Respiratory Module Acid-Base Disturbances. Regulation of Acid-Base balances Normal plasma pH –...

Respiratory Module

Acid-Base Disturbances

Regulation of Acid-Base balances

• Normal plasma pH– 7.35-7.45

• pH is the indicator of– H+ ion concentration

• pH range compatible with life– 6.8 – 7.8

Learning Tip

• BASE – ALKALINE– pH– Base = alkaline = pH

• Acid– Acidic– pH– Acid = acidic = pH

• 3 Bases• 3 Acids• 3B = 3A• pH =

– Homeostasis– 7.40

• 4 Bases– High

• 4 Acids– High

• 4B = 4A• pH =

– Homeostasis– 7.40

• 2 Bases– Low

• 2 Acids– Low

• 2B = 2A• pH =

– Homeostasis– 7.40

• 4 Bases (alkaline)– High

• 3 Acids (acidic)– Normal

• 4B > 3A• pH =

– Alkalosis– > 7.45

• 3 Bases (alkaline)– Normal

• 4 Acids (acidosis)– High

• 3B < 4A• pH =

– Acidosis– < 7.35

• 3 Bases– normal

• 2 Acids– Low

• 3B > 2A• pH =

– Alkalosis– > 7.45

• 2 Bases– low

• 3 Acids– normal

• 2B < 3A• pH =

– Acidosis– < 7.35

Learning Tip

•Normal Acid & Base = pH = Alkalosis

•Normal Acid & Base = pH =Acidosis

• Acid & Normal Base = pH =Acidosis• Acid & Normal Base = pH = Alkalosis

Chemical Buffers• The body’s major buffer system is

– The bicarbonate-carbonic acid buffer system• Bicarbonate

– HCO3-

– Base– Alkaline

• Carbonic acid– H2CO3

– Acid– Acidic

Chemical Buffers

• Carbonic Acid– CO2 + H20 = H2CO3– When CO2 is increased

• Carbonic acid is increased

– When CO2 is decreased• Carbonic acid is decreased

Kidneys

• The kidneys regulate – The bicarbonate level HCO3-

• The kidneys are able to reabsorb as well as excrete– Bicarbonate ions (HCO3-) from the renal tubules

Kidneys

• If the kidneys retain / reabsorb bicarbonate– HCO3 plasma (base)– pH

• If the kidneys excrete bicarbonate– HCO3 plasma (base)– pH

Kidneys

• If the plasma pH is acidic (pH: A > B) the kidneys will compensate by…– Retain / reabsorb bicarbonate (HCO3

-) to help restore balance

– HCO3- in the blood

– serum pH– 4A > 3B 4A = 4B

Kidneys

• If the plasma pH is alkaline (pH 3A > 4B or 2A >

3B) the kidneys will…– Excrete bicarbonate (HCO3-) to help restore

balance– HCO3– pH– 2A < 3B 2A = 2B

Kidneys

• Restoration of a balances pH is called:– COMPENSATION

• Renal compensation is:– Relatively slow– Takes hours - days

Lungs

• The lungs regulate – The Carbonic acid level / CO2

• The lungs are able to retain as well as excrete – CO2

Lungs

• Decrease in respiratory rate– CO2 (acid)– pH

• Increase in respiratory rate– CO2 (acid)– pH

Lungs

• If the plasma pH is acidic ( pH = 4A > 3B or 3A > 2B) the lungs will try to restore balance by…– Hyperventilating– CO2– pH– 4A > 3B 3A = 3B

Lungs

• If the plasma pH is alkaline ( pH = 3A < 4B or 2A < 3B) the lungs will try to restore balance by…– Hypoventilating– CO2– pH– 3A < 4B 4A = 4B

Learning Tip

Respiratory = Lungs = CO2 = Acid

Metabolic = Kidneys = HCO3 = Base

Practice Questions

1. HCO3- : 45

2. HCO3- : 24

3. PaCO2: 60

4. HCO3- : 18

5. PaCO2: 20

Practice Questions

1. HCO3-: 322. PaCO2: 40 3. HCO3-: 124. PaCO2: 535. PaCO2: 24

More practice questions

1. PaCO2: 652. PaCO2: 353. PaCO2: 524. PaCO2: 205. HCO3: 186. HCO3: 247. HCO3: 308. HCO3: 12

Respiratory Acidosis:Characteristics

• pH– < 7.35

• PaCO2– > 45 mmHg– Hypercapnia

• Metabolic Compensation– HCO3-– Kidneys reabsorb and retain HCO3

Respiratory Acidosis:Clinical Manifestations

• Feeling of fullness in the head• pulse and BP• Mental cloudiness• Weakness

Respiratory Acidosis:Etiology

Always d/t inadequate excretion of CO2• Hypoventilation• Pulmonary edema• Aspiration• Atelectasis• Overdose of sedatives

