Acid/Base Imbalances Flashcards
Where is an ABG typically obtained from?
Radial, femoral, or brachial artery
What is the normal range of pH?
7.35-7.45
What is the pH range compatible with life?
6.8-7.8
What are the major regulators of acid-base balance?
- Major ECF buffer system: bicarbonate-carbonic acid buffer system
- Lungs, under control of medulla, regulate CO2 —> carbonic acid in ECF
- Kidneys regulate bicarbonate in ECF
How fast does each regulatory mechanism respond to changes in acid-base imbalances?
- Buffers = immediately
- Lungs = minutes-hrs
- Kidneys = 2-3 days, but the kidneys can manage balance indefinitely in chronic imbalances
Why can acidosis cause hyperkalemia?
When ECF H+ are increased, H+ enters the cells in exchange for K+
Why can alkalosis cause hypokalemia?
With decreased H+ levels, H+ enters plasma in exchange for K+
How does respiratory system respond to increased H+?
Increase in RR & depth —> increased CO2 elimination & decreased CO2 in blood
Hyperventilation = acidosis
How does respiratory system respond to decreased H+?
Decrease in RR —> CO2 retention
Hypoventilation = alkalosis
What is the normal range of urine pH?
Avg = 6, can increase or decrease b/t 4-8
What is the base:acid content ratio?
20:1
Normal ABG values
PH 7.35-7.45 PaCO2 35-45 HCO3 22-26 PaO2 80-100 Oxygen sat >94% Base excess/deficit +/- 2 mEq/L
Metabolic acidosis
S/S
HA, confusion, drowsiness, increased RR/depth, decreased BP, decreased CO, dysrhythmias, shock
If decrease is slow pt may be asymptomatic until bicarbonate is <15
Metabolic acidosis
Causes
DKA
Lactic acid accumulation (shock)
Severe diarrhea
Kidney disease
Metabolic acidosis
Compensation
Lungs increase CO2 excretion w/Kussmaul’s respiration (deep & rapid)
Kidneys attempt to excrete additional acid
Metabolic acidosis
Nursing interventions
- Monitor K level (can cause hyperkalemia)
- Serum calcium levels may be low w/chronic metabolic acidosis —> must be corrected prior to TX, can result in tetany from increase in pH & decrease in ionized calcium
Anion gap
Measurement of the difference b/t negatively and positively charged electrolytes
Used to help identify the cause of metabolic acidosis
What is normal anion gap?
8-12
How is anion gap affected from metabolic acidosis?
Increased w/acid gain (lactic acid, DKA)
Remains WNL when acidosis caused by bicarbonate loss (diarrhea, diuretics)
How to calc anion gap
Anion gap = Na - (Cl + HCO3)
Metabolic alkalosis
S/S
R/T decreased Ca - respiratory depression, tachycardia
R/T hypokalemia
Metabolic alkalosis
Causes
Prolonged vomiting, NG suction
Gain of HCO3 (ingestion of baking soda)
Metabolic alkalosis
Compensation
- Renal excretion of HCO3
- Decreased RR to increase plasma CO2
Metabolic alkalosis
Management
- Correct underlying problem
- Supply Cl to allow excretion of bicarb
- Restore fluid vol w/NS solutions
Respiratory acidosis
Causes
Always due to respiratory problem w/inadequate excretion of CO2 (hypoventilation, respiratory failure)
Respiratory acidosis
S/S
Suddenly increased pulse, RR, BP
Mental changes
Feeling of fullness in head
In chronic, may be asymptomatic because of compensation
Respiratory acidosis
Compensation
Kidneys conserve HCO3 & secrete H+ in urine
Respiratory acidosis
Complication
Increased ICP - if PaCO2 increases rapidly, cerebral vasodilation will increase ICP —> cyanosis, tachypnea
Respiratory alkalosis
Cause
Always due to hyperventilation
Respiratory alkalosis
S/S
Lightheaded, inability to concentrate, numbness/tingling, sometimes loss of consciousness
Causes of hyperventilation
Extreme anxiety, hypoxemia, early phase of salicylate intoxication, gram-neg bacteremia, inappropriate ventilator settings
Respiratory alkalosis
Compensation
Rarely occurs when acute
Can buffer w/bicarbonate shift
Renal compensation if chronic
