Just take off the mask!

By Fred C. Quarnstrom, DDS, FADSA, FAGD, FICD, FACD, CDC, FACDNitrous oxide oxygen sedation is probably the safest pharmacologic sedation technique a dentist can use. At one time in the 1970s it was estimated that close to 50% of dentists used nitrous oxide sedation. At the time, the membership in the ADA was close to 120,000. If each practitioner used nitrous once a day and worked 200 days each year, that would translate to close to 100 million uses a day.This went on for years. In all that time I know of one death. An oral surgeon put a patient to sleep and intubated him in preparation for surgery. The surgeon was new out of his residency and was using an ECG monitor showing the patient’s heartbeat. This monitoring was uncommon in the 1960s. The surgeon noticed some aberrant heatbeats and stopped the procedure before surgery was started. He put the patient on 100% “oxygen” and waited for the anesthetics to wear off. At this time it was common to use Pentothal^®. He saw more and more arrhythmias, and the patient then went into cardiac arrest. The medical team started CPR with the help of an MD surgeon in his building. They were unable to revive the patient. The patient was in his late 20s and had been in a hospital only one time to have a knee injury treated. What a tragedy, but it appeared that everything that could have been done was done.It was discovered sometime later that the room they were using had the oxygen and nitrous oxide lines switched. When they had put the patient on 100% oxygen, he was actually getting 100% nitrous oxide. Oxygen is necessary to sustain life.

Shortly after starting the lab, one of the participants came to me and said we had a patient who was asleep. I move very fast when I am concerned. I immediately took the patient’s pulse. It was regular and about 70 beats per minute. My pulse dropped from 200 to about 180. I asked someone to bring my emergency kit. Next I pinched the patient’s arm; there was no response. She was out. I looked at the machine and saw that it was delivering 1 L./minute of nitrous oxide and 4 L./minute of oxygen, a 20% mixture of nitrous oxide. However, the patient was out under general anesthesia. I shut off the nitrous oxygen and raised the oxygen flow to 7 L./minute. I took the patient’s blood pressure; it was 125/65 — quite good for someone who appeared to be in her 60s. However, she was unresponsive.My pulse went from 180 to about 140. My cognitive skills were dropping very rapidly as the emergency continued. I was teaching in a state where I was not licensed. We were now into this emergency about three minutes. This could qualify as the unlicensed practice of dentistry. I needed to call for help and get the patient transferred to a hospital. She was not responding to any stimulation. I decided to take the mask off and get her breathing room air. After all, she had been fine on room air. I took the mask off and she was awake in a minute.That was when I noticed a green hose going down to a blue tank and a blue hose going down to a green tank. I decided it was time to take a coffee break. I needed to get my nervous system under control.I had set up the machine backward because I depended on the pins that should prevent this ... and they were gone! Thirty-five years later, I know of about 65 times when machines or systems have been set up backward. Plumbers have switched gas lines. Too many washers have been placed between the yolk and small tanks, making the pin index system useless. A manufacturer set a machine up backward, and in one case a failsafe valve failed, backfilling the oxygen line with nitrous oxide.What is the solution?

• First, check out your system every time any plumbing is changed.
• Turn on the oxygen tank and be sure only oxygen outlets are pressurized and that the nitrous oxide lines are not pressurized.
• Bleed the pressure from the oxygen line and do the same for the nitrous oxide line.
• Any time a plumber changes your plumbing, check the lines.
• When you go to a new office, check the lines.
• If you are doing general anesthesia or IV sedation, always monitor oxygen saturation with a pulse oximeter.
• If the saturation starts falling, consider that the lines may be switched and go to a small oxygen tank that is independent of the in-office piping.

What are the five most important steps you can take in this situation?

1. If a patient goes to sleep, take off the mask. Do not oxygenate.
2. If a patient goes to sleep, take off the mask. Do not oxygenate.
3. If a patient goes to sleep, take off the mask. Do not oxygenate.
4. If a patient goes to sleep, take off the mask. Do not oxygenate.
5. If the patient does not awake immediately, call 911. You do not get points against you for calling for help.

Fortunately, true emergencies are rare in a dental office. Consequently, even if we practice for emergencies, it is very difficult to be prepared to treat all of the potential problems we might see. The paramedics prefer to arrive while the patient is still alive. This really improves their save ratio. When we see a true emergency, cognitive thought becomes difficult. The paramedics see emergencies every day and are very good at handling emergencies. Call 911 for help sooner rather than later.