Anticonvulsants

Question 1

LITHIUM- acute

Answer 1

R
Usual.

R
- >25g = GI
- Kids: accidental is benign

S
- ANTICIPATE:
–> GI symptoms only
–> Delayed neurotox possible if impaired excretion.

-SUPPORT:
–> Support urinary excretion with fluids and Na repletion

I
- 12 lead, BGL, parac (delib)
- UEC –> Na and eGFR
- Lithium level

D
- No

E
- Not indicated

A
- No

D
- OBSERVE:
–> 4 hours (standard), 12 hours (SR)

-HOME WHEN:
–> Lithium level <2.5 and falling

BG CHRONIC USE DOESN’T CHANGE APPROACH

Question 2

LITHIUM- Chronic

Answer 2

R
- Usual

R
- Any patient on lithium with neurological Sx. Intercurrent AKI.
- Dose and levels don’t help predict course
- If signif obtunded, or seizure –> BAD. Risk permanent neurol.

S
-ANTICIPATE:
–> Mild: Tremor, hyperreflex, agitation, ataxia.
–> Mod: Stupor, rigidity, hypoTN
–> Sev: Coma, seizure, clonus.
- As chronic med, Diabetes insipidus
—> hyperNa

-SUPPORT:
- Usual
–> - Support urinary excretion with hydration. 5% dextrose if DI/hyperNa. Target UO >1ml/kg/hr

I
- 12-lead, BGL, parac (delib)
- Lithium level (to CONFIRM and TRACK only. Poor correlation).
- Causes: UEC, thyroid
- AKI will slow excretion

D
- AC: no.

E
- Haemodialysis if:
–> Level >2.5
–> Neurological Sx and urinary excretion likely to fail

A
- No.

D
- Always admit.
- Recovery over days- weeks.
- Permanent neurol possible.

Question 3

CARBAMAZEPINE

Answer 3

R
- Usual

R
- >20-50mg/kg= mild/mod
- >50mg/kg / level >40 = DANGER
- Kids: “one pill can kill”
- Effects are predictably dose-dependant

S
- ANTICIPATE:
–> By 4 hours, peak 8-12 hours
–> Sx often fluctuate (erratic absorption)

At lower doses (<50mg/kg)
–> CNS including EYE stuff (eg. nystagmus, mydriasis, ophthalmoplegia)
–> Anticholinergic

At higher doses (>50mg/kg)
–> Coma
–> Na-CHANNEL BLOCKADE (subtle on ECG) –> hypoTN, ventric arrythmia

-SUPPORT:
- Usual
- Sodi Bic in ventric arrythmia

I
- 12-lead, BGL, parac (delib)
- Carbamazepine levels 6hrly (correlate well)

D
- AC: yes in lower-dose (<50/kg)

E
- MDAC: yes IF INTUBATED
- Haemodialysis/ VA ECMO:
–> Prolonged coma with Level >40 at 48hrs or HD instability

A
- No.

D
- OBSERVE
–> 8 hours
Then, home or ward depending on no or mild symptoms.

-HOME WHEN
-Asymptomatic
-Admit ANY symptoms (fluctuant and unpredictable course)

Question 4

SODIUM VALPROATE

Answer 4

R
- Usual

R
- Most just drowsy and supportive
- >200mg/kg significant
- >1g/kg lethal
- Kids: accidental is benign
- Levels correlate well with prognosis:
—> Level >7000 = MODS

S
- ANTICIPATE:
–> Any = mild drowsy
–> >400/kg = Coma, MODS
–> 1g/kg = Fatal + METABOLIC: (lactic acidosis, ammonia, hypoNa/Ca/glyc…) + bone marrow suppression.

-SUPPORT:
- Usual

I
- 12-lead, BGL, parac (delib)
- Valpro level (correlates) 4 hourly
- - Lactate + ammonia

D
- AC: yes in larger doses (>400/kg)
- Repeat in 4 hours if level rising

E
- Haemodialysis if:
–> 1g/kg
–> Level > 7000 umol/L (1000mg/L)
–> Lactic acidosis
–> HD instability

A
- No

D
- OBSERVE
–> 8-12 hours

Question 5

PHENYTOIN

Answer 5

R
- Usual

R
- > 20mg/kg significant
- > 100mg/kg potentially dangerous
- Kids: accidental usually benign

S
- ANTICIPATE:
- Usually pretty benign
–> 20mg/kg: CEREBELLAR (dysarthia, ataxia, nystagmus)
–> >100mg/kg: coma, seizure- RARE even in massive OD.

-SUPPORT:
- Usual (GCS related)

I
- 12-lead, BGL, parac (delib)
- Phenytoin level (correlates)

D
- AC: yes consider

E
- No
- Good outcomes with supportive Mx

A
- No

D
- OBSERVE
–> 12 hours ish

-HOME WHEN
–> Walking safely

NA CHANNEL BLOCKADE WHEN GIVEN RAPID IV only

Question 6

What is the lithium level that indicates toxicity?

Answer 6

> 2.5