Critical Assessment of Use of Central Venous Oxygen Saturation as a Mirror of Mixed Venous Oxygen in Severely Ill Cardiac Patients

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1 Criticl Assessment of Use of Centrl Venous Oxygen Sturtion s Mirror of Mixed Venous Oxygen in Severely Ill Crdic Ptients By MELVIN M. SCHEINMAN, M.D., MuRRAY A. BROWN, B.A., AND ELLIOT RAPAPORT, M.D. SUMMARY Bedside ctheteriztion of the right hert with percutneously introduced flowdirected ctheter ws crried out in 24 criticlly ill ptients; 71 determintions of mixed venous oxygen sturtion (MVo2) were obtined. A second ctheter ws inserted either into centrl intrthorcic vein or the right trium for simultneous smpling of centrl venous (CVo2) or right tril (RAo2) oxygen sturtion. For the group s whole, men CVo2 (57.9% ) ws significntly greter thn men MVo2 (53.3% 14.84) (P <.1), but there ws no significnt difference nd correltion ws good between chnges in centrl venous compred to chnges in mixed venous oxygen sturtion. On the other hnd, there ws no significnt men difference s well s n excellent correltion between individul vlues of RAo2 nd MVo2 (r = +.95). Ptients with hert filure or shock showed poor correltion between CVo2 nd simultneously determined MVo2. Furthermore, subjects with shock showed men CVo2 (58.% ) tht ws significntly greter thn men MVo2 (47.5% 15.11). In contrst, there ws no significnt difference between men RAo2 nd men MVo2 nd excellent correltion of individul vlues in ptients with either hert filure or shock. Although CVo2 is poor reflection of MVo2 in subjects with severe hert filure or shock, there ws better correltion between chnges in CVo2 with corresponding chnges in MVo2. In ddition, RAo2 correlted closely with corresponding vlues of MVo2. The reversl of the norml reltionship between CVo2 nd MVo2 under these circumstnces is comptible with the thesis tht low output sttes re ttended by redistribution of blood flow wy from femorl, splnchnic, nd renl circultion with preferentil preservtion of cerebrl blood flow. Additionl Indexing Words: Shock Myocrdil Hert filure A VARIETY of hemodynmic nd biochemicl mesurements hs been used to ssess crdiovsculr function in severely ill ptients. Mny of these require highly skilled technicl support, expensive equipment, or the fcilities of reserch lbortory. Mixed venous oxygen sturtion (MVo2) is n ex- From the Crdiopulmonry Lbortory nd Medicl Services, Sn Frncisco Generl Hospitl, nd the Deprtment of Medicine nd Crdiovsculr Reserch Institute, University of Cliforni, Sn Frncisco Medicl Center, Sn Frncisco, Cliforni. 165 cellent index of systemic flow since it is directly proportionl to crdic output when rteril oxygen content nd oxygen consumption remin constnt. Furthermore, mesurement of MVo2 is simple nd inexpensive nd cn be performed by reltively unskilled personnel. This study ws supported in prt by Grnt HE from the U. S. Public Helth Service. Address for reprints: Melvin M. Scheinmn, M.D., Crdiopulmonry Lbortory, Sn Frncisco Generl Hospitl, 11 Potrero Avenue, Sn Frncisco, Cliforni 9411.

