Bispectral index monitoring in ischemic-hypoxic brain injury

Abstract

The BIS monitor is a simple-to-use and widely available monitor used in cardiac surgery. It can provide useful new information regarding the patient's hypnotic state, but also other components of brain function. The detection of cerebral hypoperfusion is of prime importance to perfusionists and others caring for patients undergoing cardiac surgery. BIS values consistent with the anesthetic drug and dose administration should reflect adequate cerebral perfusion and function. Abnormally low or a sudden deterioration in BIS values probably indicate cerebral hypoperfusion and should be taken seriously. A growing number of anecdotal reports and small case series support these contentions, but large prospective outcome studies are needed before this technology can be reliably used to monitor cerebral perfusion and other aspects of brain function during surgery.

Figure 1.

Changes in the bispectral index with severe hypotension during tricuspid valve replacement. Systolic blood pressure decreased to ∼30 mmHg at around 09:01 (A and B). Intravenous fluids and vasoconstrictor therapy was instituted (C) but uncontrolled bleeding worsened (D) and it took a further 9 minutes for the patient’s blood pressure to be stabilized on CPB. Reproduced with permission from England MR. The changes in bispectral index during a hypovolemic cardiac arrest. Anesthesiology. 1999;91:1947–9.

Figure 2.

Bispectral index and systemic blood pressure during off-pump surgery. After positioning of the heart for distal anastomosis of left circumflex coronary artery grafting, the arterial blood pressure decreased to 70/35 mmHg and the BIS decreased from 45 to 0. Reproduced with permission from Hemmerling TM, et al. Bispectral index as an indicator of cerebral hypoperfusion during off-pump coronary artery bypass grafting. Anesth Analg. 2005;100:354–6.