Significant numbers / equations to memorise Flashcards
Normal ratio of CSF glucose to blood glucose
0.6
CSF protein normal range
<0.45 g/L
Light’s criteria
Pleural fluid is exudate if any of the following satisfies:
1. Pleural TP > Serum TP ⨉ 0.5
2. Pleural LDH > Serum LDH ⨉ 0.6
3. Pleural LDH > 2/3 ULN of serum LDH
SAAG (serum-ascites albumin gradient) limit
> 11 g/L: transudate
<11 g/L: exudate
Calculated osmolality
= 2 [Na+] + [urea] + [glucose]
Polyuria criteria
> = 3L /day urination in adults
Fluid deprivation test: time, urgency, walkthrough
Time: 8 hours
Stop when: body weight ↓ 3% / Na > 150 / altered mental status
Walkthrough:
- UOsm > 600: normal
- UOsm 300~600:
- DDAVP increase >50%: partial cranial DI
- DDAVP increase <50%:
- plasma osm normal: primary polydipsia
- plasma osm > 300: partial nephrogenic DI
- UOsm < 300: complete DI
- DDAVP increase >50%: complete cranial DI
- DDAVP increase <50%: complete nephrogenic DI
Na+ normal range
135~145 mmol/L
Na+ correction precautions
must be <12mmol/L (~6) in 24hr
Osmolarity normal range
280~295
Corrected serum Na
= measured Na + 2.4 ⨉ (plasma glucose - 5.5) / 5.5
≈ measured Na + plasma glucose / 2 (when it’s high)
normal U[Na] or U[K] under non-renal Na loss
<20
Fluid restriction limit
<1 L/ day
Lethal dose in salt toxicity
> 4 tablespoon in adult
K+ normal range
3.5~5.1 mmol/L
