|Year : 2015 | Volume
| Issue : 3 | Page : 173-177
Role of bedside ultrasound in determining the position of umbilical venous catheters
Samar Mohamed El-Maadawy1, Khaled Mahmoud El-Atawi2, Mahmoud Saleh Elhalik2
1 Department of Radiology, Latifa Hospital, Dubai, United Arab Emirates
2 Department of Pediatrics-Neonatal Intensive Care Unit, Latifa Hospital, Dubai, United Arab Emirates
|Date of Web Publication||2-Jul-2015|
Samar Mohamed El-Maadawy
Department of Radiology, Latifa Hospital, P.O. Box 9115, Dubai
United Arab Emirates
Source of Support: None, Conflict of Interest: None
Background: Umbilical venous catheter (UVC) is the most commonly used central venous line during neonatal resuscitation. Misplacement is responsible for potential serious complications. Aims: The aim was to find out the ability of bedside ultrasound to determine the UVC tip position (TP). Ultrasound may then be the new gold standard saving unnecessary radiographs thus decreasing the radiation dose received by neonates. Early detection of UVC misplacement will help in preventing complications as ultrasound is easy, readily available at the bedside. Settings and Design: Prospective blind comparison to a gold standard. Subjects and Methods: Our study included all neonates admitted to the neonatal intensive care unit from February 2013 to October 2013 who required insertion of UVC. Exclusion criteria included neonates with thoracic or abdominal congenital abnormalities, critically ill or very low birth neonates and withdrawal of parent consent. A portable chest-abdomen radiograph was obtained followed by bedside ultrasound examination by a senior radiologist blinded to the radiograph interpretation. The UVC TP determined by ultrasound was compared to chest-abdomen radiograph interpretation. Statistical Analysis: Sensitivity, specificity, accuracy positive and negative predictive values for ultrasound results were calculated. Results: Seventy-five catheter insertions for 74 neonates were included in our study. The sensitivity, specificity, and accuracy of ultrasound were 91.3%, 94.2%, and 93.3%, respectively, with a positive predictive value of 87.5% and a negative predictive value of 96.1%. Conclusion: Our results show that bedside ultrasound could replace thoracoabdominal radiograph in determining UVC TP therefore decreasing neonatal radiation dose and decreasing or preventing complications resulting from misplacement.
Keywords: Neonatal intensive care unit, ultrasound, umbilical venous catheter
|How to cite this article:|
El-Maadawy SM, El-Atawi KM, Elhalik MS. Role of bedside ultrasound in determining the position of umbilical venous catheters. J Clin Neonatol 2015;4:173-7
|How to cite this URL:|
El-Maadawy SM, El-Atawi KM, Elhalik MS. Role of bedside ultrasound in determining the position of umbilical venous catheters. J Clin Neonatol [serial online] 2015 [cited 2018 Feb 20];4:173-7. Available from: http://www.jcnonweb.com/text.asp?2015/4/3/173/159878
| Introduction|| |
The umbilical vein (UV) is the easiest and most-used central venous access during neonatal resuscitation. The catheter is introduced into the UV, joining the inferior vena cava (IVC) via the venous portal system and the ductus venosus (DV). 
The preferred location of the tip of the umbilical venous catheter (UVC) is typically in the cephalad portion of the IVC or at the IVC-right atrial junction. 
Misplacement is responsible for potential serious complications such as intracardiac thrombosis, arrhythmia, endocarditis, portal vein thrombosis, or hepatic necrosis. 
Anomalous positioning of the UVC frequently occurs because the catheter is inserted by the pediatrician without imaging guidance.  Thus, the catheter tip position (TP) must be confirmed with thoracoabdominal anteroposterior radiographs being the method most commonly used.  However, the last portion of the DV runs in the sagittal plain, and, therefore, is not visualized properly in AP view of the abdomen. As a result, catheter malposition can be easily missed. ,
Several recent studies have evaluated the role of ultrasound in UVC position. ,,,, In our institution, as well as in other institutions in the country, thoracoabdominal radiograph is the current standard to determine the UVC TP. The aim of our study was to find out the potential of bedside ultrasound to determine the UVC tip position and the early detection of UVC misplacement hence decreasing neonatal radiation dose and decreasing or preventing complications resulting from misplacement.
| Subjects and Methods|| |
Our study included all neonates admitted at our neonatal intensive care unit (NICU) from the period of February 2013 to October 2013 who required insertion of UVC. Exclusion criteria included neonates with thoracic or abdominal congenital abnormalities, critically ill or very low birth weight neonates who require minimal handling and withdrawal of the consent by the parent. The study was approved by our Health Authority Research Ethics Committee. Written consent was obtained from the parents in all patients.
