Acid/Base, Blood Gas Interpretation

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Table of Contents:
   Normal values
    Interpreting an arterial blood gas sample
        Arterial versus venous sample
        Acid-base status
        Ventilation
        Oxygenation
        Anion gap
        Using venous blood gas results
    Case studies:
        Case 1:            Case 6:
        Case 2:            Case 7:
        Case 3:            Case 8:
        Case 4:            Case 9:
        Case 5:            Case 10:
   Advanced Acid-Base Information

 

 

 

Normal Arterial Blood Gas Values for Dogs in Fort Collins, CO (1500 M)
Unless indicated otherwise, barometric pressure = 640 mm Hg

                              Mean       Standard Deviation
pH

7.386

0.030

pCO2

31.57

3.60

pO2

79.68

6.44

HCO3

18.22

2.16

B.E.

-4.55

2.14

Saturation

92.74

1.43

 

Interpreting an arterial blood gas result:

1.  Determine whether the sample is arterial or venous
        Saturation > 88% = Arterial
                         < 88% = Mixed, Venous,                                            Pulmonary Disease, etc.

2.  Determine the acid/base status of the patient

3. Assess the ventilatory status (PaCO2)

 

4. Assess how the animal is oxygenating

A = (Barometric Pressure - 47)0.21 - pCO2/0.8

a = pO2

Alveolar - arterial gradient = A - a

A-a Gradients in the Dog
Normal

0 - 10

Probably normal

11- 20

ARDS?

21 - 30

ARDS

> 30

A - a Gradient =PaO2/FIO2

Normal Value: A - a Gradient > 200

Example: A dog is intubated, has an inflated endotracheal tube and breathing 100% oxygen. His PaO2 = 160 mm Hg. How well is the dog oxygenating?

A - a Gradient = 160 / 1.0 (100% = 1.0!!)

= 160 (the dog is NOT oxygenating well!)

 

5. Determine the Anion Gap (if electrolytes are available).

Anion Gap = (Na+ + K+) - (HCO3- + Cl-)

 

Using venous blood gases to assess the acid-base status in dogs: (Wingfield WE, Van Pelt DR, Hackett TB: Usefulness of venous blood gases in estimating acid-base status of the seriously ill dog. J Vet Emer Crit Care 4:23-27, 1994.)

    1. Arterial pH = 0.039 + (0.961 X venous pH)

    2. Arterial pCO2 = 7.735 + (0.572 X venous pCO2

    3. Arterial HCO3- = 0.538 + (0.845 X venous HCO3-

 

Case Studies: 

Case #1:
6 year old intact Male English Bulldog
Hx: Hypoplastic trachea, mitral/tricuspid insufficiency

Blood Gas:

T = 38.3 C
Hb = 13.8 gm/dl
pH = 7.063
PaCO2 = 106.7 mm Hg
PaO2 = 56.3 mm Hg
HCO3- = 28.4 Meq/l
BE = -4.2
Saturation = 89.8%

Sample acquired on oxygen mask with spontaneous ventilation

Electrolytes:   
    Na+ = 152 mEq/l
    K+ = 3.3 mEq/l
    Cl- = 109 mEq/l

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


Second Sample:
T = 38.4
        Hb = 10.3
        pH = 7.267
        PaCO2 = 55.3
        PaO2 = 109.6
        HCO3- = 24.0
        BE = -2.6
        Sat = 95.9

Sample acquired with oxygen supplementation (40%):

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Treatment:_____________________________________

 

 

Answers


Case #2:
7 year old SF Golden Retriever
Hx: pancreatic duct adenocarcinoma, peritonitis

Blood Gas:
        T = 38.1
        Hb = 12.0
        pH = 7.202
        PaCO2 = 19.8
        PaO2 = 86.6
        HCO3- = 7.4
        BE = -18.5
        Sat = 91.5

Sample obtained on room air with spontaneous ventilation

Electrolytes:
Na+ = 153
        K+ = 3.4
        Cl- =123

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment: ______________________________________

 

 

Answers


Case #3:
6 year old CM Boston Terrier
Hx: projectile vomiting

Blood gas: T = 38.7

Hb = 18.3

pH = 7.490

PaCO2 = 47.0

PaO2 = 58.0

HCO3- = 34.8

BE = 10.2

Sat = 88.9

Barometric pressure = 640 mm Hg

Sample obtained on room air with spontaneous ventilation

Electrolytes:
        Na+ = 143
        K+ = 2.8
        Cl- = 72

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

                Anion Gap?___________________________

Treatment:_____________________________________

 

 

