Fasting Before Hepatic SBRT
For hepatic stereotactic body radiotherapy (SBRT), patients should fast for no more than 6 hours for solid foods and may consume clear liquids up to 2 hours before each treatment session.
Standard Fasting Protocol for Hepatic SBRT
The fasting requirements for hepatic SBRT should follow established perioperative guidelines for liver procedures, as there are no specific SBRT-unique fasting protocols in the literature:
- Solid foods: Maximum 6-hour fast before treatment 1
- Clear liquids: May be consumed up to 2 hours before treatment 1, 2
- Light meals (toast, clear liquids): Require 6-hour fasting period 1
- Fatty or fried foods: Require 8 hours or more of fasting if consumed 1
Clear Liquid Definition
Clear liquids that are permitted up to 2 hours before treatment include 2:
- Water
- Fruit juice without pulp
- Carbonated beverages
- Clear tea
- Black coffee (without milk, cream, or sugar)
- Carbohydrate-rich drinks
Rationale for Limited Fasting
Prolonged fasting beyond 6 hours for solids is unnecessary and potentially harmful 1. The evidence supporting shorter fasting periods includes:
- Clear liquids empty from the stomach within 60-90 minutes 3
- Preoperative carbohydrate loading 2 hours before procedures reduces perioperative insulin resistance, malaise, hunger, thirst, nausea, and anxiety without increasing aspiration risk 1
- Meta-analyses demonstrate that 2-4 hour fasting for clear liquids results in smaller gastric volumes and higher gastric pH compared to prolonged fasting 2
Important Clinical Considerations
High-Risk Populations Requiring Modified Protocols
Certain patients may require individualized fasting adjustments 1, 2:
- Diabetic patients: At high risk of severe hypoglycemia during extended fasting and should not fast without close medical supervision 2
- Patients with gastroesophageal reflux disease or delayed gastric emptying: May require longer fasting periods than standard recommendations 2, 3
- Patients with Child class C cirrhosis: Should not undergo prolonged fasting due to risk of encephalopathy, ascites, and metabolic decompensation 2
Medication Management During Fasting
- Oral medications should be rescheduled to non-fasting periods when possible 2
- Essential oral medications may be taken with approximately 240 mL of water up to 2 hours before treatment without breaking the fast 2
- Non-oral medications (parenteral, suppositories, inhalers) are permitted during fasting periods 2
Common Pitfalls to Avoid
- Excessive fasting: Fasting longer than 8 hours may induce hypoglycemia, particularly in vulnerable populations, and can cause metabolic stress that significantly alters physiologic parameters 2, 4
- Inadequate hydration: Patients should maintain adequate hydration with at least 500 mL of water in the 12 hours before treatment 1
- Confusion about clear liquids: Beverages with milk or cream are NOT clear liquids and require the full 6-hour fasting period 2, 3