Normal Range
- Potassium is a macromineral
- Normal serum potassium level = 3.5-5 mEq/L
- Estimated by Flame photometry or Ion Selective electrode
- Serum potassium concentration does not vary appreciably in response to water loss or retention
- Mainly excreted through urine
- Aldosterone and Corticosteroids increase K+ excretion.
Hypokalemia
- Plasma potassium below 3mmol/L
- Must be viewed with caution as mortality and morbidity are high
Causes of Hypokalemia
- Increased gastrointestinal losses-
- Vomiting
- Diarrhea
- Aspiration
- Low potassium in diet
- Malabsorption of potassium
- Pyloric obstruction
- Increases renal loses-
- Administration of diuretics for congestive cardiac failure.
- Overactivity of adrenal cortex in Cushing’s syndrome
- Acute tubular necrosis
- Metabolic Alkalosis
- Hyperaldosteronism
- Hyper-reninism
- Renal artery stenosis
- Hypomagnesemia
- Renal tubular acidosis
- Adrenogenital syndrome
- 17-alpha hydroxylase deficiency
- 11-beta hydroxylase deficiency
- Potassium Redistribution-
- Metabolic alkalosis- K moves into cell in exchange for H+
- Insulin therapy
- Thyrotoxic periodic paralysis due to abnormal Na-K-ATPase
- Hypokalemic periodic paralysis due to abnormal calcium channels
- Administration of glucose and insulin in diabetic coma
- Administration of drugs like-
- Insulin
- Salbutamide
- Osmotic diuretics
- Thiazides
- Acetazolamide
- Corticosteroids
Signs & Symptoms of Hypokalemia
- Muscular weakness, fatigue, and cramps.
- Hypotension with palpitation
- Tachycardia
- Cardiomegaly
- Decreased reflexes
- ECG changes like-
- Flattened waves
- Inverted T-waves
- Depressed ST segment with AV block
- Cardiac arrythmias and arrest.
Treatment of Hypokalemia
- Potassium supplementation at 200-400mmol per 1mmol fall in serum potassium.
- 100mmol KCl/day in 3-4 doses
- IV in acute cases, no more than 10mmol/hour
- Magnesium supplementation and alkalosis correction are also required.
- Â Daily potassium assay to be continued even after recovery.
Hyperkalemia
- Plasma potassium above 5.5mmol/L
- Even minor increase is life threatening
Causes of Hyperkalemia
- Transmembrane shift
- Hyperkalemic periodic paralysis
- Cell damage due to trauma and malignancy
- Decreased renal excretion of potassium-
- Obstruction of urinary tract
- Renal failure due to low GFR
- Deficient aldosterone as in Addison’s disease.
- Severe volume depletion (heart failure)
- Entry of potassium to extracellular space-
- Increased hemolysis
- Tissue necrosis
- Burns Tumor lysis after chemotherapy
- Rhabdomyolysis,
- Crush injury
- Excess potassium supplementation
- Malignant hypertension
- Redistribution of potassium to extracellular space
- Metabolic acidosis
- Insulin deficiency (diabetes mellitus)
- Tissue hypoxia
- Pseudo hyperkalemia-
- Factitious (K+ leaches out when blood is kept for a long time before separation)
- Improper blood collection (hemolysis)
- Thrombocytosis (> 400 million/mL)
- Leukocytosis (>11 million/mL)
- Drugs-
- Spironolactone
- ACE inhibitors
- Beta blockers
- Cyclosporine
- Digoxin
Signs & Symptoms of Hyperkalemia
- Muscle weakness preceded by paresthesia(abnormal tingling sensation)
- Ventricular arrhythmia due to increased membrane permeability
- Ventricular fibrillation
- Depression of CNS with mental confusion and numbness.
- Bradycardia with reduced heart sounds.
- Flaccid paralysis
- Cardiac arrest
- ECG changes-
- Elevated T-wave
- Widening of QRS complex
- Lengthening of PR interval
Treatment of Hyperkalemia
- For K > 6.5mmol/l, 6 units of plain insulin with 50% dextrose to be given intravenously over 10 minutes to stimulate glycogen synthesis
- 0.3mMol of K+ is trapped intracellularly for every 1g of glycogen stored.
- 10ml of 10% calcium gluconate to be given over 5 minutes intravenously to stabilize myocardium.
- Correction of hyperglycemia and acidosis required
- 500ml of 1.4% NaHCO3 to be given over 2 hours if patient is acidotic
- Continuous monitoring of ECG and Volume overload required
- Dialysis may be required in renal failure.