Hyponatremia

Hyponatremia
By :
James Yost, MD, MS, MBA
Emory Family Medicine

Hyponatremia
* Definition
* Epidemiology
* Physiology
* Pathophysiology
* Types
* Clinical Manifestations
* Diagnosis
* Treatment

Hyponatremia
* Definition:
o Commonly defined as a serum sodium concentration 135 meq/L
o Hyponatremia represents a relative excess of water in relation to sodium.
* Epidemiology:
o Frequency
+ Hyponatremia is the most common electrolyte disorder
+ incidence of approximately 1%
+ prevalence of approximately 2.5%
+ surgical ward, approximately 4.4%
+ 30% of patients treated in the intensive care unit
o Mortality/Morbidity
+ Acute hyponatremia (developing over 48 h or less) are subject to more severe degrees of cerebral edema
# sodium level is less than 105 mEq/L, the mortality is over 50%
+ Chronic hyponatremia (developing over more than 48 h) experience milder degrees of cerebral edema
# Brainstem herniation has not been observed in patients with chronic hyponatremia
o Age
+ Infants
# fed tap water in an effort to treat symptoms of gastroenteritis
# Infants fed dilute formula in attempt to ration
+ Elderly patients with diminished sense of thirst, especially when physical infirmity limits independent access to food and drink
* Physiology
o Serum sodium concentration regulation:
+ stimulation of thirst
+ secretion of ADH
+ feedback mechanisms of the renin-angiotensin-aldosterone system
+ renal handling of filtered sodium
o Stimulation of thirst
+ Osmolality increases
# Main driving force
# Only requires an increase of 2% - 3%
+ Blood volume or pressure is reduced
# Requires a decrease of 10% - 15%
+ Thirst center is located in the anteriolateral center of the hypothalamus
# Respond to NaCL and angiotensin II
o Secretion of ADH
+ Synthesized by the neuroendocrine cells in the supraoptic and paraventricular nuclei of the hypothalamus
+ Triggeres:
# Osmolality of body fluids
* A change of about 1%
# Volume and pressure of the vascular system
+ Increases the permeability of the collecting duct to water and urea
o renin-angiotensin-aldosterone
+ Renin
# Stemuli are perfusion pressure, sympathetic activity, and NaCl delivery to the macula densa
# Increase in NaCl delivery to the macula decreases the GFR by decrease in the renin secretion
+ Aldosterone
# Reduces NaCl excretion by stimulating it’s resorption
* Ascending loop of Henle
* Distal tubule
* Collecting duct
o extracellular-fluid and intracellular-fluid compartments make up 40 percent and 60 percent of total body water
o renal handling of water is sufficient to excrete as much as 15-20 L of free water per day
o sodium is the predominant osmole in the extracellular fluid (ECF) compartment and serum

* Pathophysiology
o hyponatremia can only occur when some condition impairs normal free water excretion
o acute drop in the serum osmolality:
+ neuronal cell swelling occurs due to the water shift from the extracellular space to the intracellular space
+ Swelling of the brain cells elicits 2 responses for osmoregulation, as follows:
# It inhibits ADH secretion and hypothalamic thirst center
# immediate cellular adaptation
* Types
o Hypovolemic hyponatremia
o Euvolemic hyponatremia
o Hypervolemic hyponatremia
o Redistributive hyponatremia
o Pseudohyponatremia
Hypovolemic hyponatremia
* develops as sodium and free water are lost and/or replaced by inappropriately hypotonic fluids
* Sodium can be lost through renal or non-renal routes
* Nonrenal loss
o GI losses
+ Vomiting, Diarrhea, fistulas, pancreatitis
o Excessive sweating
o Third spacing of fluids
+ ascites, peritonitis, pancreatitis, and burns
o Cerebral salt-wasting syndrome
+ traumatic brain injury, aneurysmal subarachnoid hemorrhage, and intracranial surgery
+ Must distinguish from SIADH
* Renal Loss
o Acute or chronic renal insufficiency
o Diuretics

