Vascular catheterization is one of the most common procedures in everyday clinical practice in hospitals and is not free of complications.1 Ultrasound-guided central vein catheterization has been widely used in adults and subsequently in children, and in recent years it has been found to be very useful in young infants and newborns.2,3

Thus, the international evidence-based guidelines on point of care ultrasound (POCUS) of 2020 and the Cochrane review on the subject of 2015 recommend POCUS-guided technique for inner jugular vein line placement in neonates and children with a quality of evidence A.4,5 Oulego-Erroz et al. recommended ultrasound-guided subclavian and brachiocephalic venous line placement in children and neonates, associated with a greater success rate with fewer needle passes.6

The umbilical vein is the vascular access site of choice in the initial management of the newborn. The reported failure rate of blind umbilical vein line placement ranges from 25% to 50%, and this technique, contrary to line placement at other central access sites, has not been modified for decades.7,8

A correctly placed umbilical catheter is inserted through the umbilical vein, traversing the portal sinus to the ductus venosus, with confirmation of the central position by visualization of the tip at the inferior cavoatrial junction.7

During insertion, the catheter may migrate towards the left portal vein, right portal vein, splenic vein or, less frequently, the mesenteric vein.

Malposition with progression of the catheter into the portal system may take place in up to 40% of patients, and this position (subhepatic) can cause severe complications such as portal vein thrombosis, portal hypertension and portal cavernoma formation, abscess, ascites, cardiac tamponade and hepatic necrosis due to the hyperosmolality of infused solutes.7–9

Thus, in 2006, Morag et al. described a series of 133 children with portal vein thrombosis, of who 45 (34%) had a history of umbilical catheter in situ.

This warrants the search for methods that could improve the success rate in terms of achieving the central position in umbilical vein catheterization.9

One such method is the double catheter technique. It is based on the notion that the first (malpositioned) catheter followed the path of least resistance, entering one of the vessels in the portal system. The second catheter would bypass the area of misdirection, already occupied by the first catheter, and enter the inferior vena cava. The reported success rate was 50%, and the only described complication was bleeding during the removal of the malpositioned catheter, which was easily controlled.10

Another strategy is placing the infant lying on the right side. The rationale is that this position would pull the right lobe of the liver downward, increasing the external pressure on the portal vein and reducing the pressure on the ductus venosus, making it easier for the catheter to pass through the latter into the inferior vena cava. A study conducted by Kieran et al. did not find an increase in the success rate with this technique, although the authors noted that a larger sample may have supported this hypothesis. The technique was well tolerated and the position did not increase the difficulty of inserting the catheter.11

A third technique involves manual mobilization of the liver and is based on anatomical reasoning. Applying pressure over the liver to push it downwards shifts the portal sinus and improves the angle of the umbilical vein in relation to the ductus venosus, creating a flatter and straighter trajectory. It also compresses the opening into the left portal vein and reduces the angle of the caudal turn from the portal sinus to the right portal vein, making it less accessible.9 It is important to avoid applying excessive pressure, which could occlude the entry to the ductus venosus, and it may be necessary to inject a small volume of saline through the catheter to dilate it temporarily and facilitate its passage. This reduced the failure rate by 52%.9

Last of all, we discuss real-time ultrasound guided catheterization. The most recent guideline of the European Society of Paediatric and Neonatal Intensive Care on the subject recommends the use of POCUS to guide catheterization of the femoral vein, jugular vein and others, and also to assess the position of the catheter tip.4 However, the application of POCUS to umbilical vein catheterization is a novel and emerging technique that entails significant progress in this essential neonatal procedure.7

Using the liver as an acoustic window, the relevant anatomy may be visualised with the transducer (sector array or linear array) approximately at the midline, below the xyphoid and facing the head longitudinally, finding the territory of the umbilical and portal veins (Fig. 1).

Figure 1.

Image obtained during ultrasound-guided umbilical vein catheterization. The umbilical catheter can be traversing the portal sinus to enter the ductus venosus.

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The reported success rate is of 93%, with no complications.8

We present a study conducted after the introduction of a stepwise protocol aimed at improving the success rate of umbilical vein catheterization.

Our primary objective as to assess the impact of novel techniques in the success rate of umbilical vein catheterization over a 12-month period.

The secondary objectives were to describe the epidemiological and clinical characteristics of the patients, identify the recanalization technique used most frequently in our hospital and the technique with the highest success rate and describe the potential complications associated with malpositioned central lines.

Design: quasi-experimental pre- and postintervention study conducted in a level B neonatal intensive care unit (NICU) (not offering neonatal surgical care).

Participants: all newborns who required umbilical vein catheterization for any reason between January and June 2022 (preintervention) and between July and December 2022 (postintervention). The sole exclusion criterion was the refusal of the parents or legal guardians to consent to participation.

During the study period, we included 72 children, 25 in the preintervention group and 47 in the postintervention group (Fig. 2).

Figure 2.

Flowchart of performed catheter insertions and reinsertions in the preintervention and postintervention periods.

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When it came to their clinical and epidemiological characteristics, there were no significant differences between the two periods (Table 1).

We did not identify complications such as portal vein thrombosis, abscesses, ascites or necrosis in either period.

