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* From the Division of Cardiology, Elmhurst Hospital Center, Elmhurst, NY.
Correspondence to: John E. Madias, MD, Professor of Medicine (Cardiology), Division of Cardiology, Elmhurst Hospital Center, 79-01 Broadway, Elmhurst, NY 11373; e-mail: madiasj{at}nychhc.org
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Key Words: acute renal failure • central venous catheters • electrocardiography • end-stage renal failure • hemodialysis • hemodialysis catheters • intracardiac ECG • P waves • venovenous hemofiltration
Hemodialysis (HD) of patients who are hospitalized in critical care units is commonplace, and it is carried out either as a continuation of the routine HD that patients with end-stage renal failure undergo while ambulatory, as a new procedure for patients who are destined to receive maintenance therapy with HD due to the worsening of their known renal dysfunction, or as a supportive procedure in patients with new acute renal failure who are expected eventually to recover. Many of these procedures are administered via a double-lumen Shiley central venous catheter (SCVC) for venovenous hemofiltration, which is inserted into the superior vena cava (SVC) or high right atrium (RA) employing cannulation of the internal jugular, or subclavian veins, or peripherally into the basilic or femoral veins. This type of HD is useful not only for patients with acute renal failure who will receive short-term therapy with HD, but also for others relying on long-term therapy with HD whose arteriovenous shunts have failed due to thrombosis, who are awaiting maturation of a shunt, or who have not had a shunt placed yet.
The scenario of insertion of the SCVC is appropriately associated with considerable concern in the surgeon or other physicians on the case regarding the proper positioning of the catheter in the central circulation, and the occurrence of complications of arrhythmias, pneumothorax, hematomas, central vessel or chamber perforation, hemothorax, hemopericardium, or cardiac tamponade.1 Even when the SCVC finds its way into the central circulation, concern remains about whether the catheter tip has extended deeply into the RA or even into the right ventricle, thus setting the stage for possible supraventricular or ventricular arrhythmias. It has become customary to obtain a portable anteroposterior chest radiograph immediately after such procedures to ensure the proper positioning of the catheter and absence of the feared complications. Parenthetically, an anteroposterior chest radiograph provides a false sense of absolute security, since for the purpose of being sure of the position of the tip and the course of an inserted central venous catheter (CVC), a complementary lateral chest radiograph is needed, but it is rarely obtained in critical care units. Asking for a "chest film" is an ingrained, "reflex-like" action taken by almost all physicians in critical care areas.
However, one wonders whether the rethinking of such a practice is in order, considering the ease of monitoring the intracardiac (IC) ECG (ie, SVC/RA) as a guide for the proper positioning of an SCVC that is inserted via the brachiocephalic veins, and the certainty that it provides about a safe positioning of the tip of the catheter after its insertion whenever concern arises. These IC ECGs can be obtained via special electrodes or guidewires,2 but such an approach limits their employment to only the insertion time window and renders the procedure more invasive, increasing the chance for complications Thus, a more versatile and safe method is to use the saline solution-filled SCVC, which is inserted preferably via the internal jugular vein, as an ECG electrode, both for the correct positioning of the catheter and for the evaluation of its proper position after its insertion, in lieu of a chest radiograph. This IC ECG-based approach for inserting CVCs has been used widely in positioning ventriculoatrial shunts, for the detection and treatment of air embolism during neurosurgical procedures, for parenteral nutrition, and for the diagnosis of complex cardiac arrhythmias.3 4 5 6 7 8 Moreover, the IC ECG-guided placement of a CVC using saline solution as the conductive medium has been employed even for catheters that are inserted peripherally via arm veins,9 which occasionally could trigger ventricular tachycardia traced to change in the arm’s position.10 All of the workers cited have concluded that employing the ECG-guided approach to the placement of CVCs eliminates the need for obtaining a postprocedure chest radiograph.
The recording of IC ECGs should be performed using well-grounded ECG equipment that has been certified and monitored by the bioengineering department of an institution, which is also requisite for recording routine standard ECGs, since serious arrhythmias could occur with poorly grounded ECG recorders.11 Also the IC ECG can be recorded using battery-operated ECG machines or by using the "battery" mode of an electrically unplugged conventional ECG machine. For the purposes of documentation of the appropriateness of the positioning of the SCVC, the operator should include in the procedure note a recording of an IC ECG obtained from the distal lumen after the catheter has been securely anchored as part of the patient’s record. This serves as evidence that the tip of the catheter is in the intravascular environment and is at a level that excludes an arrhythmogenic trigger. Also, obtaining a few IC ECG recordings at different stages of the catheter advancement denotes that the tip was always in the SVC/RA compartment and, thus, that complications like pneumothorax, perforation, hemothorax, or hemopericardium are unlikely.