Euvolemic hyponatremia
* Normal sodium stores and a total body excess of free water
o Psychogenic polydipsia, often in psychiatric patients
o Administration of hypotonic intravenous or irrigation fluids in the immediate postoperative period
o administration of hypotonic maintenance intravenous fluids
o Infants who may have been given inappropriate amounts of free water
o bowel preparation before colonoscopy or colorectal surgery
* SIADH
o downward resetting of the osmostat
o Pulmonary Disease
+ Small cell, pneumonia, TB, sarcoidosis
o Cerebral Diseases
+ CVA, Temporal arteritis, meningitis, encephalitis
o Medications
+ SSRI, Antipsychotics, Opiates, Depakote, Tegratol

* Total body sodium increases, and TBW increases to a greater extent.
* Can be renal or non-renal
o acute or chronic renal failure
+ dysfunctional kidneys are unable to excrete the ingested sodium load
o cirrhosis, congestive heart failure, or nephrotic syndrome

Redistributive hyponatremia
o Water shifts from the intracellular to the extracellular compartment, with a resultant dilution of sodium. The TBW and total body sodium are unchanged.
+ This condition occurs with hyperglycemia
+ Administration of mannitol
* Pseudohyponatremia
o The aqueous phase is diluted by excessive proteins or lipids. The TBW and total body sodium are unchanged.
+ hypertriglyceridemia
+ multiple myeloma
* Clinical Manifestations
o most patients with a serum sodium concentration exceeding 125 mEq/L are asymptomatic
o Patients with acutely developing hyponatremia are typically symptomatic at a level of approximately 120 mEq/L
o Most abnormal findings on physical examination are characteristically neurologic in origin
o patients may exhibit signs of hypovolemia or hypervolemia
* Diagnosis
o CT head, EKG, CXR if symptomatic
o Repeat Na level
o Correct for hyperglycemia
o Laboratory tests provide important initial information in the differential diagnosis of hyponatremia
+ Plasma osmolality
+ Urine osmolality
+ Urine sodium concentration
+ Uric acid level
+ FeNa
o Plasma osmolality
+ normally ranges from 275 to 290 mosmol/kg
+ If >290 mosmol/kg :
# Hyperglycemia or administration of mannitol
+ If 275 – 290 mosmol/kg :
# hyperlipidemia or hyperproteinemia
+ If <275 mosmol/kg :
# Eval volume status
o Plasma osmolality < 275 mosmol/kg
+ Increased volume:
# CHF, cirrhosis, nephrotic syndrome
+ Euvolemic
# SIADH, hypothyroidism, psychogenic polydipsia, beer potomania, postoperative states
+ Decreased volume
# GI loss, skin, 3rd spacing, diuretics
o Urine osmolality
+ Normal value is > 100 mosmol/kg
+ Normal to high:
# Hyperlipidemia, hyperproteinemia, hyperglycemia, SIADH
+ < 100 mosmol/kg
# hypoosmolar hyponatremia
* Excessive sweating
* Burns
* Vomiting
* Diarrhea
* Urinary loss
o Urine Sodium
+ >20 mEq/L
# SIADH, diuretics
+ <20 mEq/L
# cirrhosis, nephrosis, congestive heart failure, GI loss, skin, 3rd spacing, psychogenic polydipsya
o Uric Acid Level
+ < 4 mg/dl consider SIADH
o FeNa
+ Help to determine pre-renal from renal causes
* Treatment
o four issues must be addressed
+ Asyptomatic vs. symptomatic
+ acute (within 48 hours)
+ chronic (>48 hours)
+ Volume status
o 1st step is to calculate the total body water
+ total body water (TBW) = 0.6 × body weight
o next decide what our desired correction rate should be
o Symptomatic
+ immediate increase in serum Na level by 8 to 10 meq/L in 4 to 6 hours with hypertonic saline is recommended
o acute hyponatremia
+ more rapid correction may be possible
# 8 to 10 meq/L in 4 to 8 hours
o chronic hyponatremia
+ slower rates of correction
# 12 meq/L in 24 hours

* Symptomatic or Acute
o Treatment Cont. - Here comes the Math!!!
+ estimate SNa change on the basis of the amount of Na in the infusate
+ ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)
# ΔSNa is a change in SNa
# [Na + K]inf is infusate Na and K concentration in 1 liter of solution
o OH MY GOD, what did he just say!!!!!!!!!!!!!!!!!!

