Page 854 - Small Animal Internal Medicine, 6th Edition

826 PART VI Endocrine Disorders

500 600 60
VetBooks.ir 400 500 50
Blood glucose (mg/dL) 300 Blood glucose concentration (mg/dL) 300 30 Serum insulin concentration (µU/mL)
40
400

200
200
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100 100 10

0 8 AM Noon 8 PM Mid 8 AM
8 AM Noon 4 PM 8 PM
* *
FIG 49.10
FIG 49.9
Blood glucose concentration curves obtained from three Mean blood glucose (blue line) and serum insulin (red line)
poorly controlled diabetic dogs treated with recombinant concentrations in eight dogs with diabetes mellitus treated
human lente insulin twice a day, illustrating the typical with beef/pork-source NPH insulin subcutaneously once
blood glucose curves suggestive of the Somogyi response. daily. The duration of NPH effect is too short, resulting in
In one dog (solid line) the glucose nadir is less than prolonged periods of hyperglycemia beginning shortly after
80 mg/dL and is followed by a rapid increase in blood the evening meal. ↑, Insulin injection; *, equally sized
glucose concentration. In another dog (dashed line) a rapid meals consumed.
decrease in blood glucose concentration occurs within 2
hours of insulin administration and is followed by a rapid
increase in blood glucose concentration; the rapid decrease of insulin for the dog. Alternatively, glycemic regulation of
in blood glucose stimulates glucose counterregulation, the diabetic dog could be started over with an insulin dose
despite maintaining the blood glucose nadir above 80 mg/ of 0.25 U/kg given twice daily.
dL. In one dog (dotted line) the blood glucose curve is not
suggestive of the Somogyi response, per se. However, the Short duration of insulin effect
insulin injection causes blood glucose to decrease by For most dogs the duration of effect of lente and NPH
approximately 300 mg/dL during the day, and the blood insulin is 10 to 14 hours, and twice-daily insulin administra-
glucose concentration at the time of the evening insulin tion is effective in controlling blood glucose concentrations.
injection is considerably lower than the 8 am blood glucose However, in some diabetic dogs the duration of effect of lente
concentration. If a similar decrease in blood glucose occurs and NPH insulin is less than 10 hours—a duration that is too
with the evening insulin injection, hypoglycemia and the short to prevent periods of hyperglycemia and persistence of
Somogyi response would occur at night and would explain
the high blood glucose concentration in the morning and clinical signs (Fig. 49.10). Serum fructosamine concentra-
the poor control of the diabetic state. tions are variable but usually greater than 500 µmol/L. A
diagnosis of short duration of insulin effect is made by dem-
onstrating an initial blood glucose concentration greater
not always identified. Serum fructosamine concentrations than 300 mg/dL combined with a glucose nadir above
are unpredictable but are usually increased (>500 µmol/L); 80 mg/dL that occurs less than 8 hours after insulin admin-
these results confirm poor glycemic control but do not iden- istration and recurrence of hyperglycemia (>300 mg/dL)
tify the underlying cause. within 12 hours of the insulin injection (see Fig. 49.8). Treat-
Establishing the diagnosis may require several days of ment involves a change to longer-acting insulin (Fig. 49.11).
hospitalization and serial blood glucose curves—an approach Although PZI, insulin glargine, and insulin detemir all have
that eventually leads to problems with stress-induced hyper- the potential to be effective in diabetic dogs, our preference
glycemia. An alternative, preferable approach consists of is to start with insulin detemir at an initial dosage of 0.1 U/
arbitrarily gradually reducing the insulin dose by 1 to 3 U kg administered twice a day. The most common problem
(depending on the size of the dog and the dose of insulin) with insulin detemir is a prolonged duration of effect (>14
and having the client evaluate the dog’s clinical response over hours), which can create issues with hypoglycemia and
the ensuing 2 to 5 days, specifically as it relates to changes in glucose counterregulation when insulin detemir is given
polyuria and polydipsia. If the severity of polyuria and poly- twice a day. Regardless, most diabetic dogs require insulin
dipsia worsens after an initial reduction in the insulin dose, detemir twice a day to attain diabetic control, and the insulin
another cause for the insulin ineffectiveness should be dosage can be quite small to compensate for prolonged dura-
pursued. However, if the client reports no change or improve- tion of effect in dogs with this problem.
ment in polyuria and polydipsia, continued gradual reduc- Prolonged duration of insulin effect
tion of the insulin dose should be pursued until polyuria and In some diabetic dogs the duration of effect of lente or
polydipsia worsen again, which identifies an inadequate dose NPH insulin is greater than 12 hours, and twice-daily insulin