Pimp Questions
โ What is the key pathophysiologic difference between HHS and DKA?
In HHS, patients have enough circulating insulin to prevent lipolysis and ketogenesis, but not enough for peripheral glucose uptake. So they develop extreme hyperglycemia without significant ketoacidosis. In DKA, there is absolute insulin deficiency โ uninhibited lipolysis โ ketone body production โ metabolic acidosis. This is why HHS is nearly exclusive to Type 2 DM (some residual insulin production).
โ Why are fluids more important than insulin in HHS?
HHS patients have an average 8-10L fluid deficit (vs 3-5L in DKA). Aggressive IV fluids alone will drop glucose by 75-100 mg/dL per hour through dilution + improved renal perfusion โ glycosuria. Starting insulin before adequate hydration risks cardiovascular collapse (glucose drops โ water moves intracellularly โ further intravascular depletion) and cerebral edema (too-rapid osmolality correction).
โ How do you calculate corrected sodium in hyperglycemia?
Corrected Na = measured Na + 1.6 ร [(glucose โ 100) / 100]. Hyperglycemia causes osmotic water shift from ICF to ECF โ dilutional hyponatremia. The corrected Na tells you the true sodium status. If corrected Na is elevated โ the patient is even more hyperosmolar and dehydrated than the measured Na suggests. Use corrected Na to guide IVF choice (0.9% vs 0.45% NS).
โ Why is mortality in HHS so much higher than DKA?
HHS mortality is 5-20% (vs 1-5% for DKA) because: (1) patients are older with more comorbidities, (2) the trigger is often a serious acute illness (MI, stroke, sepsis), (3) degree of dehydration is much more severe (8-10L), (4) hyperosmolality itself causes end-organ damage, (5) HHS is a hypercoagulable state โ arterial and venous thrombosis.
โ What is the risk of correcting osmolality too quickly?
Cerebral edema. The brain adapts to chronic hyperosmolality by generating idiogenic osmoles (intracellular solutes). Rapid correction of serum osmolality causes water to shift into brain cells โ edema. Target osmolality decline โค 3 mOsm/kg/hr. This is analogous to osmotic demyelination in too-rapid sodium correction.
โ When do you transition from IV insulin drip to subcutaneous insulin?
When the patient meets ALL of: (1) glucose < 300, (2) osmolality < 315, (3) alert and eating. Give basal insulin (glargine 0.2-0.3 U/kg) 2-4 hours BEFORE stopping the drip -the drip has a half-life of only 5-10 minutes, so any gap in coverage โ rebound hyperglycemia.
Clinical Examples
๐ Case 1, Nursing Home HHS with UTI Trigger
Patient: 82F, T2DM on metformin + glipizide, dementia, HTN. Brought from SNF with 4 days of progressive lethargy, decreased PO intake, and new urinary incontinence.
Key findings: T 100.8°F, HR 108, BP 88/52. Glucose 1,040, Na 152 (corrected 167), K 4.6, Cr 3.2 (baseline 1.0), serum osm 398, pH 7.32, bicarb 22, BHB 0.6. UA: pyuria + bacteria.
Management:
- NS 1.5 L/hr x 2 hours, then 500 mL/hr; switch to 0.45% NS when corrected Na begins to normalize
- Insulin 0.1 U/kg/hr IV (NO bolus) started after first liter of fluids and K confirmed ≥ 3.3
- Ceftriaxone 1g IV for UTI (trigger treatment)
- DVT prophylaxis with enoxaparin (HHS is a hypercoagulable state)
- Target glucose drop 50-70 mg/dL/hr; target osm correction ≤ 3 mOsm/kg/hr
Teaching point: Fluids alone drop glucose 75-100 mg/dL/hr. The corrected sodium reveals the true degree of dehydration. Always identify and treat the trigger.
๐ Case 2, HHS/DKA Overlap Syndrome
Patient: 55M, T2DM on insulin (non-adherent x 2 weeks), obesity, CKD stage 3. Presents with confusion, vomiting, and polyuria.
