CO₂ angiography uses carbon dioxide as a gaseous contrast medium to visualise blood vessels, particularly in procedures below the diaphragm. It is a relevant option for patients with chronic kidney disease, or CKD (Chronic Kidney Disease), diabetes, impaired renal function or previous reactions to iodinated contrast media. This pathway is intended for interventional radiologists, vascular surgeons, hospital management and hospital teams seeking to reduce iodine exposure while maintaining a controlled workflow that can be documented.
CO₂ does not automatically replace iodinated contrast media in every examination. The choice depends on the anatomical region, clinical indication, required image quality, the patient's condition and the centre's experience. The decision must be made by the physician responsible for the procedure.
Renal protection encompasses the measures taken to reduce the risk of worsening kidney function during or after a procedure. The assessment considers creatinine, eGFR (estimated Glomerular Filtration Rate), age, diabetes, dehydration, heart failure, potentially nephrotoxic medications and the anticipated amount of iodinated contrast medium.
AKI (Acute Kidney Injury) refers to a rapid decline in kidney function, assessed primarily through changes in creatinine and urine output. The term CIN (Contrast-Induced Nephropathy) is now used with greater caution. In many cases, CA-AKI (Contrast-Associated Acute Kidney Injury) is preferred, because the deterioration may result from multiple factors rather than exclusively from the contrast medium.
An effective renal protection protocol first confirms that the examination is appropriate. Before the procedure, the team assesses kidney function, corrects dehydration where possible and determines the minimum reasonable amount of iodinated contrast medium. It also plans clinical and laboratory monitoring for at-risk patients after the examination.
Hydration must be individualised. In patients with heart failure or a risk of fluid overload, fluids must be managed with particular caution. Changes to treatments such as diuretics, metformin or antihypertensive medications must also be decided by the physician: patients must not stop taking their medications on their own.
CO₂ is a radiolucent gas. When injected into a vessel, it temporarily displaces the blood in the segment being examined and creates negative contrast on angiographic images. The technique is used primarily in the lower-limb arteries, iliac and pelvic regions, haemodialysis vascular access and certain aortic procedures.
The main advantage is the ability to adopt a contrast-sparing strategy, reducing the volume of iodinated contrast medium, or a CO₂-first strategy, using CO₂ as the first imaging modality. In selected cases, a CO₂-only approach without iodinated contrast media is possible, provided that image quality is sufficient to address the clinical question.
Unlike iodinated contrast media, CO₂ is not nephrotoxic and is rapidly eliminated through the lungs. However, safety depends on patient selection, the route of administration, injection volumes and intervals, catheter positioning and compliance with the device's instructions for use.
Image quality may be affected by movement, calcification, slow flow, complex anatomy and overlapping vessels. For this reason, CO₂ may be combined, when indicated, with intravascular ultrasound, fluoroscopy, angiography using a low volume of iodinated contrast medium or other imaging modalities. Reducing iodinated contrast use does not mean compromising diagnostic quality.
The first step is risk stratification. The team identifies patients with CKD, reduced eGFR, diabetes, a kidney transplant, previous episodes of AKI, dehydration or a need for repeated procedures. In complex cases, discussion between the interventional radiologist, vascular surgeon, nephrologist and anaesthetist helps balance the expected benefit against procedural risk.
The second step is to define the contrast strategy: standard iodinated contrast use, reduced iodinated contrast use, CO₂-first or CO₂-only. The decision must take into account the anatomy, urgency, required procedure, necessary image quality and the centre's experience. A written protocol reduces variability between operators and facilitates staff training.
During the procedure, it is useful to record the volume of iodinated contrast medium, the number and volume of CO₂ injections, delivery parameters, image quality, radiation dose and any adverse events. This traceability enables internal audits and improvement assessments, without treating a single outcome as a guarantee for every patient.
After the intervention, the centre can monitor creatinine, eGFR, urine output, symptoms and the need for further procedures. Indicators include AKI incidence, average iodinated contrast volume, length of stay, readmissions, technical quality and the percentage of cases completed using a contrast-sparing strategy.
A system intended for clinical use must be assessed on the basis of its intended purpose, European regulatory documentation, the manufacturer's instructions and consumable compatibility. In Italy, the centre must verify compliance with the applicable requirements of the MDR (Medical Device Regulation), the European Medical Device Regulation 2017/745, as well as CE marking where required.
From a technical perspective, a professional system should allow reproducible control of the main injection parameters, in accordance with the manufacturer-approved specifications:
Automation reduces variability in manual operations and makes the workflow more standardised. However, it does not eliminate the need for clinical expertise: safety also depends on patient selection, vascular access, catheter position, gas handling and adherence to contraindications.
Before purchasing a system, hospital management should request a technical data sheet, declaration of conformity, instructions for use, maintenance plan, consumables management arrangements, local support and a training programme. Angiodroid offers automated digital systems for CO₂ angiography, together with consumables and implementation support; the final assessment nevertheless remains the responsibility of the centre and its clinical engineering team, in accordance with procurement procedures.
