Acid base I Flashcards
what are the clinical decision making steps to assessing acid base disorders?
- history
- pH: acidemic or alkalemic?
- metabolic or respiratory?
- anion gap?
- appropriate compensation?
- if metabolic acidosis, is it a mixed disorder?
- diagnosis?
- treatment?
what is the pH range compatible with life?
6.80 - 7.80
can a respiratory acid base disorder be both alkalosis and acidosis?
no
what is the range of normal blood pH?
7.35 - 7.45
what is the conceptual cause of metabolic alkalosis?
increased serum HCO3-
what maintains metabolic alkalosis?
condition resulting in inability to secrete HCO3- by the kidneys
what value indicates a primary metabolic alkalosis?
over 40 mmol / L [HCO3-]
what is the compensatory mechanism for metabolic alkalosis?
respiratory acidosis - hypoventilation, increased pCO2
what are the etiologies of metabolic alkalosis?
- GI proton loss
- renal proton loss
- intracellular shift of hydrogen
- alkali administration
- contraction alkalosis
what should be considered the normal value for bicarb?
25 mmol / L
although contraction alkalosis can be caused by diuretics, it is maintained by ___________
hyperaldosteronism
what is the mechanism for contraction alkalosis?
- diuretics trigger secretion of H+ and K+ with loss of volume
- to counteract this hypovolemia, aldosterone is released which promotes Na+/H2O/HCO3- and secretion of K+/H+
what are two major reasons why metabolic alkalosis can be maintained?
- chloride depletion (also decreases bicarb secretion)
- hypokalemia
which two drugs can cause renal hydrogen loss leading to metabolic alkalosis?
- loop diuretics
- thiazide diuretics
what are the treatment options for metabolic alkalosis?
- correct underlying cause and maintainers
- correct electrolyte abnormalities (NaCl or KCl resuscitation)
what are maintainers of metabolic alkalosis?
- hypovolemia
- hypokalemia
- reduced GFR
- chloride depletion
- aldosterone excess
what drug interferes with bicarb reabsorption?
acetazolamide
what value of [HCO3-] indicates a primary metabolic ACIDOSIS?
under 15 mmol/L
what is the compensation for metabolic acidosis?
respiratory alkalosis - hyperventilation, decreased pCO2
usually an increase in the anion gap is caused by an increase in the unmeasured _____________ (cations / anions)?
unmeasured anions
what is the concept behind anion gap? what is its purpose?
- the total number of cations and anions must be equal to maintain neutrality
- however, the ions measured by the lab (Na, Cl, HCO3) are NOT equal
- purpose: differentiates different causes of metabolic acidosis (high vs normal / non-anion gap)
what are the scenarios that lead to a normal anion gap metabolic acidosis?
- loss of substantial amounts of measured anion HCO3-, leading to a hyperchloremic state
- sum total of measured anions remains the SAME, and in turn the anion gap remains the same, but hyperchloremic - defective renal acidification resulting in failure to excrete normal quantities of metabolically produced acid
- hyperchloremic state occurs because conjugate base is excreted as sodium salt and sodium chloride is retained
what are the causes of high anion gap metabolic acidosis?
Methanol Uremia (chronic renal failure) Diabetic ketoacidosis (most common reason) Propylene glycol Infection / Iron / Isoniazid Lactic acidosis Ethylene glycol Salicylates (aspirin)
diabetic ketoacidosis is a triad of:
- hyperglycemia
- high anion gap metabolic acidosis
- ketonemia
