Potassium is an essential mineral, accounting for the majority of the positive charge within cells. An excess of potassium in the blood is known as hyperkalemia. In the hospital setting, clinicians monitor potassium levels very carefully due to the potentially deadly effects of hyperkalemia. One of the most serious effects of excess potassium is is its effect on the electrical conduction system of the heart.
Normal Potassium Levels in Infants
Normal blood values of potassium in adults are much lower than those present in infants. While the normal adult range of potassium is 3.5 to 5.0 millimoles per liter or mmol/L, the range in newborns is 3.7 to 5.9 mmol/L and for infants up to one year 4.1 to 5.3 mmol/L, according to "The Johns Hopkins Hospital: The Harriet Lane Handbook for Pediatric Officers."
Potassium and the Heart
The resting phase of the heart is conducted by the flow of potassium ions out of the myocardial cells. According to the book "Rapid Interpretation of EKGs", this phase is known as the repolarisation phase. In situations of hyperkalemia, the main pacemaker of the heart called the sinoatrial node is depressed and the ventricular contraction phase is lengthened. Thus, the heart's pumping capability decreases and arrhythmias or electrical conduction abnormalities occur.
The causes of hyperkalemia in infants are similar to those in adults. Typical causes include kidney failure, decreases in insulin levels, trauma and crush injuries. Renal tubular acidosis, blood drawing in a child causing destruction of blood cells, muscle injuries and medications such as theophylline can also result in hyperkalemia in infants.
Signs and Symptoms
Lethargy and muscle weakness are the most common symptoms of hyperkalemia. Apathy and prickling sensations in the limbs are also common. Tetany occurs in more severe cases. Signs include diarrhoea and abdominal distention, along with electrical conduction defects manifest on electrocardiograms, or EKGs.
In an infant, the treatment depends on the findings on the EKG, according to "The Johns Hopkins Hospital: The Harriet Lane Handbook." If the child has a normal EKG, then potassium is just eliminated from his or her diet and kayexalate, a polystyrene resin that promotes the excretion of potassium in the stool, is given.
If the EKG is abnormal, then intravenous calcium gluconate is given, along with insulin and glucose. Dialysis is recommended for the most severe cases.
- "The Johns Hopkins Hospital: The Harriet Lane Handbook" 17th ed.; Drs. Jason Roberston and Nicole Shilkofski; 2005
- "2007 Current Consult Medicine"; Drs. Maxine Papadakis and Stephen McPhee; 2007
- "Harrison's Principles of Internal Medicine" 17th ed.; Dr. Anthony Fauci, et al., eds.; 2008
- "Rapid Interpretation of EKG's"; Dr. Dale Dubin; 2000
- "Step-Up to Medicine" 2nd ed.; Drs. Steven Agabegi and Elizabeth Agabegi; 2008