BIS biz

Often seems another distracting number which doesn't add to the scheme of anaesthesia, but BIS can be a handy tool of reassurance when there may be doubts about adequate cerebral perfusion. In particular it can indicate adequate cerebral perfusion and function when position and high venous pressure might compromising. Recent cases when it has reassured me have been a thoracic level laminectomy and a prolonged gyne laparoscopy when the relatively low positions of the head caused estimated venous pressures of 20 - 30 cmH2O. In addition to measures to maintain arterial pressure and minimise cerebral vasodilatation normal BIS values and waveform indicated we could safely persevere with surgery in the desired position.