Role Of Potassium In Human Body

2. Role Of Potassium In Human Body

3. IMPORTANCE • Important for skeletal and cardiac muscles activities.The depolarization and contraction of heart requires potassium.

4. Consequences • Hypokalemia causes tachycardia, ECG changes and irregular heart beat. • Hyperkalemia is associated with cardiac arrhythmia( ventricular fibrillation), bradycardia,ECG changes ( elevated T waves) • If it goes up to 7 meqt/l it can even stop the heart beat, (cardiac arrest) which can lead to death.

6. Total body contents and regulation of K. Dietary sources/Daily Requirements Metabolism / absorption and excretion Important functions and Related health problems/diseases Learning Objectives

7. Body content and distribution • Total body content is 115 grams. • 70-75% is in skeletal muscles. • 20-25% is in soft tissues • It is the major Intra cellular cation (150 meqt/ Liter) • ECF contains 3.5-5.5 meqt/ liter.

8. DISTRIBUTION • Whole blood 200 mg/dl • Plasma 20 mg/l • Cells 440 mg/100 g • Muscles 250-400 mg/100 g • Nerve Tissues 530 mg/100 g

9. Potassium balance Potassium balance When gain = loss Major gain is through GIT absorption ~100 mEq (1.9–5.8 g)/day

10. Potassium Loss • Major loss is excretion by kidneys • Primary ECF potassium regulation by kidneys • Controlled by aldosterone regulating Na+/K+ exchange pumps in Distil ConvulutedTubules (DCT) and collecting duct of nephron. • Potassium is also excreted in GIT, Saliva, Gastric juice, Bile , Pancreatic and Intestinal juices.

11. This route of loss becomes clinically important • When these secretions are lost in large amount. • K+ is continuously filtered by the glomeruli and reabsorbed by the Proximal Convoluted Tubules (PCT). • K+ are also secreted in DCT in exchange for sodium.

12. Effect of Low pH Low ECF pH can cause H+ to be substituted for K+ • Potassium is highest in ICF due to Na+/K+ exchange pump • ~145 m Eq/L in ICF vs. • ~ 5.6 m Eq/L in ECF

13. The major factors involved in potassium balance • Factors Controlling Potassium Balance • Approximately 100mEq (1.9–5.8 g) of potassium ions are absorbed by the digestive tract each day. • Roughly 98 percent of the potassium content of thehuman body is in the ICF. • The K concentration in the ECF is relatively low. • The rate of K entry from the ICF through leak channels is balanced by the rate of Krecovery by the Na/K exchange pump. • When potassium balance exists, the rate of urinary K excretionmatches the rate of digestive tract absorption.

14. The major factors involved in potassium balance Factors Controlling Potassium Balance Approximately 100mEq (1.9–5.8 g) ofpotassium ions are absorbed by thedigestive tract eachday. Roughly 98 percent of thepotassiumcontent of thehuman body is inthe ICF, ratherthan the ECF. The K concentration in theECF is relatively low. The rateof K entry from the ICFthrough leak channels isbalanced by the rate of Krecovery by the Na/Kexchange pump. When potassiumbalance exists,the rate of urinaryK excretionmatches the rateof digestive tractabsorption. The potassium ionconcentration in theECF is approximately5 mEq/L. KEY  Absorption The potassium ionconcentration of theICF is approximately135 mEq/L. Renal K lossesare approximately100 mEq per day  Secretion  Diffusion through leak channels

15. The role of aldosterone-sensitive exchange pumpsin the kidneys in determining the potassiumconcentration in the ECF The primary mechanism ofpotassium secretion involvesan exchange pump thatejects potassium ions whilereabsorbing sodium ions. Tubularfluid ECF The sodium ions are then pumped outof the cell in exchange for potassiumions in the ECF. This is the same pumpthat ejects sodium ions entering thecytosol through leak channels. KEY  Aldosterone- sensitive exchange pump  Sodium-potassium exchange pump

16. Events in the kidneys that affect potassium balance Under normal conditions, thealdosterone-sensitive pumpsexchange K in the ECF forNa in the tubular fluid. Thenet result is a rise in plasmasodium levels and increasedK loss in the urine. Distalconvolutedtubule When the pH falls in the ECFand the concentration of H isrelatively high, the exchangepumps bind H instead of K.This helps to stabilize the pHof the ECF, but at the cost ofrising K levels in the ECF. Collectingduct

17. Disturbances of potassium balance Hypokalemia Below 3 mEq/L in plasma Can be caused by: Diuretics Aldosteronism (excessive aldosterone secretion) Symptoms Muscular weakness, followed by paralysis Potentially lethal when affecting heart Potassium imbalance

18. Hyperkalemia Above 5.6 mEq/L in plasma Can be caused by: Chronically low pH Kidney failure Drugs promoting diuresis by blocking Na+/K+ pumps Symptoms Muscular spasm including heart arrhythmias Potassium imbalance

19. Potassium • Alkali metal • Highly reactive, • Found in combined state, mostly as Salt.

20. Dietary sources • Meat ,Chicken , Beef liver • Milk • Dried apricots, Peaches • Oranges, Banana, • All vegetables • Broccoli, Tomato

21. DIETARY SOURCES • Human milk contains about 500mg/liter, • cow’s milk contains 1400 mg/liter. • 3-4 grams /day is normally provided by a balance diet • Deficiency is rare .

