Acid-base Imbalances Flashcards
What is the normal blood pH?
7.34-7.45
What are the 3 mechanisms of maintaining normal blood pH?
~ maintaining H+ ions to keep cell membrane integrity ~
1) Buffer systems (to respond instantly)
- Prevents drastic changes
- Rapidly changes strong acids and bases into weaker ones
- Located in intra & extracellular fluid
- Carbonic acid + hemoglobin + proteins and phosphates
2) Respiration (mins)
- CO2 is produced by cellular respiration
- HCO3- binds to excess H+ in the body to form CO2 again which will be exhaled from body
- H+ is more acidic than H2CO3 by-product
- If body is in alkalosis, rate of breathing dec to retain CO2 and ^ H+ conc to ^ acidity
- Occurs within 1-3 mins
3) Kidney excretion (hrs)
- Acids can only be excreted by kidney
- Kidneys can adjust blood HC)3 by ^ or dec secretion/absorption and producing new bicarbonate
What are acidosis and alkalosis?
Both can be either due to respiratory or metabolic reasons
Acidosis:
- ^ H+ ions
- Causes nervous system depression
- Respiratory (hypoventilation)
- Metabolic (^ metabolic acids)
Alkalosis:
- Dec H+ ions
- Causes nervous system irritability
- Respiratory (hyperventilation)
- Metabolic (excessive loss of H+ or ^ HCO3-)
What are the pH, PCO2 and HCO3 lab results for respiratory and metabolic acidosis/alkalosis?
RAc: Dec pH, ^ pCO2, N HCO3-
MAc: Dec pH, N pCO2, Dec HCO3-
RAlk: ^ pH, Dec pCO2, N HCO3-
MAlk: ^ pH, N pCO2, ^ HCO3-
How does respiratory acidosis occur?
- Hypoventilation (Accumulation of CO2 forms carbonic acid which dissociates into H+ ions)
- pH 7.35, PaCO2 > 45 mmHg
- Due to brainstem trauma, CNS depressant drugs, impaired respiratory muscle function, lung disorders
- If renal buffer (mechanism 3) is ineffective, may need ventilator support
What is the treatment for respiratory acidosis?
- Hold any respiratory depressant drugs
- Improve ventilation
- Opiates (NALOXONE) PRN
~ Response within 10 mins - BZP (FLUMAZENIL) PRN (max x5 every 20 mins)
- ABG every 2-5 hrs initially, then12-24 hrs
- Basic metabolic panel needed
How does metabolic acidosis occur?
- Certain conditions cause generation of excess acids (eg lactic acids, salicylic acid)
~ Body ^ RR to try to excrete excess acids in the form of CO2
~ Kidneys may also have impaired ability to excrete H+
What is the treatment for metabolic acidosis?
- HCO3- replacement (ie sodium bicarb)
~ Only if chronic
~ Not used for acute (DKA, lactic acidosis, septic shock) - Treat underlying condition instead
How does respiratory alkalosis occur?
- Hyperventilation (due to respiratory stimulates, ^ metabolic demands etc)
- pH >7.45 PaCO2 < 35 mmHg
What is the treatment for respiratory alkalosis?
- Correct underlying disorders
- Hold any suspected drugs
- Initiate ocygen therapy in px with severe hypoxemia (pO2 < 40 mmHg)
- Treat theophylline overdoses
How does metabolic alkalosis occur?
- Excessive loss of H+ or excessive HCO3- loss
- Prolonged vomiting, gastric suction
- Excessive antacid usage
How is metabolic alkalosis treated?
- Correct underlying conditions
- Hold any suspected drugs
If ECF volume dec:
- NS for fluid resus
- Replace K+ and Cl-
If ECF overload:
- w no renal insufficiency: ACETAZOLAMIDE
- but w ARF/ESRD: HD or PD
- but w hyperaldosteronism: SPIRONOLACTONE or AMILORIDE
~ use K+-sparing diuretics instead of loop diuretics
What are the normal results of an ABG?
pH: 7.35 - 7.45
PaO2: 80 - 100 mmHg
PaCO2: 35 - 45 mmHg
HCO3: 22 - 26 mEq/L
Base excess (BE): -2 to +2
SaO2: 95% - 100%
Why is ABG sent down in ice?
To slow down metabolism of RBC
What is the difference between partially and fully compensated states?
pH completely returns to normal in fully compensated states (but will be on the low/high sides of neutral)
