Hypoglycaemia Flashcards
Definition of hypoglycaemia
Blood glucose concentration of less than 3.3 mmol/L
Sources of glucose in the body
- intestinal absorption from the digestion of carbohydrates,
- dissolution of glycogen (the storage form of glucose) via glycogenolysis predominantly in the liver but also in the muscle,
- synthesis of glucose (gluconeogenesis), mostly by the liver, from non-carbohydrate sources e.g., lactate, pyruvate, amino acids, and glycerol, but also a significant amount by the kidneys.
Euglycaemic control
Glucose lowering hormones
- insulin
Glucose elevating hormones
- Glucagon
- catecholamines
Normal hepatic blood supply and funtioning hepatocytes
Typical causes of hypoglyaemia
- excessive uptake of glucose by normal or neoplastic cells
- Impaired hepatic gluconeogenesis or glycogenolysis
- a deficiency in diabetogenic hormones
- inadequate dietary intake of glucose
- combination
Main differentials for profound, symptomatic hypoglycaemia
Neoplasia
- pancreatic
- extra-hepatic
Hepatic disease
- decreased hepatic gluconeogenesis
Hypoadrenocorticism
- lack of cortisol (counter regulatory hormone)
Sepsis/SIRS
- decreased hepatic glycogenesis
- increased glucose utilisation
Iatrogenic inappropriate administration of insulin
Drugs/toxicities
- xylitol
- insulin overdose
Paraneoplastic hypoglycaemia/other tumours
Stressor in juveline toy breeds
Starvation
Hunting dog hypoglycaemia
Artefactual/spurious
Clinica signs og hypoglycaemia
Depends on severity and duration
Intermittent or persistent
Seizures
Weakness
Collapse
Ataxia
Less commonly - lethargy, tremors, blindness
Emergency treatment of symptomatic hypoglycaemia
GIVE GLUCOSE!
But administer 50% glucose or dextrose solution IV in SMALL AMOUNTS and SLOWLY (to avoid rebound hypoglycaemia)
Commonly 0.5ml/kg of a 50% solution, remember to dilute
If failure to respond, then Dexamethasone IV
Effects of steroids on glycaemia:
§ Stimulation of gluconeogenesis
§ Inhibition of glucose uptake into tissues
§ Antagonises the effects of insulin directly by decreasing the sensitivity of insulin receptors
Glucagon injection very rarely used in veterinary medicine
If the dog of cat is having a hypoglycaemic seizure at home, owner can rub sugar mixture on the animal’s gums. Once it is aware of its surroundings, it should be fed a small meal. Then brought to the practice for assessment
After the initial emergency control, if not already done:
· Blood analysis (biochemistry and bile acids, ACTH)
· Blood pressure
· Establish IV line
· Urinalysis
· Set up for imaging, US/radiology (e.g. a septic peritonitis)
Insulinoma
Pancreatic beta cell tumours or insulinomas are uncommon in the dog and rare in the cat.
In dogs 95% of insulinomas are considered to be aggressive malignant tumours.
Surgery is still considered to be the single most appropriate treatment but unfortunately at the time of surgical intervention most dogs will already have microscopic or grossly visible evidence of metastatic disease.
Insulinoma is therefore a clinical syndrome that we are left to manage rather than cure in the majority of cases.
Metastases to the liver, local LNs, and omentum is seen in 50% of dogs
Clinical presentation of insulinoma
Middle aged to old dogs.
Large breed dogs mainly.
Certain breed predispositions e.g. GSD, Boxer, Golden retriever, Labrador retriever
Clinical signs are typically episodic
Signs usually increase in severity
Late presentation partly explains why the metastatic rate is so high at the time of diagnosis.
Subtle signs due to stimulation of the sympatho-adrenal system.
The onset of neuroglycopenic signs can be delayed by up-regulation of glucose transporters at the blood brain barrier as an adaptive response to chronic severe hypoglycaemia.
Once these signs develop however, urgent and effective treatment is mandatory as irreversible brain lesions are known to occur in people and have been reported in a dog and a cat with persistent hypoglycaemia.
DIagnosis of insulinoma
Documentation of hypoglycaemia
Insulin assay
Diagnostic imaging
Staging insulinomas
Stage I: insulinoma confined to pancreas
Stage II: insulinoma with regional lymph node metastasis
Stage III: insulinoma with distant metastasis
Management of the stable insulinoma patient
Surgery
Dietary management
- small frequent feeds
- high fat, protein and complex carbohydrate
Prednisolone
- to induce peripheral insulin resistance
Diazoxide
- inhibits pancreatic beta cell insulin production
Streptozotocin
- specific cytotoxic agent for beta cells
Prognosis of insulinoma
Guarded
66-75% of dogs survive >6mo before intractable hypoglycaemia develops
Survival for surgical managed cases: median 381 days (range 20-1758)
Survival for medically managed cases: median 74 days (range 8-508)
