T. K. Oliver, Jr., M.D., G. A. Young, M.D., G. D. Bates, B.S.,
and
J. S. AdamoFrom the Departments of Pediatrics, University of Wa.shington, Seattle, Washington
and The Ohio State University, Columbus, Ohio
(Submitted February 1; accepted for publication May 31, 1966.)
This investigation was supported by a U.S. Public Health Service Research Grant (HD 00747) from the National Institute of Child Health and Human Development.
ADDRESS: (T.K.O.) Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington 98105.
PEDIATRICS, Vol. 38, No. 5, November 1966
FACTITIAL
HYPERKALEMIA
DUE
TO
ICING
BEFORE
ANALYSIS
RECENT REPORT by Acharya and Payne1 of a high plasma potassium concen-tration at birth and for 48 hours thereafter in normal full-term infants prompts this communication because their results, like those we reported in 1961,2 are quite
cer-tainly in error.
In addition to these two studies, Wid-dowson and McCance3 have also reported high values (8.0 mEq/l on higher) at birth
while other investigators47 have reported lower values (4.6-5.1 mEq/l). The analysis
of plasma electrolytes in our study was a by-product of an investigation primarily di-rected at the determination of blood gas tensions serially during the first hour of life. Because the tension method was time consuming,8 samples of hepaninized whole blood were kept in crushed ice for up to 6 hours prior to centrifugation and
separa-tion of plasma for further analyses. We had determined that no significant changes oc-curred in pH, CO2 content, or glucose con-centration during that period. Although an increase in plasma potassium is well-known
during storage of blood in a refrigerator
over a period of days, there did not seem to be any evidence that this would occur
acutely. Nonetheless, it was decided to de-termine if icing whole blood would effect plasma potassium concentration.
MATERIALS AND METHODS
Twenty normal term infants all with 1-minute Apgar scores of 8 or more had a catheter passed into the umbilical artery within 2 minutes of age. Five 1 ml samples were collected in lightly oiled, hepaninized syringes (exactly as in the previous studyl)
and capped with a mercury bead to assure
even mixing. One sample was immediately
centrifuged and the plasma decanted; an-other was forcibly ejected through a 23 gauge needle into a test tube, then
immedi-ately centrifuged to study the effects of hemolysis; the remaining syringes were
placed in crushed ice and kept there for 1, 3, and 5 hours, at which time the blood was centrifuged and the plasma decanted. In order to avoid a systematic error, the order of collection was randomized. In 12 healthy adult males, free-flowing venous blood was
collected in a hepaninized syringe and all-quots were injected into test tubes. All-quots were centrifuged immediately or after storage in crushed ice for 1, 3, and 5
hours. In a subsequent study in five adult males, 10 ml of hepannized venous blood
was collected and immediately centrifuged, 1 ml plasma was decanted (to increase packed red cell volume), and the blood was resuspended; aliquots were then handled as
above.
Plasma potassium was determined on all samples and packed red cell volume on those from most newborn infants and all five adults in the later study. Potassium
concentration was measured by a standard flame photometric method.9 Plasma hemo-globin was determined by a modification of the benzidine method.1#{176} Packed red cell volume was determined with a
micro-he-matocnit centrifuge, the sample being spun for 4 minutes at 11,000 rpm. All determina-tions were performed in duplicate.
Newborn vs. Adult
RESULTS
-. infants
.-.. “polycythemic” adults
8
-1
1)
0
0
a
Time on ice - hours
8
.--. infants adults
a i
Time on ice-hours
Fic. 1. The effect on potassium concentration of
icing infant and adult whole blood. The bars
in-ARTICLES 901
newborns was 4.81 ± S.E. 0.15 mEq/l. When the blood was kept on ice the plasma potassium rose promptly and significantly; the value at 5 hours was 7.02 ± S.E. 0.21, a
mean increase of 2.2 mEq/l (Fig. 1). The immediate mean concentration of plasma potassium for adults was 4.56 ± S.E. 0.11
mEq/l and nose more slowly (significantly only after 3 and 5 hours) to a peak mean value of 5.87 ± S.E. 0.18, an increase of 1.3 mEq/1. There was no significant difference
in mean potassium concentrations of freshly separated newborn on adult plasma (p>
0.10), but there were highly significant dif-fenences (p < 0.001) at 1, 3, and 5 hours.
Newborn vs. “Polycythemic” Adults
Although the packed cell volume was not measured in the 12 adults in the first part
of this study, the possibility that the
ob-served differences in potassium concentra-lion could be attributed to the higher packed
cell volume of neonates was investigated by removing some plasma, then neconstitut-ing the blood from adults. The resulting mean packed cell volume was 53.8 and did not differ significantly from the newborn’s hematocrit, 51.5 ± S. E. 0.38.
