Radiographic Assessment of Jugular Bulb Catheters L. Anne Hayman, M.D.,* Linda M. Fahr, M.D.,* Katherine H. Taber, Ph.D.,* Carol L. Hughes, R.N., ~ Ann M. Ritter, M.D., ~ and Claudia Robertson, M.D. ~ Departments of *Radiology and ~Neurosurgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas
The objective of this paper is to review the technical pitfalls associated with the bedside placement of oxygen saturation (02 ) catheters into the jugular bulb (JB). A retrospective review was used to gather data on optimum radiographic technique and JB 0 2 catheter position on 27 patients. Eleven percent (3/27) of the JB 0 2 catheters required immediate repositioning to prevent serious complications (that is, reliance upon incorrect 0 2 measurements or venous thrombosis). Radiographic assessment of these catheters is best performed using a portable overpenetrated Stenvers view and a companion overpenetrated lateral radiograph. Computed tomographic scans of the neck or skull base also detected malpositioning of the catheter. This series indicates that conventional bedside radiography requires meticulous attention to assure adequate visualization of the catheter. Knowledge of the venous anatomy of the neck and familiarity with JB 0 2 catheter design will improve the radiologist's ability to correctly interpret images which include this device.
he use of fiberoptic jugular bulb (JB) catheters is beconfing an increasingly colnnaon way to measure oxygen (02) saturation. They are introduced via a puncture in the anterior inferior neck into the jugular venous system (1, 2). A schematic of the catheter design is shown in Figure 1. Two comnlerciaUy available fiberoptic catheters are commonly used in adult patients. Both catheters are 4 French and 25 cm in length. They are advanced 12-15 cm until the tip is in the jugular bulb. In children, 3 French catheters 5-15 cm in length have been used (3). Ideally, all JB catheters are advanced into the jugular bulb. Since these catheters are placed without the benefit of fluoroscopic guidance, their position must be ascertained by portable radiographs. Once they are in place, they remain in the jugular bulb for approximately 5 days. During this time, they appear on the intensive care chest radiographs (Fig. 2) and computed tomographic (CT) scans of the neck or head. Unfortunately, most radiologists are not familiar with these devices, and, to our knowledge, the pitfalls in catheter assessment have received little attention in the radiologic literature. Only a single radiographic study has addressed the problem of assuring that the catheter is advanced into the jugular bulb (4). The purpose of this report is to acquaint the reader with these devices by describing our experience with 27 patients who were monitored by fiberoptic JB 0 2 catheters.
MATERIALS A N D M E T H O D S
Twenty-seven patients with JB 0 2 catheters were studied. Thirty-three radiographs were obtained using an AMX4 portable x-ray unit (General Electric, Milwaukee, WI). An 8:1 or 10:1 parallel grid, with the grid lines parallel to the long axis of the catheter, was used to nfininfize loss of radiation due to grid cntoff. Companion overpenetrated lateral and Stenvers radiographs were obtained. The latter required rotating the head 15-20 ° away from the side of the JB 0 2 catheter (usually placed in the larger right jugular vein). In addition to the portable radiographs, eight patients also had a CT scan that included tile JB 0 2 catheter. These scans were performed on a 9800 Signa Unit (General Electric, Mihvaukee, WI), and bone window settings were available for review. All images were reviewed retrospectively to determine the radiographic quality and position of the JB 0 2 catheter. Independent assessments were made by physicians fanfiliar with these catheters and the venous anatomy of the neck. Radiography of Jugular Bulb Catheters • 331
T r a n s m i t t i n g and receiving optical fibers
Figure 1. Schematic of the fiberoptic JB 0 2 catheter system. Note that the catheter has a double lumen; one side contains the radiodense optical fibers, and the other provides a route for retrieval of a blood sample to calibrate the O 2 saturation of the catheter. The monitor also receives information from a pulse oximeter (SaO2), which is attached to the patient's extremity.
These assessments were compared with the reports generated by radiologists unfamiliar with this technology.
RESULTS Overpenetrated lateral and companion Stenvers views were best at identifying the catheter tip in the superior jugular bulb (Fig. 3). There were no clinical complications 332 * Radiography of Jugular Bulb Catheters
associated with turning the head to obtain the Stenvers view. In most patients (24/27), the catheter was correctly positioned in the internal jugular venous system. In 11% (3/27), the catheter needed to be immediately repositioned. In one case, it had been threaded into the plexus of posterior veins that drain the neck muscles (Fig. 4). In another patient, the distal portion was looped within the internal jugular vein (Fig. 5). In a third patient, the catheter Emergency Radiology • November/December 1995
Figure 2. Portable chest radiograph of a patient with a right-sided jugular bulb catheter. Arrowheads mark the external tubing. An arrow marks
the proximal portion of the introducer. Nasogastricendotracheal and subclavian lines are also present.
