Defining central venous line position in children: tips for the tip

Introduction

The main problem inserting a central venous line is to determine its position. The most used method is X-ray/fluoroscopy, but other radiological and nonradiological techniques are available to both predict the necessary length of insertion and to locate the tip position. Purpose of this review is to analyse literature related to the position of centrally inserted central venous catheters and to review topics related to tip positioning of those catheters in children. Applications of specific techniques to PICCs and umbilical venous catheter (UVC) will also be reviewed.

Materials and Methods

We analysed 68 original manuscripts, 46 were available as full text and 22 as abstracts. Forty-two were specifically related to the paediatric population and 26 to the adult population. The papers analysed were published between 1949 and 2014. All articles were written in English language except one in Italian and one in German.

Results

Recommended CVC tip position

Royal College of Nursing (RCN) (1), British Committee on Standards in Haematology (BCSH) (2) and American Society of Anaesthesiologists (ASA) (3) stress that the recommended tip position is the lower third of the superior vena cava (SVC) or the junction between the SVC and the right atrium (SVC-RA junction). The U.S. Food and Drug Administration recommended that ‘the catheter tip should not be placed in, or be allowed to migrate into, the heart’ (4) and the National Association of Vascular Access Networks stated that the tip of PICCs should be located in ‘the lower one-third of the SVC, close to the junction of the SVC and right atrium’ (5). The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) (6) recommends a different approach for haemodialysis catheters: for long-term venous access, the recommended tip position is the RA, and for short-term venous access the recommended position is the SVC. European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines, finally, consider the atrial position of the tip as acceptable and do not give specific indications (7).

The only guidelines available specifically related to the paediatric patient are issued by the Great Ormond Street Hospital (8) and the Pediatric Special Interest Group of AVA (Association For Vascular Access) (formerly Pedivan) (9) and both agree in recommending the positioning of the catheter tip in the SVC or at the SVC-RA junction.

The decision to set the catheter tip either in the SVC or at the SVC-RA junction instead of placing it in the RA has been supported to avoid a possible increase in catheter-related complications. The complications linked to catheter tip position are catheter-induced perforation/tamponade, thrombosis and catheter-induced arrhythmia.

Cardiac tamponade

Darling and colleagues (10) reported five cases of tamponade occurring in one neonatal unit over a 4-year period, caused by the placement of tip in the RA. The author also points out that catheter angulation, curvature or looping, which was present in all five cases, is a major risk factor for perforation. Weil and colleagues (11) reported six cases of pericardial effusion causing cardiac tamponade: in five of the six patients affected, the chest X-ray showed that the catheter tip was overlying the cardiac silhouette. It is also important to stress that other authors recorded cases of pericardial effusion and cardiac tamponade even if the catheter tip was not placed in the RA. Onal and colleagues (12) reported the case of a newborn affected by cardiac tamponade after umbilical venous catheterization: the authors stress that correct position never guarantees uneventful catheterization.

Thrombosis

Due date only one paper analysed the incidence of thrombosis in relation to catheter tip position in children and adolescents: Revel-Vilk and colleagues (13) found out an increased risk of catheter malfunction related to thrombosis in CVC placed in the SVC. The researchers analysed 423 CVCs inserted into 262 oncologic patients for a total of 76,540 catheter days: they found an increased risk of catheter-related deep vein thrombosis when the tip was placed in the SVC instead of being placed in the RA or at the SVC-RA junction. The calculated hazard ratio was 1.64 with a 95% confidence interval between 0.35 and 7.82.

Estimating the length of insertion

All insertion procedures are performed after estimating the length required to reach the desired position of the tip. Usually, a quick evaluation is performed looking at external anatomic landmarks, but different approaches have been described in the paediatric population using both formulas and anatomic landmarks. A summary of such methods is reported in Table I.

TABLE I -

Summary of the main studies related to estimation of length of insertion of cvc in children

