Electrolyte Imbalance - Sodium Disorders PDF

ELECTROLYTE IMBALANCE SODIUM DISORDERS Dr. Tarek Kassem, PharmD, BCPS, BCACP. 1 Na+ Definition/clinical manifestations a. Normal concentratio...

ELECTROLYTE IMBALANCE SODIUM DISORDERS Dr. Tarek Kassem, PharmD, BCPS, BCACP. 1 Na+ Definition/clinical manifestations a. Normal concentration: 135–145 mEq/L b. Mild hyponatremia: 125–135 mEq/L c. Moderate hyponatremia: 115–124 mEq/L d. Severe hyponatremia: 115 mEq/L or less 2 Overview Major cation in ECF, AND responsible for its osmolality The most common electrolyte disturbances in practice Inpatient and ambulatory Hyponatremia < 135 mEq/L Hypernatremia >145 mEq/L 3 Hyponatremia=Na 280 mOsm/L [ hypertonic hypo] or hypotonic depending on serum osmolality 280 mOsm/L What’s happening: Suggestive of excess non-sodium osmoles in ECF causing fluid shifts: ICF to ECF Diabetic ketoacidosis – for every 100 mg/dl increase in glucose, there is a decrease in serum sodium by 1.7 [1.6-2.4]mEq/L Mannitol, ethylene glycol, and sorbitol are less common. Treatment: treat underlying cause 9 Isotonic Hyponatremia Posm around 280 mOsm/L Also known as Pseudohyponatremia Na+ content in the body is not actually reduced Instead, Na+ shifts from the EC compartment into the cells in an attempt to maintain plasma osmolality in a normal range. Severe hyperlipidemia can be associated with a normal osmolality Treatment: Once the underlying condition is corrected, Na+ will shift out of the cells, and hyponatremia will resolve. 10 Hypotonic Hyponatremia Posm < 280 mOsm/L Three classifications: – Hypovolemic – Hypervolemic – Euvolemic 11 Hypovolemic Hypotonic Hyponatremia Characteristics: - Posm 450 mOsm/kg Causes: Renal: Diuretic use [Thiazides, Loop] Extra-renal: GI: vomiting, diarrhea Excessive sweating Cerebral salt wasting Treatment: Restore Na, and fluid via NS and LR If severe symptoms: 3%NS [Hypertonic] 12 Treatment Overview Raise serum sodium at a safe rate, defined as a change no greater than 10–12 mEq/L in 24 hours. Severe or acute onset (24 hours or unknown): Na by 0.5 mEq/L/hour until serum Na reaches 120 mEq/L (max rise of 10 mEq/day Risks of correcting Na+ too quickly: seizure, paralysis, brain herniation, central pontine myelinolysis, death 13  Osmotic demyelination syndrome[Central pontine demyelination] Can occur with rapid correction of sodium The myelin sheath that covers nerve cells is destroyed 14 NaCl Replacement Options 0.9% NaCl Isotonic saline Effectively corrects Na+ and H20 deficits Provides volume resuscitation while correcting Na+ level Most appropriate option for patients with hypovolemia hyponat. 3% NaCl Hypertonic saline (Na+=513 mEq/L) Reserved for severe hyponatremia cases NaCl tablets are not effective as replacement option 15 NaCl Replacement Calculations Step #1 - calculate Na deficit (mEq): Na deficit = TBWater x [target Na - current Na] TBWater = 0.6 L/kg for males; TBW = 0.5 L/kg for females Step #2 - calculate correction volume (L) Correction volume = Na deficit (mEq) / Na solution (mEq/L) 0.9% NaCl = 154 mEq/L 3% NaCl = 513 mEq/L Step #3 – calculate infusion time (hrs) Infusion time = [target Na – current Na+] /correction rate Correction rate is typically = 0.5 – 1.5 mEq/L/hr[will be given] Step #4 – calculate infusion rate (ml/hr) Infusion rate = correction volume (ml) / infusion time (hrs) 16 EXAMPLE: 70 kg male; Na+=110; Target Na+ = 120; (correct at rate of 0.5 mEq/L/hr);Using 0.9% NaCl 1- Na deficit mEq using the equation. TBW = 70kg*0.6L/kg= 42L 42L*(120 mEq-110 mEq)=420 mEq 2- Correction volume = 420 mEq/154 mEq/L= 2.7L 3- Infusion time = [120-110]/0.5mEq/L/hr= 20 hrs 4- Flow rate = 2700 mL/20 hr= 135 mL/hr 17 Hypervolemic Hypotonic Hyponatremia Characteristics: Posm 40 mEq/L Impaired water excretion caused by the inability to suppress secretion of