Optimum depth of central venous catheter - Comparision by pere's, landmark and endocavitory (atrial) ECG technique: A prospective study.

CONTEXT: Blind insertion of central venous catheter has many implications. Better options should be sought to perform this procedure. AIM: To evaluate various options for positioning central venous catheter tip. SETTINGS AND
DESIGN: This is institutional based randomized prospective controlled study.
MATERIALS AND METHODS: In this prospective study depth and position of central venous catheter were evaluated in 150 patients in intensive care unit. Three different methods: Pere's, landmark, and endocavitory (atrial) ECG control were used. STATISTICAL ANALYSIS: Twoway ANOVA test was applied on SPSS version 16 to test the significant difference between the three groups.
RESULTS: Patient characteristic and demographic data were similar in the three groups. The average depth of central venous catheter by Pere's, landmark, and endocavitory (ECG) technique were 14.20 ± 0.69 cm, 12.08 ± 0.98 cm, and 8.18 ± 0.74 cm, respectively.
CONCLUSION: The correct position of central venous catheter by endocavitory (atrial) ECG appears not only to reduce the procedure related complications but also post procedure manipulation of catheter tip detected by post procedure chest X-ray.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Placing central venous catheter (CVC) has become a common practice for anaesthesiologists and intensivists in operation theatres and intensive care units. It is imperative to place the catheter tip at correct position in order to avoid the consequences of malposition.

Malpositions constitute overinsertion with tip position below the level of pericardial reflection (below carina)[1] as abutting and erosion of vessel wall could result in life threatening cardiac tamponade, insertion to an inadequate depth with tip lying in inominate vein, proximal superior vena cava, or in one of the tributaries of subclavian or internal jugular vein. Later predispose to thrombus formation and infection due to mechanical trauma to the subclavian vessel wall.[2] A steep angle of more than 40° between the CVC tip and vessel wall is more likely to erode and perforate.[3]

Carina has long been considered as radiological landmark for positioning CVC tip.[4] Others define the position of tip in relation to the three zones: A, B, and C. Zone A (upper right atrium and lower superior vena cava), zone B (upper SVC and junction of right and left inominate veins), zone C (left inominate vein).[567] Radiologically, these zones are not distinctly delineated. It is therefore desirable to rest the tip between carina and within 34 cms above this radiological marker to avoid pericardial reflection.

The purpose of the present study was to determine the correct position and depth of CVC by three different techniques in adult patients in intensive care unit.

MATERIALS AND METHODS

After obtaining approval from hospital ethics committee and written informed consent, 150 patients aged between 20 to 50 years admitted in intensive care unit were enrolled in this prospective study. More than one attempt at vein puncture, first attempt arterial puncture, arrhythmias, pacemaker driven rhythm, local infection, and abnormal coagulation profile were excluded from this study.

In all enrolled patients, CVC was inserted aseptically adapting infraclavicular route for puncturing right subclavian vein at 1 cm medial and inferior to clavicle at medial one-third and lateral two-third point in supine position. All patients were randomly placed into three groups.

Group P: In this group, depth was determined by applying Pere's formula (height in cms/10-2).

Group L: In this group, depth was determined by measuring distance with sterile tape between puncture site to clavicular notch and from clavicular notch to manubrio-sternal angle.

Group E: In this group, depth was determined by observing the change in configuration of ‘P’ wave of endocavitory (atrial) ECG recorded on standard monitor by placing an indigenously designed adaptor placed between the monitor and the CVC. This adaptor was made by fixing two electrodes atop of metal strips which were seated on the base of box [Figure 1]. These metal strips had central movable flange portion to increase the firm attachment to the underlying contact points. To facilitate recognition and avoid incorrect attachments, the electrodes were marked “RM” and “AG.”

Figure 1

Depicting improvised adaptor with established connection between the monitor and guidewire mounted central venous catheter

AG- Alligator clip/guide wire

RM- Right arm lead//monitor

Circuit was planted at the underside of the base through an on-off switch visible at the top right. After aseptic preparation and draping the site, right SCV was cannulated with 18 G needle and 20 cm long catheter was railroaded over the guidewire such that “J” tip just protrude out of distal end of the catheter. Standard ECG monitor was used whose right arm lead (clamp/knob/banana plug) was attached to “RM” electrode. The other electrode marked “AG” receives alligator clip from a sterilized cable whose other end had a pin which is inserted by an assistant into the socket of the ethylene oxide sterilized disposable ECG lead. The clamp of ECG lead is in turn fixed to the guidewire as depicted in Figure 1. Left arm and left foot lead are attached as usual. Surface ECG (Lead II) is displayed on the monitor. Turning on the switch on top of the adapter shift to endocavitory (atrial) ECG trace. In order to maintain sterility of the drap, it was ensured that the assembly was placed away from draped area.

The observed change in the configuration of “P” wave of ECG as the catheter mounted guide wire was advanced are depicted [Figures 2a–c]. As sino-atrial (SA) node is approached height of “P” wave accentuate progressively and attain a maximum amplitude. On further advancement into the atria, “P” wave becomes bifid with negative deflection followed by positive. The catheter was then withdrawn until the “P” wave regains original configuration and was threaded at skin on further 2-3 cm retrieve.