	Validation	Recommendation	Success rate
CVP = central venous pressure; TV = thoracic vertebrae; AP = antero-posterior; SVC-RA = superior vena cava- right atrium (junction); SK = apex of muscular triangle formed by the sternal and clavicular heads of the sternocleidomastoid muscle; ICS = intercostal space; TEE = transesophageal echocardiography; BSA = body surface area; IJ(V) = internal jugular (vein); RIJ = right internal jugular (vein); SC = subclavian; RS = right subclavian (vein); LS = left subclavian (vein).
Hayashi et al (1995) (15)	158 patients included. Correct position confirmed by AP chest X-ray (TV used as a marker). RIJ access only.	Use patient height to estimate length of insertion. The author provides specific table.	Considering appropriate a position between vertebrae T 3-4-5 138/158(87%) catheters were properly positioned (41, 63, 34 respectively, for T 3-4-5).
Andropoulos et al (2001) (16)	456 insertion procedures evaluated (330 RIJ 126 RS). Position confirmed by AP chest X-ray. Position of the SVC/RA junction evaluated from AP chest X-ray and distance from insertion point calculated. Relationship evaluated with regression analysis. RS access only.	Estimate initial insertion length from height: patients <100 cm: (height in cm/10) -1 patients >100 cm: (height in cm/10) -2	Estimated as if these criteria were applied to the insertion procedures used for calculation: - Total: 97% - SC access: 93.1%- IJ access: 99.1%
		Estimate length of insertion based on patient weight. The author provides specific table.	Estimated as these criteria were applied to the insertion procedures used for calculation: Tot: 98% SC: 94% IJ: 99.4%
Kim et al (2003) (17)	83 insertion procedures evaluated. Position confirmed by AP chest X-ray. Position of the SVC/RA junction evaluated from AP chest X-ray and distance from insertion point calculated. Relationship evaluated with regression analysis. RIJ access only.	Estimate length of insertion using the distance between standardised insertion point (SK) and 3rd ICS. Optimal depth of insertion: SK-ICS (cm) -1	Estimated as these criteria were applied to the insertion procedures used for calculation: CVC position above the right atrium in 98.8% of the cases.
Yoon et al (2006) (18)	60 insertion procedures evaluated. Position confirmed by TEE intraoperatively. Distance between insertion site and SVC/RA junction calculated Relationship evaluated with multiple regression analysis. RIJ access only.	Estimate length of insertion using height of the patient: 1.7 + (0.07* height[cm])	Estimated as these criteria were applied to the insertion procedures used for calculation: CVC position above the right atrium in 97.5% of the cases.
Na et al (2009) (19)	90 insertion procedures evaluated. Length of insertion estimated from anatomic landmarks. Position confirmed by Chest radiograph using the carina as a landmark. RIJ access only.	Defining two points: A: sternal head of the right clavicle B: midpoint of the perpendicular line drawn from Point A to the line connecting both nipples. The ideal length of insertion can be calculated: (I-A distance + A-B distance) -0.5	Mean distance of the CVC tip from the carina level was 0.1 95% CI: 0.1 cm below the carina -0.3 cm above the carina
Shah et al (2012) (20)	69 insertion procedures evaluated. Length of insertion calculated using ECG method (guidewire technique). Confirmed by surgeon during open heart operation. Relationship evaluated with regression analysis. RIJ access only.	Estimate initial insertion length from height: patients <100 cm: (height in cm/25) + 2.5 patients >100 cm: (height in cm/10)-4	Not reported
Witthayapraphakorn et al (2013) (21)	165 CT scans evaluated to estimate ideal length of insertion. Ideal distance calculated as sum of skin-IJV distance and IJV distance and level of the carina or level of the SVC-RA junction.	Estimated length to the SVC-RA junction (cm): 6.4 + 2.8 (BSA [m2]) + 0.022 [age (month)]	Authors provide a table to compare results obtained with this formulae and other methods (eg Andropoulus formula (16))
		Estimated length to the level of the carina (cm): 4.9 + 2.7(BSA [m2]) + 0.013[age (month)]
Stroud et al (2014) (14)	727 insertion procedures considered retrospectively, 514 left and 213 right. Location of the RA/SVC junction estimated from chest X-ray and length of the catheter mesured. Relationship with biological variables evaluated with regression analysis. RS and LS access only	Estimated length of insertion is: left SC CVC: (6.5*BSA) +7 cm right SC CVC: (5*BSA) +6 cm	Defined an ideal distance range evaluating 200 randomly selected chest X-ray tip position is estimated to be correct in: 92.9% if BSA <0.5 95.7% if BSA >0.5

No method can be considered 100% correct and each guideline available recommends a different specific technique to identify tip position during or after insertion. None of the previously presented methods have been evaluated and tested in a controlled standardized environment.