* IV Fluids
o One liter of Lactated Ringer's Solution contains:
+ 130 mEq of sodium ion = 130 mmol/L
+ 109 mEq of chloride ion = 109 mmol/L
+ 28 mEq of lactate = 28 mmol/L
+ 4 mEq of potassium ion = 4 mmol/L
+ 3 mEq of calcium ion = 1.5 mmol/L
o One liter of Normal Saline contains:
+ 154 mEq/L of Na+ and Cl−
o One liter of 3% saline contains:
+ 514 mEq/L of Na+ and Cl−

* Example:
o a 60 kg women with a plasma sodium of 110 meq/L
o Formula:
+ ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)
o What is the TBW?
o How high will 1 liter of normal saline raise the plasma sodium?
* Answer:
o TBW is 30 L
o Serum sodium will increase by approximately 1.4 meq/L for a total SNa of 111.4 meq/L

* Example:
o a 90 kg man with a plasma sodium of 110 meq/L
o Formula:
+ ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)
o What is the TBW?
o How high will 1 liter of 3% saline raise the plasma sodium?
* Answer:
o TBW is 54 L
o Serum sodium will increase by approximately 7.3 meq/L for a total SNa of 117.3 meq/L

* Asymptomatic or Chronic
o SIADH
+ response to isotonic saline is different in the SIADH
+ In hypovolemia both the sodium and water are retained
+ sodium handling is intact in SIADH
+ administered sodium will be excreted in the urine, while some of the water may be retained
# possible worsening the hyponatremia

Hyponatremia

* Asypmtomatic or Chronic
o SIADH
+ Water restriction
# 0.5-1 liter/day
+ Salt tablets
+ Demeclocycline
# Inhibits the effects of ADH
# Onset of action may require up to one week

* Example:
+ 85 y/o male with weakness and head ache
+ SNa is 118 mEq/L
+ Plasma osmolality is 254 mosmol/kg
+ Urine osmolality is 130 mosmol/kg
+ Urine sodium >20 mEq/L
+ Uric acid is 3mg/dl
o What type of hyponatremia does this patient have?
o What additional labs/studies would you want?

* Example Cont.:
o Noncontrast CT Head:
* Tx
o Call Neurology and neurosurgery
o Free water restriction

* Example:
o 63 y/o female at 75 Kg with N/V/D for 4 days
o SNa is 108 mEq/L
o She has had one seizure in the ambulance
# Plasma osmolality is 251 mosmol/kg
# Urine osmolality is 47 mosmol/kg
# Uric acid is 6mg/dl
o What type of hyponatremia does this patient have?
o What additional labs/studies would you want?
* How will you Tx her?
o Calculate the total body water
+ 0.5 x weight = 37.5 L
o What rate of correction do you want?
+ 8 to 10 mEq/L in 6 to 8 hours
o What fluid will you use?
+ 3% Saline
o How will you calculate the amount of sodium to give her?
+ ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)
o How will her sodium increase after 1 liter of 3% saline?
+ By 10.8 mEq/L to 118.8 mEq/L

* What other medication will she need?
o Lasix and a foley
* Her sodium increases to 118.8 mEq/L over the next 8-10 hours. How will you continue to correct her hyponatremia?
o ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1)
o ΔSNa = 154mEq/L – 118.8mEq/L ÷ 38.5L = 0.9 mEq/L
* So 2 liters of normal saline over the next 14 hours

Hyponatremia.ppt

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Fluid, Electrolyte & Acid-Base Balance

