Page 945 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

920 CHAPTER 6

VetBooks.ir At concentrations of 5–10%, i/v glucose administra- with GI disorders, such as proximal enteritis or post-
operative ileus that cannot receive enteral nutrition.
tion alone is not enough to meet maintenance energy
requirements, but it will help stop additional fat
trations or visual monitoring of plasma turbidity can
mobilisation from adipose tissue. Insulin adminis- Serial measurements of serum triglyceride concen-
tration may also help inhibit further fat mobilisation, be useful in evaluating response to treatment.
but hyperlipaemic horses often have some degree of
insulin resistance. Heparin (40–250 USP units/kg s/c Prognosis
q12 h) stimulates lipoprotein lipase and may enhance The prognosis is fair to poor when the syndrome
removal of lipids from blood. Lactulose (0.2 ml/kg has progressed to hyperlipaemia. The prognosis
p/o q12 h) administration to decrease ammonia pro- is worse in individuals with severe underlying dis-
duction and absorption may be useful in horses with ease that is difficult to treat. The prognosis is bet-
hepatic encephalopathy. Unless absolutely required ter in individuals whose triglycerides return to the
for the treatment of underlying disease, glucocorti- normal range within 3–10 days of treatment. Best
coid administration should be avoided since steroids results are achieved when the syndrome is recog-
stimulate hormone-sensitive lipase. nised in at-risk individuals in the hyperlipidaemia
Severe cases of hyperlipaemia, especially in debili- stage. Starting i/v glucose infusions (5%), with or
tated animals, may require partial or total parenteral without added insulin, before the horse’s triglycer-
nutrition (without the lipid component) initially. ides exceed 6.65 mmol/l (500 mg/dl) can help stop
Partial or total parenteral nutrition is also useful for fat mobilisation and prevent exacerbation of the
hyperlipidaemic or hyperlipaemic horses or ponies syndrome.

MISCELLANEOUS DISEASES OF THE ENDOCRINE SYSTEM

DIABETES MELLITUS hyperglycaemia with glycosuria, polyuria and poly-
dipsia, after ruling out more common disease such as
In recent years there has been increasing interest and EMS and PPID.
attention paid to insulin resistance and the proposed
occurrence of type-2 diabetes in horses. Horses with ADRENAL INSUFFICIENCY
PPID and EMS may be insulin resistant and, per-
haps, all obese horses have some degree of insulin Definition/overview
resistance. However, very few horses go on to develop Glucocorticoid and mineralocorticoid hormones
the hyperglycaemia that is the hallmark of frank are essential for maintenance of normal homeostatic
diabetes mellitus. Although case reports of diabetes mechanisms and response to stress. Failure of the
mellitus exist in the older literature, descriptions of adrenal gland to respond despite normal ACTH
these horses are most consistent with a diagnosis secretion is considered primary adrenal insuffi-
of PPID. Primary clinical features include polyuria ciency, while decreased ACTH secretion is termed
and polydipsia secondary to hyperglycaemia and glu- secondary adrenal insufficiency. There are some
cosuria. Horses that exhibit polyuria and polydipsia animals that can produce baseline amounts of cor-
should be tested for PPID and have their renal func- tisol, but do not increase the release of cortisol in
tion examined. an appropriate manner in the presence of severe
Type-2 diabetes mellitus is a rare disease in horses metabolic stressors such as sepsis. This disorder has
as they can produce large amounts of insulin and been termed relative adrenal insufficiency (RAI) or
rarely develop pancreatic exhaustion. Nevertheless, critical illness-related corticosteroid insufficiency
a few cases have been reported suggesting that the (CIRCI). RAI has been documented in both adult
disease should be investigated in cases of sustained horses and neonatal foals.