Canine diabetes mellitus Flashcards
Outline the effects of insulin?
What are the actions of insulin after injection?
Describe the types of diabetes as stated by WHO?
Type 1: (beta–cell destruction, usually leading to absolute insulin deficiency)
- Immune-mediated (including LADA)
- Idiopathic
Type 2: (may range from predominantly insulin resistance with relative insulin deficiency to a predominantly secretory defect with or without insulin resistance)
What are some of the sources of type and type 2 diabetes?
Production (~Type 1)
- Pancreatectomy
- Pancreatitis
- Auto-immunity
- Islet cell hypoplasia
- Chemical toxicity
Target (~Type 2)
- Progesterone/agen (females more common)
- Growth hormone
- Glucocorticoids
- Glucagon
- Catecholamines
- Thyroid
- Obesity
What is the aetiology of canine diabetes mellitus?
Insulin-deficient (Type 1 like):
- Immune-mediated (probably common)Antibodies in circulation against islet Ag
- (e.g. insulin, GAD-65, insulinoma antigen-2
- DLA subtypes predisposed (MHC)
- (Samoyed, Tibetan Terrier)
- b loss due to EPI / pancreatitis (probably common)
- Congenital b loss (rare)
Insulin-resistant (Type 2 like):
- Progesterone (e.g. metoestrus) - an acromegaly (common)
- Hyperadrenocorticism, exogenous corticosteroids
- IGF-1/GH excess (pituitary acromegaly extremely rare)
Almost all diabetic dogs are insulin dependent
Exceptions include:
- Bitches presenting in metoestrus with high levels of progesterone (inducing mammary origin growth hormone excess)
- Dogs with concurrent Cushing’s disease
- May or may not be insulin-dependent
- If not treated irreversible beta-cell damage is likely to occur and the dog will become IDDM
What is the clinical presentation of diabetes mellitus?
DM is generally a disease seen in older dogs
- Peak age of incidence is 7 – 9 y/o
- Female > male cases by approx 2:1
Juvenille-onset DM has been reported but is rare
- Usually develops < 1 year of age
Name some breeds predisposed to DM?
- Australian terrier
- Standard schnauzer
- Miniature schnauzer
- Bichon frise
- Spitz
- Fox terrier
- Miniature poodle
- Samoyed
- Cairn terrier
- Keeshond
- Maltese
- Toy poodle
- Lhasa apso
- Yorkshire terrier
- Collie
- GSD
What is the usual clinical presentation of diabete mellitus in the dog?
Classic presentation of “starvation in the midst of plenty”
- Polyphagia but losing weight (insulin is required in hypothalamic satiety centre as this has an insulin dependent mechanism that recognises how much)
- Polydipsia and polyuria (osmotic diuresis)
- Quickly tired/poor exercise tolerance/sleepy
- Diabetic cataracts
- Recurrent infection (e.g.UTI)
- “Acetone” breath
- Most owners therefore present due to nocturia/urinary incontinence
- Occasionally present due to “sudden onset blindness”
What is the pathophysiology of the clinical presenting signs of diabete mellitus?
Pathophysiology
- Polyuria, polydipsia
- Osmotic diuresis
- Polyphagia
- Insulin in CNS – hypothalamic satiety centre
- Weight loss/exercise intolerance/lethargy
- Negative energy balance
- Reduced glucose and AA uptake
- Recurrent infection (esp. UTI (glucose in urine feeds the bugs, conjunctivitis)
- Immunological compromise
- Local conditions favour microbial growth
- Ketotic breath (smells like acetone (nail varnish remover))
- Ketogenesis
- Cataracts
- Osmotic effects
How are diabetic cataracts formed?
WHEN GLUCOSE NOMALLY GETS IN LENSE IT IS METABOLISED BY HK WHEN TOO MUCH GLUCOSE A DIFF PATHWAY METABOLISED EXCESS GLUCOSE AND THIS DRAWS WATER INTO THE LENS.
How can an acute clinical presentation manifest?
Occasionally the first signs of illness are acute when the dog develops diabetic ketoacidosis (DKA)
- Dull, depressed, weak, possibly comatose
- Often vomiting
- Dehydrated
- IV fluids and critical care
Ketonuria/ketotic breath ≠ DKA
- If eating and drinking – still straightforward management
How should diabetes be investigated?
Urinalysis standard part of PU/PD work-up
- Glucosuria
- Glucosuria without hyperglycaemia is not DM (renal tubular disease)
Other lab findings:
- Raised ALKP / ALT (liver swollen with metabolic activity)
- Raised cholesterol, triglycerides
- Fasting hyperglycaemia
- +/- hyponatraemia
- +/- ketonuria, ketonaemia
- Fructosamine (GOOD MEASURE FOR DIABETIC CATS due to stress hyperglycaemia it is more clear cut in dogs)
- Urine culture
How can diabetes melltius be diagnosed in the canine?
