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1
Department of Radiology, Hb6, The Cleveland Clinic Foundation, 9500 Euclid
Ave., Cleveland, OH 44195.
2
Department of Biostatistics, The Cleveland Clinic Foundation, Cleveland, OH
44195.
3
Department of Hematology and Oncology, The Cleveland Clinic Foundation,
Cleveland, OH 44195.
Received December 17, 1999;
accepted after revision July 31, 2000.
Supported in part by Liebel-Flarsheim, Inc., Cincinnati, OH.
Abstract
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SUBJECTS AND METHODS. Two hundred ninety-five CT examinations were performed during an 18-month period in 225 patients with indwelling central venous catheters. Patients were randomized to power injection either through peripheral IV catheter or through central venous catheter. Feasibility was defined as the percentage of patients with contrast material injected successfully through the randomized access route. Safety was evaluated by comparing patients with complications. Efficacy was evaluated by comparing contrast enhancement of the thoracic aorta, pulmonary artery, abdominal aorta, and liver.
RESULTS. Two hundred nine patients had randomization data recorded. One hundred three (94%) of 109 patients were successfully injected through their indwelling catheter compared with 42 (42%) of 100 through a peripherally placed IV catheter (p < 0.001). After reassignment for unsuccessful access, 174 patients underwent central venous catheter injection, and 51, peripheral IV catheter injection. No statistically significant difference was noted in the complications between the central venous catheter and peripheral IV catheter groups. Enhancement was greater in the thoracic aorta, pulmonary artery, and liver for the peripheral IV catheter group (p < 0.03).
CONCLUSION. Power injection of contrast media through central venous catheters for CT examinations is feasible and safe when set hospital guidelines and injection protocols are followed. This technique provides an acceptable alternative in patients without adequate peripheral IV access when bolus contrast enhancement is desired.
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Because many patients requiring central venous catheters have poor peripheral IV access, it is both practical and possibly necessary to administer IV contrast material through the central venous catheter, as well as more convenient for the patient. However, the manufacturers of both power injectors and central venous catheters make no recommendations regarding the use of the two devices together. The radiologist is left to choose among different options for administering IV catheter contrast material to these patients. A peripheral IV catheter can be placed when possible, and contrast material can be injected in a routine manner using a power injector. Contrast material can also be injected by hand or by power injector through the central venous catheter. Alternatively, a non-IV contrast media-enhanced examination can be performed.
Furthermore, no studies have been performed evaluating the efficacy of contrast enhancement when power-injecting contrast material through central venous catheters. Bolus IV contrast enhancement for CT scanning using a power injector is the preferred method for contrast administration for CT examinations of the neck, chest, and abdomen [6,7,8,9,10,11]. IV access is typically achieved by placing an 18- or 20-gauge Angiocath (Becton-Dickinson, Sandy, UT) in an antecubital vein or other large upper extremity vein. However, no studies have been performed comparing the degree of contrast enhancement achieved by power-injecting contrast material through a central venous catheter with that achieved using peripheral IV catheter injection.
The purpose of this study was to determine whether it is feasible to power-inject contrast material through central venous catheters and whether power injectors are safe for administering IV catheter contrast media through central venous catheters. We also sought to determine if contrast media administered through central venous catheters provide adequate contrast enhancement when compared with peripheral IV catheter injection.
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Patients were randomly assigned to receive either insertion of a peripheral IV catheter (peripheral venous access group) or access of their central venous catheter (central venous access group) with the power injection of contrast media through the site of venous access. The protocols used to access each central venous catheter and to assess whether the central venous catheter was patent and suitable for use were determined by preexisting hospital nursing policy. To summarize these protocols, all central venous catheters were accessed using aseptic techniques and were flushed with a heparinized saline solution (unless heparin use was contraindicated) both before and after the examination. In accordance with hospital policy, if no blood was returned from the central venous catheter it was deemed unusable for contrast injection. Port catheters were accessed with 19-gauge hook-type needles (Huber needle; Baxter, Deerfield, IL). Needleless connections (Lever Lock Cannula; Becton Dickinson, Franklin Lakes, NJ) were made with all other catheters types. All patients randomized to the peripheral venous access group underwent at least one attempt at placement of a peripheral IV catheter by an experienced nurse. If this attempt failed, a second attempt was made by the same or another experienced nurse if an adequate vein was identified. All patients in whom IV access could not be obtained by their initial randomized selection were moved to the alternate group. The percentage of patients who could undergo contrast media injection by their randomized selection was used as a measure of feasibility and was compared between the two groups. No patients were moved into a potential third group—that is, patients in whom we could not obtain IV access by either route.
