24.3 Interventional Patient Management: Contrast Selection, Pre-Procedure Workup & Post-Procedure Care
Key Takeaways
- Pre-procedure workup for an interventional case covers informed consent, coagulation profile and platelet count, renal function, allergy history, current medications including anticoagulants and metformin, fasting status and intravenous access.
- Low-osmolar and iso-osmolar non-ionic contrast agents are standard for intra-arterial work because they cause less pain, less endothelial and haemodynamic disturbance and fewer adverse reactions than high-osmolar ionic agents.
- Carbon dioxide and gadolinium are alternative contrast agents used below the diaphragm in patients with severe renal impairment or a documented severe iodinated contrast reaction.
- Post-procedure femoral access care requires manual compression or a closure device followed by bed rest with the limb straight, and regular observation of the puncture site, distal pulses, limb colour, temperature, sensation and vital signs.
- The complications the technologist must recognise early are haematoma and retroperitoneal haemorrhage, pseudoaneurysm, arteriovenous fistula, distal embolisation, dissection, contrast-induced nephropathy and vasovagal reaction.
24.3 Interventional Patient Management: Contrast Selection, Pre-Procedure Workup & Post-Procedure Care
The Enhanced TOS gives Patient management and care 3 items within Interventional Radiology, with two competencies: explain the different contrast media used, its advantages and disadvantages, and the mode of administration, and illustrate pre-operative and post-operative nursing care. Sections 24.1 and 24.2 covered access technique, digital subtraction angiography and the interventional procedures themselves. This section is the wrap-around care that makes them safe.
1. Pre-Procedure Assessment
| Domain | What is checked | Why it matters |
|---|---|---|
| Identity and consent | Two identifiers; written informed consent taken by the operator; site and side marked | Wrong-patient and wrong-side procedures are never recoverable |
| Indication and imaging review | Prior CT, MR, ultrasound or angiography reviewed and available in the room | Determines access route, catheter and device selection |
| Coagulation | Prothrombin time / INR, activated partial thromboplastin time, platelet count | Bleeding is the commonest serious complication of a puncture |
| Renal function | Serum creatinine and estimated glomerular filtration rate | Contrast-induced nephropathy risk; may change the agent or the volume |
| Allergy | Iodinated contrast, latex, antiseptic, medications | Determines premedication and preparedness |
| Medications | Anticoagulants and antiplatelets, metformin, insulin, antihypertensives, beta blockers | Anticoagulation may need to be withheld and bridged; metformin is managed per policy |
| Fasting | Typically clear fluids up to about 2 hours, solids about 6 hours, per institutional policy | Sedation and the small risk of emergency conversion to surgery |
| Access | A functioning intravenous cannula; the site chosen away from the working field | Drugs, fluids and emergency access |
| Baseline observations | Blood pressure, heart rate, respiratory rate, temperature, oxygen saturation; distal pulses marked on the limb to be punctured | Post-procedure comparison is impossible without a baseline |
| Pregnancy status | Asked and documented for every female of childbearing potential | Fluoroscopy dose to the uterus |
| Site preparation | Hair clipped, not shaved; skin prepared with an alcohol-based chlorhexidine solution and allowed to dry | Shaving with a razor increases infection risk |
| Antibiotic prophylaxis | Where indicated by procedure type, given within the correct window before puncture | Reduces device and access-site infection |
The team briefing / surgical safety pause immediately before the first incision or puncture confirms patient, procedure, site, allergies, antibiotic timing, anticipated blood loss, equipment availability and any special concern. It is a formal safety step, not a formality.
2. Contrast Media in Interventional Work
Why the choice matters more here than in general radiography
Intra-arterial injection delivers a high concentration of contrast directly to an organ or a limb, so the physicochemical properties of the agent translate directly into patient experience and physiological effect.
| Class | Example characteristics | Advantages | Disadvantages |
|---|---|---|---|
| High-osmolar ionic monomer (HOCM) | Osmolality roughly 5-8 times that of plasma | Cheap; high iodine delivery | Marked injection pain and heat, endothelial injury, volume shifts, higher adverse-reaction rate. Largely abandoned for intra-arterial work |
| Low-osmolar non-ionic monomer (LOCM) | Osmolality roughly 2-3 times plasma | Much less pain and heat; substantially fewer adverse reactions; good opacification | Higher cost than HOCM |
| Iso-osmolar non-ionic dimer (IOCM) | Osmolality approximately equal to plasma | Best tolerated; least pain; favoured in high-risk renal and peripheral work | Higher viscosity, so warming and larger-bore catheters help; highest cost |
The rule: non-ionic low-osmolar or iso-osmolar agents are the standard for intra-arterial and interventional use.
Viscosity matters mechanically. A viscous agent injected through a microcatheter needs higher pressure and a lower flow rate. Warming contrast to body temperature lowers viscosity and improves injection through small catheters.
Alternative contrast agents
| Agent | Use | Cautions |
|---|---|---|
| Carbon dioxide | Digital subtraction angiography below the diaphragm in severe renal impairment or severe iodinated contrast allergy | Never above the diaphragm and never in the cerebral or coronary circulation because of gas embolism risk; requires a dedicated delivery system and image-processing adjustment; buoyant, so it fills anterior structures |
| Gadolinium | Occasional alternative in iodine allergy | Limited iodine-equivalent opacification per unit volume; nephrogenic systemic fibrosis risk in severe renal impairment |
| Dilute contrast | Routine practice in many procedures | Reduces total iodine load while retaining adequate opacification |
Contrast-induced nephropathy: prevention
Identify risk — pre-existing renal impairment, diabetic nephropathy, dehydration, heart failure, advanced age, high contrast volume, and concurrent nephrotoxic drugs. Then: hydrate with intravenous isotonic saline before and after, minimise contrast volume, use LOCM or IOCM, avoid repeated contrast studies within a short interval, and manage metformin according to institutional policy in patients with impaired renal function.
