1 / 43

Hypokalaemia

Hypokalaemia. By Dr Nihal Abosaif Consultant acute physician UHCW. Outline. Physiology of K+ transport Factors modifying transcellular K+ distribution Causes of Hypokalaemia Diseases associated with it Management of Hypokalaemia. Introduction : Potassium .

harsha
Download Presentation

Hypokalaemia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Hypokalaemia By Dr Nihal Abosaif Consultant acute physician UHCW

  2. Outline • Physiology of K+ transport • Factors modifying transcellular K+ distribution • Causes of Hypokalaemia • Diseases associated with it • Management of Hypokalaemia

  3. Introduction : Potassium • Most abundant cation in human body • Regulates intracellular enzyme function and helps to determine neuromuscular & cardiovascular tissue excitability. • 90 % of total body K+ : Intracellular ( predominantly in muscle ) • 10 % : Extracellular fluid • < 1 % : Plasma

  4. Introduction : Potassium • Ratio of extracellular K+ to Intracellular K+ : determines the membrane potential • The acuity of changes in serum potassium concentration & membrane potential determines clinical symptoms and underlying signs • Plasma concentration varies from 3.5 to 5.3 mmol/l

  5. Physiology Of Potassium Homeostasis • K+ uptake into cells : actively driven by Na+/K+/ATPase • Leak back into ECF : opposed by electrical gradient

  6. Factors modifying transcellular K+ distribution • Acid base status • Pancreatic hormones : insulin , glucagon • Catecholamines • Aldosterone • Plasma Osmolality • Exercise • Cellular K+ content

  7. Acid Base Status • Alkalosis promotes K+ uptake by cells • Acidosis diminishes K+ uptake by cells • Acute respiratory alkalosis, in contrast increase plasma K+ by 0.2 mmol/l per 0.1 pH unit due to increased adrenergic activity

  8. Pancreatic Hormones • Insulin stimulates cellular uptake of K+ by activating Na+/K+/ATPase ( decreasing plasma K+ ) • Insulin affects K+ transport independently of glucose uptake • Glucagon increase plasma K+ independently of changes in plasma glucose / insulin

  9. Catecholamines • Beta 2 adrenergic activity – hypokalaemia • Alpha adrenergic antagonists – hypokalaemia

  10. Aldosterone • Invitro studies • Aldosterone stimulates Na+/K+/ATPase and thereby activating Na + influx

  11. Osmolality • Hyperosmolality ( Mannitol infusion / hyperglycemia in DM ) : increase plasma K+ • Each 10 mOsm / Kg rise in plasma osmolality, increases plasma K+ by 0.6 mmol/l

  12. Exercise • Recurrent contraction increases K+ egress from muscle • Modest exercise : high K+ in ECF in local environment produces vasodilatation & thereby increased regional blood flow • Severe exercise : increase plasma K+ modestly • Physical training increases Na+/K+/ATPase activity in skeletal muscle which helps skeletal muscle to take up K+ again

  13. K+ Balance • Kidney is dominant in sustaining K+ balance • >90 % K+ : excreted in urine • Remainder through faeces • Decrease in GFR, K+ excretion via faeces increased • GI Loss : K+ secretion by proximal & distal colon

  14. Renal Handling of K+ • Glomerulus: freely filtered • PCT, TAL, Loop of Henle : reabsorbed

  15. Hypokalemia • Defined as plasma concentration of K+ < 3.5 mEq/L • Mild Hypokalemia : 3.0 – 3.5 mEq/L : asymptomatic • Hypokalemia < 3.0 mEq/L : symptomatic • Clinical manifestations of hypokalemia vary greatly between individual patients & their severity depends on degree of hypokalemia

  16. Diagnosis • Clinical features • Investigations

  17. Clinical Features • Mild hypokalemia : generally asymptomatic Increased risk of mortality for pts with cardiovascular disease – trigger ventricular tachycardia / ventricular fibrillation (decrease K+ : d/t sympathetic stimulation) Digitalis induced arrhythmias – can occur with normal drug levels if hypokalemia is present Diuretic induced hypokalemia & hypomagnesemia must be avoided in pts on drugs that prolong QT interval : as it predisposes to polymorphic VT / Torsade de pointes • Hypokalemia < 3 mEq/L : Symptomatic

