- Email: [email protected]
Depression of intramyocardial oxyhemoglobin dissociation by angiographic contrast media
Depression dissociation
of intramyocardial by angiographic
oxyhemoglobin contrast media
David S. Sheps, M.D. Bruce F. Cameron, M.D., Ph.D.* Stephen M. Mallon, M.D. Leonard S. Sommer, M.D. William C. Lo, A.S. Donald R. Harkness, M.D. Robert J. Myerburg, M.D. Miami, Fla.
Several potentially deleterious effects of contrast material have been described in the past decade.‘-” These have included effects of the injection of a hyperviscous and hypertonic solution on the size and shape of red cells, certain hemodynamic and electrocardiographic changes, a tendency to acidosis, and a depression of blood calcium levels. The production of acidosis by’ the injection of water soluble contrast materials has been clearly demonstrated.‘. 3. 3.R. 9. I0 However, the significance of this finding upon oxygen delivery by red blood cells has been questioned.” When oxygen delivery is described in terms of P50, that value is expressed either as P50 at pH 7.4 or P50 in vivo. Usually plasma pH adequately reflects the intrared blood cell pH throughout the physiologic range. However, angiographic contrast medium has been shown to alter the red blood cell pH gradient. Therefore, in this situation, plasma does not reflect intra-red blood cell pH. Previous workers have measured intra-red blood cell pH after the addition of contrast medium with differing results.“. I” From the Divisions Medicine, University laou Cancer Research
of Cardiology and Hematology, of Miami School of Medicine, Institute, Miami, Fla.
Supported
by Florida
Received
for publication
Heart Sept:
Awxiation
Accepted
for publication
Dec. 27, 1978.
Grant
No. 75 AG 213.
25, 1978.
Reprint requests: David S. Sheps, M.D., Associate cine, Division of Cardiology, School of Medicine, North Carolina at Chapel Hill, 349 Clinical Science Hill, N. C. 27514. *Dr. Cameron Association.
OOO2-8703/80/020193
is an Established
Department of and the Papanico-
Investigator
+ 05$00.50/O
0 1980
of the
The
Professor of MediThe University of Bldg. 229H Chapel American
Heart
C. V. Mosby
Co.
The purpose of this study was to examine the effects of contrast medium in an experimental system where extracellular pH was kept constant using a highly buffered red blood cell solution. Thus, all P5O’s were measured under the same conditions (pH 7.4, PCO, 40, and temperature 37” C.) and any changes seen would therefore directly reflect changes in intra-red blood cell pH. In addition, the effect of contrast medium on the red cell pH gradient was examined anerobically. It has previously been shown that contrast media do not alter red blood cell 2,3 DPG,” which is the only other known explanation for acute changes in P50 in this system. In addition to the in vitro studies, in vivo studies were performed on blood drawn simultaneously from the coronary sinus and peripheral arterial system prior to, and one minute and five minutes after selective injection of the left coronary artery with contrast material. Methods In vitro studies. Blood was drawn from the antecubital vein of normal volunteers into tubes containing sodium heparin. Methylglucamine 3,5diacetamido-2,4,6-triiodobenzoate, 66% aqueous solution (Renografin 76) was added to blood in concentrations varying from .02 to .O&.c./c.c. blood, and incubated for a constant time interval prior to measurement of P50. The effect of variation of incubation time from one minute to 30 minutes was evaluated at a Renografin concentration of .O~C.C./C.C.blood.
American Heart Journal
193
Sheps
et
al.
I
*Oh O_r
II
I/L
10 20
30
2. Effect of variation of incubation time on P50 with a constant concentration of 0.06 ml. Renografin/ml. blood. P5O’s are expressed as percentage change from control (without Renografin). Fig.
1. P50 after incubation with Renografin at various concentrations as shown. All samples were incubated at a constant time interval of 30 minutes. Results are expressed as percentage of control values (without Renografin). Fig.
I. Red blood cell pH gradients (Plasma pH-Intraerythrocyte pH) in the control state and after 30 minutes of incubation with Renografin .06 c.c./c.c. blood
Table
Control
Renografin
0.24 0.20 0.20 0.21 0.20 0.20 0.20 0.207 0.015
0.07 0.05 0.08 0.05 0.06 -0.03 -0.02 0.037 0.044
Blood hemoglobin was measured with an IL 182 cooximeter. Blood oxygen dissociation curves were obtained by a modification” of the method of Longmuir and Chow.” The curve was measured at PCO, 40, pH 7.4, and 37” C. on whole cell suspensions in 0.16 M sodium phosphate buffer in a 30 C.C.closed cell. Buffers and blood samples were thoroughly equilibrated with a gas mixture containing 19.6% oxygen prior to introduction into the chamber. The cell suspensions were deoxygenated by beef heart mitochondrial succinate respiration (without CO, production) and the PO, was measured with a membrane type oxygen electrode (YSI, model 53 oxygen monitor). The oxygen signal was continuously recorded on a Kip and Zonen BD 9 recorder. All curves were measured in duplicate, and duplicate determinations on the same sample agreed to within + 0.25 mm. Hg.