Radiographic landmarks

In the paediatric population, only a few researchers discussed the validity of radiographic landmarks for the correct placement of central venous catheters. In 2005, Yoon and colleagues (22) studied 57 right internal jugular vein catheterization in infants and children: the researchers placed the catheters using a trans-oesophageal echocardiographic probe to ensure that the tip lay at the SVC-RA junction, than a chest A-P X-ray was taken to evaluate whether the carina could be used as a radiologic landmark. Conclusion is that the carina can be used as a radiographic landmark for the proper CVC tip placement in paediatric patients. In 2006, Albrecht and colleagues (23) evaluated the position of the carina in 31 fresh cadavers of small children (mean age at the time of death was 12.5 ± 3.4 months) concluding that the carina itself is located 0.5 ± 0.04 cm above the pericardial duplication as it transverses the SVC. A similar study was conducted in 2007 by Inagawa and colleagues (24) and considered a sample of nine neonatal fresh cadavers (median post-conceptional age at autopsy was 35 weeks, range 23-42) concluding that in newborns, the carina is not always located above the pericardium and cannot be considered a valid anatomic landmark. In 2008, Baskin and colleagues (25) evaluated the anatomic relationship of thoracic structures analysing 100 computed tomographic studies from a predominantly paediatric population (52 males and 48 females, mean age 16 years, range 12-28). The researchers evaluated the use of vertebral units (distance between the inferior endplate of one vertebra to the inferior endplate of the next) to define appropriate catheter tip position and concluded that a point two vertebral body units below the carina enables the reliable estimate of the position of the cavoatrial junction. The researchers stress that the radiological measurement of the position of cavoatrial junction should be identified in a lower position than previously believed. Although this method does not consider the parallax effect, it might still be considered reliable because, as reported by the researchers, ‘the spine is only minimally affected by geometric magnification and is adaptive to somatic growth’. Kim (17) and colleagues studied the possibility of predicting the optimal length of the central venous catheter using a formula, the authors stress that, based on chest radiographs, ‘the right third intercostal space is at the level of the SVC/RA junction’. In this specific case, the target of the study was to define a formula to predict the length of insertion of the central venous catheter, not to identify a radiologic landmark.

Ultrasound scan

In 2006, Lanza and colleagues (26) studied the role of B mode and Doppler ultrasound in defining catheter position: the study analysed 107 consecutive central venous line placement procedures in a paediatric population of 107 patients (average age 31.7 days, range from 1 day to 7 years). The authors found that, assuming chest radiography as the gold standard procedure, post-procedural B-mode and Doppler ultrasound had a sensitivity of 84.6% and specificity of 100%; the negative predictive value was 97.9% and the positive predictive value was 100%. The concordance between sonography and chest radiography was 98.1%. The echocardiographic assessment identified 11 potential complications, all confirmed by chest X-ray; only two malpositions, both in the RA, were not detected by ultrasound. Internal jugular and subclavian approach were analysed. In these cases, the evaluations were performed by one radiologist, blinded to the radiographic findings. The identification of the catheter was performed with both grey-scale sonography and Doppler ultrasound images after injection of 2-3 ml of saline solution. The authors conclude that B-mode and Doppler ultrasound may be good substitutes for chest X-ray, reserving the X-ray to the cases in which a malposition is suspected after sonographic examination.

The role of ultrasonography has been widely considered in defining the position of venous lines in newborns. The first experiences of ultrasound application in evaluating venous line position in newborns dates back to 1987 when Diemer (27) reported his experience with 19 newborns who underwent a central venous line positioning procedure (from a peripheral arm vein or from umbilical vein or from subclavian vein). In all 19 cases, the inserted silastic catheter was identified by ultrasound, nine cases of malpositioning or looping of the catheter were identified and four cases of malpositioning were detected by ultrasonography but not by standard radiographic examination. In 1996, Madar (28) and colleagues found similar results analysing 40 intravascular catheter insertion procedures (18 umbilical arterial catheters; three UVCs; and 19 percutaneous silastic long lines). Specific studies have been subsequently conducted to evaluate the role of ultrasound in detecting PICCs tip position. Ohki and colleagues (29) in 2000 compared the efficacy of ultrasound and standard radiography in identifying the position of very thin (0.4 mm outer diameter) percutaneous central venous catheter in newborns. Fifty-seven CVCs were studied in 44 infants: in 87% of the cases, the ultrasound was able to identify the catheter tip, missing in only three cases. The authors also stress that ultrasound was able to identify 78% of cases of catheter tip dislodgement. The authors conclude that ‘US provides precise information about the PCVC tip position in relation to vascular structure and contributes to safer positioning of the PCVC than traditional radiography alone’. The authors also state that, with ultrasound, the PICC tip position can be evaluated during the infant’s movements, which is a huge advantage over standard chest X-ray. In 2009, Nicole Sneath (30) reviewed the available methods to assess the tip position of PICCs also considering ultrasonography as an option. The author concluded the evaluation pointing out that the results available from the previously published trials are probably not generalizable due to the small size of the samples and that more studies are needed to assess the validity of ultrasonography. In 2012, Jain and colleagues (31) compared the use of targeted neonatal echocardiography (TnECHO) and the chest X-ray to choose the latter (in contrast with the previous approaches) to better identify PICCs tip position. The authors found a 59% (13/22 infants) concordance between the two methods and defined a 64% sensitivity and 55% specificity of radiographs in determining malposition of the central line. The authors conclude that ‘TnECHO is a useful tool in identifying tip position, performing real-time manipulation, and minimizing exposure to further radiographs’. Finally, in 2013, Tauzin and colleagues (32) compared echocardiography and plain radiographs in defining PICCs tip position in low birth weight newborns. The authors examined the placement of 109 catheters in 89 infants; the placement of these catheters was controlled by echocardiography and by plain radiograph. In 25% of the cases identified as appropriately positioned by plain radiograph, the tip was then echocardiographically identified within the heart and was repositioned. The authors concluded that echocardiography, coupled with initial plain radiographs, should be the gold standard for assessing PICC tip positions in low birthweight infants (see Tab. II).