Fluid, Electrolyte & Acid-Base Balance

Body Fluids
* Your body is 66% water
* Not evenly distributed – separated into compartments
* Able to move back and forth thru the cell membranes to maintain an equilibrium

Fluid Compartments
* Intracellular fluid – fluid inside cells [ICF]
* Extracellular fluid – fluid outside cells and all other body fluids --- ž is plasma [intravascular fluid], remaining ū is interstitial fluid. Small amount is localized as CSF, serous fluid, synovial fluid, humors of eye & endo/perilymph of ears

Edema
* Condition in which fluid accumulates in the interstitial compartment. Sometimes due to blockage of lymphatic vessels or by a lack of plasma proteins or sodium retention

Fluid Balance
* Amount in = amount out
* Average daily intake is 2500 ml [ fluids, food and metabolic water]
* Average daily output is 2500 ml [ urine, feces, perspiration, insensible perspiration]
* What can throw off these numbers?

Electrolyte Balance
* Def: - concentration of individual electrolytes in the body fluid compartments is normal and remains relatively constant.
* Electrolytes are dissolved in body fluids
* Sodium predominant extracellular cation, and chloride is predominant extracellular anion. Bicarbonate also in extracellular spaces
* Potassium is the predominant intracellular cation and phosphates are the predominant intracellular anion
* Cations are actively reabsorbed, anions passively follow by electrochemical attraction
* Aldosterone works at kidney tubules to regulate sodium & potassium levels
* Because of sodium and potassium influence, water will move between compartments
* Example: if high [sodium], then water will move from intracellular space to extracellular space due to osmotic pressure

Balance of other Electrolytes
* Calcium – hypercalcemia / hypocalcemia
* Magnesium – hypermagnesemia/ hypomagnesemia
* Phosphate – hyperphosphatemia/ hypophosphatemia
* Chloride – hyperchloremia/ hypochloremia
Acid - Base Balance
* Blood - normal pH of 7.2 – 7.45
* < 7.2 = acidosis > 7.45 = alkalosis
* 3 buffer systems to maintain normal blood pH
* Buffers
* Removal of CO2 by lungs
* Removal of H+ ions by kidneys
Buffers
* Protein Buffer Systems
* Amino Acid buffers
* Hemoglobin buffers
* Plasma Protein buffers
* Phosphate Buffer Systems
* Carbonic Acid – Bicarbonate Buffer System
Maintenance of Acid-Base Balance
* Respiratory System: removal of CO2 by lungs – stabilizes the ECF, has direct effect on Carbonic Acid – Bicarbonate Buffer System

* Urinary System: removal of H+ ions by kidneys

Disturbances to Acid-Base Balance
* Respiratory Acidosis
* Respiratory Alkalosis
* Metabolic Acidosis [ lactic acidosis, ketoacidosis]
* Metabolic Alkalosis

Fluid, Electrolyte & Acid-Base Balance.ppt

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Evaluation of Laboratory Data in Nutrition Assessment

Evaluation of Laboratory Data in Nutrition Assessment
By:Cinda S. Chima, MS, RD

Laboratory Data and the NCP
* Used in nutrition assessment (a clinical sign supporting nutrition diagnosis)
* Used in Monitoring and Evaluation of the patient response to nutritional intervention

Specimen Types
* Serum: the fluid from blood after blood cells and clot removed
* Plasma: fluid from blood centrifuged with anticoagulants
* Erythrocytes: red blood cells
* Leukocytes: white blood cells
* Other tissues: scrapings and biopsy samples
* Urine: random samples or timed collections
* Feces: random samples or timed collections
* Less common: saliva, nails, hair, sweat

Interpretation of Routine Medical Laboratory Tests
* Clinical Chemistry Panels
o Basic metabolic panel
o Comprehensive metabolic panel
* Complete blood count
* Urinalysis
* Hydration status