194
IN
5”
TIM:01 INO~OATION IN MINUTES
RENOGARFIN CONTENT (ml/mlMood)
Mean Std dev T = 11.02 P < .OOOl
I
Red cell and plasma pH’s were measured using an IL 213 blood gas analyzer at 37” C. The red cell lysate was obtained by the freeze-thaw technique.‘!’ PH gradients were therefore obtained across the red cell membrane in the control state, and after incubation with Renografin for 30 minutes (.06 C.C. Renografin/c.c. blood) at 37” c. In vivo studies. Eleven adult patients who were undergoing cardiac catheterization and selective coronary arteriography were studied. Arterial catheters were introduced percutaneously through the femoral artery and venous catheters via a cutdown into the basilic vein. The venous catheter was positioned in the proximal coronary sinus. The position was verified by a combination of the fluoroscopic location and by the low oxygen saturation. In eight patients, studies were performed approximately ten minutes after left ventriculography. In three patients, studies were performed prior to left ventriculography. Prior to the first coronary injection, control samples were obtained from the proximal coronary sinus and the central aorta. Contrast material was then selectively injected into the left coronary artery (approximately 6 to 12 ml. over 3 to 4 seconds). One minute and five minutes after injection, repeat blood samples were obtained from the proximal coronary sinus and the central aorta. Blood samples were cooled on ice, and oxyhemoglobin dissociation curves and P50 were determined in duplicate within twelve hours. Results
The effects of Renografin on whole blood P50 in concentrations (as outlined above) which would be attained during cardiac catheterization were studied on blood samples drawn from eight Effect of Renografin
on blood
Fehntnry,
P50 in vitro.
1980, Vol. 99, No. 2
Myocardial
oxyhemoglobin
dissociation
II. Differences in P50 between coronary sinus and aorta before and after left coronary arteriography
Table
Control cs
Ao
29.86 28.08 26.63 27.43 26.11 25.56 25.78 28.93 27.30 k 1.56 SEM .55
28.58 26.62 28.53 26.28 25.56 25.78 28.57 27.13? 1.37 SEM .52
*Significant, p < 0.01. Abbreviations: CS = coronary
A (CS-Ao) -.50 .Ol -1.10 -.17 0 0 .36 -.20, .47 SEM .18
CS
Ao
28.46 26.77 25.92 28.84 25.77 22.56 25.30 28.57 26.52 k 2.12 SEM .75
29.71 29.23 30.40 26.44 22.83 26.90 28.21 27.67 i 2.58 SEM .97
sinus; Ao = aorta, A = difference
Heart
Journal
A (CS-Ao)
of aorta from coronary
patients. For this series of experiments, all blood samples were incubated with Renografin at a constant time interval of 30 minutes. The average blood Renografin concentration attained during angiography was estimated at .02 to .04 C.C. Renografin/c.c. blood. This is based on an average total dose of 100 to 200 c+c. of contrast at an average blood volume of 5 liters. Concentration added in vitro ranged from .02 to .08 C.C.Renografin/c.c. blood in all eight patients. The results are depicted in Fig. 1 as percentage decrease at each concentration when compared to the control P50. As shown in Fig. 1, the P50 progressively decreased throughout the range of concentrations studied. In two patients in whom higher concentrations were studied, P50 decreased even further. The changes from control values were significant (p < .Ol) by Student’s t test for Renografin concentration up to .08 m1Jc.c. blood. The effect of the time of incubation of Renografin with blood on P50 was studied at a dose of .06 C.C. Renografin/c.c. blood. The time of incubation refers to the time interval prior to introduction of the blood sample into the closed cell. Results of variation of incubation time are shown in Fig. 2. In both patients studied, a significant decrease in P50 was seen at one minute incubation. This remained constant up to ten minutes of incubation, beyond which point there were further decreases at 15,20, and 30 minutes of incubation. Although the absolute decrease at one minute was only 3 to 5% of the control value, this represented a change of .7 mm. Hg which
American
5 Minute
1 Minute
-1.25 -2.46 -1.56 -.67 -.27 -1.60 .36 -1.06* k .94 SEM .36
cs
Ao
29.08 26.28 26.91 26.19 26.27 23.11 25.23 29.11 26.52 t 1.96 SEM .69
29.71 28.25 27.19 27.12 26.61 23.11 25.51 29.11 27.07 t 2.10 SEM .74
sinus; SEM = standard
A(CS-Ao) -.63 -1.97 .28 -.93 -.34 0 -.28 0 -.55 t 65 SEM .23
~~~~ of the mean.
is well beyond our range on the same blood sample
of reproducibility (i.e., i 0.25 mm.
