Lesson
Relative Insulin Deficiency and Hyperosmolality
HHS develops when insulin activity limits major ketogenesis but cannot control hepatic glucose output or peripheral glucose use, allowing profound osmotic diuresis and water loss.
- Relative insulin deficiency
- Hyperglycemia
- Osmotic diuresis
- Water deficit
- Neurologic dysfunction
Increase hepatic glucose without major ketogenesis
Lose water and electrolytes through glucosuria
Impair kidney perfusion and cognitive function
Separate HHS from DKA physiology
Residual insulin activity is often enough to suppress extensive lipolysis and ketogenesis but not enough to control glucose. Severe hyperglycemia therefore develops without the degree of ketoacidosis expected in DKA.
Follow the water deficit
Glucosuria drives osmotic diuresis and large losses of water, sodium, potassium, and other electrolytes. Limited thirst response, impaired access to water, acute illness, functional dependence, or cognitive impairment can prevent replacement.
Connect tonicity to the brain
Hyperosmolality draws water from cells and contributes to weakness, lethargy, focal findings, seizures, and coma. Cognitive impairment is clinically important but is not required as a separate diagnostic criterion when all four biochemical criteria are established.
Quick check
Lesson
Four-Part Diagnosis and Osmolality
Current diagnosis requires severe hyperglycemia, hyperosmolality, absence of significant ketonemia, and absence of metabolic acidosis, with all four criteria present.
- Glucose at least 600
- Effective osmolality
- Total osmolality
- Minimal ketones
- No acidosis
At least 600 mg/dL
Effective above 300 or total above 320
Beta-hydroxybutyrate below 3, pH at least 7.3
Apply all four criteria
HHS requires plasma glucose at least 600 mg/dL, effective osmolality above 300 mOsm/kg or total osmolality above 320 mOsm/kg, beta-hydroxybutyrate below 3.0 mmol/L or urine ketones below 2+, and pH at least 7.3 with bicarbonate at least 15 mmol/L.
Calculate effective and total osmolality
With values in mmol/L, effective osmolality equals two times sodium plus glucose. Total osmolality adds urea. With conventional units, effective osmolality is two times sodium plus glucose divided by 18, while total osmolality also adds BUN divided by 2.8.
Interpret the number in context
Effective osmolality excludes urea because urea crosses cell membranes and contributes less to sustained tonicity. Measured osmolality, an osmolar gap, renal failure, alcohols, and other solutes can complicate interpretation.
Quick check
Lesson
Precipitating Causes and Mixed Crisis
HHS is commonly precipitated by infection, vascular events, medications, insulin insufficiency, impaired water access, or a combination, and more than one-third of crises can show DKA and HHS overlap.
- Infection
- Stroke and ischemia
- Medication effects
- Water access
- Mixed DKA and HHS
Infection, ischemia, stroke, trauma, or surgery
Function, cognition, cost, caregiving, or medication
Significant ketones or acidosis change insulin intensity
Find acute illness
Infection, myocardial infarction, stroke, pancreatitis, surgery, trauma, and other stressors raise counterregulatory hormones and can reduce intake. Evaluation should follow symptoms, examination, risk, and initial data.
Find treatment and access failures
New diabetes, insufficient insulin, glucocorticoids, sympathomimetics, atypical antipsychotics, thiazide-like diuretics, enteral or parenteral nutrition, and limited access to water or diabetes care can contribute.
Recognize mixed DKA and HHS
Significant ketonemia at least 3.0 mmol/L or metabolic acidosis indicates mixed DKA and HHS rather than pure HHS. Mixed crisis uses the higher 0.1 units/kg/h DKA insulin intensity after potassium safety is established.
Quick check
Lesson
Initial Assessment and Fluid Resuscitation
Fluid therapy restores perfusion and begins lowering glucose and osmolality before insulin has its full role.
- Hemodynamics
- Isotonic crystalloid
- Balanced crystalloid
- Fluid deficit
- Limited reserve
Cognition, perfusion, output, heart, and kidney reserve
Begin 500 to 1,000 mL/h when reserve permits
Use smaller increments and frequent reassessment
Stabilize and measure
Assess airway, breathing, circulation, cognition, temperature, volume status, glucose, electrolytes, creatinine, osmolality, ketones, venous pH, bicarbonate, ECG, intake, output, and the likely precipitant.
Restore circulating volume
Adults without cardiac or kidney compromise commonly begin isotonic saline or balanced crystalloid at 500 to 1,000 mL/h for the first 2 to 4 hours. Subsequent rates reflect response and aim to correct the deficit over 24 to 48 hours.
Protect limited reserve
Older adults and people with heart failure or end-stage kidney disease may require 250 mL increments and frequent hemodynamic reassessment. A fixed large-volume pathway can cause pulmonary edema and mechanical ventilation.
Quick check
Lesson
Sodium, Osmolality, and Controlled Correction
HHS treatment must lower tonicity gradually enough to avoid neurologic injury while still restoring volume and kidney perfusion.
- Glucose decline
- Sodium decline
- Osmolality decline
- Corrected sodium
- Hypotonic fluid threshold
Avoid rapid intracellular water shifts
Trend sodium and glucose together
Do not react to the expected early rise alone
Control the treatment slopes
Glucose decline should not exceed 90 to 120 mg/dL/h, sodium decline should not exceed 10 mmol/L in 24 hours, and osmolality should fall about 3 to 8 mOsm/kg/h.