TABLE II -

Summary of the main studies related to ultrasound detection of piccs tip in newborns

	Population/Purpose	Technique used	Success rate
PICCS = peripherally inserted central catheter; TnECHO = Targeted Neonatal Echocardiography; LBW = low birth weigh.
Diemer et al (1987) (27)	19 catheters: 9 PICCs; 6 subclavian; 4 umbilical venous. Evaluate the role of sonography to reduce radiographic controls for tip position.	3.0 MHz probe WINDOWS: subcostal four chamber way for all studies. Other for specific cases.	19/19 tips identified.9/9 cases of malposition detected, 4 of which not detected by standard X-ray.
Madar et al (1996) (28)	40 catheteres: 18 umbilical arterial; 3 umbilical venous; 19 percutaneous. Evaluate cross-sectional ultrasound in identifying catheter tip.	7.5 MHz probe WINDOWS: not specified.	38/40 tips identified. X-ray identified all 40 catheters. 1/40 was located high in the VC, 1/40 was properly placed but ultrasound could not detect it (distended abdomen).
Ohki et al (2000) (29)	57 PICCs.Assess ultrasound ability to identify thin PICCs.	12 or 10 MHz probe WINDOWS: not specified. All studies performed by the same examiner.	87% tips identified. 78% of dislodgement identified.
Jain et al (2012) (31)	22 PICCs. Compare TnECHO with radiographic study in locating tip of PICCs.	TnECHO	59% concordance between the two techniques. 5 cases wrongly interpreted by X-ray study.
Tauzin et al (2013) (32)	109 PICCs in low birth weight infants. Compare ultrasound and radiography in locating tip of PICCs in LBW infants.	5-12 Hz multifrequency probe. All studies performed by the same examiner.	25% of cases identified as properly positioned by X-ray was identified as malpositioned with ultrasound.

There are also few examples of the application of ultrasound in detecting UVC tip. In 1982, Oppenheimer and colleagues (33) described 15 sonographic localization procedures performed in five children with an UVC. In 12 cases, the tip of the catheter was identified. The authors also describe a similar experience with 100 arterial umbilical catheters. In 1995, Greenberg and colleagues (34) compared 95 radiographs and ultrasound studies for 79 patients who underwent an UVC positioning: 60 evaluations of tip position were performed with standard chest X-ray and 35 with ultrasound. The authors stress that real-time ultrasound offers some advantages over standard X-ray: it allows an immediate and precise evaluation of tip position with the injection of a small amount of fluid and does not expose the baby to radiation. In 2011, Simanovsky and colleagues (35) used a different method to compare ultrasound and standard chest X-ray to evaluate tip placement of UVC: they measured the distance between the diaphragm and the tip of the catheter and compared the measurements performed with the two methods. Of the 75 cases analysed, in 46, the two measures were identical; in the other 29, a difference of 1-7 mm was recorded. Ultrasound was also able to identify three cases of catheter malposition that was not evident at plain chest X-ray. Michel and colleagues (36) in 2012 compared thoraco-abdominal X-ray (TAX) and ultrasound to show path and tip position of UVC in newborns: 60 cases were evaluated (mean gestational age 34.7 ± 4.2 weeks); sensitivity and specificity were 93.3% and 95.6% for US and 66.7% and 63.0% for TAX (p<0.001), respectively. The authors conclude that US examination is superior to TAX in determining UVC tip position.

