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Internal potassium shift in premature infants: cause of nonoliguric hyperkalemia
1Department of Neonatology, Fukuoka Children's Hospital and Medical Center for Infectious Diseases, Japan.
Insights
Premature infants experience nonoliguric hyperkalemia due to an internal potassium shift, not intake. This potassium shift is inversely related to gestational and postnatal age, leading to higher serum potassium levels.
Area of Science:
- Neonatal Physiology
- Pediatric Nephrology
- Endocrinology
Background:
- Nonoliguric hyperkalemia is a clinical challenge in premature infants.
- Understanding potassium (K) balance is crucial for managing neonatal metabolic disturbances.
Purpose of the Study:
- To investigate the pathophysiology of nonoliguric hyperkalemia in premature infants.
- To determine the relationship between gestational age, postnatal age, and serum potassium levels.
Main Methods:
- Measured serum potassium, external K balance (intake/excretion), and estimated internal K balance (intracellular to extracellular shift).
- Analyzed data based on gestational age (24-36 weeks) and postnatal age (0-72 hours) in 24 nonoliguric premature infants.
Main Results:
- Serum potassium rose significantly in infants with lower gestational ages (24-32 weeks) within 24 hours.
- External K balance was negative and more pronounced in more premature infants.
- Internal K shift was greater in more premature infants and decreased with postnatal age.
Conclusions:
- An internal potassium shift, inversely proportional to gestational and postnatal age, is the primary cause of nonoliguric hyperkalemia in very premature infants.
- Potassium loading from this shift increases serum potassium and subsequent urinary potassium excretion.
Abstract:
To study the pathophysiology of nonoliguric hyperkalemia, we measured serum potassium concentration and external K balance (intake and excretion), and estimated internal K balance (a shift from intracellular space to extracellular space) in 24 nonoliguric premature infants during the first 72 hours after birth. Data were analyzed from two aspects: gestational age (group 1, 24 to 28 weeks, n = 9; group 2, 29 to 32 weeks, n = 9; group 3, 33 to 36 weeks, n = 6) and postnatal age (0 to 72 hours). Serum K concentration rose from baseline (0 hour) to 24 hours in groups 1 and 2 (p < 0.01) but did not rise in group 3. The external K balance was negative in all groups during the study period, and was more negative in the more premature infants (group 1 > group 2 > group 3) during the second 24 hours. There was a significant difference (p < 0.01) between the internal K balance of the three groups during the first 24 hours (group 1 > group 2 > group 3), and the K shift decreased significantly (p < 0.05) during the study period in groups 1 and 2. The more premature the infants, the larger the K shift and the larger the rise in serum K concentration during the first 24 hours, and the more negative the external K balance after 24 hours. These data indicate that K loading caused by the K shift associated with prematurity produces a rapid rise in serum K concentration, resulting in an increase in urinary K excretion. We conclude that an internal K shift inversely proportional to gestational and postnatal age is the primary cause of nonoliguric hyperkalemia in very premature infants.