The safety of the power injection of contrast media through central venous catheters was evaluated by comparing the rate of complications between the two groups. All patients were assessed for immediate complications related to the access route, such as extravasation or malfunction of the central venous catheter or any reaction after the examination. All patients were also contacted by telephone 24-48 hr after their examination to assess any early complications. This step was taken because most infections related to catheter access occur within 24-48 hr. Patients were specifically asked about fever, pain, or erythema around the catheter skin site to assess the possibility of infection. Patients were asked to report any other potential reaction. Patients were also asked if any subsequent difficulty had been encountered in accessing their central venous catheter after the examination. Delayed complications related to catheter infection were assessed by reviewing hospital records from the hospital information system for as long as 6 weeks after the study. Specifically, we evaluated evidence of infection as documented by positive findings on blood cultures or cultures of catheters, and we recorded all catheter removals and procedures used to clear blocked central venous catheters.
Contrast Administration Protocols
Contrast types, doses, and viscosities are listed in
Table 2. Contrast material was
kept warm, which lowers viscosity (Table
2). Nonionic and ionic contrast media were both used and were
chosen on the basis of the American College of Radiology guidelines for the
selective use of nonionic contrast media followed in our department
[12]. Iothalamate meglumine
60% (Conray 60%; Mallinckrodt, St. Louis, MO) and iopromide 300 (Ultravist
300; Berlex Laboratories, Wayne, NJ) were used for IV catheter injections.
Contrast material was administered through peripheral IV catheters at flow
rates of either 2.5 or 3 mL/sec for abdominal CT or combined chest and
abdominal CT examinations, and 2 mL/sec for neck and chest only CT. Slower
flow rates and lower-iodine-concentration contrast material with lower
viscosity were used with central venous catheters to remain within
manufacturer's guidelines of maximum pounds per square inch at the inflow into
the device
[1,2,3].
Because the central injection of contrast material should increase vascular
enhancement compared with peripheral IV catheter injection, we expected that
enhancement might remain similar even with slower flow rates and
less-concentrated contrast material. Therefore, we initially tested equivalent
volumes but found that the hepatic enhancement was significantly less; we then
changed the protocol to test equivalent doses with different volumes for the
port-type catheters only (the volume of other catheters was too small).
Iothalamate meglumine 43% (Conray 43%; Mallinckrodt) and ioversol 240 (Optiray
240; Mallinckrodt) were used for central venous catheter injections. Contrast
material was administered through central venous catheters at rates between
1.5 and 2.5 mL/sec for all CT examinations on the basis of the catheter in
place (derived from prior studies and in vitro testing of the devices). All
contrast material was injected using a Liebel-Flarsheim (Cincinnati, OH) 9000
series injector. We set the pressure cutoff (measured by the injector at the
plunger) at 300 psi for peripheral IV catheters and 100 psi for the central
venous catheter group. As determined by a previous study
[2], the pressure is higher at
the injector-tubing interface than at the tubing-catheter interface;
therefore, the pressure cutoffs were set as we have stated. Pressure cannot be
easily measured at the connection site of the tube to the catheter (or
hook-needle for port catheters) under adequately sterile conditions.
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Efficacy was determined by comparing the absolute contrast enhancement between peripheral and central venous access groups with a specific catheter type. Specifically, contrast enhancement of the liver and abdominal aorta for abdominal CT examinations, of the thoracic aorta and pulmonary artery for chest CT examinations, and of the carotid artery for neck CT examinations was compared.
