Content – Hypoglycemia

last authored: Sept 2016, Jessica Francis

Draft – Pending Final Review

Introduction

Hypoglycemia, or low blood glucose, occurs when there is an imbalance of insulin and glucose in the blood (too much insulin in proportion to glucose). Glucose is a primary energy source for the human brain, which means the brain is in constant need of a sufficient supply to maintain proper function. During hypoglycemia, glucose levels decrease, resulting in impaired cognitive function.

Hypoglycemia is characterized by the following three things:

1. A blood glucose level of less than 4mmol/L (70mg/dl)
2. CNS symptoms such as confusion, erratic behaviour, coma etc.
3. Resolution of symptoms within minutes of glucose administration

Causes and Risk Factors

Hypoglycemia can be triggered by various factors.

Medication-induced Hypoglycemia

Hypoglycemic symptoms may occur when blood glucose levels fall too rapidly due to a mismatch of caloric intake and hypoglycemics, especially insulin.

Hypoglycemia and Alcohol

Hypoglycemia can produce many of the symptoms of alcohol intoxication, such as agitation, impaired judgment and irritability. Patients who use insulin as part of intensive therapy are at increased risk of hypoglycemia several hours after drinking alcohol. Different types of alcohol will affect blood glucose levels differently, depending on carbohydrate content and if mixed with other substances.

Alcohol inhibits the liver’s ability to release glucose through reduced gluconeogenesis, especially in people with depleted glycogen stores. This impairment can last hours after alcohol consumption, which can cause hypoglycemia when sleeping. Those taking diabetic medications, such as insulin, should take extra carbohydrates prior to going to bed.

Postprandial Hypoglycemia

Exaggerated insulin release can follow a meal, especially if there is a mismatch in timing of ingestion of food and peak action time of insulin or oral hypoglycemic agents. For this reason, it is recommended to eat frequent small meals.

Fasting Hypoglycemia

Fasting hypoglycemia tends to produce neuroglycopenic symptoms and may result from decreased liver production of glucose (ex. in patients with liver damage). It may also result from increased peripheral glucose use, often due to increased insulin levels due to a pancreatic tumour.

Hypoglycemic unawareness (or asymptomatic hypoglycemia) is characterized by a person not experiencing signs or symptoms of hypoglycemia. This increases the risk of blood glucose levels dropping to a dangerous level.

Hypoglycemic unawareness is related to autonomic neuropathy, which reduces epinephrine release and attending sympathetic symptoms, described below. Elderly and patients using beta blockers are at increased risk of hypoglycemic unawareness. If hypoglycemia unawareness is present, patients should typically aim for higher glucose levels.

Risk factors for hypoglycemia include (Canadian Diabetes Association):

• history of previous hypoglycemia
• hypoglycemia unawareness
• increased age
• impaired cognitive status
• autonomic neuropathy
• long duration of insulin therapy
• current low A1C
• renal dysfunction
• low socioeconomic status, poor health literacy, food insecurity

Pathophysiology

Insulin is a natural hormone produced in the pancreas by beta cells, and serves to allow glucose into cells to provide energy. In Type 1 Diabetes, the body attacks its beta cells, resulting in little or no insulin being released into the body. Thus, insulin administration is required to regulate blood glucose levels. In Type 2 Diabetes, the body is unable to properly utilize its insulin (insulin insensitivity), or not enough insulin is being produced. Type 2 Diabetes is usually managed through physical activity and meal planning and may require medications and/or insulin to control blood sugar as well.

Glucagon and epinephrine, together with a decrease in insulin, are the most important physiological responses to hypoglycemia. When blood glucose levels drop below 4mmol/L or 70mg/dL, glucagon is produced by the pancreas to result in glycogenolysis. In this process,  glycogen that is stored in the liver is converted into glucose, which is then released into the bloodstream. In Type 1 Diabetes, where glucagon secretion is impaired, epinephrine acts as the principal hormone, acting on both liver and muscle to liberate glucose through glycogenolysis.

The brain is very dependent on blood glucose levels, and temporary hypoglycemia can rapidly cause cerebral dysfunction, with symptoms below.

History and Physical Exam

Symptoms of hypoglycemia typically appear when glucose levels drop below 50mg/dL (2.8mmol/L), however there is no direct correlation between symptoms and glucose levels. Each individual may or may not display different symptoms at different glucose levels.

While assessing the patient, inquire into:

• Is the patient diabetic?
• What medications (especially diabetes medications) is the patient taking?
• When were medications last given?
• When was the last meal, and what was eaten?
• Is there a history of previous hypoglycemic episodes?
• Has the patient recently had surgery?
• Has the patient had any recent drug or alcohol ingestion?
• Has the patient had any recent infections?

Signs and symptoms of hypoglycemia may be autonomic – resulting from the release of epinephrine to raise glucose levels, as well as neuroglycopenic – resulting from brain deprivation of glucose.

Investigations

Depending on the setting and context, tests to consider may include:

• serum blood glucose
• electrolytes
• BUN and creatinine
• ketones (beta-hydroxybutyrate, acetate)
• urinalysis
• blood gases

If the cause remains unclear, further testing could include levels of:

• cortisol
• insulin, proinsulin, C-peptide
• growth hormone

Differential Diagnosis

All patients who present with altered mental status should have a blood glucose level taken.

Other causes that should be considered in a patient presenting with the symptoms above should include:

• intoxication
• head trauma
• anxiety
• adrenal crisis
• Addison’s disease
• shock (many causes)

Management

Recognize this as an emergency, and act quickly to treat, based on clinical status and setting.

Conscious Patient

Administer 15-20g of fast acting carbohydrates (simple carbohydrates such as commercial dextrose tablets, 175mL of fruit juice, 6-8 lifesavers, or 3 packages of sugar in water).

Repeat if no improvement within 15 minutes

If no significant improvement after 2-3 doses of simple carbohydrates, consider injection of glucagon.

Administer additional longer-acting food combinations after symptoms subside, especially if the next meal is more than 1 hour away. Foods to consider include crackers and peanut butter or cheese.

Unconscious Patient (or severe hypoglycemia)

Call for help if appropriate.

Provide basic life support as needed.

Provide glucagon sub cut or IM.

Begin an IV and administer 25-50 mL dextrose 50% in water (D50W), given over 1-3 minutes.

Continue to closely monitor vital signs and blood glucose levels.

Followup Care

Determine the cause of hypoglycemia episodes, and adjust medications or meals to reduce the risk.

Proper education is required for patients taking medications to regulate their blood glucose levels.

Resources and References

Briscoe, V. J., & Davis, S. N. (2006). Hypoglycemia in Type 1 and Type 2 Diabetes: Physiology, Pathophysiology, and Management. Clinical Diabetes, 24(3), 115-121.

Canadian Diabetes Association (CDA) Clinical Practice Guidelines Expert Committee (2008). Clinical practice guidelines for the prevention and management of diabetes in Canada. Canadian Journal of Diabetes Care, 32(Suppl), S1-S201.

Clayton et al. 2013. Hypoglycemia. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee

Lewis, S.L., Heitkemper, M.M., Dirksen, S.R., Bucher, L, & O’Brien, P.G. (2010). Medical-surgical nursing in Canada. Toronto: Elsevier Canada.