泌尿系统教学课件：Disorders of Potassium Metabolism.ppt

单击此处编辑母版标题样式,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,1,Disorders of Potassium Metabolism,2,Content,1.Normal metabolism of Potassium,(1)Content and distribution,(2)Regulation of K,+,balance,(3)Function of potassium,2.Hypokalemia 3.Hyperkalemia,3,1.,Normal metabolism of potassium (1)Content and distribution,The adult body contains about 45 mmol/Kg of BW.,About 98%of potassium is within the cells,K,+,i=140160 mmol/L.,About 2%of K,+,is in the ECF,K,+,e=3.55.5 mmol/L.,75%of the intracellular K,+,is in muscle cells,.,4,(2)Regulation of K,+,balance,1)Equilibrium of K,+,in ICF(98%)and ECF(2%)(Transcellular potassium),2)Balance of intake and excretion,5,1)Equilibrium of K,+,in ICF and ECF(transcellular potassium movement),Equilibrium means to keep,K,+,i=140160 mmol/L;,K,+,e=3.55.5 mmol/L,6,Mechanism to keep the equilibrium between ICF and ECF:,The basic mechanism to the balance is,“leak and pump”.,(A)Functioning of Na,+,-K,+,pump,(B)Influence of leaking,7,(A)Functioning of Na,+,-K,+,pump,“Pump”,means the active transport of K,+,from ECF to ICF,against the concentration gradient of K,+,with expending ATP.,If the function of Na,+,-K,+,pump is impaired(e.g.anoxia,acidosis),relative more K,+,will move out of the cells by leaking,which will lead to high K,+,e.,A)Insulin promotes the movement of K,+,into the liver cells and skeletal muscle cells for glycogen synthesis via the Na,+,-K,+,pump activation.,Na,+,-K,+,pump activation,K move from ECF to ICF,【K,+,】,e,8,B),-adrenergic agonists elevate Na,+,-K,+,ATPase activity.,-adrenergic agonists enhance K,+,transport out of cells by reducing Na,+,-K,+,ATPase activity.,C)Aldosterone increases the activity of Na,+,-K,+,ATPase.,9,D)A high K,+,e will stimulates Na,+,-K,+,ATPase activity,E)Strenuous physical exercise can promote the K,+,shift out of cells.,ATP depletion decrease the activity of Na,+,-K,+,ATPase.,10,(B)Influence of leaking,“Leak”,indicates the moving of K,+,out of the cell according to the gradient of K,+,between ICF and ECF,without expending ATP.,Leaking leads to the tendency to reduce the,K,+,i.,A)When the cell membrane is injured,the permeability of cell membrane to K,+,is increased.More K,+,move from cells into ECF.,11,B)Acidosis induces K,+,movement out of cells.(Alkalosis?),A decrease 0.1 of pH elevates K,+,e about 0.6mmol/L.,12,C)Increased osmolality of extracellular fluid draws water out of cells,increases the K,+,i and the gradient of K,+,between ICF and ECF,so more K,+,out of cells.,(in hyperglycemia),13,2)Balance of intake and excretion,Intake:The common foods,like lean meat,milk and fruits content a lot of potassium.,The average diet contains 60100 mmol of potassium per day,which is enough for the daily body requirement.90%of potassium in food is absorbed in small intestine.,The same amount of K,+,as intake,must be excreted.,14,Excretion,(A)Via kidney,About 90%or more potassium is eliminated from kidney.,The more K we eat,the more K is eliminated from kidneys.When the intake of potassium is decreased,the elimination from urine is decreased.,If no potassium intake,the kidneys will still secrete small amount of potassium.,15,Potassium is freely filtered at the glomerulus.Almost all the potassium filtered is reabsorbed in proximal tubules via active transport(65%),and in loop of Henle via Na,+,-K,+,-2Cl,-,cotransporter(27%).,16,Most of the potassium in the urine is,secreted from distal tubules,and collecting ducts by Na,+,-K,+,exchange mechanism.,17,Factors that affect the secretion of potassium in distal tubules and collecting ducts:,Increase of potassium concentration in ECF,Aldosterone,Na,+,-K,+,pump,Secretion of K,+,Acute acidosis,Na+-K+pump,Secretion of K,+,18,(B)Via intestinal tract,10%of potassium in food is eliminated by feces.There are more loss of potassium with watery stool.,The epithelial cells of colon excrete K,+,as the same way as distal tubular cells(principal cells)controlled by aldosterone.,19,(C)Via sweating,Generally speaking,the loss of K,+,with sweat is neglectful(510 mmol/L).This kind of loss may be significant some time(in plenty of sweat).,20,(3)Function of potassium,1)Metabolism,2)Membrane potential,3)Regulation of pH,4)Osmotic pressure of ICF,21,1),Metabolism,K,+,is required for the activity of some intracellular enzymes e.g.the enzyme for ATP production.,K,+,is involved in anabolism.,1 g of glycogen contents 0.330.45 mmol,The K,+,moves into cells with glucose,during the synthesis of glycogen.,1 g of protein needs 30 mmol of K,+,.,22,2),Membrane potential,K,+,i,RMP=59.5 lg-,K,+,e,23,Minimal increase or decrease of K,+,e will lead to the change of membrane potential.,K,+,is important for normal neuromuscular irritability.,24,3)Regulation of pH,Exchange of K,+,and H,+,crossing the cell membrane is important for acid-base balance.,When K,+,moves out of the cells,H,+,will move into the cells as an exchange for electrical neutral.More H,+,will lead to acidosis.,Changes of K,+,concentration will lead to the changes of pH.,25,4)Osmotic pressure,Potassium ion is the major intracellular cation,so K,+,is important in the formation of osmotic pressure in the cell.,26,2.Hypokalemia,(1)Concept,(2)Causes,(3)Effect on the body,(4)Principle of treatment,27,(1)Concept,Hypokalemia indicates the K,+,in