NPO Duration Before Elective CABG
For elective CABG, patients may safely consume clear liquids until 2-4 hours before anesthesia induction and light meals until 6 hours before surgery, rather than the traditional midnight fasting requirement. 1
Evidence-Based Fasting Guidelines
Clear Liquids
- Clear, nonalcoholic fluids can be continued up to 2-4 hours preoperatively without increasing aspiration risk 1
- This recommendation is supported by multiple randomized trials demonstrating safety in cardiac surgery populations 1
- A small cardiac surgery-specific study confirmed that oral carbohydrate drinks consumed 2 hours preoperatively were safe with no aspiration incidents 1
Solid Foods
- Light meals may be consumed up to 6 hours before anesthesia induction 1
- After full meals (including meat, fatty, or fried foods), 8 or more hours fasting is required 1
Traditional vs. Evidence-Based Practice
The traditional "NPO after midnight" approach mandates 6-8 hours fasting from solid meals, but this unnecessarily prolongs the fasting period for most patients 1. The Enhanced Recovery After Surgery (ERAS) Society guidelines specifically challenge this outdated practice, noting that prolonged fasting causes:
- Preoperative dehydration 1
- Electrolyte abnormalities 1
- Patient dissatisfaction and increased anxiety 1
- Interrupted sleep the night before surgery 1
Special Considerations and Caveats
High-Risk Populations
- Patients with diabetes mellitus may have delayed gastric emptying, potentially increasing aspiration risk 1
- Transesophageal echocardiography use during surgery may increase aspiration risk 1
- In these populations, consider more conservative fasting times despite the general evidence supporting shorter NPO periods 1
Carbohydrate Loading
- A 12-ounce clear carbohydrate beverage (24g complex carbohydrate) 2 hours preoperatively may reduce insulin resistance and improve postoperative glucose control 1
- However, this carries only a weak recommendation (Class IIb) for cardiac surgery specifically, as large trials in CABG populations are lacking 1
Strength of Evidence
The recommendation for shortened NPO times is classified as Class IIb, Level C-LD by the ERAS Society 1, indicating:
- The evidence is extrapolated primarily from noncardiac surgery populations 1
- Large-scale studies specifically in cardiac surgery patients are still needed 1
- The recommendation represents moderate-quality evidence with expert consensus 1
Despite the moderate evidence level, the safety profile demonstrated across multiple trials and the clear patient benefits support adopting these liberalized fasting guidelines for most elective CABG patients 1.