Should a 3% hypertonic sodium chloride infusion be continued when a PET‑CT scan is planned?

Should 3% Hypertonic Saline Be Continued During PET-CT Scanning?

Discontinue the 3% hypertonic saline infusion before PET-CT scanning and use only normal saline (0.9% NaCl) for hydration and IV access maintenance during the procedure.

Rationale Based on Guidelines

The EANM procedure guidelines for FDG PET/CT tumor imaging explicitly state that normal saline (NaCl 0.9%) should be used for flushing administration systems and for intravenous hydration during PET-CT procedures 1. The guidelines specifically recommend:

• Flushing with "at least 10 mL of normal saline (NaCl 0.9%) – or solutions without glucose" 1
• If oral hydration is inadequate, "this amount can be given in the form of normal saline intravenously" 1
• No mention of hypertonic saline (3% NaCl) is made in any PET-CT imaging protocol

The most recent EANM/SNMMI guideline for FDG PET use in infection and inflammation (2025) similarly references only normal saline for IV administration, with no provision for hypertonic solutions during imaging 2.

Clinical Context and Safety Considerations

Why This Matters for PET-CT Quality

The primary concern is maintaining optimal imaging conditions:

• PET-CT requires stable physiologic conditions during the 60-minute uptake period and scanning 1
• Hypertonic saline causes significant fluid shifts and hemodynamic changes that could affect tracer distribution
• The guidelines emphasize creating a "stress-free environment" during FDG uptake 1

When 3% NaCl Is Actually Indicated

The evidence shows 3% hypertonic saline is reserved for specific acute conditions 3, 4:

• Severe symptomatic hyponatremia (serum sodium <120-125 mmol/L with neurologic symptoms)
• Acute hyponatremia with seizures or altered mental status requiring rapid correction 4
• The 2021 cirrhosis guidelines state: "Hypertonic sodium chloride (3%) administration should be reserved for those who are severely symptomatic with acute hyponatremia" 3

Practical Algorithm

If patient is on 3% NaCl when PET-CT is ordered:

1. Assess clinical urgency: Is the patient having active seizures, severe neurologic symptoms, or critically elevated intracranial pressure?

2. If clinically stable (most common scenario):

   • Temporarily discontinue 3% NaCl
   • Maintain IV access with 0.9% normal saline
   • Proceed with PET-CT per standard protocol
   • Resume 3% NaCl after imaging if still indicated

3. If critically unstable (rare):

   • Consider delaying PET-CT until patient stabilized
   • If imaging cannot be delayed, discuss with radiology about potential artifacts from ongoing hypertonic infusion

Important Caveats

• The IV line itself can remain in place – guidelines only require it be maintained with normal saline 1
• Research shows 3% NaCl can be safely given peripherally 5, 6, 7, 8, 9, but this is irrelevant to PET-CT protocols which specify normal saline
• Recent research on oral isotonic vs hypotonic solutions for PET-CT found isotonic saline reduced intestinal FDG uptake 10, further supporting use of isotonic rather than hypertonic solutions

Bottom line: Standard PET-CT protocols universally call for normal saline only. There is no evidence supporting continuation of 3% NaCl during imaging, and doing so introduces unnecessary variables that could compromise image quality without clear benefit to the patient during the brief imaging period.