week 4- blood chemistry Flashcards
• What is blood chemistry analysis used for?
o quantify chemical constituents in serum/plasma
o may identify organ damage or morbidity
o usu need results of mult analytes to confirm abn
o Requires knowledge of pathophysiology
• What’s in the different colored tubes, and what are they used for?
o Lavender: EDTA binds Ca2+ (prevents clotting); cell studies lke CBC
o Light Blue: Sodium Citrate binds Ca2+ (preserves clotting factors); coagulation studies such (PT and aPTT)
o Red: clot activators; serum testing (CMP)
• What are the 8 categories of blood analytes?
o Electrolytes: Na+, K+, Cl-, CO2
o Enzymes: AST, ALT, Alkaline phosphatase, GGT, LDH
o Lipids: Cholesterol, Triglycerides, HDL, LDL, VLDL, Lipoprotein(a)
o Metabolic by-products: BUN, NH3, Creatinine, Bilirubin, Uric Acid
o Proteins: Total protein, Albumin, Globulin
o Minerals: Ca, P, Mg
o Carbohydrates: Glucose
o Calculated Values: Anion Gap, A/G Ratio, BUN/Creatinine Ratio, Globulin, etc.
• What blood tests pertain to renal function?
o BUN, Creatinine, Ca2+, P, Glucose, Albumin, Electrolytes
• Which tests may vary by lab?
o BMP/CMP/Renal panel: anion gap, BUN/creat ratio
o CMP: calc osmolality, globulin, A/G ratio
• What does “normal” mean in blood analysis?
o Each lab has own “Normal” values/rr
o varies dt differences in analyzer methods, population, etc.
o Textbooks will also list different ranges
o Also depend on age & gender
• What is the breakdown of solid and fluid composition (TBW) of the body?
o 40% solids (M, F=45%)
o 60% fluids (Total body water, TBW) → 65% ICF, 35% ECF
o 25% interstitial fluid
o 5-8% plasma (intravascular)
o 1-2% transcellular: CSF, intraocular, serous membranes, in GI, respiratory, urinary tracts (3rd space)
• Where does the water we consume come from?
o ~2500 mL total
o 10%- water of metabolism
o 30%- in moist food
o 60%- in beverages
• Where does our water waste leave the body?
o Total 2500 mL o 6%- sweat o 6%- feces o 28%- Skin and lungs o 60% urine
• How is fluid and electrolyte homeostasis maintained in the body?
o Neutral balance: input = output
o Positive balance: input > output
o Negative balance: input < output
• What are examples of solutes (dissolved particles) in blood?
o Electrolytes (charged): Cations (+) Na+, K+ , Ca2+, H+; Anions (-) Cl-, HCO3- , PO43- o Non-electrolytes (Uncharged): proteins, urea, glucose, O2, CO2
• What is the serum osmolality test?
o Measures # dissolved particles in serum per unit volume
o eval fluid and electrolyte imbalances (in sz, ascites, hydration status, acid/base balance)
o detect presence of organic acids, sugars, ethanol
o Calculated w serum Na, glucose, BUN (3 most important solutes in blood )
o = 2(Serum Na) + glucose/18 + BUN/2.8
o rr= 285-295 mOsm/kg
o >385: stupor in hyperglycemia
o 400-420: grand mal sz
o >420: death
• What is isotonic to human blood?
o 9g salt in 1L water= 0.9%
• How does the body react to hypertonic blood?
o Detected by osmoreceptors in hypothalamus, and thirst (angiotensin II) receptors
o → ADH secreted from posterior pituitary (neurohypophysis), ↑ thirst
o ↑ permeability of distal tubules/collecting ducts to water, more water to blood, less to urine
o Results in ↓ blood osmolality
• How does the body react to hypotonic blood?
o Detected by osmoreceptors in hypothalamus, and thirst (angiotensin II) receptors
o Inhibit ADH from PP (NH), ↓ thirst
o ↓ perm distal/collecting ducts to water, more lost in urine
o Results in ↑ blood osmolality
• What are the modes of fluid movement?
o Fluid compartments separated by membranes freely permeable to water
o Osmosis: water moves thru semi-permeable membrane from lo osmolality to hi
o Diffusion: substance (electrolytes) move from higher to lower concentration thru a solution
o Filtration: water and solutes move thru semi-permeable membrane from hi to lo pressure (blood pressure)
o Active transport: move against concentration/electrochemical gradient (Na-K pump)
• What pressure forces are present in arterioles vs venules?
o A: 41.3 mmHg out, 28 in = net 13.3 out
o V: 21.3 out, 28 in = net 6.7 in
• What is edema? Causes? Grades of pitting?
o Accumulated fluid in interstitial space
o ↑hydrostatic P, ↓ plasma osmotic P, ↑capillary membrane permeability, lymphatic channel obstruction
o 1+: 2mm indent (slight), normal contour; interstitial fluid vol 30% above normal
o 2+: 4mm (deeper), last longer, fairly normal contour
o 3+: 6mm (deep), several secs, obvious skin swelling
o 4+: 8mm (deep), last minutes, frank swelling
o Brawny: no pitting dt so much fluid accumulation, firm or hard to palpate; skin surface shiny warm moist
• What are electrolytes? In the body?
