1 Department of Anaesthesiology and Intensive Care Medicine, 2 Department of Neonatology and Pediatric Intensive Care Medicine, 3 Institute of Psychology, and 4 Institute of Diagnostic and Interventional Radiology, Friedrich-Schiller-University of Jena, Bachstrasse 18, D-07743 Jena, Germany
Corresponding author. E-mail: cwsm.schummer@gmx.de
Accepted for publication: June 11, 2003
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Abstract |
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Methods. Of 114 patients, 53 were randomized to right and 61 to left internal jugular vein catheterization using a triple lumen catheter. Three methods to ascertain catheter tip position were sequentially applied in each patient, and the insertion depths (ID) obtained using each of the three methods were recorded: (i) ECG guidance with a Seldinger guide wire (ID-A); (ii) ECG guidance with saline 10% used as an exploring electrode (ID-B); (iii) from position ID-B, the catheter was rotated and advanced until all three lumina could be aspirated easily. The catheter was fixed in that position (ID-C). To determine final catheter tip position, intraoperative transoesophageal echocardiography (TOE) and a postoperative chest X-ray (CXR) were performed.
Results. The depth of insertion of a catheter using the three methods varied significantly in left-sided (P<0.001), but not in right-sided catheters. Forty-eight of 57 (84%) left-sided CVCs, correctly positioned according to ECG guidance, had to be advanced further to achieve free aspiration through all three lumina. By this stage, five of the catheter tips had been positioned in the upper right atrium as demonstrated by TOE. There were 13 malpositions (23%) after left-sided insertion. In nine catheter malpositions, undetected by ECG guidance, the angle between the catheter tip and the lateral wall of the superior vena cava exceeded 40° on CXR.
Conclusions. Intra-atrial ECG does not detect the junction between the superior vena cava and right atrium. It is not a reliable method for confirming position of left-sided CVCs. Post-procedural CXRs are recommended for left-sided, but not right-sided CVCs.
Br J Anaesth 2003; 91: 4816
Keywords: heart, catheterization; measurement techniques, echocardiography, transoesophageal; monitoring, electrocardiography; veins, jugular
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Introduction |
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Nowadays, ECG-guided CVC-placement is considered to be a useful and safe method to ensure extra-atrial catheter tip position.4 In patients in our intensive care unit, we noticed a high incidence of critical catheter tip positions (angle >40°) in left-sided CVCs placed by means of ECG guidance. Therefore, we designed a study to compare CVC positioning via the right (Group R) and left internal jugular vein (Group L). Two methods of ECG-guidance were tested. The catheter was then advanced and rotated until free aspiration of venous blood through all lumina was possible. The final position of the CVC tip was determined by a transoesophageal echocardiogram (TOE) and postoperative portable chest X-ray (CXR). Our hypothesis was that ECG-guidance is not a suitable tool for correct placement of left-sided CVCs.
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Materials and methods |
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The final position of all CVC tips was checked intraoperatively by TOE, and after surgery by portable CXR. The correct position of the catheter tip was considered to be in the superior vena cava or at the superior vena cava-right atrial junction and parallel (<40°) to the superior vena cava wall, according to CXR and TOE. Malposition was considered to be a catheter tip placed in a vein other than the superior vena cava, or if the tip abutted the vein or heart wall at an angle >40°.
