Page 112 - Basic Monitoring in Canine and Feline Emergency Patients

In this analysis, positive numbers indicate effects duration. On physical examination, the patient has
that will be alkalinizing (free water effect, chloride no overt abnormalities. Abdominal imaging is
VetBooks.ir effect, albumin effect) and negative numbers indi- within normal limits; a stat venous blood gas is
run while full bloodwork is pending. The com-
cate values that will be acidifying (phosphate, lac-
tate). In contrast to traditional acid–base analysis,

non-traditional (semi-quantitative) analysis dem- bined results of both are below:
onstrates in this case that the metabolic side of the
acid−base analysis is a mixed process (i.e. due to Parameter (unit) Patient value Normal value a
multiple underlying causes), and helps the clinician pH 7.35 7.4
see what effect corrections of various values PvO (mmHg) 35 35
2
should have on acid–base status. PvCO (mmHg) 21.2 45
2
−
In this patient, a free water deficit (see Chapter HCO (mmol/L) 12 22
3
8) is causing a concentrating effect, which is ‘cor- BE (mmol/L) –13 0
recting’ the measured chloride to normal. This is Na (mmol/L) 153 153
hiding what is actually a significant hypochlo- K (mmol/L) 5.1 4.3
remia that becomes apparent when the chloride is Cl (mmol/L) 120 122
corrected. Combined with the hypoalbuminemia, Albumin (g/dL) 3.4 3.3
these effects explain the alkalinizing forces of the Phosphorus (mg/dL) 6.4 5.7
Lactate (mmol/L)
1.2
<2
metabolic assessment. Likely differentials in this Creatinine 3.5
patient include respiratory or renal losses of free BUN 31
water and hypoalbuminemia secondary to the Glucose 177
systemic inflammatory response seen in heat
stroke. These forces are masking the acidifying a Stated normal values used for calculations are the median of
effects of a significant hyperlactatemia and mod- the analyzers’ reference range. For example, if the range for
erate hyperphosphatemia, both presumably sec- sodium is 148–157, the median value used for normal is 153.
ondary to poor perfusion causing anaerobic
metabolism and decreased glomerular filtration.
When all effects (free water, chloride, phosphate, Traditional analysis
albumin, and lactate) are summed up and sub- 1. Assess the pH. The pH is slightly acidemic.
tracted from the base excess, the unmeasured 2. Assess the PCO and HCO to determine
−
2
3
anion effect is <5, therefore there are unlikely to which is causing the acidosis.
be any other significant unmeasured anions play- # # PvCO is low which would cause a respira-
2
ing a role (such as toxins). tory alkalosis, so the pH is not the ‘fault’ of
With both approaches, practitioners will recognize the respiratory side.
−
the respiratory abnormalities and be able to # # HCO is low which would cause a metabolic
3
address the dog’s hypoventilation. The non-tradi- acidosis. This explains the pH. Therefore,
tional approach allows for a more nuanced break- this cat has a metabolic acidosis.
down of the contributions of each aspect of the # # Is compensation adequate? For every 1-point
−
metabolic disorders and might prompt more timely change in HCO , pCO should change by
2
3
recognition of the free water deficit and chloride 0.7. 22 − 12 = 10 × 0.7 = 7. 45 − 7 = 38. The
effects than with traditional analysis. actual value of pCO is much lower (21.2)
2
This patient was hospitalized in critical condi- than this expected value, so there is exces-
tion and required multiple interventions including sive hyperventilation beyond what is needed
plasma support for coagulopathy. He did make a for compensation alone. This patient there-
full recovery and was discharged to his owners fore has a mixed metabolic acidosis and res-
after 9 days of hospitalization. piratory alkalosis.
# # For a metabolic acidosis, assess the anion
gap. AG = (153 + 5.1) − (120 + 12) = 26.1.
Case study 2: Use of the anion
gap in acid–base analysis This was considered elevated as compared
to the reference range given for this chemis-
A 2.5-year-old spayed female domestic shorthair try analyzer (10–23), and approaches the
cat presents for lethargy and vomiting of one day’s upper end of general AG references for cats
104 A.C. Brooks