2 166 Tble I Summry of Oxygen Sturtion nd Pressures in All Ptients Ptient no. nd dignosis Group I (no hert filure) 1. Sepsis, hypotension 2. Hert block, cute myocrdil Hert rte, 45 Hert rte, 78 Hert rte, 1 3. Pulmonry embolus Group II (hert filure) 1. Acute myocrdil 2. Chronic obstructive bronchopulmonry disese 3. Hypertensive crdiovsculr disese 4. Acute myocrdil 5. Acute myocrdil 6. Acute myocrdil 7. Acute myocrdil 8. Ischemic hert disese 9. Cirrhosis, pulmonry hypertension, cute ortic insufficiency 1. Ischemic hert disese 11. Crdiomyopthy 12. Sepsis, hert filure 13. Myocrditis Oxygen sturtion (%) MV2 Arteril CVo2 RAo2 RVo2 PAo SCHEINMAN ET AL. Pressures (mm Hg) PA (men) 2715 (19) 412 (28) 312 (22) (18) (27) (25) (25) (21) (1) (45) (35) (25) 25 (45) 5522 (37) 3725 (29) (25) (32) (33) 6518 (36) (34) (36) (35) (22) RV >

3 CENTRAL VENOUS OXYGEN SATURATION 167 Tble 1 (continued) Ptient no. nd Oxygen sturtion (%) MV, Arteril Pressures (mm Hg) dignosis CVo2 RA2 RVo2 PAo2 2 PA (men) RV Group III (shock) 1. Postcrdiopulmonry rrest 2. Acute myocrdil 3. Acute myocrdil 4. Acute myocrdil 5. Acute myocrdil 6. Acute myocrdil 7. Postcrdic rrest, sepsis 8. Postcrdic rrest Abbrevitions: CV = centrl = PA pulmonry rtery (16) 312 (2) 322 (26) (4) (35) 2515 (2) (3) (33) 535 (4) 453 (37) 525 (45) 4831 (4) 4737 (4) 315 (22) 3217 (23) 3518 (25) 2715 (2) 3519 (25) 351 (2) 3512 (21) venous; RA = right trium; MV = mixed venous; RV = right ventricle; Recently, the clinicl usefulness of centrl venous oxygen sturtion (CVo2) in ssessing hemodynmic impirment in the ptient with cute myocrdil hs been emph- sized.1-3 The bsic ssumption in these studies is tht CVo2 is n ccurte reflection of MVo2. However, to our knowledge, comprtive mesurements of CVo2 nd MVo2 in ptients

4 168 with severe hert filure or shock, regrdless of the cuse, hve not been crried out. The purpose of the present study ws to determine whether the oxygen sturtion of blood withdrwn from ctheters tht re ordinrily used to monitor centrl venous pressure is n ccurte reflection of MVo2 in criticlly ill ptients. Methods Percutneous right hert ctheteriztion ws performed t the bedside in n intensive coronrv cre unit on 24 ptients with known or suspected cute myocrdil to ssess the degree of myocrdil dysfunction, response to therpy, or both. Centrl venous ctheters* were inserted through medil ntecubitl or externl jugulr vein. Intrthorcic plcement of the ctheter ws confirmed by roentgenogrphy in ll ptients. The Sttisticl Anlyses of Dt ble 2 SCHEINMAN ET AL. ctheter tip ws found in the right trium in seven ptients, ws clerly in the superior ven cv in 12, nd ly in the innominte or subclvin veins in the others. In ddition, no. 1 nylon ctheter (Portex) ws inserted through 17-guge needle into medil ntecubitl vein nd "floted," under electrocrdiogrphic nd pressure monitoring,t into either the pulmonry rtery or right ventricle. In most ptients the ctheter ws connected to dilute heprin drip to llow seril mesurements of pressure nd MVo2 sturtion. Approximtely 1 ml of blood ws removed from the no. 1 nylon ctheter to cler the line. An dditionl 2 ml ws spirted into 2-ml heprinized glss syringe. Simultneously, 5 ml of *Brdic Model No R; needle guge 14, ctheter length 24 inches. telectronics for Medicine DR-2 recorder nd Stthm P23D strin guge. Simultneous No. of Men nd SD mesurements mesurements (%) r P vlue All ptients CV2- MV2 52 CV i <.1 MV i ACVo2- AMVo >.5 RA2- MV2 19 RA2 52. i >.5 MV ARAo2- AMVo >.5 Group I CV2 - MV2 7 CV <.1 MV ± ACVO2- AMVo >.5 Group II CV2- MV2 22 CV i <.1 MV = CV 2-AMV, >.5 RA2- MV2 9 RA ± <.2 MV ± 7.55 ARAo2 - AMVo <.4 Group III CV2- MV2 23 CV2 58. i <.1 MV i ACVo2 - AMVo >.5 RA2- MV2 1 RA <.4 MV ± 19.9 ARAo2- AMVo >.5 Abbrevitions: SD= stndrd devition; r = -- I - correltion coefficient: P vlue I obtined bv -.y pired t-test.