CO₂ angiography is used primarily in peripheral vascular procedures below the diaphragm, including lower-limb revascularisation, assessment of haemodialysis vascular access and certain iliac or aortic procedures. At experienced centres, it can support EVAR (Endovascular Aneurysm Repair), i.e. endovascular repair of the aorta, as well as selected fenestrated or branched procedures.
Arterial injection of CO₂ above the diaphragm, such as into the coronary, cerebral or carotid arteries, is generally not indicated because it may carry serious risks. Right-to-left cardiac shunts, arteriovenous malformations, severe pulmonary hypertension, haemodynamic instability and other conditions listed in the device's instructions also require specialist assessment.
CO₂ is a strategy for reducing iodine exposure, not a guarantee of freedom from complications. If the images are inadequate, the physician may add a limited amount of iodinated contrast medium or choose an alternative modality.
The term "iodine allergy" is often imprecise. Reactions to iodinated contrast media may be immediate or delayed, mild or severe, and may involve different mechanisms. It is important to document the product used, the dose, time of onset, symptoms and treatment received.
Nausea, a feeling of warmth or mild itching do not have the same clinical significance as widespread urticaria, bronchospasm, throat swelling, a drop in blood pressure or loss of consciousness. Following a previous reaction, the physician may consider a different contrast medium, premedication where appropriate, an alternative examination or a CO₂-based strategy. Premedication does not eliminate the risk and must not be started without medical advice.
The alternatives depend on the diagnostic question. They may include colour Doppler ultrasound, CO₂ angiography, magnetic resonance imaging with or without contrast media, computed tomography using a reduced volume of iodinated contrast medium or intravascular imaging techniques. No modality is equivalent in every situation: the choice takes into account the anatomy, urgency, kidney function, allergies and the quality of information required.
Effective training is progressive and involves the entire team: interventional radiologists, vascular surgeons, nurses, radiographers and clinical engineering staff. A comprehensive programme includes theory, simulation, live cases, supervised practice, image review and analysis of the centre's first cases.
Angiodroid's Zero-Contrast and CO₂ Journey programmes focus on practical implementation: patient selection, protocol development, system use, image optimisation and outcome measurement. Before enrolling, it is advisable to check the venue, schedule, faculty, professional requirements, availability of continuing education credits and the distinction between device training and professional certification.
For an Italian hospital, the pathway can begin with an assessment of its caseload, iodinated contrast use and renal indicators. Request a workshop, a live case or a clinical demo, specifying the specialty, procedure volume, vascular territories treated and renal protection goals: the team can then define a training and technology pathway suited to the centre's context.
How to implement a CO₂ angiography pathway
Step 1: identify at-risk patients.
Record creatinine, eGFR, comorbidities, previous reactions to iodinated contrast media and the indication for the procedure.
Step 2: define the protocol.
Establish when to use reduced iodinated contrast volumes, CO₂-first or CO₂-only strategies, together with criteria for supplementing CO₂ with iodinated contrast media.
Step 3: train the team.
Train operators in the use of the device and consumables, alarm handling, contraindications and image management.
Step 4: measure outcomes.
Monitor iodinated contrast volume, technical quality, AKI, length of stay, readmissions and the need for additional procedures.
Can CO₂ always replace iodinated contrast media?
No. It is particularly useful in peripheral procedures below the diaphragm, but it is not suitable for every vascular territory or diagnostic question. The physician may add iodinated contrast medium or choose another modality when image quality or safety requires it.
Is CO₂ angiography safe for patients with renal insufficiency?
CO₂ can reduce exposure to iodinated contrast media and help preserve kidney function in selected patients. It does not eliminate all procedural risks: indications, contraindications, the device and monitoring must be assessed by an experienced team.
I have had a reaction to iodinated contrast media: can I have an alternative examination?
Alternatives are often available, but the choice depends on the examination required and the nature of the reaction. The physician may consider CO₂, colour Doppler ultrasound, magnetic resonance imaging, computed tomography using a low volume of iodinated contrast medium or a different contrast agent, always documenting the previous event.
Does premedication always prevent an allergic reaction?
No. Premedication may be considered by the physician in selected situations, but it does not eliminate the risk or replace appropriate examination selection, monitoring and the team's preparedness for emergencies.
Where can I learn CO₂ angiography in Italy?
Training may include workshops, live cases, simulation and mentoring at vascular centres or through specialist programmes. Angiodroid offers Zero-Contrast and CO₂ Journey programmes; it is advisable to request the latest schedule, venue, requirements and course content.
If your centre manages patients with CKD, diabetes, allergies to iodinated contrast media or a need for repeated vascular procedures, a structured assessment can help identify which cases may be suitable for a contrast-sparing strategy. Request an Angiodroid consultation or clinical demo to review the protocol, hardware, training and outcome indicators within the Italian context.