Two reviewers unaware of the route of injection performed all measurements for each patient included in the study. The attenuation of the hepatic parenchyma during the portal venous phase was measured at the same hepatic level in both the right and left lobes of the liver before and after contrast administration. This was usually at the same table position unless considerable respiratory variation occurred. Care was taken not to include hepatic vessels in the region-of-interest circle. Similarly, the diameter of the region-of-interest circle was kept the same (2-3 cm) for all hepatic measurements. The right and left lobe absolute enhancement (average contrast-enhanced minus average unenhanced) was calculated. A single unenhanced image of the mid liver was obtained in most patients unless unenhanced imaging was part of the imaging protocol. The unenhanced and enhanced Hounsfield unit attenuations of the abdominal aorta on abdominal CT examinations, of the carotid artery on neck CT examinations, and of the descending thoracic aorta and central pulmonary artery measurement on chest examinations were recorded. The diameter of the region-of-interest circle was maximized to the diameter of the vessel without including edges or vascular calcifications. Single unenhanced images of the pulmonary hilus or neck were obtained.
Statistical Analysis
The first scan for each individual patient was used for statistical
analysis. Therefore, 225 patients and scans were included in the study. One
hundred nine patients were randomized to central venous catheter injection,
and 100 to peripheral IV catheter injection. The remaining 16 patients did not
have their initial randomization data recorded. After we reassigned patients
because of inability to obtain access, the two final groups consisted of 51
patients who received contrast material through a peripheral IV catheter and
174 patients who received contrast material through the central venous
catheter. This latter group included 117 patients with a port-type catheter,
28 with a triple-lumen Hickman catheter, 13 with an all-purpose triple-lumen
catheter, 10 with a double-lumen Leonard catheter, and six with another type
not recorded. The IV catheter group consisted of 32 (63%) women and 19 (37%)
men, and the central venous catheter group consisted of 117 (67%) women and 57
(33%) men. The mean ages for the peripheral and central venous access groups
were 55.5 and 52.5 years, respectively. No statistically significant
difference in age (p = 0.196, t test) or gender (p
= 0.550, chi-square test) was noted between the two groups. No difference
existed in the patient diagnoses between the two groups; 144 (83%) patients in
the central venous catheter group and 44 (86%) patients in the IV catheter
group had a cancer diagnosis, and the remainder had a non-cancer
diagnosis.
The 51 patients who underwent contrast injection by peripheral IV catheter were used as the control group for evaluating contrast enhancement. Enhancement was compared between the control group and two subgroups of patients with a Bardport central venous catheter (separating the patients who received 150 mL from those who received 200 mL) and two subgroups of patients with triple-lumen Hickman catheters. Statistical evaluation for this analysis was performed using the two-way analysis of variance and the Tukey test when significant differences occurred. Too few patients had other types of catheters to achieve statistical significance, and too few patients underwent neck CT to evaluate carotid artery enhancement.
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Safety (Rate of Complications)
Immediate complications.—Of patients who underwent contrast
material injection through their central venous catheters, 10 (6%) of 174
patients experienced some type of immediate complication. Most immediate
complications were minor contrast reactions, and one was idio-syncratic (a
patient noted a lump in her forearm after contrast material was injected
through the central venous catheter (Table
3). No patients had malfunction of the central venous catheter
immediately after the contrast administration. In the group of 51 patients who
underwent contrast injection through a peripheral IV catheter, two patients
(4%) experienced an immediate complication, both minor contrast reactions. No
statistically significant difference was seen in the rate of immediate
complications (p = 0.61, chi-square test)
(Table 4).
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Early complications.—Of patients who underwent contrast injection through their central venous catheters, three (2%) of 174 patients reported some type of early complication. One patient with a central venous catheter reported that her device was no longer patent. This patient's central venous catheter was used successfully by other personnel for chemotherapy between the CT examination and the follow-up, but statistically this was treated as a complication of the use of the central venous catheter with the power injector. In the group of 51 patients who underwent contrast injection through a peripheral IV catheter, only one patient (2%) reported an early complication. No statistically significant difference was seen in the rate of early complications (p = 0.91, chi-square test) (Table 4).
