Pressure Monitoring of Intraneural an Perineural Injections Into the Median, Radial, and Ulnar Nerves; Lessons From a Cadaveric Study

Abstract

Background:Nerve damage after regional anesthesia has been of great concern to anesthetists. Various modalities have been suggested to recognize and prevent its incidence. An understudied area is the measurement of intraneural pressure during peripheral nerve blockade. Previous investigations have produced contradicting results with only one study being conducted on human cadavers.Objectives:The purpose of this investigation was to systematically record intraneural and perineural injection pressures on the median, ulnar, and radial nerves exclusively as a primary outcome.Materials and Methods:Ultrasonography-guided injections of 1 mL of 0.9% NaCl over ten seconds were performed on phenol glycerine embalmed cadaveric median, ulnar, and radial nerves. A total of 60 injections were performed, 30 intraneural and 30 perineural injections. The injections pressure was measured using a controlled disc stimulation device. Anatomic dissection was used to confirm needle placement.Results:Intraneural needle placement produced significantly greater pressures than perineural injections did. The mean generated pressures in median, radial, and ulnar nerves were respectively 29.4 ± 9.3, 27.3 ± 8.5, and 17.9 ± 7.0 pound per square inch (psi) (1 psi = 51.7 mmHg) for the intraneural injections and respectively 7.2 ± 2.5, 8.3 ± 2.5, and 6.7 ± 1.8 psi for perineural injections. Additionally the intraneural injection pressures of the ulnar nerve were lower than those of the median and radial nerves.Conclusions:Obtained results demonstrate significant differences between intraneural and perineural injection pressures in the median, ulnar, and radial nerves. Intraneural injection pressures show low specificity but high sensitivity suggesting that pressure monitoring might be a valuable tool in improving the safety and efficacy of peripheral nerve blockade in regional anesthesia. Peripheral nerves “pressure mapping” hypothetically might show difference amongst various nerves depending on anatomic location, histologic structure, and ultrasonographic appearance.

Opening Injection Pressure Is Higher in Intraneural Compared With Perineural Injections During Simulated Nerve Blocks of the Lower Limb in Fresh Human Cadavers

“…Similar to recent findings by other investigators, none of the perineural injections resulted in OIPs greater than 15 psi, suggesting that this commonly used threshold for injection pressure may be applicable to lowerextremity nerve blocks as well. 18,19 An interesting finding was that the rate of rise of OIP after beginning the injection process was 3 to 5 times higher for intraneural than for perineural injections. Previous investigators have not reported the rate of rise of injection pressure, although several reports detailed the injection pressure curves for intraneural, perineural, and intrafascicular injections.…”

The ability of a real‐time injection pressure monitoring system to discriminate between perineural and intraneural injection of the sciatic nerve in fresh cadavers

“…Measurement of injection pressure is considered to be a pivotal element in the detection of intraneural placement of a peripheral nerve block needle in order to reduce the risk of nerve damage . However, all previous studies in animal models , cadavers or human subjects have measured pressure along the injection line. These measurements are affected by speed of injection and the dimensions of the needle and connection tubing , which make their usefulness in clinical practice uncertain.…”

“…Gadsden et al have shown that injection pressures > 103 kPa may indicate needle‐nerve or needle‐fascia contact during interscalene and femoral nerve blocks . Krol et al demonstrated differences between perineural and intraneural injection pressures in the median, ulnar and radial nerves in cadavers . This suggests that injection pressure at the needle tip varies according to nerve micro‐anatomy and physical characteristics of the tissue.…”

Neurotoxicity of perineural vs intraneural–extrafascicular injection of liposomal bupivacaine in the porcine model of sciatic nerve block

“…To decrease the risk of intrafascicular injection and to prevent needle‐nerve trauma with consequent inflammatory reaction , injection pressure monitoring and electrical nerve stimulation were employed. If, during needle insertion, an evoked motor response was elicited at < 0.3 mA or injection could not commence with injection pressure < 104 kPa , the injection was re‐attempted after the needle was repositioned.…”