Despite technological advances that have substantially improved the safety of gastrointestinal (GI) endoscopy in recent years, the risk for fatal gas embolism from insufflating gas—although extremely rare—is still present. In fact, a study by a University of Florida, Gainesville, research team has concluded that when the flush button is depressed on a popular manufacturer’s endoscope, gas is emitted from the tip at pressures capable of exceeding 300 mm Hg, which can cause complete circulatory compromise under the right conditions.
According to Jeffrey D. White, MD, the implementation of a new endoscopic technique at the Gainesville institution prompted him and his colleagues to consider how much insufflating gas pressure was being generated at the distal tip of the endoscope. “A search of the literature revealed no information, which surprised us,” said Dr. White, an assistant professor of anesthesiology at the University of Florida. “As such, we chose to look at all three types of endoscope that we have at our center: one for colonoscopy, one for GI endoscopy, and one for ERCP [endoscopic retrograde cholangiopancreatography].” The Olympus endoscopes tested, he said, do not list technical specifications on the company website for emitted gas flow or maximum pressure at the distal port. Insufflating gas pressure that exceeds local venous pressure raises the specter of potential embolic consequences.
Maximum pressure and flow at the distal gas exit port were tested on the Olympus GIF-Q180, CF-Q180 and TJF-Q180. Gas pressure was measured using an overtube with Tegaderm seal at the distal end, and a distal side port connection to an arterial pressure transducer. Each endoscope was seated within the overtube sleeve, with both ends completely sealed. Gas flow was set to a rate of 2 L per minute and the gas flush button depressed. Pressure was then measured within the sleeve six times for each endoscope.
“What we saw is that when you depressed the flush button you generate greater than 300 mm Hg pressure every time. That’s two-and-a-half to three times the normal systolic blood pressure,” said Dr. White, at the 2014 annual meeting of the American Society of Anesthesiologists (abstract A2058). He noted that, if presented near highly vascular tissue, or where blood vessels are dilated or arterialized—such as in patients with advanced liver disease and portal hypertension—pressures of this level could produce a gas embolus capable of causing complete circulatory compromise in one minute or less.
“We were surprised by the high pressures generated,” he said. “And as we embark on a new horizon of natural orifice transluminal endoscopic surgery, where we leave the endolumen and start dissecting through tissue planes, we need to consider the potential risks along with the benefits of these new procedures. If you think about that high [rate of] pressure being emitted from the tip of an endoscope with sufficient proximity to transmit that gas into the bloodstream, it’s a set up for the development of a fatal gas embolism. And that could happen very quickly at a flow rate of 2 L per minute. This has already been documented in the literature associated with ERCP.”
Given these results, the researchers were quick to make recommendations to possibly improve patient safety. “We endorse the use of carbon dioxide [CO2] instead of air as an insufflating gas. There are practices where people still use air, even though it’s 35 to 50 times less soluble in blood than CO2,” Dr. White said. “We also encourage the future design of endoscopes to allow precise regulation of the maximum gas pressure being emitted from the tip. There is currently no failsafe for the Olympus endoscope, and we think this is something that should be noted.”
Harriet W. Hopf, MD, reminded her colleagues of the best way to treat gas emboli should they occur. “Most gas emboli will cross the pulmonary circulation because of bronchial vessels,” said the professor of anesthesiology at the University of Utah, in Salt Lake City. “So this is a good opportunity to remind us all that if we start seeing more of these, we should get these patients into a hyperbaric chamber immediately. Patients who survive the initial event and are treated with hyperbaric oxygen within 24 hours usually have close to 100% recovery.
“If it’s a CO2 embolism,” she continued, “patients might have an arrest or show some instability, but then they’ll often come right back. They will actually have had endothelial injury and ischemia reperfusion injury, will often wake up fine, and then get worse again. So if they’ve had any kind of a gas embolism, you should consider sending them right to the hyperbaric chamber.”