CLINICAL-EXPERIENCE WITH 118 BRAIN-TISSUE OXYGEN PARTIAL-PRESSURE CATHETER PROBES

OBJECTIVE: We assessed the technical and diagnostic reliability of par tial pressure of oxygen (PO2) of brain tissue (P(ti)O-2) monitoring. T he monitoring system and the catheter probes were tested in vitro, and clinical experiences obtained with 118 brain P(ti)O-2 catheter probes , used in 101 patients, are reported. METHODS: The polarographic (LICO X; Medical Systems Corp., Greenvale, NY) P(ti)O-2 catheter probe lies 22 to 27 mm below the dura level; its PO2-sensitive surface is 7.1 mm( 2). For 10 patients, the adaptation time (with initially unreliable si gnals after insertion) was determined. For 27 patients, the probe was removed in a stepwise fashion (three increments of 5 mm) and the heter ogeneity of brain P(ti)O-2 levels was investigated, after removal of t he catheter probes, their PO2 and zero display error values were deter mined and compared with probe performance data obtained in vitro with unused PO2 catheter probes. RESULTS: Small iatrogenic hematomas were o bserved for two patients (1.7%). No infection occurred after 6.7 +/- 3 .9 days (mean a standard deviation) of monitoring. The technical compl ication (dislocation or defect) rate was 13.6%. The mean adaptation ti me was 79.0 +/- 51.7 min. A flow chart is presented, which helps to ru le out artifacts. The mean P(ti)O-2 measured at 22 to 27 mm below the dura was 23.8 +/- 8.1 mm Hg, at 17 to 22 mm was 25.7 +/- 8.3 mm Hg, at 12 to 17 mm was 33.0 +/- 13.3 mm Hg (P < 0.01, compared with the init ial value), and at 7 to 12 mm was 33.3 +/- 13.3 mm Hg (P < 0.01). Rece nt catheter probe versions exhibited a PO2 display error of -1.2 +/- 5 .1% (mean +/- standard deviation, n = 38) and a mean zero display erro r of 1.1 +/- 0.9 mm Hg (n = 34). The greatest PO2 display errors were measured during the first 4 days of continuous monitoring. In the in v itro test (of 12 unused catheter probes), the maximal probe display er ror was 1.07 +/- 2.14%, tested at temperatures between 22 degrees C an d 37 degrees C and tested at oxygen pressures of 0, 44, and 150 mm Hg. In vitro, the zero display error was -0.21 +/- 0.25 mm Hg. CONCLUSION : Brain P(ti)O-2 monitoring, reflecting an area 17 to 27 mm below the dura, is a safe and reliable technique for monitoring cerebral oxygena tion. Excluding the first 1 hour after insertion, data are reliable, w ith almost 100% good data quality.