ADH 22 Treatment of SIADH Fluid restriction Sodium tablets +/- furosemide Vasopressin receptor antagonists: promote water [VRA] diuresis while preserving electrolytes: Tolvaptan[ Jynarque]: 15 mg PO daily V2 selective antagonism [ Na+ loss Renal, GI, lung, and skin losses Treatment: Safely correct hypernatremia to 140-150 mEq/L at a rate that restores and maintains brain cell volume by administering 0.9% NaCl until vital signs stable, then free water replacement [D5W], or NS, or 0.45%NS The correction rate should be approximately 1 mEq/L per hour for hypernatremia that developed in less than 48 hours and 0.5 mEq/L per hour for hypernatremia that developed more slowly. 40 Treatment of Hypovolemic Hypernatremia Step #1: select fluid and determine Na content - 0.9% NS ,0.45% NS , D5W - Step #2: calculate H20 deficit (- mEq) - H20 deficit = [Na+ solution – current Na+] / [TBW +1] - Step #3: determine how many liters are needed to decrease Na to goal - Volume (L) = [Current Na+ - Target Na+] / H20 deficit - Step #4: determine how long to run the fluids: - Time (hrs) = [Current Na+ - Target Na+] / correction rate of Na - Step #5: determine how fast to run the fluids: - – Infusion Rate (mL/hr) = volume from Step #3 (ml) / correction time 41 70 kg male; Na+=160; Target Na+ = 145; (correct at rate of 0.5 mEq/L/hr) Step #1: D5W Step #2: calculate H20 deficit (- mEq) – H20 deficit = [0 mEq/L– 160 mEq/L] / [42L +1] = -3.72 mEq Step #3: determine how many liters are needed to decrease sodium to goal – Volume (L) = [160 mEq/L – 145 mEq/L] / 3.72 mEq = 4 L Step #4: determine how long to run the fluids: Time (hrs) = [160 mEq/L – 145 mEq/L] / 0.5 mEq/L/hr = 30 hrs Step #5: determine how fast to run the fluids: – Infusion Rate (mL/hr) = 4L / 30 hrs = 0.133 L/hr = 133 ml/hr 42 Hypervolemic Hypernatremia Causes: Na+ gain > H20 gain :Sodium overload Treatment: - Restore free water deficit : Use D5W as solution and calculate replacement volume and rate using same equations used for hypovolemic hypernatremia Supplement with fluid removal Loop diuretics: – Furosemide 20-40 mg IV q 6 hours May require hemodialysis to remove more water. 43 Euvolemic[isovolemic] Hypernatremia Causes: Osmotic diuresis: Water loss only Diabetes Insipidus [DI] Central diabetes insipidus (decreased AVP secretion) Nephrogenic diabetes insipidus (decreased kidney response to AVP) Patients with untreated DI excrete (3-20 L/day) of dilute urine, resulting in hypernatremia. Lithium, which impairs AVP mediated water transport, is the most common cause of acquired nephrogenic DI. 44 Central Diabetes Insipidus Characteristics: Deficient secretion of antidiuretic hormone Slight rise in sodium (141-145 mEq/L) with urine volumes of 3L/D Treatment: – Desmopressin (DDAVP): vasopressin agonist; increases water permeability in renal tubular cells resulting in decreased urine volume. Dose: 10-20 mcg intranasal once daily Dose titrate to achieve daily urine volume of 1.5-2L and Na of 137-142 mEq/L Adverse Effects: hyponatremia, hypervolemia 45 Nephrogenic Diabetes Insipidus Characteristics: Resistance to antidiuretic hormone produce large amounts of hypotonic urine Decrease in urinary concentrating ability Causes: drugs, hypercalcemia, hypokalemia Treatment: Non-pharmacologic treatment: Na restriction + hypotonic fluids Pharmacologic : Thiazide diuretics: HCTZ 25 mg PO q 12-24 hours Indomethacin 50 mg PO TID Amiloride 5-10 mg PO daily: Directly inhibits uptake of lithium into nephron 46  47 BIG PICTURE HYPERNATREMIA Hypovolemic Hypernatremia – Fluid DOWN – give fluid back to the patient – Utilize calculations to determine how much Hypervolemic Hypernatremia – Na+ and fluid UP – Restore free water and remove excess fluid Euvolemic Hypernatremia – Central diabetes insipidus – Nephrogenic diabetes insipidus 48 THANK YOU! 49