Clinical Chemistry Panels: Basic Metabolic Panel (BMP)
Also called Chem 7
Includes
o Electrolytes: Na+, K+, Cl-, HCO3 or total CO2
o Glucose
o Creatinine
o BUN
Basic Metabolic Panel Charting Shorthand
Creatinine
CO2
K+
glucose
BUN
Cl
Na
BMP
Clinical Chemistry Panels: Comprehensive Metabolic Panel
Includes
* BMP except CO2
* Albumin
* Serum enzymes (alkaline phosphatase, AST [SGOT], ALT [SGPT]
* Total bilirubin
* Total calcium
Phosphorus, total cholesterol and triglycerides often ordered with the CMP

Clinical Chemistry Panels:
Complete Blood Count (CBC)
* Red blood cells
* Hemoglobin concentration
* Hematocrit
* Mean cell volume (MCV)
* Mean cell hemoglobin (MCH)
* Mean cell hemoglobin concentration (MCHC)
* White blood cell count (WBC)
* Differential: indicates percentages of different kinds of WBC

Clinical Chemistry Panels: Urinalysis
Negative
Leukocyte esterage
Negative
Nitrite
0.1-1 units/dl
Urobilinogen
Not detected
Bilirubin
Negative
Blood
Negative
Ketones
Not detected
Glucose
2-8 mg/dl
Protein
6-8 (normal diet)
pH
1.010-1.025 mg/ml
Specific gravity
Types of Assays
* Static assays: measures the actual level of the nutrient in the specimen (serum iron, white blood cell ascorbic acid)
* Functional Assays: measure a biochemical or physiological activity that depends on the nutrient of interest (serum ferritin, TIBC)
o (Functional assays are not always specific to the nutrient)

Assessment of Nutrient Pool
Assessment of Hydration Status
* Dehydration: a state of negative fluid balance caused by decreased intake, increased losses, or fluid shifts
* Overhydration or edema: increase in extracellular fluid volume; fluid shifts from extracellular compartment to interstitial tissues
o Caused by increase in capillary hydrostatic pressure or permeability
o Decrease in colloid osmotic pressure
o Physical inactivity
* Use laboratory and clinical data to evaluate pt

Hypovolemia
Isotonic fluid loss from the extracellular space caused by
* Fluid loss (bleeding, fistulas, nasogastric drainage, excessive diuresis, vomiting and diarrhea)
* Reduced fluid intake
* Third space fluid shift, when fluid moves out of the intravascular space but not into intracellular space (abdominal cavity, pleural cavity, pericardial sac) caused by increased permeability of the capillary membrane or decrease on plasma colloid osmotic pressure

Symptoms of Hypovolemia
* Orthostatic Hypotension (caused by change in position)
* Central venous and pulmonary pressures 
* Increased heart rate
* Rapid weight loss
* Decreased urinary output
* Patient cool, clammy
* Decreased cardiac output
* Ask the medical team!!
Treatment of Hypovolemia
* Replace lost fluids with fluids of similar concentration
* Restores blood volume and blood pressure
* Usually isotonic fluid like normal saline or lactated Ringer’s solution given IV
* Excess of isotonic fluid (water and sodium) in the extracellular compartment
* Osmolality is usually not affected since fluid and solutes are gained in equal proportion
* Elderly and those with renal and cardiac failure are at risk

Causes of Hypervolemia
* Results from retention or excessive intake of fluid or sodium or shift in fluid from interstitial space into the intravascular space
* Fluid retention: renal failure, CHF, cirrhosis of the liver, corticosteroid therapy, hyperaldosteronism
* Excessive intake: IV replacement tx using normal saline or Lactated Ringer’s, blood or plasma replacement, excessive salt intake
* Fluid shifts into vasculature caused by remobilization of fluids after burn tx, administration of hypertonic fluids, use of colloid oncotic fluids such as albumin

