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Anesth Analg 2006;103:1609-1610
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ane.0000246268.58067.99

LETTER TO THE EDITOR

Editor-in-Chief Steven L. Shafer

Elevated Burst Suppression Ratio: The Possible Role of Hypoxemia

Ngai Liu, MD, Thierry Chazot, MD, Catherine Mutter, MD, and Marc Fischler, MD

Department of Anesthesiology; Hôpital Foch; Université Paris Ile-de-France Ouest; Suresnes, France (Liu, Chazot) Departments of Anesthesiology and Intensive Care; Hôpital Hautepierre; Strasbourg, France (Mutter) Department of Anesthesiology; Hôpital Foch; Université, Paris Ile-de-France Ouest; Suresnes, France; m.fischler{at}hopital-foch.org (Fischler)

To the Editor:

We report a case characterized by the simultaneous occurrence of increased suppression ratio number (SR) and hypoxemia without a concomitant decrease in bispectral index (BIS).

A 59-yr-old man was scheduled for tracheal granuloma removal by laser, using a rigid bronchoscopy. The patient’s history included two lobectomies for epidermoid carcinoma. Anesthesia induction was induced and maintained with infusions of propofol and remifentanil. A bolus of succinylcholine was injected to facilitate introduction of the bronchoscope. The lungs were mechanically ventilated through the lumen of the bronchoscope using a high frequency jet ventilator. Six minutes after the succinylcholine bolus, his Spo2 decreased dramatically below 80% despite ventilation with pure oxygen, and we also observed an increase of the SR. BIS was in the range of 40–60 and signal quality index was more than 75%. His mean arterial blood pressure was 80 mm Hg. The bronchoscope was withdrawn and replaced by an endotracheal tube; the lungs were mechanically ventilated using pure oxygen. High airway pressure and auscultation revealed bronchospasm. Spo2 improved after inhalation of a beta2-agonist and we observed a decrease of the SR (Fig. 1). The endotracheal tube was removed. The patient’s postoperative neurological examination was normal.


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  		Figure 1. Acute decrease of Spo2 during rigid bronchoscopy. BIS, bispectral index; SR, burst suppression ratio; A, high frequency jet-ventilation; B, tracheal intubation; C to D, inhalation of beta2 agonist; E, recovery.

 

In general, burst suppression patterns appear at BIS levels below 40. The effect of an increasing concentration of a volatile anesthetic on the electroencephalogram is a progressive slowing until burst suppression patterns occur. Our observation of an increased SR appearing while BIS was at an adequate anesthetic level could have been a coincidence, but we cannot exclude a relationship between SR and poor brain tolerance of hypoxemia. This hypothesis is supported by animal studies demonstrating that hypoxemia induces isoelectric electroencephalograms, oxygenation allowing the restoration of a baseline electroencephalogram (1), and a reduction in cerebral tissue damage (2).

REFERENCES

  1. Feet BA, Brun NC, Hellstrom-Westas L, et al. Early cerebral metabolic electrophysiological recovery during controlled hypoxemic resuscitation in piglets. J Appl Physiol 1998;84:1208–16.[Abstract/Free Full Text]
  2. Burda J, Marsala M, Radonak J, Marsala J. Graded postischemic reoxygenation ameliorates inhibition of cerebral cortical protein synthesis in dogs. J Cereb Blood Flow Metab 1991;11:1001–5.[Web of Science][Medline]




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press