned to the stomach. This step is important because the fluid contains electrolytes and nutrients that the body needs. Re-instill the contents by slowly pushing the plunger back into the tube.
Once the residual has been returned, flush the NG tube with about 30 milliliters of water to help maintain its patency and clear any remaining contents. Finally, reconnect the NG tube to the feeding apparatus or cap it securely as appropriate for the ongoing treatment plan. Document the volume, color, and consistency of the residual, as well as the actions taken.
What Your Residual Volume Means
Interpreting aspirated residual volume involves understanding expected amounts and when further action may be necessary. The stomach naturally holds some fluid, including digestive juices and any previously administered formula. Therefore, a small amount of residual volume is typically expected.
While specific medical thresholds can vary by institution and individual patient needs, a common general guideline for a significant residual volume might be around 200 to 250 milliliters, or sometimes up to 500 milliliters, especially in critically ill patients. If the residual volume is consistently high, it may indicate delayed gastric emptying, suggesting the stomach is not processing fluids as quickly as expected. In such cases, a healthcare professional might decide to temporarily hold the feeding for a period, such as one to two hours, and then recheck the residual.
Residual volume is just one indicator of feeding tolerance. Other signs, such as abdominal distension, nausea, vomiting, or discomfort, are also considered when assessing how well a patient is tolerating their tube feeding. The decision to adjust or hold feedings should be based on a comprehensive assessment rather than solely on the residual volume.
Common Issues and When to Contact a Healthcare Professional
Difficulty aspirating fluid is a common problem, where the syringe pulls back little to no contents. If this occurs, try repositioning the individual, perhaps having them lie on their right or left side for a few minutes, which can help pool gastric contents in an accessible area. Instilling a small amount of air (1 to 2 mL) into the tube can also help move the tube away from the stomach wall, potentially allowing for aspiration.
Another issue is a clogged tube, which can prevent aspiration or the flow of formula. If a blockage is suspected, gently attempting to flush the tube with warm water using a push-pull motion with the syringe may help dislodge it. Never force the syringe, as this could damage the tube.
Several signs indicate that you should contact a healthcare professional immediately. These include consistently high residual volumes that do not decrease after holding feedings, or if the individual exhibits signs of distress such as vomiting, persistent coughing, or difficulty breathing during or after a feeding. Other red flags include significant abdominal pain, distension, or if the tube appears to be dislodged or moved from its original marked position. Any signs of blood in the tube or stomach contents also warrant immediate medical attention.