Saline Should Be Used for Epidural Procedures, Not Distilled Water
Saline (0.9% sodium chloride) is the appropriate fluid for epidural use, while distilled water is strictly contraindicated due to documented neurotoxicity and severe pain upon injection. 1
Why Distilled Water Must Never Be Used
Distilled water causes severe, instantaneous thoracolumbar pain when injected epidurally, as documented in a case report where accidental epidural injection required immediate treatment with saline and analgesics to resolve the pain. 1
Distilled water is neurotoxic and strictly contraindicated for epidural use, despite historical use as a method to identify the epidural space—experimental data confirm its potential for neurological harm. 1
The hypotonic nature of distilled water (osmolarity near 0 mOsm/L) creates a dangerous osmotic gradient that can damage neural tissue through cellular swelling and lysis. 2, 3
Why Saline Is the Standard of Care
Normal saline (0.9% NaCl) is isotonic (osmolarity ~308 mOsm/L) and safe for epidural use, making it the appropriate choice for loss of resistance technique during epidural placement and for diluting epidural medications. 2, 3
Saline and air show equivalent safety and efficacy in the loss of resistance technique for identifying the epidural space, with no statistically significant differences in inability to locate the space, accidental vascular or subarachnoid placement, or adverse effects like paraesthesias. 4
Saline is used routinely in epidural procedures for obstetric analgesia, postoperative pain management, and chronic pain treatment without evidence of neurotoxicity. 5, 4
Practical Considerations for Saline Use
Use sterile saline pre-packaged in epidural trays or individually wrapped sterile glass ampoules to minimize bacterial contamination risk, as both needle and tray drawing techniques show contamination rates of 11-24% with non-sterile plastic ampoules. 6
Injecting 4-5 mL of normal saline through the epidural needle before catheter threading does not significantly improve ease of catheterization or reduce complications like paraesthesia (27.4% vs 16.0%, P=0.08) or venous cannulation (6.3% vs 11.7%, P=0.30). 7
In neurosurgical or traumatic brain injury patients, maintain isotonicity with 0.9% saline as the first-line crystalloid to prevent cerebral edema, avoiding hypotonic solutions that decrease plasma osmolarity and drive water into brain tissue. 2, 3
Critical Safety Point
If distilled water is accidentally injected epidurally, immediately administer 5-20 mL of 0.9% saline followed by local anesthetic mixture to dilute the hypotonic solution and provide analgesia for the severe pain. 1
The case report demonstrated complete resolution of pain and no neurological deficits at 10-day follow-up after this treatment approach. 1