Respiratory Acidosis:Management

• Improve ventilation• Bronchodilators, antibiotics, pulmonary

hygiene measures

Metabolic Alkalosis:Characteristics

• pH– > 7.45

• Bicarbonate / HCO3-– > 26 mEq/l

• Respiratory compensation– CO2 by

• Hypoventilation

Metabolic Alkalosis:Clinical Manifestations

• Ca+• Tingling of the fingers • Hypertonic muscles• Atrial tachycardia• Tetany

Metabolic Alkalosis:Etiology

• #1– Vomiting or gastric suction

• Long term diuretics

Metabolic Alkalosis:Management

• Reverse underlying disorder• Restore normal fluid & electrolytes

Respiratory Alkalosis:Characteristics

• pH– > 7.45

• PaCO2– < 35 mmHg

• Metabolic Compensation– ↓ HCO3 by

• The kidney will excrete HCO3

Respiratory Alkalosis:Clinical Manifestations

• Lightheadedness• concentration• LOC

Respiratory Alkalosis:Etiology

• Hyperventilation– Extreme anxiety– Gram-negative bacteria– Excessive ventilation by mechanical ventilators

Respiratory Alkalosis:Management

• If anxiety breath more slowly• Breath into a closed system

Metabolic Acidosis: Characteristics

• pH – < 7.35

• Bicarbonate - HCO3– < 22

• Respiratory Compensation– CO2 by

• Hyperventilation

Metabolic Acidosis: Clinical Manifestations

• Confusion, H/A, drowsy• N&V• Cold clammy skin• Dysrhythmias• Hyperkalemia• Shock

Metabolic Acidosis: Etiology

• Renal failure• Diabetic ketoacidosis• Lactic acidosis• Salicylate poisoning• Diarrhea

Metabolic Acidosis:Management

• Correct metabolic defect• Watch K+ levels

Mixed acid-base disorders

• Is it possible to pat to have both respiratory and metabolic imbalances at the same time?– YES!

Compensation

• The pulmonary system and the renal will compensate for each other to return to pH to normal

• The lungs compensate for metabolic disturbances by altering the PaCO2 levels by Hyper/hypoventilation

• The kidneys compensate for respiratory disturbances by altering the HCO3- levels by reabsorbing retaining or excreting HCO3

Compensation

• Respiratory acidosis– Kidneys retain HCO3

• Respiratory alkalosis– Kidneys excrete HCO3

• Metabolic acidosis– Lungs excrete CO2 (hyperventilate)

• Metabolic alkalosis– Lungs retain CO2 (hypoventilate)

Medications & acid-base disturbances

• Diuretics – Metabolic Alkalosis

• Steroids– Metabolic alkalosis

• Narcotics– Respiratory acidosis

Blood Gas Analysis

pH 7.35 – 7.45

PaO2 80-100 mmHg

PaCO2 35-45 mmHg

HCO3- 22-26 mEq/l

Base Excess

-2 to +2

Si02 95 – 100%

• pH– Acidity / alkalinity

• PaO2– Not primary in acid-

base regulation– Change with O2

administration– < 60 acidosis– < 80 Hypoxemia

Blood Gas Analysis

pH 7.35 – 7.45

PaO2 80-100 mmHg

PaCO2 35-45 mmHg

HCO3- 22-26 mEq/l

Base Excess

-2 to +2

Si02 95 – 100%

• PaCO2– Effective ventilation– PaCO2

• Hypoventilation– PaCo2

• Hyperventilation

• HCO3-– Renal component– Kidney excrete or

retain

Blood Gas Analysis

pH 7.35 – 7.45

PaO2 80-100 mmHg

PaCO2 35-45 mmHg

HCO3- 22-26 mEq/l

Base Excess

-2 to +2

Si02 95 – 100%

• Base Excess– Amount of blood

buffer• High

– Alkalosis

• Low– Acidosis

• SiO2– % of Hgb saturated

with O2

Steps to Blood Gas Analysis

1. Label the pH, PaCO2 & HCO3-

• Serum pH > 7.4– Alkalosis

• Serum pH < 7.4– Acidosis

• Serum pH = 7.4– Homeostasis

Steps to Blood Gas Analysis

• Label the PaCO2 & HCO3-– PaCO2

• Acidosis– PaCO2

• Alkalosis– HCO3-

• Alkalosis– HCO3-

• Acidosis

Steps to Blood Gas Analysis

2. Find the Cause of the acid-base disturbance• pH > 7.4 Alkalosis

– If the PaCO2 is < 40 = respiratory alkalosis– If the HCO3- is > 24 = metabolic alkalosis