The indications for catheter insertion in our unit includes all extreme preterm babies who are in need of respiratory support, administration of high osmolarity fluids and parenteral nutrition, also to those who require frequent blood sampling or blood gas monitoring and if exchange transfusion is needed. The UVC was inserted by neonatologist (VYGON umbilical catheter REF 1274.17, 5 Fr, ø1.7 mm-L. 40 cm, France). Immediately after the insertion of the UVC, a portable chest-abdomen radiograph was obtained using a portable radiograph unit (Mobile DaRt Evolution, Shimadzu, SN CM74B301101A, Japan). All the radiographs were interpreted by a senior neonatologist. As soon as possible after obtaining the radiograph, a bedside ultrasound examination was done by a senior radiologist blinded to the radiograph interpretation. Ultrasound was done using a portable ultrasound machine (Logic Book XP GE Healthcare, Germany) using the 8L superficial probe in sagittal and transverse planes through a thoracoabdominal approach with the neonate supine. Warm coupling gel was used under aseptic precautions. The UVC was carefully traced from the umbilicus up to the TP. By ultrasound, the UVC appeared as two intimately related echogenic parallel lines that end abruptly at the tip. Caution was taken so as not to confuse the UVC with nasogastric tube which follow a different route behind the right atrium (RA) via the gastro-esophageal junction to the stomach. The Preterm Infant Pain Profile (PIPP) - our unit pain assessment tool - was used during the ultrasound examination to assess the tolerance to the ultrasound procedure. The assessment was done by our unit nurse. A pain score of 0 to 6 implied that the ultrasound procedure was well-tolerated, and no action was required.
Two separate data collection sheets were used for each catheter insertion; radiograph data collection sheet that was filled by senior neonatologist blinded to the US interpretation and ultrasound data collection sheet that was filled by senior radiologist blinded to the radiograph interpretation. Both sheets included the patient name, health card number, gestational age, weight in grams, and estimated TP (UV, branch of portal vein [BPV], DV, RA, left atrium [LA], right ventricle or undetermined). In addition, the radiograph data collection sheet included the vertebral level of the catheter tip, and the ultrasound data collection sheet included any catheter-related complications.
In our study, the correct UVC TP was defined as a tip located within the distal thoracic IVC or at the IVC/RA junction; all the remaining positions were considered incorrect.
Both data collection sheets for each catheter insertion were analyzed and interpreted for catheter TP. Statistical methods used included mean and standard deviation, median, and range. Categorical data were described in terms of frequencies (number of cases) and percentages. Sensitivity, specificity, accuracy positive and negative predictive values for ultrasound results were calculated using the following definitions. True positive when radiograph showed a correct TP and the ultrasound was in agreement, true negative when radiograph showed incorrect TP and the ultrasound was in agreement, false positive when radiograph showed incorrect TP but was reported as correct by ultrasound or the ultrasound failed to determine the TP and false negative when radiograph showed a correct TP but was reported as incorrect by ultrasound or the ultrasound failed to determine the TP.
| Results|| |
Seventy-five UVC's were evaluated in 74 neonates. The mean gestational age was 31.0 ± 5.56 weeks (ranged from 22 to 40 weeks). The weight ranged from 415 to 4075 g with a median of 1000 g.
The UVC TP was clearly seen in all 75 catheter insertions by radiograph (100%) and in 74 out of 75 catheter insertions by ultrasound (98.7%).
