From the Departments of Biochemistry and Medicine, Medical-Dental Schools of Alabama, Birmingham, Alabama

Transcription

1 SERUM SODIUM AND VALUES IN FOUR HUNDRED NORMAL HUMAN SUBJECTS, DETERMINED BY THE BECKMAN FLAME PHOTOMETER* HOWARD C. ELLIOTT, JR., B.S., AND HOWARD L. HOLLEY, M.D. From the Departments of Biochemistry and Medicine, Medical-Dental Schools of Alabama, Birmingham, Alabama Recently, there have been several publications 5,7 regarding the use of the Beckman Flame Photometer for the quantitative determinations of sodium and potassium in biological material. This report is concerned with statistical studies of sodium and potassium values in normal human subjects, together with a correlation of these findings with those of other workers. Four hundred serum samples from normal subjects were examined by the technic described by Mosher. 5 PROCEDURE The normal samples were obtained from fasting volunteers at the blood bank of the Jefferson-Hillman Hospital, who were fairly evenly distributed in sex and age. The blood was collected in plastic tubes, allowed to clot and centrifuged immediately to prevent any shift in the electrolyte equilibrium between cells and serum. It was decided to use serum obtained from clotted blood in place of plasma because of the difficulty in obtaining heparinized blood in a charity hospital, and the possibility of contamination with sodium or potassium if oxalates were used. The macro technic described by Mosher 5 was used with the exception of the following change. The stock standard was prepared to contain 145 meq. of sodium and 5.0 meq. of potassium per liter, and, 1.0 and ml. of this solution were transferred by a microburet into 50-ml. volumetric flasks to form the low, middle and high standards. Within the limits set by these standard solutions the transmission-concentration relationship is linear. This makes possible calculation of results by simple proportionality. If a sample did not fall within the limits of the above standards another serum dilution was made and the determination repeated. Duplicate determinations were made, and the average of two readings on each determination was taken as the correct reading. The experimental error of the technic was studied, using the following procedure. Five samples of pooled serum were placed in separate tubes and placed with five clinical samples. These were numbered by a disinterested person and then given to the analyst, who thus had no idea what the samples were. This completely eliminated the psychological * A portion of this material has been extracted from the thesis of Howard C. Elliott, Jr., presented in partial fulfillment for the degree of Master of Science, Medical College of Alabama, Birmingham, Alabama. This study was supported in part by a grant from Lakeside Laboratories, Inc., Milwaukee, Wisconsin. Received for publication, May 21,

2 832 ELLIOTT AND HOLLEY effect of doing repeated determinations on the same sample. Table 1 is typical of a series of these studies, and shows the reproducibility of the technic when performed by an experienced technician. A number of sodium and potassium determinations were made, using both the flame photometric technic and established methods of chemical analysis. 3 ' 5 ' 8 The results are indicated in Table 2. TABLE 1 ANALYSIS OF POOLED SERUMS SAMPLE SODIUM AV. AV. la lb Ic Id Ie % of m % of av Average TABLE 2 COMPARISON OF VALUES OF SODIUM AND IN SERUM BY CHEMICAL AND FLAME PHOTOMETRIC ANALYSIS SAMPLE Chem. SOD I T J M Fl. Ph. Chem. l"i. Ph. mej./l S S RESULTS OF THE NORMAL DETERMINATIONS The distribution curves (Figures 1 and 2) for both sodium and potassium compare well with hypothetical "normal" distribution curves. In the 400 sodium determinations shown in Figure 1 the range is from to 155.0, with an average value of The standard deviation is 3.81, and the coefficient of variation is 2.6 per cent. Two hundred and eighty determinations, or percent of the sodium values, fall within the mean ± the standard deviation. The 400 potassium determinations shown in Figure 2 indicate a distribution very slightly skewed to the right. The range of the potassium

3 SERUM SODIUM AND 833 determinations is from 3.1 to 5.5, with an average of 4.18 The standard deviation is 0.43, and the coefficient of variation is.10.3 per cent. Two hundred and seventy-four, or 68.5 per cent of the potassium values 80 co co & o20 z I42" " I 152" 3 I54"5 SODIUM meq/l FIG. 1. Distribution of flame photometric determinations of serum sodium in 400 normal persons SUBJECTS fc b z \73B-.940-l 4?:3 44"54.6" ".1 52:35.4:5 meq/l FIG. 2. Distribution of flame photometric determinations of serum potassium in 400 normal persons. fall within the range of the mean ± standard deviation. The ranges covered by one standard deviation in the sodium and potassium determinations are in accordance with Arkin and Colton, 1 who state that per cent of the values should be covered by the mean =fc one standard deviation in a normal distribution curve.

