Peripheral intravenous power injection of iodinated contrast media: the impact of temperature on maximum injection pressures at different cannula sizes

Development of a method to measure regional perfusion of the lung in anesthetized ponies using computed tomography angiography and the maximum slope model

OBJECTIVE

To develop a method based on CT angiography and the maximum slope model (MSM) to measure regional lung perfusion in anesthetized ponies.

ANIMALS

6 ponies.

PROCEDURES

Anesthetized ponies were positioned in dorsal recumbency in the CT gantry. Contrast was injected, and the lungs were imaged while ponies were breathing spontaneously and while they were mechanically ventilated. Two observers delineated regions of interest in aerated and atelectatic lung, and perfusion in those regions was calculated with the MSM. Measurements obtained with a computerized method were compared with manual measurements, and computerized measurements were compared with previously reported measurements obtained with microspheres.

RESULTS

Perfusion measurements obtained with the MSM were similar to previously reported values obtained with the microsphere method. While ponies were spontaneously breathing, mean ± SD perfusion for aerated and atelectatic lung regions were 4.0 ± 1.9 and 5.0 ± 1.2 mL/min/g of lung tissue, respectively. During mechanical ventilation, values were 4.6 ± 1.2 and 2.7 ± 0.7 mL/min/g of lung tissue at end expiration and 4.1 ± 0.5 and 2.7 ± 0.6 mL/min/g of lung tissue at peak inspiration. Intraobserver agreement was acceptable, but interobserver agreement was lower. Computerized measurements compared well with manual measurements.

CLINICAL RELEVANCE

Findings showed that CT angiography and the MSM could be used to measure regional lung perfusion in dorsally recumbent anesthetized ponies. Measurements are repeatable, suggesting that the method could be used to determine efficacy of therapeutic interventions to improve ventilation-perfusion matching and for other studies for which measurement of regional lung perfusion is necessary.

Warmed contrast media temperature loss in traditional manifold systems during angiographic procedures

BACKGROUND

Extrinsic warming of contrast media (CM) to 37 °C before angiographic procedures is performed to improve bolus kinetics and avoid potential adverse effects. Extrinsically warmed CM readily loses temperature after removal from the warming cabinet, but the extent of its cooling has not been previously investigated.

PURPOSE

To assess temperature loss of extrinsically warmed CM in tubing of traditional angiographic manifolds during simulated angiography.

MATERIAL AND METHODS

In total, 35 scheduled diagnostic angiographic procedures were observed in a hospital setting. Relevant time points of CM use during the procedures were recorded. The shortest, median, and longest procedures were then simulated in the experimental laboratory to measure CM temperatures at specific times at three locations along the tubing system.

RESULTS

The angiographic procedures lasted 7.0-26.6 min (median = 11.7 min), with the total duration dependent primarily on the time from contrast being removed from the warming cabinet to the commencement of imaging. During the simulated procedures, consistent patterns of temperature loss were observed. By the last simulated angiographic run, injected CM temperature decreased by 7.4-16.4 °C, depending on procedure length. Most of the heat loss occurred in the tubing between the CM bottle and coronary control syringe.

CONCLUSION

During angiographic procedures, prewarmed CM loses its temperature rapidly with the duration of exposure to ambient room temperature. If no additional measures are employed to maintain its temperature outside of the warming cabinet, extrinsic warming has limited impact on injected CM temperature.