Symptoms of Hypervolemia
* No single diagnostic test, so signs and symptoms are key
* Cardiac output increases
* Pulse rapid and bounding
* BP, CVP, PAP and pulmonary artery wedge pressure rise
* As the heart fails, BP and cardiac output drop
* Distended veins in hands and neck
* Anasarca: severe, generalized edema
* Pitting edema: leaves depression in skin when touched
* Pulmonary edema: crackles on auscultation
* Patient SOB and tachypneic
* Labs: low hematocrit, normal serum sodium, lower K+ and BUN (or if high, may mean renal failure)
* ABG: low O2 level, PaCO2 may be low, causing drop in pH and respiratory alkalosis

Treatment of Hypervolemia
* Restriction of sodium and fluid intake
* Diuretics to promote fluid loss; morphine and nitroglycerine to relieve air hunger and dilate blood vessels; digoxin to strengthen heart
* Hemodialysis or CAVH

Dehydration
* Excessive loss of free water
* Loss of fluids causes an increase in the concentration of solutes in the blood (increased osmolality)
* Water shifts out of the cells into the blood
* Causes: prolonged fever, watery diarrhea, failure to respond to thirst, highly concentrated feedings, including TF

Symptoms of Dehydration
* Thirst
* Fever
* Dry skin and mucus membranes, poor skin turgor, sunken eyeballs
* Decreased urine output
* Increased heart rate with falling blood pressure
* Elevated serum osmolality; elevated serum sodium; high urine specific gravity
* Use hypotonic IV solutions such as D5W
* Offer oral fluids
* Rehydrate gradually

Laboratory Values and Hydration: BUN
Low: inadequate dietary protein, severe liver failure
High: prerenal failure; excessive protein intake, GI bleeding, catabolic state; glucocorticoid therapy
Creatinine will also rise in severe hypovolemia
Decreases
Increases
BUN
Normal: 10-20 mg/dl
Other factors influencing result
Hyper-volemia
Hypo-volemia
Lab Test
Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.
Laboratory Values and Hydration Status: BUN:Creatinine Ratio
Low: inadequate dietary protein, severe liver failure
High: prerenal failure; excessive protein intake, GI bleeding, catabolic state; glucocorticoid therapy
Decreases
Increases
BUN: creatinine ratio
Normal: 10-15:1
Other factors influencing result
Hyper-volemia
Hypo-volemia
Lab Test
Laboratory Values and Hydration: HCT
Low: anemia, hemorrhage with subsequent hemodilution (occurring after approximately 12-24 hours)
High: chronic hypoxia (chronic pulmonary disease, living at high altitude, heavy smoking, recent transfusion)
Laboratory Values and Hydration: Alb, Na+
Serum sodium generally reflects fluid status and not sodium balance Serum albumin
Other factors influencing result
Hyper-volemia
Hypo-volemia
Lab Test
Laboratory Values and Hydration Status
Low: diuresis, hyponatremia, sickle cell anemia
High: SIADH, azotemia,
Urine osmolality (200-1200 mosm/kg)
Urine sp. Gravity
1.003-1.030
Serum osmolality
(285-295 mosm/kg)
Other factors influencing result
Serum sodium
Low: malnutrition; acute phase response, liver failure
High: rare except in hemoconcentration
Serum albumin
Other factors influencing result
Hyper-volemia
Hypo-volemia
Lab Test
Hypokalemia (K+< 3.5 mEq/L)
* ↑ renal losses (diuresis)
* ↑ GI losses (diarrhea, vomiting, fistula)
* K+ wasting meds (thiazide and loop diuretics, etc)
* Shift into cells (anabolism, refeeding, correction of glucosuria or DKA)
* Inadequate intake
Hyperkalemia (K+>5.0 mEq/L)
* Decreased renal excretion as in acute or chronic renal failure
* Medications, e.g. potassium sparing diuretics, beta blockers, ACE inhibitors
* Shift out of cells (acidosis, tissue necrosis, GI hemorrhage, hemolysis)