22. Infants 0 – 0.5 yr = 350 – 925 0.5 – 1.0 yr = 425 – 1275 Children 1 – 3 yr = 550 – 1650 4 – 6 yr = 775 – 2325 7 – 10 yr = 1000 – 3000 11+ = 1525 – 4575 Adult = 1875 – 5600 Requirement (mg)

23. In infants lean body mass and fecal losses are main determinants of potassium need. • Adults can maintain potassium balance with intake as low as infants. • Conc. of K+ is low in sweat. • Less than 390 mg or 10 mEq/L as compared to • Na, which is 25 – 30 mEq/L.

24. Absorption and Metabolism • Kis almost completely absorbed from gut. ( SI &LI) • Very little K is lost in feces (less than 10 %) • Kidneys regulate its secretion under the influence of change in acid-base balance and activity of adrenal cortex. • Hyper kalemia not likely to develop even after ingestion or injection of large amount of K, if kidney function is intact.

25. DIETARY INTAKE AND EXCRETION • Daily intake recommended 1.5 … 4.5 grams • Average Diet contains 4 … 8.0 grams EXCRETION • Excreted mostly in Urine • K ions filtered freely in the glomerular filterate • 93 % is reabsorbed mostly in the proximal convoluted tubules

26. FUNCTIONS • Major cation in ICF, maintains intracellular osmotic pressure there . 98% is found in ICF. • ECF K+ is an important factor in the skeletal and cardiac muscle activity. • Contraction and depolarization of heart require potassium

27. Functions Proper plasma potassium level is essential for : • Normal heart function • Normal function of skeletal muscle fibers • Many enzyme reactions • Neuron and muscle activity

28. Functions • Resting membrane potential along with Na and Cl. • An important role in the renal tubule, where K+ compete with H+ for exchange with Na+ • K + are required for the activity of Na / K- ATPase

29. Hypokalemia • Decrease K+ intake Starvation Malnutrition Old age K free fluid I.V

30. Hypokalemia • Excessive renal loss a. Diuresis with Frusemide and Thiazide b. Metabolic Alkalosis _ Deficiency of H+ ion • Tubular cells • More K+ ions undergo change with Na+ • Accelerate hypokalemia

31. Hypokalemia • Renal Diseases • Excessive loss of K+ ion due to any cause/diuretic • Recovery phase of Acute Renal Failure • Chronic Pyelonephritis • Renal tubular Disorders

32. Hypokalemia • Post operatively e. Hormones • Aldosterone  loss of K+ • Excess cortisol or overdose of ACTH same effect

33. 3- Loss from GIT • Vomiting • Diarrhea • GI. Fistulas • Excessive use of purgatives

34. Hypokalemia • Excessive Transfer to Cells • Glycogenesis • Paralysis

35. Sign and Symptoms • Anorexia • Nausea • Muscle weakness • Mental depression • Respiratory weakness

36. Sign and Symptoms • Dyspnea • Rapid and irregular pulse • Low BP • ECG Changes: T-wave inversion • Reduce insulin secretion

37. Hypokalemia Hypokalemia occurs with: • Excessive loss in diarrhea • Diabetic Acidosis • Certain laxatives and • Diuretics

38. Causes of Hypokalemia • When Glucose is converted to glycogen for storage , some K is also stored. • Treatment with insulin results in glucose metabolism and storage along with K with-drawl from blood and results in Hypokalemia. • K replacement should be considered.

39. Causes of Hypokalemia • Chronic wasting diseaseKlowering / deficit associated with malnutrition prolonged –ive Nitrogen balance and GE losses. • K is stored with nitrogen as muscle protein. Therefore, when breakdown occurs, K also transferred from ICF to ECF and removed by kidney.

40. Management When rehabilitating from these diseases, diet should contain K+ along with amino acid to ensure adequate retention.

41. Hyperkalemia • In health, generally not seen • K+ ion excretion is efficient • However certain clinical conditions lead to hyperkalemia

42. 1. Release from tissues • Crushed or infected tissues • Intra vascular hemolysis • Hematomas • Burnt tissues • Extensive surgical operations • Sudden lysis of tumors

43. 2. Renal Insufficiency • Excretion by the distil convoluted Tubules if lower, leads to retention of K+ • It is normally the case ,when oligouria is associated

44. 3. Chronic Dehydration & Shock • Decreased formation of urine • K+ retention

45. 4. Acidosis :H+ ion displaces K+ion5. Fever :  temp excessive break down of tissues body proteins 6. Addisons Disease Less K+ secreted by distal tubules into urine 7. I.V. administration

46. Symptoms • Heart • ECG changes when plasma K+ reaches 7 mmoles/L • T-waves becomes high peaked • P-waves disappears • QRS-complex broad • Wide spread cardiac blocks appear • Bradycardia and arrhythmias appear • Sudden death may take place

47. Symptoms 2. Nervous Symptoms • Mental confusion • Weakness of muscles • Tingling of the extremities Treatment: • Removal of the primary cause

48. Very high sudden intake 12 gms (250 – 300 mEqt / per sq. m. of body surface area/day or 18 gmsfor an adult may be fatal because leads to Cardiac arrest.

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