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Home , Septic shock

Challenges Associated With Central Venous Placement and Central Venous Oxygen Saturation

Matthew Wemple MD and Andrew M Luks MD

Introduction mellitus, and hypertension presented to the emergency de- partment with shortness of breath and . Soon Patients with septic and often after arrival he became drowsy and was placed on nonin- require hemodynamic monitoring in order to guide bed- vasive . Labs drawn in the emer- side management. This is particularly true of patients with gency department revealed white-blood-cell count -dependent chronic kidney disease, who may be 22,000 cells/␮L, with 90% and 1% bands, blood less tolerant of large volume than individuals urea nitrogen 67 mg/dL, creatinine 8.1 mg/dL, hematocrit with normal renal function. With the declining use of pul- 34%, and venous lactate 1.2 mmol/L. His Acute Physiol- monary artery and the introduction of early goal- ogy and Chronic Health Evaluation II score at this time, directed therapy as a means for resuscitating patients with calculated retrospectively, was 29. Following admission to septic shock,1 central venous catheters (CVCs) are increas- the ICU, a venous blood gas analysis revealed pH 7.10, ingly being used for this purpose. These catheters allow P 82 mm Hg, and P 52 mm Hg. The patient was CO2 O2 continuous monitoring of central venous pressure to guide subsequently intubated with a 7.5-mm endotracheal tube, fluid administration, as well as point measurement or con- using a rapid sequence protocol with etomidate for seda- tinuous monitoring of central venous oxygen saturation tion and rocuronium for neuromuscular blockade. He was (S ), a surrogate measure of mixed venous oxygen sat- cvO2 placed on mechanical ventilation with the following set- uration (S ) that provides information about the balance vO2 tings: volume assist control, respiratory rate 24 breaths/ between oxygen delivery and consumption at the tissue min, tidal volume 510 mL (8 mL/kg ideal body weight), level. In order to use the central venous pressure and S cvO2 F 1.0, and PEEP 5 cm H O. Peak inspiratory pressure at IO2 2 to guide resuscitation or other aspects of patient the time was 53 cm H O, while mean airway pressure was management, the clinician must verify that the line is in 2 13 cm H2O. Sedation and analgesia for ventilator tolerance the appropriate position and ensure there are no sources of were provided with intravenous boluses of fentanyl and error in the generated data. We present a case of a patient midazolam, administered according to a nurse-driven pro- with chronic kidney disease who presented with sepsis and tocol. His vital signs following intubation were: tempera- respiratory failure, which demonstrates some of the chal- ture 36.7°C, 111 beats/min, 87/ lenges that can arise in these regards and how to approach 39 mm Hg, and S 100%. On examination, the patient pO2 these situations. had breath sounds bilaterally, without crackles or wheezes. He demonstrated an irregular tachycardic rhythm, with no Case Summary murmurs, rubs, S3, S4, or loud P2. His and skin A 54-year-old man with a past medical history notable were unremarkable, and bilateral lower extremities showed for dialysis-dependent chronic kidney disease, diabetes symmetric 1ϩ pitting edema. The patient had bilateral upper extremity dialysis fistulae, both of which demon- strated a palpable thrill. Patient records available at this The authors are affiliated with the Division of Pulmonary and Critical time indicated that the left upper extremity fistula had a Care , Department of Medicine, Harborview Medical Center, pseudoaneurysm. University of Washington, Seattle, Washington. A triple lumen CVC capable of continuously monitor- ing S (Presep, Edwards Lifescience, Irvine, California) The authors have disclosed no conflicts of interest. cvO2 was placed in the left internal jugular vein without diffi- Correspondence: Andrew M Luks MD, Division of Pulmonary and Crit- culty, using ultrasound guidance. The left internal jugular ical Care Medicine, Harborview Medical Center, 325 Ninth Avenue, Box 359762, Seattle WA, 98104. E-mail: [email protected]. was chosen because the physician performing the proce- dure, aware of the pseudoaneurysm of the left-sided fis- DOI: 10.4187/respcare.01762 tula, assumed the patient received via the

