Intra-neural injections during performance of PNB s

Intra-neural injections during performance of PNB s Zbigniew Koscielniak-Nielsen, MD, PhD, FRCA. Case reports Controversies Human studies Animal studies Pathophysiology Morbidity studies Conclusions ESRA Winter week, Grindelwald, 23-28 January 2011 Univ. Dept. of Anaesthesiology Rigshospital, Copenhagen, DK

Benumof JL. Anesthesiology 2000; 93: 1541-4. Permanent loss of cervical spinal cord function after interscalene block performed under GA (4 pt s with intramedullary LA injections) * 50 mm stimulating needle inserted at C 6 * Rapid signs of total spinal anesthesia * Medullary syrinx on NMR scans

Kaufman et al. Pain 2000; 85: 283-6. Debiliating chronic pain syndromes after presumed intraneural injections Brachial pl. blocks in 7 awake patients Excruciating pain and paresthesias experienced by all patients during LA injections Recommendations: Avoid mechanical paresthesia Instruct pt. to report pain Do not sedate pt. heavily Do not re-block the nerves Univ. Dept. of Anaesthesiology Rigshospital,Copenhagen, DK

Sala-Blanch et al. Anesthesiology 2004; 101: 1027-30. Intra-neural injection during anterior sciatic n. block 75 year old IDDM patient. Min. stim. current 0.3 ma, 0.3 ms, 20 ml 1.5% MEPA. No discomfort, good block, normal recovery.

Paresthesiae vs. Motor response Interscalene block Urmey et al. Anesthesiology 2002: 96: 552-4. All patients had easily elicited paresthesie, but only 30% of patients exhibited motor response to stimulation current up to 1 ma. Karaca et al. Reg Anesth Pain Med 2003: 28: 380-3. Uncomfortable paresthesia is typically absent or not reported, when a low (0.6 ma) stimulating current is used to identify the brachial plexus and the needle is advanced slowly. (sedated patients) Bollini et al. Reg Anesth Pain Med 2003: 28: 384-8. Motor response preceded paresthesia in every patient. This response can be achieved at a small distance from the nerve, whereas mechanical paresthesia requires a more intimate contact. Motor fibers may also be located more superficially and therefore are encountered first.

Paresthesia vs. motor response Sensory and motor axons are largely segregated to different fascicles, which join and divide repeatedly and occupy as little as a quarter of a cross-sectional area of a nerve. It is therefore possible for a needle to enter the nerve without contacting any sensitive neuronal tissue. Sunderland S. Nerve injuries and their repair. Churchill-Livingstone, Edinburgh 1991.

CT or Ultrasound vs. Motor response Popliteal block Rodriguez et al. Reg Anesth Pain Med 2008: 33: 285-90. 3-5 ml of mepivacaine was injected through the stimulating catheter in 45 pts. Nine pts. developed solid block 5 min later. Threshold currents were 0.52 ma (0.4-0.75) and 0.3 ma (0.18-0.55) respectively. In ten more pts. CT scans showed intraneural catheter position in 3 and 2 other scans were equivocal. None had neurological injury. Sala Blanch et al. Br J Anaesth 2009: 102: 855-61. 40 ml of mepivacaine was injected at threshold currents < 0.5 ma in 42 pts. Nerve diameter was measured with US before and after the injection. Nerve swelling with fascicular separation was seen in 37 pts. (88%). None had neurological injury. Robards et al. Anesth Analg 2009: 109: 673-7. 30-40 ml of LA was injected at threshold currents 0.2-0.5 ma or upon obtaining clear image of intraneural needle location in 24 pts. In 4 pts. no twitch appeared despite increasing amplitude to 1.5 ma. Nerve swelling was observed in all patients. All blocks were succesful. None had neurological injury.

