IHS Acid-Base

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Anonymous
ID:
276746
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IHS Acid-Base
Updated:
2014-06-13 12:00:07
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IHS
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IHS
Description:
IHS Acid-Base/Blood Gas Analysis
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  1. Oxygenation and ventilation problems are assessed by how many abnormal variables?
    one
  2. Acid-Base disorders are assessed by how many variables?
    2+
  3. pH is _____ related to [H+]
    inversely
  4. What does a negative base excess (base deficit) indicate?
    metabolic acidosis
  5. What is a normal value for base excess?
    -2 - 2
  6. What determines the acidity of a solution?
    [H+]
  7. What is the normal pH and number of hydrogen ions in arterial blood and ECF?
    • 35-45 nmol/liter
    • 7.45 - 7.35
  8. What is the normal pH and number of hydrogen ions in the ICF?
    6.9, ~ 160 nmol/liter
  9. What is pH?
    • the power to which number 10 must be raised to find the exact number of H+ that exist in a liter of solution
    • - exponent of the number 10
    • - negative logarithm of H+
  10. If H+ are 1000, pH is ____
    6
  11. If H+ are 100, pH is ____
    7
  12. If H+ are 10, pH is ____
    8
  13. What are the 4 buffer systems?
    bicarbonate, hemoglobin, phosphate, protein
  14. What are the 3 ways the body regulates pH?
    buffer systems, ventilatory response system, renal response system
  15. What does it mean to be a weak acid?
    it readily gives up a H+
  16. What is pKa?
    A value that tells us the pH at which a solution is 50% ionized (deprotonated) and 50% non-ionized (protonated)
  17. If you have 2 solutions, one with a pKa of 8 and one with a pKa of 6, which one will more easily give up a hydrogen ion?
    pKa 8, it is a weaker acid
  18. What are the 5 components of the bicarbonate buffer system?
    • carbon dioxide
    • water
    • carbonic anhydrase
    • carbonic acid
    • bicarbonate
  19. What is the formula for the bicarbonate buffer system?
    CO2 + H2O <--> H2CO3 <--> H+ + HCO3-
  20. What does the Henderson-Hasselbach equation define?
    the hydrogen ion concentration in terms of pH (HCO3-/H2CO3 or pCO2)
  21. Where/how is most of the body's carbonic acid stored?
    in the blood as dissolved CO2
  22. What is quantitatively the largest buffering system in the ECF?
    bicarbonate buffer system
  23. What are the 3 variables of the H-H equation?
    measured HCO3, measured PaCO2, calculated pH
  24. How does a Hgb molecule accept a H+?
    by releasing O2
  25. What are the different percentages of blood CO2 transport?
    • 7% stays in plasma
    • 23% binds to Hgb
    • 70% converts to carbonic acid and then to H+ and HCO3- where HCO3- is pushed into the blood by a Cl- moving on to the cell
  26. What is the exchange of a Cl- for a HCO3- ion on a RBC called?
    hamburger shift or chloride shift
  27. What is the haldane effect?
    deoxygenated Hgb has a higher affinity for CO2
  28. Where are the 3 chemoreceptors located that are involved in the Ventilatory Response System?
    • 1) carotid bodies
    • 2) aortic arch
    • 3) ventral surface of the medulla oblongata
  29. What % of response is the central chemoreceptor responsible for?
    85%
  30. Where are the carotid body chemoreceptors located? What nerve do they use?
    • bilateral bifurcation of the carotid arteries
    • use glossopharyngeal (CN IX)
  31. What are the 3 mechanisms utilized by the renal response system?
    • 1) reabsorption of bicarb
    • 2) secretion of H+ (NH3-->NH4-> excretion)
    • 3) intracellular bicarb production
  32. Where is bicarb reabsorbed?
    the proximal tubules
  33. How does Acetazolamide (diamox) work?
    • carbonic anhydrase inhibitor
    • creates a non-AGAP acidosis
    • used to correct chloride-resistant metabolic alkalosis
  34. What are the causes (general) of Resp Acidosis?
    • 1) increased production
    • 2) Decreased elimination
    • 3) Increased rebreathing or absorption
  35. What causes an increased production of CO2?
    • malignant hyperthermia
    • hyperthyroidism
    • sepsis
    • overfeeding
  36. What causes decreased elimination of CO2?
    • pulmonary disease (PNA, ARDS, fibrosis, edema)
    • upper airway obstruction (laryngospasm, foreign body, OSA)
    • lower airway obstruction (asthma, COPD)
    • Chest wall restriction (obesity, scoliosis, burns)
    • CNS depression (anesthetics, opiods, CNS lesions)
    • decreased skeletal muscle strength
  37. What causes increased rebreathing or absorption?
    • exhausted soda lime
    • incompetent one way valve
    • laparoscopic surgery
  38. What causes Respiratory Alkalosis? (general)
    • Increased minute ventilation
    • decreased production
  39. What are causes of an increased minute ventilation?
    • hypoxia
    • mechanical ventilation 
    • anxiety, pain 
    • CNS disease (tumor, infection, trauma)
    • Fever, sepsis
    • drugs (salicylate, progesterone, doxapram)
    • liver disease
    • pregnancy
    • restrictive lung disease
    • pulmonary embolism
  40. What are causes of a decreased production of CO2?
    • hypothermia
    • skeletal muscle paralysis
  41. What are causes of AGAP metabolic acidosis?
    • M - methanol, ethylene glycol
    • U - uremia
    • L - lactic acidosis (decreased perfusion)
    • E - ethanol
    • P - paraldehyde
    • A - aspirin, INH
    • K - ketones
  42. What are causes of a non-AGAP acidosis?
    • NaCl administration > 30ml/kg/hr
    • GI losses (diarrhea, ostomy, pancreatic fistula)
    • Renal losses - RTA
    • acetazolamide
  43. What are the causes of metabolic alkalosis?
    • Chloride responsive:
    • - renal loss (diuretic therapy)
    • - GI loss (vomiting, NG suction)
    • - Alkali administration (citrate in blood products, acetate in TPN, bicarb)

    • Chloride resistant:
    • - hyperaldosteronism
    • - refeeding syndrome
    • - profound hypokalemia
  44. What are the dangers in over ventilating someone in reps acidosis?
    • You can create a metabolic alkalosis 
    • - CNS irritability and seizures
    • - hypocapnia causes vasoconstriction --> cerebral and myocardial ischemia
  45. What happens if respiratory alkalosis is prolonged?
    - HCO3- ions are transported our of the CSF --> resetting of central chemoreceptors to a lower PaCO2 level
  46. What role does phosphotructokinase play in alkalosis?
    • alkalosis --> 
    • stimulation of phosphotructokinase -->
    • glycolysis and generation of lactic acid
  47. Does alkalosis cause relative hypo or hypercalcemia? how? what symptom is associated?
    hypo - alkalosis increases the affinity between plasma proteins and calcium (so you can potentially see tetany)
  48. What is AGAP primarily used for?
    differential diagnosis of metabolic acidosis
  49. What is the formula to calculate AGAP?
    Na - (Cl + HCO3)
  50. If you have a metabolic acidosis but a normal AGAP, what does that mean? what is it called?
    • Cl- has replaced your HCO3- loss
    • hyperchloremic metabolic acidosis
  51. Where are common buffers found? what implication does this have?
    in the bone. chronic acidosis --> loss of bone mass
  52. How do you calculate how much bicarb someone needs? and how much do you administer?
    base deficit x weight in kg x 0.3

    administer half of this calculation and then recheck

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