Abstract 2281: Changes in Plasma Ionized Calcium and RBC K Content in Severe Hyperkalemia: New Electrocardiographic Concept
Background and Objectives: The ancient concept of ECG changes in hyperkalemia has been challenged by observations in our laboratory suggesting that plasma ionized Ca++ and intracellular K in RBC were the most critical determinants of hyperkalemic-induced ECG changes and arrhythmias. This hypothesis was further tested in a 2nd cohort of patients.
Methods: Group I, includes 25 patients in which our observation was first recorded. Group II, 35 patients with hyperkalemia, in which Ca++ and RBC K content were corrected. In all subjects cardiac monitoring was continuously recorded, while BP, HR, ECG and arterial pH, HCO3, PCO2, plasma (Na, K, Cl, Ca++) and RBC (Na, K, Cl, H2O) were serially recorded.
Results: In group I, 11 patients (44%) exhibited ECG changes reflecting hyperkalemia (K 6.6 ±0.7 mmol/L /l), in presence of metabolic acidosis (pH 7.32 ±0.3), increased RBC K (106 ± 9mmol/l of cell), and decreased Ca++ (0.65 ± 0.01mmol/l); while in 14 others (56%), no ECG changes were recorded despite severe hyperkalemia (7.2 ±1.2 mmol/l, p <0.03), metabolic acidosis (pH 7.34 0.03, p n.s.), but decreased RBC K (86.4 ±5 mmol/l of cell, p <0.001) and higher Ca++ (0.87± 0.03 mmol/l p< 0.002). Nine out of 25 patients (36%) with Ca++≤0.8 mmol/l had ventricular fibrillation or asystolia, and 7 did not survive (28%); while 16 others (64%) with Ca++≥0.9 mmol/l presented no ventricular arrhythmia. In group II (n=35, pH 7.33 ± 0.4) with severe hyperkalemia (K 6.8 ±1.5 mmol/l), the restricted K intake, correction of acidosis and ionized Ca++ values prevented the occurrence of significant ECG changes, ventricular arrhythmias (0%), or death (0%) related to hyperkalemia.
Conclusion: This is the first evidence documenting that the ECG changes and ventricular arrhythmias in hyperkalemia are strictly dependent on plasma Ca++ and RBC K exchange, a finding that might help to prevent and reverse this potentially life-threatening metabolic problem.