Volume 42, Issue 4 , Pages 179-182, December 2011
Clinical Implementation of the New MEDRAD XDS Contrast Extravasation Detector for Multidetector Computed Tomography
Article Outline
Abstract
Background
Increased speeds of computed tomography (CT) acquisition and concomitant increased intravenous (IV) bolus injection rates have placed patients at greater risk of contrast extravasation.
Purpose
To assess the efficacy of the MEDRAD XDS extravasation detector by recording the incidence of contrast extravasation in high-risk patients during CT angiography.
Material and Methods
We prospectively collected data on 25 adults ages 45 to 85 years (mean=65 years), all of whom were considered to be at high risk of having a contrast extravasation. All patients underwent CT angiography with power-injected IV contrast injection introduced via an antecubital venous line. Details recorded included patient age and weight, contrast volume, flow rate, maximum injector pressure, image quality, and extravasation incidence and volume. The size of the most commonly used cannula was 20 gauge and the flow rates ranged from 4.0 to 6 mL/second.
Results
The XDS device alerted the clinicians to five episodes of extravasation. These were identified at an early stage of the injection with no more than 8 mL of contrast material having been introduced.
Conclusion
The utility of this device has been demonstrated and its employment should reduce extravasated contrast volumes with minimum discomfort to high-risk patients.
Résumé
Contexte
La vitesse croissante de l’acquisition TDM et l’augmentation concomitante du taux d’injection intraveineuse en bolus exposent les patients à un risque accru d’extravasation de l’agent de contraste.
But
Évaluer l’efficacité du détecteur d’extravasation MEDRAD XDS en enregistrant l’incidence d’extravasation d’agent de contraste chez les patients à haut risque durant l’angiotomodensitométrie.
Méthodes et matériel
Nous avons recueilli de façon prospective des données sur 25 patients adultes âgés de 45 à 85 ans (moyenne de 65 ans), tous considérés à haut risque d’extravasation d’agent de contraste. Tous les patients ont subi une angiotomodensitométrie avec injection intraveineuse sous pression d’agent de contraste par cathéter veineux dans la zone antécubitale. Les données enregistrées comprennent l’âge et le poids du patient, le volume d’agent de contraste, le débit, la pression maximale d’injection, la qualité de l’image ainsi que le taux d’incidence et le volume d’extravasation. La taille de canule la plus fréquemment utilisée était le calibre 20 et le débit variait de 4,0 à 6 ml/s.
Résultats
L’appareil MEDRAD XDS a alerté les cliniciens dans cinq épisodes d’extravasation, qui a été détectée reconnus aux premiers stades de l’injection de 8 ml ou moins d’agent de contraste.
Conclusion
L’utilité de l’appareil et le taux peu élevé d’inconfort du patient ont été démontrés, et son utilisation devrait permettre de réduire le volume d’agent de contraste extravasé chez les patients à haut risque.
Introduction
An extravasation of contrast media during a computed tomography (CT) acquisition is a well-known complication [1]. There is a wide range of consequences of contrast extravasation that are easily understood and recognizable: impact to the patient, radiographer and nurse, scanner schedule, and the potential need for surgical intervention. Although an extravasation is well recognized, the frequency that a technician would see an extravasation varies, ranging from 0.14% to 0.9%, with an average of 0.43% [2], [3], [4], [5], [6], [7]. Higher extravasation rates for CT angiography (CTA) are based on acquisition of data during the arterial phase of contrast material passage [8] because optimum timing of the contrast bolus is required, where the inflow velocity ranges from 3 mL/second to 6 mL/second.
The presentation of extravasation of iodinated contrast media varies from minor erythema and swelling to tissue necrosis associated with progressive edema and skin ulceration. The injuries mainly heal and only rarely lead to long-term injury such as hypoesthesia, marked weakness, and pain [9].
Interestingly according to Jacob et al., the incidence after mechanical bolus injection is higher than that reported for hand-injection or drip-infusion techniques; however, there seems to be no relationship between injection rate and extravasation frequency. The clinical presentation is highly variable. Most extravasations involve small volumes of contrast material and induce minimal swelling or localized erythema, which rapidly diminish. Automated power injection may result in extravasation of large volumes and may lead to compartment syndrome and severe tissue damage [10].