Chan VWS et al. Anesth Analg 2007;104(5):1281-4 Intraneural electrical stimulation and ultrasound detection of intraneural injection in pigs A study of 28 exposed brachial plexus nerves with 22 g stimulating needle inserted 2 cm intraneurally The minimum current to elicit a twitch was 0.43 ma (range 0.02-5.0) Ultrasound visualized increase in the diameter of 24 nerves after LA injection Histology revealed that 22 of these injections were extrafascicular (within the epineurium) and 2 intrafascicular (disrupting the perineurium) Ultrasound is a useful technique to detect intraneural LA inj. but can not differentiate intra- and extrafascicular injections Zkn 10

Pressure (psi) Hadzic A et al. Combination of intraneural needle placement and high injection pressure causes fascicular injury and neurologic deficits. RAPM 2004;29:417-23. 45 40 35 30 25 20 15 10 5 0 Intraneural Injections High pressure injections Intra-fascicular Neurologic injury >20 psi(1040 mmhg) Low pressure injections Extra-fascicular Dense, long acting block <12 psi(620 mmhg) 1 12 23 34 45 56 67 78 89 Time (sec) dog1 dog2 dog3 dog4 dog5 dog6 dog7

Number of occurrences (lasting >1sec) Claudio R et al. Reg Anesth Pain Med 2004;29:201-5. Injection Pressures Generated by Anesthesiologists (n=30) During Simulation of Interscalene Brachial Plexus Block Injection 250 200 150 100 50 0 1-1.9 2-3.9 4-5.9 6-7.9 8-9.9 10-11.9 12-13.9 14-15.9 16-17.9 18-19.9 20-24.9 25-29.9 >30 Pressure Ranges (psi) The syringe-feel method of assessing injection force is inconsistent and may be affected by variability in needle design.

Future? (Courtesy of Dr. Hadzič) Inj. Pressure monitoring To avoid pressure > 20 psi

10.8 + 2.9 kω 18.2 + 6.1 kω El. Imp. could be a quantifiable warning signal of intraneural needle placement

Problems in learning US-guided blocks Error 1 (43.7%) = needle not visualized while being advanced. Error 2 (11.6%) = inadequate equipment preparation. Error 3 (4.7%) = neural target malpositioned on ultrasound screen. Error 4 (26.9%) = unintentional probe movement. Error 5 (3.5%) = awkward needle holding. Error 6 (1.7%) = watching hands instead of ultrasound image. Error 7 (7.8%) = poor ergonomics. Sites B et al. Characterizing novice behavious associated with learning ultrasound-guided peripheral regional anesthesia. RAPM 2007;32:107-115.

None had neurological injury.

Causes of nerve damage - direct needle trauma - intra-neural injection - neuronal ischaemia * vasoconstrictors, haematoma, oedema - drug error - intra OP factors * tourniquet, traction, positioning

NERVE LESIONS (acc. to Seddon) Neuropraxia (functional damage) - intact axons, impaired conduction - complete recovery in days or weeks - no surgical interventions are necessary Axonotmesis (partial disruption) - axonal degeneration, intact supportive structures - spontaneous recovery slow and often partial - distal lesions and younger pt. fare better Neurotmesis (total disruption) - transsection of sheaths and axons - recovery improbable, often sprouting/neuromas - microsurgery/neurolysis is often the best option Univ. Dept. of Anaesthesiology Rigshospital,Copenhagen, DK

Fanelli G et al. Anesth Analg 1999;88:847-52. Nerve Stimulator and Multiple Injection Technique for Upper and Lower Limb Blockade A prospective study of 3996 patients. (2175 sciatic-femoral, 1650 axillary, 171 interscalene) 69 pt s (1.7%) had neurological sequele in the operated limb * Complete recovery within 12 weeks in all but one pt. - 25 weeks * The only predictor of sequele was tourniquet pressure > 400 mmhg * MIT was not associated with > rate of neurologic complications * Sedation/analgesia should be advocated during block placement

Candido KD et al. Anesth Analg 2005;100:1489-95 Neurologic sequelae after interscalene brachial plexus block in 660 subjects: The association of Patient, Anesthetic and Surgical factors 58 sequele (8.8%) were reported by 56 patients * Complete recovery within 4 weeks in all but 2 patients -10, 26 weeks * 31 sequele in 29 patients (4.7%) were likely associated to IS block * 27 sequele (4.1%) were not likely associated to IS block (surgery) Paresthesia/pain/bruising were anesthetic risk factors

