Page 111 - Basic Monitoring in Canine and Feline Emergency Patients

of ventilation should all be considered possible
Parameter (unit) Patient value Normal value a causes of the hypoventilation.
VetBooks.ir Albumin (g/dL) 2.1 3.1 3. Assessment of the metabolic side shows bicarbo-
nate and base excess are also elevated which would
7
3.9
Phosphorus (mg/dL)
be expected to cause a metabolic alkalosis. These
<2
Lactate (mmol/L)
7
processes are ‘cancelling out’ the respiratory acido-
a Stated normal values used for calculations are the median of sis, creating a normal pH. This would therefore be
the analyzers’ reference range. For example, if the range for classified as a mixed disturbance. Further assess-
sodium is 135–145, the median value used for normal is 140.
ment of the list of differentials for metabolic alka-
losis (see Table 5.3), indicates a free water deficit, as
While a 0.5 mL/kg bolus of 50% dextrose diluted indicated by the elevated sodium level, is the most
1:1 with saline and an initial 30 mL/kg crystalloid likely cause of the metabolic alkalosis.
bolus are started, the initial data is assessed:
Therapeutic interventions based on this analysis
Traditional approach would include interventions to improve ventilation
to resolve the respiratory acidosis (sedation and cool-
1. Evaluate the pH. Here, the pH is normal (7.4). ing, with possible intubation if necessary to improve
This demonstrates one of the pitfalls of traditional upper airway obstruction), and treatment to improve
acid–base analysis; by strictly following the ‘rules’ of perfusion (IV fluids). It is likely that the complexity
acid–base analysis, a clinician might stop here and of the metabolic aspect of acid–base would be missed
decide no acid–base abnormality is present. However, on initial evaluation. Repeat blood gas analysis as
the savvy clinician chooses to assess each compo- each parameter was normalized would reveal the
nent that can contribute to acid–base abnormalities. changing pH and might allow for further characteri-
Additional interpretation would be as follows: zation of this dog’s metabolic abnormalities.
2. Assessment of the respiratory side of the acid–
base equation reveals an elevated PvCO consist-
2
ent with hypoventilation. This would be expected Non-traditional approach
to cause an acidosis; the normal pH implies The assessment of the respiratory side of the acid–base
another alkalinizing process must also be hap- equation is identical as above: an elevated PvCO is
2
pening. The hypoventilation should be addressed consistent with hypoventilation and should be addressed
based on the likely differentials listed in Table based on the likely differentials listed in Table 5.1.
5.1. Given this patient’s mentation and stridorous In order to assess the metabolic side of the acid–
breathing, upper airway obstruction ± central res- base equation, the given values are utilized in the
piratory depression and/or exhaustion of muscles equations listed in Table 5.5:

Patient value and median
Effect Formula reference range value Calculated effect
Free water effect Dogs: 0.25[(Na ) − (Na )] Na = 160 3.5
p
r
p
Cats: 0.22[(Na ) − (Na )] Na = 146
p r r
Corrected chloride Cl × (Na /Na ) Cl = 110 Cl = 100.4 (see
p r p p corrected
chloride effect in next row)
Chloride effect Cl − Cl Cl = 110 9.6
r corrected r
Cl = 100.4
corrected
Phosphate effect 0.58 (Phos − Phos ) Phos = 7 −1.8
p
r
p
Phos = 3.9
r
Albumin effect 3.7 (Alb − Alb ) Alb = 2.1 3.7
r p p
Alb = 3.1
r
Lactate effect −1 × lactate Lactate p = 7 −7
p
Sum of effects Free water effect + Cl effect + Phos 3.5 + 9.6 + (−1.8) + 3.7 +
effect+alb effect + lactate effect (−7) = 8
Unmeasured anion effect Base excess − sum of effects BE = 10 10 − 8 = 2
Venous and Arterial Blood Gas Analysis 103