Hyperosmolar Hyperglycaemic State (HHS)

HHS is a hyperglycaemic emergency in type 2 diabetes characterised by glucose >30 mmol/L, osmolality >320 mOsm/kg, profound dehydration (average 8–10 litres), and minimal ketosis. Unlike DKA, correction must be slow (over 48 hours) to prevent…

JBDS HHS Guideline 2012 (updated 2023)

The pathway

1 · Diagnosis and initial assessment

Glucose >30 mmol/L (often 40–60)
Osmolality >320 mOsm/kg: calculate as 2(Na + K) + urea + glucose
Ketones: typically <3 mmol/L blood ketones (vs DKA where >3)
pH >7.3, bicarbonate >15 (vs DKA which is acidotic)
ABG, U&E, FBC, blood cultures, urine culture
ECG: look for hypokalaemia or precipitating ACS

2 · IV fluid resuscitation — slow and careful

0.9% NaCl is first-line (NOT 0.45% NaCl initially)
1 litre over 1 hour if haemodynamically compromised
Then 0.9% NaCl 500ml/hr for next 4 hours
Target: osmolality fall of 3–8 mOsm/kg/hour — NO faster
Do NOT correct glucose faster than 5 mmol/L/hour
Switch to 0.45% NaCl only if osmolality not falling despite adequate 0.9% NaCl
Do NOT use rapid large-volume resuscitation — risk of cerebral oedema

3 · Insulin — timing matters

Do NOT start insulin in first hour — fluids alone will lower glucose
Insulin indicated only if:
Blood ketones >1 mmol/L, OR
Rate of glucose fall <5 mmol/L/hour after 1h of fluids
Fixed-rate insulin infusion (FRII): 0.05 units/kg/hr (NOT the 0.1 units/kg/hr used in DKA)
Target glucose fall: 5 mmol/L/hour — no faster
Add 5% glucose when glucose <14 mmol/L to allow continued insulin

4 · Potassium replacement

Check K⁺ before starting insulin
K⁺ >5.5: no replacement
K⁺ 3.5–5.5: 40 mmol/L in IV fluid
K⁺ <3.5: urgent replacement before insulin — senior review
Recheck K⁺ hourly while on insulin infusion

5 · VTE prophylaxis — critical

Enoxaparin 40mg SC (prophylactic) on admission unless contraindicated
HHS carries very high thrombosis risk (hyperviscosity from dehydration)
If haematocrit markedly elevated → consider therapeutic dose LMWH after senior review
Continue throughout admission

6 · Treat the precipitant

Infection (most common): blood/urine cultures → antibiotics per local guidelines
ACS: 12-lead ECG, troponin, cardiology input
Stroke: FAST assessment, CT head
Medications: review for culprit drugs (steroids, thiazides, antipsychotics)
New T2DM: HHS may be the presenting event — diabetes team referral

7 · Monitoring frequency

Glucose and ketones: hourly
Osmolality: hourly for the first 6 hours, then 2-hourly for the next 6 (JBDS)
Urine output: catheterise — target >0.5 ml/kg/hr
Neurological obs: hourly — deterioration = cerebral oedema, call senior
Target at 24h: osmolality <315, glucose 14–20 mmol/L
Target at 48h: glucose 10–14 mmol/L, osmolality normal

Drugs

Drug	Dose	Route	Notes
0.9% Sodium Chloride	500ml/hr initially	IV	First-line fluid. Do NOT use 0.45% NaCl initially. Slow correction over 48 hours. Target osmolality fall 3–8 mOsm/kg/hr.
Insulin (Actrapid)	0.05 units/kg/hr	IV infusion	Not in first hour. Start only if ketones >1 or glucose not falling. Half the DKA rate. Avoid dropping glucose >5 mmol/L/hr.
Potassium chloride	40 mmol/L in IV fluid	IV	If K⁺ 3.5–5.5 mmol/L before/during insulin. Check hourly on insulin infusion.
Enoxaparin	40mg OD SC (prophylactic)	SC	Start on admission. Very high VTE risk. May need therapeutic dose if haematocrit very elevated — senior review.

When to escalate

Osmolality >350 mOsm/kg (JBDS marker of severity) — HDU/level 2 and immediate senior review; also Na >160, pH <7.1, GCS <12, SBP <90, urine output <0.5ml/kg/hr,Neurological deterioration during treatment — cerebral oedema; stop insulin, reduce fluid rate, mannitol 0.5–1g/kg IV, CT head,K+ <3.0 mmol/L — hold insulin, urgent potassium replacement, senior review,Haemodynamic instability despite fluids — vasopressors, ITU referral,Concurrent ACS identified on ECG — dual pathway activation: HHS + ACS management,No improvement in osmolality at 4 hours — reassess fluid strategy, consider 0.45% NaCl, endocrinology review

Reference: JBDS HHS Guideline 2012 / NHS Diabetes Inpatient Guideline 2023

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