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60 Section I: Diagnostics and Planning

this risk is also affected by the presence of patient comorbidities and • eccentrocytes (associated with onion toxicity and some drugs;
various individual factors. Consequently, recognition of a patient’s Figure 6.1);
individual risk factors is an important step towards optimization • schistocytes (fragmented erythrocytes seen in DIC, iron defi-
and can lead to modified protocols in order to reduce risk. ciency, hemangiosarcoma or valvular stenosis);
Numerous factors have been associated with postoperative infec- • spherocytes (associated with hemolytic anemia, DIC, and iron
tion of surgical wounds in humans and animals. Some patient‐ deficiency; Figure 6.2).
based risk factors for infection associated with spinal surgery that
have been identified in people include anemia, coronary artery dis- Inclusions
ease, coagulopathy, bone and tissue neoplasia, malnutrition, diabe- • Heinz bodies (acetaminophen, propylene glycol, propofol, zinc
tes mellitus, smoking, immunocompromised hosts, obesity, alcohol and copper toxicities, diabetes mellitus, renal disease, lymphoma,
abuse, advanced age (>60 years), surgical duration, and previous and hyperthyroidism);
surgical infection [5,6]. In dogs, contamination of the surgical field • Howell–Jolly bodies (accelerated erythropoiesis, and secondary
due to either a break in asepsis or traumatic wound is an obvious to splenectomy, increased circulating corticosteroids, septicemia/
risk factor for infection [7]. Other suspected or proven factors endotoxemia, and hypoxia);
which are not specific to neurosurgery include length of anesthesia • basophilic stippling (associated with lead poisoning);
and length of surgery, number of people in the operating room, • infectious (canine distemper virus, Babesia spp., Cytauxzoon felis,
postoperative wound drainage, increasing body weight, intraopera- Mycoplasma spp.).
tive hypothermia, increasing age (>8 years), severe blood loss, shock
or hypotension, presence of a distant infection, prior irradiation of
the surgical site, systemic disease (e.g., uremia), endocrinopathies,
excessive use of electrocautery, use of propofol in the anesthetic
protocol, use of high doses of corticosteroids, postoperative admis-
sion to an intensive care unit (increases with increased duration of
stay), antimicrobial prophylaxis, contaminated suction tips, and use
of braided multifilament suture material [7–10]. Although not
reported specifically, tissue trauma resulting in poor tissue perfu-
sion, poor tissue apposition resulting in dead space and seroma for-
mation, and poor hemostasis resulting in hematoma also appear to
increase the risk of postoperative inflammation, dehiscence and/or
infection. Seromas and hematomas provide a good medium for
small numbers of contaminating bacteria to thrive since therapeu-
tic antibiotic levels cannot be reached in previously formed tissue
exudate and blood clots.

Complete Blood Count
Although some neoplasias such as multiple myeloma and lym- Figure 6.1 Blood smear from a dog presenting with oxidative damage to
phoma (which can be associated with hyperglobulinemia and erythrocytes causing eccentrocyte formation (erythrocytes in which the
abnormal circulating lymphocytes respectively) can cause spinal hemoglobin is localized to part of the cell, leaving a portion with little hemo-
and hematological abnormalities, this is rarely the case for con- globin; arrows). Source: Courtesy of Dr. Darren Wood.
ditions restricted to the vertebral column [3,11]. Regardless, a
CBC is still useful for detecting systemic diseases that may have
neurological manifestations, such as spinal infectious patholo-
gies, and is recommended in all cases. At a minimum, packed
cell volume (hematocrit) and total serum protein are recom-
mended for all surgical candidates as they provide baseline data
for monitoring hemorrhage and fluid balance. A platelet count is
also important for detecting thrombocytopenia and possible
bleeding tendencies.

Abnormalities [12,13]
Erythrocytes
Morphology
Poikilocytes
Red blood cells with different and abnormal shapes. The most com-
mon types include:
• echinocytes (associated with dehydration, inherited erythrocyte
defect or snake bite);
• acanthocytes (seen with concurrent hepatic or renal disease,
hemangiosarcoma, iron deficiency, and disseminated intravascu- Figure 6.2 Blood smear from a dog with immune‐mediated hemolytic ane-
lar coagulation [DIC] syndrome); mia exhibiting autoagglutination. Source: Courtesy of Dr. Darren Wood.