  18. Cardiac • Digitalis Intoxication : ventricular extrasystoles ventricular tachycardia ventricular fibrillation partial-complete AV block bradycardia atrial flutter atrial fibrillation • Ventricular arrhythmias : tachycardia / fibrillation

  19. Neuro-muscular • Fatigue • Myalgia • Muscular weakness involving lower limbs Severe Hypokalemia : • Paralysis ( extremities ) • Weakness of respiratory muscles ( dyspnea ) • Rhabdomyolysis (exercise induced)

  20. Gastro-intestinal • Constipation • Paralytic ileus

  21. Renal • Chronic interstitial nephritis due to functional decrease in renal blood flow – decreased GFR • Chronic renal failure • Renal Cysts

  22. Fluid – Electrolyte • Polyuria ( nephrogenic diabetes insipidus ) • Polydipsia ( nephrogenic diabetes insipidus ) • Increased ammonia production ( intracellular acidosis ) precipitate hepatic coma in pts with advanced liver ds • Edema • Chloride wasting • Metabolic alkalosis • Hypercalciuria • Phosphaturia

  23. Endocrine • Glucose intolerance ( decreased insulin secretion ) • Growth retardation ( Reduced Growth hormone receptors, Reduced IGF-1 ) • Hypertension ( increased renin secretion )

  24. Basic Investigations • ECG : Initially : flattening of t wave depression of ST Segment development of prominent u waves Severe hypokalemia : increased amplitude of p wave increased QRS duration • S.Potassium

  25. Investigations – Causes • Urinary K+ • TTKG • Urinary Chloride • CBC • Peripheral Smear • ABG • Echocardiogram • Cardiac Enzymes • Serum aldosterone • Serum renin • USG Abdomen • CT / MRI Abdomen • FBS / PPBS / Urine Ketones • TSH / free T3 / free T4 • Colonoscopy / OGDscopy

  26. Causes of hypokalaemia • Decreased net intake • Shift into cells • Increased net loss

  27. Spurious Hypokalemia • Occurs in patients with extreme leukocytosis eg : in myeloproliferative disorders • Invitro WBC uptake potassium within the test tube

  28. Decreased Intake or increased loss • Starvation • Clay ingestion ( binds to dietary K+ & Iron ) • Diarrhoea and vomiting

  29. Transcellular shifts • Acid – Base Status : Metabolic Alkalosis • Hormonal : Increased Insulin Increased Beta 2 Adrenergic activity • Drugs : Beta 2 agonists Theophylline Barium Intoxication Chloroquine Calcium Channel Blockers

  30. Transcellular shift • Catecholamine release associated with : • Asthma • COPD – exacerbations • Heart failure • Myocardial infarction / angina • Drug withdrawal syndrome – alcohol / narcotics / barbiturates

  31. Transcellular shift • Insulin administration – for treatment of DKA • Refeeding Syndrome • Hypokalemic Periodic Paralysis • Thyrotoxic Periodic Paralysis • Treatment of anemia : Vit B12 / Folic acid deficiency • Use of GM – CSF in patients with Neutropenia

  32. Renal Vs Extra renal loss • Urinary K+: > 20 mEq/L – Renal loss • Urinary K + : < 20 mEq/L – Extrarenal loss • TTKG : Transtubular Potassium Gradient ( Urine K+ / Plasma K+ ) ( Urine Osm / Plasma Osm ) • TTKG : Renal loss : > 4 Extra renal loss : < 4

  33. Algorithm for diagnosis of Extra Renal Loss

  34. Renal Loss

  35. Renal Loss + Metabolic Alkalosis

  36. Renal loss +Urine Cl > 20 mEq/L

  37. Renal loss - Drugs • Amphotericin B : tubular damage increased excretion of K+ • Aminoglycosides : renal wasting of K+ • Thiazides, Furosemide, Acetazolamide : renal loss K+ • Cisplatin • HYPOMAGNESEMIA : Significant renal K+ wasting

  38. Management of Hypokalaemia • If mild asymptomatic • Oral KCl • If severe or symptomatic hypokalemia • IV KCl supplement

  39. IV infusion rate for severe or symptomatic hypokalemia .

  40. THANK YOU

More Related