In this VETgirl online veterinary continuing education blog, we demonstrate how to treat the critically ill, emergent hyperkalemic blocked cat (e.g., feline urethral obstruction). Life-saving therapy should be implemented immediately – this doesn’t include the unblocking, per se, but the stabilization of the cardiopulmonary system first. Severe hyperkalemia and metabolic acidosis can result in cardiotoxicity, seen as either bradycardiac or tachycardia. Treatment should include IV access, IV fluid resuscitation, calcium gluconate (to stabilize the heart) and some type of medication to lower the potassium levels (e.g., regular insulin with dextrose or sodium bicarbonate therapy). Continued therapy should include IV fluids, analgesics (e.g., buprenorphine), ECG monitoring, blood pressure monitoring, urine output monitoring (including matching the ins and outs), and supportive care. With treatment, the prognosis is fair to good!