The MEDRAD Extravasation Detection System (XDS; Warrendale, PA, USA) is designed to aid in the detection of intravenous contrast media passing from the injection site into the surrounding tissue during diagnostic studies in CT applications. The system uses low-power, high-frequency electromagnetic energy to detect changes in subcutaneous fluid levels, and when the radio wave-type signal is passed continuously through the tissue the XDS system is activated. A sensor mounted to the patient’s arm measures the strength of this return signal (Figure 1). If signal strength should change, as would happen if fluid began to pool in the subcutaneous tissues, an alarm will sound signaling that an extravasation is occurring. The XDS system is designed to detect a fluid buildup of less than 20 mL of intravenous contrast media and/or saline from the injection site into the surrounding tissue (the actual value is dependent on the injection flow rate and other patient characteristics).
Figure 1
XDS Extravasation Detection System Operation of Radiofrequency waves relative to veins [11]. Top image (before extravasation) demonstrates the radiofrequency waves calibrating the tissue density before contrast administration; bottom image (extravasation) demonstrates the contrast extravasation being detected by changes in radiofrequency pulses from changes in tissue density.
Although the potential of this device for alerting clinicians to early extravasation is clear, few clinical studies have demonstrated its application for high-risk patients undergoing examinations with high-rate bolus injections [6], [7]. This study addresses this deficiency and assesses the efficacy of the XDS device during CTA studies. The detection of extravasation will be recorded, coupled with contrast detection during low-dose timing bolus during CTA.
Materials and Methods
Patient Selection
Informed consent was provided by all patients undergoing a CTA with the XDS contrast extravasation device over a 6-month period. Contraindications for a contrast-enhanced CTA were renal insufficiency (creatinine >120 μmol/L) and reduced estimated glomerular filtration rate (<50 mL/min), hyperthyroidism, and a medical history of allergy-like reactions.
We investigated 25 high risk patients (10 male, 15 female) with a median age of 65 years (range = 45–85 years) who underwent a CTA scan for three reasons: coronary anomalies (n = 10) using a flow rate between 5 and 6 mL/second of contrast material and normal saline; pulmonary artery angiogram for pulmonary embolus detection (n = 10) with the contrast agent introduced at 4.0 mL/second; and abdominal aortic angiogram (n = 5) for infrarenal abdominal aortic aneurysm at a flow rate of 4.5 mL/second of contrast material and normal saline.
There is no literature illustrating risk factors that contribute to subcutaneous extravasation using a mechanical injector. We reviewed the last 1,000 patients who had a contrast extravasation during CTA. In each extravasation event, both patient and technical factors were reviewed and tabulated (Table 1) by allotting common characteristics across all patients that could have contributed to contrast extravasation. All patients in this study displayed at least two of these risk factors to be considered a high-risk category for extravasation.
Table 1. Inclusion Criteria based on the Classification of Patient and Technical Factors, which could have Contributed to Contrast Extravasation during Computed Tomography Acquisition
| Technical factors | Flow rates higher than 3.0 mL/second Cannula in situ > 2 days |
|---|---|
| Patient factors | Unable to communicate Fragile and/or damaged veins Patient hospital stay > 2 weeks Diabetics Chemotherapy Radiotherapy Arterial insufficiency Compromised lymphatic and or venous drainage Connective tissue disorders (i.e., Marfan syndrome) Low muscular mass and atrophic subcutaneous tissue |
Contrast Acquisition
All patients were examined on a Dual Source Computed Tomography (SOMATOM Definition; Siemens Medical Solutions, Forchheim, Germany). In the contrast-enhanced scans, contrast medium volume, injection rate, and injection duration have interrelated effects on the time course of arterial enhancement. Contrast volume was calculated according to duration of acquisition times and also body weight of 0.8 mL/kg.
The contrast delivery system was a MEDRAD Stellant Dual Barrel Power injector with a 325 psi limit. A nonionic low osmolar contrast agent (Iopromide 370 mg/mL) and normal saline flush was used for all examinations.