Figure 2

(a) Normal endocavitory (atrial) ECG. (b) ‘P’ wave increase in amplitude progressively to reach maximum (denoting location of SA node). (c) normal configuration is reverted on catheter retrieve

Post insertion portable chest X-ray was taken in supine posture to assess catheter tip position and complications. The depth at skin to which the CVC was inserted was observed in the three groups.

The result was expressed as mean ± SD. For statistical analysis two-way ANOVA test was applied on SPSS version 16 to test the significant difference between the three groups. P < 0.05 was considered significant difference between the groups.

RESULTS

This study randomly evaluated depth and position of CVC by three different techniques in 150 patients admitted in intensive care units. The three groups were demographically similar with no statistically significant difference with regard to age, height, and insertion time [Table 1].

Table 1

Demographic data (values in mean+SD)

The insertion depth of CVC threaded at skin surface by three different techniques was observed [Table 2].

Table 2

Intracarporeal insertion depth of central venous catheter (in cms) at skin (mean+SD)

Post insertion chest X-ray depicted the position of CVC tip in relation to level of radiologically visible landmark carina by three techniques. Also malpositions and angle the CVC made to the vertical were determined [Table 3].

Table 3

Position of central venous catheter on post insertion chest X-ray

DISCUSSION

This study demonstrated appreciable reduction in the length of CVC inserted into SVC with application of ECG guided placement in comparison to Pere's and anatomical landmark techniques. For positioning the CVC tip, numerous studies have been published based upon the height of patient[89] and landmark based insertion.[10] The correct position of CVC tip can be verified on post insertion chest X-ray [Figure 3]. There is a potential life threatening risk of cardiac tamponade with CVC whose tip lie below the upper level of pericardial sac when it abuts and erodes the vessel wall. Vessel wall can possibly be perforated while carrying out the procedure with dilator or guidewire.[11] Czepizak and OCallaghan recommended fixation of catheter, use of soft tip catheters, and preference for right sided insertion.[12] The lower part of superior vena cava is surrounded by the pericardial sac. In cadavers, it has been observed that the upper limit of the pericardial sac is 0.8 cm below the carina.[13] On chest X-ray the distinct upper boundary of the pericardial sac is not visible. Carina has thus been considered as reliable radiological landmark for positioning the CVC tip. The CVC tip can safely be positioned within the superior vena cava between carina and 4 cm above. CVC tip positioned outside the superior vena cava are prone to venous thrombus formation and infection.[14]

Figure 3

Postinsertion chest X-ray displaying normal position of CVC tip (arrow) in relation to carina

There can be enormous disparity between the surface landmarks and the actual position of the subclavian and superior vena cava which can give erroneous calculations during CVC insertion procedure. This study clearly demonstrated that 96% of CVC inserted by endocavitory (atrial) ECG control were correctly placed as confirmed by post insertion chest X-ray. No CVC was overinserted below the level of carina avoiding the possibility of tamponade in this group. By landmark technique, only 52% of CVC were positioned correctly and 30% were overinserted.

The possibility of vessel wall perforation consequently leading to either hydrothorax or cardiac tamponade can be attributed to the angle between catheter tip and superior vena cava wall. Because of acute joining of left subclavian vein to superior vena cava there is increased likelihood of steep angle of >40o that the CVC tip make to the wall of superior vena cava (wall is assumed as vertical line parallel to the line joining the tip of spinous process of vertebra) when placed from left subclavian vein.

McGee and Moriarty observed intracardiac position with 20 cm and 16 cm CVC in 56 and 11% of subjects respectively, in their study.[15] Russel recommended 13 cm CVC length to avoid cardiac placement.[16] The present study with ECG guided CVC tip positioning corresponds to attempts in a study by Lee et al. which showed that the catheter tips could successfully be placed near carina.[17]

During SCV, catheterization malpositions of CVC has been observed by some authors to vary from 1.8%[18] to as high as 9.3%.[19] Delay in detecting malpositioned catheter by post insertion chest X-ray can be avoided when applying endocavitory (atrial) ECG technique. Strict sterility of the draped area during endocavitory ECG procedure was maintained by keeping the length of the cable bearing alligator clip and the pin adequate enough (length 150 -cm) to avoid intrusion into sterile area and by wrapping the leads in a sterile sheath. The connection between the cable and the ECG lead was established by the assistant. In obesity and burn in the neck region where anatomy is distorted, landmark technique can misguide catheter tip placement. In these situations, endocavitory ECG could achieve optimal depth for CVC tip.

The use of adapter for endocavitory guided ECG technique allow smooth uninterrupted CVC insertion and ensured greater patient safety.[2021] This study achieved significantly higher percentage of correct position of CVC tip with endocavitory ECG guided CVC insertion in comparison to other methods adapted. Excellent quality and lucid exhibition of ECG on monitor is crucial to situate CVC tip at acceptable position in SVC which were repetitively attainable without any hassle. Limiting insertion depth in ECG guided CVC insertion group have possibly decreased the malpositions in comparison to other techniques employed and required less relocation drills.

Only limitation of ECG guided technique is that arterial puncture and cannulation cannot be ignored as this technique fails to recognize the difference between the two vessels. Other criteria like pulsating blood column should be considered to correctly identify the vessel.

Based on data obtained in our study we conclude with the opinion that endocavitory (atrial) ECG technique for central venous catherization not only limits the intracorporeal length of the catheter but also is more accurate in securing correct position within the superior vena cava. It does not increase the financial burden and can get wider scope in the protocol of CVC insertion in intensive care unit.