Contrast Media Temperature and Patient Comfort in CT of the Abdomen

Abdominal computed tomography (CT) scans are performed daily on a regular basis. Since its advent, rapid technical advances in CT continuously improved image quality. Besides scan technique, the contrast media (CM) injection protocol is the crucial factor in abdominal imaging. Parenchymal contrast enhancement is determined by patient related factors (e.g. cardiac output, blood volume and patient weight), the CM injection protocol and the scan protocol. Much literature has been performed with regard to optimizing CM application and the scan protocol. Flow rate of the CM and patient discomfort have been thoroughly investigated in our department. Heating CM up to body temperature has been daily clinical routine in our department for years.

According to the recent recommendations (ESUR guidelines 10.0) it is advised to warm iodine-based CM before administration. Warming the CM is expected to result in a higher patient comfort, based on clinical observation. Kok et al. showed in phantom experiments that high temperature, low iodine concentration and low viscosity significantly decreases injection pressure. Subsequently, as increased temperature reduces the viscosity of the CM, the decreased viscosity is hypothesized to reduce the risk of extravasation. A decreased viscosity might also have a substantial impact on individual tailored CM injection protocols in daily routine scanning as it is speculated that a decrease of viscosity and subsequent decrease in peak injection pressure could influence patient comfort during injection. The EICAR trial showed that prewarmed CM can be safely injected at high flow rates, without patient discomfort, pain or stress. However, the latter was not compared to CM at room temperature.

Different CM concentrations are used in different hospitals throughout the world. The higher the concentration, the higher the viscosity of the CM. In present study, only one CM concentrations (e.g. 300 mg/ml) will be used, which is used in daily clinical practice for years. Heating the CM decreases the viscosity. It is therefore expected that the preheated CM in a concentration of 300 mg/ml has a lower viscosity in comparison to the CM at 20° C.

Pre-warming CM might be regarded as best clinical practice. No studies have been performed to investigate this statement, nor is there any literature that shows that prewarmed CM has a favorable patient comfort compared to CM injected at room temperature. For these reasons, there remains to be some reluctance and many clinics still not pre-warm their CM. One study, in which CM is injected in to the cavity of the uterus to check for any anatomical variants and causes for infertility, showed a preference for prewarmed CM in hysterosalpingography (HCG). This study found that prewarmed CM alleviates the pain and decreased the incidence of vasovagal episode during the HCG.

The hypothesis is that although using CM at room temperature (~23°C [~73°F]) might result in lower attenuation of the liver parenchyma than would be achieved using CM pre-warmed to body temperature, diagnostic image quality, patient safety and comfort will not be compromised by not pre-warming CM in this setting. Pre-warming CM requires special equipment and more complex planning and logistics. On the other hand, pre-warming CM may yield higher attenuation levels, comfort and image quality. In case this study does not show a significant difference in patient comfort and diagnostic quality between groups, pre-warming the CM can be stopped, resulting in a considerable simplified workflow.

Inclusion criteria

• Patients referred for abdominal CT
• Patient ≥ 18 years old and competent to sign informed consent

Exclusion criteria

• Hemodynamic instability
• Pregnancy
• Renal insufficiency defined as glomerular filtration rate (GFR) < 30ml/min/1.73m2 (Odin protocol 004720)
• Iodine allergy (Odin protocol 022199)
• Age < 18 year
• Unable to give informed consent or no informed consent obtained
• Inability to position an 18 gauge cannula in an antecubital vein