4 834 ELLIOTT AND HOLLEY DISCUSSION The results of the sodium and potassium determinations by both chemical and flame photometric technics, as shown in Table 2, indicate that sodium values are the same within the limits of experimental error by both methods, while lower potassium values are obtained with flame photometric determinations than by chemical analysis. We feel that a greater degree of precision is possible with flame photometric technics, and accept these values. TABLE 3 STATISTICAL ANALYSIS OP DATA OBTAINED BY FLAME PHOTOMETRY SODIUM Average Range Standard deviation Coefficient of variation Average deviation Deviation per cent average SI IS TABLE 4 COMPARISON OF STATISTICAL DATA BY VARIOUS INVESTIGATORS INVESTIGATOR NO. DETNS. AV. RANGE Sodium Smith 5 Marin is 3... Overman 4. Hald (av.) l.s (St.) 3.6 Potassium Smith*... Marinis 3.. Overman 4 Hald S (av.) (St.) Table 3 shows the statistical analysis of the data we have obtained with the Beckman Flame Photometer, and Table 4 is a compilation of the other published statistics ' ' on normal sodium and potassium determination by flame photometry. Smith, and co-workers 7 are the only other investigators who have used the Beckman Flame Photometer and reported values obtained. While our range of. sodium values is somewhat greater, this is to be expected in consideration of the number of samples involved in each case. The average values and deviations compare favorably with Smith and associates, 7 and with Marinis, 4 who used the Perkin-Elmer Flame Photometer. In the potassium values there is

5 SERUM SODIUM AND 835 some deviation in the range compared with other investigators, but, again, the average values and deviations are the same order of magnitude. The potassium values we found would also indicate that the normal values for potassium are below commonly accepted figures as stated by Smith and associates. 7 Possibly the correlation is not as great with Hald 2 and Overman 6 because of the small number of samples they analyzed, and refinements in instruments and technics since their work was published. The statistical study of the data by separation into sexes, age groups, and race showed no significant deviation, and is not included in this study. SUMMARY It has been shown that the technic of Mosher 1 is reproducible, and values obtained are in agreement with other investigators, 2 ' 4 ' 6 ' 7 using flame photometric technics. The average value for sodium is in agreement with values reported by previous workers. The average value for potassium falls significantly below that reported by previous workers, but is in agreement with Smith. 7 REFERENCES 1. ARKIN, H., AND COLTON, R. R.: An Outline of Statistical Methods, Ed. 4. New York: Barnes and Noble, Inc., p. 3S. 2. HALD, P. M.: The flame photometer for the measurement of sodium and potassium in biological fluids. J. Biol. Chem., 167: , LOON BY, J. M., AND DYER, C. G.: A photoelectric method for the determination of potassium in blood serum. J. Lab. and Clin. Med., 28: 355, MAKINIS, T. P., MUIRHEAD, E. E., JONES, F., AND HILL, J. M.: Sodium and potassium determinations in health and disease. J. Lab. and Clin. Med., 32: , MOSHER, R. E., BOYLE, A. J., BIRD, E. J., JACOBSON, S. D., BATCHELOR, T. M., ISKRI, L.T., AND MYERS, G. B.: The use of flame photometry for the quantitative determination of sodium and potassium in urine. Am. J. Clin. Path., 19: 461-4, OVERMAN, R. R., AND DAVIS, A. K.: The application of flame photometry to sodium and potassium determinations in biological fluids. J. Biol. Chem., 168: , SMITH, R. G., CRAIG, P., BIRD, ID. J., BOYLE, A., ISERI, L. T., JACOBSON, S. D., AND MYERS, G. B.: Spectrochemical values for sodium, potassium, iron, magnesium and calcium in normal human plasma. Am. J. Clin. Path., 20: , S. WEINBACH, A. P.: A micromethod for the determination of sodium. J. Biol. Chem., 110: 95, 1935.