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1 Department of Radiology, New York Presbyterian Hospital, Weill Medical College
of Cornell University, 520 E 70th St., Starr Pavilion–630, New York, NY
10021.
2 University of Medicine and Dentistry of New Jersey, Robert Wood Johnson
Medical School, 401 Haddon Ave., Camden, NJ 08103.
3 Department of Neurology, New York Presbyterian Hospital, Weill Medical College
of Cornell University, New York, NY 10021.
Received March 2, 2004;
accepted after revision May 6, 2004.
Address correspondence to P. C. Sanelli
(pcs9001{at}med.cornell.edu).
Abstract
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MATERIALS AND METHODS. An in vitro experiment was performed using a 7-French Arrow-Howes multilumen central venous catheter. Each catheter port was tested by varying contrast agent flow rates delivered by a power injector. Contrast media specifications were kept similar to routine clinical practice. The in vivo experiment included 104 cases in which rapid contrast injections, 3.0–5.0 mL/sec, were delivered through a central venous catheter for dynamic CT examinations. Patient monitoring for early complications of contrast extravasation, cardiac arrhythmia, and allergic reactions was performed. Contrast injections were monitored for pressure limitation, automatic flow-rate adjustment, and catheter injury. Chart review was performed for delayed complications of mediastinal hematoma, infection, or catheter malfunction.
RESULTS. During the in vitro experiment, all desired flow rates, 3.0–9.9 mL/sec, could be delivered through the central venous catheter with no catheter injury. No immediate or early patient or catheter complications were observed during the in vivo experiment. Follow-up evaluation revealed that 18 blood cultures and one catheter culture were positive for bacterial growth. In a subgroup of 43 patients, five contrast injections were pressure-limited by the power injector, and only one had the flow rate automatically adjusted to 3.6 mL/sec from 4.0 mL/sec.
CONCLUSION. Rapid contrast injection rates, at 3.0–5.0 mL/sec, through the Arrow-Howes multilumen central venous catheter are feasible and safe in the clinical setting. However, a strict protocol should be followed to avoid possible serious complications.
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Despite the recent need for central venous access for rapid contrast injection, the manufacturers of both power injectors and central venous catheters have made no recommendations regarding the use of the two devices together. Most manufacturers of central venous catheters set guidelines for medication flow rates and inflow pressures for their devices to prevent damage to the catheter or blood vessels. The manufacturer of the Arrow-Howes multilumen central venous catheter (Arrow International) recommends flow rates of less than 1 mL/sec for all three ports and a pressure setting of 15 psi. However, the manufacturer has not yet established maximum pressure recommendations for contrast injections through central venous catheters, which is currently under investigation (Moore M, Arrow International, personal communication). Reports in the literature have shown that injection rates of 1.5–2.5 mL/sec can be used with central venous catheters, despite the manufacturers' guidelines [3, 4]. The purpose of this study was to determine the safety and feasibility of using a central venous catheter for rapid contrast injection rates, at 3.0–5.0 mL/sec.
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In Vivo Experiment
All patients referred to the radiology department at our institution from
July 2002 to November 2003 with a central venous catheter in place for
contrast-enhanced CT examinations requiring injection rates of 3.0 mL/sec and
greater were included in the study. All patients were inpatients at the time
of the procedure. The referring physician determined that it was medically
necessary to perform these examinations in the clinical setting, despite the
lack of peripheral IV access.
This study resulted from the growing demand and strong interest from the clinical services at our institution due to the large volume of ICU patients requiring dynamic CT brain perfusion and angiography on an emergent basis. Therefore, written informed consent was not obtained from these ICU patients. However, institutional review board approval was obtained to perform retrospective analysis regarding catheter and patient complications during the hospital course.
A total of 104 rapid contrast injections were performed for dynamic CT; 81 were for CT brain perfusion, and 23, for CT angiography of the head, neck, and pulmonary vasculature. Two examinations had injection rates at 5.0 mL/sec with a total volume of 45 mL; 79, at 4.0 mL/sec with a total volume of 45 mL; eight, at 4.0 mL/sec with a total volume of 120 mL; and 15, at 3.0 mL/sec with a total volume of 120 mL. Eighty-nine contrast injections were through multilumen central venous catheters, and 15 contrast injections were through percutaneous sheaths placed in the internal jugular vein.
Of a total of 60 patients, 20 required repeated dynamic enhanced CT during their hospital course. In this group, two to four repeated contrast injections were performed through the central venous catheter on a single patient. The age range of patients was 29–89 years old, with a median age of 55 years. Fifty female and 10 male patients were included in the study. Contrast injections using a peripheral catheter are the mainstay policy of our department. Routinely, radiology nurses attempt peripheral IV access before the use of a central venous catheter. The patients included in this study were inpatients in whom adequate peripheral IV access could not be obtained.
