RELATIONSHIP OF MUSCLE STRENGTH TO POTASSIUM CONCENTRATION IN A HYPOKALEMIC INFANT

A nine-month infant, weighing 9.8 kg, presented with hypotonin seconda ry to acute hypokalaemia (1.0 mmol/l). Muscle strength improved as the serum potassium was increased. Muscle strength was assessed by the pr essure generated inside a saline-filled endotracheal tube cuff during a grasp reflex. Potassium concentration and hand grip strength were re lated wing a sigmoidal Emax model, Zero, effect was assumed when the p otassium concentration was zero. The Emax, EC50 and Hill coefficient v alues were determined by non-linear regression using the MKMODEL progr am. Parameter estimates (SE) were EC50 1.79 (0.15) mmol/l, Hill coeffi cient 3.79 (0.92), Emax 114.4 (8.9) mmHg.