Traditional teaching as featured prominently throughout educational material has focused on procedure related pain as being indicative of needle-nerve impalement or intraneural injection. By being able to report such pain, the theory is that LA injection will be suspended in response to the patients’ reporting of pain. However, this teaching is supported only by a limited number of case reports (albeit partly because of the medico-legal implications of reporting such cases). 1 In a review of severe chronic pain syndromes following presumed intraneual injections, all eight patients retrospectively reported severe procedure related pain. 2 In two large prospective series, of seven patients who developed nerve related symptoms after block resolution, five had pain associated with the procedure. 3, 4 Finally, in two other case reports of severe block related neuropathies, severe pain was said to have been present during the injection phase of the block procedure. 5, 6 Other prolonged neuropathies have occurred without any significant procedure related pain. 7, 8 Complicating the interpretation of procedure related pain as an indicator of intraneural needle placement/injection is the range of thresholds patients’ have for reporting procedural pain. For example, patients who complain about pain during IV cannula placement and LA infiltration frequently report significant pain during dextrose/LA injection and catheter advancement. Thus, non-block related procedural pain is useful in clinically assessing the significance of reported pain during dextrose/LA injection or catheter advancement.
Because pain on injection does not always occur with intraneural injection, and many patients with block related procedural pain are clearly not undergoing intraneural injection, anesthesiologists are increasingly reappraising the necessity for patient consciousness during these procedures. Regardless, patients who complain of procedure related pain should be suspected of sustaining needle-nerve impalement or intraneural injection.
Interscalene block is often singled out as a block where it is imperative to have patients conscious throughout the procedure. This is because of several case reports of permanent neurological deficit secondary to intracordal LA injection during interscalene block performed under GA. However, such complications are probably related to poor technique rather than performing the block awake vs. under GA per se. Critical is a needle orientation eliminating the possibility of the needle traversing an intervertebral foramen (i.e. orientated caudad and posterior), but more importantly ensuring the needle simply does not encroach on the vertebral column.
Our practice is to whenever possible, perform peripheral blocks in responsive patients. All central neuraxial blocks are performed awake or under light sedation. We can recall several patients who experienced lancinating pain on attempted epidural catheter advancement (i.e. nerve root irritation), which necessitated using a different interspace. If patient anxiety renders performance of a peripheral block in an awake (sedated) patient difficult or impossible, deep sedation or GA is administered. However, certain precautions are followed:
1. Ultrasound needle guidance is used.
2. An 18G Tuohy needle is used (all except distal median/radial/ulnar blocks and the ankle block) – rendering intraneural needle placement very unlikely and intrafascicular placement impossible.
3. For the in-plane technique, both the needle tip and nerve must be visualised such that extraneural LA injection is confirmed.
4. For the out-of-plane technique, the Tuohy needle is orientated as parallel as possible to the target nerve, and concomitant neurostimulation is used to confirm the absence of motor responses < 0.2 mA (pulse width 0.1 ms).
5. LA injection can be performed with minimal injection resistance.
1. Moore DC, Mulroy MF, Thompson GE. Peripheral nerve damage and regional anaesthesia. Br J Anaesth 1994;73:435-6.
2. Kaufman BR, Nystrom E, Nath S, et al. Debilitating chronic pain syndromes after presumed intraneural injections. Pain 2000;85:283-6.
3. Auroy Y, Benhamou D, Bargues L, et al. Major complications of regional anesthesia in France: The SOS Regional Anesthesia Hotline Service. Anesthesiology 2002;97:1274-80.
4. Capdevila X, Pirat P, Bringuier S, et al. Continuous peripheral nerve blocks in hospital wards after orthopedic surgery: a multicenter prospective analysis of the quality of postoperative analgesia and complications in 1,416 patients. Anesthesiology 2005;103:1035-45.
5. Graif M, Seton A, Nerubai J, et al. Sciatic nerve: sonographic evaluation and anatomic-pathologic considerations. Radiology 1991;181:405-8.
6. Fremling MA, Mackinnon SE. Injection injury to the median nerve. Ann Plast Surg 1996;37:561-7.
7. Shah S, Hadzic A, Vloka JD, et al. Neurologic complication after anterior sciatic nerve block. Anesth Analg 2005;100:1515-7, table of contents.
8. Bonner SM, Pridie AK. Sciatic nerve palsy following uneventful sciatic nerve block. Anaesthesia 1997;52:1205-7.