As can be seen in Figure 2, increasing the
packed cell volume of adult blood
corn-Fic. 2. The effect on potassium concentration of
icing infant and “polycythemic” adult blood. The
bars indicate 1 S.D.
pletely obliterated the previously observed
differences in plasma potassium concentra-tion.
Effect of Hemolysis
Plasma hemoglobin concentration was determined on 82 samples. The values ranged between 3 and 94 mg/100 ml, with a mean of 20.9 mg/100 ml. (Normal for the method is up to 5.0 mgIlOO ml.) No correla-tion existed between these values and potas-sium concentration, indicating that this
de-gree of hemolysis does not affect plasma potassium concentration, although more in-tense hemolysis surely does.
COMMENT
These results clearly show that when whole blood is stored on ice there is a prompt rise in plasma potassium concentra-tion. Although many investigators have ob-served a rise when blood is refnigerated,h1.15
the rate at which this occurs has not been fully appreciated. The only report
indicat-ing that this might occur rapidly-which we found only in a hind-sight literature
search-5 is that of Goodman, et al.16 who observed a
mean increase of 1.2 mEq/l when clotted
blood was stored in ice for 6 hours in
902 FACTITIAL HYPERKALEMIA
of 1.3 mEq/l over a 5-hour period in the
adults we studied.
These studies were not designed to eluci-date the mechanisms involved in the pre-vention of sodium and potassium shifts in
the direction of their concentration gra-dients, but they serve to confirm the obser-vations made more than 20 years ago that
this is a function of glycolysis.u
The important lesson is that chemical
analyses should be performed soon after blood collection; if this is not possible, it is critical that the blood sample be handled
appropriately. Icing allows one to delay analyses of acid-base chemistries and
glu-cose, but this is entirely inappropriate for
potassium analysis. For this, the plasma (or
serum) should be separated as soon as pos-sible. It was clear from this study that the
effects of icing were independent of me-chanical hemolysis. Correct handling of blood samples should prevent both these
potential sources of factitial elevation in
potassium concentration.
SUMMARY
Both adult and newborn blood plasma
potassium concentration rose significantly
when whole blood was kept on ice for
pen-ods of 5 hours. This appears to be due to inhibition of red cell glycolysis. The rise in
plasma potassium concentration of blood
from newborn infants is significantly great-en than that occurring in blood from adults; this difference is a function of the neonate’s
increased ned cell volume. Meaningful
in-terpretation of potassium concentration, particularly in the newly born, demands that the plasma be separated immediately.
The plasma potassium concentration of
normal newborns at birth does not differ
significantly from adults; in this study the
mean value in 20 infants was 4.81 mEq/l.
REFERENCES
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first 48 hours of life. Arch. Dis. Child., 40: 430, 1965.
2. Oliver, T. K., Jr., Demis, J. A., and Bates,
G. D. : Serial blood-gas tension and acid-base balance (luring the first hour of life in human iIlfaIltS. Acta Paediat. (Scand.), 50:
346, 1961.
:3. \Viddosoi. E. M., and McCance, B. A. : The effect of development on the composition
of the serum and extracellular fluids. Clin.
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4. James, L. S.: Acidosis of the newborn and its
relation to birth asphyxia. Acta Paediat.
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5. Reardon, H. : In Adaptation to Extra-uterine
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Columbus: Ross Laboratories, p. 79, 1959.
6. Earle, D. P., Bakwin, H., and Hirsch, D.: Plasma potassium level in the newborn. Proc. Soc. Exper. Biol. Med.. 77:756, 1951. 7. Smith, C. A. : Physiology of the Newborn In-fant, ed. 3. Springfield, Illinois: Charles C
Thomas, 1959.
8. Bates, C. D., and Oliver, T. K., Jr. : A
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J. Appl. Physiol., 17:743, 1962.
9. Meites, S., and Faulkner, W. R. : Manual of
Practical Micro and General Procedures in
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Charles C Thomas, 1962.
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11. Harris, J. E. : The influence of the
metab-olism of human erythrocytes on their potas-sium content. J. Biol. Chem., 141:579, 1941. 12. Scudder, J., Drew, C. R., Corcoran, D. R., and
Bull, D. C. : Studies in blood preservation.
I. Repartition of potassium in cells and
plas-ma J.A.M.A., 112:2263, 1939.
13. Downman. C. B. B., Oliver, J. 0., and Young,
I. NI.: Partition of potassium in stored blood. Brit. Med. J., 1 :559, 1940.
14. Danowski, T. S. : The transfer of potassium
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15. Ponder, E. : Anomalous features of the loss of
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