Page 846 - Small Animal Internal Medicine, 6th Edition

818 PART VI Endocrine Disorders

for treatment failure (see the section on complications of therapy considered if the client reports clinical signs sugges-
insulin therapy). If hypoglycemia is noted clinically or bio- tive of hyperglycemia or hypoglycemia, if the physical exam-
VetBooks.ir chemically at any time, the insulin dosage should be ination identifies problems consistent with poor control of
glycemia (e.g., thin appearance, poor haircoat), or if the dog
decreased and further adjustments in the insulin dose made
as needed to attain glycemic control.
Many factors affect the dog’s glycemic control from day is losing weight.
to day, including variations in insulin administration and SINGLE BLOOD GLUCOSE
absorption, dietary indiscretions and caloric intake, amount DETERMINATION
of exercise, and variables that affect insulin responsiveness Measuring a single blood glucose concentration is helpful
(e.g., stress, concurrent inflammation, infection). As a con- only if hypoglycemia is identified. Documenting hypo-
sequence, the insulin dosage required to maintain glycemic glycemia supports insulin overdosage and the need to
control typically changes with time. Initially, a fixed dose of decrease the insulin dose, especially if glycemic control is
insulin is administered at home and changes are made only poor. In contrast, documenting an increased blood glucose
after the client consults with the veterinarian. As the insulin concentration does not, by itself, confirm poor control of
dose range required to maintain glycemic control becomes glycemia. Stress or excitement can cause marked hypergly-
apparent, and as confidence is gained in the client’s ability to cemia, which does not reflect the dog’s responsiveness to
recognize signs of hypoglycemia and hyperglycemia, the insulin and can lead to the erroneous belief that the diabetic
client is eventually allowed to make slight adjustments in the dog is poorly controlled. If a discrepancy exists between the
insulin dose at home on the basis of clinical observations of history, physical examination findings, and blood glucose
the pet’s well-being and ideally results of home blood glucose concentration, or if the dog is fractious, aggressive, excited,
monitoring. or scared and the blood glucose concentration is known to
be unreliable, serum fructosamine concentration should be
Techniques for Monitoring Diabetic Control measured for further evaluation of the status of glycemic
The basic objective of insulin therapy is to eliminate the control. In addition, a single blood glucose concentration is
clinical signs of diabetes mellitus while avoiding or delay- not reliable for evaluating the effects of a given type and dose
ing the onset of common complications associated with of insulin in a poorly controlled diabetic dog (see the section
the disease (see Box 49.5). Blindness caused by cataract on serial blood glucose curve).
formation is inevitable for most diabetic dogs but can be
delayed if good glycemic control can be established and SERUM FRUCTOSAMINE
wide fluctuations in the blood glucose concentration avoided CONCENTRATION
(see page 828). Complications to avoid include poor hair- Fructosamines are glycated proteins that result from an
coat and unthrifty appearance, weight loss, hypoglycemia, irreversible, nonenzymatic, insulin-independent binding of
recurring ketosis, and recurrence of polyuria and polydip- glucose to serum proteins. The extent of glycosylation of
sia. The devastating chronic complications of human dia- serum proteins is directly related to the blood glucose con-
betes (e.g., diabetic nephropathy, atherosclerosis) require centration; the higher the average blood glucose concentra-
years to develop and become clinically relevant and are tion during the preceding 2 to 3 weeks, the higher the serum
uncommon in diabetic dogs, in part, because diabetes is fructosamine concentration and vice versa. Serum fructos-
diagnosed in older dogs. As such, the need to establish amine concentration is not affected by acute increases in the
nearly normal blood glucose concentrations is not nec- blood glucose concentration, as occurs with stress- or
essary in diabetic dogs. Most clients are happy and most excitement-induced hyperglycemia, but can be affected by
dogs are healthy and relatively asymptomatic if most blood concurrent hypoalbuminemia, hypoproteinemia, hypertri-
glucose concentrations are kept between 100 mg/dL and glyceridemia, hyperthyroidism (cats), hypothyroidism, azo-
250 mg/dL. temia, prolonged storage at room temperature, and interfering
substances such as hemolysis (Table 49.5). Serum fructos-
HISTORY AND PHYSICAL EXAMINATION amine concentrations can be measured during the routine
The most important initial parameters for assessing control evaluation of glycemic control in a diabetic dog; to clarify
of glycemia are the client’s subjective opinion of severity of the effect of stress or excitement on blood glucose concentra-
clinical signs and overall health of the pet, findings on phys- tions; to clarify discrepancies between the history, physical
ical examination, and stability of body weight. If the client is examination findings, and serial blood glucose concentra-
happy with the results of treatment, the physical examination tions; and to assess the effectiveness of changes in insulin
is supportive of good glycemic control, and the body weight therapy.
is stable, the diabetic dog is usually adequately controlled. Fructosamine is measured in serum, which should be
Measurement of serum fructosamine concentrations can frozen and shipped on cold packs overnight to the labora-
add further objective evidence for the status of glycemic tory. Although freezing does not cause a significant change
control (discussed in greater detail later). Poor control of in results, prolonged storage of serum at room tempera-
glycemia should be suspected and additional diagnostics ture or in the refrigerator can decrease serum fructosamine
(e.g., serial blood glucose curve) or a change in insulin results. Each laboratory should furnish its own reference