After induction of general anaesthesia, patients were put into the 20° Trendelenburg position for CVC insertion. The right (RIJV) or left internal jugular vein (LIJV), respectively, was punctured midway between the mastoid process and the sternal notch, just lateral to the carotid artery pulsation. The vein was entered using a sterile Seldinger technique, the guide wire was advanced and a triple lumen polyurethane CVC was introduced (Certofix® Trio SB 730, length 30 cm, 7 French). The kit includes a connection cable with a crocodile clip for connecting the guide wire to a Certodyn® universal adaptor (both B. Braun Melsungen AG, Melsungen, Germany). First, the guide wire was used as an unipolar electrode. A black marking on the proximal end of the guide wire indicates the point at which the tip of the wire is just level with the port of the distal catheter lumen. The sterile connection cable was clamped to the guide wire at the marked position in order to connect it to the adaptor that allows the operator to switch from a surface to an intravascular ECG. The catheter was then advanced, together with the guide wire, until an increase in P-wave size was detected. Both catheter and guide wire were then withdrawn until the P-wave returned to normal size. Markings on the catheter allowed the measurement of its depth of insertion (ID-A). The guide wire was then removed and the same procedure was repeated with the distal lumen filled with saline 10% using an Alphacard® (an electrical-conductive syringe with a cable and a cable joint for connection to the Certodyn® universal adaptor, B. Braun Melsungen AG, Melsungen, Germany). The electrically conductive liquid in the venous catheter lumen served as the intravascular electrode in this procedure (saline 10% has a higher conductive capacity than normal saline).6 The insertion depth was recorded again (ID-B). Then all three lumina of the catheter were tested for free back flow of venous blood. If there was any difficulty in aspirating venous blood, the catheter was rotated by up to 360°. If problems persisted, the catheter was advanced by 1 cm. The whole procedure of aspiration, and turning and advancing the catheter was repeated until no difficulty in aspirating the lumina was detected. At this position, the catheter was sutured to the skin, and the final insertion depth was recorded (ID-C).
After placing and testing the CVC, the TOE probe (multiplane probe, 6,2 MHz/HP Sonos 5500, Philips, Andover, MA, USA) was inserted to a midoesophageal position and rotated to the right (clockwise). Then the plane of the probe was turned to an angle of 90110° to produce a bicaval view according to the American Society of Echocardiography/Society of Cardiovascular Anesthesio logists (ASE/SCA) guidelines.7 The echocardiographic correlate of the superior vena cava-right atrial (SVC-RA) junction was defined as the base of the superior edge of the crista terminalis.8 9
A rapid flush of cephazolin 2 g in 20 ml normal saline (given for perioperative antibiotic prophylaxis) was used to identify the distal end of the CVC by TOE (Fig. 1). The microbubbles of the solution acted as contrast medium and helped to identify the catheter tip position in the superior vena cava. The catheter tip was usually identified as two closely spaced, parallel, bright echodense lines surrounding the darker fluid-filled lumen. The relationship of the CVC to the crista terminalis was recorded as a benchmark for the insertion depth. A second anaesthetist, blinded to the insertion depths of the CVCs, performed all the TOE examinations.
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Results |
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Fifty-three CVCs were inserted through the RIJV (Group R), and 61 through the LIJV (Group L). There were 13 malpositions, all of which occurred in Group L. Four aberrant catheter positions (one in the azygos vein, and three in right innominate vein) were detected by the intravascular ECG (Method A). After being correctly positioned, these cases were not included in further analysis. The depths of insertion of 57 of the catheter tips in Group L and 53 in Group R were analysed. Chest radiography revealed nine left-sided catheters with an impingement angle of more than 40° to the superior vena cava, but none in Group R (Table 2).
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Discussion |
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ECG-guided CVC-placement claims to detect the intra-atrial position of the tip of CVCs by detecting an intra-atrial P-wave (P-atriale) with the exploring electrode. The adjacent atrial wall tissue is thought to be responsible for the increase in voltage of the P-atriale.3 6 It is traditionally thought that either of the two methods using the catheter tip as an unipolar electrode produce similar results: an intraluminal wire or an electrolyte solution.12 13 Lack of an increase in P-wave size indicates aberrant catheter placement in vessels other than the superior vena cava.6 14 15
In our study, TOE served as the gold standard in assessing final CVC position with respect to the right atrium. In all patients where the CVC is visible below the entrance of the azygos vein into the superior vena cava, the tip of the CVC can be localized by TOE. The multiplane probe used allowed a three-dimensional assessment of catheter position in relation to the right atrium and superior vena cava without changing the transducer position.