Managing a reaction
Every interventional room must carry oxygen, suction, an emergency trolley with adrenaline (epinephrine), antihistamine, corticosteroid, bronchodilator and intravenous fluids, a defibrillator, and staff trained in basic life support. Adrenaline is the definitive treatment for anaphylaxis; antihistamines and steroids are adjuncts and do not replace it.
3. During the Procedure
- Sterile field discipline. Full barrier precautions for vascular access: cap, mask, sterile gown and gloves, and a large sterile drape. The scrubbed and unscrubbed roles must be explicit and maintained.
- Monitoring. Continuous ECG, pulse oximetry, non-invasive blood pressure and, where sedation is used, capnography and a dedicated person whose sole responsibility is the patient.
- Communication. Talk to the conscious patient: warn before an injection that will cause heat, before a balloon inflation that will cause pain, and before any request to hold still or hold breath.
- Anticoagulation and flushing. Heparinised saline flush of catheters and sheaths prevents thrombus; document systemic heparin dose and time.
- Radiation dose. Record fluoroscopy time and dose-area product or air kerma. Use pulsed fluoroscopy at the lowest acceptable rate, last-image-hold, tight collimation, minimal magnification, and keep the image intensifier or detector as close to the patient as possible while keeping the tube far from the patient. Vary the beam angle in prolonged cases to avoid a deterministic skin injury at one site. Staff wear apron, thyroid shield and eye protection and use the table-side lead curtain and ceiling-suspended screen.
- Documentation. Contrast type and volume, drugs given, devices implanted with lot numbers, complications, and dose metrics.
4. Post-Procedure Care
Haemostasis at a femoral arterial puncture
Manual compression is applied above the arteriotomy for typically 10-20 minutes, longer if the patient is anticoagulated or a large sheath was used, with pressure sufficient to stop bleeding while preserving distal pulses. Alternatively an arterial closure device is deployed. Radial access, increasingly used, permits a compression band and much earlier mobilisation.
The observation regimen
| Element | Standard practice |
|---|---|
| Bed rest | Supine with the punctured limb kept straight; typically about 2-6 hours after femoral arterial access depending on sheath size and anticoagulation; venous punctures need less |
| Observations | Every 15 minutes for the first hour, every 30 minutes for the next 2 hours, then hourly — or per local policy |
| What is observed | Puncture site for bleeding, swelling or haematoma; distal pulses; limb colour, temperature, sensation and movement; vital signs; pain |
| Hydration | Encourage oral fluids or continue intravenous fluids to promote contrast clearance |
| Analgesia | As prescribed; new or increasing pain is a warning sign, not an expected finding |
| Discharge advice | Keep the site clean and dry; avoid heavy lifting, straining and strenuous activity for the stated period; how to apply pressure if bleeding occurs; and when to return urgently |
Complications to recognise early
| Complication | Presentation | Immediate action |
|---|---|---|
| Haematoma | Swelling and bruising at the puncture site | Direct pressure; mark and measure the extent; observe |
| Retroperitoneal haemorrhage | Back or flank pain, hypotension, tachycardia, falling haemoglobin with a deceptively normal-looking groin | Medical emergency — call the operator, resuscitate, urgent CT |
| Pseudoaneurysm | Pulsatile, tender swelling with a bruit | Ultrasound; compression or thrombin injection |
| Arteriovenous fistula | Continuous machinery bruit and thrill | Ultrasound; may need repair |
| Distal embolisation or thrombosis | The six Ps — pain, pallor, pulselessness, paraesthesia, paralysis, poikilothermia (coldness) | Emergency — notify the operator immediately |
| Dissection | Loss of distal flow, limb ischaemia | Emergency imaging and intervention |
| Contrast-induced nephropathy | Rising creatinine at 48-72 hours, falling urine output | Hydration, avoid further nephrotoxins, nephrology input |
| Vasovagal reaction | Bradycardia, hypotension, pallor, sweating, nausea | Lie flat, elevate legs, intravenous fluids, atropine if required |
| Infection | Fever, site erythema and discharge | Cultures, antibiotics |
| Radiation skin injury | Erythema at 1-3 weeks, later epilation or ulceration at the beam entrance site in a prolonged case | Dose review, dermatology referral, document and report |
The technologist's contribution to safety is observational. The person who notices that a groin is quietly swelling, that a foot has become cold and mottled, or that a patient who was chatting has become pale and restless, prevents most of the harm in an interventional service. Escalate early; the operator would rather be called for nothing than late.
Thirty minutes after a femoral arterial angiogram, a patient reports increasing back and flank pain. The groin puncture site appears unremarkable, but the blood pressure has fallen from 130 over 80 to 90 over 55 and the heart rate has risen to 118. What is the most likely complication?
A patient with an estimated glomerular filtration rate of 18 mL per minute requires digital subtraction angiography of the lower limb arteries. Which contrast strategy is appropriate?
Which set of investigations should be available before a percutaneous interventional procedure with arterial access?
Four hours after femoral arterial access, a patient's punctured limb is pale, cool and painful, with absent pedal pulses and new paraesthesia. What is the correct immediate action?