The preparation of the MEDRAD XDS device involved the cannulation of the antecubital fossa in the right arm using a 20-gauge cannula. The cannula was secured by a double-sided adhesive sensor interface disposable, which acts as a coupling device between the patients arm and the sensor device [10]. After the cannula and sensor interface disposable were secured, the patient sensor was placed over alignment pads that corresponded with the patient sensor pads [10]. Finally, the arm was moved into a secure position and the XDS system was activated.
Results
The XDS system was accurate in detecting all extravasations during the CTA acquisitions. In our department, the rate of contrast extravasation was 0.2% of all contrast CTA acquisitions (database of 1,000 patients), which is in line with previous workers' [1], [2], [3], [4], [5], [6], [7], [8], [9], [10].
Two of the 10 patients scanned with the extravasation device during cardiac CTA acquisition showed an extravasation at the test bolus phase before the cardiac CTA acquisition. Each extravasation event was characterized as a technical error with both cannulas being in the patient’s antecubital fossa for more than 2 days. This test bolus phase consisted of 10 mL of contrast followed by 80 mL of normal saline chaser. On both occasions, the XDS system detected extravasation after injecting ≤5 mL of contrast. This detection can be attributed to a superficial extravasation adjacent to the sensor. In each occasion we determined extravasation during the test bolus, because there was no contrast visible during the timing bolus. However, this also could contribute to a venous valve adjacent to the cannula end and therefore a true extravasation could not be excluded that increased the pressure to mimic an extravasation. The diagnostic scan was performed as a separate injection after the test bolus initially extravasated (Table 2).
Table 2. Sex, Age, Weight, Contrast Dose, Rate, Maximum Pressure, Extravasation Detected and Image Quality Achieved during Cardiac CTA Acquisition
| Patient | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Sex | M | M | M | M | F | F | F | F | F | F |
| Age | 48 | 54 | 45 | 64 | 48 | 49 | 68 | 72 | 81 | 76 |
| Weight (kg) | 84 | 66 | 123 | 97 | 80 | 65 | 95 | 70 | 68 | 62 |
| Contrast dose (mL) | 80 | 56 | 96 | 82 | 60 | 60 | 84 | 62 | 58 | 60 |
| Rate (mL/second) | 5 | 5 | 6 | 6 | 5 | 5 | 6 | 5 | 5 | 5 |
| Maximum pressure (psi) | 240 | 220 | 296 | 290 | 220 | 180 | 230 | 205 | 235 | 215 |
| Extravasation detected | N | N | Y | N | N | N | Y | N | N | N |
Three of the 10 patients scanned with the extravasation device during pulmonary CTA acquisition showed an extravasation during the pulmonary artery acquisition. Each extravasation event demonstrated both technical and patient error. Each patient had a cannula in the antecubital fossa for more than 2 days. Two of three patients were on chemotherapy and the other had a hospital stay longer than 2 weeks. On every occasion, the XDS system detected extravasation after injecting 5–8 mL contrast. In the patients that displayed extravasation, the scan was immediately terminated because of the MEDRAD XDS device. The patients were recannulated and the subsequent scan was performed without complications (Table 3).
Table 3. Sex, Age, Weight, Contrast Dose, Rate, Maximum Pressure, Extravasation Detected and Image Quality Achieved during Pulmonary Artery Angiography
| Patient | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Sex | F | F | M | F | M | F | M | M | F | F |
| Age | 45 | 83 | 84 | 81 | 64 | 66 | 49 | 76 | 73 | 54 |
| Weight (kg) | 79 | 69 | 101 | 77 | 67 | 89 | 109 | 93 | 66 | 85 |
| Contrast dose (mL) | 80 | 70 | 100 | 75 | 72 | 93 | 100 | 100 | 70 | 90 |
| Rate (mL/second) | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
| Maximum pressure (psi) | 150 | 120 | 120 | 135 | 110 | 110 | 180 | 125 | 180 | 140 |
| Extravasation detected | Y | N | N | N | Y | Y | N | N | N | N |
All patients who sustained an extravasation were managed conservatively with ice compression and limb elevation for 2 hours. No extravasation was detected during abdominal CTA acquisition because they were all from the emergency department and each patient presented to radiology with a 18-guage cannula in the antecubital fossa that had been in situ for less than 2 hours (Table 4).
