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Original Research |
1 Department of Diagnostic Imaging, Hospital for Sick Children, 555 University
Ave., Toronto, ON M5G-1X8, Canada.
2 Department of Medical Imaging, Toronto Western Hospital, University Health
Network, Toronto, ON M5T-2S8, Canada.
Received April 18, 2005;
accepted after revision June 7, 2005.
Address correspondence to J. G. Amaral
(joao.amaral{at}sickkids.ca).
Abstract
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SUBJECTS AND METHODS. At a tertiary pediatric center, we prospectively collected data on 557 children undergoing CT with IV contrast injection by power injector through a peripheral venous line. Data collected included age, weight, angiocatheter size, location of venous access, flow rate, total contrast volume, maximum injector pressure, and incidence of extravasation. Adverse effects such as emesis, sensation of warmth, hives, and allergies and anaphylaxis also were recorded.
RESULTS. The patients' ages ranged from 13 days to 20 years (mean, 9.8 years). The size of angiocatheter most commonly used was 22 gauge (n = 443). The dorsum of the hand was the most common site of venous access (n = 373). The mean flow rate was 1.48 mL/s. When the patients were divided into groups on the basis of reaction or no reaction, statistical differences between the groups were found with respect to flow rate (p = 0.016) and pressure (p = 0.017) needed for injection. There were two episode of extravasation (0.3%), which were treated conservatively.
CONCLUSION. The use of power injectors through 18- to 24-gauge angiocatheters in children is safe when meticulous technique is used and personnel are appropriately trained. Our study showed a similar rate of extravasation as has been reported in other studies.
Keywords: children • contrast media • CT • pediatrics • power injectors • safety
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There have been anecdotal reports of power injector use in children, but to our knowledge, only two studies in the English-language literature specifically describe the use of power injectors and their safety in children [2, 3]. An important complication related to IV injection is the risk of extravasation of the contrast medium. In children, the volume of extravasated contrast material necessary to damage soft tissues, including skin, blood vessels, and nerves, is much smaller than in adults. The use of power injectors in imaging of children therefore has been avoided at some institutions.
The purpose of our study was to assess the safety of power injector use in peripheral IV injections as measured by the incidence of extravasation in children undergoing CT. We also review the management of contrast media extravasation as reported in the literature.
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The power injector (Envision CT, Medrad) was used with the manufacturer's
preset specifications except that the pressure limit was adjusted to a maximum
of 150 psi (1,034 kPa). The examinations were performed with an 8-MDCT scanner
(LightSpeed Ultra, GE Healthcare). Nonionic low-osmolar contrast medium
(iohexol, Omnipaque 300, Nycomed) warmed to body temperature (
37°C)
was administered. The approximate viscosity of iohexol at this temperature
equals 6.3 cp (centa-Poise)
[1]. The maximum contrast dose
was 2 mL/kg to a total maximum dose of 100 mL, unless otherwise specified by
the radiologist. The flow rate for each study was determined by the
radiologist and set at the minimum rate that would achieve the imaging
objective. The maximum flow rates for the angiocatheters are shown in
Table 1. These rates were based
on our previous clinical experience.
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When the patient arrived in the CT area, one of the CT team members (radiology nurses, CT technologists, and radiologists) who was trained and had experience in the use of a power injector obtained peripheral venous access or evaluated an existing access site. This person gently flushed the IV catheter with 5-10 mL of normal saline solution and verified patency. If any resistance was felt, new peripheral venous access was obtained or manual injection was performed. The patients who needed a manual injection were excluded from the study. The site chosen for insertion of the IV catheter was at the discretion of the CT team member obtaining venous access with no specific recommendations. During the injection, one of the CT team members remained in the CT room observing the site and directly palpating the region proximal to the angiocatheter insertion site. If there was any suspicion of extravasation, this individual terminated the injection immediately.
In our department, most body CT examinations are performed in a single
phase after contrast administration ( 60-second delay) to decrease the
overall radiation dose to the child. In most routine abdominal and pelvic CT
examinations, the child is imaged in the portal venous phase. Therefore, in
most cases, the individual observing the site was able to leave the room
before the scanning was initiated, limiting exposure of personnel to
radiation. During CT angiography, however, one of the CT team members remained
in the room, palpating the site until the end of the injection.
The power injector was used only in patients with peripheral venous access. If the patient had a peripherally inserted central catheter, central venous line, Port-A-Cath, midline or butterfly needle, new peripheral venous access was obtained, or the power injector was not used.