ECG guidance led to correct positioning of all 53 CVCs inserted via the RIJV. In right-sided catheters, the three methods used to guide CVC placement (intraluminal wire (A) or fluid column (B), as well as the clinical test of free venous back flow (C)) all led to a similar insertion depth. No catheter tip with an angle >40° to the vessel wall was detected on CXR.
In contrast to Group R, there were 13 out of 57 malpositions (23%) in Group L, nine with an angle >40°, and four in aberrant vessels. Also in Group L, the depths of insertion differed significantly between the two methods for ECG guidance (ID-A, ID-B), most likely attributable to the anatomy of the neck and upper thorax. Compared with the straight course of a CVC inserted via the RIJV, a catheter inserted through the LIJV is distorted by two curves of up to 90° (the left internal jugular into the left innominate vein, and the left innominate vein into the superior vena cava). After removing the guide wire, the catheter will float more freely and follow the curves, resulting in a longer distance between the catheter-tip position and the right atrium. This would explain the need to advance fluid filled CVCs further. Additionally, a small, but statistically significant difference was found between ID-B and ID-C in Group L (P<0.001). This finding demonstrates that a considerable percentage of left-sided CVCs placed by ECG guidance abut or impinge on the lateral vessel wall.
The five CVCs advanced into the right atrium Group L, which were found to be beyond the base of the crista terminalis, entered the atrium by only 1 cm. The need to advance some of these catheters into the right atrium may be related to the varying length of the superior vena cava. We agree with the opinion that a catheter withdrawn to a position where no intra-atrial ECG can be recorded, is located outside the heart.6 Given the large number of catheters advanced further than indicated by ECG guidance in this study, one would have expected a far higher incidence of intra-atrial CVCs. This suggests that the intra-atrial ECG is not detecting the right atrium accurately. Our data support the view that the intra-atrial ECG is in fact detecting the pericardial reflection since the pericardium is a fluid filled sac (important for electrical conductance), and there is no other anatomical structure beyond it to explain our findings. Therefore, we believe that catheters placed under ECG guidance are generally located outside of the pericardium, rather than outside the right atrium.
It remains a matter of debate whether positioning a catheter tip in the upper right atrium is appropriate.3 16 But there is agreement that if a patient is exposed to the risk of central venous cannulation, the catheter has to function correctly. In clinical practice, we therefore accept catheter tip positions in the upper right atrium. In vitro and in vivo studies have shown that an acute angle of >40° to the wall of the superior vena cava results in a markedly increased risk of vessel perforation.17 From a clinical point of view, there is no doubt that a CVC tip should not abut a vessel wall. The significance of this problem increases with the stiffness of the catheter and becomes higher when haemodialysis catheters are used.1822
A limitation of our study is the time delay between CVC insertion, TOE assessment and the final position check by postoperative CXR. We cannot exclude catheter migration attributable to surgical manipulations. While portable CXR does not reliably detect whether a CVC enters the right atrium, it is nevertheless helpful in determining catheter tip position.23 Despite our placement procedure of advancing the tip to guarantee adequate flow, chest radiography revealed nine cathetersall left-sidedwith an impingement angle >40° to the superior vena cava (Table 2). Forty-eight of the 57 catheters in Group L (84%) were advanced towards the right atrium in order to achieve free venous back flow through all lumina. Of these 48 catheters, only five were found to be placed at a poor angle (10%). Nine left-sided CVCs were not advanced. Four of these were positioned incorrectly with respect to the angle with the wall of the superior vena cava (44%).
In many hospitals, ECG guidance for CVC placement has replaced a post-insertion CXR to check its position. In Germany (this situation may be different in other countries), from a legal point of view, ECG guidance is equivalent to a CXR.24 Unless the subclavian vein had been punctured or the procedure has proved difficult, post-insertion CXR is considered superfluous if the CVC has been placed with ECG guidance. From our results, this practice is not acceptable with left-sided catheters, when a post-insertion CXR is needed.
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