5 CENTRAL VENOUS OXYGEN SATURATION blood ws discrded from the centrl venous line while n dditionl 5 ml ws spirted into heprinized glss syringe. Oxygen sturtion ws mesured in both smples immeditely fter withdrwl.* Duplicte smples showed n verge difference of.9% oxygen sturtion. Fiftytwo simultneous mesurements of MVo2 nd CVo2 were obtined in 18 ptients. In seven ptients simultneous determintions of right tril oxygen sturtion (RAo2) nd MVo2 were performed. Arteril smples were spirted from ctheters previously inserted into either brchil or femorl rtery. The rteril blood ws nlyzed for ph, Pco2, Po2, nd oxygen sturtion. Ptients were seprted into three groups: Group I consisted of three severely ill ptients who hd no clinicl or hemodynmic evidence of left ventriculr filure or shock; group II consisted of 13 ptients with cler-cut evidence of left ventriculr filure, usully mnifested by gllop rhythms, crdiomegly, vsculr congestion on chest roentgenogrm, nd elevted pulmonry rtery pressure (ptients were studied either during or shortly fter n episode of cute pulmonry edem); nd group III contined the eight hypotensive ptients who hd poor cpillry filling nd were either oliguric or nuric (most of them hd clinicl nd hemodynmic evidence of left ventriculr filure s well). The etiologic dignosis for ech ptient is presented in tble 1. z I- 4 I-- *A-O oximeter Model No. 18. loor- 9C C4 w Qe 4 ix AC z >; 2( IC U "~~ ~~~ A, _ { * 11 I X ~~~GROUPS * -- * R.A. 2 ~~ ~~ I GROUPSI I II I^I^IX s n o r W% 1 2 ^ M.V. -2 % SATURATION o so 9 IoU Figure 1 Comprison by groups of ll determintions of CVO2 nd RAO2 with corresponding vlues of MV2. Results The dt nd sttisticl nlyses for the three groups of ptients re reported in tbles 1 nd 2. The reltionship between ll vlues of MVo2 nd the simultneously determined RAo2 or CVo2 is illustrted in figure 1. Men CVo2 ws significntly greter thn the men MVo2 (P <.1), but there ws no significnt difference between the men sturtions of RAo2 nd MVo2. Furthermore, the correltion ws better between MVo2 nd RAo2 (r +.95) thn between MVo2 nd CVo2 (r = +.86). Chnges in oxygen sturtion from ll smples of blood from the pulmonry rtery or right ventricle (AMVo2) compred to simultneously determined chnges in oxygen sturtion from the centrl veins (ACVo2) or right trium (ARAo2) re depicted in figure 2. There ws no significnt men difference nd correltion ws good between ACVo2 nd AMVo2 in 34 determintions (r = +.9). >uz ALL DETERMINATIONS +31 ~ U * < L ^ e S. ~ ~~~..br,. _ * C.V. 2 (r=.9) * R.A. 2 (r=.95) M.V. 2 - % SATURATION 169 Figure 2 Comprison of chnges in RA2 nd CVO, with corresponding chnges in MVO2 for ll determintions.

