Severe hypoxemia is considered by many to contraindicate major surgery. Several studies have shown that dependency on oxygen, PaO₂ ≤ 60 mmHg, PaCO₂ ≥ 45 mmHg, FEV1 ≤50%, and FVC ≤ 75% are indicative of a high risk of morbidity and mortality following major surgical procedures. Here, we report our experience of the use of regional anesthesia in such patients. One patient was a 82-year-old female patient who was scheduled for partial hip replacement due to a fracture of the right femur. Her pulmonary function test and preoperative arterial blood gas analysis results were as follows: FVC 1.23 L (49.1%), FEV1 1.11 L (61.3%), FEV1/FVC 90.2%, a room air pH 7.423, PaCO₂ 43.0 mmHg, PaO₂ 46.4 mmHg, SaO₂ 84.5% and base excess 2.7 mM/L. Another patient was a 79-year-old COPD male patient scheduled for appendectomy. His immediate preoperative arterial blood gas analysis results were; room air pH 7.368, PaCO₂ 62.1 mmHg, PaO₂ 43.8 mmHg, SaO₂ 77.4% and base excess 7.3 mM/L. Both patients underwent and tolerated surgery safely with regional anesthesia. No permanent sequela occured postoperatively in these cases. No severe changes in room air arterial blood gas levels were observed before and after surgery. We present a review of two cases of severe hypoxemia in which a regional block was used.