Inadvertent severe hypercapnia during general anesthesia: drop-in oxygen saturation or electrocardiography changes; which one warns us earlier?

Abstract

Abstract Background During general anesthesia especially when the nurse or anesthesiologist forgets to change manual to controlled mode after successful endotracheal intubation, capnography shows End-tidal Co2 above 20 mmHg after checking the place of the tracheal tube and will remain on the screen permanently. In this scenario, the patient receives a high concentration of oxygen, and Spo2 (oxygen saturation) does not drop for a long time which is too late to intervene. It has been all-time questionable which one of the cardiac dysrhythmias or Spo2 dropping occurs earlier. Results Medical records of seven deceased patients reviewed. All of them had electrocardiogram changes including premature ventricular contraction or bradycardia as a first warning sign. Oxygen saturation remains above 95% even with cardiac dysrhythmia. Conclusions Bradycardia and premature ventricular contraction were the first warning findings for severe hypercapnia during general anesthesia and occurred earlier than dropping oxygen saturation. Furthermore, the normal capnography waveform is more reliable than the End-tidal Co2 number for monitoring.