True about hyperkalemia -

Classically, the electrocardiographic manifestations in hyperkalemia progress from tall peaked T waves (5.5-6.5 mM), to a loss of P waves (6.5-7.5 mM) to a widened QRS complex (7.0-8.0 mM), and, ultimately, a to a sine wave pattern (>8.0 mM). However, these changes are notoriously insensitive, paicularly in patients with chronic kidney disease or end-stage renal disease. ( ref: harrisons principles of internal medicine, 19E page 310)