Effect of Extrinsic Warming of Low-Osmolality CT Contrast Media (Iohexol 350) on Extravasations and Patient Reaction Rates: A Retrospective Study

Background: Extrinsic warming of iodinated CT contrast media to body temperature reduces viscosity and injection pressures. However, studies examining the effect of extrinsic warming on clinical adverse events are limited in number and provide conflicting results. Therefore, consensus practice recommendations have been sparse. Objective: To compare rates of extravasation, allergic/allergic-like reactions, and physiologic reactions between iohexol 350 warmed to body temperature (37°C) and maintained at room temperature. Methods: This retrospective study compared adult patients who received CT examinations using IV iohexol 350 that had either been warmed to body temperature or maintained at room temperature. At our institution, contrast media had historically been warmed to body temperature prior to a protocol change unrelated to this investigation. Patient and CT examination characteristics were extracted from the electronic medical record. Adverse events, including extravasations, allergic/allergic-like reactions, and physiologic reactions, were compared between groups. Results: A total of 3939 patients received contrast media warmed to body temperature before the protocol change; 3933 patients received contrast media at room temperature after the protocol change. The body temperature group experienced 11 (0.28%; 95% CI 0.14%, 0.50%) adverse events, all extravasations; allergic/allergic-reaction rate was 0.00% (97.5% CI 0.00%, 0.09%). The room temperature group experienced 17 (0.43%; 95% CI 0.25%, 0.69%) adverse events [13 (0.33%; 95% CI 0.17%, 0.56%) extravasations; 4 (0.10%; 95% CI 0.03%, 0.26%) allergic/allergic-like reactions]. No physiologic reaction occurred in either group. The two groups were not different in terms of overall reaction rate (p=.19), extravasation rate (p=.69), allergic/allergic-like reaction rate (p=.06), or physiologic reaction rate (p>.99). Logistic regression adjusting for patient and CT characteristics (age, sex, conventional CT vs CTA, contrast media volume, injection location, needle gauge) showed no significant association of patient group and adverse reaction rate (odds ratio=2.19, 95% CI 0.68-7.00). Multivariable regression modeling demonstrated an excess of 0.27 adverse events per 100 patients within the room temperature group, below a 0.6% non-inferiority margin. Conclusion: The data suggest that maintaining iohexol 350 at room temperature is non-inferior to warming the agent to body temperature before injection. Clinical Impact: The resources involved to prewarm iohexol 350 before injection may not be warranted.

Applying a New CT Quality Metric in Radiology: How CT Pulmonary Angiography Repeat Rates Compare Across Institutions

OBJECTIVES

To quantify overall CT repeat and reject rates at five institutions and investigate repeat and reject rates for CT pulmonary angiography (CTPA).

METHODS

In this retrospective study, we apply an automated repeat rate analysis algorithm to 103,752 patient examinations performed at five institutions from July 2017 to August 2019. The algorithm identifies repeated scans for specific scanner and protocol combinations. For each institution, we compared repeat rates for CTPA to all other CT protocols. We used logistic regression and analysis of deviance to compare CTPA repeat rates across institutions and size-based protocols.

RESULTS

Of 103,752 examinations, 1,447 contained repeated helical scans (1.4%). Overall repeat rates differed across institutions (P < .001) ranging from 0.8% to 1.8%. Large-patient CTPA repeat rates ranged from 3.0% to 11.2% with the odds (95% confidence intervals) of a repeat being 4.8 (3.5-6.6) times higher for large- relative to medium-patient CTPA protocols. CTPA repeat rates were elevated relative to all other CT protocols at four of five institutions, with strong evidence of an effect at two institutions (P < .001 for each; odds ratios: 2.0 [1.6-2.6] and 6.2 [4.4-8.9]) and somewhat weaker evidence at the others (P = .005 and P = 0.011; odds ratios: 2.2 [1.3-3.8] and 3.7 [1.5-9.1], respectively). Accounting for size-based protocols, CTPA repeat rates differed across institutions (P < .001).

DISCUSSION

The results indicate low overall repeat rates (<2%) with CTPA rates elevated relative to other protocols. Large-patient CTPA rates were highest (eg, 11.2% at one institution). Differences in repeat rates across institutions suggest the potential for quality improvement.

Computed Tomography Angiography With High Flow Rates: An In Vitro and In Vivo Feasibility Study

OBJECTIVE

The aims of this study were to test high-flow application of contrast media (CM) using novel high-flow needles and to assess injection- and flow-related parameters in a circulation phantom and in an in vivo population.

