Acid-Base Disorders

Question 1

Metabolic Acidosis

Answer 1

• Decreased pH
• Decreased HCO3- concentration (disturbance)
• Decreased pCO2 (Compensation)
• Inability to compensate causes secondary disorder
• Must Determine presence or absence of anion gap
• Compensation: pCO2=1.5(HCO3)+8 +/-2

Question 2

Anion Gap Metabolic Acidosis

Answer 2

• AG=[Na]-[Cl]-[HCO3]
• AG should be 12
• Elevated AG indicates excess acid (Endogenous or exogenous)
• If hypoalbuminemia present, normal AG is decreased (2.5per1)
• Causes: MUDPILES
• Methanol
• Uremia
• Diabetic ketoacidosis
• Paraldehyde/pyroglutamic acid
• Iron/Isoniazid
• Lactic acidosis
• Ethylene glycol
• Salicylates

Question 3

Non-Anion gap Metabolic acidosis

Answer 3

• Hyperchloriemic b/c Cl concentration increases to leave normal AG
• Associated w/ excess bicarb loss from the body
• Diarrhea
• Renal Tubular Acidosis
  
  • Proximal RTA: impaired bicarb reabsorption (urine pH5.3)
  • Hyperkalemic distal RTA: impaired H+ & K+ secretion (<5.3)

Question 4

Respiratory Acidosis

Answer 4

• pH decreased
• pCO2 increased (disturbance-from hypoventilation)
• HCO3- increased (Compensation)
• Due to CO2 retention from impaired respiratory function
• Causes: Drug OD, muscle weakness, obesity, chest abnormalities, aspiration, asthma, COPD, lung disease
• Compensation: HCO3- increases 1-3.5mmol/L per every 10 mmHg increase in pCO2

Question 5

Metabolic Alkalosis

Answer 5

• pH increases
• HCO3- increases (disturbance)
• pCO2 increases (compensation)
• Due to urinary or GI loss of H+ or total body gain of alkali
  
  • Vomiting
  • Diuretics
  • Mineralocorticoid excess
  • Rabid administration of bicarb
• Volume depletion w/ low urine chloride is chloride responsive
• Decreases respiratory drive
• Compensation: pCO2 increases 6mmHg per 10mmol/L increases in HCO3-

Question 6

Respiratory Alkalosis

Answer 6

• pH increases
• pCO2 decreases (disturbance due to hyperventilation)
• HCO3- decreases (compensation)
• Causes: Hypoxemia: CHF, pneumonia, PE, altitude
  
  • Pulmonary disease
  • Stim respiratory center: saliculate, sepsis, psychogenic, lesion
• Compensation: HCO3 decreases 2-5mmol/L per 10mmHg decrease in pCO2