By radiograph, the estimated TP was determined to be correct in 23/75 catheter insertions (30.7%) out of which 21 insertions (28%) were at the distal thoracic IVC and two insertions (2.7%) were at the IVC/RA junction. In the remaining 52/75 catheter insertions (69.3%), the TP was considered incorrect with 39 insertions (52%) at the RA, one insertion (1.3%) at the LA, five insertions (6.7%) at the DV, six insertions (8%) at the BPV, and one insertion (1.3%) the UV [Table 1]. The vertebral level of the TP was recorded from T4 to L1.
|Table 1: Umbilical venous catheter tip position as determined by radiograph|
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By US, the estimated TP was determined to be correct in 23/75 catheter insertions (30.7%) out of which 21 insertions (28%) were in the distal thoracic IVC and two insertions (2.7%) were in IVC/RA junction. In 51/75 catheter insertions (68%), the TP was considered to be incorrect with 40 insertions (53.3%) at the RA, one insertion (1.3%) at the LA, four insertions (5.3%) at the DV, four insertions (5.3%) at the BPV, two insertions (2.7%) at the UV. In the remaining case, (1.3%) the ultrasound failed to determine the UVC TP [Table 2]. The proposed reason for this was the position of the neonate in the incubator; the neonate was positioned in an oblique view due to ventilation related pneumothorax and chest tube insertion. In one case, the ultrasound was able to locate the UVC TP at the LA; the UVC was pulled back, and a repeat ultrasound showed the UVC to be correctly placed at the IVC/RA junction. In two cases, the ultrasound showed the UVC TP at the UV; the UVC was removed and a right lower limb PICC line was inserted. In four cases, the ultrasound showed the UVC tip at BPV. One case developed transient portal venous gas, one case developed hepatic hematoma, and another case developed the encysted liver collection [Figure 1]. The two cases with hepatic hematoma and encysted liver collections required further follow-up with CT and ultrasound. All of these four catheters were removed, and lower limb PICC lines were inserted. In two cases where the UVC TP was at the RA, ultrasound detected small rim of pericardial effusion. Therefore, ultrasound was able to detect complications resulting from misplacement in 5/75 catheter insertions (6.7%). The ultrasound examination was tolerated well by all neonates as all had a PIPP score <6.
|Figure 1: (a) Thoracoabdominal radiograph at day 3 of life showing umbilical venous catheter (UVC) tip at T10. (b) Ultrasound on the same day showing UVC tip at left portal vein branch. (c) An irregular heterogenous collection seen at left lobe of the liver. (d) Computed tomography with intravenous contrast revealing a complex cystic liver collection with small air locule (arrow)|
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|Table 2: Umbilical venous catheter tip position as determined by ultrasound|
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Nineteen out of 21 catheter insertions thought to be in the IVC by radiograph were found to be in the IVC by ultrasound and four out of six catheter insertions thought to be in BPV by radiograph were found to be in BPV by ultrasound. All the 39 catheter insertions thought to be in the RA by radiograph was found to be in the RA by ultrasound [Table 3]. Of 23 catheter insertions thought to be correct by radiograph 21 catheter insertions were found to be correct by ultrasound and out of the 52 catheter insertions thought be incorrect by radiograph 50 were found incorrect by ultrasound. The sensitivity, specificity, and accuracy of ultrasound were 91.3%, 94.2%, and 93.3%, respectively, with a positive predictive value of 87.5% and a negative predictive value of 96.1%.
|Table 3: Positions of the catheter tip determined by radiograph compared with ultrasound|
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Ultrasound improved radiograph interpretation in two cases. One case was thought to be in incorrectly positioned in the DV by radiograph but was seen in the IVC by ultrasound. The second case was thought to be incorrectly positioned in the BPV by radiograph but was seen in the IVC by ultrasound. Accordingly, no change in catheter position was done.
| Discussion|| |
Umbilical venous catheters are widely used in NICUs. Despite their widespread use, misplacement is common because the neonatologists are inserting these catheters blindly without the aid of imaging. A study about the appropriate and inappropriate UV catheterization placement showed that an acceptable position of UVC was achieved on the first attempt in less than half of placements.  Michel et al.  found that only 45.9% of UVCs had a central route on initial UVC placement. Our study showed that 30.7% of all catheter insertions were appropriately placed on the first attempt.
