• Hyperventilating? (Decreased PaCO2)
• Hypoventilating?  (Increased PaCO2)
• Normal ventilation?

• Is the animal breathing room air?
  • Calculate the Alveolar-arterial (A-a) gradient

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

a = pO₂

Alveolar - arterial gradient = A - a

• Is the animal on supplemental oxygen?

A - a Gradient =PaO₂/FIO₂

Normal Value: A - a Gradient > 200

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 #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
P_aCO₂ = 106.7 mm Hg
P_aO₂ = 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:_____________________________________

Second Sample:
T = 38.4
        Hb = 10.3
        pH = 7.267
        P_aCO₂ = 55.3
        P_aO₂ = 109.6
        HCO₃^- = 24.0
        BE = -2.6
        Sat = 95.9

Sample acquired with oxygen supplementation (40%):

Blood Gas Assessment:

Treatment:_____________________________________

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

Blood Gas:
        T = 38.1
        Hb = 12.0
        pH = 7.202
        P_aCO₂ = 19.8
        P_aO₂ = 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:

Treatment: ______________________________________

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

Blood gas: T = 38.7

Hb = 18.3

pH = 7.490

P_aCO₂ = 47.0

P_aO₂ = 58.0

HCO₃^- = 34.8

BE = 10.2

Sat = 88.9

Barometric pressure = 640 mm Hg

Sample obtained on room air with spontaneous ventilation

Blood Gas Assessment:

                Anion Gap?___________________________

Treatment:_____________________________________

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

P_aCO₂ = 66.5

P_aO₂ = 52.0

HCO₃^- = 12.6

BE = -21.3

Sat = 88.5

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

K⁺ = 3.6

Cl^- = 97

  Blood Gas Assessment:

Anion Gap?___________________________

Treatment:_____________________________________

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

P_aCO₂ = 27.9

P_aO₂ = 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:

Anion Gap?___________________________

  Treatment:_____________________________________

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

Blood Gas: T = 39.0

Hb = 15.0

pH = 7.457

P_aCO₂ = 19.5

P_aO₂ = 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:

Anion Gap?___________________________

  Treatment:_____________________________________

 Second Sample: T = 38.9

Hb = 14.2

pH = 7.438

P_aCO₂ = 30.0

P_aO₂ = 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:

Anion Gap?___________________________

Treatment:_____________________________________

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

P_aCO₂ = 19.7

P_aO₂ = 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:

Anion Gap?___________________________

Treatment:_____________________________________

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

P_aCO₂ = 21.1

P_aO₂ = 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:

Treatment:_____________________________________

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

P_aCO₂ = 28.6

P_aO₂ = 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:

Anion Gap?___________________________

Treatment:_____________________________________

Case #10:
12 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

P_aCO₂ = 32.9

P_aO₂ = 55.8

HCO₃^- = 10.8

BE = -16.2

Sat 72

Barometric pressure = 641 mm Hg

Sample obtained on room air, spontaneous ventilation

K⁺ = 4.2

Cl^- = 106

Blood Gas Assessment:

Anion Gap?___________________________

Treatment:_____________________________________