Delayed complications.—Of patients who underwent contrast injection through their central venous catheters, 39 patients had a blood culture documented within 6 weeks of the CT examination. Thirty-eight patients (97%) had negative blood cultures, and one patient (3%) had a positive blood culture (at 4 weeks after the CT examination). Eight patients had their central venous catheter lines removed during that time because it was no longer needed, and no culture was performed; and three additional patients were seen in clinical follow-up without a problem referable to the central venous catheter. The remaining 124 patients had no documentation of infection or catheter malfunction recorded in the hospital information system in the 6-week interval. Therefore, only one (2%) of 50 patients had a positive report of an adverse event, which may or may not have been related to the central venous catheter injection for CT.
Of patients who underwent contrast injection through a peripheral IV catheter, 11 of 51 patients had a blood culture documented within 6 weeks of the examination. All 11 patients (100%) had negative blood cultures. Two patients had their central venous catheter line removed during that time because it was no longer needed, and no culture was performed. The remaining 38 patients had no documentation of follow-up in the 6-week interval. No statistically significant difference was seen when evaluating for delayed complications, either comparing the entire patient group (1/174 versus 1/51) or just the group with documented follow-up (1/50 versus 0/13) (p > 0.5).
Contrast Enhancement in the Bardport Central Venous Catheter
Group
Enhancement in the thoracic aorta, pulmonary artery, and liver was less for
the Bardport central venous access group than for the peripheral venous access
group (Table 5). This
difference was statistically significant between the peripheral access group
and both the 150-mL and the 200-mL volume Bardport central access groups
(p < 0.011). No significant difference was noted between the two
Bardport groups, and no statistically significant difference was seen in the
enhancement of the abdominal aorta between the central and peripheral venous
access groups (p = 0.654). Not enough neck CT examinations were
performed (n = 4) to achieve statistical significance.
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Contrast Enhancement in the Triple-Lumen Hickman Central Venous
Catheter Group
Enhancement in the thoracic aorta, pulmonary artery, and liver was less for
the triple-lumen Hickman central venous access group than for the peripheral
venous access group. This difference was statistically significant (p
< 0.003) (Table 6). No
statistically significant difference was seen in the enhancement of the
abdominal aorta between these two groups (p > 0.268). Not enough
neck CT examinations were performed (n = 4) to achieve statistical
significance.
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Little literature exists on the use of central venous catheters to administer IV contrast terial for CT examinations using the same power injectors used for contrast administration through peripheral IV catheters, and the manufacturers make few recommendations. Data about the safety, feasibility, and efficacy of power-injecting contrast media through central venous catheters are mostly anecdotal, and practices vary among institutions. One group of authors has even devised a method for manually regulating the pressure [18].
In vitro studies have established that power injection of contrast media through central venous catheters is technically feasible without damaging the catheter while remaining within the manufacturer's guidelines for pressure at the catheter connection [1,2,3,4]. In one study, hand injection generated higher peak pressures at equivalent flow rates than did power injection [2]. A retrospective study of power injection of contrast media in 500 pediatric patients included more than 250 central venous catheters [5]. That study reported a low complication rate for power injection in pediatric patients, but flow rates used were less than or equal to 0.8 mL/sec. An in vitro study of implanted port devices also included a study of 13 patients [1]. Contrast material was injected safely in all patients and within manufacturer's pressure guidelines. However, once again flow rates were slow: 1 mL/sec. No large prospective study of the power injection of contrast media in adults at intermediate flow rates (1.5-2.5 mL/sec) has been performed.
Our study shows that power-injecting contrast media through the central venous catheters included in our study is both feasible and safe. IV access was achieved more frequently with the central venous catheter, as might be expected given the indications for placement of central venous catheters in these patients. No known catheter fractures occurred, and only one central venous catheter failure and one infection were reported. Overall, most complications were contrast-related; and although the total number is small, complication rates were not statistically different from those for contrast injection through a peripherally placed IV catheter.
