T1DM Flashcards
What is T1DM?
Cause?
Type 1 diabetes mellitus (T1DM) is a disease where the pancreas stops being able to produce insulin. What causes the pancreas to stop producing insulin is unclear. There may be a genetic component. It may be triggered by certain viruses, such as the Coxsackie B virus and enterovirus.
What happens to blood glucose level in T1DM?
When the pancreas is not producing insulin, the cells of the body cannot take glucose from the blood and use it for fuel. Insulin acts like a key that lets glucose into the cell. Therefore, when there is no insulin, the cells think there is no glucose in the blood and the body is being fasted. The cells cannot use glucose, so the level of glucose in the blood keeps rising, causing hyperglycaemia.
Basic physiology of carbohydrate metabolism?
Eating carbohydrates causes in a rise in blood glucose levels. As the body uses these carbohydrates for energy there is a fall in blood glucose levels. The body ideally wants to keep the blood glucose concentration between 4.4 and 6.1 mmol/l.
Insulin is a hormone produced by the pancreas that reduces blood sugar levels. Insulin is produced by the beta cells in the Islets of Langerhans in the pancreas. It is an anabolic hormone (a building hormone). It is always present in small amounts, but increases when blood sugar levels rise.
Insulin reduces blood sugar in two ways: Firstly, it causes cells to absorb glucose from the blood and use it as fuel. Secondly, it causes muscle and liver cells to absorb glucose from the blood and store it as glycogen. Insulin is essential in letting cells take glucose out of the blood and use it as fuel. Without insulin, cells cannot take up and use glucose.
Glucagon is a hormone that increases blood sugar levels. It is produced by the alpha cells in the Islets of Langerhans in the pancreas. It is a catabolic hormone (a breakdown hormone). It is released in response to low blood sugar levels and stress. It tells the liver to break down stored glycogen into glucose. This process is called glycogenolysis. It also tells the liver to convert proteins and fats into glucose. This process is called gluconeogenesis.
Ketogenesis occurs when there is insufficient supply of glucose, and glycogens stores are exhausted, such as in prolonged fasting. The liver takes fatty acids and converts them to ketones. Ketones are water soluble fatty acids that can be used as fuel. They can cross the blood brain barrier and be used by the brain. Producing ketones is normal and not harmful in healthy patients when under fasting conditions or on a very low carbohydrate, high fat diet. People in ketosis have a characteristic acetone smell to their breath.
How does T1DM present?
About 25 – 50% of new type 1 diabetic children present in diabetic ketoacidosis (DKA). This is the result of a situation where the pancreas can no longer produce enough insulin to maintain basic blood glucose regulation.
The remaining paediatric patients present with the classic triad of symptoms of hyperglycaemia:
Polyuria (excessive urine)
Polydipsia (excessive thirst)
Weight loss (mostly through dehydration)
Other less typical presentations include secondary enuresis (bedwetting in a previously dry child) and recurrent infections. Symptoms are usually present from 1 to 6 weeks prior to developing DKA, however this can vary significantly.
How is T1DM diagnosed?
Baseline bloods including FBC, renal profile (U&E) and blood glucose
Blood cultures should be performed in patients with suspected infection (i.e. with fever)
HbA1c can be used to get a picture of the blood sugar over the previous 3 months. This gives an idea of how long they have been diabetic prior to presenting.
Thyroid function tests and thyroid peroxidase antibodies (TPO) to test for associated autoimmune thyroid disease
Tissue transglutaminase (anti-TTG) antibodies for associated coeliac disease
Insulin antibodies, anti-GAD antibodies and islet cell antibodies to test for antibodies associated with destruction of the pancreas and the development of type 1 diabetes
Long term management of T1DM?
Management involves the following components:
Subcutaneous insulin regimes
Monitoring dietary carbohydrate intake
Monitoring blood sugar levels on waking, at each meal and before bed
Monitoring for and managing complications, both short and long term
Insulin regimes for T1DM?
Insulin is usually prescribed as a combination of a background, long acting insulin given once a day, and a short acting insulin injected 30 minutes before the intake of carbohydrates (i.e. at meals). Alternatively, insulin can be administered by an insulin pump. Insulin regimes are initiated by a diabetic specialist.
