Hypokalemic Periodic Paralysis
Abstract
Introduction:
The primary focus of this project is to educate individuals on aspects of the unique and rare disease, hypokalemic periodic paralysis (HPP), especially attack triggers and expected pathophysiology behind those. The case presented details a common trigger and presentation of an HPP attack. The monitoring, lab values, and ED course treatment follow the most up to date management of severe hypokalemia coupled with discharge and prophylactic management of HPP as well.
Case description:
A 26-year-old Asian male presented to the Emergency Department with a chief complaint of muscle weakness in the lower extremities, difficulty ambulating, and fatigue. Weakness started around 4 hours prior to arrival at the ED following the patient performing leg exercises at the gym. The patient does report a history of HPP diagnosed at the age of 14. Physical exam showed decreased range of motion and decreased strength of bilateral lower extremities. Decreased deep tendon reflexes also noted. Pertinent lab results showed a potassium level of 1.6mEq/L (normal 3.5- 5.2) and Magnesium level of 2.1mg/dL (normal 1.7- 2.2). ECG was performed and showed sinus bradycardia, first degree AV block, and ventricular S2. Due to the patients known history of HPP further diagnostic testing was not necessary in this case.
Management/ Outcome:
The Patient received 40mEq of oral potassium immediately on arrival to ED. The patient did report he had taken oral potassium over the last several hours. Due to minor improvement in symptoms and the extremely low potassium level an IV drip was also initiated with 40mEq of IV potassium chloride. Labs were redrawn every 2 hours. The patient improved over the course of his ED stay. He regained strength of lower extremities bilaterally and was able to ambulate well without assistance. Prior to discharge patients’ potassium level was normalized at 5.4mEq. Patients at home regimen was adjusted to 20mg of oral potassium chloride, extended release twice daily along with 50mg of spironolactone once daily.
Discussion:
It is important to be able to recognize attack symptoms of HPP and to be educated on the triggers as well. When discussing history of present illness with a patient knowing these clues may help to make a quicker diagnose and faster treatment of the patient. An ECG must be performed initially and monitored over time to check for signs of hypokalemia or any life threatening arrythmias. Signs of QTc prolongation can be present in severe cases and dictate treatment approach. Although the patient in this case did not have any gastrointestinal complaints or abnormalities, providers should be aware of the effect of low potassium on the GI tract leading to decreased peristalsis and the possibility of a paralytic ileus. A detailed history with the patient is a must and an abdominal x-ray is a good consideration as well.
Additionally, it is important to understand the pathophysiology behind the attack triggers to not make mistakes in management. An increase in insulin or epinephrine can cause serum potassium to shift intracellularly leading to low blood potassium which causes muscle cell damage and decreased conduction of skeletal muscle contraction. This leads to the muscle weakness and in severe cases muscle paralysis that is seen with HPP. Understanding this mechanism will help to understand why providers cannot treat an HPP patient with an IV infusion of potassium and dextrose as dextrose is a sugar that can stimulate insulin secretion and lead to further decline in potassium levels. Overall, the patient case depicted throughout this project is a strong example of the course of HPP. The learning objectives aid in a better understanding the history, clinical manifestations, physical exam, diagnosis, and management of HPP.