Neurological deterioration after laryngeal mask insertion

I. Calder1, A. M. McLeod1, T. Asai2, K. Shingu2, C. J. Edge3, V. Addy3 and C. Kearns3

1 London, UK 2 Osaka, Japan 3 Oxford, UK

{dagger}LMA® is the property of Intavent Limited.

Editor—We feel that aspects of the case report by Edge and colleagues, describing a man who became tetraparetic after a laparoscopic cholecystectomy,1 are unsatisfactory.

The title and introduction of the report suggest that the insertion of an LMA{dagger} was related to the neurological deterioration suffered by the patient. However, in the discussion, Edge and colleagues state that ‘neck manipulation as a result of ... insertion of the LMA cannot be blamed’. Readers are entitled to know whether the authors believe that the LMA had anything to do with the neurological deterioration or not.

Edge and colleagues repeatedly described their patient’s spine as unstable, presumably because of the rupture of the posterior longitudinal ligament (PLL).1 Edge and colleagues do not make it clear at what level the rupture was (we imagine it was C5/6), or whether ‘completely’ ruptured, means perforated, or transversely discontinuous. Even if it was the latter, the study by White and colleagues of the effect of destroying various elements of the cervical spine does not support the view that an isolated rupture of the PLL would make the spine unstable.2 Edge and colleagues’ concluding paragraph about the theoretical dangers of small movements in unstable patients is not supported by reference to the literature and is inapplicable to their case.

Edge and colleagues make it clear that the patient was developing a myelopathy in the days before his anaesthetic. The patient had an intraspinal haematoma. The rupture of the PLL could have been due to a spontaneous intraspinal haemorrhage or vice versa. We presume that the haematoma was the cause of the patient’s myelopathy and that the purpose of the neurosurgical intervention was to drain it. Do Edge and colleagues have a different view?

Patients with spinal abnormalities are at risk of neurological damage during anaesthesia.3 Patients with pre-existing myelopathy are probably at even greater risk.4 Weglinski, Berge and Davis have added to the literature on this point within the last year.5 Edge and colleagues’ unfortunate patient was definitely at risk. We have rehearsed the probable causation of these injuries in a recent editorial, 3 but in essence we believe that prolonged minor degrees of malposition eventually result in hypoperfusion of the cord. In our view, it is likely that similar mechanisms operate in the induction of both peripheral and neuraxial nerve injury. Prolonged minor compression and/or stretching of nervous tissue results in damage. The problem with anaesthesia is that it results in loss of the normal protective reflexes that deflect the consequences of minor degrees of malposition, as Copleteers, Van de Velde and Stappaerts have emphasized.6

The sooner anaesthetists, neurologists and surgeons comprehend that spinal cord injury is a hazard of anaesthesia, take this into account when contemplating surgery, and stop thinking we can obviate the risk by some variation in the method of airway management, the better for our patients.

It would appear that Edge and colleagues have been influenced by our editorial, and cite many references in common with it. We are disappointed that they have not absorbed our central message. Their report has introduced an unjustified association between the LMA and spinal cord injury into the literature; we regret its publication.

I. Calder

A. M. McLeod

London, UK

Editor—We found that the article by Edge and colleagues was misleading.1 First, the majority of people would get the impression from the title that this is a report of posterior spinal ligament rupture produced by insertion of the LMA. However, the authors stated in the discussion that ‘In our case, neck manipulation as a result of direct laryngoscopy or insertion of the LMA cannot be blamed’.1 It becomes obvious only when one reads the case presentation and discussion that the laryngeal mask was an unlikely cause of this damage. The patient had suffered from severe neck pain with weakness in the legs and some difficulty in walking before the operation and, for whatever reason, the symptoms worsened after surgery. We believe that the title should reflect the contents of the article accurately, because busy clinicians would often only read the titles of the articles, particularly when an internet search is used. The abstract of the article does not rectify this misleading title.

Second, their claim about the safety of laryngoscopy in patients with unstable necks is also misleading. In the introduction, the authors state that ‘[a]ccording to prevailing dogma, direct laryngoscopy is hazardous in the presence of cervical instability’.1 We should attempt to minimize movement of the head and neck during insertion of an airway device, as studies in cadavers and anaesthetized patients have shown some movement of the neck during insertion of an airway. Nevertheless, direct laryngoscopy and tracheal intubation have been performed routinely in numerous patients with unstable necks, and there have only been a few case reports of possible damage to the spinal cord from these procedures. It is reasonable to conclude therefore, that as long as we take careful measures to protect the neck (such as manual in-line head and neck stabilization), direct laryngoscopy and tracheal intubation can be performed safely without damaging the cervical spine in the majority of patients. The authors’ claim is therefore unsubstantiated, and we fear that such a statement may mislead people, such as orthopaedic surgeons, patients, and lawyers. It would be sad if any case of tracheal intubation in a patient with an unstable neck was brought to the courts based on this unsound dogma. In this era of evidence-based medicine, we should summarize what we know, and improve our clinical practice further, based on reliable data and sound reasoning.

T. Asai

K. Shingu

Osaka, Japan

Editor—Thank you for the opportunity to respond to this correspondence. We described a temporal association between a devastating deterioration in neurological function and the insertion of a laryngeal mask airway. In our patient, there was probably pre-existing unrecognized damage to the posterior longitudinal ligament. This was worsened during the procedure to create a haematoma and result in critical cervical cord compression. The presence of a haematoma at the site of complete rupture on MRI scan and at surgical decompression was taken as a sign of recent injury. We acknowledged the potential reduction in spinal perfusion pressure that may accompany moderate arterial hypotension during anaesthesia.1

Cervical spinal cord injury produced by airway manoeuvres is extremely rare. We agree that if measures are taken to protect the neck in suspected cervical spine injury, then the airway can be secured safely. In our case, there was no suspicion of cervical spine abnormality and therefore no such protective measures were taken.

Cadaveric and radiological studies may describe expected cervical spine movement in specific populations. However, there is still a place in the literature for a case report describing a catastrophic event as a result of a combination of unusual circumstances.

C. J. Edge

V. Addy

C. Kearns

Oxford, UK

References

1 Edge CJ, Hyman N, Addy V, et al. Posterior spinal ligament rupture associated with laryngeal mask insertion in a patient with undisclosed unstable cervical spine. Br J Anaesth 2002; 89: 514–17[Abstract/Free Full Text]

2 White AA, Johnson RM, Panjabi MM, Southwick WO. Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop 1975; 109: 85–96[Medline]

3 McLeod AM, Calder I. Spinal cord injury and direct laryngoscopy—the legend lives on. Br J Anaesth 2000; 84: 705–9[CrossRef][ISI][Medline]

4 May DM, Jones SJ, Crockard HA. Somatosensory evoked potential monitoring in cervical surgery: identification of pre- and intraoperative risk factors associated with neurological deterioration. J Neurosurg 1996; 85: 566–73[ISI][Medline]

5 Weglinski MR, Berge KH, Davis DH. New-onset neurologic deficits after general anesthesia for MRI. Mayo Clin Proc 2002; 77: 101–3[ISI][Medline]

6 Coppleters MW, Van de Velde M, Stappaerts KH. Positioning in anesthesiology: toward a better understanding of stretch-induced peripheral neuropathies. Anesthesiology 2002; 97: 75–81[CrossRef][ISI][Medline]





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