6 1 The stndrd error from the liner regression line ws 7.9. In 12 simultneous determintions there ws no significnt difference in mens nd correltion ws good between ARAo2 nd AMVo2 (r = +.96). The stndrd error from the regression line ws 5.4. In group I, there ws no significnt difference between men CVo2 nd men MVo2, nd there ws close correltion between the seven vlues in this group. Likewise, there ws excellent correltion between AlCVo2 nd AMVo2 in this group, but only four determintions were mde (r = +.98). No RAo2 smples were obtined in this group. In group II, no significnt men differences were found between simultneous mesurements of CVo2 nd MVo2 or between RAo2 nd MVo2. However, the correltion ws better between vlues of RAo2 nd MVo2 (r=+.83) thn between CVo2 nd MVo2 (r=+.). Similrly, there ws no significnt men difference between ACVo2 nd AMVo2 or between ARAo2 nd AMVo2, but the correltion ws better between ARAo2 nd AMVo2 (r = +.99) thn between ACVo2 nd AMVo2 (r= +.79). In group III, men CVo2 (58.% ) ws significntly higher thn men MVo2 (47.5% 15.11) (P <.1). In contrst, there ws no significnt difference between men RAo2 (5.9% ) nd MVo2 (49.2% 19.9), nd correltion ws good between individul determintions (r = +.97). Chnges in CVo2 were compred with simultneous chnges in MVo2 in 17 instnces. There ws no significnt difference between the mens of the sturtion chnges in the two smpling sites, nd the correltion coefficient, r, equled Similrly, there ws no significnt difference in mens, nd correltion ws excellent between ARAo2 nd AMVo2 (r = +.9). Discussion The objective of this study ws to determine whether or not the oxygen sturtion of blood spirted from ctheter used to mesure centrl venous pressure is n ccurte reflection of MVo2. Ctheters used to monitor SCHEINMAN ET AL. centrl venous pressure were introduced by the house stff, nd no effort ws mde to direct the ctheter to specific intrthorcic site. The only requirement for inclusion of subjects into this study ws roentgenogrphic locliztion of the ctheter tip within the thorx. Mixed venous 2 sturtion ws determined by withdrwl of blood from smll nylon ctheter which ws flow-directed t the bedside into the pulmonry rtery or the right ventricle when it ws not possible to mnipulte the ctheter into the pulmonry rtery. The ctheter ws inserted by one of the uthors (M.S.) t the bedside under electrocrdiogrphic nd pressure monitoring. The precutions, overll sfety, nd uses of this technic re summrized elsewhere.4 Centrl venous 2 sturtion proved to be n ccurte reflection of MVo2 in the seriously ill ptient only when the ptient ws not in shock or hert filure. When shock ws present, not only ws CVo2 consistently higher thn MVo2, but lso more importntly, the correltion between individul vlues of MVo2 nd CVo2 ws very poor (r = +.55). Although ptients with hert filure showed no difference in mens, there ws poor correltion in individul ptients between vlues of CVo2 nd MVo2 (r -.). + Similrly, this group reveled reltively poor correltion between chnges in CVo2 nd chnges in MVo2 s these were followed over period of hours to dys (r = +.79). We believe tht these observtions result from regionl blood flow redistribution seen with shock or hert filure, or both. Specificlly, inferior ven cvl blood normlly hs n oxygen sturtion somewht higher thn tht of mixed venous blood lrgely becuse of the mjor contribution of highly sturted renl venous effluent.6 Shock nd hert filure, both of which produce profound reductions in renl blood flow,7-9 will result in the renl blood flow hving less influence on inferior ven cvl sturtion. Similrly, blood flow is reduced to the kidneys, muscles, skin, nd splnchnic regions in hert filure.'-12 If, in ddition, there is preferentil mintennce of cerebrl blood flow in shock or congestive

