Illustration of CO2 embolism risk during transanal TME surgery.

CO2 Embolism During Transanal TME: What Surgeons Need to Know

Rhea Morgan in Health & Wellness October 2026 • 4 min read.

"A Deep Dive into Causes, Prevention, and Management Strategies for a Rare but Serious Complication."

Transanal Total Mesorectal Excision (taTME) has revolutionized colorectal surgery, offering new hope for patients needing complex procedures. However, with any innovative technique comes a learning curve and the potential for unexpected complications. One such concern is carbon dioxide (CO2) embolism, a rare but serious event that can occur during the transanal phase of taTME.

While CO2 embolism is a known risk in laparoscopic surgery, it's considered negligible. Its occurrence during taTME, therefore, raises important questions about the unique factors at play. Recent studies have highlighted a few cases, prompting a closer look at the underlying causes and how to prevent them.

This article delves into the complexities of CO2 embolism during taTME, exploring the potential reasons behind its occurrence and offering practical strategies for surgeons to minimize this risk. Understanding these nuances is crucial for maximizing the benefits of taTME while ensuring the highest standards of patient safety.

Unmasking the Culprits: Why CO2 Embolism Occurs During taTME

Illustration of CO2 embolism risk during transanal TME surgery.

The exact cause of CO2 embolism during taTME is likely multifactorial, involving a combination of factors that create a perfect storm. Let's break down the key elements that can contribute to this complication:

One potential mechanism involves small veins within the "pneumo-pelvis," the space created by insufflation during the procedure. Partial venotomy, or a nick in a small vein, can lead to splinting of the afferent and efferent ends. This creates an open portal for CO2 to enter the bloodstream, especially if the vein doesn't fully collapse.

Pneumo-pelvis Pressure: The pressure within the pneumo-pelvis can prevent small veins from collapsing completely when cut.
AirSEAL® and Suction: The use of AirSEAL® for insufflation, combined with liberal suction, can create rapid changes in flow rates, promoting turbulent CO2 flow and increasing the likelihood of embolism.

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Latest Research

Pressure Gradients and Embolism Risk

The case report and literature review explains that pelvic venous pressure falls when the surgical field is above the heart, increasing the pressure gradient during CO₂ insufflation at 15–17 mmHg. It cites one study finding that a gradient of 5 mmHg is sufficient for CO₂ to enter the venous system. The review also reports that the degree of Trendelenburg positioning was directly related to the rate of CO₂ embolism.

Counterpoints

Incidence Remains Unknown

The report titled “CO2 embolism can complicate transanal total mesorectal excision” states that the incidence of CO₂ embolism in this setting is unknown. It evaluates three cases of intraoperative embolism during the transanal portion of TME dissection. These cases document the complication, but the report does not establish how frequently it occurs.

Comparison

A Procedure-Specific Review

A 2018 source describes taTME as a relatively new approach for low rectal cancer that uses subperitoneal CO₂ to create the pelvic workspace and perform the operation from the anal side. A review published May 6, 2022, examined CO₂ embolism during taTME alongside reports of embolism in laparoscopic procedures. It presents its work as a comprehensive account of etiology and pathophysiology and recommends tools for monitoring CO₂ embolism during taTME.

Understanding these factors allows surgeons to implement strategies that minimize the risk of CO2 entry into the venous system.

Practical Steps to Minimize CO2 Embolism Risk

While CO2 embolism is a rare complication, taking proactive steps is essential to protect patients during taTME procedures. By understanding the underlying causes, surgeons can implement strategies to minimize risk:

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Expert View

Interpret Cases With Caution

A report on CO₂ embolism during taTME states that the incidence is unknown and evaluates three intraoperative cases. The cases occurred during the transanal portion of TME dissection. They establish that embolism has been reported in this setting, but do not provide an incidence estimate.

Real-World Impact

Two Reported Intraoperative Events

A 2020 case report describes taTME as requiring high-flow transanal CO₂ insufflation to create a working space. It reports CO₂ embolism in two patients scheduled for taTME. Both events occurred during anterior mesorectal dissection in contact with the prostate.

Applying gentle pressure with a gauze square during dissection, especially in the anterior region, can effectively aid haemostasis and reduce the need for aggressive suction. This approach minimizes turbulent CO2 flow and reduces the risk of venous entry.

By incorporating these strategies into their practice, surgeons can confidently offer the benefits of taTME while minimizing the risk of CO2 embolism. Continuous learning and adaptation are crucial for maximizing patient safety in this evolving surgical landscape.

