Week 8 Flashcards
What is acidosis and alkalosis?
What is acidemia and alkalemia?
Pathological process/condition that causes pH to change
Blood pH altered
Acidemia pH < 7.35
Alkalemia pH >7.45
Cause for respiraotry acidosis or alkalosis?
Cause for metabolic acidosis or alkalosis?
Pathological change in PaCO2:
Often due to the lung function, but can be also due to CO2 poisoning.
Pathological change in [HCO3-]
What types of acid/bases are buffered by:
Non-votile buffers (e.g. Hb)?
Bicarbonate system (volatile)?
CO2
Metabolic acid products / Gastrointestinal acid products
Clinical causes for respiratory acidosis?
Non-pulmonary?
Pulmonary?
Non-Pulmonary:
Disruption in neural linkage driving breathing
Central nervous system depression (drug overdose, anesthesia)
External environment preventing nromal breathing (heavy weight)
Pulmonary:
Upper airway obstruction
Severe asthma attack
COPD (bronchitis especially)
Severe pneumonia
Severe pulmonary edema
Clinical causes for respiratory alkalosis?
Non-pulmonary?
Pulmonary?
Arterial hypoxemia or hypoxia
Direct stimulation of pulmonary mechano- and chemo-receptors by lung disease
Psychological factors
Chemical or physical factors that directly stimulate the medullary respiratory center
Pulmonary: Bacterial pneumonia, Pulmonary embolus, Acute asthma (all first three)
Non-pulmonary: sepsis, liver disease, pregnancy, psychogenic hyperventilation
When oxygen begins to drive breathing?
When PaO2 is less than 60 mmHg
Causes for metabolic acidosis
Gastrointestinal acid production (GAP)
Diarrhea or laxative abuse (loss og HCO3- and H+ absorption)
Metabolic acid production (MAP)
Imbalance between organic acid production and consumption (incomplete metabolism of carbons that forms acid because of lack of oxygen during hypoxia)
e.g. lactic acidosis (exercise), ketoacidosis (type I diabetes)
Causes for metabolic alkalosis
What does it require?
What will happen eventually to HCO3-?
Vomiting or nasogastric drainage (loss of H+)
Generation and maintenance mechanism (volume depletion, hypokalemia, aldosterone excess)
Spill of HCO3- urine
Values for acute respiratory acidosis and alkalosis
Acute respiratory acidosis
pH down by 0.07
HCO3- up slightly (~1 mM)
Acute respiratory alkalosis
pH up by 0.08
HCO3- down slightly (~2 mM)
Values for metabolic acidosis and alkalosis
Acidosis
PaCO2 = 1.5 x [HCO3-] + 8 ± 2 (Winter’s Formula)
Alkalosis
PaCO2 = 0.7 [HCO3-] + 20 (+/- 5)
Which electrolytes are measured?
Sodium Na+ (140 mM)
Potassium K+(4 mM)
Chloride Cl- (100 mM)
“Bicarbonate HCO3- “ (24-30 mM)(really total CO2)
Anion gap equation
Anion gap = [Na+]-([Cl-] + [CO2])
[HCO3-] vs. total CO2
[HCO3-] is in arteries (calculated from pH and PaCO2)
rules of thumb for acid base disturbances
venous total CO2 equals CO2 dissolved + [HCO3-]
Anion gap calculation
Normal ion gap
12mM +-4
Types of ion gaps
Normal
Anion gap metabolic acidosis or normochloremic
Non-anion gap metabolic acidosis or hyperchloremic