The mean catheter indwelling time was of 3 days in the preintervention period compared to 3.5 days in the postintervention period.

The relative frequency of central venous catheterization did not differ between the preintervention and postintervention periods, with percentages of 48% and 51%, respectively. Table 2 presents the data on the catheter tip position, methods used for catheterization and methods used to assess the catheter tip position.

In the preintervention period, repositioning was not attempted in any case. However, in the postintervention period, out of the 23 patients in whom the first catheterization was unsuccessful, reinsertion was not attempted in 4 and attempted in 19, per the decision of the physician in charge. Of the 19 patients in whom it was attempted, repositioning was successful (catheter tip in the central position) in 10 (52%) and unsuccessful in 9, which increased the overall percentage of patients with successful umbilical vein catheterization to 72%.

The most successful catheter repositioning technique used in our unit was liver pressure (used in 5 cases), with an overall reinsertion success rate of 55%, followed by the double catheter technique (used in 2 children, successfully) and ultrasound-guided repositioning combined with liver pressure. Liver pressure followed by ultrasound-guided reinsertion with liver pressure was used in a single patient. The combination of different techniques (double catheter, liver pressure and ultrasound-guided) achieved a success rate of 50% (Fig. 3).

Figure 3.

Recannulation methods and success rate.

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When it came to the assessment of the catheter tip position, following the introduction of these methods, the use of sonography besides radiography increased by 22%.

In 6 cases in the postintervention period (13%), the peripheral catheter was left in place, having attempted umbilical vein catheter repositioning, unsuccessfully, in only half of them.

Although there is scientific evidence that supports the recommendation of ultrasound-guided catheterization of other vessels, such as the jugular or femoral veins,2–6 few studies contribute evidence in support of it use for umbilical vein catheterization.7,8

Unlike other studies that have reported success rates of up to 93%, in our study we did not find statistically significant differences in the first-attempt success rate between the groups. One possible explanation is that our unit is going through the learning curve for these new techniques, especially the use of POCUS to guide umbilical vein catheter placement.

Still, the new techniques succeeded in achieving correct reinsertion of 53% of the malpositioned catheters in the postintervention group. We believe that this reduced the use of material resources, saved time that would have been attempting catheterization at other access sites and, in addition, spared our neonatal patients the pain associated with invasive punctures, besides allowing earlier initiation of intravenous treatment.

The main benefit of our study is that the failure rate observed with blind catheter insertion, of 52%, decreased to 27% after the introduction of the new techniques.

The most frequently used technique was liver pressure, both for catheter reinsertion and initial insertion. Its salient qualities are that it is quick and easy to implement, does not require prior experience and is particularly appropriate for catheterization in extremely preterm or severely ill infants. The success rate in our sample was high, of 52.6% for initial catheter insertion and 55.5% for catheter reinsertion, and there were no associated complications, in agreement with the previous literature.9

The double catheter technique was used sparingly and only for repositioning. In our case, it was only used in 2 cases, successfully in both, with no associated complications.10 The approach of placing the patient in the right lateral decubitus position was not used in any instance because the literature to date has not described an increased success rate, because help from an additional staff member would be required to hold the child in the position and because the position itself could be poorly tolerated, although Kieran et al. reported that the position was well tolerated and did not increase the difficulty of inserting the catheter.11

As for the use of ultrasound, umbilical vein catheterization was guided by ultrasound in 6 instances, combined with liver pressure in 2, and this approach was successful in 50% of cases. It was used for catheter reinsertion 5 times, also with a 50% success rate. Although this technique requires at least 2 qualified staff members, frequent use of it could shorten the duration of the procedure and would allow performance of it in more severely ill and premature infants, always making sure to take the precaution of warming up the ultrasound gel. At the moment, it is a novel and emerging technique for the catheterization of umbilical vessels, and it is a significant advance in this basic neonatal procedure that we believe must be known to the largest possible number of physicians.

Another strength of our study is that we succeeded in reducing the amount of radiation that our patients were exposed to, as the initial suspicion that the catheter was malpositioned was based on clinical features and in most cases the catheter was reinserted without prior performance of a radiograph. We have also started to use sonography to assess the position of the catheter tip in addition to plain radiography, and we may eventually stop using radiography for this purpose altogether. Last of all, another positive aspect is that, as a result of the review, we have emphasised the need to remove malpositioned catheters from the portal system in our unit, on account of the risk of complications.9,12

One of the limitations of the study is that it had a quasi-experimental design and there was no simultaneous control group to compare the effects of the intervention with, which may limit the extrapolation of the results.

Another limitation is that despite the new techniques and the two hypothetical clinical scenarios presented and proposed at the beginning of the study, both the technique chosen for umbilical vein catheterization and the decision to attempt reinsertion in the case of malposition were left to the judgment of the physician in charge of the patient at the given time. As a result, reinsertion was not attempted in every instance that the catheter was not inserted correctly.

Thus, although the use of new techniques in our sample was not associated with an increased first-attempt success rate, it did increase the success rate of catheter reinsertion. Therefore, we believe it could be beneficial for neonatal units with failure rates similar to those of our unit to implement the measure bundle we applied or a similar one to increase their success rate.

This research did not receive any external funding.

The authors have no conflicts of interest to declare.