LETTERS TO THE EDITOR: Letters & Announcements
To the Editor:
The bispectral index (BIS), a parameter derived from the electroencephalogram (EEG), is currently used to assess the depth of sedation in intensive care unit patients (1). Moreover, good correlation has been reported between BIS and neurologic status in coma patients (2). Elsewhere, severe hypoglycemia may induce a decrease in EEG in either diabetic or nondiabetic patients (3,4).
An 84-year-old patient was admitted into the intensive care unit because of multiple organ failure 11 days after abdominal aortic aneurysm surgery. Sedation (sufentanil 15 μg / h and midazolam 6 mg / h) was continuously monitored using an A-2000 XP monitor (Aspect MS, Inc., Natick, MA). After a systematic capillary blood sample indicating a severe hypoglycemia (1.15 mmol / l), administration of glucose 30% was decided upon to correct this hypoglycemia. A few minutes after glucose infusion had begun, a rapid increase in BIS value was observed (Fig. 1). At this time, no other event, such as a change in ventilatory and hemodynamic conditions, sedation infusion rate, or external neurological stimulation to the patient, had occurred that could have explained such an increase in BIS value.
Because BIS is a parameter derived from the EEG and EEG changes were described during profound hypoglycemia, an increase in BIS value with correction of hypoglycemia seems totally understandable. Nevertheless, to our knowledge, this is the first report of change in BIS related to change correction of hypoglycemia. This observation confirms that BIS could be a reliable index of cerebral activity, not only during anesthesia and sedation, but also in various situations responsible for neurologic impairments.
Benoît Vivien, MD
Olivier Langeron, MD, PhD
Bruno Riou, MD, PhD
1. De Deyne C, Struys M, Decruyenaere J, Creupelandt J, Hoste E, Colardyn F. Use of continuous bispectral EEG monitoring to assess depth of sedation in ICU patients. Intensive Care Med 1998; 24: 1294–8.
2. Gilbert TT, Wagner MR, Halukurike V, Paz HL, Garland A. Use of bispectral electroencephalogram monitoring to assess neurologic status in unsedated, critically ill patients. Crit Care Med 2001; 29: 1996–2000.
3. Pramming S, Thorsteinsson B, Stigsby B, Binder C. Glycaemic threshold for changes in electroencephalograms during hypoglycaemia in patients with insulin dependent diabetes. Br Med J 1988; 296: 665–7.
4. Bjorgaas M, Sand T, Vik T, Jorde R. Quantitative EEG during controlled hypoglycaemia in diabetic and non-diabetic children. Diabet Med 1998; 15: 30–7.