What are the causes of low oxygen sat rates after surgery?

Interpret right. It depends on the timing. Worst could be pulmonary embolus form immobility several hours after. But right after surgery, usually the or is cold and causes closing off of skin arterioles (response to cold temp) and since the monitor is dependent on pulses could read wrong. The best time to ask is when it is happening as the health officer can correlate with timing and symptoms.
many. There can be many causes, the most common after surgery is atelectasis due to poor inspiration. This can be improved by using the bedside incentive spirometer frequently. Other causes include excessive sedation, pulmonary edema, or rarely pulmonary embolism.