Emergency points in nephrology

Dr Mojgan MortazaviNa /K DisordersSODIUM

HyponatremiaHyponatremiaHyponatremia defined as a Na+ Na+ loss>20 mEq/LRenal loss Diabetic insipidis Central Nephrogenic20 mEq/LRenal loss Diuretic Glycosuria Renal failureExtrarenal loss GI-vomiting GI-diarrhea Excess sweating Respiratory lossHypertonicdialysis Hemodilysis Peritoneal dialysisTreatment Water replacement D5W at 1-2 mEq/L/hr vasopressin for Central DIMineralocorticoid 1 Hyperaldosteronism Cushing disease Adrenal

oTreatment Diuretics dialysisTreatment Saline then hypotonic solutionSymptoms of hypernatremiaLethargy ,weakness, irritability, are the earliest findings which can then progress to twitching ,seizures, coma, and death that are more related to cellular dehydration in the brain.Patients with chronic hypernatremia may be relatively asymptomatic despite a plasma Na+ >170The severity of the neurologic symptoms is related to the both the degree and more importantly ,the rate of rise in the effective plasma osmolality. Treatment of hypernatremiaRapid correction of hypernatremia can induce cerebral edema, seizures, permanent neurologic damage, and death therefore the plasma Na+ must be slowly lowered unless the patient has symptomatic hypernatremia. Treatment of hypernatremiaWater deficit= 0.4 LBW( plasma Na-140/ 140)The maximum safe rate at which the plasma Na+ should be lowered (in the absence of hypernatremic symptoms) is 0.5 meq/L/h or 12 meq/L/per day Formula for Managing HypernatremiaCLINICAL USE

Estimate the effect of 1 liter of any infusate on serum Na+Estimate the effect of 1 liter of any infusate containing Na+ and K+ on serum Na+FORMULA*

1.Change in serum Na+ =

2.Change in serum Na+ =infusate Na+ - serum Na+total body water + 1(infusate Na+ + infusate K+) -serum Na+total body water + 1Characteristics of InfusateInfusateInfusate Na+Extracellular-Fluid Distributionmmol per liter %5% Dextrose in H20 0 400.2% NaCl in 5% dextrose in H2O 34 550.45% NaCl in H2O 77 73Ringers lactate130 970.9% NaCl in H2O154100Summary of Managing HypernatremiaIsotonic saline unsuitable except in ECF volume depletion causing hemodynamic instabilitySwitch to hypotonic solutions as soon as circulatory status stabilizedAvoid excessive rapid correction or over correctionSelect the most hypotonic infusate suitable with appropriate allowances for ongoing fluid lossesMost important - reassess infusion prescriptions at regular intervals based on pts clinical status and electrolyte values

POTASSIUM

POTASSIUM BALANCEPotassium is the major intracellular cation that is essential for a variety of cellular and neuromuscular functions.The total body K+ stores in a normal adult are 3000-4000 meq(50-55meq/kg) and the normal plasma concentration is 3.5-5 meq/l and inside cells is about 140 meq/lRegulation of potassium balanceThe maintenance of K+ balance involves two functions: 1-the normal distribution of K+ between the cells and extra cellular fluid 2-the renal excretion of the K+ added to the extra cellular fluid from dietary intake and endogenous cellular breakdownFactors influencing the distribution of K+ between the cells and extra cellular fluidPhysiologic: 1-Na+k+ ATPase 2-catecholamines 3-insulin 4-plasma potassium concentration 5-exercisePathologic: 1-chronic disease 2-extra cellular PH 3-hyperosmolalityRenal excretion of k+The urine is major route by which the K+ derived from diet and endogenous cellular breakdown , is eliminated from the body.The primary event in urinary K+ excretion is the SECRETION of K+ from the tubular cell in to the lumen in the distal nephron.Renal Handling of K+Glomerulus: freely filtered

PCT, Thick As limb LOH : reabsorbed

HypokalemiaHypokalemiaHypokalemia is defined as a K+ 20 mEq/day Na+>100 mEq/dayExclude reredistribution Alkalosis Insulin Periodic paralysis Barium poisoning Vitamin B12 therapyNormal blood pressureHigh blood pressurePlasma renin levelsSerum HCO3 -Low plasma reninHigh plasma renin Malignant HTN Renovascular disease Renin secreting tumorHigh HCO3 -Low HCO3 RTAUrine chloride 4 Extra renal loss : < 4

Renal Vs Extra renal loss Extra Renal Loss Renal LossAmphotericin B : tubular damage increased excretion of K+Aminoglycosides : renal wasting of K+Thiazides, Furosemide, Acetazolamide : renal loss K+Cisplatin

HYPOMAGNESEMIA : Significant renal K+ wasting Renal loss - DrugsRenal Loss + Metabolic Alkalosis Renal loss +Urine Cl > 20 mEq/LTreatment of hypokalemia.A variety of potassium preparations are available for oral and IV use including the CL-, HCO3-, phosphate ,gluconate.In metabolic alkalosis and hypokalemia KCL preparation is choiceIn metabolic acidosis and mild degree of hypokalemia KHCO3 is preferredORAL: KCL can be given orally in salt substitutes as a liquid or in a slow release tablet or capsule

Treatment of hypokalemia.IV: the standard IV kcl solution contains 2meq/ml each of k+ and cl-.20-40 meq of k+(10-20 ml) is added to each liter of saline solution.In general ,no more than 60 meq/l should be given through a peripheral vein ,since higher concentration of k+ are very irritating ,resulting in pain and sclerosis of the vein. Treatment of hypokalemia..1-If k+ is between 3 to 3.5 meq/l treatment is not urgent and these patients can usually be treated with oral kcl at an initial dose of 60-80 meq/day2-In patients with sever symptoms or marked hypokalemia ,k+ must be give more rapidly. The plasma k+ will acutely rise by as much as 1-1.5meq/l after 40-60 meq oral kcl and by 2.5-3.5 meq/l after 135-160 meq/l but these maximum effect is transient ,why?Rate of potassium repletionIV potassium is administered at a maximum rate of 10-20 meq/h although as much as 40-60 meq/h has been given to patients with paralysis or life threatening arrhythmias. This solution containing as much as 200 meq of k+ /L and are best tolerated if given into a large vein such as femoral vein (infusion through a central venous line should probably be avoided, why?

Rapid administration of k+ is potentially dangerous even in severely k+ depleted patients and should be used only in life threatening situation HYPERKALEMIAHYPERKALEMIAHyperkalemia defined as a k+>5meq/l occurs as a result of either k+ release from cells or decreased renal loss.There is an adaptive response in hyperkalemiaHyperkalemiaSpurious Hemolysis Thrombocytosis Leukocytosis Mononucleosis (leaky RBC)Potassium excessRedistribution Acidosis Diabetic ketoacidosis -Blockade Succinylcholine Periodic paralysis Digoxin toxicity

Tubular hyperkalemiaWithout aldosteroneDeficient Acquired Obstruction Renal transplants SLE Amyloidosis Sickle cell Drugs K-sparing diureticsGFR >20 mL/minGFR