A Quick Overview of Hypokalemic PP
1) Patient has “attacks” of weakness and/or floppy paralysis which have clearly defined beginnings and endings.
2) First attacks occur by the age of 16 in 65% of patients.
3) Attacks follow triggering events (vigorous exercise, intense short-term stress, fright) or a meal high in carbohydrate and/or sodium (baked goods, pizza, Chinese food, sugar-sweetened soda, beer, etc.). Often a first attack occurs in a teenager/young adult who has participated in a sporting event and celebrated afterward with pizza and beer or soda. Attacks also frequently occur after dental work or stitching of minor wounds, triggered by the epinephrine in the local anaesthetic. Heat, stress and chilling are reported triggers in many patients.
4) Attacks usually begin in early morning hours before waking so patient awakens weak/paralyzed.
5) Potassium level in the blood falls in the hours leading up to the attack. In teenagers this fall may be dramatic, even to 1.8 – 2.0 mmol, older patients usually experience less drop from normal. Potassium level normalizes well before strength returns, so the drop in potassium may not always be evident if blood is drawn several hours into the attack or toward its end.
6) Patients do not lose potassium (or other electrolytes) in the urine during paralytic attacks. Low serum levels due to excretion immediately prior to or during attacks suggests another diagnosis. See: Determining the Origin of Hypokalemic Paralysis.
7) Patients should not be started on medication which modifies/ manipulates acid-base balance or potassium levels until a 24-hour urine examination has been conducted to rule out kidney, endocrine and digestive disorders.
8) Older patients may present with gradual onset of fixed muscle weakness (myopathy) without attacks or hypokalemia. A thorough physical exam, family history, genetic and electrodiagnostic testing are key elements to obtaining a correct diagnosis. 9) Older patients may also gradually develop attacks of weakness which last from days to months. They may last long enough to be mistaken for permanent muscle weakness. Muscle strength varies from day to day, or from morning to evening, and responds to treatment, or to more aggressive treatment. These are called Abortive Attacksbecause they never progress to paralysis. These patients may also have paralytic attacks with abortive attacks between.