LOCAL OXYGEN-SUPPLY TO THE CEREBRAL-CORTE X DURING THIOPENTONE AND PROPOFOL ANESTHESIA - 1ST RESULTS

Because the brain is highly vulnerable to damage from even a brief imb alance of oxygen delivery and demand, intraoperative disturbances of l ocal oxygen supply must be avoided. Until now, there has been no metho d allowing fast and reliable intraoperative measurement of the local o xygen supply in the human brain. Intraoperative investigations were th erefore performed using the Erlangen micro-lightguide spectrophotomete r. Methods. Intraoperative investigations of local intracapillary haem oglobin saturation (SO2) were performed during neurosurgical intervent ions using the Erlangen microlightguide spectrophotometer (EMPHO). Mea surements were performed in eight patients (age 31-67 years) during ne urosurgical interventions. Three received thiopentone anaesthesia, and three received propofol. In two patients thiopentone anaesthesia was later changed to propofol. The EMPHO enables rapid, non-invasive measu rement of local intracapillary SO2. White light from a Xenon-arc lamp is transmitted by a 250-mum micro-lightguide to the tissue. The remitt ed (reflected) light is led by 6 micro-lightguides surrounding the ill uminating one to a rotating band-pass interference filter disk. Light in the range of 502 to 630 nm is detected with a photomultiplier. In t his range haemoglobin shows an SO2-dependent spectrum, which is then a nalysed. Because the measurements are performed with micro-lightguides , high spatial resolution is attained. Representative measurements can be performed in a very short period of time (approx. 60 s); thus, the EMPHO enables rapid monitoring of local SO2 in the brain. Results. Th e effect of propofol and thiopentone anaesthesia on the distribution o f local intracapillary haemoglobin saturation was investigated during neurosurgical interventions. The arterial PCO2 was similar in both gro ups (31 +/- 0.7 and 31 +/- 0.5 mmHg, respectively). There were also no differences in arterial blood pressure. The FiO2 was 0.28 +/- 0.04 in the thiopentone group and 0.30 +/- 0.1 in the propofol group. In all patients receiving propofol anaesthesia higher local SO2 values were f ound, even if the patients first received thiopentone (values in paren thesis). The mean local SO2 amounted to 65.4% (57.3%) in the propofol group and 38.8% (45.2%) in the thiopentone group. The number of values below 25% SO2 was 5.6% (5.8%) in the propofol group and 18.7% (19.1%) in the thiopentone group.