Intra- and Extra-Pericardial Lengths of the Superior Vena Cava in Vivo: Implication for the Positioning of Central Venous Catheters
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Anaesth Intensive Care 2005; 33: 384-387 Intra- and Extra-pericardial Lengths of the Superior Vena Cava in Vivo: Implication for the Positioning of Central Venous Catheters T. D. KWON*, K. H. KIM†, H. G. RYU*, C. W. JUNG§, J. M. GOO**, J. H. BAHK†† Departments of Anesthesiology, Cardiothoracic Surgery and Radiology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea SUMMARY To reduce the possibility of cardiac tamponade, a rare but lethal complication of central venous catheters, the tip of the central venous catheter should be located above the cephalic limit of the pericardial reflection, not only above the superior vena cava-right atrium junction. This study was performed to measure the superior vena cava lengths above and below the pericardial reflection in cardiac surgical patients. Cardiac surgical patients (n=61; 27 male), whose age [mean±SD (range)] was 47±15 (15-75) years, were studied. The intrapericardial and extrapericardial lengths, and the length of the medial duplicated part were measured separately. The whole vertical lengths of the superior vena cava on either side were calculated respectively by adding the intra-and extrapericardial and medial duplication lengths. The lateral extrapericardial was 29.1±6.5 (Mean±SD) (9-49) mm (range), and lateral extrapericardial length was 32.6±6.9 (20-53) mm. The medial extrapericardial length was 23.3±5.0 (11-39) mm, medical duplicated length was 7.2±3.3 (4-20) mm, and medial intrapericardial was 28.3±7.0 (20-52) mm. The averaged superior vena cava length of both sides was 60.3±9.0 (44.5-90) mm. Almost half of the superior vena cava was found to be within the pericardium and half out. This information may be helpful in deciding how far a central venous catheter should be withdrawn beyond the superior vena cava-right atrial junction during right atrial electrocardiographic guided insertion, and in the prediction of optimal central venous catheter insertion depth. Key Words: VEINS: superior vena cava, length. COMPLICATIONS: central venous catheterization, cardiac tamponade The United States Food and Drug Administration should be located above the cephalic limit of the peri- guidelines state that central venous catheter (CVC) cardial reflection2-4, not merely above the superior tips should not be placed in, or allowed to migrate vena cava (SVC)-right atrial (RA) junction. Without into the heart1. However, to avoid the rare but lethal information about the SVC length, it may not be pos- complication of cardiac tamponade, the CVC tip sible to determine how far the CVC should be with- drawn after it is located at the level of the SVC-RA junction (e.g. during a right atrial electrocardio- graphic guided insertion technique), or to identify a potentially dangerous positioning of a CVC tip on the *M.D., Fellow, Department of Anesthesiology, Seoul National University chest X-ray. Hospital, Seoul National University College of Medicine, Seoul, Korea. The SVC length below the cephalic limit of the †M.D., Assistant Professor, Department of Cardiothoracic Surgery, Seoul National University Hospital, Seoul National University College of pericardial reflection has previously been assumed Medicine, Seoul, Korea. to be 20 mm5, or reported to be about 3.0 cm in a §M.D., Clinical Assistant Professor, Department of Anesthesiology, Seoul 6 National University Hospital, Seoul National University College of study of 34 cadavers of very old people . However, Medicine, Seoul, Korea. cadaveric studies measuring anatomic structures may **M.D., Assistant Professor, Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, be limited by the post mortem factors causing distor- Seoul, Korea. tion of anatomical structures and the emptied vessels. ††M.D., Associate Professor, Department of Anesthesiology, Seoul National University Hospital, Seoul National University College of Thus, measurements of the SVC lengths below and Medicine, Seoul, Korea. above the cephalic limit of pericardial reflection in Address for reprints: Dr Jae-Hyon Bahk, Department of Anesthesiology, live, blood-filled vessels were warranted. Seoul National University Hospital, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul, Korea 110-744. The purpose of this study was to measure the intra- Accepted for publication on February 28, 2005. pericardial (IP) and extrapericardial (EP) lengths on Anaesthesia and Intensive Care, Vol. 33, No. 3, June 2005 LENGTH OF THE SUPERIOR VENA CAVA 385 the blood-filled SVC during cardiac surgery, and to seek for any anatomical landmarks for the prediction of the cephalic limit of pericardial reflection or SVC lengths on the chest X-ray. METHODS After receiving Hospital Review Board approval and obtaining informed consent, 61 elective cardiac surgical patients (27 males and 34 