Two cases of using the bispectral index (BIS) to evaluate the depth of sedation during therapeutic hypothermia in patients after cardiopulmonary resuscitation

Abstract

During therapeutic hypothermia (TH) in patients after cardiopulmonary resuscitation, it is often necessary to administer a neuromuscular blocking agent due to shivering, thus making it difficult to evaluate the depth of sedation. We herein report two patients who underwent TH while controlling the sedation dosage based on the bispectral index (BIS) level, and we also evaluated BIS using portable electroencephalograms (pEEG). First, a 37-year-old male was administered a sedative dosage due to the fact that the BIS level was under 60. pEEG showed α waves and similar changes to those associated with the BIS level were observed. The patient awoke early after TH. Second, a 63-year-old male was managed without sedation because the BIS level remained under 10. pEEG showed flat waves and the neurological prognosis indicated a poor outcome. BIS is useful and readily-controlled, however, BIS has not yet been established as an accepted evaluation method in patients with brain disorders. However, light sedation could be avoided in these cases due to the use of BIS. In addition, a BIS value of 0 was thus suggested to be a possible diagnostic factor for a poor neurological prognosis.