A Percutaneous Endoscopic Gastrostomy (PEG) tube is a feeding device placed directly into the stomach through the abdominal wall. Monitoring the Gastric Residual Volume (GRV) is a common practice in managing a PEG tube. GRV is the amount of contents remaining in the stomach after feeding, used to assess how well the stomach is emptying and tolerating the delivered nutrition.
Understanding Gastric Residual Volume
Gastric residual volume is the liquid aspirated from the stomach, consisting of the administered formula, water, and natural gastrointestinal secretions. The measurement is typically performed by connecting a large syringe to the PEG tube and gently withdrawing the contents. The primary reason for measuring GRV is to gauge gastric emptying speed and identify potential feeding intolerance.
A large volume of contents suggests delayed emptying, which could increase the risk of reflux or aspiration into the lungs. However, the measurement is dynamic and can be influenced by various factors, including tube size and position, syringe size, and the patient’s body position. Since the stomach is a reservoir, some residual volume is physiologically normal.
Establishing the Thresholds for High Residuals
Historically, lower volume cutoffs, such as 100 or 200 milliliters, were used to prompt the temporary halting of tube feeds. This strict approach often resulted in patients receiving inadequate nutrition, delaying recovery. Studies showed that withholding feeds for these lower volumes did not reduce complications like aspiration pneumonia.
Current, consensus-based guidelines from organizations like the American Society for Parenteral and Enteral Nutrition (ASPEN) have shifted toward a more permissive and evidence-based approach. For adults receiving gastric tube feeding, the recommendation is to avoid holding feeds for a GRV less than 500 milliliters in the absence of other signs of intolerance. Some guidelines even recommend against the routine monitoring of GRV entirely in critically ill patients, recognizing its poor correlation with aspiration risk.
The 500-milliliter threshold is typically considered over a 4 to 6-hour period. This reflects a significant change from older, restrictive protocols and acknowledges that a large GRV alone is a poor predictor of complications. Clinical judgment and the presence of other symptoms, not just the number, are now the primary drivers of intervention.
Factors that Increase Gastric Residual Volume
An elevated gastric residual volume is a sign of delayed gastric emptying, which can be triggered by a variety of non-feeding-related factors. Certain medications commonly administered to patients can slow down the natural movement of the gut, known as motility. Opioid pain medications and sedatives are known to depress the gastrointestinal tract, leading to content buildup.
Underlying patient conditions also play a significant role in gastric emptying. Patients with diabetes may experience gastroparesis, a condition that slows stomach motility. Critically ill patients (sepsis or shock) often have impaired gastrointestinal function as the body diverts resources. Electrolyte abnormalities and hypothermia contribute to a high GRV.
Finally, the method of feeding administration can affect the residual volume. A rapid rate of infusion, especially with bolus feedings, can overwhelm the stomach’s capacity to empty efficiently. The temperature of the formula, particularly colder formulas, can also slow motility and contribute to increased residual volume.
Practical Steps for Managing Elevated Residuals
When a high GRV is measured, especially exceeding the 500-milliliter threshold, the first step is to re-check the residual to confirm the reading, as technique can affect the result. Simultaneously, assess for other signs of intolerance, including abdominal distention, pain, nausea, or vomiting. A high GRV without these accompanying symptoms is less concerning than one that is part of a broader picture of feeding intolerance.
If the elevated reading is confirmed and the patient shows signs of discomfort, the next intervention is typically to temporarily hold the feeding or decrease the infusion rate. It is recommended to return the aspirated fluid to the stomach, as it contains essential nutrients, electrolytes, and digestive enzymes.
Addressing underlying causes is a continuous part of the management strategy. This may involve elevating the head of the bed to at least 30 to 45 degrees to minimize the risk of aspiration, or reviewing the patient’s medications for agents that slow gut motility. In persistent cases, the medical team may administer prokinetic medications (e.g., metoclopramide or erythromycin) designed to stimulate gastrointestinal movement.