MATERIALS AND METHODS

A circulation phantom simulating physiological parameters was used. Preheated CM (300 mg/mL) was injected at flow rates varying between 5 and 15 mL/s through a novel 18-gauge high-flow intravenous injection needle. In addition, feasibility of these high-flow needles was tested with administration of flow rates of 9 mL/s in 20 patients referred for pre-transcatheter aortic valve implantation assessment. Injection parameters (eg, peak pressures, peak flow rates) in both phantom and in vivo setup were continuously monitored by a data acquisition program. Attenuation at predefined levels of the aorta (eg, aortic root to common femoral arteries) was measured in all patients to determine clinical applicability.

RESULTS

In the phantom setup, injection rates up to 15 mL/s were feasible. An enhancement plateau was reached at 11 mL/s (464 [20] HU). In patients, no pressure- or flow-related complications (eg, extravasation) were recorded (mean [SD] peak pressure, 154 [8] psi; mean [SD] peak flow rate, 9.2 [0.1 mL/s; range, 9.1-9.6]). Diagnostic attenuation values were reached at all predefined levels of the aorta (330.8 [113.1] HU to 622.9 [81.5] HU).

CONCLUSIONS

These results indicate that injections with 9 mL/s using high-flow injection needles are safe. The pressure limit of 325 psi was not reached, and the injections resulted in diagnostic attenuation values. Using this dedicated needle, high flow rates should not be considered a drawback for CM application in routine CT angiography examinations.

Influence of contrast media viscosity and temperature on injection pressure in computed tomographic angiography: a phantom study

PURPOSE

Iodinated contrast media (CM) in computed tomographic angiography is characterized by its concentration and, consecutively, by its viscosity. Viscosity itself is directly influenced by temperature, which will furthermore affect injection pressure. Therefore, the purposes of this study were to systematically evaluate the viscosity of different CM at different temperatures and to assess their impact on injection pressure in a circulation phantom.

MATERIALS AND METHODS

Initially, viscosity of different contrast media concentrations (240, 300, 370, and 400 mgI/mL) was measured at different temperatures (20°C-40°C) with a commercially available viscosimeter. In the next step, a circulation phantom with physical conditions was used. Contrast media were prepared at different temperatures (20°C, 30°C, 37°C) and injected through a standard 18-gauge needle. All other relevant parameters were kept constant (iodine delivery rate, 1.9 g I/s; total amount of iodine, 15 g I). Peak flow rate (in milliliter per second) and injection pressure (psi) were monitored. Differences in significance were tested using the Kruskal-Wallis test (Statistical Package for the Social Sciences).

RESULTS

Viscosities for iodinated CM of 240, 300, 370, and 400 mg I/mL at 20°C were 5.1, 9.1, 21.2, and 28.8 mPa.s, respectively, whereas, at 40°C, these were substantially lower (2.8, 4.4, 8.7, and 11.2 mPa.s). In the circulation phantom, mean (SD) peak pressures for CM of 240 mg I/mL at 20°C, 30°C, and 37°C were 107 (1.5), 95 (0.6), and 92 (2.1) psi; for CM of 300 mg I/mL, 119 (1.5), 104 (0.6), and 100 (3.6) psi; for CM of 370 mg I/mL, 150 (0.6), 133 (4.4), and 120 (3.5) psi; and for CM of 400 mg I/mL, 169 (1.0), 140 (2.1), and 135 (2.9) psi, respectively, with all P values less than 0.05.

CONCLUSIONS

Low concentration, low viscosity, and high temperatures of CM are beneficial in terms of injection pressure. This should also be considered for individually tailored contrast protocols in daily routine scanning.

I.v. contrast administration with dual source 128-MDCT: a randomized controlled study comparing 18-gauge nonfenestrated and 20-gauge fenestrated catheters for catheter placement success, infusion rate, image quality, and complications

OBJECTIVE

The purpose of this study was to compare the performance of a 20-gauge fenestrated catheter with an 18-gauge nonfenestrated catheter for i.v. contrast infusion during MDCT.