W. The effects of Renografin .06 c.c.1c.c. blood on the red blood cell transmembrane pH gradient were studied in vitro in seven normal subjects. The differences between plasma and intraerythrocytic pH were compared in the control state and after 30 minutes of incubation with Renografin. The addition of Renografin decreased the plasma pH and the difference between plasma and intraerythrocytic pH (Table I). The mean pH gradient was 0.21 + .Ol prior to the addition of Renografin. The gradient after incubation with Renografin was .04 +- .04, p < .OOOl. In vivo effects of Renografin. Control samples were simultaneously obtained from the proximal coronary sinus and central aorta, and repeat samples were obtained at one minute and five minutes following injection of the left coronary artery in the 11 patients studied. In eight patients these determinations were performed after left ventriculography, and in three they were performed prior to left ventriculography. The results in the initial group of eight patients are shown in Table II. There is no significant difference between P5O’s from coronary sinus or aorta in the control period. At one minute after left coronary injection, the decrease of coronary sinus as compared to aortic P50 is significant (p < .Ol Student’s t test). This difference is reduced by five minutes post-injection when values approach the control state.
195
Sheps
et al.
When the coronary arteries were injected prior to left ventriculography there was no difference between simultaneous coronary sinus or aortic samples prior to injection, or one minute or five minutes after injection. Discussion
Intravascular injection of radiographic contrast material results in a complex series of potentially deleterious effects. Most of these effects have been attribued to the contrast material’s hypertonicity and high viscosity. A lowering of ionized calcium levels has been described secondary to angiographic contrast material which may be implicated in cases of hypotension secondary to contrast injection.’ Initially, the acidosis secondary to contrast material was thought to affect oxyhemoglobin dissociation,’ but recently it has been stated that there is no effect on oxyhemoglobin dissociation since intra-red blood cell pH is not affected by angiographic contrast media. Instead, it was stated, contrast causes an extrusion of hydrogen ions from the red cell.” The results of this study are in agreement with that of Lichtman and associates,!’ referred to above. The decreased P50 seen in our in vitro and in vivo studies secondary to contrast material is explained as follows: The contrast medium (Renografin 76) is a salt of an impenetrable anion, and by balancing negative ions within the red cell alters the transmembrane ionic charge gradient (seeTable I). When the red cell interior is strongly buffered with respect to the suspending medium,” the result is a relative acidification of the medium without change in intracellular pH; when the suspending medium is strongly buffered, as in our studies, the reduction of the pH gradient will result in an increase in intracellular pH. The P50 of the blood then decreasesdue to the Bohr effect’,’ when compared to the same blood P50 prior to addition of contrast medium with an intra-red blood cell pH of 7.2. We and others have shown that this effect is both dosageand time-dependent.’ The exact situation in vivo is not known and is probably dependent upon blood tlow and relative buffering capacity of intra- and extra-red blood cell spaces. The equilibrium studies of Lichtman and associates” are at one extreme where the entire pH change is extracellular. The red blood cell suspension system that we have examined is
196
at the other extreme where the entire change is intracellular. The actual situation in vivo would depend on the relative buffering capacity of in traand extra-red blood cell spaces. In areas of rapid blood flow, the changes described are of little consequence since the dye is rapidly diluted. However, in areas of myocardium distal to a critical coronary lesion, these effects may take on more significance. This is theoretically possible for two reasons. First, the stagnation of blood tlow would allow tissues to be exposed to the effects of the contrast media for a longer time period. Second, the chronically ischemic tissue bed experiences a shift to anerobic metabolism with an increase in glucose consumption, lactate production, a decrease in pH, and ion shifts.“-“* If ischemia is severe enough, there may be a release of cardiac lysosomal enzymes’; which may impair transport functions of cell membranes. This would lessen the metabolic differences between intracellular and extracellular spaces. The increased total CO, produced by ischemia’” would offer a better buffering capacity than normal tissue at normal rates of blood flow. These conditions would favor the kind of changes in P50 seen in our study done in a highly buffered red blood cell solution. The magnitude of these effects in vivo is unknown. In this regard, Caulfield, and colleagues,’ using a protocol similar to ours, found that the effect of Renografin on ionized calcium was of a greater magnitude and duration in patients with coronary artery disease than in normals. When the normal sequence of cardiac angiography was reversed (i.e., coronary arteriography performed prior to left ventriculography), no effect on P50 was detected one minute or five minutes after the injection of the left coronary artery. This suggests that the effects are additive and dose-related, as seen in our in vitro studies. The ultimate effects of contrast medium on oxyhemoglobin dissociation are complex and dependent upon dosage and blood flow, but the direction of change in P50 is probably most influenced by the buffering capacity of the ambient tissue. Summary
The effect of the addition of radiographic contrast material (Renografin) to blood on the oxyhemoglobin dissociation curve and P50 was measured by a metabolic deoxygenation tech-
February,
1980, Vol. 99, No. 2
Myocardial
nique in a strongly buffered red cell suspension. With incubation time constant, increasing doses produced progressive decreases in P50. With incubation time varied at a constant dose, a decrease in P50 was seen after only one minute. In addition, in vivo studies were performed on 11 patients undergoing cardiac catheterization. Simultaneous proximal coronary sinus and aortic samples were drawn as controls, and then at one minute and five minutes after injection of the left coronary artery. In eight patients studies were performed after, and in three prior to left ventriculography. At one minute after left coronary injection there was a significant decrease of coronary sinus as compared to aortic P50 (p < .lO) (only when left ventriculography was performed prior to coronary arteriography). The magnitude of these effects in vivo is unknown, but they would be expected to be more severe in areas distal to a critical coronary lesion due to stasis of blood flow and ischemic metabolic changes.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14. REFERENCES 1.
