High ambient oxygen flow saturation during anaesthesia and its effect on surgical fires
From the United States: a report on oxygen flow during anaesthesia as the potential cause of surgical fires was recently published in Anesthesia Progress. The report states that: as office-based (general practice) oral surgeries are becoming more common, the need for updated safety procedures is a growing concern for practitioners.
During oral surgery, the use of anaesthesia is not unusual, and with high oxygen saturation levels comes the increased risk for surgical fires. It is therefore necessary that dental anaesthesiologists, as well as oral and maxillofacial surgeons, establish and follow standards to decrease the risk of combustion during surgery.
Researchers from the Riley Hospital for Children/Indiana University School of Dentistry, Indiana University School of Medicine and Purdue University in Grand Rapids, Michigan, examine the effect of ambient oxygen on surgical fire occurrence.
In a controlled environment, under a vented chemical hood, the researchers performed 30 trials at each oxygen saturation level (60%, 80% and 100%) with flow rates of either 4 or 10 litres per minute (L/min) to detect latency time to combustion.
To mimic the oral cavity, they used a raw chicken carcass, which allowed for the use of an oxygen-supplied tube to be secured and two gauze sponges to be placed, creating a more realistic surgical setting. Additionally, a standard electrosurgical tip, a commonly used dental tool, was inserted to provide an ignition source.
The researchers were able to obtain real-time data with the use of a thermometer, dew point hygrometer and oxygen sensor, which were all connected to a computer during each trial. The readings obtained confirmed that conditions were consistent throughout all trials.
The researchers categorized their data according to specific occurrences during the trials: the time to the first event, the time to the first pop and the time to the first flash or fire. The results indicated that the total number of fire events increased significantly as the oxygen saturation levels increased; specifically, saturation levels at 60% were much lower than at 80% or 100%.
It was also noted that there was a correlation between the flow rate and the time to the initial fire event, as the flow rate of 10 L/min did increase the number of events. Ignitions were found to be significantly higher at 100% than at 60% or 80%; similarly, ignitions were much higher at the 10 L/min flow rate with 100% oxygen than at the 4 L/min rate.
Overall, the higher the oxygen saturation and flow rate, the more likely a surgical fire is to occur. Dr. Leah Davis, one of the researchers involved in this study, commented: “This research is interesting and exciting to me because dental anaesthesia is something that is becoming more widely used every day, but cannot be taken lightly.
“More research and regulations need to be put in place to make sure all procedures will keep patients safe.”
The study confirms that the previously recommended oxygen saturation levels and flow rates remain safe. However, researchers suggest future study is warranted to determine the minimum concentration and flow rates that could cause combustion during oral surgery.
The current literature regarding surgical fires during oral surgery is lacking, and as more office-based surgeries are occurring, more data points are needed to set a standard of care.
Full text of the article, “The Effects of Different Levels of Ambient Oxygen in an Oxygen-Enriched Surgical Environment and Production of Surgical Fires,” Anesthesia Progress, Vol. 65, No. 1, 2018, is now available here: http://www.anesthesiaprogress.org/doi/full/10.2344/anpr-64-04-12.
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