What intraoperative monitoring makes sense?

The routine practice of monitoring oxygenation, ventilation, circulation, and temperature during surgery is now the standard of care. However, with the possible exception of pulse oximetry and capnography, extensive physiologic monitoring has not been shown to reduce the incidence of adverse anesthestic-related events. Monitors are useful adjuncts, but they alone cannot replace careful observation by a vigilant anesthesiologist.