Electrocardiography

Serafini and colleagues (37) in 1985 reported the first example of ECG positioning technique in children. They describe the application of the column of saline technique in 52 children needing antineoplastic chemotherapy. The authors stress that this technique may avoid chest X-ray control. Three years later, Hoffman and colleagues (38) experimented this technique on 50 patients obtaining a success rate of 96% and 100% accuracy. The two failures reported were due in one case to technical malfunction and in one case to the presence of a supraventricular arrhythmia. Redo and colleagues (39) in 1993 reported a series of 384 insertion procedures in newborns and children guided by the ECG technique. Again, the technique success rate was 95%. In 1994, Zachariou and colleagues (40) evaluated the efficacy of ECG positioning (column of saline technique) in 77 Broviac implantation procedures comparing this technique with the standard X-ray they reported a specificity of 100% and a sensitivity of 81% for the ECG method. In 1997, Parigi and Verga (41) reported the results of a 10-year experience with the ECG technique described by Serafini (37) 12 years earlier. The authors reported the results of 807 CVC positioning procedures in 771 children: no false negative or false positive results (except for one case of error in connecting up the electrocardiograph monitor). In the 17 (2.1%) cases in which the P wave deflection was not detected, radiological checking showed that the catheter had been malpositioned (e.g. it was in the controlateral subclavian vein). In 1999, Simon and colleagues (42) reported their experience of 23 insertion procedures using the guidewire technique: in 20 of the 23 children, the proper position of the catheter was confirmed by chest X-ray, in three cases, the necessary atrial signal was not detected. In one case, a technical error was responsible for the failure, and in two cases, the catheter was malpositioned (subclavian vein/pleura). Finally, Weber and colleagues (43) in 2013 used a commercialized endovascular ECG-system (Alphacard®) in 50 patients: in 44 cases, the CVC was properly placed at first attempt, while in six cases, this approach failed mainly due to nonsufficient length of the catheter or doubt related to the reliability of the technique (Tab. III).

TABLE III -

Summary of the main studies related to ecg detection of cvc tip in children

	Population/Purpose/Method	Success rate
CVC = central venous catheter; ECG = electrocardiography.
Serafini et al (1985) (37)	52 CVC insertions. Describe the endocavitary technique to localise CVC in children Column of saline technique.	The author reports 52 successful procedures. No X-ray control.
Hoffman et al (1988) (38)	50 CVC insertions. Describe the technique and report possible failures. Column of saline technique.	96% success rate. 100% accuracy. 1 failure due to malfunction. 1 failure due to SV arrhythmia.
Redo et al (1993) (39)	384 CVC insertions: 150 internal jugular vein; 218 external jugular vein; 11 cephalic vein; 5 axillary vein. Describe the applicability and success rate of this technique. Column of saline technique.	95% success rate. Radiographic control in recovery room confirmed position.
Zachariou (1994) (40)	77 CVC insertions. Compare CVC technique with standard chest X-ray. Column of saline technique.	72.6% success rate at first attempt. 13 cases identified as non properly positioned by both ECG and X-ray. 3 cases defined as properly positioned by ECG but found malpositioned by X-ray. ECG specificity: 100%. ECG sensitivity: 81%.
Parigi and Verga (1997) (41)	807 CVC insertions. Describe 10 years experience with ECG technique. Column of saline technique.	ECG specificity: 100%. ECG sensitivity: 100%. One case of malfunction. 17 cases of malposition detected (2.1%), confirmed by radiographic control.
Simon at al (1999) (42)	23 CVC insertions. Presentation of 23 insertions with guidewire technique.	20/23 successful insertions. 3 failures: 1 malfunction, 2 malpositioned catheters.
Weber et al (2013) (43)	50 CVC insertions. Presentation of 50 insertions with guidewire technique.	44/50 successful insertions. 6 failures: in five cases CVC too short or the anaesthetist did not trust the ECG-method; in one case an unknown anatomical anomaly was present.

