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Lignocaine, spinal anaesthesia, and neurological complications

Systematic review
Results
Comment

Spinal anaesthesia has been used now for over a century, and a number of local anaesthetics is available. Increased employment of day case surgery has led to increased use of spinal anaesthesia, especially with rapid onset and short duration of action, allowing patients to go home sooner.

Spinal anaesthesia is associated with relatively low rates of neurological complications, some of which may be severe and permanent. These may be a result of a combination of needle injury, unusual anatomy, and effects of anaesthetic drugs.

Transient neurological symptoms refer to those appearing from a few hours to 24 hours after full recovery from uneventful spinal anaesthesia. They include pain, which can be severe, originating from the gluteal region and radiating to the lower extremities. A systematic review [1] questions whether these symptoms are associated with a particular local anaesthetic, and especially lignocaine (or lidocaine, depending where in the world you are).

Systematic review

This review sought randomised and pseudo-randomised trials appearing as full publications in adults receiving spinal anaesthesia, including pregnant women. The follow up period for transient neurological symptoms had to be at least 24 hours. At least one study arm had to have used lignocaine.

Results

Fifteen studies were included, with 1,439 patients in 18 comparisons, and with information on 1,437 patients. Rates of transient neurological symptoms were consistently higher with lignocaine than with other local anaesthetics, with the possible exception of mepivacaine (Figure 1; Table 1).



Figure 1: Neurological symptoms with lignocaine and other local anaesthetics







Table 1: Results for transient neurological symptoms with individual local anaesthetics



Patients
Drug
Trials
Total
With symptoms
Percent with symptoms
Lidocaine
18
704
97
14.0
Bupivacaine
7
291
3
1.0
Prilocaine
4
217
4
1.8
Mepivacaine
3
100
14
14.0
Procaine
2
65
2
3.1
Ropivacaine
1
30
0
0.0
Levobupivacaine
1
30
0
0.0


The typical description was of bilateral pain in buttocks, thighs, and legs, with visual analogue scores varying from 2 to 9 on a 10 point score. Pan usually disappeared by the second day, and the maximum duration was five days. No patient with transient neurological symptoms was reported to have any permanent neurological sensory or motor deficits.

Overall, 14% of patients given lignocaine had transient neurological symptoms compared with 3.1% with any other local anaesthetic, giving a number needed to harm of 9 (95% CI 7 to 13).

Comment

Anaesthetists may want to look at these data much more closely. There is considerable clinical heterogeneity between the trials, in terms of patients, their position during operation, the size and cut of the needles used, the placing of the anaesthetic, whether it was hyperbaric, the strength of the local anaesthetic, to name just some of the issues they will have. Definition of symptoms may be another. Whether any of these points turns out to be crucial is another matter, but people have looked at some of them, and found, for instance, that the incidence of neurological symptoms did not vary with lignocaine concentration.

Moreover, however you look at these data, there are issues of trial quality (most were open) and the lack of numbers, and the reasons for the large spread of results with lignocaine, from 0 to over 30%. This suggests either some technical issue, or some quality issue of trial reporting that this review did not explain.

We must also remember that significant and long lasting neurological damage after spinal anaesthesia is a very rare event, with lignocaine or any other local anaesthetic. So these adverse events are transient, an important fact. All of which, of course, makes this an interesting learning example, and one that should have legs.

Reference:

  1. D Zaric et al. Transient neurological symptoms (TNS) following spinal anaesthesia with lidocaine versus other local anaesthetics. Cochrane Database of Systematic Reviews 2005 issue 4.

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