2.
3.
4.
15.
Braunwald, E., and Swan, H. J. C., ed.: Cooperative study on cardiac catheterization, Circulation 37(Suppl. 3):81, 1968. Lachlan, M.: Biochemical and other changes occurring in infants during angiography, Proc. R. Sot. Med. 63:46, 1970. Rosenthal, A., Litwin, B. S., and Laver, M. B.: Effect of contrast media used in angiocardiography on hemoglobin-oxygen equilibrium, Invest. Radiol. 8:191, 1973. Friesinger, G. C., Schaffer, J., Criley, M., Gaertner, R. A., and Ross, R. S.: Hemodynamic consequences of the injection of radiopaque material, Circulation 31:730, 1965.
American
Heart
Journal
16.
17.
18.
19.
oxyhemoglobin
dissociation
Levin, A. R., Grossman, H., Schubert, E. T., Winchester, P., and Gilladoga, A.: Effect of angiocardiography on fluid and electrolyte balance, Am. J. Roentgenol. 105:777,1969. Marshall, M., and Henderson, G. A.: Tendency to acidosis following injection of radio opaque contrast material, Br. J. Radiol. 41:190, 1968. Berg, G. R., Hutter, A. M., and Pfister, R. C.: Electrocardiographic abnormalities associated with intravenous urography, N. Eng. J. Med. 28987, 1973. Caulfield, J. B., Zir, L., and Harthorne, W. J.: Blood calcium levels in the presence of arteriographic contrast material, Circulation 52:119, 1975. Lichtman. M. A.. Murahv. M. S.. Whitbeck. A. A.. Poaal. M., and Lipchik, E. 0.: Acidification of plasma by the yed cell due to radiographic contrast materials, Circulation 52:943, 1975. Rosenthal, A., and Mesrobian, A.: The relationship between angiography, intraerythrocytic pH and hemoglobin equilibrium, Invest. Radiol. 10:140, 1975. Cameron, B. F.: Biphasic blood oxygen dissociation curves in hemoglobin S hemoglobinopathies. Sickle cell heterozygotes, Biochem. Biophys. Res. Commun. 43:888, 1971. Longmuir, I. S., and Chow, J.: Rapid method for determining effect of agents on oxyhemoglobin dissociation curves, J. Appl. Physiol. 28:343, 1970. Naera, N., Strange, P. E., Boye, E., and Severinghaus, J. W.: pH and molecular CO, components of the Bohr effect in human blood, Stand. J. Clin. Lab. Invest. l&96, 1966. Scheuer, J.: Myocardial metabolism in cardiac hypoxia, Am. J. Cardiol. 19:385, 1967. Brachfeld, N.: Maintenance of cell viability, Circulation 39 and 4O(Suppl. 4):202, 1969. Katz, A.M.: Effects of interrupted coronary flow upon myocardial metabolism and contractility, Progr. Cardiovast. Dia. 10:450, 1968. Brachfeld, N., and Gemba, R.: Mechanisms of myocardial cell death: Release of lysosomal hydrolases after iachemia, Clin. Res. 13:524, 1965. Williamson, J. R., Schaffer, S. W., Ford, C., and Safer, B.: Contribution of tissue acidosis to ischemic injury in the perfused rat heart, Circulation 53(Suppl. 1):3, 1976. Halpert, P., Fleishman, R. G., Keupe, D., et al.: The Bohr effect related to blood and erythrocyte pH, Am. J. Physiol. 205:337, 1963.