This approach has also been experimented in newborns: Neubauer reported the first examples of the application of this technique in this particular patient population. In 1991 (44), he described the results of 50 insertion procedures in infants weighting less than 1000 g being successful in 45 cases: with the remaining five catheters went into an ideal position by withdrawing 1-2.5 cm. In 1995 (45), the same author describes an extensive experience of 535 central venous catheterization procedures in a neonatal intensive care unit: of the 535 procedures performed, 273 took advantage of the ECG positioning method. The author concludes that CVC placement with ECG monitoring is a suitable method to reduce malpositioning; he also reports that there were no side effects specifically related to the ECG method.

Finally, we found two examples of the application of the ECG technique to UVC catheterization in newborns. In 2000, Biban and colleagues (46) compared the ECG method (using a specific conductive device Vygocard; Medival, Padova, Italy) with the standard landmark method in 44 patients (22 insertion with one method, 22 with the other): X-ray confirmed the position of the catheters. Tip placement was more accurate with ECG technique (88% of successful insertion procedure vs. 55%). In 2005, Tsui and colleagues (47) applied the column of saline technique to eight UVC insertion procedures. Five catheters were placed at first insertion, and X-ray confirmed three cases of malposition supposed through ECG recording. The catheters were then repositioned and X-ray confirmed the correct tip placement.

Discussion

What is the best position?

The best position of central venous catheter tip is a subject that has been widely discussed in the past (48). It seems that all the major recent guidelines, at least for the adult patient, recommend positioning the tip of the catheter in the SVC or at the junction between the SVC and the RA.

Cardiac perforation and tamponade

Due date [similarly to what was reported for the adult patient by Rutherford and colleagues (49) and reiterated by Vesely (48)], there is no clear evidence to support an increased risk of cardiac tamponade in case of right atrial placement of the catheter tip. It is although important to stress that the choice of positioning the tip in the SVC or at the junction between the SVC and the RA is based, in the paediatric population, on common sense and on a precautionary principle. The choice made by the KDOQI committee to recommend the placement of short-term CVC tip in the RA depends on the need of a very high flow rate to sustain haemodialysis.

Thrombosis

The risk of thrombosis related to the position of the catheter tip has been extensively discussed without finding a clear evidence to support either position (SVC or RA). As pointed out by Vesley (48), catheter-related thrombosis depends on many factors. From a biological point of view, a catheter tip in a vein is perceived by the coagulation system as a foreign body and induce the deposition of fibrin and platelets activation. So, we should record an increased risk of catheter-related deep vein thrombosis if the tip is placed in the SVC. The consequences of this biologically plausible chain of events have been clinically observed by researchers in the adult population (50-51-52), but the evidence of its occurrence in paediatric population is not known. Actually, there is no strong evidence to support the fact that a catheter placed in the SVC is more prone to coagulation than one placed in the RA. It is also difficult to assess whether there is a difference of thrombosis risk between the SVC, the junction between the SVC and the RA and the RA itself and whether this difference is clinically relevant.

Defining tip position

As already pointed out, the most accepted method used to define tip position is the chest X-ray or fluoroscopy as recommended by all recent guidelines available. Many different methods have been described in literature to identify tip position, both radiological and nonradiological. Many landmarks have also been described to certify tip position with fluoroscopic and radiographic methods. The importance of setting tip position accurately is demonstrated both by the attention posed by guidelines in recommending a postoperative radiographic control and by the incidence of primary malposition. The incidence of this kind of malposition is estimated to be between 2 and 30% in the overall population depending on implantation technique and methods used to identify it (53). Only few guidelines state that a radiological control might be avoided in optimal conditions: in absence of risk of pneumothorax and if the position of the tip was verified via other methods during the procedure. The radiographic control might be avoided only if the insertion is performed under sonographic guide and a specific method is used to assess tip progression and final position.

Chest X-ray and fluoroscopy: which landmark?

As mentioned, radiographic and fluoroscopic methods are considered the standard in defining catheter tip position. Researchers discussed the role of anatomic landmarks to locate the lower third of the SVC or the SVC-RA junction. The landmarks proposed with standard chest X-ray are the fifth-sixth thoracic vertebrae [defined as the ideal position of the CVC tip by Defalque and colleagues (54)], the inferior border of the clavicles [defined as the landmark to identify the origin of the SVC by Greenall and colleagues (55)] and the angle between the right main bronchus and the trachea [reported as the ideal landmark to identify the lower SVC or the junction between RA and SVC by Rutherford and colleagues (49) and by Schuster and colleagues (56)]. Radiographically, the SVC-RA junction could be identified through the characteristic widening of the right mediastinal border: this radiologic landmark is not validated and is usually considered unreliable. It is also worth mentioning that an MRI study conducted by Aslamy and colleagues (57) stressed that the right tracheobronchial angle is the most reliable landmark for the upper margin of the SVC. These findings are also corroborated by the fact that the right tracheobronchial angle is located in the same plan as the SVC, reducing the parallax effect.

