33 terms

Acid Base Disorders

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Normal blood pH
7.35-7.45
Three ways blood pH is regulated?
Cellular buffer system
Respiration
Renal
Acidosis
pH lower than 7.35
Alkalosis
pH greater than 7.45
ABG
arterial blood gas (labs you can order)
How does your respiratory system compensate for acidosis?
Hyperventilation (blowing off CO2)
How does your respiratory system compensate for alkalosis?
Hypoventilation (retaining CO2)
How is your blood pH determined?
by ratio of HCO3 :CO2
What's wrong with someone who is hyperventilation?
too little CO2
What's wrong with someone who is hypoventilating?
too much CO2
Hypercapnia
So much CO2 --> coma/confusion --> lose drive to breathe
Metabolic alkalosis
Too much HCO3 (bicarbonate)

Gain of HCO3 or loss of H+
(↑ HCO3 )

Increases pH
Metabolic acidosis
Defined as pH < 7.35 without elevated PCO2

Too little HCO3

Loss of HCO3 or gain of H+
(↓ HCO3 )

Decreased pH
Respiratory alkalosis
Too little CO2
pH greater than 7.45
CO2 less than 35
Caused by hyperventilation (losing CO2)
Mixed metabolic and respiratory acidosis
Too much CO2 AND too little HCO3
What do we tolerate better - alkalosis or acidosis?
We can tolerate a lot more alkalosis than acidosis
Mixed metabolic and respiratory alkalosis
Too much HCO3 AND too little CO2
Normal PO2
80-100
Normal PCO2
35-45 mmHg
Normal HCO3
22-26 mEq/L (arterial)
Different reasons causing alkalosis
Hyperventilation
1. Stimulation of medullary respiratory center: Septicemia, hysterical hyperventilation, salicylate poisoning, neurologic disorders

2. Hypoxemia: high altitude, pneumonia, severe anemia

3. Mechanical ventilation

*The body can tolerate alkalosis well, prob wont be hospitalized
Signs and symptoms of respiratory alkalosis
- Usually sudden onset
- Hyperexcitability of NS
- Signs of hypokalemia (too low calcium --> the Ca ions start to bind with protein)
- Numbness of fingers and toes (remember, this is hyperventilation), tingling, dizziness, light-headedness
- Possible positive Chvostek and Trousseau signs
- Apnea in hypoxic drivers
Respiratory acidosis
pH less than 7.35
PCO2 greater than 45
Causes of respiratory acidosis
1. Inhibition of respiratory center in medulla (E.g., by opiates, sleep apnea, CNS lesions, O2 therapy in hypoxic drivers)

2. Respiratory mm disorder (E.g., Guillain-Barré syndrome, polio, ALS, MS)

3. Disorder of gas exchange (E.g., COPD, Pneumonia, pulmonary edema)

4. Airway obstruction (E.g., Obstructive sleep apnea, aspiration, laryngospasm)
Signs and symptoms of respiratory acidosis
HA, weakness, change in LOC/behavior
- Often d/t vasodilation of cerebral blood vessels 2/2 elevated CO2

Warm flushed skin

Hypoxemia sx
Causes of metabolic alkalosis
Loss of H+ : Vomiting, hyperaldosteronism

Ingestion of HCO3-
- Ingestion of NaHCO3 (baking soda)
- Milk-akalai syndrome

Increased reabsorption of HCO3-
- Loop or thiazide diuretics
Metabolic alkalosis signs and symptoms
- Often asymptomatic
- May have sx related to hypovolemia, hypokalemia
- Possible neuro sx (especially acute, severe alkalosis)
- Hyperreflexia, tetany
- Compensatory hyperventilation
Causes of metabolic acidosis
Excessive production or ingestion of fixed H+ (increased anion gap)
! Lactic acidosis; poisoning with methanol, etylene glycol, formaldehyde; diabetic ketoacidosis; fasting/starvation
2. Loss of bicarbonate (normal anion gap)
! Diarrhea, some types of kidney disease, intestinal suction
3. Inability to excrete fixed H+
! Chronic renal failure (increased anion gap), some types of kidney disease (normal anion gap)
! Most often d/t increased fixed acid in body
! Can investigate source of metabolic acidosis with anion gap
Anion gap
The difference in the measured cations (positively charged ions) and the measured anions (negatively charged ions) in serum, plasma, or urine


Plasma anion gap = [Na+] - ([HCO3 ] + [Cl ])

Normal range: 8-16 mEq/L
Remember, 8-16 mEq/L is the amount of unmeasured cations

Results either:
- Low/Normal
- Elevated
How to interpret ABG
1. Look at pH (<7.35 = acidosis, >7.45 = alkalosis)

2. Is acidosis or alkalosis respiratory or metabolic? (look at PCO2 and HCO3)

3. Is there compensation?
ROME
Respiratory opposite - means your pH is low and CO2 is high
- resp acid: pH low, CO2 high
- resp alk: pH high, CO2 low

Metabolic Equal - same direction
- metabolic acid: PH is low and bicarb is low
- metabolic alk: pH is high and Bicarb is also high
Normal pH
Normal CO2
Low bicarb
Normal PO2

What does this mean?
Compensated respiratory acidosis

A renal response to something respiratory (it compensated)
Low PH (acidosis)
High CO2 (acidosis)
Normal bicarb
Low PO2

What is it?
Respiratory acidosis without compensation