Basal Bolus Regimes
Patients are usually initiated on a basal-bolus regime.
The basal part refers to an injection of a long acting insulin, such as “Lantus”, typically in the evening. This gives a constant background insulin throughout the day.
The bolus part refers to an injection of a short acting insulin, such as “Actrapid”, usually three times a day before meals. This is also injected according to the number of carbohydrates consumed every time the patient has a snack.
Insulin Pump
Insulin pumps are small devices that continuously infuse insulin at different rates to control blood sugar levels. They are an alternative to the basal bolus regimes. The pump pushes insulin through a small plastic tube (cannula) that is inserted under the skin. The cannula is replaced every 2 – 3 days and the insertion sites are rotated to prevent lipodystrophy and absorption issues.
To qualify for an insulin pump funded by the NHS the child needs to be over 12 and have difficulty controlling their HbA1c. Local criteria may vary.
The advantages of an insulin pump are better blood sugar control, more flexibility with eating and less injections. The disadvantages are difficulties learning to use the pump, having it attached at all times, blockages in the infusion set and a small risk of infection.
Potential complication of insulin injection?
Injecting into the same spot repeatedly can cause a condition called lipodystrophy, where the subcutaneous fat hardens and prevents normal absorption of insulin when further doses are injected into this area. For this reason patients should cycle their injection sites. If a patient is not responding to insulin as expected, ask where they inject and check for lipodystrophy.
Types of insulin pump?
There are two types of insulin pump:
Tethered pump
Patch pump
Tethered pumps are devices with replaceable infusion sets and insulin. They are usually attached to the patients belt or around the waist with a tube that connects from the pump to the insertion site. The controls for the infusion are usually on the pump itself.
Patch pumps sit directly on the skin without any visible tubes. When they run out of insulin the entire patch pump is disposed of and a new pump is attached. Patch pumps are usually controlled by a separate remote.
Short term complications of T1DM?
Hypoglycaemia
Hyperglycaemia (and DKA)
Hypoglycaemia?
Symptoms?
Hypoglycaemia is a low blood sugar level. In diabetes this is caused by too much insulin, not enough carbohydrates or not processing the carbohydrates properly, for example in malabsorption, diarrhoea and vomiting and sepsis. Most patients are aware when they are hypoglycaemic by their symptoms, however some patients can be unaware until severely hypoglycaemic.
Typical symptoms are hunger, tremor, sweating, irritability, dizziness and pallor. More severe hypoglycaemia will lead to reduced consciousness, coma and death unless treated.
Treatment hypoglycaemia?
Hypoglycaemia needs to be treated with a combination of rapid acting glucose such as lucozade and slower acting carbohydrates such as biscuits or toast to maintain the blood sugar level when the rapid acting glucose is used up.
Options for treating severe hypoglycaemia where there is impairment of consciousness, seizures or coma, and oral glucose would not be safe, are IV dextrose and intramuscular glucagon. IM glucagon does not require a cannula. If a cannula is sited then 10% dextrose solution can be given according to local protocols, for example 2mg/kg bolus followed by a 5mg/kg/hour infusion.
Causes of hypoglycaemia in T1DM?
In diabetes this is caused by too much insulin, not enough carbohydrates or not processing the carbohydrates properly, for example in malabsorption, diarrhoea and vomiting and sepsis.
Other causes of hypoglycaemia include hypothyroidism, glycogen storage disorders, growth hormone deficiency, liver cirrhosis, alcohol and fatty acid oxidation defects (such as MCADD).
Nocturnal hypoglycaemia?
Nocturnal hypoglycaemia is a common complication. The child may be sweaty overnight. Morning blood glucose levels may be raised. Diagnosis of nocturnal hypoglycaemia can be made by continuous glucose monitoring. It can be treated by altering the bolus insulin regimes and snacks at bedtime.
Hyperglycaemia treatment?
Patients that are hyperglycaemic, but not in DKA, may require their insulin dose to be increased. Patients will get to know their own individual response to insulin and be able to administer a dose to correct the hyperglycaemia. For example, they may learn that 1 unit of novorapid reduces their sugar level by around 4 mmol/l. Be conscious that it can take several hours to take effect and repeated doses could lead to hypoglycaemia.
When they meet the criteria for DKA they need admission for inpatient management.