- Hyperglycaemia
- fasting hyperglycaemia
- >12mmol/l usually
- >5.5 – 12mmol/l more challenging
- Glucosuria
- Renal threshold ~ 10-12mmol/L
- +/- Ketonuria
- Fructosamine
- The non-enzymatic binding of glucose to albumin
- Levels of fructosamine are dependent on the half-life of albumin and give an indication of glycaemic control over the preceding 2-3 weeks
- ? Accuracy
- Useful but be careful when interpreting results
- A fructosamine of > 400mmol/l is highly suggestive of diabetes mellitus
- Differentiates long term high glucose from short term high glucose (e.g. stress hyperglycaemia
- Caution (false negatives) if PU/PD history very recent
What are the aims of treatment?
- Prevent life threatening ketoacidosis
- Abolish clinical signs
- Restore lost condition/weight
- Reduce risk of complications
With regards to treatment and the dog is IR what needs to be considered when treating?
Insulin
- Type and frequency of administration
Diet
- Must be carefully assessed
Body condition
Lifestyle
- Availability for 12hourly injections
- Availability for monitoring (e.g., hypoglycaemia)
- Ongoing costs
When to spay intact female
What is the licensed insulin for dogs?
- One licenced product for dogs
- Caninsulin, MSD
- Intermediate acting preparation
- Lente (mixed insulin zinc suspension)
- Usually given twice daily but sometimes once
- Initial dose 0.5 iu/kg BID
- Most patients require between
- 0.8 – 1.2 iu/kg/dose to stabilise
- 40IU/ml – must use companion syringes with vial product
- Owners must be counselled regarding their handling of insulinInsulin should be kept between 2-8oC
- Fridge door often best (unless internal freezer)
- The insulin should not be shaken, just gently rolled prior to drawing up dose
- Insulin beyond its expiry date may be ineffectual
- Manufacturers recommend discard bottle after 28 days in use
Interpret these blood glucose curves?
For the curve below, determine the values for the 4 measures described above. Insulin was injected at 0800, just after the first blood sample was drawn. This patient is receiving insulin twice daily at 0800 and 2000.
Onset of insulin = 2h
Duration of action = 10h
Lowest glucose concentration = 6.4 mmol/L
Time of nadir (peak effect) = 4h (at noon)
Many diabetic dogs will have blood glucose concentrations that rise above the renal glucose threshold at certain times of the day. However, it is the duration of hyperglycemia (and therefore glucosuria) that becomes important. Draw a line of the graph to indicate the approximate value for the renal threshold and estimate the number of hours that the dog will experience glucosuria each day. Some glucosuria can be tolerated (i.e. PU/PD does not develop; subclinical), but this is a key component of diabetes management and should be minimised.
Draw line at 10 mmol/L
Draw a schematic for making decision about DM treatment based on BGC?
Using the guidelines provided below, please interpret the following curves and provide recommendations.
Curve 1: Dog receives 0.25 IU/kg lente insulin (Caninsulin®) at 0800 and 2000.
Interpretation: Insulin is effective and the duration of action is adequate, yet there is inadequate control of hyperglycemia
Recommended action: Increase dose by 20% (from 0.25 IU/kg to 0.30 IU/kg) and recheck in 7 days. Remember that most dogs require dosages of 0.8 to 1.2 IU/kg once or twice daily.
Using the guidelines provided below, please interpret the following curves and provide recommendations.
Curve 2: Dog receives 0.8 IU/kg lente insulin (Caninsulin®) once daily at 0800.
Interpretation: Insulin is effective, but the duration of action is too short. Although the curve was stopped at 10PM, there was no further insulin action.
Recommended action: Switch to twice daily insulin injections. Lower dose by 20%, give every 12h, and recheck in 7 days.
Using the guidelines provided below, please interpret the following curves and provide recommendations.
Curve 3: Dog receives 2.5 IU/kg lente insulin (Caninsulin®) once daily at 0800.
Interpretation: This dog is demonstrating the Somogyi effect (also called ‘overswing’) where the insulin dosage is too high and the blood glucose concentrations are being lowered too far. Mechanisms to protect the dog against hypoglycaemia are then activated, including release of glucagon, cortisol, and epinephrine. These hormones induce hyperglycemia, which then resolves slowly over the next few hours.
Recommended action: Reduce the dosage by 75% or return to starting dosages for canine diabetes mellitus (0.25 to 0.50 IU/kg q12h). Recheck after 7 days.