Key findings: HR 118, BP 96/60. Glucose 890, Na 131 (corrected 144), K 5.8, Cr 4.1 (baseline 1.8), pH 7.18, bicarb 10, AG 28, BHB 5.2, serum osm 342.
Management:
- HHS/DKA overlap, meets criteria for both (glucose > 600, osm > 320, AND AG acidosis + elevated ketones)
- Aggressive NS resuscitation 1 L/hr; K 5.8 so safe to start insulin immediately
- Insulin drip 0.1 U/kg/hr (treat ketoacidosis like DKA, close the gap)
- When glucose reaches 300: switch to D5 0.45% NS + reduce insulin to 0.02-0.05 U/kg/hr
- Monitor K q2h, will drop rapidly with insulin and fluids
Teaching point: Up to 30% of hyperglycemic emergencies have overlap features. Treat the ketoacidosis like DKA (close the anion gap) while managing hyperosmolarity like HHS (gradual osm correction). The K of 5.8 is falsely reassuring, total body K is depleted. ADA Consensus, Kitabchi 2009
๐ Case 3, HHS Complicated by Cerebral Edema
Patient: 70F, T2DM on sulfonylurea, found confused at home for 2+ days. Started on aggressive IV fluids and insulin at outside hospital before transfer.
Key findings: Glucose dropped from 1,100 to 450 in 4 hours. Osm corrected from 410 to 340 (17.5 mOsm/hr). Patient now obtunded with new fixed dilated left pupil.
Management:
- Stat CT head, cerebral edema confirmed
- Mannitol 1 g/kg IV bolus or hypertonic saline 3% 250 mL
- Elevate head of bed to 30 degrees
- STOP hypotonic fluids; switch to NS to prevent further osmolality drop
- Neurosurgery consult for possible EVD placement
Teaching point: Cerebral edema from overly aggressive correction is the most feared HHS complication. The brain generates idiogenic osmoles to adapt to chronic hyperosmolality. Target osm decline ≤ 3 mOsm/kg/hr and glucose decline 50-70 mg/dL/hr. This patient's osm dropped at nearly 6x the safe rate.
Sample Presentation
Mrs. Williams is an 78-year-old woman with T2DM, dementia, and HTN, brought from nursing home with 3 days of altered mental status, decreased PO intake, and new incontinence. VS: T 100.4ยฐF, HR 112, BP 92/58, RR 20. Exam: dry mucous membranes, tenting, somnolent but arousable. Labs: glucose 923, Na 149 (corrected 163), K 4.8, Cr 2.8 (baseline 1.1), pH 7.34, bicarb 20, BHB 0.8, serum osm 384. UA: pyuria. CXR: clear.
Key Points: Classic HHS -glucose > 600, osm > 320, no significant ketoacidosis. Trigger: UTI (pyuria + fever). Start NS 1.5L/hr. Kโบ is adequate โ can start insulin at 0.1 U/kg/hr after first 1-2L fluids. Treat UTI empirically. DVT prophylaxis. ICU for monitoring. This patient has ~10L fluid deficit.
- Fingerstick glucose q1h -target decline 50-70 mg/dL per hour. Faster correction risks cerebral edema.
- BMP q2-4h -Kโบ (shifts dramatically with insulin), Naโบ (corrected Na should rise as glucose falls -if not, you're giving too much free water), Cr (improving = adequate hydration)
- Serum osmolality q2-4h -target decline โค 3 mOsm/kg/hr. If dropping faster โ slow IVF rate.
- Urine output q1h -target โฅ 0.5 mL/kg/hr (sign of adequate resuscitation). Foley catheter in ICU.
- Mental status -should improve as osmolality normalizes. If AMS worsens despite improving labs โ CT head (stroke may have been the trigger).
- Fluid balance (I&Os) -track meticulously. Goal: replace deficit over 24-48h.
- Resolution criteria: glucose < 300, osmolality < 315, patient alert/eating โ transition to SQ insulin. ADA/AACE Consensus, 2009
Monitoring