The method for obtaining an IC ECG via an SCVC is simple. A plastic adapter with a rubber head is used to plug the hub of the catheter. The needle of a saline solution-filled syringe is inserted via the rubber head, and, after initial aspiration to ensure that the catheter is free of clots or air bubbles, the saline solution is infused. The needle of the syringe then is connected to the V1 cable of the ECG machine, using an alligator clamp. The 12-lead ECG thus obtained is identical to the tracings routinely recorded, save for the IC ECG substituting for the V1 precordial lead. When the tip of the SCVC is in the SVC or is at its junction with the RA, the recorded P wave reveals an entirely negative complex, which becomes larger as the catheter is inserted deeper into the SVC. When the totally negative P wave is replaced by a positive/negative deflection, the tip has reached the high atrium/mid-atrium, and a totally positive P wave suggests that the tip is at the low atrium and is about to cross the tricuspid valve. As the SCVC tip approaches the low RA, the amplitude of the corresponding QRS complex increases. An IC ECG during the insertion of a SCVC should be recorded via the distal (tip) lumen, which also provides a larger P wave than the one obtained from the proximal lumen, the opening of which is situated 3.5 cm from the tip. IC ECGs also can be obtained by using aspirated blood as the conductive medium or by infusing 4% saline solution or solutions of other electrolytes, like NaHCO39 which supposedly provide more reliable recordings; however, convenience calls for the filling of the catheter with normal saline solution (0.9%), which in the hands of this author has been adequate.
In 2000, while we were employing IC ECGs in studies involving patients with anasarca peripheral edema,12 13 we encountered three patients who required HD during their hospitalization in our coronary care unit. Patient 1, a 66-year-old man with diabetes, coronary artery and peripheral vascular disease, hypertension, and chronic renal failure, required HD. An SCVC was inserted via the right internal jugular vein. Immediately after the procedure, we obtained an IC ECG from the SCVC, and we concluded that the tip of the catheter was above the SVC/RA junction (Fig 1 ). Nevertheless, the surgeon who performed the procedure recommended a chest radiograph, which was obtained (Fig 1) and confirmed our impressions.
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It is prudent for the clinician to keep in mind that occasionally a chest radiograph needs to be obtained when patients develop symptoms during a procedure, or when the procedure was laborious, took many punctures, or was associated with IC ECGs of questionable quality. The question of how quickly the procedure can be performed has been thoroughly researched,3 4 5 6 7 8 9 15 16 and the consensus is that this procedure can be completed rapidly, without any additional equipment, practically eliminating the need for a confirmatory chest radiograph with a related time delay of approximately 1 h and thus preparing the patient for immediate HD, which occasionally has to be implemented expeditiously. In terms of subsequent monitoring, repeating the IC ECG is rarely required. SCVCs are securely anchored in their position, and only peripherally inserted catheters are associated with migration deeper into the RA or right ventricle.10 17 Nevertheless, on the rare occasion when this happens due to deficient stabilization of the catheter (eg, due to disruption of the skin sutures), an IC ECG can be obtained, can be checked to confirm that the morphology of the P wave has changed from a negative deflection to a positive/negative or completely positive one, the SCVP can be withdrawn a few centimeters, and the IC ECG can be repeated, with the presence of only a negative P-wave deflection in the final tracing needed to confirm repositioning. Even in such an instance, a chest radiograph is unnecessary.
The issues discussed above need to be considered the next time a physician is about to recommend a chest radiograph after a SCVC has been placed in an HD-bound patient. Instead, an IC ECG can be obtained quickly to provide the physician with the needed reassurance. Furthermore, this method should be recommended to all physicians placing SCVCs and should be used during the actual cannulation and positioning of such catheters. Vast experience, particularly in Europe, with cases numbering in the thousands among anesthesiologists and nephrologists2 3 4 5 6 7 8 14 15 16 attests to the safety of this procedure. The method has logical underpinnings, has been adequately researched, and now awaits wide application in this country.
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Received for publication May 5, 2003. Accepted for publication May 6, 2003.
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