Expect an early sodium rise
A glucose fall of 100 mg/dL can raise sodium about 1.6 mmol/L as water returns intracellularly. That expected rise does not by itself indicate failure or require hypotonic fluid.
Reserve hypotonic saline
Initial 0.45 percent saline is avoided. It is considered only when osmolality is not declining despite adequate positive fluid balance and appropriate insulin treatment, with the complete sodium and volume context reviewed.
Quick check
Lesson
Potassium, Insulin, and Dextrose
Potassium safety and adequate fluid replacement precede low-dose insulin, while dextrose later prevents hypoglycemia and overly rapid osmotic correction.
- Potassium threshold
- Fluid-first strategy
- 0.05 units/kg/h
- Mixed crisis dose
- Dextrose below 250
Replace first when lower
Use for pure HHS after initial fluid replacement
Use when significant DKA features coexist
Gate insulin with potassium
If potassium is below 3.5 mmol/L, replace potassium and delay insulin until it exceeds 3.5. When potassium is 3.5 to 5.0 and kidney function and urine output permit, replacement is commonly added to maintain 4 to 5 mmol/L.
Use the correct insulin intensity
Pure HHS without acidosis and with absent or mild ketonemia uses fixed-rate IV insulin at 0.05 units/kg/h after adequate fluid and potassium replacement. Mixed DKA and HHS uses 0.1 units/kg/h.
Add dextrose while osmolality resolves
When glucose falls below 250 mg/dL, add 5 to 10 percent dextrose and adjust insulin to prevent hypoglycemia while continuing controlled correction until HHS resolution criteria are met.
Quick check
Lesson
Monitoring and Resolution
HHS resolution requires recovery of osmolality, glucose, urine output, and cognition rather than a glucose threshold alone.
- Hourly glucose
- Four-hour chemistry
- Osmolality trend
- Urine output
- Cognitive recovery
Glucose, electrolytes, creatinine, and osmolality
Glucose below 250 and output above 0.5 mL/kg/h
Investigate persistent or new neurologic findings
Monitor a coupled system
Check glucose every 1 to 2 hours and electrolytes, creatinine, and osmolality about every 4 hours during active treatment. Potassium is rechecked early after insulin and repeatedly thereafter. Track hemodynamics, cognition, intake, output, and cumulative fluids.
Confirm all resolution domains
HHS is considered resolved when measured or calculated osmolality is below 300 mOsm/kg, glucose is below 250 mg/dL, urine output exceeds 0.5 mL/kg/h, and cognitive status has improved.
Do not substitute one marker
A glucose below 250 does not prove that hyperosmolality, hypoperfusion, or neurologic dysfunction has resolved. Conversely, persistent altered cognition after osmolality correction requires evaluation for stroke, infection, seizure, medication effects, or another cause.
Quick check
Lesson
Complications and Special Populations
Treatment can cause hypoglycemia, hypokalemia, fluid overload, cerebral edema, osmotic demyelination, thrombosis, and worsening kidney injury if correction is too rapid or poorly monitored.
- Neurologic injury
- Thrombosis
- Acute kidney injury
- Fluid overload
- Hypoglycemia and hypokalemia
Avoid rapid glucose, sodium, and osmolality change
Restore perfusion and assess prophylaxis
Adjust treatment to heart, kidney, age, and pregnancy
Prevent rapid osmotic injury
Cerebral edema is rare in adults but can follow rapid osmotic change. Osmotic demyelination can occur when hypernatremia and hyperosmolality correct too quickly. New neurologic deterioration requires urgent evaluation.
Address perfusion and thrombosis
Severe dehydration produces hemoconcentration and thrombotic risk, while acute kidney injury is common and often improves with rehydration. Thromboprophylaxis follows the clinical setting, mobility, bleeding risk, and institutional protocol.
Protect special populations
Frail older adults, pregnancy, heart failure, dialysis, and severe infection require individualized fluids, monitoring, and level of care. Children use pediatric protocols rather than adult HHS algorithms.
Quick check
Lesson
Transition, Discharge, and Prevention
Resolution must lead to a safe insulin transition, medication and precipitant review, water and care access, education, supplies, and timely follow-up.
- Basal overlap
- Precipitant correction
- Water access
- Medication review
- Follow-up
Activate basal coverage before IV insulin stops
Treat illness and medication or access failures
Provide supplies, support, instructions, and rapid review
Transition without an insulin gap
Select subcutaneous therapy from prior treatment, inpatient requirements, nutrition, kidney function, hypoglycemia risk, and the reason for HHS. Give basal insulin with protocol-defined overlap before stopping IV insulin when ongoing insulin is required.
Correct the system that failed
Treat infection or vascular disease, reassess hyperglycemia-promoting medicines, confirm insulin and device technique, and evaluate whether thirst, mobility, cognition, caregiving, food, housing, cost, or transportation limited care.
Create a usable prevention plan
Provide written glucose, medication, hydration, sick-day, emergency, and contact instructions. Ensure medicines, monitoring supplies, water access, caregiver support when needed, and early outpatient follow-up are available before discharge.
Quick check
Module test
Check the connections.
Each attempt draws 10 questions from the complete 100 question bank.
Each attempt draws a fresh set and rearranges the answer choices.
References
Current clinical foundation.
Lecture material was synthesized with the following contemporary guidance. Verify local policy and current guidance before applying clinical information.