Acid-Base Balance Exam Review

Bicarbonate HCO₃-

Weak base

Normal bicarbonate levels

22-26

Chemical buffers alone cannot stop blood pH changes

Respiratory system as 2nd line of defense

• Hyper/Hypoventilation

3rd line of defense against pH changes

Kidneys

Full compensation

Blood pH is fully normal (7.35-7.45)

Partial compensation

pH cannot fully normalize

ROME

pH and HCO₃

• Respiratory Opposite

• Metabolic Equal

Acidosis pathophysiology

pH below 7.35 due to excess H⁺

Metabolic Acidosis

• Overprod + Underelim of H⁺

• Underprod + Overelim of HCO₃

Metabolic Acidosis LABS

• pH < 7.35

• Bicarb < 21

• PaO₂ normal

• PaCO₂ normal/slight decreased

• Hyperkalemia

Respiratory Acidosis

Impaired respiratory function

• Issues with O₂ and CO₂

• Retention of CO₂

Respiratory Acidosis S/S

• Decreased PaO₂ with rising PaCO₂

• Resp depression

• Inadequate chest expansion

• Airway obstruction

• Reduced alveolar-capillary diffusion

Respiratory Acidosis LABS

• pH < 7.35

• PaO₂ low + PaCO₂ high

• Serum bicarbonate variable

• K⁺ high (if acute) / normal or low (if renal compensation)

Assessing Acidosis

• CNS + Neuromuscular + CV CHANGES

• Resp + Skin + Psychosocial changes

Responding to Acidosis

Call physician (we can’t do anything without orders)

Respiratory Acidosis Treatment

• Improve gas exchange

• Bronchodilators + Anti-inflammatories + Mucolytics

• O₂ therapy

• Pulmonary hygiene

• Vent support

• Preventing complications

Alkalosis Pathophysiology

Decreased H⁺ + blood pH > 7.45

Metabolic ALKAlosis

• Base excess

• Acid deficit

Acid deficit

• Prolonged vomiting

• Excess cortisol

• Hyperaldosteronism

• Thiazide diuretics

• Prolonged NG suction

Base excess acidosis HALLMARK

ABG with elevated pH and bicarbonate with NORMAL O₂ and CO₂

Metabolic ALKAlosis Symptoms

• Confusion + Dizziness + Irritability

• Dysrhythmias + Anxiety + Seizures

• N/V + Diarrhea

• Compensatory HYPOventilation

Respiratory ALKAlosis cause

Due to HYPERventilation

Respiratory ALKalosis HALLMARK

• ABG with higher pH + low CO₂

• O₂ + bicarbonate usually normal

Respiratory ALKAlosis

• Hyperventilation + Tachycardia + Normal/Hypotension

• Anxiety + Seizures + Irritability

• Hyperreflexes + Muscle cramps

• Hypokalemia

• Numbness + Tingling in extremities

Assessment of ALKAlosis

• HYPOcalcemia + kalemia

• CNS changes (Chvostek’s + Trousseau’s)

• Tetany

• CV + Resp changes

Responding to Alkalosis

• Prevent further electrolyte loss + Restore fluid balance

• Monitor changes + provide safety

• Modify/stop gastric suctioning, basic IV solutions, and drugs promoting H⁺ excretion

Why be careful with NG suctioning?

Quickly causes metabolic ALKAlosis