The protocol for contrast injection using a central venous catheter in our department of radiology includes an initial anteroposterior scout view of the chest to localize the central venous catheter (Fig. 1). A radiologist selects three to five axial sections using 5.0-mm collimation through the catheter tip to verify its inferior extent and intravascular location (Fig. 2). The anteroposterior scout view is used only to determine the slice location for the axial CT images through the catheter tip.
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Only catheter tips located above the cavoatrial junction were used for contrast injection to avoid potential complications of cardiac injury or arrhythmia from catheter motion or contrast-medium flow during the rapid contrast injection. The distal port, a 16-gauge-diameter lumen, was preferred for the contrast injection because it has the largest diameter bore. A clean technique was implemented in accessing the central venous catheter: alcohol cleansing of the port, using a sterile syringe and saline for flushing and a sterile syringe (Tri-Pak, Medrad) and contrast material; and applying a new luer lock plug at the port upon completion of the injection. The selected port was checked for adequate blood return by the radiology nurse. In accordance with hospital policy, if no blood return was obtained, then the central venous catheter was considered unusable for contrast injection. The contrast tubing was directly attached to the selected port of the catheter, without piggyback extensions. Nonionic contrast material, iodixanol (Visipaque 320, Amersham) was kept at room temperature before injection. For CT brain perfusion, the injection rate was set at 4.0 mL/sec with a 2-sec delay for a total volume of 45 mL of contrast agent. For CT angiography, the injection rate was set at 3.0 mL/sec with a 15- to 20-sec delay for a total volume of 120 mL of contrast agent. A pressure setting of 300 psi was selected for all contrast injections. At the end of the examination, the central venous catheter port was assessed for catheter damage and then flushed with a heparinized saline solution by the radiology nurse.
During the contrast injection, patient monitoring included ECG analysis to evaluate induced cardiac arrhythmias, continuous blood pressure monitoring through a separate arterial catheter, and patient observation for complaints of pain and shortness of breath. All patients were assessed for immediate complications related to the access route, such as contrast extravasation, malfunction of the central venous catheter, or any allergic reaction after the examination. Follow-up was performed during the patient's hospital course through chart review to evaluate catheter and patient complications after the contrast injection. Specifically, we evaluated evidence of infection as documented by findings positive for bacterial growth on blood or catheter cultures and delayed complications of catheter malfunction. The follow-up period had a range of 1–81 days after the contrast-enhanced CT examinations, with a median of 14 days. Short follow-up periods were due to patients' being discharged from the ICU, removal of the central venous catheter, and, occasionally, mortality from unrelated causes.
In Vitro Experiment
Because of the increasing demand from the clinical services to use a
central venous catheter for contrast injections in the ICU patients, we also
performed an in vitro experiment. Power injection of contrast material using a
central venous catheter was evaluated by varying the injection flow rates in a
laboratory experiment. The Arrow-Howes multilumen central venous catheter was
used in all the experiments because it is the standard central venous catheter
used at our institution (Fig.
3). This catheter is a 7-French catheter with three ports,
including an 18-gauge-diameter lumen for the proximal and middle ports and a
16-gauge-diameter lumen for the distal port. Each lumen was individually
evaluated by power injecting contrast material at varying flow rates of 3.0,
4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 9.9 mL/sec, using an Envision CT power
injector (Medrad) (Table 1).
The highest flow rate that can be set on the Medrad power injector is 9.9
mL/sec. A standard pressure setting of 300 psi was selected for all injections
in the experiment. The catheter was freely placed in a water bath maintained
at room temperature. Visipaque 320 nonionic contrast material was used for all
injections and was injected at room temperature, according to the current
departmental policy (contrast material is no longer kept at body temperature).
A total volume of 45 mL of contrast material, the amount used in dynamic CT
perfusion, was administered for each power injection. The contrast injection
specifications in this experiment were kept in accordance with the guidelines
of the department of radiology for routine clinical cases. The catheter was
carefully examined after each injection trial by the nurse and two physicians
performing the experiment.
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We collected data during each injection to determine whether the contrast injection was delivered at the desired flow rate through the central venous catheter, whether the injection reached its maximum pressure settings, whether the flow rate was automatically adjusted by the power injector, and whether the catheter was damaged, including damage to the port–catheter junction and the tip.
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In this experiment, the catheter and the tip were closely inspected visually for signs of damage after each injection by two physicians and a nurse performing the experiment. No catheter damage was seen for any of the contrast injections. Therefore, rapid contrast injection rates were considered safe for the catheter under experimental conditions.