o Minerals in blood and tissues give electrical charge to keep heart, kidneys, nerves, organs functioning (Na+, K+, Cl-, Ca2+, Mg2+, HCO3-, PO42-, SO42-)
o Out of balance an cause serious consequences
o Body fluids are electrically neutral, osmotically maintained
• What are a cathode an anode?
o Cathode (-): + cations move to cathode o Anode (+): - anions move to anode
• When should you replace electrolytes?
o Heavy sweating: esp Na, K
o Chronic vomit/diarrhea: esp Na, K, Cl
• What are the relative extracellular and intracellular ratios/values (E:I) of ions?
o Na: 14 (143 mEq/L):1 o K: 1:28 (140) o Ca: 5 (5):1 o Mg: 1:19(58) o Cl: 26(105):1 o HCO3: 3(28):1 o PO4: 1:19(75) o SO4: 1:2(2)
• What is Sodium’s role as an electrolyte?
o 90% of total ECF cations; lo in ICF
o 136 -145 mEq /L
o Pairs with Cl- , HCO3- to neutralize charge
o Most important ion in regulating water balance
o Important in nerve and muscle function
• How are sodium levels maintained in blood?
o dietary intake vs renal excretion o Aldosterone retains Na+ by increasing renal reabsorption o ADH (Vasopressin): from Hypothalamus, cases water retention o RAAS: ↑ Aldosterone & ADH o Natriuretic Peptides: formed in brain (BNP & CNP), heart (ANP), ↑ renal excretion
• How does RAAS work to increase blood Na/volume?
o Sympathetic/hypotension/↓NA →Kidney(JGA) →Renin →angiotensinogen, AI, AII
o AII → cardiac and vascular hypertrophy, systemic vasoconstriction, thirst
o AII → adrenal cortex (aldosterone), pituitary →renal Na and water retention
o → ↑blood vol
• What are normal and critical Na levels?
o Adult/elderly/child: 136-145 mEq/L
o Optimum: 135-142
o Critical: < 120-125, >155
• What happens in hypernatremia? Causes?
o Plasma Na+ > 145; dt ↑ Na + or ↓ water
o Water moves from ICF → ECF, cells dehydrate
o Ssx: thirst, lethargy, neuro dysfunction (dehydrated brain cells), lo vascular vol
o Dt ↑ diet intake, hyperaldosteronism, dehydration, excess sweat, extensive burns, Cushing’s, osmotic diuresis, hi Na+ in IV fluids
o ADH def (DI): collecting ducts can’t reabsorb water
• What are 2 types hyponatremia?
o Na <135, → Na in ECF
o Depletion: Na loss- diuretics, vomit, diarrhea, ↓ aldosterone, ↓Na intake
o Dilution: renal dysfunction w intake of hypotonic fluids, excess sweat→intake lots of pure water
o SIADH (syndrome of inappropriate ADH), oliguric renal failure, severe CHF, ascites, cirrhosis → impair renal excretion water
o Hyperglycemia: attracts water (Na ↓ 1.6-3 for every 100mg/dL ↑ in plasma glucose)
• What are ssx of hyponatremia?
o Neuro: lethargy, HA, confusion, apprehension, depressed reflexes, sz, coma
o Muscle: cramps, weakness, fatigue
o GI: N/V, abdominal cramps, diarrhea
• What is Potassium’s role in the body?
o Major intracellular cation; muscle, RBCs, liver
o nerve conduction, muscle function, acid-base balance, protein synthesis, maintenance of osmotic pressure in blood.
o K+ bicarbonate is the major intracellular buffer
o Controls rate and force of cardiac contraction (with Mg and Ca), CO
• How is K processed by body?
o Normal western diet ~70 mmol/day
o Intestine absorbs nearly 100%
o Processed by liver in hepatoportal circulation
o Almost exclusively excreted by the kidney; minimal excreted by feces
• How are K levels regulated?
o Feedforward: ↑K intake → hepatoportal, gut sensors → CNS → ↑K excretion
o Feedback: ↑K intake AND ↓excretion → ↑plasma K → adrenal cortex, ↑ aldosterone → ↑renal excretion
o K secreted (lost) when Na reabsorbed in renal tubules
o Alkalosis: pH>7.45 = ↓K
o Acidosis: pH<7.35 = ↑K
• How do renal tubules handle lo or hi/norm K intake?
o PT: either, ~67% reabsorbed
o Thick ascending loop: either, ~25% reabsorbed
o DT: lo (3% reab), hi (secretes 10-50%)
o Proximal CD: lo (10% reab), hi (secrete 5-30%)
o Distal CD: lo (1% reab), hi (secretes 15-80%)
• How does K get in and out of cells?
o Out: passive K channels
o In: H-K-ATPase, 1K in, 1H out
o In: Na-K-ATPase, 2K in, 3Na out