Serum Calcium
* Normal serum 9.0-10.5 mg/dL (includes ionized calcium and calcium bound to protein, primarily albumin, and ions)
* Ionized calcium: 4.5-5.6 mg/dL
* Normal levels maintained by hormonal regulation using skeletal reserves
* Ionized calcium is more accurate, especially in pt with hypoalbuminemia; evaluate before repleting Ca+
Hypocalcemia (serum calcium <9.0 mg/dL; ionized Ca+ <4.5 mg/dL)
* Hypoalbuminemia
* Hypoparathyroidism
* Hypomagnesemia
* Renal failure, renal tubular necrosis
* Vitamin D deficiency or impaired metabolism

Hypercalcemia (serum calcium >10.5 mg/dL; ionized Ca+ >5.6 mg/dL)
* Hyperparathyroidism
* Some malignancies, especially breast, lung, kidney; multiple myeloma, leukemia, lymphoma
* Medications: thiazide diuretics, lithium, vitamin A toxicity
* Immobilization
* Hyperthyroidism
Serum Phosphorus (normal 3.0-4.5 mg/dL)

* Serum phos a poor reflection of body stores because <1% is in ECF
* Bones serve as a reservoir
Hypophosphatemia (<3.0 mg/dL)

* Impaired absorption (diarrhea, Vitamin D deficiency, impaired metabolism)
* Medications: phosphate binding antacids, sucralfate, insulin, steroids)
* Alcoholism, especially during withdrawal
* Intracellular shifts in alkalosis, anabolism, neoplasms
* Refeeding syndrome
* Increased losses: hyperparathyroidism, renal tubular defects, DKA recovery, hypomagnesemia, diuretic phase of ATN




Charney and Malone, 2004, p. 93





Hyperphosphatemia (>4.5 mg/dL)

* Decreased renal excretion: acute or chronic renal failure (GFR<20-25 mL/min); hypoparathyroidism
* Increased cellular release: tissue necrosis, tumor lysis syndrome
* Increased exogenous phosphorus load or absorption, phosphorus containing laxatives or enemas, vitamin D excess
* Acidosis
Hypomagnesemia <1.3 mEq/L (normal 1.3-2.1 mEq/L)
* Decreased absorption: prolonged diarrhea, intestinal or biliary fistula, intestinal resection or bypass, steatorrhea, ulcerative colitis; upper GI fluid loss, gastric suctioning, vomiting
* Renal losses: osmotic diuresis, DM with glucosuria, correction of DKA, renal disease with magnesium wasting, hypophosphatemia, hypercalcemia, hyperthyroidism
* Alcoholism
* Inadequate intake: malnutrition
* Medications
* Intracellular shift: acute pancreatitis
* Refeeding syndrome
Hypermagnesemia (>2.1 mEq/L)
* Acute or chronic renal failure
Assessment for Protein-Calorie Malnutrition
* Hormonal and cell-mediated response
to stress
o Negative acute-phase respondents
o Positive acute-phase respondents
* Nitrogen balance
Assessment for Protein-Calorie Malnutrition–cont’d
* Hepatic transport proteins
o Albumin
o Transferrin
o Prealbumin
o Retinol-binding protein
o C-reactive protein
o Creatinine
* Immunocompetence
Hormonal and Cell-Mediated Response to Inflammatory Stress
* Acute illness or trauma causes inflammatory stress
* Cytokines (interleukin-1, interleukin-6 and tumor necrosis factor) reorient hepatic synthesis of plasma proteins
* Although protein-energy malnutrition can occur simultaneously, interpretation of plasma proteins is problematic

Hormonal and Cell-Mediated Response to Inflammatory Stress
* Negative acute-phase respondents (albumin, transthyretin or prealbumin, transferrin, retinol-binding protein) decrease
* Positive acute-phase reactants (C-reactive protein, orosomucoid, fibrinogen) increase
* The change in these proteins is proportional to the physiological insult

