Blood gases and acid/base regulation Flashcards
Acidemia
increase in plasma hydrogen concentration above normal
Acidosis
a process causing an increase plasma hydrogen concentration
Alkalemia
a decrease in plasma hydrogen concentration below normal
Alkalosis
a process which decreases plasma hydrogen concentration
Acceptable range for hydrogen concentration
35-45 nm/L, pH 7.35-7.45
Two types of acids:
- Volatile (food metabolism)
2. Non volatile (ex. insulin generates keto acids)
Acid-base balance is maintained by 3 primary functions
- Chemical buffering
- Respiratory control of CO2
- Renal regulation
Carbonic Acid-Bicarbonate System
Co2 + H2O H2Co3 H+ + HCO3
Henderson-Hasselbalch equation
pH=pK + log [HCO3-]/a x pCO2
Acidity = Bicarbonate / Carbon Dioxide
the respiratory parameter
pCO2
measured across capillary/alveolus barrier, from high pressure to low pressure
Reference range: 35-45
Regulation of pCO2
if pCO2 increases: ventilation of lungs will increase
if pCO2 decreases: ventilation of the lungs will decrease
H+ receptors in the ventral wall of medulla & CO2 receptor in aortic and carotid bodies play an important regulatory role
pCO2 reflects
how well the lungs are functioning
the metabolic factor
HCO3- concentration controlled by the kidneys regulation takes place w/in hours/days Blood --> kidney cell --> urine Reference range: 22-28
Metabolic vs respiratory acidosis
Metabolic: HCO3 goes down, respiratory: pCO2 goes up
Metabolic vs respiratory alkalosis
Metabolic: HCO3 goes up, respiratory: pCO2 goes down
Metabolic acidosis
Renal failure, diabeties, anaerobic production of lactic acid, high protein intake, diarrhea
Compensation: decrease pCO2
Metabolic alkalosis
Vomiting, intravenous infusion of bicarbonate, intake of alkaline substances, K+ deficiency (increased renal excretion of H+)
Compensatoin: increase pCO2
PLUMSEEDS - Metabolic Acidosis causes
Paracetamol Lactic acidosis Uremia Methanol poisoning Salicylate Ethanol intake Ethylene glycol intake Diabetes mellitus Starvation
Respiratory acidosis
Hypoventilation
Airway obstruction
Sedative overdose
Compensation: Increase HCO3
Respiratory alkalosis
Hyperventilation
Anxiety, fever
Congestive heart failure
Compensation: Decrease HCO3
Compensation is driven by
pH
Compensation involves either a:
respiratory or metabolic response
a slightly abnormal pH suggests:
compensation
Rules for interpretation of acid base diseases
- Determine pH status
- Determine the primary process (observe HCO3)
- Look for compensation
