Real-time ultrasound for tip location of umbilical venous catheter in neonates: a pre/post intervention study

The umbilical venous catheter (UVC) is currently one of the most common central venous access devices used in neonatal intensive care unit (NICU). It is very easy to place, more stable when compared to a peripheral venous line and suitable for preterm and critically ill term infants who require fluids, inotropes, parenteral nutrition or frequent blood sampling [1]. The UVC is usually inserted by skilled medical staff at a distance previously calculated using anthropometric measures or formulas and nomograms usually based on birth weight (BW) [2, 3].

The ideal UVC tip position is outside the heart at the junction of inferior vena cava (IVC) and right atrium (RA) [1, 4‐7]. This position has been associated with less incidence of early and belated life-threatening complications such as pericardial and pleural effusion, cardiac tamponade, endocarditis, cardiac arrhythmias, liver haematoma, necrosis or other parenchymal injuries, necrotizing enterocolitis, thrombosis and portal hypertension [4, 8‐10].

Antero-posterior chest radiography (CR) is the most commonly used method to locate catheter tip [11, 12] using as landmarks either the thoracic vertebral bodies or cardiac silhouette although a significant number of studies has questioned the accuracy of CR for this purpose [13‐17].

On the other hand ultrasonography (US) has been suggested in several papers as gold standard [13‐17] as it seems more reliable, faster and without side effects [13‐16, 18‐22]. US can be performed at the bedside during the insertion procedure (real-time US,) avoiding multiple catheter manipulations and allowing an immediate and safe injection of fluids and medications [7, 15, 18].

US also allows monitoring the UVC tip position over time, since tip migration has been described up to 50–90% of the cases [22, 23].

Despite all these proven advantages, US is still not widely used in many NICUs to assess the UVC tip position, possibly because it needs additional and adequate training of the medical staff. In many studies scan was performed by paediatric radiologists or cardiologists [14, 16, 19, 24, 25] that are not always available or on-call, but recent studies have suggested that training on the use of real-time US (RUS) is easy and feasible [15, 17, 25‐28].

In our Neonatal Unit, US is widely used by neonatologists and neonatal fellows: many of them are able to perform head US, echocardiography and lung US. Nevertheless US is not always routinely used for intraprocedural assessment of UVC tip position since not the whole medical staff is completely trained and skilled to it.

This pre/post-intervention study was designed to evaluate the feasibility of a basic, multimodal training of the medical staff, with the aim to implement the use of RUS to localize the UVC tip position.

Among the consultants and trainees 53 out of 67 (79.1%) doctors attended the training.

Sixty-six patients underwent umbilical venous catheterisation during the study period, 54 were enrolled and analysed: 26 infants in the pre-intervention phase and 28 infants in the post-intervention phase (Fig. 3).

The reasons for UVC positioning were the following: in the pre-intervention phase 7 babies needed an UVC for prematurity, 6 for birth asphyxia, 5 for respiratory distress syndrome (RDS), 3 for surgical conditions, 4 had intrauterine growth restriction (IUGR) with abnormal antenatal doppler, 1 had a cardiac arrhythmia, in the post-intervention phase 3 neonates needed UVC for prematurity, 5 for birth asphyxia, 13 for RDS, 1 for surgical condition, 4 for IUGR with abnormal antenatal doppler, 1 for suspected sepsis, 1 for isoimmunization.

Baseline characteristics of infants included in the study are listed in Table 2.

The primary and secondary outcomes are reported in Table 3: the use of RUS for tip location significantly increased after the training while the use of CR decreased, as expected. The average time to visualize the position of the catheter tip did also differ between the two phases since it was significantly lower in the post-intervention phase. The number of UVC manipulations in the first 24 h was not significantly different, while the UVCs placed during the post-intervention phase were more frequently placed at the IVC-RA junction. There was no significant difference in the other secondary outcomes (Table 3).

Twenty-two catheters located at the IVC-RA junction were evaluated over time with serial scans to study tip migration. Overall 11/22 infants (50%) experienced catheter migration. Ten catheters moved inwards into the right or left atrium and one moved outwards into hepatic vessels. The highest migration rates were registered on day 1 and day 3 (Table 4).