In Vivo Experiment
All patients who presented to the radiology department for CT requiring a
rapid contrast-injection rate could receive their injections through the
central venous catheters. All central venous catheters were easily accessed by
the radiology nurse, with adequate blood return documented. No incidents
occurred in which a central venous catheter could not be accessed because of
catheter malfunction. Successful power injection through the central venous
catheters and dynamic enhanced CT were completed in all patients.
Follow-up evaluation and chart review were performed after the contrast injection through the central venous catheter within a mean of 17 days (range, 1–81 days). At injection rates of 3.0 (n = 15), 4.0 (n = 87), and 5.0 (n = 2) mL/sec, we reported none of the following complications: immediate, early, or delayed patient allergic reactions; induration at the catheter insertion site; contrast extravasation; chest pain; shortness of breath; or cardiac arrhythmia. No evidence of development of mediastinal hematoma was documented in the charts. However, follow-up chart review revealed that a total of 86 blood cultures and 11 catheter tip cultures were performed after removal of the central venous catheter. Eighteen blood cultures and only one catheter culture were positive for bacterial growth. A total of 13 patients (21.7%) had positive blood cultures during their ICU course.
No early or delayed complications were reported relating to the catheter, such as catheter rupture, leakage, occlusion, or breakage at the port–catheter junction or tip. No evidence of contrast extravasation was noted at the catheter insertion site. In a subgroup of 43 cases (41%), the exact pressure applied through the central venous catheter was carefully monitored and recorded. Five of the 43 cases were pressure-limited by the Medrad power injector, with the limitation of the pressure setting ranging from 306 to 316 psi. All these cases were CT brain perfusion examinations with an injection rate set at 4.0 mL/sec. Only one case resulted in an automatic adjustment of the injection rate down to 3.6 mL/sec. Therefore, only one rapid contrast injection could not be delivered at the flow rate selected because of pressure limitations.
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Power injection of contrast material has become a routine part of many CT protocols for the brain, chest, abdomen, and pelvis. The power injection ensures uniformity and predictability of contrast injections among CT examinations. In addition, higher flow rates can be reliably achieved for dynamic CT protocols. It is expected that the pressure generated by a power injector is more predictable and consistent than that produced during a hand injection [5]. Greater variability was found in the rate and pressure achieved during the course of the injection when a contrast material bolus was administered by hand [5]. At each flow rate, intraluminal catheter pressures increased rapidly to a steady state and the pressures increased linearly with increasing flow rates [6]. The complication rate with power injectors is significant but small, with contrast extravasation being the most frequent complication reported [7–9]. The current models of power injectors allow a pressure limit to be set so that the injection rate is automatically reduced or the injection is terminated when a set pressure limit is reached. This limit may also act as an added safety measure for using the power injector with a central venous catheter to prevent catheter or vessel injury. However, currently there are no set recommendations for using these two devices together.
Data regarding the feasibility and safety of power injection of contrast material through central venous catheters are limited. Current reports have not used rates higher than 2.5 mL/sec [3]. Many radiologists are hesitant to use central venous catheters for rapid contrast injections because of potential complications, including contrast extravasation, mediastinal hematoma, cardiac arrhythmia, and catheter rupture and obstruction. Power injection of contrast material through central venous catheters using low flow rates has been shown to be technically feasible without damaging the catheter while remaining within the manufacturer's guidelines for pressure limits at the catheter connection site [4–6, 10]. The complication and infection rates are low for central venous catheters [11]. Early and delayed complication rates were not statistically different when comparing peripherally and centrally placed IV catheters for contrast injection [3]. Overall in our study, the total number of complications was low, and most were considered infectious types of complications. Results of 18 blood cultures were positive, and findings of only one catheter tip culture were positive. These positive blood and catheter culture findings may not necessarily be due to contrast injection using the central venous catheter, given that these patients were in the ICU receiving multiple drug therapies through the same catheter. The reported percentage of positive blood cultures drawn from central venous catheters or peripheral venipuncture or both in the medical and surgical ICU population is 21.7–28.7% [12, 13]. The positive blood culture rate in our study population (21.7%) is consistent with previously published reports in the literature. Therefore, it is difficult to determine if these positive blood cultures were due to the central venous catheter access or if even the one positive catheter culture was due to the single contrast injection the patient received for dynamic CT.