females) were enrolled in the study. Twenty-six of the patients underwent aortic valve replacement; six mitral valve replacement; 22, coronary artery bypass surgery, and four, off-pump coronary artery bypass surgery. Patients who required a re-operation were not in- cluded. After routine sternotomy, a self-retaining retractor was placed. The pericardial sac was opened. The IP part of SVC was exposed as usual. The EP part of SVC was exposed after removing the loose connective tissue medially and laterally. The cephalic limit of pericardial reflection on the medial side was taken as the angular transitional junction between the left brachiocephalic vein and the SVC. The cephalic limit of pericardial reflection on the lateral side was regarded to be at the same level as the medial. The vertical lengths on each side of SVC were measured as follows: black suture silk of about 10 cm long was pinched with two forceps. The between-forceps length was adjusted to be exactly the same as the part of SVC length that we were trying to FIGURE 1: Schematic diagram showing the extrapericardial length measure, while keeping the silk tight. Afterwards, we (EP), the intrapericardial length (IP), and the length of the medial measured the distance between the two forceps with duplicated part (MD) of the superior vena cava (SVC). RA=right a pre-sterilized ruler. The IP and EP lengths on both atrium, BC=brachiocephalic vein. sides, and the length of the medial duplicated part (MD) were measured separately (Figure 1). The whole vertical lengths of the SVC on either side were late the notch-carina and notch-angle lengths for 7 calculated by simply adding the IP and EP lengths, each patient : actual distance=projected distance on and the MD length in the case of the medial SVC the plain film x [distance between X-ray tube and length. The distances were measured by two cardiac object is equal to distance between X-ray tube and surgeons, and with less than 3% inter-observer differ- film]. Distance between X-ray tube and object=the ence. The arithmetic mean of the individual measure- distance between X-ray tube and film (72 inch x ments was used for data analyses. 25.40 mm=1828.8 mm) minus the distance between To find potential anatomical landmarks for the the carina and the anterior chest wall, which was cephalic limit of pericardial reflection or SVC lengths measured on the lateral chest X-ray. To improve that are easily identifiable at bedside or on chest accuracy and reliability, three measurements of the X-ray, the jugular notch of the clavicle to tracheal distances were performed with electronic calipers to carina (notch-carina length) and the jugular notch the nearest 0.1 mm. The arithmetic mean was calcu- to tracheobronchial angle distances (notch-angle lated by using the measurements within 5% variances length) were measured vertically on the preoperative and used for the study. routine posterior-anterior (PA) chest X-ray. The The relationships of the height, weight, body mass distances were measured with electronic calipers on index or age with the SVC length or IP, MD and EP the 12-times enlarged images of the digital PACS lengths were analyzed by the Pearson’s partial corre- (Picture Archiving Communication System) as fol- lation analysis. On the assumption that any disease lows. Because intrathoracic structures appear mag- with the proximal aortic enlargement might lengthen nified on PA views, a correction was made to calcu- the SVC length, SVC lengths depending on the pre- Anaesthesia and Intensive Care, Vol. 33, No. 3, June 2005 386 T. D. KWON, K. W. KIM ET AL sence or absence of aortic valvular disease were com- pulmonary diseases increases with age, the SVC pared with unpaired t-test. Pearson’s correlation length may be lengthened in the extremely aged analysis was used to assess the relationship between population of the cadaver study6. the notch-carina and notch-angle lengths and the IP, The cephalic limit of pericardial reflection was MD, EP and whole SVC lengths. Values are pre- known to surround the SVC as far as insertion of the sented as mean±SD (range). P values <0.01 were azygos vein5,9, or lie at the same level as the angle considered significant. made by the right main bronchus and the trachea5,10. The tracheal carina was found to be always located RESULTS above the cephalic limit of pericardial reflection on Patients’ age was 47±15 (15-75) years, height cadaver dissection6. The internal jugular vein or the 161.8±8.6 (140.0-186.0) cm, and weight 60.8±9.5 innominate vein is located just behind the jugular (46.0-83.0) kg. Neither the SVC length nor any por- notch of the clavicle11,12, which is easily palpable 0.25 tion of the SVC correlated with the weight, body mass to 1 cm lateral to the sternal end11. Therefore, this index or age of the patients. The only exception was jugular notch may be used as a surface landmark for the height, which had some correlation with medial central venous access.