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biotic coverage was narrowed to penicillin on hospital day 3. Beginning on hospital day 1, the patient underwent intermittent hemodialysis, with minimal hemodynamic in- stability on the infusion. He was dialyzed using his left upper extremity fistula after the nephrologist ascertained that this was his usable fistula. With intermittent hemodialysis and treatment of his in- fection, the patient’s oxygenation improved, such that his F was 0.4 on hospital day 1, and 0.3 on hospital day 2. IO2 The patient received spontaneous breathing trials (CPAP

5cmH2O with no pressure support) starting on hospital day 1, but failed on this and the following day due to a rapid shallow breathing pattern. On hospital day 3 he main- tained a respiratory rate of 25 breaths/min and a tidal volume of 330 mL during his spontaneous breathing trial, and was subsequently extubated to oxygen by nasal can- nula. The central line was removed following extubation, Figure. Portable chest radiograph taken after insertion of the cen- tral venous catheter in the left in internal jugular vein. The black and the patient was transferred to the medicine ward on arrow points to the tip of the catheter. hospital day 4. He was subsequently discharged from the hospital on hospital day 5 with plans to complete a 14-day course of intravenous cefazolin, dosed with hemodialysis. right upper extremity dialysis fistula and wanted to avoid cannulation on that side. After the portable chest radio- Discussion graph obtained to confirm catheter tip position (Figure) raised concern about possible intra-arterial placement, a CVCs play a key role in the management of patients pressure transducer was attached to the catheter (Ultra- with septic shock and respiratory failure. Our case dem- view, Spacelabs Healthcare, Issaquah, Washington) and onstrates some of the challenges that can arise with place- revealed a central venous pressure waveform with a pres- ment of these devices and interpretation of some of the sure of 17 mm Hg. The CVC was then connected to the data provided by them. continuous S monitoring system (Vigilance II, Edwards The first challenge associated with the CVC is safe and cvO2 Lifescience, Irvine, California), and the initial reading was correct placement of the device. The most important step 94%. A blood gas analysis sample was obtained from the in this regard is to ensure that the introducer needle and central line to calibrate the device and revealed pH 7.39, guide wire are in the central vein, rather than an artery, P 33 mm Hg, P 96 mm Hg, and oxygen saturation prior to insertion of the CVC. This is done using portable CO2 O2 96%. ultrasound to identify the vein prior to needle puncture, to Based on the results of pressure transduction and chest observe the needle entering the appropriate vessel, and to radiography, it was felt that the catheter tip was likely in confirm venous placement of the guide wire prior to in- a persistent left superior vena cava, proximal to the right serting the catheter. Before advancing the guide wire atrium. The S was felt to be elevated due to the pres- through the needle, clinicians can also use pressure trans- cvO2 ence of a dialysis fistula on the same side as the catheter, duction via the 18-gauge needle to verify the presence of through which arterialized blood entered the venous sys- a central venous pressure waveform. In our case we used tem and traveled past the catheter tip. S monitoring ultrasound guidance, as described above, but did not use cvO2 was discontinued, and the central line was used only for pressure transduction prior to guide wire insertion. Cath- infusion of vasopressors and other medications. eter placement proceeded without apparent complication. The patient required a continuous infusion of norepi- Once the CVC has been secured in place, chest radiog- nephrine to achieve a goal of raphy is performed to confirm that the tip of the CVC is in Ͼ 65 mm Hg. The infusion rate varied between 6 and the appropriate position at the junction of the superior 10 ␮g/min before it was discontinued on hospital day 2, as vena cava and the right atrium. In our patient the chest his hemodynamic compromise resolved (the day of pre- radiograph and the initial, uncalibrated S reading were cvO2 sentation is treated as day zero). Following admission, the both concerning for a possible intra-arterial placement. In patient had been started on vancomycin, ceftriaxone, and such situations, providers can employ several tactics to azithromycin pending culture results. Blood cultures drawn verify that the CVC is in a central vein. Pressure trans- in the emergency department subsequently grew group B duction can be used at this point to identify either an ␤-hemolytic streptococci on hospital day 2, and his anti- arterial or venous waveform, although, as noted above,