It has been also reported that injections through the Bardport and triple-lumen Hickman catheters resulted in less vascular enhancement of the pulmonary artery and thoracic aorta [3], likely because of the reduced concentration of contrast material and the slower flow rates used with the central venous catheters compared with the peripheral catheters. Manufacturers recommend slower flow rates and less concentrated contrast media for central venous catheter injections so that the catheters remain within pressure guidelines they set and damage to the device or blood vessels is avoided [3]. Less concentrated contrast material used with central venous catheters is less viscous, thus reducing the pressure generated at equivalent flow rates [5]. However, central injection of contrast material shortens the time to peak enhancement and improves vascular enhancement when compared with peripheral IV catheter injection [11]. In our in vitro and in vivo experiments, it was feasible to deliver contrast material through central venous catheters at the same flow rates, total contrast volume, and contrast concentration compared with peripheral IV contrast injections without causing pressure limitations severe enough to automatically adjust to a slower flow rate. Therefore, similar or improved vascular and organ enhancement can be achieved using central venous catheters for contrast administration.
There are several limitations of this study. The in vitro and in vivo experiments did not include the effects of different catheter lengths. Shorter catheter lengths generate lower intraluminal pressures according to Poiseuille's law. This limitation may account for the different pressures generated in the central venous catheters among the patients in our study. In addition, the in vivo study included a small group of patients who had a single type of catheter. The Arrow-Howes multilumen central venous catheter and percutaneous sheaths were used in our study because they are the standard multilumen catheters used at our institution for inpatients. Therefore, outpatients with other catheter types were not evaluated. The study also did not include pediatric patients, whose central catheters have smaller luminal diameters. Therefore, this information cannot be uniformly translated to other catheter types, and each central venous catheter should be evaluated individually to determine its safety before clinical use.
Another consideration not included in the study is that repeated manipulations and long-term use of the catheter may result in greater risk of catheter injury during a rapid contrast injection rate. Even though 20 patients (33%) had multiple contrast injections through the central venous catheter, this parameter was not specifically evaluated.
In addition to the catheter limitations posed in the study, only a single type of contrast media was used in both the in vitro and in vivo experiments. Visipaque 320 is a highly viscous contrast agent that is iso-osmolar with blood. The contrast media was not warmed to body temperature to lower the viscosity and reduce the pressures generated during the injection because implementing this step is no longer the practice in our department. Therefore, the results in this study may vary when using other types of contrast media, particularly those with higher osmolality.
Another limitation is that only 45-mL total volume of contrast medium was used in the in vitro and in many of the in vivo studies. This amount of contrast agent was used to correlate with the amount used for CT brain perfusion; this technique was in greatest clinical demand for assessing our ICU patients. However, larger volumes of contrast agent may have different effects on the catheter. Careful catheter inspection was performed visually in both the in vitro and in vivo experiments. Microscopic evaluation was not performed to detect tiny tears. However, follow-up chart review revealed no delayed catheter complications.
It is not possible to generalize these results to all types of central venous catheters because of the differences in manufacturers' limitations, materials, lengths used, and luminal diameters. We encourage each institution to individually test the central venous catheters and contrast media most commonly used in the radiology department. Alternatively, in the future, manufacturers may also provide pressure limits and flow-rate recommendations for a range of contrast media of different viscosities for the power injector with each catheter package. Either one of these measures should be taken to satisfy the growing demands of dynamic CT in patients with only central venous catheter access.
One reservation concerning the widespread application of using central venous catheters for rapid contrast injection rates is that minimal or no set guidelines are provided for physicians or nurses in the radiology department. Although we have shown that contrast injection rates as high as 3.0–5.0 mL/sec can be safely administered via the power injector through Arrow-Howes multilumen central venous catheters, a strict protocol must be used to minimize catheter and patient complications. If power injection through central venous catheters is to become commonplace in radiology departments across the country, there is the potential for some serious complications to occur because of the large number of personnel with varying skill levels and the large volume of CT examinations performed.
Our current departmental protocol for power injection through a central venous catheter is included in the Materials and Methods section. Documentation of adequate blood return and visualization of placement of the catheter tip above the cavoatrial junction and its intravascular location are necessary. We do not consider rapid contrast injection rates through central venous catheters to be a routine method for delivering contrast material; therefore, this protocol is supervised by a radiologist to ensure accurate catheter location and to limit patient complications.
Because of the growing demand from clinical services to perform dynamic CT in patients with only central venous access, this study may serve as an example for setting guidelines for clinical use at other institutions. In our experience, rapid contrast injection rates, at 3.0–5.0 mL/sec, through the Arrow-Howes multilumen central venous catheter are feasible and safe in the clinical setting. However, a strict protocol should be followed to avoid possible serious complications.
Acknowledgments
We thank Deborah Fitzpatrick for her support and dedication during this
research study.
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