Anaesthesia for spinal surgery in children
Edmonton, Alberta, Canada
* E-mail: jnorton{at}ualberta.ca
Editor—Soundarajan and Cunliffe have produced an admirable summary of the conditions requiring spinal surgery in children and the major anaesthetic considerations surrounding this type of surgery.1 Any review of such a challenging and diverse subject matter must, by necessity, give only cursory attention to certain aspects of anaesthetic care. The authors briefly describe the use of spinal cord monitoring towards the end of their review. We would like to elaborate on the issues surrounding monitoring of spinal cord function intraoperatively, as this is both of rapidly increasing importance in the field and of great impact on the anaesthetic technique. After the publication of guidelines in 1991,2 monitoring of spinal cord function has become the standard of care in scoliosis surgery and is increasingly utilized in other spinal surgeries. With the approval by regulatory bodies of appropriate stimulators, and the publication of workable guidelines, Tc motor evoked potentials (MEPs) are increasingly used in addition to somatosensory evoked potentials (SSEPs).3 This type of monitoring presents an additional challenge to the anaesthetist. In the majority of centres, the MEPs are recorded from the muscles, especially in scoliosis surgery, to avoid the need of placing electrodes on the spinal cord. This necessitates the entire anaesthetic management be tailored to the requirements of this monitor. The anaesthetic cannot include ongoing neuromuscular block, and particularly in children, reliable recordings of MEPs are best obtained in the absence of many of the halogenated agents. This makes a total intravenous anaesthesia (TIVA) approach utilizing propofol and a short-acting opioid infusion preferable.4 5 In our experience, in children in particular, MEPs recorded using EMG needle electrodes elicited with multi-pulse transcranial electrical stimulation are poorly recorded and reproducible if the mean arterial pressure is <60 mm Hg. There are benefits. When monitoring is taking place, the neurophysiology technician will frequently record EEG, allowing the anaesthetist to determine depth of anaesthesia with increased accuracy. This is important in the face of the significant impact that depth of anaesthesia has on spinal cord monitoring. Although burst suppression allows for easy recording of SSEPs, it can lead to difficulty in obtaining TcMEPs due to loss of the oscillatory activity in the motor cortex which is crucial for generation of TcMEPs. Preserving neural function, especially in children, is of critical importance. In many instances, scoliosis surgery is at least semi-elective yet presents a significant risk of neural damage. Appropriate and comprehensive neuromonitoring is therefore crucial and the anaesthetic monitoring considerations are of major importance to the safe completion of surgery. As can be clearly seen from this description, this is an area which requires experience and communication. As spinal surgery increasingly becomes a team activity with the involvement of the surgeon, anaesthetist, and neurophysiologist, it is important that we recognize that we may need to alter our choice of anaesthetic in order to provide for improved patient safety.6 We would like to thank Soundarajan and Cunliffe for drawing renewed attention to this important and developing area of paediatric anaesthetic care.
Liverpool, UK
* E-mail: mary.cunliffe{at}rlc.nhs.uk
Editor—We would like to thank Drs Norton and Cave for their comments on our article.1 As they quite rightly point out, it is difficult within the confines of a word limited review to sometimes put in as much information as you would like on a particular aspect of care. I hope we did stress the importance of spinal cord monitoring in patients undergoing this type of surgery, which is now a standard of care for these patients. We would also like to fully endorse the view that spinal cord monitoring is a team event which involves the neurophysiologist, the anaesthetist, and the surgeon. The choice of which type of monitoring to use has also increased, and we must choose the technique that will be most sensitive and accurate within the context of the surgery being performed.
References
1 Soundararajan N, Cunliffe M. Anaesthesia for spinal surgery in children. Br J Anaesth (2007) 99:86–94.
2 Dawson EG, Sherman JE, Kanim LEA, Nuwer MR. Spinal cord monitoring: results of the Scoliosis Research Society and the European Spinal Deformity Society Survey. Spine (1991) 16:S361–4.[CrossRef][Web of Science][Medline]
3 MacDonald DB. Intraoperative motor evoked potential monitoring: overview and update. J Clin Monitoring Comput (2006) 20:347–77.[CrossRef]
4 Pajewski TN, Arlet V, Phillips LH. Current approach on spinal cord monitoring: the point of view of the neurologist, the anesthesiologist and the spine surgeon. Eur Spine J (2007) in press.
5 Sloan TB, Heyer EJ. Anesthesia for intraoperative neurophysiologic monitoring of the spinal cord. J Clin Neurophysiol (2002) 19:430–43.[CrossRef][Web of Science][Medline]
6 Raw DA, Beattie JK, Hunter JM. Anaesthesia for spinal surgery in adults. Br J Anaesth (2003) 91:886–904.
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