NPO Requirements for Nuclear Medicine Stress Perfusion Scans of the Heart
Patients do not need to be NPO (nothing by mouth), including clear liquids, before a nuclear medicine stress perfusion scan of the heart. However, certain dietary restrictions are recommended to ensure optimal image quality and diagnostic accuracy.
Recommended Preparation Guidelines
Food Restrictions
- Nondiabetic patients should not consume food or simple carbohydrates for at least 4 hours prior to the FDG PET/CT study 1
- For morning appointments, patients should not eat after midnight and should have only a light meal (no alcohol and minimal carbohydrates) the evening before 1
- For afternoon appointments, patients may have a light breakfast at least 4 hours prior to the scheduled examination time 1
Fluid Intake
- Adequate prehydration is important to ensure a sufficiently low concentration of the radiopharmaceutical in the urine and for radiation safety reasons 1
- Consumption of approximately 1 liter of plain water during the 2 hours prior to injection is recommended 1
- Coffee or caffeinated beverages are not recommended as they may contain traces of simple carbohydrates and have excitant effects 1
Medication Considerations
- Regular medications can be taken as prescribed 1
- Parenteral nutrition and intravenous fluids containing glucose should be discontinued at least 4 hours before the radiopharmaceutical injection 1
- Any intravenous prehydration must not contain glucose 1
Protocol-Specific Considerations
Exercise vs. Pharmacological Stress Testing
- For exercise stress testing, patients should avoid strenuous exercise for at least 6 hours before the study, and preferably for 24 hours 1
- For pharmacological stress testing using vasodilator agents (adenosine, dipyridamole, regadenoson), there are no additional specific NPO requirements beyond the general guidelines 1
Imaging Agents and Protocols
- Different protocols (stress-first vs. rest-first) may be used depending on patient characteristics and clinical scenarios 1
- The choice between stress-first and rest-first protocols balances radiation exposure considerations with the need for diagnostic quality images 1
- For larger patients (>250 lbs or BMI >35) or females with significant breast attenuation, a 2-day protocol with higher radiopharmaceutical activities may be preferable 1
Patient Comfort and Image Quality Considerations
- The patient should void immediately prior to the examination to reduce bladder activity 1
- Patients should be kept warm starting 30-60 minutes before injection and throughout the uptake period to minimize radiopharmaceutical accumulation in brown fat 1
- During injection and the subsequent uptake phase, the patient should remain seated or recumbent and silent to minimize uptake in muscles 1
Special Populations
- For diabetic patients, specific protocols may be needed to manage blood glucose levels before the scan
- For breastfeeding mothers, the ICRP does not recommend interruption of breastfeeding after FDG administration, but suggests limiting contact between mother and child for 12 hours after injection 1
By following these preparation guidelines, optimal image quality can be achieved while ensuring patient comfort and safety during nuclear medicine stress perfusion scans of the heart.