In 17 patients, who underwent CR for UVC tip location or for lung or abdominal disease, UVC tip position on US was compared to vertebral body (Fig. 4). As expected the location of UVC based on vertebral bodies proved to be unreliable [22].

A basic, targeted training on US-guided catheter insertion is effective in increasing the use of RUS and decreases the use of CR.

Physicians were able to learn the proposed technique for tip navigation and tip location after one theoretical lesson and multiple bedside practical sessions.

Our study demonstrates that a focused intervention, such as a targeted training, can increase awareness of the benefits and consequently implement the use of a technique that has already been validated as the gold standard for catheter tip location. To the best of our knowledge there are only few studies focusing on a well-established and specific training of the neonatal medical staff on the use of US in UVC line placing, one of which used an animal model [17, 31].

Of great interest in our paper is the reduction in the number of CR to visualize UVC. Several studies demonstrated that the use of lung US significantly reduced radiation exposure in preterm neonates admitted to NICU [32], and we speculate that the use of US-guided catheter procedures could further contribute to this purpose, especially in preterm babies which are likely the most vulnerable population with regard to the long-term effects of ionizing radiation.

Another interesting finding is that the use of RUS significantly reduced the time to visualize the UVC position and consequently the time needed to safely use this venous access device. According to the Infusion Nursing Society guidelines [7] clinicians have to verify tip location prior to start infusion. Infusion of high osmolality solutions like parenteral nutrition or medications like inotropes can be associated with severe complications in case of a high or low position of the catheter, so an immediate correct visualization of the UVC tip is crucial. Our study confirms that US is more accurate in regard to tip location when compared to CR. This finding is expected, in fact the location of the tip at x-ray is based on the relationship between the projection of the tip and some non-vascular radiological landmarks, such as the vertebral bodies and/or to the diaphragm. On the contrary, US can detect the position of the tip inside the vasculature with the best precision [15, 17, 24].

Migration of the UVC tip has also been documented and Franta et al. and Hoellering et al. recently demonstrated that it can occur up to 50% [22] or 90% [23] of the cases. It is commonly attributed to drying of the Wharton jelly and secondary shortening of the umbilical cord remnant. In our study half the infants experienced catheter migration. It occurred mainly inwards (in right or left atrium) between 24 and 48 h. We could not document any significant association with ventilation mode or other clinical parameters.

The execution of repeated US scans both for training purposes and to study catheter migration might create discomfort or instability, especially on preterm babies. Nevertheless we think that the discomfort and the stability of the patient must be balanced against the risk of malposition or migration of such catheters. Several reports [22, 23], including our findings, suggest that UVC migration is a quite frequent event. This is particularly important, especially in preterm infants, because migration and secondary malposition have been recently associated with the risk of NEC [33].

Considering our experience and previous results, we encourage the use of US not only for UVC placement but also for tip monitoring in order to avoid complications due to migration.

To the best of our knowledge this is the first study that completely focuses on and demonstrates the feasibility of a basic, multimodal medical staff training on the use of RUS for UVC localisation, with a significant impact on the routine clinical practice. Our targeted training protocol could be easily adopted by other tertiary care neonatal centres in order to achieve good results in terms of accuracy, reduction of radiation exposure and time-saving deriving from the use of RUS.

We believe that the following factors played a major role in achieving a positive outcome: identifying the problem and the incidence of catheter malposition, creating awareness of all the related complications, developing a targeted and basic training program, using multiple methods, easy-to-follow and with a reasonable duration, tracking the implementation process by weekly surveys among the trainees.

One limitation of this study is the relatively small number of patients. However, the sample size was enough to meet the study aims, particularly to demonstrate the feasibility of the training and to measure the increase in the use of RUS to assess UVC tips position.

The introduction of a targeted training for the medical staff on the use of RUS in NICU to guide UVC placement is feasible and resulted in an implementation of this technique with a reduction in the use of CR in our neonatal unit. US-guided umbilical line placement is a technique easy to learn, thus we encourage the introduction of similar training protocols in neonatal units with the aim to adopt RUS. We further suggest regular US evaluation of UVC position since catheters migration occurs very often and it is potentially related to severe complications.