Acid-Base Balance Flashcards
What chemicals constitute the primary pH buffer system in the blood?
Bicarbonate and CO2
Normal pH of the blood
7.4 (7.35-7.45)
Organs that are largely responsible for pH control
Lungs (through PCO2)
Kidneys (through HCO3-)
donate protons
Acid
accept protons
Base
Acid/base that dissociates completely
Strong acid/base
Acid/base that dissociates partially (results in conjugate bases/acids)
Weak acid/base
a solution that resists pH changes when an acid or base is added
Buffer
Metabolic acids (acids other than carbonic acid) are eliminated via the ______
Kidneys
What are the two types of acid that are eliminated by the lung and kidney, respectively?
Lung eliminates respiratory acid = CO2
Kidney eliminates metabolic acid = end products of protein, AA, and nucleic acid metabolism
Normal concentration of bicarbonate in blood
24 (24-28 mEq/L)
Why is it beneficial to have our buffer system in an “open” environment
If our blood becomes acidic and shifts to producing CO2 from bicarbonate, the CO2 can be blown off in the lungs, allowing for minimal impact from the acid on our pH
Why is bicarbonate a good biological buffer?
- Abundant (24-28 mEq/L)
- Good in an open system (lungs)
- PCO2 and HCO3- can be regulated independently
Examples of other buffers in body besides bicarbonate
- Plasma proteins and intracellular proteins w/ acidic and basic residues
- Hb (rich in Histamine)
- Non-protein buffers
- movement of acids and bases between plasma and cells
Normal cell (cytosolic) pH
6.8
How do the kidneys respond to excess acid?
Elimination of acid in urine
Retention of bicarbonate
Buildup of CO2 due to insufficient excretion of CO2 by the lungs; pH falls and PaCO2 rises; Caused by hypoventilation; can be caused by alcohol, drugs, or neuromuscular insult
Respiratory acidosis
Excess excretion of CO2 due to hyperventilation; pH rises and PaCO2 falls; can be caused by anxiety, drugs, acute asthma and neural dysregulation
Respiratory alkalosis
Buildup of acids (such as lactic or keto acids) to plasma that consume bicarbonate; CO2 stays normal as lungs compensate; can be caused by hypoxia, exercise, diabetes, diarrhea or renal syndromes
Metabolic acidosis
Loss of acids (such as lactic or keto acids), resulting in increased plasma bicarbonate; CO2 stays normal as lungs compensate; can be caused by emesis (loss of HCl), diuretics or excess ingestion of bicarbonate
Metabolic alkalosis
Compensation for respiratory acidosis
Renal compensation by increasing secretion of H+ in urine and retaining bicarbonate in plasma
Compensation for respiratory alkalosis
Renal compensation by decreasing secretion of H+ in urine and decreasing retention of bicarbonate in plasma
Compensation for metabolic acidosis
Inc. ventilation to decrease CO2 to normalize pH (can progress to Kussmaul breathing)
What is the breathing that is first rapid and shallow but progresses to deep labored breathing in severe diabetic keto acidosis?
Kussmaul breathing
Compensation for metabolic alkalosis
Dec. ventilation to inc. CO2 (rarely happens since it can cause hypoxemia)
metabolic pH disturbances have compensation at the level of what organ system?
respiratory (lungs and rate of ventilation)
respiratory pH disturbances have compensation at the level of what organ system?
renal (kidneys and selective retention/excretion)
- much slower than respiratory!!
Equation for the Anion Gap
Anion gap= Na - (Cl + HCO3-)
Normal range of carbon dioxide in blood
40 for convention (35-45)
Compensation Equation for metabolic acidosis (low HCO3)
PaCO2= (1.5 x HCO3) + (8+-2)
Indication for mechanical ventilation (invasive positive pressure)
Hyoxemic respiratory failure
Hypercarbic respiratory failure
Unstable airway (coma or seizure)
Goals of mechanical/invasive ventilation
Adequate tidal volume, respiratory rate and oxygen concentration
Prevent alveolar collapse (PEEP)
PEEP
Positive End Expiratory Pressure
Goals for mechanical ventilation in a case of hypoxemia
Adjust oxygen concentration and PEEP
Goals for mechanical ventilation in a case of hypercarbia
Inc. minute ventilation (tidal volume and respiratory rate)
BiPAP (inc. inspiratory pressure to inc. TV)
Respiratory acid is aka
volatile
Metabolic acid is aka
non-volatile or fixed
What diagram is used to interpret acid-base disturbances?
Davenport diagram
- Be able to read and interpret the diagram!!
Davenport diagram shows relationship between plasma
pH, HCO3-, and PCO2
True or False: Respiratory compensation takes longer than renal (metabolic) compensation
False