Hypoglycaemia
Reading File
Asking for Preferences
Finding Sources
Searching PubMed
hypoglycemia management
Finding Sources
Finding Sources
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
I have enough rich content from the textbooks to compile a thorough, exam-focused overview. Let me now write the comprehensive answer.
Hypoglycaemia - Complete Overview
Definition
Hypoglycaemia is defined clinically by Whipple's Triad:
- Symptoms and/or signs compatible with hypoglycaemia
- A low measured plasma glucose concentration
- Resolution of symptoms when glucose concentration is raised
There is no single plasma glucose value that categorically defines hypoglycaemia in adults, but symptomatic hypoglycaemia most commonly occurs below 40-50 mg/dL (2.2-2.8 mmol/L). The normal fasting plasma glucose range is 70-110 mg/dL (3.8-6.0 mmol/L).
Key exam point: Whipple's Triad is the gold standard for confirming hypoglycaemia - a low glucose alone is insufficient.
Physiology of Glucose Regulation
The brain is the key organ at risk because:
- Glucose is its obligate metabolic fuel
- It cannot oxidize fatty acids
- It cannot synthesize or store glucose
Plasma glucose is maintained by balancing:
- Inputs: intestinal absorption, glycogenolysis, gluconeogenesis (from lactate, pyruvate, alanine, glutamine, glycerol)
- Outputs: uptake by insulin-dependent tissues (skeletal muscle, adipose, liver)
Counterregulatory Responses (in order of activation):
| Glucose Level | Response |
|---|---|
| ~70 mg/dL | Insulin secretion falls |
| ~65 mg/dL | Glucagon release (from alpha cells) - stimulates hepatic glycogenolysis/gluconeogenesis |
| ~60 mg/dL | Epinephrine release - adrenergic symptoms begin |
| ~55 mg/dL | Cortisol and growth hormone released |
| <50 mg/dL | Neuroglycopenic symptoms appear |
Classification & Causes
1. Diabetic / Iatrogenic (most common overall)
| Agent | Risk |
|---|---|
| Insulin | Highest risk; accounts for ~2-6% of deaths in T1DM |
| Sulfonylureas (e.g. glibenclamide) | High risk; prolonged severe hypoglycaemia due to long duration of action |
| Meglitinides (repaglinide) | Moderate risk |
| Metformin, TZDs, DPP-4i, GLP-1 RAs, SGLT-2i | Low risk as monotherapy; risk increases if combined with insulin/sulfonylurea |
Risk factors for iatrogenic hypoglycaemia (Goldman-Cecil, Table 210-8):
Medical: Strict glycaemic control, previous severe hypoglycaemia, long T1DM duration, lipohypertrophy at injection sites, impaired hypoglycaemia awareness, hepatic/renal dysfunction, sepsis, cognitive dysfunction, C-peptide negativity
Lifestyle: Increased exercise, alcohol, skipped meals, early pregnancy, breastfeeding, poor diet
2. Non-Diabetic Fasting Hypoglycaemia
| Category | Examples |
|---|---|
| Hormone deficiencies | Hypopituitarism, adrenal insufficiency (cortisol/ACTH deficiency), growth hormone deficiency, hypothyroidism |
| Insulinoma | Pancreatic beta-cell tumour - most common endogenous cause of fasting hypoglycaemia |
| Non-islet cell tumours | Large retroperitoneal sarcomas, hepatocellular carcinoma - via IGF-II overexpression activating insulin receptor |
| Critical illness | Hepatic failure (impaired gluconeogenesis/glycogenolysis), renal failure, sepsis, CCF |
| Enzyme defects | Glucose-6-phosphatase deficiency (glycogen storage disorders), gluconeogenic enzyme defects |
| Substrate deficiency | Malnutrition, end-stage cachexia |
| Drugs | Alcohol (inhibits gluconeogenesis), quinine, pentamidine, salicylates |
| Factitious | Exogenous insulin/sulfonylurea administration |
3. Non-Diabetic Postprandial (Reactive) Hypoglycaemia
- Alimentary hyperinsulinism - most common cause; follows gastric surgery (gastrectomy, pyloroplasty, gastrojejunostomy, vagotomy) - rapid glucose absorption triggers excessive insulin surge
- Reactive hypoglycaemia - also seen with late dumping syndrome; carbohydrate load raises glucose, triggers insulin overshoot
Pathophysiology: Why Diabetics Are at Extra Risk
In T1DM, counterregulatory defences become progressively defective:
- Glucagon response to hypoglycaemia fails - within a few years of onset
- Epinephrine release becomes blunted - develops over time
- Result: Hypoglycaemia Unawareness - patients lose warning adrenergic symptoms; even a single hypoglycaemic episode can blunt subsequent counterregulatory responses
Somogyi phenomenon (clinically important exam topic):
- Nocturnal insulin excess → unrecognised overnight hypoglycaemia → counterregulatory hormone surge → rebound morning hyperglycaemia
- Trap: physician misinterprets morning hyperglycaemia as poor control and increases insulin, worsening the cycle
- Correct management: reduce the evening/overnight insulin dose
Clinical Features
Symptoms arise from two mechanisms:
A. Adrenergic / Autonomic (early - counterregulatory response to falling glucose)
- Sweating, tremor, palpitations, tachycardia
- Anxiety, hunger, pallor
- Nausea
B. Neuroglycopenic (later - CNS glucose deprivation)
- Difficulty concentrating, confusion, slurred speech
- Bizarre behaviour, aggression
- Visual disturbances
- Focal neurological signs
- Seizures
- Coma
Exam point: In hypoglycaemia unawareness, the adrenergic prodrome is absent - patient goes directly from normal to neuroglycopenic/comatose. This is most dangerous.