SUBJECTS AND METHODS

Two hundred five adult outpatients imaged on a dual-source 128-MDCT scanner with arterial phase body CT (flow rates, 5.0-7.5 mL/s) were randomized to either an 18-gauge nonfenestrated or 20-gauge fenestrated catheter. After randomization, any 18-gauge nonfenestrated subjects whose veins were deemed insufficient for that catheter gauge were assigned to a third cohort for placement of a 20-gauge fenestrated catheter. Catheter placement success, infusion rate, contrast volume, maximum pressure, complications, and aortic enhancement levels were recorded.

RESULTS

Catheters were placed on the first attempt in 97% (100/103) for 18-gauge nonfenestrated and 94% (96/102) for 20-gauge fenestrated placements and in two or fewer attempts in 99% of both groups. Mean infusion rates (5.74 mL/s for 18-gauge nonfenestrated and 5.58 mL/s for 20-gauge fenestrated placements) and aortic enhancement levels were not significantly different. Maximum pressure was higher with 20-gauge fenestrated catheters (mean ± SD, 230.5 ± 27.6 pounds per square inch [psi]) than 18-gauge nonfenestrated catheters (mean ± SD 215.6 ± 32.8 psi) (p = 0.002). One subject with an 18-gauge nonfenestrated catheter had a high-pressure alarm. In the third cohort, a 20-gauge fenestrated catheter was successfully placed in two or fewer attempts in 85% (28/33), with one minor extravasation attributed to vein insufficiency.

CONCLUSION

A 20-gauge fenestrated catheter performs similarly to an 18-gauge nonfenestrated catheter with respect to i.v. contrast infusion rates and aortic enhancement levels and can be placed in most subjects whose veins are deemed insufficient for an 18-gauge catheter.

Catheter insertion for intravenous (IV) contrast infusion in multidetector-row computed tomography (MDCT): defining how catheter caliber selection affects procedure of catheter insertion, IV contrast infusion rate, complication rate, and MDCT image quality

PURPOSE

This study evaluated the effect of intravenous (IV) catheter gauge size on catheter placement, contrast infusion, and image quality for patients undergoing IV contrast-enhanced multidetector computed tomography (MDCT).

MATERIALS AND METHODS

One thousand consecutive adult outpatients undergoing IV contrast-enhanced MDCT and 10 IV insertion CT nurses were observed from IV catheter selection through IV removal. Patients' demographics, number of sticks required, catheter gauge during each attempt, time for catheter placement, IV nurses' assessment of vein quality and contrast infusion parameters were recorded. Scan quality was assessed subjectively.

RESULTS

Subjects included 547 men and 453 women, with a mean age 59.2 years (range, 19-92 years). Median number of catheter attempts was 1 per patient (range, 1-9). Catheters were successfully placed in 98%. First and final catheters were most commonly 20 gauge (59% and 56%, respectively), followed by 22 gauge (34% for both), 18 gauge (6% for both), and 24 gauge (2% and 3%, respectively). Mean infusion rate correlated with catheter gauge: 5.3 mL/s for 18 gauge; 3.5 mL/s for 20 gauge; 2.3 mL/s for 22 gauge; and 1.7 mL/s for 24 gauge (P < 0.0001). Target infusion rate of ≥ 3 mL/s was related to catheter gauge (100% of 18 gauge, 71% of 20 gauge, 11% of 22 gauge, and 0% of 24 gauge; P < 0.0001). Nine hundred sixty-eight subjects underwent imaging. Most of the CT examinations (935/968 [97%]) were of acceptable quality.

CONCLUSION

Experienced IV starters usually achieve IV access in one attempt by tailoring IV catheter gauge to vein quality; however, target infusion rates are not likely to be achieved with 22- and 24-gauge catheters, used in nearly 1/3 of the patients in this study.