What is the preferred diluent, Normal Saline Solution (NSS) or D5W (5% Dextrose in Water), for epidural steroid/facet block injections in patients with various medical histories, including allergies, kidney disease, diabetes, or glucose intolerance?

Diluent Selection for Epidural Steroid and Facet Block Injections

Normal saline solution (NSS) is the preferred diluent for epidural steroid and facet block injections over D5W, as it provides appropriate volume expansion without introducing glucose that could complicate diabetes management or create unnecessary metabolic concerns. 1, 2

Primary Recommendation

NSS should be used as the standard diluent for these procedures because:

• Epidural steroid injections are routinely performed with normal saline as the diluent, combined with local anesthetic (typically 1% lidocaine) and corticosteroid (such as 60 mg triamcinolone), as documented in clinical practice 1

• Normal saline provides mechanical washout of inflammatory mediators while serving as an appropriate vehicle for medication delivery without adding metabolic complications 3

• D5W is inappropriate for procedures requiring volume expansion or hemodynamic support, as it lacks adequate plasma volume expansion properties and should not be used as a primary resuscitation or injection fluid in clinical scenarios requiring circulatory support 4

Clinical Rationale by Patient Population

Diabetic Patients and Glucose Intolerance

• Avoid D5W in diabetic patients undergoing epidural injections, as any dextrose-containing solution requires blood glucose monitoring every 1-2 hours, and uncontrolled hyperglycemia can worsen clinical outcomes 5, 4

• Normal saline eliminates glucose-related complications that could arise from D5W administration, particularly important given that epidural steroid injections themselves can cause transient hyperglycemia through systemic steroid absorption 6

Patients with Kidney Disease

• Normal saline is appropriate for patients with renal disease in the volumes used for epidural injections (typically 3-6 mL total volume), as this small volume does not pose significant fluid overload risk 1

• Monitor for fluid overload in severe renal compromise, though the small volumes used in epidural/facet injections (3-10 mL total) are unlikely to cause problems even in patients with kidney disease 7

Patients with Allergies

• Normal saline is hypoallergenic and does not introduce additional allergen risk beyond the medications being administered (steroid and local anesthetic) 1, 2

• D5W contains no additional allergens, but offers no advantage over NSS and introduces unnecessary glucose exposure 5

Standard Injection Protocol

The typical epidural steroid injection composition includes:

• Corticosteroid: 60-80 mg triamcinolone or equivalent methylprednisolone 7, 1
• Local anesthetic: 3 mL of 1% lidocaine hydrochloride 1
• Diluent: 3 mL of normal saline 1
• Total volume: 6-9 mL administered in increments under fluoroscopic guidance 1, 2

Critical Considerations

Efficacy Evidence

• Steroids demonstrate superior pain control compared to saline or local anesthetic alone at 1 month (most prominent), 3 months, and 6 months follow-up, with the effect diminishing but remaining significant through 1 year 3

• The mechanical effect of volume injection (whether saline or local anesthetic) contributes to pain relief by washing out inflammatory mediators and blocking nociceptor activity, independent of steroid effect 3

Safety Profile

• Epidural injections carry inherent risks including infection (including fatal fungal meningitis from contaminated preparations), spinal fluid leaks (0.4-6%), adhesive arachnoiditis (6-16%), intravascular injection (7.9-11.6%), and neurological complications 8

• The choice of diluent (NSS vs D5W) does not significantly impact these complication rates, as the risks are primarily related to the injection technique, steroid preparation contamination, and anatomical factors 8, 6

Contraindications to D5W

• D5W should never be used in hypotensive patients requiring any degree of hemodynamic support, as it provides inadequate plasma volume expansion 4

• Avoid D5W in patients with hypernatremia when hemodynamic stability is threatened, as isotonic saline takes priority for volume resuscitation 4

Practical Algorithm

For all epidural steroid and facet block injections:

1. Use normal saline as standard diluent (3 mL) combined with local anesthetic (3 mL of 1% lidocaine) and corticosteroid (60-80 mg triamcinolone or methylprednisolone) 1, 2

2. In diabetic patients: Confirm normal saline use and monitor blood glucose if systemic steroid absorption is a concern, though local epidural administration minimizes this risk 6

3. In patients with renal disease: Normal saline remains appropriate given small injection volumes (6-9 mL total) 1

4. In patients with multiple comorbidities: Normal saline provides the safest metabolic profile without introducing glucose-related complications 4, 3

Common Pitfalls to Avoid

• Do not use D5W thinking it provides "gentler" osmotic properties - the small volumes used in epidural injections make osmotic differences clinically irrelevant, while D5W introduces unnecessary glucose exposure 5, 4

• Do not delay necessary surgery by performing serial epidural injections (typically administered in series of three) in patients with clear surgical pathology, as this exposes them to injection risks while potentially allowing neurological deterioration 8

• Ensure sterile technique and use only FDA-approved, uncontaminated steroid preparations, as contaminated epidural steroids have caused 25 deaths and sickened 337 patients in documented outbreaks 8