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Hyperbaric dye solution distribution characteristics after pencil-point needle injection in a spinal cord model
S J Holman1, R A Robinson, D Beardsley
1Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.
Anesthesiology
|April 1, 1997
Summary
To minimize intrathecal maldistribution of hyperbaric lidocaine and reduce the risk of cauda equina syndrome, use injection rates of 6 ml/min or higher. Faster injection rates with larger needles reduce dye concentration in the sacral area.
Area of Science:
- Anesthesiology
- Neurosurgery
- Pharmacology
Background:
- Hyperbaric 5% lidocaine intrathecal maldistribution, linked to flow-rate limiting and directional characteristics of microcatheters, may have caused cauda equina syndrome.
- This study investigates hyperbaric dye distribution via caudally directed side port needles in a spinal cord model to assess maldistribution potential.
Purpose of the Study:
- To evaluate the impact of injection rates on the distribution of hyperbaric dye solutions.
- To determine optimal injection parameters for minimizing intrathecal maldistribution with side port needles.
Main Methods:
- A transparent spinal canal model filled with simulated cerebrospinal fluid was used.
- Hyperbaric phthalocyanine blue dye was injected via side port needles (Sprotte, Whitacre) at varying rates (2-16 ml/min).
- Digital video image processing quantified dye distribution and concentration.
Main Results:
- Injection rate significantly affected peak dye concentration (P < 0.0001) for all needles.
- Rates ≥ 6 ml/min yielded peak dye concentrations below 168 mg/L, indicating reduced maldistribution potential.
- The 24-gauge Sprotte needle showed lower peak concentrations than smaller Whitacre needles (P < 0.05).
Conclusions:
- Injection rates of 6 ml/min or higher minimize sacral maldistribution for tested side port needles.
- At slow rates (2 ml/min), dye concentration varied inversely with needle diameter and orifice area.
