How Do I Know My Patient is A live?

Question

You are using a pulse oximeter on a cat undergoing ovariohysterectomy under general anaesthesia. Partway through the surgery the pulse oximeter begins alarming and reporting an oxygen saturation of 87%. What steps should you now take?

Answer 

Look at the cat – do the mucous membranes look blue (this is unlikely as our ability to detect cyanosis is quite poor)?

Move the probe – repositioning is very important as a first step as the capillary bed becomes squeezed and the monitor then may give a false reading. Once the probe is reattached, see if the reading has changed (usually it then will increase).

Check the monitor for a good signal, determined by either examining the waveform generated by the pulse oximeter, or by observing a signal indicator light (usually green).

If the reading is still low then a search for a cause must begin. Preferably confirm the reading using blood gas analysis if available. However, an arterial sample from a cat will be difficult to obtain.