NerveGuard - Automatic Injection Pressure Limiter

Avoiding nerve damage during peripheral nerve blocks
Ultrasound-guided localisation of peripheral nerves provide crucial benefits in regional anaesthesia.(1) Nonetheless, it is clear that one such benefit is not the reduction of the incidence of permanent nerve damage.(2) Even in combination with nerve stimulation, intrafascicular injections cannot be ruled out.(1,3,4,5) With the automatic injection pressure limiter NerveGuard®, PAJUNK introduces a preventive position control to avert damage due to Intrafascicular injection, Cannula-nerve contact and blockage of Cannula opening by contact with fascia.


Nerve damage: Intrafascicular injection

The higher the injection pressure during injections in the intrafascicular space, the more severe and long-lasting the resultant paresis.(6)
If the pressure during intrafascicular injections exceeds a critical threshold of 15 psi, such injections may demonstrably lead to severe long-term neurological complications. (6,7,8) (Kapur(6): > 20psi, Hadzic(7):
> 25psi, Hasanbegovic(8): > 15.9psi
Effects: In the case of long duration (several hours) intrafascicular injections at high pressure, the microvascular blood supply of the nerve is severely restricted, which can lead to degeneration of nerve structures. (7,12)

Limiting the injection pressure to 15psi avoids nerve damage associated with Intrafascicular injection.


Nerve damage: Cannula-Nerve contact

Direct cannula-nerve contact can also lead to damage of the neural structures with subsequent transient or permanent neurological impairment. (10,11) Localisation control using ultrasound and/or nerve stimulation may not in all cases reliably indicate direct cannula-nerve contact.
Further, Paresthesia in and of itself is not regularly observed. (10)
Avoiding direct cannula-nerve contact minimises the risk of damage to the nerve wall. (11)

A reliable indicator of direct cannula-nerve contact is an opening pressure of ≥ 15psi.


Cannula-fascia contact

Injections administered inadvertantly in errant tissue layers can also cause anaesthesia failures.  An opening pressure of ≥ 15psi may indicate occlusion of the tip of the cannula due to blocking by fascia. (9)

To prevent injections in errant tissue layers close to the nerve, the critical threshold is an opening pressure of 15psi.


Solution - NerveGuard - Automatic injection Pressure Limiter

With NerveGuard attached to syringe and in line with injection hose, syringe injection pressure is limited to a maximum 15psi - at greater pressures, NerveGuard's valve closes and prevents further administration of anesthetic. This action is automatic - no monitoring or visual control is necessary.


Upon corrective retraction and Repositioning of cannula, valve reopens

Left: The tip of the cannula pierces the fascia and is now in the optimal position for an injection.
Right: Avoiding an injection when there is direct cannula-nerve contact minimises the risk of damage to the nerve wall.(11)

Order # 001151-38M, box/10

NerveGuard is compatible with Pajunk needles - SonoPlex, SonoTap & NanoLine in guages 20, 21, 22 for single shot procedures and for 18G and 19G needles while performing Continuous Block.

1. Choquet O., Capdevila X. Ultrasound-guided nerve blocks: the real position of the needle should be defined, Anaesth. Analg. 2012 May; 114(5): 929–930

2. Neil J. M., Brull R., Horn J. L., Liu S. S., McCartney C. J., Perlas A., Salinas F. V., Tsui B. C. The Second American Society of Regional Anesthesia and Pain Medicine Evidence-Based Medicine Assessment of Ultrasound-Guided Regional Anesthe- sia, Reg. Anaesth. Pain Med. 2016 March–April; 41(2): 181–194

3. Robards C., Hadzic A., Somasundaram L., Iwata T., Gadsden J., Xu D., Sala-Blanch X. Intraneural injection with low-current stimulation during popliteal sciatic nerve block, Anesth. 2009 Aug; 109(2): 673–677

4. Vassiliou T., Müller H.H., Limberg S., De Andres J., Steinfeldt T., Wiesmann T. Risk evaluation for needle-nerve contact related to electrical nerve stimulation in a porcine model, Acta Anaes- thesiol. Scand. 2016 Mar; 60(3): 400–406

5. Sites B. D., Spence B. C., Gallagher J. D., Wiley C. W., Bertrand M. L., Blike G. T. Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia, Reg. Anesth. Pain Med. 2007 Mar–Apr; 32(2): 107–115

6. Kapur E., Vuckovic I., Dilberovic F., Zaciragic A., Cosovic E., Divanovic K.A., Mornjakovic Z., Babic M., Borgeat A.,Thys D.M., Hadzic A. Neurologic and histologic outcome after intraneural injections of lidocaine in canine sciatic nerves, Acta. Anaesthesiol. Scand. 2007 Jan; 51(1): 101–107

7. Hadzic A., Dilberovic F., Shah S., Kulenovic A., Kapur E., Zaciragic A., Cosovic E., Vuckovic I., Divanovic K.A., Mornjakovic Z., Thys D.M., Santos A.C. Combination of intraneural injection and high injection pressure leads to fascicular injury and neurologic deficits in dogs, Reg. Anesth. Pain Med. 2004 September–October; 29(5): 417–423

8. Hasanbegovic I., Kulenovic A., Hasanovic S. Effects of in- traneural and perineural injection and concentration of ropivacaine on nerve injury during peripheral nerve block in wistar rats, J. of Health Sciences 2013; 3(3): 243–249

9. Gadsden J., Latmore M., Levine D.M., Robinson A. High Opening Injection Pressure is Associated With Needle-Nerve and Needle-Fascia Contact During Femoral Nerve Block, Reg. Anesth. Pain Med. 2016 Jan–Feb; 41(1): 50–55

10. Gadsden J., Choi J.J., Lin E., Robinson A. Opening injection pressure consistently detects needle-nerve contact during ultrasound-guided interscalene brachial plexus block, Anesthesiology 2014 May; 120(5): 1246–1253

11. Steinfeldt T., Graf J., Schneider J., Nimphius W., Weihe E., Borgeat A., Wulf H., Wiesmann T. Histological consequences of needle-nerve contact following nerve stimulation in a pig model, Anesth. Research and Practice 2011; Article ID 591851: 0–9

12. Lundborg G., Myers R., Powell, H. Nerve compression injury and increased endoneurial fluid pressure: a „miniature compartment syndrome“, J. Neurol. Neurosurg. Psychiatry 1983 Dec; 46(12): 1119–1124