Figure 3. Correct placement of a Baxter fiberoptic catheter. Conventional overpenetrated radiographs in lateral (A) and Stenvers(B) projections of right jugular bulb show the catheter (arrows). The right external auditory canal (EC)is marked for orientation.
tip was identified on a C T scan as it entered the vertebral v e n o u s plexus ( c o m p a r e Figs. 6 and 7). N o n e o f the catheters entered tile siguloid sinus. N o case required the use o f intravenous contrast to determine catheter position. N o carotid artery punctures were repcrted. O n the conventional radiographs, radiologists unfanfiliar with this teclmology either failed to mention the JB 0 2 catheter or suggested that it was a malpositioned subclavian line. In one case, a radiolucent JB 0 2 connector was mistaken as transection o f the catheter. O n C T scans o f the neck and skull base, calcification o f the stylohyoid ligament Emergency Radiology• November/December1995
a n d / o r the jugular spine initially confused the authors, but tracing the density superiorly to the jugular bulb or inferiorly below the level o f ligament calcifcation quickly solved this problem (Figs. 5 and 6). N o n e o f the C T reports mentioned the presence o f the catheter except one, which was interpreted by an author o f this study (L. A. H.).
DISCUSSION T h e fiberoptic JB 0 2 catheter is an increasingly popular device that is visible on radiographs o f the chest, neck, and Radiography of Jugular Bulb Catheters • 333
Figure 4. Incorrectly placed Baxter fiberoptic catheter. Conventional overpenetrated radiograph in lateral projection shows the catheter (arrow) in the plexus of veins which drain the posterior muscles of the neck (see Fig. 9 for normal venous anatomy in the lateral projection).
Figure 5. Coil in the midportion of an Abbott fiberoptic catheter. Conventional overpenetrated radiograph in Stenvers projection shows that the catheter tip is correctly placed in the jugular bulb. Coiling occurs when this catheter is advanced afterthe tip is lodged in the jugular bulb. The introducer for this type of catheter is routinely left inside the jugular vein. The terminal end of the introducer is marked by an arrowhead in this radiograph.
Figure 6. CT of a correctly placed catheter. Axial CT scans of the neck (A) and skull base (B) filmed in bone w i n d o w settings show a right-sided JB 0 2
catheter (arrows), which is correctly positioned in the superior jugular bulb. Calcified stylohyoid ligaments (arrowheads) in (A) should not be confused with the catheter. 334 • Radiography o f Jugular Bulb Catheters
Emergency Radiology • November/December 1995
Figure 7. CT of an incorrectly placed catheter. Axial CT scans of the C1 level (A) and approachingC2 (B) vertebrae filmedin bone window settings show a left-sidedIB O2 catheter (arrows). The tip of the catheter is incorrectlyplaced in the leftvertebral plexus at the level of the atlas. (See Fig.8 for normal axial venous anatomy.)Calcifiedstylohyoidligamentsare marked by arrowheads for orientation.
