Dr Sean Tighe
Consultant Anaesthetist
Countess of Chester Hospital Foundation NHS Trust
Sean qualified in 1978 from Guy’s Hospital. He was appointed in 1993 as a Consultant
Anaesthetist at the Countess of Chester Hospital Foundation NHS Trust, with an interest in
Intensive Care and anaesthesia for ophthalmic, plastic, general and orthopaedic surgery. He
established the acute pain service and developed an interest in regional anaesthesia for
ophthalmic, breast, upper and lower limb surgery. He is Treasurer of the European Society
of Regional Anaesthesia UK&I, and committee member and past secretary of the British
Ophthalmic Anaesthesia Society. Formerly Sean was a Consultant Anaesthetist at the Royal
Naval Hospital, Plymouth in the rank of Surgeon Commander, Royal Navy. Sean served in
the Falklands campaign in 1982 and in Northern Iraq in 1991.
ABSTRACT
Complications of Peripheral Nerve Blockade: Incidence and Prevention
The consent process requires that the patient be fully appraised of the risks as well as the
benefits, prior to any invasive procedure, so that they can make a fully informed choice.
Unfortunately, with regard to peripheral nerve blockade, neither the benefits nor the risks
can be objectively quantified with accuracy. The evidence base for complications of
peripheral nerve blocks (PNBs) is particularly poor, relying heavily on case reports,
retrospective surveys and closed claims analysis. There are very few prospective studies.
The incidences quoted below should therefore be viewed with caution as they are a
personal interpretation of the literature and of the author’s limited unpublished case series
of only 890 cases.
1. Pain. >1:10, common (personal data). Mitigated by use of local infiltration with small
quantities of analgesics and sedatives1.
2. Significant haematoma. < 1:10,000? Rare. Minor bruising <1:10 2. Nerve compression and
the need for blood transfusion have been reported 3,4. No deaths. Care should be taken
when large vessels are in close proximity, with lumbar plexus block and with combinations
of anticoagulant drugs3,4. Long bevel needles may cause less bleeding than short bevels.
3. Significant infection. Single shot < 1:10,000. Rare 1. Catheters < 1:1005. Catheters are
very commonly colonized with oral flora 6. A single death has been reported from
necrotizing fasciitis with an axillary catheter7. Full aseptic precautions will minimize
infection.
4. Block-related complications. <1:1 - <1:1 million? Common-very rare. Pneumothorax is
associated with intercostal (<1:108), supraclavicular (<1:1009), interscalene (<1:50010) and
paravertebral blockade (<1:100011). There have been isolated reports of haemothorax after
paravertebral12 and supraclavicular block (<1:100,000 13?). Phrenic nerve paresis is
inevitable with the landmark technique of interscalene block (1:1 14), but this can be
avoided in 55% with ultrasound (< 1:1 14). Paraplegia has resulted from interscalene block (<
1:1 million?15). Horner’s syndrome is often seen in neck and high paravertebral blocks (<
1:1, personal data). Intrathecal or epidural spread was reported in 1 :130 lumbar plexus
blocks16 and can occur with any block near the neuraxis (<1:1000, personal data ). 5% of
ilio-ingunal blocks spread onto the femoral nerve (<1:10 17). Insensate trauma may occur if
the area is not protected. Prevention is by meticulous technique.
5. Local anaesthetic toxicity. < 1:1000 18. Uncommon. Inadvertent intravenous injection
occurs in up to 1:500 cases (personal communication, Selander D). Seizures have been
reported in <1:100018 - <1:800016. The incidence of profound hypotension secondary to
toxicity is unknown, but under GA, it is probably much higher than generally realized
(<1:100, personal data). Cardiac arrest and death was reported in 1:44,000; 1:394 lumbar
plexus blocks16. Myotoxicity is very rare (< 1:100,000?19). The risk of toxicity is minimized
by using the lowest concentration and dose for the desired effect, of drugs with the highest
therapeutic ratio. Initial disconnection and frequent aspiration should be performed. An
epinephrine marker may be of benefit, but risks neurotoxicity (vide infra). A small initial
test dose is recommended, with slow incremental injection over as prolonged a period as
possible. Catheter techniques may assist this process. Ultrasound also has theoretical
advantages20.
6. Temporary neurological symptoms, <1:10 21. Common. Permanent neurological damage;
<1:10,000? Rare.. 1:10 had minor neurological symptoms lasting up to one month 21. For
lesions lasting up to three months, the incidence was < 1:250 (upper limb 10)- < 1:5000 (all
blocks22). At 6 months, the rates were <1:50010 – <1: 700016, respectively. The definition of
permanence is debatable, but may be assumed if it persists >1 year. Further recovery after
6 months can be expected. If this is assumed to be 30%, the overall incidence of
permanent neurological damage at 1 year would be approximately 1:10,000. For upper
limb blocks, particularly interscalene block, the risk may be up to twenty times greater
(<1:50010), although Auroy noted a high rate with popliteal blocks (1:317 16). This compares
with <1:6000 for GA alone (a study of ulnar neuropathy only 23), 1:12,000 for intrathecal16
and 1: 35,000 for epidural block16.
However, a surgical aetiology should always be excluded first, as this is far more common 10.
In upper limb surgery, the incidence of temporary nerve damage was 7 - 8.2% and this was
permanent in 0.7 -3.3% without PNBs24, 25, probably due to stretch, compression and/or
direct surgical trauma. Ulnar neuropathy has been reported in 1:500 medical patients,
recumbent in bed26. The apparently high incidence of neuropathy after upper limb block
may therefore be erroneous.
The mechanism of neurological damage is multifactorial, but a double crush phenomenon
has been suggested27. Penetration of the intrafascicular structure is unlikely to be the sole
factor27. Predisposition and/or injection of neurotoxic local anaesthetic are probably
required in addition27. Great care should therefore be taken in those at risk; diabetics, the
extremes of age and weight, males and atherosclerosis, particularly in combination 27.
Short bevel needles are less likely to penetrate nerves than long bevels, but if they do,
nerve damage is likely to be more extensive28, particularly if insertion is perpendicular to
the direction of the fascicles29. Pencil point needles may be less traumatic30, but have to
be placed closer to the nerve. There is no evidence that the location technique has any
influence on the incidence of nerve injury21,27 but ultrasound has theoretical, unproven
advantages20.
Animal studies have correlated nerve injury with high injection pressures 31, indicating the
poor compliance of intrafascicular structures. High pressure injection should be strictly
avoided.
Intrafascicular local anaesthetics are neurotoxic, in proportion to concentration 32. Esters
are worse than amides and adrenaline increases toxicity 32. The lowest dose and
concentration, without epinephrine, should be used to minimize neuropathy, particularly in
high risk patients. Patients should be carefully positioned to avoid compression or stretch,
even if they are conscious.
There is no evidence that the incidence of neuropathy is increased when PNBs are
established in anaesthetized or heavily sedated patients27. Despite this, ASRA (USA) has
recommended that PNB’s should usually be performed in awake patients, except in
paediatrics and when the risk benefit ratio is clearly in favour of doing otherwise 27.
Interscalene block is specifically mentioned in this respect27. Meticulous technique and
training are the most important factors in the prevention of nerve injury and all other
complications of PNBs.
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CONTACT DETAILS:
Sean Q M Tighe, Consultant Anaesthetist
Countess of Chester Hospital Foundation NHS Trust
Liverpool Rd, Chester, CH2 1 UL
Email: sean.tighe@coch.nhs.uk