Our study also shows that vascular enhancement is less for the pulmonary artery and thoracic aorta when injecting through the Bardport and triple-lumen Hickman catheters. This lower enhancement should be because of both a reduced concentration of contrast material and slower flow rates. Vascular enhancement of 80-100 H may be adequate for chest CT examinations; however, making such a determination would require a subjective evaluation. On the other hand, no difference was seen in the aortic vascular enhancement in the abdomen. This may be because the abdomen is typically scanned after peak aortic enhancement in order to scan the liver during peak portal venous enhancement. The differences in delay times (Table 7) and the duration of injection between the two protocols likely account for this result.
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The finding that liver enhancement is less with central venous catheter injection is not surprising given the results of a large body of literature on hepatic enhancement [10, 19,20,21,22,23,24,25]. Lower doses and slower flow rates do result in lower hepatic enhancement with peripheral IV catheter injection. Slower flow rates and less-concentrated contrast material were used for central venous catheter injections to remain within pressure guidelines set by the manufacturers and to avoid damaging the device or blood vessel. The less-concentrated contrast material used in this study with central venous catheters is less viscous, thus reducing the pressure generated at equivalent flow rates [2]. A previous study has shown that central injection of contrast material shortens the time to peak enhancement and improves vascular enhancement when compared with peripheral IV catheter injection [26]. We had therefore hoped that enhancement might remain similar even though slower flow rates and less-concentrated contrast material were used. This scenario did not prove to be true, however; power injection into a central vein could not compensate for the alterations in flow rate and concentrations used. We were able to achieve hepatic enhancement of approximately 40 H, which may be an acceptable degree of enhancement [10, 20, 21, 23].
Our study has some biases and limitations. First, regarding the feasibility portion of the study, only one attempt at peripheral venous catheter placement by experienced personnel was required for peripheral IV access; some patients did not undergo more than one attempt when venous access was poor. Therefore, some bias undeniably exists in the rate of failed peripheral IV catheter placements. Regarding safety, we set out to measure central venous catheter failures and extravasations, but most complications were contrast reactions. A relatively small number of patients were enrolled to evaluate differences in contrast reactions, and we are continuing to accrue data on safety. Another limitation is that only three registered nurses were used during the study to access and care for the central venous catheters. A degree of expertise and comfort with the central venous catheter devices might have added to the success of the study. Furthermore, we did not study pediatric patients.
Other limitations to this study include the relatively small number (13-66) of patients in each subgroup of central venous catheters used to compare contrast enhancement despite having more than 200 patients enrolled in the study. This small number was caused by the different central venous catheters implanted and CT examinations ordered. We also did not test different flow rates or delay times with the same catheter in vivo, nor was contrast enhancement compared in the same patient for the two different injection techniques [24, 25]. Further studies need to be performed to evaluate different injection protocols. Also, blood return determined whether a central venous catheter could be used, but we did not radiographically check central venous catheter position or monitor patient heart rate for arrhythmia. Doing so might have added greater safety. Finally, no direct analysis was performed after explantation of the catheter to ensure that no damage was done during the IV catheter injection; to do so is obviously impractical and not necessarily specific to power injector use.
One of our fears is that loose application of these methods will ultimately damage a central venous catheter or harm a patient. If power injection through central venous catheters were to become commonplace in radiology departments across the country, some serious complications would almost certainly arise because of the large number of personnel, varying skill levels, and volume of CT examinations performed. Therefore, we urge each institution to establish its own safety protocols. Our current hospital practice is as follows: We first attempt placement of a peripheral IV catheter; if that is unsuccessful, trained nursing personnel assess the central venous catheter for use. If the central venous catheter is accessible and there is blood return, contrast material is injected by power injector at the protocols given in this article.
In summary, power injection of IV contrast media through central venous catheters is feasible and safe as a means of IV access when central venous catheters are accessed according to hospital protocols. Power injection of contrast media through indwelling central venous catheters provides an alternative to obtain a bolus IV contrast-enhanced examination when peripheral IV access is inadequate. Careful adherence to protocols and hospital policies should help minimize risks to the patient. We suggest that before radiology departments use central venous catheters for power injection, policy guidelines be formed for the use, the monitoring of complications related to the use, and the devices used for the injection of contrast media.
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