Page 1390 - Small Animal Internal Medicine, 6th Edition

1362 PART XIII Hematology

interpretation based on standard canine reference ranges TABLE 83.1
may lead to misdiagnoses. These differences have been con-
VetBooks.ir firmed in a recent study with a large number of healthy Venous Cooximetry and Blood Gas Reference Intervals*
animals, in which even narrower and therefore more breed-
REFERENCE INTERVAL
specific RIs were established for Greyhound biochemistry
parameters (Dunlop et al., 2011). PARAMETER GREYHOUNDS NON-GREYHOUNDS
CREATININE/SDMA PO 2 (mm Hg) 36.3-84.3 34.6-69.6
Creatinine concentrations are significantly higher in Grey- PCO 2 (mm Hg) 25.6-39.9 24.7-44.4
hounds than in non-Greyhounds (1.6 and 1.03 mg/dL, SO 2 (%) 78.6-99.8 54.4-99.8
respectively; Feeman et al., 2003). Greyhounds have consid- tHb (g/dL) 18.1-25.0 15.0-21.3
erable muscle mass and predictably have higher body stores O 2 Hb (%) 75.6-97.4 54.7-96.1
of phosphocreatine, which may result in higher serum cre- COHb (%) 0.9-3.9 0.4-4.5
atinine concentrations. Greyhounds have a higher glomeru-
lar filtration rate (GFR) than non-Greyhounds (Drost et al., MetHb (%) 0.0-2.2 0.1-2.8
2006). Therefore the most likely cause of high serum creati- HHb (%) 0.4-21.2 2.7-40.0
nine concentrations in Greyhounds is the large muscle mass. P 50 (mm Hg) 26.0-28.4 21.4-38.4
These differences in serum urea and creatinine concentra- O 2Ct (mL/dL) 19.7-32.0 13.3-24.6
tions were recently confirmed using a large number of O 2 Cap (mL/dL) 23.8-34.1 20.2-28.5
Greyhounds, and the study indicated even narrower RIs
(11.34-26.18 and 1.12-1.98 mg/dL, respectively; Dunlop COHb, Carboxyhemoglobin; HHb, deoxyhemoglobin; MetHb,
et al., 2011). Actively racing Greyhounds usually have blood methemoglobin; O 2 Cap, oxygen capacity; O 2 Ct, oxygen content;
urea nitrogen values above the RI for dogs, primarily because O 2 Hb, oxyhemoglobin; PCO 2 , partial pressure of carbon dioxide;
of a raw meat–based diet. PO 2 , partial pressure of oxygen; SO 2 , oxygen saturation; tHb, total
hemoglobin.
Simmetric dimethylarginine (SDMA) is an amino acid *n = 57. These were established by our group (Zaldívar-López
metabolite excreted exclusively by glomerular filtration (Braf et al., 2011b) using the STP CCX Analyzer (Nova Biomedical,
et al., 2014). Shortly after this test became available recently, Waltham, MA).
we noticed that results were frequently above the RI (0-14 µg/
dL) in a high proportion of Greyhounds. After several
studies, it is clear that the RIs for SDMA should be higher in content (O 2 Ct), and oxygen capacity (O 2 Cap), and signifi-
Greyhounds; a recent study proposes using 19.9 µg/dL as the cantly lower deoxyhemoglobin (HHb) and P 50 values when
upper limit of the RI for Greyhounds) (Liffman et al., in compared with non-Greyhounds (Zaldívar-López et al.,
press); this should prevent overdiagnosing renal disease in 2011b). These findings support the fact that this breed is able
this breed. to carry a higher concentration of total oxygen in the blood.
As noted, this breed also has a lower P 50 and therefore
LIVER ENZYMES high oxygen affinity. Current studies on hemoglobin-based
Dunlop et al. (2011) reported narrower RIs for liver enzyme oxygen carriers have revealed that in certain tissues, a high-
levels in Greyhounds, finding higher alanine aminotransfer- affinity oxygen carrier is beneficial, delivering oxygen to the
ase (ALT) activity compared with the generic canine RI. The tissues that need it most, which would be of benefit during
mechanism of this change is yet to be determined. strenuous exercise. Although counterintuitive to traditional
wisdom, these mechanisms could explain the benefits of
SERUM ELECTROLYTES AND having a high-affinity Hb.
ACID-BASE BALANCE
Serum concentrations of sodium, chloride, and bicarbonate PROTEIN
are higher in Greyhounds than in non-Greyhounds, and Recently published Greyhound-specific reference ranges for
serum calcium (and ionized calcium), magnesium, and total protein, albumin, and globulin are 5.2 to 6.7, 2.7 to 3.7,
potassium concentrations are lower (Zaldívar-López et al., and 2.2 to 3.3 g/dL, respectively (Dunlop et al., 2011). Thus
2011a). The same study also found that Greyhounds have Greyhounds have lower plasma, serum protein, and globulin
higher serum glucose concentrations when using a Nova concentrations.
analyzer (Nova Analytical Systems, Niagara Falls, NY) but The hypoglobulinemia in Greyhounds using serum
lower glucose concentrations than the non-Greyhounds protein electrophoresis has been investigated further (SPE;
when using a Roche Hitachi 911 analyzer (GMI, Ramsey, Fayos et al., 2005). The concentrations of total protein, total
MN). globulin, and α 1 -, α 2 -, β 1 -, and β 2 -globulins were signifi-
Venous and arterial blood gas results in Greyhounds are cantly lower and the albumin-to-globulin ratio (A/G) was
presented in Table 83.1. Greyhounds have significantly significantly higher in Greyhounds than in non-Greyhounds.
higher pH, partial pressure of oxygen (PO 2 ), oxygen satura- No significant difference was found in albumin or γ-globulin
tion (SO 2 ), oxyhemoglobin (O 2 Hb), total Hb (tHb), oxygen concentrations. Possible mechanisms include chronic plasma