2120 RESPIRATORY CARE • DECEMBER 2012 VOL 57 NO 12 CHALLENGES ASSOCIATED WITH CENTRAL VENOUS CATHETER PLACEMENT this measurement is more appropriately performed prior to ing. Cardiac catheterization with oximetry can also be insertion of the guide wire and CVC. Second, comparisons performed to evaluate the degree of shunt volume. We did can be made between simultaneous blood gases drawn not consider this diagnosis at the time of the patient’s ad- from the CVC and a known arterial site. Similar values on mission, and, as a result, did not pursue studies to confirm or the 2 samples are indicative of intra-arterial placement, rule out this possibility. while substantial differences, particularly with regard to Once the CVC is safely in place and catheter tip posi- the P , are supportive of intravenous placement. Finally, tion has been confirmed, the clinician can monitor S as O2 cvO2 bedside ultrasound and color Doppler can be used to vi- a means to guide resuscitation of the patient. The S can cvO2 sualize the CVC in a non-pulsatile vessel. In our patient, be obtained as a point measurement off a blood gas drawn pressure transduction and bedside ultrasound were both from the CVC or monitored continuously using a propri- consistent with central venous placement. etary catheter and monitor (Presep or Vigilance II, Ed- After reviewing the chest radiograph and the blood gas wards Lifesciences, Irvine, California), The S serves as cvO2 data, we suspected that our patient had a persistent left a surrogate measure of the S , which provides informa- v¯O2 superior vena cava, a rare anatomical variation, occurring tion about the balance between oxygen delivery and oxy- in only 0.3–0.5% of the population.2 This could have been gen consumption in the tissues.9 Because measurement of confirmed using a chest computed tomography scan, but the S requires a pulmonary artery catheter, and use of v¯O2 we opted not do to this, as the scan results would not have such devices has fallen off in the past decade, following changed patient management. A persistent left superior studies questioning their impact on patient outcomes, S cvO2 vena cava empties into an enlarged coronary sinus and is has become a more commonly followed resuscitation end usually accompanied by a right superior vena cava. The point. vessel can also drain into the left atrium and lead to right- Although monitoring of S is easy to do and provides cvO2 to-left shunt and hypoxemia.3 It is most frequently discov- ready feedback regarding the impact of various interven- ered after accessing a central vein, either for line place- tions, there are important limitations of the parameter about ment or during electrophysiology procedures.4,5 Patients which the user must be aware. First, as our case demon- with this anomaly may also have a higher incidence of strates, clinicians should be wary of using the S to cvO2 conduction system abnormalities and ,6 al- guide resuscitation in patients with dialysis fistulas or par- though none of these issues were seen with our patient. tial anomalous pulmonary venous connection. In such cases The elevated oxygen saturation seen on the S mon- the reported values will be falsely elevated and, as a result, cvO2 itor and on the blood gas drawn from the CVC were likely will not accurately reflect the balance between oxygen due to the ipsilateral dialysis fistula and the fact that ar- delivery and consumption in the tissues. In the case of terialized blood was being returned to the venous circula- partial anomalous pulmonary venous connection, the mag- tion upstream of the catheter tip, thereby raising the satu- nitude of the error will depend on the shunt volume asso- ration and P from true venous levels. Another possible ciated with the particular anomaly. For a dialysis fistula O2 anatomic variant that could explain the elevated oxygen the magnitude of the error will be affected by the blood saturation seen on the sample drawn from the CVC is that flow through the fistula and the downstream position of of partial anomalous pulmonary venous connection. This the catheter tip relative to the fistula and right atrium. The entity includes several usually asymptomatic anatomic vari- greater the flow through the fistula, the more likely that a ants that cause oxygenated blood from the pulmonary ve- high oxygen saturation will be measured from the catheter nous system to drain into the systemic venous system. tip. Blood flow through a dialysis fistula has been reported Common variations include the left upper pulmonary vein to average between 1.3 and 2.7 L/min, depending on draining into the left innominate vein, drainage of smaller whether the patient has a brachial or radial fistula and pulmonary vessels from the right upper lobe into the su- whether or not they have pulmonary hypertension, and perior vena cava, and pulmonary venous drainage into the may even range as high as 3.3 L/min.10 azygous vein, coronary sinus, and inferior vena cava. In In terms of positioning, the CVC must be downstream the case of the scimitar syndrome, the entire right lung (or of the fistula for the S to be affected. This is illustrated cvO2 sometimes a portion of it) drains into pulmonary veins and in a report of a patient with a right-sided hemodialysis then the scimitar vein, which subsequently drains into the fistula, who had 2 catheters placed in his right internal inferior vena cava. Of note, the presence of both persistent jugular vein. The first was a short introducer catheter whose left superior vena cava and anomalous pulmonary venous tip remained in the internal jugular vein and, as a result, return in the same individual has been reported frequently,7 was not in contact with arterialized blood coming from the and this finding can be asymptomatic.8 Confirmation of dialysis fistula via the subclavian vein. The second was a partial anomalous pulmonary venous connection is gener- CVC whose tip was more centrally located in the superior ally made with advanced imaging, such as echocardiogra- vena cava and directly in the path of returning arterialized phy, computed tomography, or magnetic resonance imag- blood from the subclavian vein. The oxygen saturation