The data collected included age and weight, gauge of angiocatheter (16, 18, 20, 22, or 24), total volume of contrast medium used, total injection time, flow rate, and injector pressure needed to achieve the selected flow rate. We limited the maximum injector pressure in our machine to 150 psi (1,034 kPa). If a certain flow rate required an injector pressure higher than 150 psi, the power injector automatically decreased the flow rate, returning the pressure to less than its maximum limit. Therefore, a pressure greater than 150 psi might have been recorded before a drop in flow rate. The IV catheter location (hand, wrist, forearm, elbow, or foot) was recorded.
Adverse effects were classified as sensation of warmth, vomiting, hives or anaphylaxis, and extravasation. The incidence of each adverse effect was recorded and correlated with the size of the angiocatheter. The patients were also subdivided into two groups according to the presence or absence of any side effect, and the injection characteristics for these two groups were compared. It is our departmental policy that any major complication such as extravasation or anaphylaxis generate an incident report. These reports were reviewed, confirming that all cases of extravasation in our study population were accounted for.
This study was approved by our institutional research ethics board. Statistical analysis comparing reaction groups was done with a two-tailed unpaired Student's t test with a confidence level of 95% (unequal variances assumed). A p value less than 0.05 was considered to indicate a significant difference. Descriptive statistical analysis was also performed. All statistical analyses were conducted with SPSS software version 12.0.
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The dorsum of the hand was the most common location of venous access and was the site of injection in 373 (67.3%) of the children. The antecubital fossa or elbow was used in 119 (21.5%) cases (Table 2). Twenty-two-gauge angiocatheters were used in 443 (80%) patients, and 24-gauge angiocatheters were used in 78 (14.1%) patients. Larger-bore angiocatheters (16-, 18-, and 20-gauge) were used in only 32 (5.8%) patients.
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The volume of contrast medium injected ranged between 8 and 152 mL, with a mean volume of 68.8 ± 30.1 mL (doses > 100 mL were administered at the discretion of the radiologist for specific indications). Flow rate ranged between 0.4 and 4 mL/s (mean, 1.48 mL/s), and injection times ranged between 6 and 100 seconds (mean, 47.3 seconds). The measured pressures ranged from 15 to 180 psi (103-1,241 kPa), with a mean pressure of 58.8 psi (405 kPa). Additional details on flow rate, pressure, and complications in comparison with angiocatheter size are in Table 3.
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Two episodes of extravasation were detected in our sample population. The first occurred in a 10-year-old girl who had been in a motor vehicle accident and had a small epidural hematoma that necessitated CT angiography. During injection through a 20-gauge angiocatheter in the left forearm at a rate of 3 mL/s, 50 mL of contrast medium extravasated into the subcutaneous compartment. The injection was stopped, and cold compresses were applied. The child did not complain of pain or discomfort during the injection. Physical examination showed the forearm was edematous. No discoloration, blisters, motion limitation, or neurovascular compromise of the left limb was found. There were no signs of compartment syndrome. The plastic surgery service was consulted, and conservative management was instituted. The patient was treated with elevation of the affected arm. Soft-tissue swelling improved after 2 days, and no permanent sequelae occurred. The study was completed successfully with access of another IV site and administration of contrast medium through a power injector.
The other episode of extravasation occurred in a 17-year-old boy who had undergone renal transplantation and chest and abdominal CT for exclusion of posttransplantation lymphoproliferative disorder. Injection was performed in the hand through a 22-gauge angiocatheter. The rate was 1.5 mL/s. Approximately 10 mL of contrast medium extravasated into the interstitial compartment. Cold compresses were applied, and the swelling subsided within 2 hours. The patient was discharged with no sequelae.
Among the other patients who had adverse effects, one patient experienced hives, 14 patients experienced emesis, and 46 felt a sensation of warmth. No episodes of anaphylaxis occurred. The pump did not fail during our data collection period.
When we compared the group that experienced any side effect with the group that did not, there was a significant difference between the groups with respect to flow rate. The mean flow rate of 1.73 mL/s in the side effect group was significantly higher than the mean flow rate of 1.46 mL/s in the no side effect group (p = 0.016). The mean pressure of 69 psi (476 kPa) in the side effect group was also significantly higher than the mean pressure of 57.5 (396 kPa) in the no side effect group (p = 0.017). No significant difference in age, weight, volume of contrast medium, or time for injection was found between the groups (Table 4). Because of the small number of cases of extravasation in our sample, the site of injection and flow rate were not correlated with extravasation rate.
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In our hospital, a power injector was successfully used in 554 children. It was interesting that 67.5% of the injections were performed on the dorsum of the hand and that small-bore catheters were used in 94.2% of our sample. Although it has been suggested [4-7] that power injection into the dorsum of the hand is a risk factor for extravasation and should be avoided, no significant increase in the rate of extravasation was found in our population. Jacobs et al. [1] also found that there was no correlation between extravasation rate and catheter location, catheter size, or catheter type.