skull base. Two fiberoptic catheters are currently approved in the United States. The most widely used is the Abbott Critical Care 4 French umbilical artery catheter. 1kecently, Baxter Healthcare Corporation, Edward Critical Care has released a 4 French regional ox'ygen saturation catheter. These catheters are placed in the superior jugular bulb to measure the 0 2 saturation in the blood and thereby estimate cerebral blood flow (CBF). The advantage o f this technology is that it provides continuous monitoring, which allows tile detection o f a decrease in CBF before it results in brain damage. It has proven useful in patients with severe head injury and for intraoperative monitoring o f neurosurgical or cardiovascular patients (1, 2, 5-7). Nearly 40% of head injured patients have episodes of an abnormally low jugular venous 0 2 (<50%). This is significant because one or nrore of these episodes is strongly associated with a poor neurologic outcome, suggesting that early identification by a fiberoptic catheter could initiate early therapy for ischemic episodes and improve outcome after head injury (8). Allother possible application ofJB 0 2 technology is in patients undergoing cardiopuhnonary bypass. Twenty-three percent o f these patients developed an abnormally low JB 0 2 (<50%) when they were rewarnled from 27°C. Although the CBF was sig~fificantly lower in these patients, neurologic consequences were not docmnented (5). Since these catheters are introduced without tim benefit o f fluoroscopic guidance, their position nmst be d o c u mented by conventional x-rays o f the neck and skull. A EmergencyRadiology• November/December1993
complicated set o f measurenmnts has recently been advocated to determine the position o f the catheter tip (4). These measuren:ents were not necessary to evaluate tile films obtained in this study because the jugular bulb was well visualized. This is an important consideration because 0 2 naeasurements from a malpositioned catheter will be contamitmted by blood from outside the brain, resulting in an erroneous calculation of cerebral blood flow that may cause a misdirected therapy. Inappropriate placement o f the catheters has been reported in 3% o f 123 patients. However, tile details concerning the catheter locations in these cases were not described (3). Another study noted that the JB 0 2 catheter required repositioning in 19% (6/32 cases) (4). This study seemed to imply that the internal jugular vein catheter needed only to be advanced into the ju~flar bulb. Problems with positioning outside the internal jugular vein were not mentioued. The present study, however, clearly indicates that this complication can occur. For this reason, the imaging clinician must understand tile complex venous anatomy of tile neck. It is sunnnarized in Figures 8-11 (6). T h e caliber o f these valveless veins varies with the position of the body and head, as well as physiologic changes ill intrathoracic pressure. W h e n the patient is s,piHe, the internal jugular vein is the major route o f cerebral venous drainage (9). It anastaumses with the vertebral plexus at the foramen magnum and at irregular intervals tlaroughout the neck. These veins connect with the Radiography of Jugular Bulb Catheters • 335
Figure 8. Schematic of cervical vertebral venous anatomy in axial project/on. [Modified from Ref. 9.]
VeOe r Vertebral
Radicularv e i n ~
Venous Plexus of the Lateral Foramen
Anterior Condyloid veins
Inferior Petrosal Sinus Sigmoid Sinus - - - - ~ .
Medial and Lateral Eoidural veins
Superior Jugular Bulb
Vertebral Plexus "surrounding the Vertebral artery
Internal Jugular Vein
Inferior Jugular Bulb
~ / ~ a v i a n v e i n
Superior Vena Cava
Figure 9. Schematic of cervical venous anatomy in coronal projection. Note the numerous unnamed interconnections between the internal jugular vein
and the vertebral venous plexus that surround the vertebral artery. (Although the jugular veins are of equal caliber in this drawing, the vein and jugular bulb on the right side are usually larger than on the left side.) [Modified from Ref. 9.] 336 • Radiography o f Jugular Bulb Catheters
Emergency Radiology • November/December 1995
Figure 10. Normal cervical venous anatomy on a lateral projection of a patient with an arteriovenous fistula. Digital subtraction vertebral angiogram (A) shows a fistulous connection between the vertebral artery (arrow) and the surrounding vertebral plexus (arrowheads) of veins. A deep muscular vein is also visualized (double arrows). The bullet fragment (BF) responsible for this injury is clearly seen on the nonsubtracted film (B).
Figure 11. Coronal CT in bone window setting shows the relationship between the first and second cervical vertebrae (C1, C2) and the jugular bulb. The lip of the clivus and the internal and external auditory canals are also labeled for orientation. Emergency Radiology • November/December 1995
Radiography of Jugular Bulb Catheters • 337
medial and lateral epidural venous plexus. In the ,pright p o sition, the intraluminal pressure in the internal jugular system becomes negative, and it collapses, shifting the venous drainage o f the brain to the vertebral plexus. A similar shift in venous drainage occurs w h e n high intrathoracic pressure interferes with flow in the internal jugular vein. S o m e authors believe that these changes in the jugular vein caliber can alter the 0 2 readings and, for that reason, advocate catheter placement in the jugular bulb itself (4).
SUMMARY Eleven percent (3/27) o f the catheters in this series required i m m e d i a t e repositioning. Medical therapies based upon C B F calculated from JB 0 2 catheter measurements may be seriously misdirected if the catheter is not correctly positioned to measure cerebral venous outfloxx; rather than venous blood from the extracerebral tissues. Portable radiographs must be correctly centered and overpenetrated to show the tip o f the catheter in the jugular bulb. C o m p a n ion lateral and Stenvers projections are reconamended. This practical guide to the radiographic appearance and location o f J B 0 2 catheters is designed to improve assessment o f these devices by radiologists w h o may be unfamiliar with this increasingly popular technology.
ACKNOWLEDGMENTS The authors wish to thank Patricia Stevenson, IL.T., and the technicians at Ben Taub General Hospital, Houston, TX, for the consistently superb images which made this project possible.
338 • Radiography of Jugular Bulb Catheters
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