Resolution of Left Bundle Branch Block After Calcium Administration in the Prehospital Setting.

Hyperkalemia is a medical emergency with potentially severe consequences that can be avoided by early recognition and effective treatment. Electrocardiogram (ECG) changes can help elucidate hyperkalemia prior to obtaining lab results and assist in early decisions on treatment, especially in the prehospital setting. ECG changes commonly associated with hyperkalemia are peaked T-waves, PR prolongation, P-wave flattening, QRS widening, or a sine-wave pattern at severely elevated potassium levels. Bundle branch blocks (BBBs) are associated with hyperkalemia but are less common and less well known in this setting. We report a case of a prehospital ECG showing a left bundle branch block (LBBB) in a patient who had end-stage renal disease, and the prehospital treatment with calcium chloride lead to resolution of the LBBB. The patient was eventually found to have a serum potassium level of 6.1 mEq/L.