RESPIRATORY EFFECTS OF EXTRADURAL ANALGESIA AFTER LOWER ABDOMINAL SURGERY

Blood-gas tensions, FRC and volume of trapped gas (V_TG) in thelung were measured in patients on the day before lower abdominalgynaecological surgery, and twice on the day following surgery,before and after establishing lumbar extradural block (EDB)using 0.5% bupivacaine to provide analgesia after operation.FRC and V_TG were measured with the closed-circuit helium-dilutiontechnique. Mean VTG was 175 ml before operation and 275 ml afteroperation. Pa_O2decreased significantly after operation, andthe changes in FRC and V_TG that occurred were related qualitatively.EDB did not significantly alter FRC, V_TG or Pa_O2. Individualchanges in FRC could not be related to changes in V_TG or Pa_O2.Although EDB provided effective analgesia, the variables measureddid not indicate that EDB conferred an immediate respiratoryadvantage.