Acid-Base Disorders

Question 1

pH, paCO2, HCO3,paO2, and oxygen saturation values

Answer 1

7.35-7.45, 35-45, 22-26, 80-100, >95%

Question 2

Keys to Acid-Base balance

Answer 2

Dietary metabolism of glucose, proteins & fats
= 15,000 mmol of CO2 daily

Lungs = Regulation of CO2
Kidneys =  Regulation of  H+ and HCO3-

Question 3

Major Buffering Pairs

Answer 3

increase in CO2 + water=H2CO3=H+ + HCO3-

Question 4

Acid-Base Regulation with lungs and kidneys

Answer 4

Lungs : Hypoventilation or Hyperventilation of CO2

Kidneys: Increased or Decreased reabsorption of HCO3

Question 5

pH < 7.35

Answer 5

acidosis

Question 6

pH > 7.45

Answer 6

alkalosis

Question 7

Arterial blood pH determinants

Answer 7

pH = 6.1 + log (HCO3/0.03 X PCO2)

Question 8

HCO3 excess

Answer 8

Metabolic alkalosis - increased HCO3 and paCO2

Question 9

HCO3 inadequacy

Answer 9

Metabolic acidosis

Question 10

When does Respiratory compensation begin

Answer 10

begins within the first hour and

is complete by 12 to 24 hours

Question 11

PaCO2 excess

Answer 11

Respiratory acidosis

Question 12

PaCO2 inadequacy

Answer 12

Respiratory alkalosis - decreased HCO3 and paCO2

Question 13

Renal compensation begins

Answer 13

begins within 24 hours and is complete in 5 days

Question 14

Steps to Determining Acid-Base disorder

Answer 14

Evaluate the pH (acidotic or alkalotic?)
Determine Source of pH disturbance:
Exam PaCO2 and HCO3 on the ABG
- decreased pH = increased CO2 = respiratory acidosis
- decreased pH = decreased HCO3 = metabolic acidosis
- increased pH = decreased CO2 = respiratory alkalosis
- increased pH = increased HCO3 = metabolic alkalosis
Determine Compensatory Status of pH disturbance

Question 15

compensatory mechanism is not yet active with no changes to pH

Answer 15

Uncompensated

Question 16

Jan Doe is a 45 y/o female admitted for a
severe asthma attack. She has been experiencing
increasing shortness of breath since admission 3 hours ago.
Her ABG’s are as follows:
pH = 7.22 ; PaCO2= 55 mmHg; HCO3 = 25 meq/L
What type of disorder does the patient exhibit?

Answer 16

Uncompensated Respiratory acidosis

Question 17

compensatory mechanism is active but has not fully corrected arterial blood pH

Answer 17

Partial

Question 18

John Doe is admitted to the hospital. He is a kidney dialysis patient who has missed his last two appointments at the dialysis center.
His ABG’s are as follows:
pH = 7.32 ; PaCO2= 32 mmHg; HCO3 = 18 meq/L
What type of disorder does the patient exhibit?

Answer 18

Partially compensated Metabolic acidosis

Question 19

compensatory mechanism has normalized arterial blood pH

Answer 19

Complete

Question 20

Jane Doe is a 54 y/o female admitted for an ileus. She has been experiencing nausea and vomiting. An NG tube has been in place for the last 24 hours.
pH = 7.43 ; PaCO2= 48 mmHg; HCO3 = 36 meq/L
What type of disorder does the patient exhibit?

Answer 20

Compensated Metabolic alkalosis

Question 21

Bicarbonate Reabsorption occurs where

Answer 21

Proximal Tubule

Gastric

Question 22

Bicarbonate Secretion occurs

Answer 22

Pancreas

Question 23

Metabolic acidosis

Answer 23

pH < 7.35: pH < 7.2 = Severe acidosis
pH < 6.7 = Incompatible with life
Deficiency in Serum HCO3/ Increase in Serum H ions

Question 24

Causes of Metabolic Acidosis

Answer 24

Normal anion gap

Excessive Anion Gap

Question 25

Causes of Metabolic acidosis:Normal anion gap

Answer 25

9 to 11 (AGap > 17 clinically relevant)
Represents a ↓HCO3- with ↑Cl- (keeps electroneutrality)
Termed “Hyperchloremic metabolic acidosis”
1) Excessive Diarrhea
Pancreatic secretions (GI) are rich with HCO3
Excessive loss of HCO3 results in excessive reabsorption of H+

Question 26

Causes of Metabolic acidosis:Excessive Anion Gap

Answer 26

Anion Gap metabolic acidosis > 17
Presence of Organic acids (i.e. lactic acid) or toxins
These acids/toxins consume HCO3- becoming anions
See a ↓HCO3- with NO ↑Cl-

Question 27

Causes of Increased Anion Gap (“MUDPILES”)Source of “Unmeasured Anions”

Answer 27

Methanol
Uremia 
Diabetes ketoacidosis
Propylene glycol
Isoniazid
Lactic acidosis
Ethanol intoxication
Salicylate overdose

Question 28

GS has lab results as follows:
Na    140
K      5.8
Cl     103
BUN  20
Scr    1.0 (0.
Gluc  90
EtOH  25mg/dL
No Ketones
GS has a h/o alcohol abuse and type I DM
pH = 7.16 ;  PaCO2= 28 mmHg; HCO3 = 9 meq/L
What  is the source of this Acid-Base disorder?

Answer 28

Alcohol intoxication

Question 29

Metabolic alkalosis

Answer 29

pH > 7.45: pH > 7.6= Severe alkalosis
pH > 7.7 = Incompatible with life
Excessive Serum HCO3 with loss of H+ ion

Question 30

Causes of Metabolic alkalosis

Answer 30

• Increased HCO3 Retention:
  Due to Loss of H+ ion (gastric or urinary)
  i.e., Nasogastric suctioning/ vomiting
• Contraction alkalosis
  Excessive diuresis
  promote loss of fluids with minimal or no loss of HCO3
  RESULT: Increases Serum HCO3

Question 31

Respiratory alkalosis

Answer 31

pH > 7.45: pH > 7.6= Severe alkalosis
pH > 7.7 = Incompatible with life
Inadequate Serum pCO2
Increased respiratory elimination of CO2

Question 32

Causes of Respiratory alkalosis

Answer 32

Hyperventilation

Question 33

Causes of Hyperventilation

Answer 33

CNS Mediated: Pain, Anxiety ,Fever, Head trauma, CVA
Medications: Theophylline, Nicotine, Catecholamines
Others: Severe anemia, High altitude, Hyperthyroidism

Question 34

Respiratory acidosis

Answer 34

pH < 7.35: pH < 7.2 = Severe acidosis
pH < 6.7 = Incompatible with life
Failure of the lungs to eliminate CO2-
Excessive serum pCO2

Question 35

Respiratory acidosis: Causes

Answer 35

Ventilatory failure :
Obstructive lung disease or Neuromuscular disease
i.e., Asthma, COPD versus Myasthenia gravis

Perfusion failure:
i.e., Massive Pulmonary embolism

Question 36

Stepwise approach to Acid-Base

Answer 36

Determine acidosis or alkalosis
Determine primary disorder
Determine severity & if compensation present
* If pH < 7.2 or pH >7.6 = SEVERE
Determine the Cause (remove)
* If metabolic acidosis - ? Excess anion gap