• pH < 7.4 Acidosis – If the PaCO2 > 40 = respiratory acidosis– If the HCO3- is < 24 = metabolic acidosis

Steps to Blood Gas Analysis

3. Check for compensation• The body tries to restore balance by altering

the buffer of the system that is not involved in the imbalance

• If compensation has occurred the values will move in the same direction as the other component.

Practice #1

pH 7.53

PaO2

PaCO2 42

HCO3- 34

Base Excess

SiO2

• Metabolic Alkalosis with NO respiratory compensation

Practice #2

pH 7.27

PaO2

PaCO2 38

HCO3- 14

Base Excess

SiO2

• Metabolic Acidosis with NO respiratory compenstation

Practice #3

pH 7.54

PaO2 50

PaCO2 30

HCO3- 25

Base Excess

SiO2

• Respiratory Alkalosis with NO metabolic compensation

Practice #4

pH 7.50

PaO2 85

PaCO2 40

HCO3- 30

Base Excess

SiO2

• Metabolic Alkalosis with NO respiratory compensation

Practice #5

pH 7.30

PaO2 40

PaCO2 56

HCO3- 26

Base Excess

SiO2

• Respiratory acidosis with NO metabolic compensation

Practice #6

pH 7.23

PaO2 90

PaCO2 40

HCO3- 16

Base Excess

SiO2

• Metabolic Acidosis with NO respiratory compensation

Practice #7

pH 7.30

PaO2 50

PaCO2 60

HCO3- 30

Base Excess

SiO2

• Respiratory Acidosis with partial metabolic compensation

Practice #8

pH 7.45

PaO2 50

PaCO2 50

HCO3- 34

Base Excess

SiO2

• Metabolic Alkalosis with complete/full respiratory compensation

Practice #9

pH 7.35

PaO2 85

PaCO2 64

HCO3- 34

Base Excess

SiO2

• Respiratory acidosis with complete/full metabolic compensation

Practice #10

pH 7.45

PaO2 80

PaCO2 35

HCO3- 24

Base Excess

SiO2

• Normal

Practice #11

pH 7.27

PaO2 95

PaCO2 55

HCO3- 24

Base Excess

SiO2

• Respiratory acidosis with NO metabolic compensation

Practice #12

pH 7.50

PaO2 85

PaCO2 40

HCO3- 30

Base Excess

SiO2

• Metabolic Alkalosis with NO respiratory compensation

Practice #13

pH 7.14

PaO2 80

PaCO2 80

HCO3- 19

Base Excess

SiO2

• Respiratory & Metabolic Acidosis with no respiratory or metabolic compensation

Practice #14

pH 7.56

PaO2

PaCO2 40

HCO3- 45

Base Excess

SiO2

• Metabolic Alkalosis with NO respiratory compensation

Practice #15

pH 7.35

PaO2

PaCO2 58

HCO3- 31

Base Excess

SiO2

• Respiratory acidosis with complete/full metabolic compensation

Practice #16

pH 7.31

PaO2

PaCO2 22

HCO3- 14

Base Excess

SiO2

• Metabolic Acidosis with partial respiratory compensation

Practice #17

pH 7.49

PaO2

PaCO2 51

HCO3- 29

Base Excess

SiO2

• Metabolic Alkalosis with partial respiratory compensation

Practice #18

pH 7.43

PaO2

PaCO2 31

HCO3- 18

Base Excess

SiO2

• Respiratory Alkalosis with complete/full metabolic compensation

Practice #19

pH 7.29

PaO2

PaCO2 50

HCO3- 15

Base Excess

SiO2

• Respiratory & Metabolic Acidosis with NO respiratory or metabolic compensation

Practice #20

pH 7.25

PaO2

PaCO2 59

HCO3- 15

Base Excess

SiO2

• Respiratory & metabolic acidosis with no respiratory or metabolic compensation

Practice #21

pH 7.40

PaO2

PaCO2 60

HCO3- 35

Base Excess +12

SiO2

• Metabolic Alkalosis with complete/full respiratory compensation

Practice #22

pH 7.40

PaO2

PaCO2 60

HCO3- 35

Base Excess -12

SiO2

• Respiratory acidosis with complete/full metabolic compensation