197
of intramyocardial by angiographic
oxyhemoglobin contrast media
David S. Sheps, M.D. Bruce F. Cameron, M.D., Ph.D.* Stephen M. Mallon, M.D. Leonard S. Sommer, M.D. William C. Lo, A.S. Donald R. Harkness, M.D. Robert J. Myerburg, M.D. Miami, Fla.
Several potentially deleterious effects of contrast material have been described in the past decade.‘-” These have included effects of the injection of a hyperviscous and hypertonic solution on the size and shape of red cells, certain hemodynamic and electrocardiographic changes, a tendency to acidosis, and a depression of blood calcium levels. The production of acidosis by’ the injection of water soluble contrast materials has been clearly demonstrated.‘. 3. 3.R. 9. I0 However, the significance of this finding upon oxygen delivery by red blood cells has been questioned.” When oxygen delivery is described in terms of P50, that value is expressed either as P50 at pH 7.4 or P50 in vivo. Usually plasma pH adequately reflects the intrared blood cell pH throughout the physiologic range. However, angiographic contrast medium has been shown to alter the red blood cell pH gradient. Therefore, in this situation, plasma does not reflect intra-red blood cell pH. Previous workers have measured intra-red blood cell pH after the addition of contrast medium with differing results.“. I” From the Divisions Medicine, University laou Cancer Research
of Cardiology and Hematology, of Miami School of Medicine, Institute, Miami, Fla.
Supported
by Florida
Received
for publication
Heart Sept:
Awxiation
Accepted
for publication
Dec. 27, 1978.
Grant
No. 75 AG 213.
25, 1978.
Reprint requests: David S. Sheps, M.D., Associate cine, Division of Cardiology, School of Medicine, North Carolina at Chapel Hill, 349 Clinical Science Hill, N. C. 27514. *Dr. Cameron Association.
OOO2-8703/80/020193
is an Established
Department of and the Papanico-
Investigator
+ 05$00.50/O
0 1980
of the
The
Professor of MediThe University of Bldg. 229H Chapel American
Heart
C. V. Mosby
Co.
The purpose of this study was to examine the effects of contrast medium in an experimental system where extracellular pH was kept constant using a highly buffered red blood cell solution. Thus, all P5O’s were measured under the same conditions (pH 7.4, PCO, 40, and temperature 37” C.) and any changes seen would therefore directly reflect changes in intra-red blood cell pH. In addition, the effect of contrast medium on the red cell pH gradient was examined anerobically. It has previously been shown that contrast media do not alter red blood cell 2,3 DPG,” which is the only other known explanation for acute changes in P50 in this system. In addition to the in vitro studies, in vivo studies were performed on blood drawn simultaneously from the coronary sinus and peripheral arterial system prior to, and one minute and five minutes after selective injection of the left coronary artery with contrast material. Methods In vitro studies. Blood was drawn from the antecubital vein of normal volunteers into tubes containing sodium heparin. Methylglucamine 3,5diacetamido-2,4,6-triiodobenzoate, 66% aqueous solution (Renografin 76) was added to blood in concentrations varying from .02 to .O&.c./c.c. blood, and incubated for a constant time interval prior to measurement of P50. The effect of variation of incubation time from one minute to 30 minutes was evaluated at a Renografin concentration of .O~C.C./C.C.blood.
American Heart Journal
193
Sheps
et
al.
I
*Oh O_r
II
I/L
10 20
30
2. Effect of variation of incubation time on P50 with a constant concentration of 0.06 ml. Renografin/ml. blood. P5O’s are expressed as percentage change from control (without Renografin). Fig.
1. P50 after incubation with Renografin at various concentrations as shown. All samples were incubated at a constant time interval of 30 minutes. Results are expressed as percentage of control values (without Renografin). Fig.
I. Red blood cell pH gradients (Plasma pH-Intraerythrocyte pH) in the control state and after 30 minutes of incubation with Renografin .06 c.c./c.c. blood
Table
Control
Renografin
0.24 0.20 0.20 0.21 0.20 0.20 0.20 0.207 0.015
0.07 0.05 0.08 0.05 0.06 -0.03 -0.02 0.037 0.044
Blood hemoglobin was measured with an IL 182 cooximeter. Blood oxygen dissociation curves were obtained by a modification” of the method of Longmuir and Chow.” The curve was measured at PCO, 40, pH 7.4, and 37” C. on whole cell suspensions in 0.16 M sodium phosphate buffer in a 30 C.C.closed cell. Buffers and blood samples were thoroughly equilibrated with a gas mixture containing 19.6% oxygen prior to introduction into the chamber. The cell suspensions were deoxygenated by beef heart mitochondrial succinate respiration (without CO, production) and the PO, was measured with a membrane type oxygen electrode (YSI, model 53 oxygen monitor). The oxygen signal was continuously recorded on a Kip and Zonen BD 9 recorder. All curves were measured in duplicate, and duplicate determinations on the same sample agreed to within + 0.25 mm. Hg.
