March 29, 2001

Cauda Equina Syndrome After Spinal Anesthesia with Hyperbaric 5% Lignocaine: A Review of the Six Cases of Cauda Equina Syndrome Reported to the Swedish Pharmaceutical Insurance 1993-1997

Loo CC, Irestedt L. Acta Anaesthesiol Scand 1999;43:371-379

Commentary by Kathryn McGoldrick, M.D.

Ever since August Bier pioneered spinal anesthesia in 1898, the safety of drugs administered intrathecally has been debated vigorously. Although uncommon, neurological complications after spinal anesthesia can be devastating. These can include such serious entities as spinal cord ischemia, arachnoiditis, and cauda equina syndrome (CES). CES is characterized by varying degrees of saddle anesthesia, sphincter dysfunction resulting in bowel or urinary problems, and paraplegia.

Auroy and colleagues, [1] after a prospective survey of 40,640 spinal anesthetics administered in France in 1994, found five cases of CES as a result of spinal anesthesia (1 in 8,128 blocks). During the past decade there has been particular concern about the potential direct neurotoxicity of hyperbaric 5% lidocaine and its possible role in the development of CES. However, most cases involving lidocaine-associated CES have been attributed to sacral maldistribution with microcatheters (removed from the market in the United States in the early 1990s) and the administration of excessive doses of hyperbaric 5% lidocaine via the continuous spinal anesthesia technique [2-4] rather than to a unique neurotoxic property of the drug per se. Then in 1997 Gerancher described CES after a single spinal administration of 5% hyperbaric lidocaine through a 25-gauge Whitacre needle. [5]

The current publication by Loo and Irestedt describes five cases of CES after "single-shot spinal" with hyperbaric 5% lidocaine and one case of CES after two doses of spinal hyperbaric 5% lidocaine that were reported to the Swedish Pharmaceutical Insurance from 1993 to 1997. The dose of hyperbaric 5% lidocaine administered ranged from 60 to 120 mg, and the ages of the patients ranged from 31 to 59 years.

Clearly, as the authors so appropriately underscore, the diagnosis of direct local anesthetic neurotoxicity is one of exclusion. Care must be exercised to rule out trauma; spinal cord ischemia (localized or global); infection; compression by hematoma, abscess, prolapsed intervertebral disc and spondylolisthesis; contamination of local anesthetics; and injurious surgical positioning. With regard to the latter phenomenon, it is important to point out that the lithotomy position stretches the cauda equina and may jeopardize perfusion of the nerves, rendering them vulnerable to neurotoxicity.

Loo and Irestedt considered that three of the cases were most probably the result of direct neurotoxicity of hyperbaric 5% lidocaine. Furthermore, in the other three cases, direct neurotoxicity was also probable, but a compressive etiology could not be excluded owing to the omission of appropriate radiological studies.

Both animal and epidemiologic studies indicate that lidocaine neurotoxicity is concentration- and dose-dependent. Drasner has suggested that there is little justification for administering more than 60 mg lidocaine, [6] and it is important to appreciate that Astra USA wrote a "Dear Doctor" letter in 1995, revising its prescribing information for hyperbaric 5% lidocaine, wherein they suggested mixing the drug with an equal volume of CSF or preservative-free saline solution thereby producing a concentration of 2.5 percent [7]. Emphasizing that no cases of CES have been linked to hyperbaric lidocaine in concentrations less than 5% when administered in doses not greater than 100 mg, Loo and Irestedt, taking a conservative approach in the context of serious potential risk, recommend that hyperbaric lidocaine should be administered in concentrations not greater than 2% and a total dose preferably not exceeding 60 mg.

References

ABSTRACT

Cauda Equina Syndrome After Spinal Anesthesia with Hyperbaric 5% Lignocaine: A Review of the Six Cases of Cauda Equina Syndrome Reported to the Swedish Pharmaceutical Insurance 1993-1997

AUTHORS:
Loo CC, Irestedt L.

SOURCE:
Acta Anaesthesiol Scand 1999;43:371-379

ABSTRACT:
Six cases of cauda equina syndrome with varying severity were reported to the Swedish Pharmaceutical Insurance during the period 1993-1997. All were associated with spinal anaesthesia using hyperbaric 5% lignocaine. Five cases had single-shot spinal anaesthesia and one had a repeat spinal anaesthetic due to inadequate block. The dose of hyperbaric 5% lignocaine administered ranged from 60 to 120 mg. Three of the cases were most likely caused by direct neurotoxicity of hyperbaric 5% lignocaine. In the other 3 cases, direct neurotoxicity was also probable, but unfortunately radiological investigations were not done to definitely exclude a compressive aetiology. All cases sustained permanent neurological deficits. We recommend that hyperbaric lignocaine should be administered in concentrations not greater than 2% and at a total dose preferably not exceeding 60 mg.