Pin index safety system and color coding: is it enough?

Despite a number of preventive mechanisms, inadvertent administration of nitrous oxide in place of oxygen can lead to fatal hypoxemia. Here we report two cases of hypoxia that occurred when we switched to the emergency cylinder for oxygen supply after exhaustion of the main oxygen cylinder. The urgency shown by the anesthetist and operating room staff to restore the main oxygen supply prevented any fatalities from occurring in our case. We found that there was incorrect painting of the nitrous oxide cylinder with the color code of oxygen. Further, damaged pins on the yoke assembly allowed the attachment of the faulty E cylinder to the machine. Even though such errors are made by the supplier we suggest that all equipment including the cylinder be thoroughly checked by the anesthetist. This also highlights the role of respiratory gas monitoring in the prevention of such mishaps.