A girl presented with severe hyperkalemia and peaked T waves on ECG. Fastest way of shifting potassium intracellularly is aEUR'
Insulin + glucose Tall T waves on ECG indicate cardiac manifestation of hyperkalemia. - Intravenous calcium gluconate is the first drug to be administered in a patient with hyperkalemia having E.C.G. abnormalities. - It stabilizes the myocardium immediately. - It acts within minutes and is characterized by improvement in E.C.G. appearance. But an impoant point to note - It does not affect transcellular movement of potassium. Thus it won't help in reducing the hyperkalemia. Among the agents which cause transcellular (intracellular) movement of potassium. - "Intravenous insulin is the fastest way to lower serum potassium levels". The goals of the therapy for the tit of acute hyperkalemia in chronological order are as follows:? i) Antagonize the affect of IC on excitable cell membranes ii) Redistribution of extracellular potassium into cells iii) Enhance elimination of potassium from the body i) Antagonize the effect of potassium on excitable cell membrane Calcium directly antagonizes the myocardial effect of hyperkalemia. It does so by reducing the threshold potential of cardiac myocytes. Calcium. for injection is available as chloride or gluconate salt. The preferred agent is the gluconate salt since it is less likely than calcium chloride to cause tissue necrosis. The onset of action is < 3 minutes. The duration of action is 30-60 minutes during which time fuher measures may be undeaken to lower p1{. ii) Redistribution of potassium into cells :? Insulin Insulin shifts potassium into cells. Potassium shift inside the cells is mediated by Na+ IC ATPase. I.V. insulin is the fastest way to lower serum potassium levelr2. The onset of action is < 15 minutes and the effect is maximal b/w 30-60 minutes. Dextrose is given along with insulin to prevent hypoglycemia. It was believed that administration of dextrose alone, can cause shift of potassium inside the cells by promoting insulin release. * The administration of hypeonic dextrose alone for hyperkalemia is not recommended for two reasons:- Endogenous insulin levels are unlikely to rise to the level necessary for a therapeutic effect. - There is a risk of exacerbating hyperkalemia by inducing hypeonicity. 5' adrenoceptor agonists These drugs can also cause movement of potassium inside the cell. High dose albuterol shows their effect in 30 minutes and persists for at least 2 hours. The effect of insulin is additive with that of albuterol. Patients taking nonselective 18 adrenoceptor blockers will be unlikely to manifest the hypokalemic effects of albuterol. - Even among patients not taking ft blockers as many as 40% seem to be resistant to the hypokalemic effect of albuterol. - The mechanism .for this resistance is unknown and currently, there is no basis for predicting which patients will respond. - For this reason albuterol should never be used as a single agent for the treatment of urgent hyperkalemia. Bicarbonate Bicarbonate (as a bolus injection) was used in the emergency t/t of hyperkalemia. Ironically this dogma was based on studies using a prolonged (4-6 hrs) infusion of bicarbonate. It has now been demonstrated that sho term bicarbonate infusion does not reduce pK in patients with dialysis dependent kidney failure, implying that it does not cause IC+ shift into cells. Sodium bicarbonate seems to have no effect to shift IC into cells even after several hours. It is likely to be effective especially in combination with a diuretic drug in enhancing urinary IC' elimination in patients with some kidney. function, although it use for this purpose has not been evaluated. iii) Elimination of potassium from the body Hyperkalemia occurs most often in patients with renal insufficiency. - However renal potassium excretion may be enhanced even in patients with significant renal impairment by increasing the delivery of solute to the distal nephron. Sodium bicarbonate A sodium bicarbonate infusion administered during 4-6 hrs at a rate designed to alkalinize the urine may enhance urinary K+ excretion and would be desirable especially in patients with metabolic acidosis. The risk of volume expansion with the bicarbonate infusion can be mitigated by use of loop acting diuretics which would, be likely to enhance the kaliuresis. Exchange resin Sodium polysterene sulfonate is a cation exchange resin. In the lumen of intestine it exchanges sodium for secreted potassium. Most of this exchange takes place in the colon, the site of most potassium secretion in the gut. There are two concerns with the use of resin in the t/t of urgent hyperkalemia The first is its slow effect - When given orally, the onset of action is at least 2 hrs and the maximum effect may not be seen for more than 6 hrs. The second is its adverse effect - It can cause intestinal necrosis Dialysis -"Hemodialysis is the method of choice for removing potassium from the body". - The rate of potassium removed with peritoneal dialysis is much slower than with hemodialysis.
Calcium gluconate IV
Oral resins
Insulin + glucose
Sodium bicarbonate