7 CENTRAL VENOUS OXYGEN SATURATION hert filure,'3-17 internl jugulr venous blood will be more highly sturted thn blood returning from other res of the upper prt of the body. The net expected result would be tht superior ven cvl sturtion would now tend to be distinctly higher thn both inferior ven cvl blood nd the resultnt MVo2 detected by ctheter in the right ventricle or pulmonry rtery. Our dt, therefore, re comptible with the thesis tht our cutely ill ptients with hert filure nd shock hd severely low crdic outputs with proportiontely greter diminution in splnchnic, renl, nd femorl rteril blood flow thn in cerebrl blood flow. Of prticulr interest ws ptient (group II, cse 13) in whom the tip of the centrl venous ctheter ws locted in the very distl portion of the right xillry vein nd yet in whom CVo2 ws consistently higher thn MVo2. We presume tht this observtion is explined by the findings of Muth nd co- z - D - t\ CN I, IL I I I Z 1( 2 3-u N -l1 6 5C * i' -,S! 9 8, -%m ~~~~,, I F, I, _, 1o 1 I, * CV. 2 (r=o.551 * R.A. 2 (r=o97) 2 1 M.V. 2- % SATURATION Figure 3 Comprison of CV2 nd RA2 with corresponding vlues of MV2 in ptients with shock. 171 workers'8 who showed mintennce of norml blood flow to resting muscle in ptients with hert filure. Donld'9 speculted tht this my result from the fct tht sufficient vsodilting ctbolites re produced during sttic posturl ctivity by muscle to ensure norml blood flow. Goldmn nd ssocites' 2 recently emphsized the clinicl usefulness of mesurements of CVo2 in ptients with cute myocrdil. They showed tht in ptients brething room ir, CVo2 of less thn 6% ws usully ssocited with hert filure or shock. Moreover, they found good correltion between the 2 sturtion in the superior ven cv nd pulmonry rtery in ptients with wide rnge of crdic outputs mesured in the ctheteriztion lbortory. Our dt differ somewht from these findings. Centrl venous oxygen sturtion ws significntly higher thn MVo2, nd this finding ws further ccentuted for vlues of CVo2 below 6% (fig. 3). Furthermore, we observed very poor correltion between CVo2 nd MVo2 in ptients with hert filure or shock, or both. Consequently, we believe tht one cnnot ssume tht CVo2 properly reflects MVo2 in ptients with low output sttes. The poor correltion between CVo2 nd MVo2 in ptients with shock or filure, or both, should not be used to negte entirely the usefulness of mesurements of CVo2. In monitoring the criticlly ill ptient, chnges in CVo2 re obviously more importnt thn the bsolute vlues. It should be noted tht our dt showed good correltion between chnges in CVo2 nd respective chnges in MVo2, lthough individul exceptions were still observed, prticulrly in the ptients with hert filure. In contrst, RAo2 shows excellent correltion with corresponding vlues of MVo2 nd is obviously fr better pproximtion of the ltter thn is CVo2. It is of interest tht in one ptient (group II, cse 9) close correltion between RAo2 nd MVo2 ws demonstrted. The ctheter ws indvertently dislodged from the right trium nd its tip ws subsequently relocted in the superior ven

