Diabetes and it's treatment (ILO/IMO Guidelines Appendix E E 10-14)

Introduction

Diabetes presents in two main forms but there may be overlap between them:

• Type 1. This form is associated with a lack of insulin production by the body. Untreated it progresses to death but injected insulin will enable the body to continue to handle the transport of glucose into cells.
• Type 2. Associated with increasing resistance to the effects of insulin. Slower progression and this may be delayed by dietary adjustment and weight loss, by the use of oral medication or by insulin.

Both forms increase the risk of disease of blood vessels. Large vessel disease increases the risk of arterial disease including heart attacks and stroke. Small vessel disease leads to retinal disease, neuropathy and loss of sensation in the extremities, skin atrophy and kidney disease. These effects can be slowed or even prevented by active treatment.
Insulin treatment has to balance the dose used and its timing against the body's intake and use of glucose. If this is out of balance because of changes to eating habits or exercise it may lead to either low blood glucose (hypoglycaemia) causing cognitive impairment and collapse, or to high blood glucose (hyperglycaemia) with an increased long term risk of blood vessel damage. There is also a risk of diabetic (hyperglycaemic) coma. Some oral medications (sulphonoureas) can also cause hypoglycaemia, although normally less severe than that caused by excess insulin.
Diabetes is commonly found because of routine urine and blood testing but it may present as increased urination and thirst, with skin infection, with tiredness and, especially in young people with type 1 diabetes, as hyperglycaemic keto-acidosis and coma.

Impairment and Risks

• Performance at tasks, including safety critical ones, may be reduced by impaired cognitive function from hypoglycaemia as a result of insulin use.
• The development of hypoglycaemia can be unpredictable but missing a meal, exercising more than usual or taking alcohol are common causes.
• Visual loss or reduced sensation from associated microvascular disease may occur, usually but not always at a late stage of diabetes.
• In those who use insulin there will be an increased risk to the individual from imbalances between the disease and the treatment given. This may be exacerbated by changes in food intake, for instance from gastro intestinal infection or sea-sickness or in response to other illnesses or injuries.
• Diabetes may be associated with other endocrine diseases and is a risk factor for vascular diseases such as heart attack and stroke.

Rationale and justification – insulin and hypoglycaemia

• Impairment from hypoglycaemia (hypo) is complex.
• There is good evidence that mild hypoglycaemia (3-4 mmol/litre) induces cognitive impairment. This may cause slowing of responses, poor judgement of risk or behavioural changes with increased aggression and risk taking. It can also blunt awareness of and responses to the warning signs of low blood glucose.
• More severe reductions in blood glucose can lead to frank incapacity and loss of consciousness.
• Perception of early symptoms of a hypo may diminish over time. Early identification of a hypo greatly reduces the risk of consequential incapacitation as oral carbohydrates can be taken to remedy the hypo. The time course from first awareness to incapacity is variable over a period of seconds or minutes.
• Recovery time following a remedy is, in subjective terms, rapid but there is measurable cognitive impairment for a period of up to sixty minutes or more, suggesting that return to safety critical tasks should not be immediate.
• Among those at risk of hypoglycaemia the probability of an episode and its severity vary widely. There is currently little valid information that can be used to stratify and predict risk based on age, the duration and severity of the diabetes or the dose or regime of insulin.
• Hypoglycaemia while undertaking safety critical tasks is not uncommon. As many as 32% of insulin users reported that they had experienced hypoglycaemia while driving, 13% in the last year.
• Irregular working hours, for instance in maritime watchkeeping, will make regulating the balance between insulin dose and food consumption difficult, hence increasing the risk of hypoglycaemia.
• Situations that prevent food intake such as sea sickness and other causes of nausea and vomiting will, unless the insulin dose is carefully adjusted, increase the risk of hypoglycaemia.
• Increased levels of exercise will raise the body's demand for glucose and so increase the risk of hypoglycaemia unless the insulin dose is also adjusted.
• Alcohol use increases the risk of hypoglycaemia by blocking glucose release from the liver to meet demands elsewhere. This effect is most marked if alcohol is consumed on an empty stomach.
• There is evidence that, at least for the first few years on insulin, those who have type 2 diabetes are at lower risk of hypo (no dot) than those with type 1 diabetes.
• An individual who has a pattern of repeated reductions in blood glucose found on blood glucose monitoring, but without symptoms, is more likely to have a severe hypoglycaemic episode than someone who has a stable blood glucose level.
• Insulin is the major cause of hypos but oral sulphonyl urea medications can also sometimes reduce blood glucose to impairing levels. Treatment with combinations of medications, usually but not always including insulin, also increases the risks of hypoglycaemia.

Rationale and justification – other aspects

• Personal behavioural aspects pose one of the largest problems in determining individual risk. Someone who is careful about maintaining the control of their diabetes, manages it assiduously and does not let the pressures of life or work override management of diabetes is likely to be able to maintain far more predictable blood glucose control than someone with irregular eating, activity and monitoring habits.
• There is case series evidence indicating that failures in the control of diabetes have led to medical emergencies at sea. Some have been fatal, while many more have needed medevac to hospital. Some have arisen from a failure to disclose or identify the condition at medical examination.
• There are no reliable predictive measures to identify whether an individual is at high risk of loss of control. However a good track record of control with steady blood glucose levels can be a helpful indicator.
• Self-monitoring of blood glucose levels enables someone using insulin both to reduce their risk of hypoglycaemia and to keep their blood glucose control optimum.
• A person with a diagnosis of diabetes has a similar excess risk of having a sudden vascular event (heart attack, stroke etc) as a person of the same age and sex who has already had one such event.

Clinical assessment and decision taking

Diabetes will either present as an established diagnosis, as a referral because the condition has just been diagnosed as a finding at examination, usually glycosuria, but sometimes because of suspicious symptoms such as thirst and polyuria or ketosis.