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Regulators of acid/base
- Buffers: act within seconds.
- Respiratory system: regulates CO2 and O2. Acts within minutes-hours
- Renal system: acts in hours to days.
Respiratory Regulators of acid/base
- System will respond within minutes to hours.
Renal regulators of acid/base
- Secretes hydrogen (H+) ions and reabsorbs bicarbonate (HCO3) ions
- Reabsorption and secretion of electrolytes (e.g., Na, Cl)
- Responds within hours to days
ABG Normal Values
- pH 7.35 - 7.45 overall state
- PaCO2 35 - 45 mm Hg (respiratory component)
- HCO3 22 - 26 mEq /L (metabolic component)
- PaO2 80 - 100 mmHg partial pressureof oxygen in arterial blood
- SaO2 96 - 100% arterial O2 saturation
How to obtain arterial blood
- Heparinized syringe to prevent clots
- Blood from an artery
- On ice to prevent changes in value due to temp. Can give you accurate results up to 10 minutes.
- Need to deliver promptly to lab.
Pathophys of Respiratory acidosis
- ↑ carbonic acid/build up of CO2
- Hypoventilation—MAIN CAUSE!
- Carbonic acid stays in the blood instead of being blown off by lungs, dissociates to HCO3 + H+
- Due to COPD/severe pneumonia, barbiturate OD
- Results in ↓
- pHCompensation – kidneys will conserve HCO3-and secrete H+ into urine
Pathophys of alkalosis
- Blows off CO2 (↓pCO2) which ↓ carbonic acid and ↑ pH
- Hyperventilation—MAIN CAUSE!
- Due to anxiety, CNS disorders, mechanical OVER-ventilation, sepsis
- Compensation – none (uncommon)
- Accumulation of carbonic acid and loss of bicarb
- Due to DKA, lactic acidosis, renal dis. (no reabsorption of bicarb or secretion of H+ by the kidneys)
- Compensation - ↑ CO2 blown off by the lungs (Kussmaul’s breathing); functioning kidneys will excrete acid
- Loss of acid from vomiting, gastric suctioning
- Gain of bicarb from ingesting baking soda
- Compensation - ↓ respiratory rate (↑CO2) and renal excretion of bicarb
SnSs of Respiratory acidosis
- DEPRESSED ACTIVITY
- pH < 7.35
- PaCO2 > 45 mm Hg
- HCO3 Normal or >26 mEq /L If compensating
SnSs of respiratory alkalosis
- Rapid, deep respirations (Kussmals)
- pH > 7.45
- PaCO2 < 35 mm Hg
- HCO3 < 22 mEq /L