Observed findings alongside a monitored event

4.8 %An intraoperative right-atrial bubble was observed in 4.8% of patients monitored with transesophageal echocardiography.^[1]

What the sources add about taTME embolism

The operative setting differs from conventional laparoscopy: taTME creates its working space through dissection and may use both transanal and transabdominal insufflation. That makes the developing pelvic workspace part of the context for interpreting embolism reports.^[2]

Reported physiological changes included abrupt decreases in end-tidal carbon dioxide, oxygen saturation, and blood pressure. The records also describe release of the insufflated pelvic space and hemodynamic support as part of management; these observations do not establish which measure was responsible for recovery.^[3]

How taTME reports compare with other settings

Laparoscopic reports offer a comparator, but their reported frequencies vary across settings and methods. The figures below are not directly interchangeable, and the vein-harvesting result specifically involved transesophageal echocardiography monitoring.^{[1] [4]}

Some laparoscopic series may have missed less significant events recorded only as comments in anesthesia records; that observation concerns laparoscopy and should not be treated as a taTME-specific estimate. Separately, taTME is described as using high-flow insufflation in a low-volume operative field.^{[3] [4]}

Work	Metric	Value
Laparoscopic surgery	Reported CDE frequency	0.0014–0.6 %^[1]
Gynecologic laparoscopic procedures	CDE cases among procedures	0.59 %^[4]
Closed-entry laparoscopies	Carbon dioxide emboli among procedures	0.001 %^[4]
Endoscopic saphenous vein harvesting	Carbon dioxide emboli among patients monitored with TEE	17.1 %^[4]

What further evidence would need to clarify

How consistently do retrospective reports and institutional reviews capture events that are noticed during surgery but not fully characterized in the records?^{[3] [5]}
How often do echocardiography findings occur without obvious changes in oxygen saturation or blood pressure, as in the reported monitored event?^[1]

Sources

Detection of carbon dioxide embolism by transesophageal echocardiography during transanal/perineal endoscopic surgery: a pilot study (pmc.ncbi.nlm.nih.gov)
Carbon Dioxide Embolism During Transanal Total Mesorectal Excision: Case Report and Literature Review (pmc.ncbi.nlm.nih.gov)
CO2 embolism can complicate transanal total mesorectal excision. (pubmed.ncbi.nlm.nih.gov)
Carbon Dioxide Embolism during Laparoscopic Surgery (pmc.ncbi.nlm.nih.gov)
Carbon Dioxide Embolism Associated With Transanal Total Mesorectal Excision Surgery: A Report From the International Registries. (pubmed.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

What exactly is CO2 embolism in the context of transanal Total Mesorectal Excision (taTME)?

CO2 embolism is a rare but serious complication that can occur during transanal Total Mesorectal Excision (taTME). It involves carbon dioxide (CO2) entering the bloodstream during the transanal phase of the surgery. This can lead to significant health problems. This is especially concerning because it's not typically a risk in laparoscopic procedures. Understanding the factors involved is crucial for patient safety during taTME.

What are the main reasons why CO2 embolism might occur during taTME?

The factors contributing to CO2 embolism include the pressure within the "pneumo-pelvis," the space created during the procedure. This pressure can prevent small veins from collapsing when cut. Additionally, the use of AirSEAL® for insufflation and liberal suction can cause rapid changes in flow rates, promoting turbulent CO2 flow. These elements can create an open portal for CO2 to enter the bloodstream increasing the risk of embolism.

How does the pressure within the "pneumo-pelvis" contribute to the risk of CO2 embolism?

The "pneumo-pelvis" pressure during taTME plays a significant role in CO2 embolism. This pressure, along with partial venotomy, can lead to splinting of the veins. This, combined with rapid changes in flow rates from AirSEAL® and suction, can cause CO2 to enter the bloodstream. The venous system's open portal created by these factors is the primary concern.

What steps can surgeons take to reduce the risk of CO2 embolism during a taTME procedure?

Surgeons can minimize the risk of CO2 embolism during taTME by understanding the causes and implementing strategies to mitigate them. While the text does not explicitly state these strategies, it emphasizes the importance of recognizing the risks associated with "pneumo-pelvis" pressure, partial venotomy, and the use of AirSEAL® and suction. Further research into these areas can guide the development of better practices.

Why is it important to understand CO2 embolism in the context of taTME?

Transanal Total Mesorectal Excision (taTME) is a surgical procedure that has revolutionized colorectal surgery. It offers new hope for patients. A major concern of taTME is CO2 embolism. Understanding and addressing this complication is essential to maximize the benefits of taTME while ensuring the highest standards of patient safety during the procedure.