ABSTRACT
OBJECTIVE: To determine the correlation of PaCO2 and ETCO2 during operations for lumbar disk herniation in prone position: the influence of position and deliberate hypotension. DESIGN: Prospective, to compare PaCO2, ETCO2, pH, SBE, Pa max, in a group of 10 patients undergoing elective intervention for lumbar disk herniation in prone position and in a control group of 10 patients undergoing interventions for elective non traumatologic orthopaedic surgery of the lower limbs in supine position. SETTING: Orthopaedic department of a non teaching hospital. MEASUREMENTS AND MAIN RESULTS: The results for the patients of the supine group were: mean PaCO2 35.26 mmHg (SD 3.045), mean P(a-ET)CO2 3.46 mmHg (SD 1.898), mean pH 7.433 (SD 0.044), mean SBE - 1.16 (SD 1.718), mean Pa max 122.5 mmHg (SD 17.989). In the prone group: mean PaCO2 30.3 mmHg (SD 5.819), mean P(a-ET)CO2 1.4 mmHg (SD 4.445), mean pH 7.430 (SD 0.052), mean SBE-3.93 (SD 3.255), mean Pa max 100.3 (SD 10.945). The difference was significant (p < 0.05) for pH, PaCO2, SBE; in the prone group the variability of P(a-ET)CO2 was greater and the values related with SBE. CONCLUSIONS: ETCO2 is a useful monitoring for PaCO2 in the situation evaluated but the accuracy of the correlation with PaCO2 is lesser than during standard surgical techniques, the metabolic acidosis observed is probably related to the effects of the peculiar position and the anaesthetic technique.