194
IN
5”
TIM:01 INO~OATION IN MINUTES
RENOGARFIN CONTENT (ml/mlMood)
Mean Std dev T = 11.02 P < .OOOl
I
Red cell and plasma pH’s were measured using an IL 213 blood gas analyzer at 37” C. The red cell lysate was obtained by the freeze-thaw technique.‘!’ PH gradients were therefore obtained across the red cell membrane in the control state, and after incubation with Renografin for 30 minutes (.06 C.C. Renografin/c.c. blood) at 37” c. In vivo studies. Eleven adult patients who were undergoing cardiac catheterization and selective coronary arteriography were studied. Arterial catheters were introduced percutaneously through the femoral artery and venous catheters via a cutdown into the basilic vein. The venous catheter was positioned in the proximal coronary sinus. The position was verified by a combination of the fluoroscopic location and by the low oxygen saturation. In eight patients, studies were performed approximately ten minutes after left ventriculography. In three patients, studies were performed prior to left ventriculography. Prior to the first coronary injection, control samples were obtained from the proximal coronary sinus and the central aorta. Contrast material was then selectively injected into the left coronary artery (approximately 6 to 12 ml. over 3 to 4 seconds). One minute and five minutes after injection, repeat blood samples were obtained from the proximal coronary sinus and the central aorta. Blood samples were cooled on ice, and oxyhemoglobin dissociation curves and P50 were determined in duplicate within twelve hours. Results
The effects of Renografin on whole blood P50 in concentrations (as outlined above) which would be attained during cardiac catheterization were studied on blood samples drawn from eight Effect of Renografin
on blood
Fehntnry,
P50 in vitro.
1980, Vol. 99, No. 2
Myocardial
oxyhemoglobin
dissociation
II. Differences in P50 between coronary sinus and aorta before and after left coronary arteriography
Table
Control cs
Ao
29.86 28.08 26.63 27.43 26.11 25.56 25.78 28.93 27.30 k 1.56 SEM .55
28.58 26.62 28.53 26.28 25.56 25.78 28.57 27.13? 1.37 SEM .52
*Significant, p < 0.01. Abbreviations: CS = coronary
A (CS-Ao) -.50 .Ol -1.10 -.17 0 0 .36 -.20, .47 SEM .18
CS
Ao
28.46 26.77 25.92 28.84 25.77 22.56 25.30 28.57 26.52 k 2.12 SEM .75
29.71 29.23 30.40 26.44 22.83 26.90 28.21 27.67 i 2.58 SEM .97
sinus; Ao = aorta, A = difference
Heart
Journal
A (CS-Ao)
of aorta from coronary
patients. For this series of experiments, all blood samples were incubated with Renografin at a constant time interval of 30 minutes. The average blood Renografin concentration attained during angiography was estimated at .02 to .04 C.C. Renografin/c.c. blood. This is based on an average total dose of 100 to 200 c+c. of contrast at an average blood volume of 5 liters. Concentration added in vitro ranged from .02 to .08 C.C.Renografin/c.c. blood in all eight patients. The results are depicted in Fig. 1 as percentage decrease at each concentration when compared to the control P50. As shown in Fig. 1, the P50 progressively decreased throughout the range of concentrations studied. In two patients in whom higher concentrations were studied, P50 decreased even further. The changes from control values were significant (p < .Ol) by Student’s t test for Renografin concentration up to .08 m1Jc.c. blood. The effect of the time of incubation of Renografin with blood on P50 was studied at a dose of .06 C.C. Renografin/c.c. blood. The time of incubation refers to the time interval prior to introduction of the blood sample into the closed cell. Results of variation of incubation time are shown in Fig. 2. In both patients studied, a significant decrease in P50 was seen at one minute incubation. This remained constant up to ten minutes of incubation, beyond which point there were further decreases at 15,20, and 30 minutes of incubation. Although the absolute decrease at one minute was only 3 to 5% of the control value, this represented a change of .7 mm. Hg which
American
5 Minute
1 Minute
-1.25 -2.46 -1.56 -.67 -.27 -1.60 .36 -1.06* k .94 SEM .36
cs
Ao
29.08 26.28 26.91 26.19 26.27 23.11 25.23 29.11 26.52 t 1.96 SEM .69
29.71 28.25 27.19 27.12 26.61 23.11 25.51 29.11 27.07 t 2.10 SEM .74
sinus; SEM = standard
A(CS-Ao) -.63 -1.97 .28 -.93 -.34 0 -.28 0 -.55 t 65 SEM .23
~~~~ of the mean.
is well beyond our range on the same blood sample
of reproducibility (i.e., i 0.25 mm.
