Authors: Kent A et al.
Cureus 17(11): e95952, November 2025. DOI: 10.7759/cureus.95952
This report presents a novel, practical technique to safely refill an empty intrathecal pump—an essential device used for delivering intrathecal opioids or baclofen in patients with chronic pain or spasticity. When the reservoir runs dry, the absence of residual fluid eliminates the usual confirmation method for needle placement, increasing the risk of “pocket fill,” a dangerous complication in which medication is inadvertently injected into the subcutaneous tissue rather than the reservoir.
The described case involved a 79-year-old man with a Medtronic SynchroMed™ II pump for hydromorphone delivery that had remained empty for two months. To confirm safe needle placement without residual fluid, clinicians inserted two needles into the pump’s fill port simultaneously, connecting each to a syringe to create a closed system. Injection of hydromorphone through the first needle produced immediate fluid backflow into the second syringe, confirming correct entry into the reservoir due to pressure generated by the pump’s inert gas propellant. Once confirmed, the refill proceeded safely, restoring intrathecal delivery without complications.
The authors explain the underlying physics using the Hagen–Poiseuille principle: reservoir pressure (155–261 mmHg) easily exceeds resistance across a 22–24 G needle, enabling visible backflow through the second needle. They emphasize that this “two-needle approach” offers real-time verification—something not achievable with ultrasound alone or with post-refill volume sensor checks. The method has since been used in six additional cases with consistent success and no adverse events.
What You Should Know:
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Empty pump reservoirs eliminate traditional confirmation methods for needle placement, heightening the risk of accidental subcutaneous injection.
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The two-needle technique uses reservoir pressure to visually confirm correct placement before drug infusion.
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This simple, low-cost approach can be performed under sterile technique without fluoroscopy, CT, or advanced imaging.
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It may serve as a valuable option when imaging resources or sensor-equipped pumps are unavailable.
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Further prospective studies are warranted to validate reproducibility and long-term safety.
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