Page 515 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Fluid Therapy in Endocrine and Metabolic Disorders 503

above this limit to avoid worsening of hypokalemia. In disadvantage of the low-dose intramuscular protocol is
addition, hypotensive animals should receive fluid ther- that it requires considerable technical effort to accom-
apy sufficient to stabilize the circulatory status before plish hourly injections and blood glucose measurements.
insulin administration to prevent the decrease in plasma In addition, the decrease in blood glucose concentration
volume that occurs when glucose and water are seems to occur more rapidly and less predictably
translocated into cells in response to insulin. than with the continuous intravenous infusion method.
Administration of small doses of regular insulin has a The continuous low-dose intravenous infusion proto-
clear advantage over large doses because the smaller doses col involves administration of regular insulin diluted in
are less likely to cause severe hypokalemia or hypoglyce- normal saline using an intravenous infusion pump. 53
mia. 42 In addition, if the reduction in the blood glucose It is my preferred technique of insulin administration to
concentration is too rapid, the associated decrease in dogs with DKA because of the predictable and consistent
osmolality has the potential to contribute to development response, the gradual decrease in blood glucose concen-
of cerebral edema. Two methods of delivering low-dose tration (mean of 28 mg/dL/hr in dogs), and the ease of
insulin therapy to dogs have been described: the use. 53 Unlike the low-dose intramuscular protocol, treat-
low-dose intramuscular technique and the continuous ment is not dependent on hourly injections, and the
low-dose intravenous infusion. 17,53 With either decrease in blood glucose concentration is more gradual
technique, regular insulin is administered with a desired using the intravenous protocol. An insulin solution is
effect of decreasing the blood glucose by not more than made by adding regular insulin at 2.2 U/kg for dogs
50 to 75 mg/dL/hr. Similar treatment has been used in and 1.1 U/kg for cats to 250 mL 0.9% saline. 52,53 This
cats with DKA. 52 solution is administered as a constant-rate infusion at
The low-dose intramuscular insulin protocol is an 10 mL/hr to deliver a dosage of 0.09 U/kg/hr in dogs
effective and straightforward, but somewhat time-con- and 0.045 U/kg/hr in cats. Because insulin may adhere
suming, method for insulin administration in DKA. 17 to plastic in the administration set, it is recommended
Intramuscular administration is recommended because that 50 mL of the insulin solution be allowed to flow
absorption from subcutaneous sites may be reduced or through the administration set before use. During insulin
inconsistent in the presence of dehydration. However, administration, intravenous fluid therapy with 0.9% saline
absorption is similar from the two administration sites is continued through a separate line as indicated for rehy-
in humans with DKA. 30 Regular insulin is the only prod- dration and maintenance needs. Blood glucose concen-
uct that has been reported to be used in dogs. Recently, tration is measured every 60 to 90 minutes. When the
subcutaneous administration of the insulin analogs insu- blood glucose is less than 250 mg/dL, the infusion rate
lin lispro and insulin aspart, have been shown to be as is decreased according to Table 20-1, and dextrose is
effective as intravenous regular insulin in humans with added to the hydration fluids to a final concentration of
uncomplicated DKA. 74,75 These analogs have a more 2.5% to 5% (see Table 20-1). 53 The primary disadvantage
rapid onset of action (10 to 20 minutes) compared with of the continuous low-dose intravenous infusion protocol
regular insulin (1 to 2 hours) and a shorter duration of is the need for an infusion pump and the time required to
effect. Any advantages over the use of regular insulin in monitor blood glucose serially.
veterinary medicine await investigation. In dogs the initial The high-dose intramuscular or subcutaneous insulin
dose of regular insulin is 0.2 U/kg intramuscularly, protocol is the simplest for management of DKA, requir-
followed by hourly measurement of blood glucose ing the least amount of monitoring and equipment. 12
concentrations. 17 Subsequent insulin administration However, it has some shortcomings, including a rapid
continues hourly at 0.1 U/kg intramuscularly until the decrease in blood glucose concentration that predisposes
blood glucose concentration is 250 mg/dL or less. Dogs to hypoglycemia, a greater magnitude of hypokalemia,
weighing less than 10 kg are given 2 U and cats are given and a substantial decrease in osmolality over a short
1 U initially, followed by 1 U every hour unless diluted period. It is for these reasons that this technique is no lon-
insulin is available. 17 If the blood glucose concentration ger used in humans and is considered less desirable for use
decreases by more than 100 mg/dL/hr, the dosage is in dogs and cats. Regular insulin is administered at
decreased. Once the blood glucose concentration is less 0.25 U/kg every 4 hours intramuscularly until the
than 250 mg/dL, the hourly insulin injections are patient is rehydrated, followed by subcutaneous adminis-
stopped, and 50% dextrose is added to the intravenous tration every 6 to 8 hours. 12 The dosage and frequency of
fluid solution in a quantity sufficient to make a 5% dex- insulin administration are based on monitoring blood
trose solution. Additional doses of regular insulin are glucose concentration hourly, with a goal of decreasing
administered every 4 to 6 hours at 0.1 to 0.4 U/kg the glucose concentration by approximately 50 mg/
subcutaneously with the dosage and dosing interval dL/hr. Once the glucose concentration is near
determined by measurement of blood glucose concentra- 250 mg/dL, dextrose is added to the intravenous saline
tion every 1 to 2 hours to maintain blood glucose concen- solution to a final concentration of 5%, and the
tration between 200 and 300 mg/dL. The primary subsequent insulin dosage is decreased by 25% to 50%.