plasma is 5.5mmol/L is defined as hyperkalemia.,If the increase of serum K,+,is caused by the movement of potassium from ICF to ECF,the hyperkalemia does not mean,potassium excess.,70,(2)Causes,1)Decrease of renal excretion potassium,2)Increased potassium intake,3)Increased movement of potassium from,cells to ECF,71,1),Decrease of renal excretion potassium,(a)GFR decrease:,oliguria and anuria,Normally 90%of potassium is excreted from kidneys.,The serum K,+,increases 0.7 mmol/L per day if the patient is anuria without K intake,and 10 days later,the patient with anuria will die from hyperkalemia.,72,(b)Absence of aldosterone:Addisons disease,hypoaldosteronism,renal tubule acidosis-IV,(c)Some diuretics(e.g.spironolactone,an antagonist of aldosterone):inhibit the sodium reabsorption and the secretion of K is reduced.,73,2),Increased potassium intake,Eat more if oliguria.,Too rapid intravenous administration of KCl leads to a severe incident,which is fatal.,Before the intravenous infusion of KCl,we must make sure that the renal function is good enough to eliminate potassium.,Intravenous solution containing potassium should never be started until urine has been assessed.,74,3),Increased movement of potassium from ICF to ECF,(a)Acidosis:,(b)Cell destruction:tissue trauma,burn,rhabdomyolysis,lysis of tumor cells by cytotoxic agents,hemolysis.,(c)Hypoxia:sodium retention in cell,acidosis and cell necrosis,(4)Hyperkalemia periodic paralysis:,subunit,of voltage gated sodium channel,75,(3)Effect on the body,1)Effect on the neuromuscular irritability,2)Effect on the heart,3)Effect on acid-base balance,76,1)Effect on the neuromuscular irritability,In mild hyperkalemia(7mmol/L),the neuromuscular irritability is decreased.,(Biphasic),77,In hyperkalemia,the RMP is less negative(partial depolarization),the difference between the RMP and TMP is decreased,which means that a smaller stimulus will evoke an action potential(AP).,The excitability(irritability)of skeletal muscles is increased at first.,78,manifestation of skeletal muscle:stabbing pain and abnormal sensation(too sensitive for pain)at first(with mild hyperkalemia),。,79,In severe stage,the RMP or=TMPNa,+,channel will not open.The excitability is decreased to disappear.The excitability(irritability)of skeletal muscles is then decreased at last.,(Biphasic),then weakness and paralysis in severe stage.,80,The excitability(irritability)of smooth muscles of GI tract is increased at first,then decreased at last.,(Biphasic),It may be manifested at first by diarrhea,intestinal colic(abdominal pain)and abnormal sensitivity(paresthesia),then abdominal distension.,81,2)Effect on the heart,(a)A gradual increase of serum K,produces,biphasic,sequences of,excitability,of myocardiac cells.An initial increase of excitability is followed by a decrease.(same as the effect on skeletal and smooth muscle),82,(b)The,conductivity,of myocardiac cell is reduced.,The difference between the RMP and TMP is decreased,The rate of depolarization is reduced in hyperkalemia,because the RMP is near the TMP.,83,(c),The autorhythmicity is decreased,because the membrane permeability to potassium is increased,the outward potassium current is increased and the inward sodium current is relatively decreased.,Sinoatrial node is not sensitive to hyperkalemia.The autorhythmicity decreasing focused on Purkinje cell.,84,(d)The contractivity is reduced due to decreased intracellular calcium,because the high K,+,e inhibits the inward flow of calcium and Na,+,-Ca,2+,exchange increase due to the Na,+,-K,+,pump activation.,85,(f)Changes of ECG,T wave,is peaked and tent-shaped because phase 3 is accelerated due to rapid outward of potassium(Potassium permeability of membrane of myocardiac cells is increased.),P wave,is prolonged and eventual disappear due to the decreased conductivity and excitability in atrium.,QRS complex,is widened due to the decreased conductivity in ventricle.,86,3)Effect on acid-base balance,(a)extracellular acidosis,When K,+,of ECF is increased in hyperkalemia,the K,+,of ECF moves into the cells,at the same time the H,+,in ICF moves into the ECF for electric neutrality.Then the H,+,in ECF will be increased.,87,(b)unusual alkalinuria.,There are two kinds of ion exchange,K,+,-Na,+,and H,+,-Na,+,in renal tubules.,In hyperkalemia,the K,+,-Na,+,exchange is increased,the H,+,-Na,+,exchange will decrease,so the excretion of H,+,from kidneys is reduced,which leads to basic(alkaline)urine.,88,(4)Principle of treatment,1)Complete restriction of exogenous,potassium intake.,2)Control of the underlying disease,(etiologic treatment),3)Transport of the serum K,+,into cells (a)Administration of insulin and glucose to transport the potassium from ECF into the cells.,(b)Bicarbonate infusion(alkaline solution)can drive the potassium into the cells.,89,4)Increase the elimination of potassium,(a)A sodium polystyrene sulfonate resin is,used to remove potassium from colon.,(b)Peritoneal dialysis,(c)Hemodialysis,90,(5)Protection of cardiac cells,A increased Ca,2+,may raise the threshold potential,which may reestablish the difference between the resting and threshold potential and restores the excitability.,A increased Na,+,will increase the inward sodium current in phase 0(depolarization)to increase the excitability of heart muscle.,