A recent study by Michel et al.  on a total of 60 subjects found that US is more accurate that thoracoabdominal radiograph in determining UVC route and TP. However, in their study, their gold standard - "actual position" - was determined by agreement of senior pediatric radiologist and neonatologist based on the results of thoracoabdominal radiograph and ultrasound. Our study was done with larger population, and we considered the thoracoabdominal radiograph as the gold standard and compared the ultrasound results to it. We have found ultrasound to be an accurate imaging modality with an accuracy of 93.3%, sensitivity of 91.3%, specificity of 94.2%, a positive predictive value of 87.5% and a negative predictive value of 96.1%.
Another study concluded that US provides precise detection of umbilical catheter TP in most of their cases.  We agree with their conclusion that the main advantage of US evaluation over radiograph is early detection of catheter malposition avoiding serious complications.
Another appealing advantage of ultrasound is lack of ionizing radiation. One study reported that 4% of preterm neonates required >30 radiographs during their stay in the NICU, resulting in increased risk of developing radiation-induced malignancies in low birth weight infants.  In our institution, we strive to keep the radiation dose to pediatrics to a minimum in line with Image Gently Campaign, which was proposed by our Health Authority Radiation Protection Committee. Keeping radiation doses to the minimum will also reflect on the radiology technicians and nursing staff.
One limitation of our study is the lack of trained personnel in the NICU to perform the ultrasound examination immediately after UVC insertion. The ultrasound examination in our study was performed by a senior radiologist who may not be available around the clock to perform such examination. A proposed solution of this is to train junior neonatologist on this technique so that they can carry on the examination independently.
In our study, 53.3% of all catheter insertions were seen at the RA by US. One study reported that despite the documented pathology associated with right atrial catheters, many institutions continue to accept catheter location in the RA. This is perhaps due to the lack of an adequate method to ensure accurate right atrial/IVC junction placement other than echocardiography.  Narla et al.  considered the right atrial position as ideal. Another study reported that the RA might be considered a safe location of the UVC tip if central in the lumen. From the RA, a UVC has a potential of crossing the foramen ovale into the LA. 
We have found poor correlation between the thoracic vertebral level of UVC TP by radiograph and the corresponding position seen on ultrasound. If we assume that RA is an acceptable position of UVC tip in addition to distal thoracic IVC and IVC/RA junction, then the vertebral level by radiograph will range from T4 to T11 [Figure 2]. It has been suggested in the previous study that the tip must be placed between T8 and T9.  Another study reported an adequate position from T6 to T11.  These findings were confirmed by Michel et al.  who found that an appropriate position ranging from T4 to T10 with a median of T7. Some authors have suggested adding a lateral radiograph to improve UVC localization. ,, A recent study by Butler et al.  concluded that lateral radiographs are more reliable in measurement of UVC TP and should be performed in conjunction with AP films to aid in detecting UVC position. We agree with their conclusion particularly if US is not available. However, we think that adding a lateral radiograph will add to the radiation burden to the neonate, radiology staff, and NICU nurses.
|Figure 2: Distribution of thoracic vertebral body catheter tip location compared to ultrasound location. IVC - Inferior vena cava; RA - Right atrium; LA - Left atrium; DV - Ductus venosus; BPV - Branch of portal vein; UV - Umbilical vein|
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The incidence of complications in our study was 6.7%. One study reported a single complication of transient arrhythmia that resolved with ultrasound-guided repositioning of the catheter. They reported that although the incidence of complications in their study was low, thrombosis, vascular injury, and portal hypertension may occur. Emboli and damage to the foramen ovale may also occur with malpositioned catheters. Thus, care should be taken with insertion and positioning of catheters and UVCs should be used only when clinically indicated. 
Although many neonates might require umbilical arterial catheter (UAC), none of the cases in our study needed any as its indication in our unit are cases of congenital diaphragmatic hernia and persistent pulmonary hypertension of the newborn. Ultrasound has been used to locate UACs because it allows direct visualization of vascular anatomy.  US is also useful in the assessment of complications, such as thrombosis and aortic aneurysm, following umbilical arterial catheterization. 
| Conclusion|| |
Our results show that bedside ultrasound could replace thoracoabdominal radiograph in determining UVC TP therefore decreasing neonatal radiation dose and decreasing or preventing complications resulting from misplacement. We think that validation studies with larger sample size are required to determine the true role of ultrasound in determining the UVC TP.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]