The 0.3% rate of extravasation in our sample population is within the range reported in the literature (0.1-0.9%) [1-5, 7-10]. Cochran et al. [3] reported an incidence of 0.34% in the largest series of power injector use in the literature (66,029 patients). Those authors also identified a subgroup of patients ranging in age from 3 months to 9 years (4,911 children) who had a 0.16% incidence of extravasation. Unfortunately, flow rates were not reported in that series. The other large pediatric series (3,121 children), described by Kaste and Young [2], had a 0.2% incidence of extravasation. In that study, however, the flow rate was limited to 0.8 mL/s, and peripheral and central venous access sites were used for injection. The flow rates were higher in our study (mean, 1.48 mL/s), and only peripheral venous access was used. In accordance with our findings, a study by Jacobs et al. [1] showed that extravasation rate did not correlate with injection rate.
When the patients with any side effect (warmth, emesis, hives) or extravasation were separated from those with no side effect and the two groups compared, a significant difference in flow rate and pressure was found. The patients in the side effect group had higher flow rates and pressures. No significant difference was found in volume of contrast medium or time of injection.
In our sample, only two cases of subcutaneous extravasation occurred (0.3%). The patients were treated conservatively with good outcome and no adverse sequelae. Because the prevalence of contrast extravasation is not high, treatment is based on experience gained with extravasation of other medications, mainly chemotherapeutic agents. Treatment depends on the agent used, volume injected, and presence or absence of mechanical compression [6]. As expected, extravasation of large volumes has a higher chance of leading to compartment syndrome. Mattern et al. (Mattern C et al., presented at the 2004 annual meeting of the American Roentgen Ray Society) addressed the importance of the compartment in which extravasation occurs. Those authors suggested that subcutaneous extravasation is less likely to lead to compartment syndrome than is muscular extravasation because of contrast diffusion through the subcutaneous tissues due to the absence of fascial planes. The agent injected is also important, as described by McAlister and Kissane [11]. In a study with an animal model, those authors found that ionic contrast medium produced more inflammatory reaction and focal necrosis in the soft tissues than did nonionic or low-osmolar ionic contrast medium.
Most articles in the literature [4-7] suggest conservative management if a low volume of nonionic or low-osmolar contrast medium is extravasated. This management includes aspiration of fluid before catheter removal, elevation of the affected extremity above heart level, and application of cold compresses over the affected area for 15-60 minutes every 45 minutes and observation every 30 minutes for the first 4 hours [5-7]. If blistering, altered tissue perfusion, or any clinical signs of compartment syndrome (tense compartment, paresthesia, pain on passive stretching of the muscle, sensory loss) [12] are present or develop after several hours, immediate consultation with a plastic surgeon is recommended. In two large series (Sistrom et al. [8] with 28 cases of extravasation and Jacobs et al. [1] with 41 cases of extravasation in 6,660 injections), all patients with extravasation were treated conservatively with no adverse sequelae.
An alternative treatment advocated by some authors includes injection of hyaluronidase, an enzyme that breaks down the interstitial barriers in the connective tissue by disrupting the interstitial polysaccharide bonds that normally hold cells together. This treatment promotes dispersion of the contrast medium, facilitating its removal by lymphatics and capillaries. Promising results were reported by Cochran et al. [3], but the study was not a randomized trial, and different therapies after contrast extravasation were not compared. Therefore, the use of hyaluronidase in the management of contrast extravasation is still controversial [8].
Surgical drainage and suction alone or combined with saline flushing also have been discussed in the management of contrast extravasation. Most plastic surgeons, however, recommend a conservative policy [6].
A limitation of our study was the small sample size from a single pediatric institution. Therefore, risk factors for the use of a power injector cannot be determined. Another limitation was that the incidence of minor adverse effects was underestimated because the nurses and technologists collected the data only if the patient volunteered a complaint. The nurses, technologists, and radiologists did not actively ask the patients about changes such as warmth or nausea. In addition, several patients were younger than 5 years, and these patients often cannot express specific complaints.
We conclude that the use of a power injector in children not only is feasible but also is safe. Small-bore angiocatheters (22- and 24-gauge) can be used. In our study, almost 70% of injections were performed in the dorsum of the hand with no increased risk of extravasation. Our extravasation rate of 0.3% is similar to those in published data. If extravasation occurs, we suggest conservative management and close observation. Plastic surgical consultation may also be considered.
Acknowledgments
We thank the CT technologists and nurses for their help in collecting the
data.
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