Page 249 - Problem-Based Feline Medicine

15 – THE CAT WITH POLYURIA AND POLYDIPSIA 241

closely monitor water intake and urine glucose, and if ● Dilute regular insulin with saline or manufac-
either increase, the cat should be reassessed immedi- turer’s diluent to increase accuracy of dosing. Give
ately and reinstituted if blood glucose ≥ 10 mmol/L 0.2 U/kg intramuscular initially, then continue with
(180 mg/dL). hourly injections at 0.1 U/kg.
● Adjust the dose up or down to achieve a decrease
Treatment of “sick” diabetic cats in glucose of 3–6 mmol/L (54–110 mg/dl) per hour.
Fluids are as important as insulin in dehydrated ● Once blood glucose is 16 mmol/L (288 mg/dl),
diabetic cats. give 0.1–0.4 U/kg every 4–6 h to achieve a blood
● Balanced electrolyte solutions or 0.9% sodium glucose of 11–14 mmol/L (200–252 mg/dl) in the
chloride is the best initial fluid depending on the first 24 h.
initial potassium concentration, with 0.9% sodium
For intravenous dosing of insulin:
chloride preferred in hyperkalemic cats.
● Use an infusion pump and add 25 IU of regular
● Once initial fluid and electrolyte deficits are cor-
insulin to a 500 ml bag of 0.9% saline, to produce
rected, use 0.45% NaCl with 30–40 mEq (mmol)/L
an insulin concentration of 0.05 IU/ml.
of KCl added.
● Infuse the insulin/saline mix using a pump into the
Serum potassium rapidly falls with treatment and maintenance fluid line via a Y piece, at an initial
potassium supplementation should be immediately rate of 1 ml/kg/h (0.05 IU/kg/h). Be sure to flush
instituted in fluids and orally, if potassium concentra- both sets of tubing before beginning the infusion, as
tion is initially normal. Cats with hyperkalemia at pres- insulin adheres to plastic.
entation usually require potassium within 12–24 h. ● When blood glucose reaches 180 mg/dl (10
● Supplement potassium in intravenous fluids at mmol/L), decrease the insulin infusion to 0.5
20–80 mmol/L (or mEq/L); do not exceed 0.5 ml/kg/h. At the same time replace the maintenance
mmol//kg/h. fluids with 0.45% NaCl supplemented to contain
● Supplement potassium orally using potassium glu- 2.5% dextrose and 30 mmol/L KCl.
conate 2–3 mmol (or mEq), q 8–24 h.
With either intramuscular or intravenous therapy, aim
Serum phosphorus falls rapidly with treatment. for a glucose drop of 54–72 mg/dl/h (3–4 mmol/L/h)
Hypophosphatemia causes hemolysis, muscle weak- and do not exceed a decrease of 108 mg/dl/h (6
ness and neurological signs. To supplement phosphate mmol/L/h). In the first 24 h, aim for a glucose con-
and potassium in intravenous fluids, give potassium as centration of 11–14 mmol/L (200–252 mg/dl). Long-
50% potassium dihydrophosphate and 50% potassium term adaptations to chronic hyperglycemia have
chloride. occurred, and glucose should not be normalized for
24–48 hours.
Bicarbonate is rarely required, because acidosis
improves rapidly with fluids and insulin therapy. If If glucose falls below 8 mmo/L (144 mg/dl) in the
bicarbonate is < 10 mmol/L (10 mEq/L), it can be first 24 h, add 50% dextrose to intravenous fluids to
added to the intravenous fluids using the formula: Body make a 5% solution.
weight × 0.4 × [12 – patient’s bicarbonate].
Continue regular insulin until dehydration is cor-
Cats which have normal hydration or are only mildly rected, and then swap to subcutaneous glargine, PZI,
dehydrated and not in shock can be started immedi- lente, or ultralente insulin administered q 24 h.
ately on insulin given subcutaneously (0.25 U/kg if
glucose is < 20 mmol/L (360 mg/dl); 0.5 U/kg ideal
body weight if glucose is ≥ 20 mmol/L).
Subcutaneous insulin is poorly absorbed in signifi- Prognosis
cantly dehydrated cats. These cats need intramus-
Prognosis is relatively good. Reported median survival
cular or intravenous insulin.
time is 17 months, considering the average age at diag-
For intramuscular dosing of insulin: nosis is 10–13 years.