Should bicarbonate be given in HHS if levels are 18
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hyperosmolar hyperglycemic state bicarbonate treatment
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Here is the direct answer:
Bicarbonate in HHS with Bicarb of 18 mEq/L
No — bicarbonate is not indicated in HHS when the serum bicarbonate is 18 mEq/L.
Why not?
A bicarbonate of 18 mEq/L is actually an expected, diagnostic finding in "pure" HHS. The textbooks are explicit:
"In the hyperosmolar hyperglycemic state in the absence of concurrent acid-base disturbances, the arterial pH rarely drops below 7.30, and serum bicarbonate levels typically do not fall below 18 mmol/L." — Goldman-Cecil Medicine
This means a bicarb of 18 is at the lower boundary of normal for HHS itself — not a sign of significant acidosis requiring intervention.
When IS bicarbonate considered (in DKA, not HHS)?
Even in DKA, the ADA has historically only considered bicarb if pH < 7.0. Per Tintinalli's:
"Sodium bicarbonate has been included in ADA guidelines if serum pH is <7.0; however, more recent data suggest no benefit and potential harms even then (particularly in the pediatric population)." — Tintinalli's Emergency Medicine
Key clinical point
A bicarb of 18 in someone presenting with HHS should actually prompt you to ask: does this patient have a concurrent mixed picture (HHS + DKA)? Bicarbonate levels significantly below 18, or a pH below 7.3, would suggest a mixed disorder — and even then, the indication for IV bicarbonate administration remains controversial and is generally not recommended unless pH is <7.0.
Bottom line: Bicarb 18 in HHS = no bicarbonate replacement needed. Focus on aggressive IV fluid resuscitation (the cornerstone of HHS treatment), electrolyte correction, and identifying the precipitating cause.
Ph is 7.31
Based on what's already in context from the previous search, I can answer this directly.
pH 7.31 + Bicarb 18 in HHS — Still No Bicarbonate
Bicarbonate is still not indicated. Here's why:
The threshold matters
The only scenario where bicarbonate has even been considered (and remains controversial) is pH < 7.0. A pH of 7.31 is well above that threshold.
Context for this pH in HHS
Per Goldman-Cecil: pH rarely drops below 7.30 in pure HHS. So a pH of 7.31 is essentially at the expected lower limit for this condition — it is not a pathological acidosis requiring correction.
What this picture tells you clinically
- pH 7.31 + bicarb 18 = mild acidosis, consistent with pure HHS
- If you see these values, no concurrent severe ketoacidosis is present
- The acidosis will self-correct with fluid resuscitation and insulin — the treatment of the underlying HHS
What to do instead
| Priority | Action |
|---|---|
| 1st | Aggressive IV fluid resuscitation (NS 15–20 mL/kg/h first hour) |
| 2nd | Identify & treat precipitating cause |
| 3rd | Electrolyte correction (especially K⁺) |
| 4th | Insulin — only after initial fluids |
Giving bicarbonate at pH 7.31 carries risk with no proven benefit: potential paradoxical CNS acidosis, hypokalemia, and worsening osmolality — all particularly dangerous in HHS.
How to calculate serum osmalality
This was covered directly in the Tintinalli's content already retrieved — no new search needed.
Serum Osmolality Calculation
Two formulas:
Calculated (Total) Osmolality:
$$\text{Osmolality} = 2[\text{Na}^+] + \frac{\text{Glucose}}{18} + \frac{\text{BUN}}{2.8}$$
Effective Osmolality (excludes BUN):
$$\text{Effective Osmolality} = 2[\text{Na}^+] + \frac{\text{Glucose}}{18}$$
Why two formulas?
BUN is osmotically inactive — it crosses cell membranes freely and does not drive fluid shifts. So the effective osmolality better reflects the true osmotic pressure causing cellular dehydration.
However, Tintinalli's notes that UK guidelines favour including BUN because elevated urea reflects dehydration severity and may help prevent overly rapid osmolality correction (which risks cerebral oedema and osmotic demyelination syndrome).
Units
- Na⁺ in mEq/L
- Glucose in mg/dL ÷ 18 (or if in mmol/L, use directly)
- BUN in mg/dL ÷ 2.8 (or if in mmol/L, use directly)
Reference ranges (relevant to HHS)
| Value | Significance |
|---|---|
| 275–295 mOsm/kg | Normal |
| >300 mOsm/kg | Significant hyperosmolality |
| >315 mOsm/kg | HHS diagnostic threshold; cognitive changes common |
| Correction rate | Do not exceed 3 mOsm/kg/h |
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