From the reviewed literature, the evidence is not sufficient to support the choice of the carina as a landmark for proper CVC placement in the paediatric population. On the contrary, there is actually no other radiological landmark allowing a proper estimate of CVC tip position.

Ultrasound: an alternative for PICCs in neonates?

Trans-oesophageal echocardiography has been used in the past to identify catheter tip position, but is considered a too expensive and invasive procedure to be applied universally (25). Recently, in the adult population some researchers tried to evaluate the role of various ultrasonographic methods to locate tip position/malposition. In 2010, Vezzani and colleagues (58) compared B-mode ultrasound and enhanced ultrasonography with the standard chest X-ray to identify catheter position and catheter induces pneumothorax. Ultrasonography and contrast-enhanced ultrasonography combined yielded a 96% sensitivity and 93% specificity in detecting catheter misplacement. Concordance with traditional radiographic technique was 95%. All ultrasonographic examinations were performed by the same operators and initially visualized subclavian vein and internal jugular vein, then the heart and the SVC. In 2013, Zanobetti and colleagues (59) evaluated the role of ultrasonography to identify tip position and catheter-related complications and compared it with standard chest X-ray. The researchers found a high concordance between the two methods and a high sensitivity (94%) and specificity (89%) for ultrasonographic identification of catheter tip malposition. The same operators who performed the insertion performed the scan and all involved physicians received a standardized specific training. In all cases, jugular and subclavian vein were scanned and heart chambers visualized. In 2013, Kim and colleagues (60) explored the feasibility of a right supraclavicular ultrasonographic view of the lower SVC as a landmark for real-time ultrasound-guided CVC tip positioning via the right internal jugular vein. This approach was feasible in all the 51 patients enrolled. A standard Chest X-ray was than evaluated to confirm the position of the tip in the lower SVC. The authors concluded that ‘Ultrasound via a right supraclavicular view is a feasible, well tolerated and accurate approach and should be further explored’. In 2014, Cortellaro and colleagues (61) evaluated the role of contrast-enhanced ultrasound to define catheter tip malposition concluding that ‘CEUS can’t substitute CXR’. In this specific case, two operators were involved and the acoustic windows used were subcostal and apical (when the subcostal was not available). The scan was initially performed with B-mode ultrasonography and CEUS was subsequently performed.

There are few trials evaluating the role of ultrasound in defining tip position in the adult patient, and only one study evaluating such a technique in the paediatric population, so no recommendation can be given. The role of ultrasonography to identify PICCs tip position in newborns has been investigated: even if there is not enough evidence to support the routine use of ultrasound, the advantages of real-time ultrasonography are clearly very important. As pointed out by many authors (29-30-31), the two main advantages of this technique are the immediate possibility to correct a malposition and to check the position of the tip during the movements of the baby's body. This technique has not been studied in a general paediatric population, but the advantages related to its application might be important considering the potential issues related to catheter malposition with body movements (62). It is also important to stress that the results reported in the papers analysed may not be generalizable due to small sample size and due to lack of standardization of the detection procedure. Another aspect to consider is that ultrasonography is known as an operator-dependent technique, and with small populations of patients, this aspect may be particularly underestimated. Further studies, with standardized technique and a larger population, should be implemented to evaluate the role of this approach. The same considerations may be considered valid to evaluate the role of ultrasound to detect tip position of UVCs.

The ECG method: an alternative to chest X-ray in children?