Short term neuropathies after brachial plexus blocks (pain, paresthesie, numbness - up to 4 weeks post-op.) Authors Journal Pt.no. Ax SC IS Incidence % Ax SC IS Moberg & Dhunér Wooley & Vandam De Jong Brand & Papper Hammelberg et al. Moore et al. Selander et al. Schmidt et al. Plevak et al. Winchell & Wolfe Tourtier et al. Hartung et al. Davis et al. Weeks et al. Urban & Urquhart Stan et al. Cooper et al Meurice et al. Horlocker et al. Fanelli et al. Borgeat et al. Borgeat et al. Bergman et al. Candido et al. Ben-David et al. Fredericton et al. Liu et al. Liu et al. J Bone Joint Surg 1951 Ann Surg 1959 Anesthesiology 1961 Anesthesiology 1961 Anesth Analg 1962 Anesth Analg 1978 Acta Anesth Scand 1979 Anësth Int Nötfall 1981 Anesthesiology 1983 Reg Anesth 1985 Anesthesiology 1989 Anæsthesist 1989 Mayo Clin Proc 1991 Br J Hand Surg 1994 Reg Anesth 1994 Reg Anesth 1995 Reg Anesth 1995 Reg An Pain Med 1998 Anesth Analg 1999 Anesth Analg 1999 Anesthesiology 2001 Anesthesiology 2003 Anesth Analg 2003 Anesth Analg 2005 Pain Practice 2006 Anesthesia 2009 Anesth Analg 2009 Anesth Analg 2010 28 publications 300 106 94 246 230 250 652 533 342 477 854 758 178 530 751 43 242 266 1000 1149 1324 1614 1650 171 521 700 368 693 336 32 659 219 654 515 17267 pt. 5.7 7.5 1.1 0.8 2.2 1.2 0.0 1.9 0.9 2.9 0.4 0.9 11.0 0.0 10.9 16.3 19.0 9.0 0.2 11.0 23.0 8.4 1.0 4.1 14.0 2.4 0.2 4.6 4.2 3.0 1.4 6.5 0.4 0.4 6.1% 2.2% 5.6% Obs! Corrected for group size.

Block type No. of patients Cardiac arrest Resp. failure Neuropathy Death Spinals - 35439 9 2 13 (0.036%) 3 PNB s - 41079 11 (0.027%) Psoas block - 3594 1 2 1 Conclusions: The incidence of serious neurological complications after PNB s is 1:3475 pt. (ca. 0.3 ) NS is not foolproof and a treshold current < 0.5 ma may be too low!

Reg Anesth Pain Med 2009; 34: 534-541. 7156 blocks in 6069 patients were followed. 30 patients (0.5%) had post-op neuropraxias and were referred to neurological assessment. 3 of them (0.5 ) had a block-related injury. Conclusions: Serious neurological complications after PNB s are uncommon and mostly unrelated to nerve blockade.

Reg Anesth Pain Med 2009; 34: 534-541. 1:5000

11 years 65.092 PNB s Anesth Analg 2007; 104: 965-74.

Surgical complications Positioning Lithotomy position > 2 h 1.5% (Obt., LCF, Sciatic, Peroneus) (1) Retractors, distension Total Hip Arthroplasty 1.2% (2) Ankle arthroscopy - 17% (3) Tourniquet Permanent damage - 0.02% (4) 1. Warner LA et al. Anesthesiology 2000; 93: 938-42. 2. Weale AE et al. J Bone Joint Surg 1996; 78: 889-902. 3. Barber FA et al. Foot Ankle 1990; 10; 263-6. 4. Jankowski CJ. Anesthesiology 2003; 99: 1230-2.

Surgical complications Arthroscopy - 6.9% (1) Rotator cuff repair - 2.6% (2) Glenohumeral instability - 1.1-8.2% (3,4) Shoulder arthroplasty (total) - 4.2% (5) Shoulder arthroplasty (hemi) - 2.8% (5) 1. Segmuller et al. J Sh Elb Surg 1995 2. Zanotti et al. J Sh Elb Surg 1997 3. Mansat et al. Orth Clin N Am 1997 4. Ho et al. J Sh Elb Surg 1999 5. Lynch et al. J Sh Elb Surg 1996

Conclusions! Intraneural injections are probably very common during PNB s. None of the nerve localization methods prevents them. Very few may result in neuropraxias, which recover spontaneously within few days or weeks. Long-lasting nerve injuries attributable to PNB s are very rare (0.2-0.5 ) Nonetheless!!! Register block details (visibility, current, paresthesie, pain, resistance, aspiration) and the operation (positioning, tourniquet, traction). Always follow the patient and demand a detailed neurophysiological assessment. Don t try to answer the question - Who s done it?

Obs! Never inject into spinal roots