Answers


Case #4:
6 year old F Bichon
Hx: Addison's disease, pneumonia; developed pneumothorax post-transtracheal wash and went into cardiopulmonary arrest

Blood Gas: T= 37.4

Hb = 13.2

pH = 6.920

PaCO2 = 66.5

PaO2 = 52.0

HCO3- = 12.6

BE = -21.3

Sat = 88.5

Sample obtained with spontaneous ventilation on supplemental oxygen (60%)

 Electrolytes: Na+ = 138

K+ = 3.6

Cl- = 97

  Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


Case #5:

10 year old SF Golden Retriever
Hx: previously treated for immune-mediated thrombocytopenia. Now presented for recurrent vomiting. Intestinal biopsies reveal inflammatory bowel disease.

Blood Gas: T= 38.9

Hb = 11.7

pH = 7.397

PaCO2 = 27.9

PaO2 = 81.4

HCO3- = 16.5

BE = -6.0

Sat = 93.3

Sample obtained on room air, spontaneous ventilation.

 

Electrolytes: Na+ = 150

K+ = 4.5

Cl- = 118

  Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

  Treatment:_____________________________________

 

Answers


Case #6:
9 year old M Golden Retriever
Hx: tachypnea, lethargy, inappetence

Blood Gas: T = 39.0

Hb = 15.0

pH = 7.457

PaCO2 = 19.5

PaO2 = 56.7

HCO3- = 13.3

BE = -9.3

Sat = 92

Barometric pressure = 635 mm Hg

Sample obtained on room air, spontaneous ventilation

  Electrolytes: Na+ = 154

K+ = 4.2

Cl- = 114

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

  Treatment:_____________________________________

 

Answers


 Second Sample: T = 38.9

Hb = 14.2

pH = 7.438

PaCO2 = 30.0

PaO2 = 71.6

HCO3- = 19.6

BE = -2.3

Sat = 91.9

Barometric pressure = 628 mm Hg

Sample obtained on room air, spontaneous ventilation

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

 

Answers


Case #7:

8 year old M Great Dane
Hx: Not doing well for 1 week. Febrile. Hemogram reveals inflammatory leukogram (48 700 neutrophils). Systolic heart murmur. Echocardiography reveals vegetative lesions on aortic valve. BUN = 112, creatinine = 6.8, phosphorous = 12.2, urine specific gravity = 1.015.

Blood Gas: T = 40.1

Hb = 5.4

pH = 7.263

PaCO2 = 19.7

PaO2 = 68.9

HCO3- = 8.3

BE = -16.1

Sat = 84.1

Sample obtained on room air, spontaneous ventilation

 

Electrolytes: Na+ = 141

K+ = 5.9

Cl- = 114

 

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


Case #8:

5 year old CM canine mix
Hx: ataxia, depression, vomiting. BUN = 85, creatinine = 7.2, phosphorous = 13.3, calcium = 5.5. Urine specific gravity = 1.011, calcium oxalate crystals present.

Blood gas: T = 39.2

Hb = 18

pH = 7.162

PaCO2 = 21.1

PaO2 = 93.1

HCO3- = 7.0

BE = -19.9

Sat = 91

Sample obtained on room air, spontaneous ventilation

  Electrolytes: Na+ = 157

K+ = 5.9

Cl- = 114

  Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


 

Case #9:
5 year old M canine mix
Hx: immune-mediated hemolytic anemia. Acute onset respiratory distress.

Blood Gas: T = 38.8

Hb = 5.3

pH = 7.452

PaCO2 = 28.6

PaO2 = 69.2

HCO3- = 19.4

BE = -3.4

Sat = 91.5

Sample obtained on room air, spontaneous ventilation

Electrolytes: Na+ = 149

K+ = 3.6

Cl- = 115

 

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


 

Case #10:
1
2 year old CM English Setter
Hx: Diabetes mellitus, tachypnea. Radiographs reveal interstitial pattern in caudal lung lobes.

Blood Gas: T = 39.3

Hb = 12.4

pH = 7.156

PaCO2 = 32.9

PaO2 = 55.8

HCO3- = 10.8

BE = -16.2

Sat 72

Barometric pressure = 641 mm Hg

Sample obtained on room air, spontaneous ventilation

Electrolytes: Na+ = 144

K+ = 4.2

Cl- = 106

 

Blood Gas Assessment:

Arterial or Venous?____________

Acid-Base?__________________________________________

Ventilation?___________________________

Oxygenation?________________________________________

Anion Gap?___________________________

Treatment:_____________________________________

 

Answers


 

Copyright, 1999.  Wayne E. Wingfield, MS, DVM, Colorado State University
This page was last updated:  03/08/99