Acid-Base - Kania Flashcards
what is a normal pH
7.35-7.45
which side of the buffer system has fast compensation?
the lungs!! CO2 + H20
Which side of the buffer system has slow compensation?
the kidneys
H+ and HCO3
What is the normal value for PaCO2
40 mmHg
What is the normal value for HCO3
24 MEq/L
where is bicarbonate reabsorbed?
the proximal tubule in the kidney
where does H+ excretion occur in the kidney?
in the distal tubule
what is the primary change in metabolic acidosis?
Decreased HCO2
what is the compensatory mechanism for metabolic acidosis?
decreased PaCO2
what is the primary change in metabolic alkalosis
increased HCO3
what is the compensatory mechanism in metabolic alkalosis
increased PaCO2
What is the primary change in respiratory acidosis?
Increased PaCO2
What is the compensatory mechanism for respiratory acidosis
Increased HCO3
What is the primary change in respiratory alkalosis
decreased PaCO2
what is the compensatory mechanism for respiratory alkalosis?
decreased HCO3
How to identify metabolic acidosis
low pH, low serum HCO3, and compensatory decrease in PaCO2
need to calculate the anion gap
Anion gap = Na+ - (Cl- + HCO3-)
what is a normal anion gap?
3-11
causes of non-anion gap acidosis (loss of HCO3 replaced by Cl-)
diarrhea, pancreatic fistulas, biliary drainage, reduced HCO3 resorptive threshold in proximal tubule, reduced renal H+ excretion, chronic renal failure, TPN
Anion Gap Acidosis
MULE PAK
what is the dosing for bicarb
(0.5L/kgxIBW) x (desired HCO3 - actual HCO3)
What does MULE PAK stand for?
methanol intoxication, uremia, lactic acidosis, ethylene glycol, paraldehyde ingestion, aspirin, ketoacidosis
when anion gap acidosis is confirmed, calculate a delta gap
patient’s anion gap - normal anion gap
what are the causes of anion gap metabolic acidosis
lactic acidosis, shock, ethanol, metformin, propylene glycol, seizures, leukemia, hepatic/renal failure, diabetes, malnutrition, rhabdomyolysis, ketoacidosis, salicylate toxicity (ASA), methanol/ethylene glycol
What do you do with a delta gap
Add to the patients measured HCO3- (result should be in the normal range for HCO3-)
If HCO3 - is elevated, there is also metabolic acidosis present
risks of bicarbonate administration
hypokalemia, hypocalcemia
desired HCO3
12 mEq/L
give 1/3 to 1/2 of the calculated dose and monitor
How is metabolic acidosis characterized
increased pH, increased HCO3-, compensatory hypoventilation resulting in increased PaCO2
causes of metabolic alkalosis
loss of acid from the GI tract, administration of bicarb, contraction alkalosis
what is saline responsive alkalosis
urinary chloride <10-20 mEq/L; correcting volume fixes alkalosis
what are the causes of saline responsive alkalosis
diuretics, vomiting/NG suction, lactated ringers and TPNs
causes of saline resistant alkalosis
increased mineralcorticoid activity, hypokalemia, bartter’s syndrome
how is saline resistant alkalosis identified
urinary chloride >20
symptoms of alkalosis
muscle cramps, weakness, parathesisas, aposrtural dizziness, hypoxia, confusion, coma, seizures, CV collapse, arrythmias
treatment of saline resistant alkalosis
correct underlying cause; usually not urgent
treatment of saline responsive alkalosis
use 1 liter NS with K supplement if needed (<4), may also use carbonic anhydrase inhibitors
persistent metabolic alkalosis treatment
hydrochloric acid, ammonium chloride, arginine monohydrate
characteristics of respiratory acidosis
low ph, hypercapnia >45, compensatory increase in HCO3-
causes of respiratory acidosis
airway obstruction, reduced drive to breathe, PE or cardiac arrest, ALS, mech vent
respiratory acidosis symptoms
SOB, dyspnea, drowsiness, HA, coma, seizures, tachycardia, arrythmias
Treatment of respiratory acidosis
correct underlying cause, mech vent, may need bicarb
characteristics of respiratory alkalosis
increased pH, decreased PaCO2 <40, compensatory decrease in HCO3- concentration
cause of respiratory alkalosis
increased drive to breathe, mech vent, aSA intoxication
treatment of respiratory alkalosis
correct the underlying cause: ventilation, sedation, paralysis