The use of electrocardiography to identify tip position has been widely investigated, both in adult and paediatric population. Two main methods have been described and used: the metal guidewire technique, which uses a specific equipment with an integrated electrode, and the column of saline technique, which is applicable to all catheters. The column of saline method was first described in 1949 by Hellerstein and colleagues (63); it was then experimented later on and finally accepted clinically in the 80s (64-65-66). Since then, this method has been used mainly in the European regions, particularly in Germany, and it is actually not recommended by international guidelines, even if it has been proved effective. In 1993, Salmela and colleagues (67) challenged this method using it on 350 patients: in 29 patients, the technique failed, nine of those had a myocardial pathology, in two the catheter looped and in the last 18, the 20-cm catheter proved to be too short. The method was then tested in different research settings (68, 69). The two available techniques were also compared by Cheng and colleagues (70) in 2002: the guidewire technique versus the column of saline technique (sodium bicarbonate) placing port-a-cath catheters. The authors found no obvious difference between the techniques in catheter tip placement time and the measured optimal catheter length. In 2004, Pawlik and colleagues (71) compared the two techniques again, finding different results: the researchers found that the two techniques are comparable in terms of tip position detection, but the ECG quality seemed to be better using the guidewire technique. Finally, in 2009, Kremser (72) and colleagues analysed the differences between the two techniques using 227 insertion procedures. The authors found that the two methods gave significantly different results regarding the position of the line tip: the guidewire technique underestimated the necessary insertion by a mean of 21 mm for internal jugular vein approach and 10 mm for the subclavian approach. Different authors tried to compare the efficacy of ECG techniques and other available methods: Watters and colleagues (69) compared the efficacy of fluoroscopy and ECG, defining the ECG as a good alternative to fluoroscopy; Chu and colleagues (73) compared superficial landmark technique with the ECG method, finding the ECG much more accurate. The same was done by Lee and colleagues (74): the authors found that the two methods, landmark and ECG, were comparable in terms of efficacy in correct positioning of the catheter tip. Feasibility and safety of this technique was recently evaluated by different authors: Pittiruti and colleagues (75) evaluated the role of ECG (both guidewire technique and column of saline technique) on 1444 catheter insertion procedures. Excluding the patients who had an undetectable p-wave preoperatively, this technique was applicable in 99.3% of the cases analysed. Schenck and colleagues (76) analysed 316 cases concluding that intra-atrial ECG technique to judge correct tip positioning for central venous port implantations is simple and economical. Pittiruti and colleagues (53) also reviewed the evidence related to ECG positioning of central venous lines, concluding that the main advantages of this technique are patient safety, applicability to all catheters; applicability to the majority of patients and accuracy.

From the literature analysed, the role of ECG method to locate tip position in paediatric population has been strongly underestimated in the past: even if this technique was described more than 60 years ago, its applications have been limited to the European region and particularly to Germany and Italy. This technique offers many advantages:

Technically, this approach provides a quick and reliable method to track the position of the catheter during the insertion procedure, potentially reducing the need for repositioning.

Provided that an adequate ECG monitor is available, it is widely applicable (53):

There are different pre-packed kits available for the guidewire technique.

The column of saline procedure is virtually applicable to all catheters on the market.

Basically, all patients with a detectable P-wave at preoperative ECG could benefit of this approach (38, 53, 67).

It is economically advantageous: if validated, it can save the post-procedural X-rays reducing costs and logistic effort. An effective cost reduction has been evaluated when the ECG is compared with a standard landmark procedure followed by chest X-ray (69). Weber and colleagues (43) also stressed that this approach might shorten the procedure.

It is safe for the patient: this technique can significantly reduce the major risk of death related to CVC insertion (cardiac perforation) (77) and can significantly reduce radiation exposure, a very important aspect for children and newborns (78-79-80).

There are other three important aspects that emerge from the literature currently available that have been poorly evaluated:

This technique requires virtually no investment: Hoffmann (38) stresses that ‘The method utilizes equipment found in most operating room departments’.

This technique seems to have a relatively small learning curve. Hoffmann (38) points out that ‘The method utilizes equipment found in most operating room departments, is easily learned and taught [...]’. Zachariou and colleagues (40) write ‘After a learning period of eight implantations we began with this prospective study’ indirectly stressing that the procedure is easily learned. Simon and colleagues (42) stress that the column of saline technique is ‘effective but complex’ preferring the guidewire approach.

This procedure seems to be much less operator dependent than ultrasound and the interpretation of the ECG record seems to be quite immediate.

Even if in the general paediatric population some papers describe very large series (e.g. 807 insertion procedures), the results may be not generalizable due to the small dimensions of the sample included in the majority of the studies published due date.

Conclusion

So far, no guideline recommends the use of a technique different from radiography/fluoroscopy to confirm CVC tip position in children. Analysing the literature currently available, it seems that two important alternatives are under evaluation in clinical practice: the use of ultrasound to detect PICCs tip position in newborns and the applications of the ECG method in assessing catheter position for the general paediatric population.

Even if no specific recommendation can be given due to the low level of evidence, we strongly suggest to consider ultrasound and ECG techniques as a potential alternative to chest X-ray and to implement further studies to define their role. A wider application of this techniques may reduce neonatal and paediatric exposure to radiations and reduce costs.

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