Combination of intraneural injection and high injection pressure leads to fascicular injury and neurologic deficits in dogs.
ABSTRACT Unintentional intraneural injection of local anesthetics may cause mechanical injury and pressure ischemia of the nerve fascicles. One study in small animals showed that intraneural injection may be associated with higher injection pressures. However, the pressure heralding an intraneural injection and the clinical consequences of such injections remain controversial. Our hypothesis is that an intraneural injection is associated with higher pressures and an increase in the risk of neurologic injury as compared with perineural injection.
Seven dogs of mixed breed (15-18 kg) were studied. After general endotracheal anesthesia, the sciatic nerves were exposed bilaterally. Under direct microscopic guidance, a 25-gauge needle was placed either perineurally (into the epineurium) or intraneurally (within the perineurium), and 4 mL of lidocaine 2% (1:250,000 epinephrine) was injected by using an automated infusion pump (4 mL/min). Injection pressure data were acquired by using an in-line manometer coupled to a computer via an analog digital conversion board. After injection, the animals were awakened and subjected to serial neurologic examinations. On the 7th day, the dogs were killed, the sciatic nerves were excised, and histologic examination was performed by pathologists blinded to the purpose of the study.
Whereas all perineural injections resulted in pressures < or =4 psi, the majority of intraneural injections were associated with high pressures (25-45 psi) at the beginning of the injection. Normal motor function returned 3 hours after all injections associated with low injection pressures (< or =11 psi), whereas persistent motor deficits were observed in all 4 animals having high injection pressures (> or =25 psi). Histologic examination showed destruction of neural architecture and degeneration of axons in all 4 sciatic nerves receiving high-pressure injections.
High injection pressures at the onset of injection may indicate an intraneural needle placement and lead to severe fascicular injury and persistent neurologic deficits. If these results are applicable to clinical practice, avoiding excessive injection pressure during nerve block administration may help to reduce the risk of neurologic injury.
- SourceAvailable from: Xavier CapdevilaAnnales Françaises d Anesthésie et de Réanimation 09/2012; 31(9). · 0.84 Impact Factor
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ABSTRACT: Ultrasound gel nerve inflammation has been reported. We evaluated the extent and nature of inflammation after gel injection with endotoxin (positive), saline, or dry needle puncture (negative) controls after peripheral blocks in piglets. Selected nerves of 12 piglets were localized by landmarks and nerve stimulator. Forty-eight hours after injection, specimens were examined for immunohistochemical cell differentiation/quantification and cytokine expression by using quantitative polymerase chain reaction. Both gel and endotoxin injections resulted in a significantly higher density of inflammatory cells (lymphocytes/granulocytes) as compared with needle insertions and/or saline injections (both P < 0.001). Cytokines were not detected in any of the specimens. Perineural gel injections cause significant inflammation. The lack of cytokines suggests injectate-related changes rather than mechanical trauma.Anesthesia and analgesia 04/2014; 118(4):869-73. · 3.42 Impact Factor