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1374 Poikilocytes Potassium

Poikilocytes
VetBooks.ir Definition

oxidative damage (Heinz bodies, eccentrocytes,
General term for abnormally shaped mature acanthocytes, prekeratocytes, keratocytes), rapidly dry smears by waving or use heat
block.
erythrocytes in blood. This shape change can pyknocytes), hepatic diseases (acanthocytes), • Lipemia causes lysis and distortion of
be artifactual (e.g., crenation) or pathologic venomous snake bite (echinocytes, spherocytes), erythrocyte morphology.
(e.g., spherocytes, schistocytes). See p. 1327. bee sting (spherocytes), congenital defect in • Crenation often occurs from effects of smear
erythrocyte membrane proteins (elliptocytes, preparation on erythrocytes.
Physiology spherocytes). • Reticulocytes have excess cell membrane,
Normal shape of mature erythrocyte is which can produce an abnormal shape;
discocyte (biconcave disk). With damage to Next Diagnostic Steps to Consider clinically relevant shape changes should only
cell membrane (e.g., antibodies, toxins, lipid if Levels are High be evaluated in mature erythrocytes.
accumulation), damage to hemoglobin (e.g., Based on specific poikilocyte(s) identified,
oxidation), or interaction with sinusoidal investigate associated diseases or conditions Specimen Collection and Handling
macrophages of spleen or liver, the plasma associated with that poikilocyte. EDTA whole blood (lavender top tube) and
membrane and/or protein cytoskeleton of the freshly prepared blood smear for laboratory
erythrocyte is/are altered, and an abnormal Important Interspecies Differences to stain
erythrocyte shape results. Crenation (artifact) occurs more commonly
in feline erythrocytes. Spherocytosis is more Pearls
Reference Interval easily detected in the erythrocytes of dogs, See p. 1327 for a differential diagnosis diagram
• Only artifactually induced poikilocytes (e.g., because normal canine erythrocytes have a of various poikilocytes.
crenation) should be observed in the blood prominent central pallor that is lacking in
of healthy animals. spherocytes. AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
• The presence of even low numbers of the EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
other types of poikilocytes should prompt Lab Artifacts
consideration of their associated conditions • Poorly prepared blood smears will distort
or diseases. canine erythrocytes so that central pallor is
lost and cells may resemble spherocytes.
Causes of Abnormally High Levels • Erythrocytes on blood smears allowed to
Immune-mediated hemolytic anemias (sphero- slowly air-dry during preparation could have
cytes), erythrocyte fragmentation (schistocytes, refractile markings and distortion; best to

Potassium

Definition Causes of Abnormally High Levels inappropriate fluid therapy (dilutional hypo-
Major intracellular cation continually pumped Decreased renal excretion (oliguric/anuric renal kalemia), polyuria associated with diabetes
into cell by energy-dependent sodium/ failure, urinary tract obstruction or rupture), mellitus, ketoacidosis, hyperadrenocorticism,
potassium-ATPase pump at cell membrane; hypoadrenocorticism, artifact gastrointestinal hyperaldosteronism, alkalemia, and hypokale-
important in cardiac and neuromuscular disease (salmonellosis, trichuriasis), pleural mic periodic paralysis of Burmese cats
membrane potentials/excitability effusion with repeated drainage, tumor lysis
syndrome, diabetic ketoacidosis, metabolic aci- Next Diagnostic Steps to Consider
Synonym dosis (due to inorganic acids), rhabdomyolysis if Levels are Low
K + See p. 516.
Next Diagnostic Steps to Consider
Physiology if Levels are High Drug Effects
Influenced by acid-base status. Metabolic Repeat measurement using green top tube • Hyperkalemia: angiotensin-converting enzyme
acidosis (e.g., with chronic kidney disease) (heparin) if sample was collected in a red inhibitors, potassium-sparing diuretics (e.g.,
+
causes extracellular shift and hyperkalemia. top tube; CBC, serum biochemistry profile, spironolactone), K penicillin, oversupple-
+
+
Under normal conditions, excess plasma K and urinalysis; evaluate for drugs that can mentation of fluids with K , o,p′-DDD (iat-
is excreted in the urine. Hyperkalemia is cause hyperkalemia; abdominal ultrasound/ rogenic hypoadrenocorticism), trimethoprim
uncommon if renal function is normal (excep- radiographs (check integrity of urinary tract); • Hypokalemia: loop diuretics (furosemide),
tions: postrenal lesions, hypoadrenocorticism, ACTH stimulation test to rule out hypoad- thiazide diuretics, amphotericin B, penicillin,
+
iatrogenic). Potassium is released during renocorticism if clinically compatible; blood administration of K -free fluids (dilutional)
normal platelet coagulation, potentially causing gas determination to assess acid-base status.
pseudohyperkalemia. See p. 495. Lab Artifacts
+
+
Serum K is higher than plasma K , especially
Reference Interval Causes of Abnormally Low Levels if thrombocytosis is present; marked hemolysis
Typically 3.5-5.5 mEq/L (mmol/L) Increased loss (vomiting, diarrhea), chronic in dog breeds (Akitas, English springer spaniels)
+
kidney disease (cats), postobstructive diuresis, with high K red blood cell concentration;
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