Diagnosis
Bedside
- Point-of-care (POC) fingerstick glucose - rapid initial test; guides immediate management
- Confirm with formal lab plasma glucose if feasible before treatment
Laboratory Workup (to identify the cause)
| Test | Purpose |
|---|---|
| Plasma glucose (formal lab) | Confirm hypoglycaemia |
| Insulin level | Elevated in insulinoma, exogenous insulin, sulfonylurea |
| C-peptide | Low with exogenous insulin (manufactured insulin lacks C-peptide); elevated with insulinoma/sulfonylurea |
| Insulin antibodies | If factitious exogenous insulin use suspected |
| Sulfonylurea screen | Detects surreptitious sulfonylurea ingestion |
| Cortisol, ACTH, GH | Rule out hormonal deficiencies |
| Liver function tests | Hepatic cause |
| Renal function | Impaired clearance of insulin/drugs |
| Ethanol level | Alcohol-induced hypoglycaemia |
| Blood cultures | Sepsis |
Factitious hypoglycaemia:
- Exogenous insulin use: high insulin + low C-peptide
- Sulfonylurea use: high insulin + high C-peptide (drug stimulates endogenous insulin)
- Insulinoma: high insulin + high C-peptide (must distinguish from sulfonylurea by drug screen)
Management
Mild-Moderate (alert patient)
- Oral glucose: 15-20g of fast-acting carbohydrate (glucose tablets, juice, sugary drink)
- "15-15 rule": 15g carbs, recheck in 15 minutes, repeat if needed
- Follow with a longer-acting snack to prevent recurrence
Severe (impaired consciousness or unable to swallow)
| Route | Agent | Dose |
|---|---|---|
| IV | Dextrose 50% (D50W) | 1-3 ampoules (50 mL each) IV |
| IV (children <8 yrs) | D25W or D10W | 0.5-1 g/kg; use D25W diluted 1:1 from D50W |
| IV (alternative, D50W shortage) | D10W | Boluses up to 250 mL |
| IM/SC | Glucagon | 1-2 mg IM or SC |
| Intranasal | Glucagon | Available as alternative (less widely used) |
Important notes:
- If alcohol use disorder suspected: give thiamine before or with glucose (to prevent precipitating Wernicke's encephalopathy)
- Glucagon is ineffective in alcohol-induced hypoglycaemia (absent hepatic glycogen stores)
- Glucagon onset: 10-20 minutes; peak 30-60 minutes; can repeat as needed
Sulfonylurea-Induced Hypoglycaemia - Special Considerations
- Hypoglycaemia is prolonged and severe due to long drug half-life
- Observe for 24 hours after any hypoglycaemic episode from sulfonylurea
- Children and patients with renal failure: hypoglycaemia may be delayed up to 18 hours after a single pill ingestion
- Octreotide (somatostatin analogue) can be used to suppress further insulin release
Specific Scenarios (High-Yield Exam Topics)
| Scenario | Key Points |
|---|---|
| Insulinoma | Fasting hypoglycaemia, high insulin, high C-peptide, no sulfonylurea on drug screen; 72-hour fast provocation test; treat surgically |
| Adrenal insufficiency | Hypoglycaemia + hyponatraemia + hyperkalaemia; treat with hydrocortisone |
| Non-islet cell tumour hypoglycaemia | Large sarcoma/HCC; mediated by IGF-II; treat with frequent small meals; difficult to control without treating primary tumour |
| Neonatal hypoglycaemia | "Small for dates" (SGA) babies at highest risk; can cause irreversible brain damage; risk much greater in children than adults |
| T1DM + hypoglycaemia unawareness | Hypoglycaemia awareness restoration therapy (HART); relax glycaemic targets; continuous glucose monitoring (CGM) |
| Alcohol-induced | Inhibits gluconeogenesis; glucagon ineffective; give IV dextrose + thiamine |
| Post-gastric surgery | Reactive/alimentary; managed with small frequent low-carbohydrate meals |
Complications of Untreated Hypoglycaemia
- Seizures
- Permanent brain injury (especially in neonates/children)
- Death (accounts for ~2-6% of deaths in T1DM)
- Older patients may take several days to fully recover neurologically even after glucose normalisation
Summary Table: Quick Exam Reference
| Feature | Details |
|---|---|
| Definition | Whipple's triad; symptomatic typically <50 mg/dL |
| Most common cause overall | Insulin therapy (iatrogenic) |
| Most common non-diabetic cause | Insulinoma |
| First counterregulatory hormone lost in T1DM | Glucagon (then epinephrine) |
| Somogyi effect | Nocturnal hypoglycaemia → rebound morning hyperglycaemia |
| Factitious insulin use marker | High insulin, LOW C-peptide |
| Glucagon ineffective when | Alcohol use / absent glycogen stores |
| IV dextrose in children | D25W or D10W (NOT D50W) |
| Sulfonylurea observation period | 24 hours |
| Must give with glucose in alcoholics | Thiamine (prevent Wernicke's) |
Sources: Goldman-Cecil Medicine 26th Ed., Chap. 210-211; Rosen's Emergency Medicine 9th Ed., Chap. Hypoglycemia
This is a shared conversation. Sign in to Orris to start your own chat.