W. The effects of Renografin .06 c.c.1c.c. blood on the red blood cell transmembrane pH gradient were studied in vitro in seven normal subjects. The differences between plasma and intraerythrocytic pH were compared in the control state and after 30 minutes of incubation with Renografin. The addition of Renografin decreased the plasma pH and the difference between plasma and intraerythrocytic pH (Table I). The mean pH gradient was 0.21 + .Ol prior to the addition of Renografin. The gradient after incubation with Renografin was .04 +- .04, p < .OOOl. In vivo effects of Renografin. Control samples were simultaneously obtained from the proximal coronary sinus and central aorta, and repeat samples were obtained at one minute and five minutes following injection of the left coronary artery in the 11 patients studied. In eight patients these determinations were performed after left ventriculography, and in three they were performed prior to left ventriculography. The results in the initial group of eight patients are shown in Table II. There is no significant difference between P5O’s from coronary sinus or aorta in the control period. At one minute after left coronary injection, the decrease of coronary sinus as compared to aortic P50 is significant (p < .Ol Student’s t test). This difference is reduced by five minutes post-injection when values approach the control state.
195
Sheps
et al.
When the coronary arteries were injected prior to left ventriculography there was no difference between simultaneous coronary sinus or aortic samples prior to injection, or one minute or five minutes after injection. Discussion
Intravascular injection of radiographic contrast material results in a complex series of potentially deleterious effects. Most of these effects have been attribued to the contrast material’s hypertonicity and high viscosity. A lowering of ionized calcium levels has been described secondary to angiographic contrast material which may be implicated in cases of hypotension secondary to contrast injection.’ Initially, the acidosis secondary to contrast material was thought to affect oxyhemoglobin dissociation,’ but recently it has been stated that there is no effect on oxyhemoglobin dissociation since intra-red blood cell pH is not affected by angiographic contrast media. Instead, it was stated, contrast causes an extrusion of hydrogen ions from the red cell.” The results of this study are in agreement with that of Lichtman and associates,!’ referred to above. The decreased P50 seen in our in vitro and in vivo studies secondary to contrast material is explained as follows: The contrast medium (Renografin 76) is a salt of an impenetrable anion, and by balancing negative ions within the red cell alters the transmembrane ionic charge gradient (seeTable I). When the red cell interior is strongly buffered with respect to the suspending medium,” the result is a relative acidification of the medium without change in intracellular pH; when the suspending medium is strongly buffered, as in our studies, the reduction of the pH gradient will result in an increase in intracellular pH. The P50 of the blood then decreasesdue to the Bohr effect’,’ when compared to the same blood P50 prior to addition of contrast medium with an intra-red blood cell pH of 7.2. We and others have shown that this effect is both dosageand time-dependent.’ The exact situation in vivo is not known and is probably dependent upon blood tlow and relative buffering capacity of intra- and extra-red blood cell spaces. The equilibrium studies of Lichtman and associates” are at one extreme where the entire pH change is extracellular. The red blood cell suspension system that we have examined is
196
at the other extreme where the entire change is intracellular. The actual situation in vivo would depend on the relative buffering capacity of in traand extra-red blood cell spaces. In areas of rapid blood flow, the changes described are of little consequence since the dye is rapidly diluted. However, in areas of myocardium distal to a critical coronary lesion, these effects may take on more significance. This is theoretically possible for two reasons. First, the stagnation of blood tlow would allow tissues to be exposed to the effects of the contrast media for a longer time period. Second, the chronically ischemic tissue bed experiences a shift to anerobic metabolism with an increase in glucose consumption, lactate production, a decrease in pH, and ion shifts.“-“* If ischemia is severe enough, there may be a release of cardiac lysosomal enzymes’; which may impair transport functions of cell membranes. This would lessen the metabolic differences between intracellular and extracellular spaces. The increased total CO, produced by ischemia’” would offer a better buffering capacity than normal tissue at normal rates of blood flow. These conditions would favor the kind of changes in P50 seen in our study done in a highly buffered red blood cell solution. The magnitude of these effects in vivo is unknown. In this regard, Caulfield, and colleagues,’ using a protocol similar to ours, found that the effect of Renografin on ionized calcium was of a greater magnitude and duration in patients with coronary artery disease than in normals. When the normal sequence of cardiac angiography was reversed (i.e., coronary arteriography performed prior to left ventriculography), no effect on P50 was detected one minute or five minutes after the injection of the left coronary artery. This suggests that the effects are additive and dose-related, as seen in our in vitro studies. The ultimate effects of contrast medium on oxyhemoglobin dissociation are complex and dependent upon dosage and blood flow, but the direction of change in P50 is probably most influenced by the buffering capacity of the ambient tissue. Summary
The effect of the addition of radiographic contrast material (Renografin) to blood on the oxyhemoglobin dissociation curve and P50 was measured by a metabolic deoxygenation tech-
February,
1980, Vol. 99, No. 2
Myocardial
nique in a strongly buffered red cell suspension. With incubation time constant, increasing doses produced progressive decreases in P50. With incubation time varied at a constant dose, a decrease in P50 was seen after only one minute. In addition, in vivo studies were performed on 11 patients undergoing cardiac catheterization. Simultaneous proximal coronary sinus and aortic samples were drawn as controls, and then at one minute and five minutes after injection of the left coronary artery. In eight patients studies were performed after, and in three prior to left ventriculography. At one minute after left coronary injection there was a significant decrease of coronary sinus as compared to aortic P50 (p < .lO) (only when left ventriculography was performed prior to coronary arteriography). The magnitude of these effects in vivo is unknown, but they would be expected to be more severe in areas distal to a critical coronary lesion due to stasis of blood flow and ischemic metabolic changes.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14. REFERENCES 1.
