Week 3 Interpreting Common Lab Values Flashcards
What are the common laboratory values that are taken?
- Complete blood count
- Urinalysis
- Clinical Chemistry Panels
- Hydration status
Labs from CBC
- Hemoglobin (120-160 g/L)
- Red blood cells (RBC) (3.8-5.2x 10^12/L)
- Hematocrit (HCT): (0.36-0.46 L/L)
- Mean cell volume (MCV): (78-100 fL)
- Mean cell hemoglobin concentration (MCHC): (310-360 g/L)
- RDW: Red blood cell distribution width (<15.6%)
- White blood cell count (WBC) :4.5-13.5 x10^9/L.
- Platlets: (140-450 x10^9/L)
normal range for hemoglobin
120-160 g/L
normal range for RBCs
3.8-5.2x 10^12/L
normal range for HCT
0.36-0.46 L/L
normal range for MCV
78-100 fL
normal range for MCHC
310-360 g/L
normal range for RDW
<15.6%
normal range for WBC
4.5-13.5 x10^9/L.
normal range for platelets
140-450 x10^9/L
What CBC blood values are important for IDA?
- ↓ hemoglobin: <12 g/dL (120 g/L)
- ↓ hematocrit (hypochromic): <0.35 L/L
- ↓ MCV (microcytic): <80 fL
Various combinations; depending on severity of depletion
When might MCV be high
magoloblastic anemia
* B12/ folate issue
What are the white blood cells with differentials?
granulocytes
* neutrophils
* % eosinophils
* % basophiles
non-granulocytes
* lymphocytes
* monocytes
When might WBCs be increased/ decreased?
- ↑ with infections ,inflammation, cancers, leukemias
- ↓ with some autoimmune conditions, bone marrow suppression, and some medications like methotrexate
Importance of urinalysis in screening
- To rule out a variety of disorders: infection, diabetes mellitus, renal disease, inborn errors of metabolism etc. Includes testing for presence of glucose, protein, RBC, bacteria etc.
- To assess over all hydration: urine specific gravity, pH important
- Can be prognostic for liver diseases when find high levels of bilirubin in urine
What is assessed in the urinalysis?
How doe specific gravity in the urinalysis change with dehydration?
dehydration = higher
* means higher concentration
What values are assessed in the blood chemistry?
- Electrolytes: Na+, K+, Cl-, HCO3 or total CO2
- Glucose
- Creatinine, Urea (BUN)
- Will often include: AST/ALT, total bilirubin, calcium, phosphorus, magnesium
- May include: cholesterol, TG and CRP
What are the conditions of low/ high sodium?
- hyponatremia (<130 mmol/L)
- hypernatremia (>145 mmol/L)
Describe hyponatremia
<130 mmol/L
* Can be due to ↑ sodium losses (renal, GI etc), fluid overload/retention (due to liver diseases),
* chronically low sodium intake (IV administration) and/or excessive fluid administration
* diuretic therapy that causes sodium wasting,
* excessive ADH secretion (common in head trauma) leading to fluid retention
* CF sweat a lot and so lose excessive sodium (diagnostic criteria)
Describe hypernatremia
> 145 mmol/L
* Most typically occurs in dehydration; rarely in excessive intake (possible via IV administration).
* Other diseases: Cushing Syndrome or Diabetes Insipidus (affects cortisol and adrenal gland function)
What are the conditions of low/high potassium?
- Hypokalemia (< 3.5 mmol/L)
- Hyperkalemia (> 5mmol/L)
Describe hypokalemia
< 3.5 mmol/L
* ↑renal losses (diuresis)
* ↑GI losses (diarrhea, vomiting, fistula)
* K+ wasting meds (thiazide and loop diuretics, etc)
* Shift into cells (anabolism, refeeding syndrome, correction of glucosuria or diabetic ketoacidosis)
* Inadequate intake
Describe hyperkalemia
> 5mmol/L (worried at 6 mmol/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)
Describe urea
Reflective of hydrational status, renal function and recent protein intakes
* Typically elevated in renal disease (creatinine would also be elevated as well) or in dehydration
* May be high if fed lots of protein intake; may be low with chronically low intakes of protein
Describe creatinine
High levels reflective of renal damage, recent skeletal protein breakdown (not chronic where levels would be low).
normal values for urea and creatinine
- urea: 3.7 mmol/L
- creatinine: 40-110 mmol/L
low versus high 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
Symptoms of dehydration
- dry skin and mucous membrane, poor skin turgor, sunken eyeballs
- orthostatic hypotension, central venous and pulmonary pressures all ↓
- ↑HR/ ↓Cardiac output
- rapid weight loss (may be several kg)
- ↓ urinary output/ ↑ urine specific gravity
- elevated serum osmolality; ↑serum sodium, ↑urea
- cool & clammy
Clinical conditions where dehydration may occur
- rapid blood loss with trauma
- high output fistulas in GI in short bowel patients
treatment for dehydration
Fluid resuscitation: with fluids of similar concentration to restore blood volume/blood pressure
* Usually isotonic fluid like normal saline or lactated Ringer’s solution given IV
* consider electrolyte status (Na+, K+, Cl- ) in choice of solution.
* TPN or enteral nutrition is NEVER USED to TREAT!
What can lead to overhydration or edema?
- Caused by increase in capillary hydrostatic pressure or permeability
- Decrease in colloid osmotic pressure
- Physical inactivity (need PA to help push fluid in the venous system)
fluid retention versus excessive intake with overhydration
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 (big issue in renal or liver disease)
Symptoms of overhydration
- Generalized edema/Pitting edema: leaves depression in skin when touched
- Rapid weight gain (> 2-3 kg in short period of time)
- Pulmonary edema: crackles on auscultation
- Patient SOB with tachypnea, systemic BP may rise and then fall with cardiac failure.
- Labs: low hematocrit, normal serum sodium, lower K+ and BUN (or if high, may mean renal failure)
What does ND set with overhydration?
MD will set very tight TFI (may be 80 or 90% maintenance or lower)
Sodium lab value changes with hydration status
- hypovolemia: typically ↑ but can be normal or ↓
- hypervolemia: ↓
- other factors influencing result: Serum sodium generally reflects hydrational status; not sodium balance or overall status (need urine collections for this).
urine sp. gravity changes with hydration status
normal: 1.010-1.025
* hypovolemia: ↑
* hypervolemia: ↓
urine osmolality changes with hydration status
normal: 200-1200 mosm/kg
* hypovolemia: ↑
* hypervolemia: ↓
other factors influencing result:
* Low: diuresis, hyponatremia, sickle cell anemia;
* High: SIADH, azotemia,
BUN changes with hydration status
normal: 3-7 mmol/L
* hypovolemia: ↑
* hypervolemia: ↓
other factors influencing result:
* Low: inadequate dietary protein, severe liver failure
* High: pre-renal failure; excessive protein intake, GI bleeding, catabolic state, glucocorticoid therapy
* creatinine may also rise in severe hypovolemia (but not good marker)
serum albumin changes with hydration status
normal:
* hypovolemia: ↑
* hypervolemia: ↓
other factors influencing result:
* Low: malnutrition; acute phase response, liver failure
* High: rare except in hemoconcentration
HCT changes with hydration status
normal: M-42-52%; F-37-47%
* hypovolemia: ↑
* hypervolemia: ↓
other factors influencing result:
* Low: anemia, hemorrhage with subsequent hemodilution (occurring after approximately 12 hours)
* High: chronic hypoxia (chronic pulmonary disease, living at high altitude, heavy smoking, recent transfusion)