Nitrogen Balance Studies
* Oldest biochemical technique for assessment protein status
* Based on the fact that 16% of protein is nitrogen
* Nitrogen intake is compared to nitrogen output, adjusted for insensible losses (skin, hair loss, sweat)
* Nitrogen balance in healthy adults is 0
* Nitrogen balance is positive in growing children, pregnant women, adults gaining weight or recovering from illness or injury
* Nitrogen balance is negative during starvation, catabolism, PEM
* Nitrogen balance = nitrogen intake (g/24 hours) –(urinary nitrogen [g/24 hours) + 2 g/24 hours
* Use correction of 4 g/24 hours if urinary urea nitrogen is used
* Nitrogen intake = (grams protein/24 hours)/6.25
Nitrogen Balance Challenges
* Urea nitrogen is highly variable as a percent of total nitrogen excreted
* It is nearly impossible to capture an accurate nitrogen intake for patients taking food po
* Most useful in evaluating the appropriateness of defined feedings, e.g. enteral and parenteral feedings

Visceral Proteins:
Serum Albumin
* Reference range: 3.5-5.2 g/dl
* Abundant in serum, stable (half-life 3 weeks)
* Preserved in the presence of starvation (marasmus)
* Negative acute phase reactant (declines with the inflammatory process)
* Large extravascular pool (leaves and returns to the circulation, making levels difficult to interpret)
* Therefore, albumin is a mediocre indicator of nutritional status, but a very good predictor of morbidity and mortality
Visceral Proteins: Plasma Transferrin

* Reference range: 200-400 mg/dl
* Half-life: 1 week
* Negative acute phase respondent
* Increases when iron stores are depleted so affected by iron status as well as protein-energy status
* Responds too slowly to be useful in an acute setting
Visceral Proteins: Transthyretin (Prealbumin)
* Reference range: 19-43 mg/dl
* Half-life: 2 days
* Negative acute-phase reactant
* Zinc deficiency reduces levels
* Due to short half-life, it is useful in monitoring improvements in protein-energy status if baseline value is obtained near the nadir as inflammatory response wanes
Visceral Proteins: Retinol-Binding Protein
* Reference range: 2.1-6.4 mg/dl
* Half-life: 12 hours
* Negative acute-phase protein
* Unreliable when vitamin A (retinol) status is compromised
* Elevated in the presence of renal failure, regardless of PEM status

Visceral Proteins: C-Reactive Protein
* Positive acute-phase reactant
* Increases within 4-6 hours of injury or illness
* Can be used to monitor the progress of the stress reaction so aggressive nutrition support can be implemented when reaction is subsiding
* Mildly elevated CRP may be a marker for increased risk for cardiovascular disease
Inflammation
* hs-CRP
* Homocysteine

Urinary Creatinine
* Formed from creatine, produced in muscle tissue
* The body’s muscle protein pool is directly proportional to creatinine excretion
* Skeletal muscle mass (kg) = 4.1 = 18.9 x 24-hour creatinine excretion (g/day)
* Confounded by meat in diet
* Requires 24-hour urine collection, which is difficult
Markers of Malabsorption
* Fecal fat
* Fat-soluble vitamins
* Vitamin D
Lipid Indices of Cardiovascular Risk
* Total cholesterol
* LDL
* HDL: HDL2a, HDL2b, HDL2c, HDL3a, HDLdb
* IDL
* VLDL
* Lp(a)
Nutrition Diagnoses and Laboratory Indices
* Nutrition-related labs can be used either as diagnostic labels or a clinical sign
Examples of Nutrition Diagnostic Statements Related to Lab Values
* Altered nutrition-related lab values (NC-2.2) related to excessive intake of saturated fat and cholesterol and genetic factors as evidenced by diet history and client history.
* Inappropriate intake of food fats (saturated fat and cholesterol) (NI-5.6.3) related to frequent use of baked goods and fried foods as evidenced by diet history and elevated LDL and TC
Examples of Nutrition Diagnostic Statements Related to Lab Values

* Excessive carbohydrate intake related to evening visits to Coldstone Creamery as evidenced by HS blood glucose and diet history

Evaluation of Laboratory Data in Nutrition Assessment.ppt

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