RESPIRATORY CARE • DECEMBER 2012 VOL 57 NO 12 2121 CHALLENGES ASSOCIATED WITH CENTRAL VENOUS CATHETER PLACEMENT measured by CO-oximetry off the catheter residing in the aware of these and other important limitations of the de- internal jugular vein was 70.9%, while the corresponding vices in order to avoid inappropriate patient management value measured from the catheter in the superior vena cava decisions. was 96.7%.11 The degree of elevation in the S will also depend on Teaching Points cvO2 the positioning of the catheter tip relative to the fistula and • Ultrasound and pressure transduction should be used the right atrium; the closer the tip is to the dialysis fistula, prior to insertion of a CVC to ensure venous, rather than the greater the amount of arterialized blood flowing by the arterial, placement. Placement should not proceed if there catheter tip, and, as a result, the higher the measured ox- is any doubt regarding whether the needle or wire is in ygen saturation. If the catheter tip resides in the right a central vein. atrium, the effect of the fistula will be reduced, as the arterialized blood will be mixed with considerably more • When questions persist about the location of the CVC venous blood in that location. In fact, the S measured after placement is complete and chest radiography is v¯O2 from the pulmonary artery does not appear to be affected performed, simultaneous blood gases drawn off the CVC at all by a dialysis fistula, as demonstrated in a case report and from a known arterial site and pressure transduction in which the S was noted to be the same when drawn can be used to confirm a venous location. v¯O2 off a pulmonary artery catheter with the fistula open or • Care must be exercised when using the ScvO in patients occluded (68.6% vs 68.3%).12 In our patient’s case, the 2 with left-to-right shunts, including dialysis fistulas or catheter tip was felt to be outside the right atrium, and we anomalous pulmonary venous connection. In such situ- suspected a relatively greater impact from the dialysis fis- ations clinicians should consider alternative resuscita- tula. Flow through the fistula was not measured. In situa- tion end points, such as serum lactate. tions like this, where the validity of the S is in doubt, cvO2 an alternative resuscitation end point should be consid- •S is a surrogate measure of S and provides an cvO2 v¯O2 ered. One such alternative is the serum lactate, which has assessment of the balance between oxygen delivery and been shown to perform as well as the S in management oxygen consumption in the tissues. Because the S cvO2 cvO2 of septic shock.13 overestimates S in shock states, and agreement varies v¯O2 Even in the cases of individuals with normal anatomy, based on the distance of the catheter tip from the right clinicians need to be aware of other issues with S atrium, clinicians should focus on the trends in these cvO2 monitoring.9 Because the tip of central venous lines typi- values rather than the absolute numbers. cally lie in superior vena cava, the S provides only cvO2 information about the balance of oxygen delivery and con- REFERENCES sumption in the cephalad half of the body, and may not 1. Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, truly reflect the S , which takes into account venous v¯O2 et al. Early goal-directed therapy in the treatment of severe sepsis return from the entire body. The depth to which the cath- and septic shock. N Engl J Med 2001;345(19):1368-1377. eter is inserted may also affect the agreement between 2. 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