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Chapter 59. Complications and Prevention of Neurologic Injury with Peripheral Nerve Blocks

Which statement is most correct regarding the epidemiology and incidence of nerve injury following peripheral nerve blockade?

A. Epidemiologic studies indicate that extrafascicular intraneural injection of local anesthetic is safe in humans.

B. Postoperative peripheral nerve injury may be due to factors unrelated to peripheral nerve blockade.

C. The incidence of postoperative peripheral nerve injury is well-defined.

D. Regardless of etiology, the incidence and severity of postoperative nerve injury is unchanged as time elapses from the time of injury.

E. Ultrasound imaging is associated with a reduced incidence of nerve injury following peripheral nerve blockade.

B is correct. Several studies over time have demonstrated that causes unrelated to anesthesia technique can be the cause of postoperative nerve injury.1-3

A is incorrect. No large epidemiologic studies support the safety of deliberate intraneural, but extrafascicular injection of local anesthetic. There are small case series with sample sizes insufficient to detect a difference in safety between extrafascicular (intraneural) injection compared to extraneural injection outside of the epineurium (standard practice).4 It is a long-standing safety guideline to avoid trauma to peripheral nerves during peripheral nerve blockade.5

C is incorrect. The incidence of postoperative peripheral nerve injury, following peripheral nerve blockade is poorly defined. This is due to variability in the study methods used to capture nerve injury, investigate potential causes of nerve injury, and define nerve injury.

D is incorrect. The incidence and severity of postoperative nerve injury reduces as time elapses from the time of injury.6 Perhaps, a critical time to assess extent of “final” improvement following a nerve injury is 6 months, although there is still potential for neurologic improvement following this point in time.

E is incorrect. Despite imaging peripheral nerves with ultrasound and controlling the injection of local anesthetic real-time, there is no evidence that ultrasound guidance has reduced the risk of nerve injury. This may relate to the relative infrequency of nerve injury, the lack of definitive prospective studies including both ultrasound-guided and traditional techniques, and the difficulties inherent in using ultrasound-guided techniques to reliably identify nerves across the range of patient morphologies and locations where nerve blocks are performed. Ultrasound-guided techniques are operator-dependent and the resolving power of ultrasound technology is limited.

Which statement is true regarding the etiology of nerve injury following peripheral nerve blockade?

A. Controlled clinical trials indicate that tourniquet compression during surgery on young healthy patients is not an independent risk factor for nerve injury.

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