2.
3.
4.
15.
Braunwald, E., and Swan, H. J. C., ed.: Cooperative study on cardiac catheterization, Circulation 37(Suppl. 3):81, 1968. Lachlan, M.: Biochemical and other changes occurring in infants during angiography, Proc. R. Sot. Med. 63:46, 1970. Rosenthal, A., Litwin, B. S., and Laver, M. B.: Effect of contrast media used in angiocardiography on hemoglobin-oxygen equilibrium, Invest. Radiol. 8:191, 1973. Friesinger, G. C., Schaffer, J., Criley, M., Gaertner, R. A., and Ross, R. S.: Hemodynamic consequences of the injection of radiopaque material, Circulation 31:730, 1965.
American
Heart
Journal
16.
17.
18.
19.
oxyhemoglobin
dissociation
Levin, A. R., Grossman, H., Schubert, E. T., Winchester, P., and Gilladoga, A.: Effect of angiocardiography on fluid and electrolyte balance, Am. J. Roentgenol. 105:777,1969. Marshall, M., and Henderson, G. A.: Tendency to acidosis following injection of radio opaque contrast material, Br. J. Radiol. 41:190, 1968. Berg, G. R., Hutter, A. M., and Pfister, R. C.: Electrocardiographic abnormalities associated with intravenous urography, N. Eng. J. Med. 28987, 1973. Caulfield, J. B., Zir, L., and Harthorne, W. J.: Blood calcium levels in the presence of arteriographic contrast material, Circulation 52:119, 1975. Lichtman. M. A.. Murahv. M. S.. Whitbeck. A. A.. Poaal. M., and Lipchik, E. 0.: Acidification of plasma by the yed cell due to radiographic contrast materials, Circulation 52:943, 1975. Rosenthal, A., and Mesrobian, A.: The relationship between angiography, intraerythrocytic pH and hemoglobin equilibrium, Invest. Radiol. 10:140, 1975. Cameron, B. F.: Biphasic blood oxygen dissociation curves in hemoglobin S hemoglobinopathies. Sickle cell heterozygotes, Biochem. Biophys. Res. Commun. 43:888, 1971. Longmuir, I. S., and Chow, J.: Rapid method for determining effect of agents on oxyhemoglobin dissociation curves, J. Appl. Physiol. 28:343, 1970. Naera, N., Strange, P. E., Boye, E., and Severinghaus, J. W.: pH and molecular CO, components of the Bohr effect in human blood, Stand. J. Clin. Lab. Invest. l&96, 1966. Scheuer, J.: Myocardial metabolism in cardiac hypoxia, Am. J. Cardiol. 19:385, 1967. Brachfeld, N.: Maintenance of cell viability, Circulation 39 and 4O(Suppl. 4):202, 1969. Katz, A.M.: Effects of interrupted coronary flow upon myocardial metabolism and contractility, Progr. Cardiovast. Dia. 10:450, 1968. Brachfeld, N., and Gemba, R.: Mechanisms of myocardial cell death: Release of lysosomal hydrolases after iachemia, Clin. Res. 13:524, 1965. Williamson, J. R., Schaffer, S. W., Ford, C., and Safer, B.: Contribution of tissue acidosis to ischemic injury in the perfused rat heart, Circulation 53(Suppl. 1):3, 1976. Halpert, P., Fleishman, R. G., Keupe, D., et al.: The Bohr effect related to blood and erythrocyte pH, Am. J. Physiol. 205:337, 1963.
197