8 172 cv. CVon ws then demonstrted to be higher thn MVo2. The results of this study support the rgument tht centrl venous ctheters should be positioned in the right trium (preferbly in the superior portion) when monitoring the cutely ill ptient with myocrdil. The close correspondence observed between RAo2 nd MVo2 justifies use of right tril oxygen content (together with n oxygen consumption nd rteril oxygen content) to pproximte crdic output by mens of the Fick formul. In ddition, filling the ctheter with sline permits recording of the right tril electrogrm2 which my be helpful in dignosing difficult rrhythmis. The right tril ctheter lso provides for more centrl injection site for dye-dilution curves. Finlly, it permits redy insertion of electrode cbles through the ctheters for emergency tril or ventriculr pcing. Acknowledgment We grtefully cknowledge the technicl ssistnce of Mrs. Nncy Fleetwood nd Miss Brbr Koller. References 1. GOLDMAN, R. H., BRANIFF, B., HARRISON, D. C., AND SPIVACK, A. P.: Use of centrl venous oxygen sturtion in coronry cre unit. Ann Intern Med 68: 128, GOLDMAN, R. H., KLUGHAUPT, M., METCALF, T., SPIVACK, A. P., AND HARRISON, D. C.: Mesurement of centrl venous oxygen sturtion in ptients with myocrdil. Circultion 38: 941, HUTTER, A. M., JR., AND Moss, A. J.: Vlue of seril centrl venous oxygen sturtions in cute myocrdil. (Abstr.) Circultion 37 (suppl. VI): VI-14, SCHEINMAN, M. M., ABBOTT, J. A., AND RAPAPORT, E.: Clinicl uses of flow-directed right hert ctheter. Arch Intern Med, In press. 5. BARRATT-BOYES, B. G., AND WOOD, E. H.: Oxygen sturtion of blood in the vene cve, right-hert chmbers, nd pulmonry vessels of helthy subjects. J Lb Clin Med 5: 93, CARGILL, W. H., AND HIcKAM, J. B.: The oxygen consumption of the norml nd the disesed humn kidney. J Clin Invest 28: 526, SCHEINMAN ET AL. 7. MERRILL, A. J.: Edem nd decresed renl blood flow in ptients with chronic congestive hert filure: Evidence of "forwrd filure" s the primry cuse of edem. J Clin Invest 25: 389, MOKOTOFF, R., Ross, G., AND LEITER, L.: Renl plsm flow nd sodium rebsorption nd excretion in congestive hert filure. J Clin Invest 27: 1, LAUSON, H. D., BRADLEY, S. E., AND COURNAND, A.: Renl circultion in shock. J Clin Invest 23: 381, BISHOP, J. M., WADE,. L., AND DONALD, K. W.: Chnges in jugulr nd renl rteriovenous oxygen content difference during exercise in hert disese. Clin Sci 17: 611, MYERS, J. D., AND HICKAM, J. B.: Estimtion of the heptic blood flow nd splnchnic oxygen consumption in hert filure. J Clin Invest 27: 62, RAPAPORT, E., WEISBART, M. H., AND LEVINE, M.: Splnchnic blood volume in congestive hert filure. Circultion 18: 581, STONE, H. H., DONNELLY, C. C., MACKRELL, T. N., BRANDSTATER, B. J., AND NEMIR, P., JR.: Effect of induced hemorrhgic shock on cerebrl circultion nd metbolism in mn. Surg Forum 5: 789, NOVACK, P., GOLUBOFF, B., BORTIN, L., SOFFE, A., AND SHENKIN, H.: Studies of the cerebrl circultion nd metbolism in congestive hert filure. Circultion 7: 724, MOYER, J. H., MILLER, S. I., AND SNYDER, H.: Cerebrl hemodynmics in ptients with hert filure ssocited with hypertension nd the response to tretment. J Clin Invest 34: 121, CORDAY, E., AND WILLIAMS, J. H.: Effect of shock nd of vsopressor drugs on the regionl circultion of the brin, hert, kidney, nd liver. Amer J Med 29: 228, SMITH, L. L., REEVES, C. D., AND HINSHAW, D. B.: Hemodynmic ltertions nd regionl blood flow in hemorrhgic shock. In Shock nd Hypotension, edited by L. C. Mills nd J. H. Moyer. New York, Grune & Strtton, Inc., 1965, p MUTH, H. A. V., WORMALD, P. N., BISHOP, J. M., AND DONALD, K. W.: Further studies of blood flow in the resting rm during supine leg exercise. Clin Sci 17: 63, DONALD, K. W.: Hemodynmics in chronic congestive hert filure. J Chronic Dis 9: 476, ROBSON, M. C.: Technique for obtining ccurte reproducible centrl venous pressure. Johns Hopkins Med J 122: 232, 1968.