Propranolol treatment was recently reported to be successful for the management 
of severe infantile hemangioma. Known adverse effects of propranolol treatment 
include transient bradycardia, hypotension, hypoglycemia, and bronchospasm (in 
patients with underlying spastic respiratory illnesses), which led to a general 
recommendation to gradually increase propranolol dosage and closely monitor 
patients' hemodynamics at the onset of therapy. To date, no serious or 
unexpected adverse effects that required specific intervention have been 
reported. In this report, we describe the case of a 17-week-old female preterm 
infant who presented with a large, ulcerated, cutaneous-subcutaneous hemangioma 
of the right lateral thoracic wall, which we treated successfully with 
propranolol. A few days into therapy, a potentially life-threatening adverse 
effect, severe hyperkalemia, was observed and required treatment with loop 
diuretics, fluids, and nebulized salbutamol to normalize her serum potassium 
levels. This therapy could be gradually tapered and finally discontinued only 
after several weeks of propranolol treatment. Our case report indicates that, at 
least during the initial phase of the propranolol treatment of infantile 
hemangioma, close monitoring of serum electrolytes, besides the monitoring of 
hemodynamics and blood glucose, is necessary.