Table 4. Sex, Age, Weight, Contrast Dose, Rate, Maximum Pressure, Extravasation Detected and Image Quality Achieved during Abdominal Aortic Angiography
| Patient | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Sex | M | M | F | F | F |
| Age | 54 | 69 | 78 | 83 | 59 |
| Weight (kg) | 92 | 89 | 90 | 138 | 93 |
| Contrast dose (mL) | 100 | 100 | 100 | 100 | 100 |
| Rate (mL/second) | 5 | 5 | 5 | 5 | 5 |
| Maximum pressure (psi) | 220 | 240 | 240 | 260 | 220 |
| Extravasation detected | N | N | N | N | N |
Discussion
High-flow automated contrast power injectors have been used since 1986 [11]. They are advantageous because they increase image quality and patient throughput, reduce exposure of radiation to staff, and increase the reproducibility of scans [12]. With the substantially improved technological advances in CT, the need for faster injection rates has become vital in imaging to maintain a peak arterial contrast enhancement during CTA. The use of these mechanical devices is linked to higher extravasation rates [10]. However, in published literature there is no correlation between injection rate and the frequency of extravasation [6], [7], [13].
In this study our preliminary results with the XDS system are promising, having demonstrated the system’s ability to detect all cases of early contrast/saline leakage into the tissue and ensuring that no incidences of severe extravasation developed, even though 20% of patients underwent a minimal extravasation. Patients within this latter group were treated conservatively with good clinical outcomes. No compartment syndrome occurred because a maximum of 8 mL contrast was injected. Small volume extravasations are assumed to occur 3% of the time and to be less than 2 mL in volume, based on previous studies [14]. In our study we had two extravasations with less than 5 mL; however, this could not exclude a true extravasation. Key physiologic aspects to consider in patients when performing contrast-enhanced CT scans are associated arterial or venous insufficiency, poor lymphatic drainage, low muscle mass, and subcutaneous tissue atrophy [13], [15]. Setting up and calibrating the extravasation device is a simple process that takes approximately 3 minutes.
Although there are clear benefits to patients in terms of comfort and morbidity, reductions in extravasations can also lead to a reduced economic burden. In addition to reduced treatment costs, the most recently reported legal claims in the United States demonstrated that extravasation accounted for high numbers of successful claims. Moderate extravasations accounted for the minority of cases resulting in award payments ranging from $1,045 to $74,421, whereas severe extravasation awards ranged from $3,294 to $2.9 million [16]. The medical and economic rationale for early detection of extravasations is clear and, although the focus here has been CTA, the potential benefits for other examinations and modalities involved with power injectors should be explored.
This was a preliminary piece of work that demonstrated a number of limitations. First, we did not include a methodology that was designed to test for false positives (extravasation alarm with no extravasation) and false negatives (no extravasation alarm when extravasation occurs). Nonetheless, we do not believe there were false positives because no extravasation was evident after examination of the patients’ injection site. The ideal image quality demonstrated by the CT scans would suggest little contrast media loss to the tissues. With respect to false negatives, these are harder to eliminate because further investigative procedures required to prove the existence of extravascular contrast media in the tissue (such as ionizing radiation or ultrasound) was beyond the scope of this work. This will be the focus of further study. Also, this article is largely a technical report on the incidence of extravasation with the XDS device, therefore detailed statistical analyses were avoided.
Conclusion
Extravasation of contrast material is a reasonably common complication of enhanced imaging studies. Large-volume extravasation may result in severe patient discomfort. Implementation of the XDS device on predetermined high extravasation risk patients has been demonstrated as an important strategy for reducing such extravasations.
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PII: S1939-8654(11)00051-8
doi:10.1016/j.jmir.2011.05.003
© 2011 Elsevier Inc. All rights reserved.
Volume 42, Issue 4 , Pages 179-182, December 2011
