Autonomic Agents

Question 1

Features of ANTICHOLINERGIC toxidrome:

Answer 1

“Mad as a hatter
Hot as a desert
Blind as a bat
Red as a beet
Dry as a bone
Full as a flask”

Delirium
—> typically: restless, fidgeting, picking, hallucinations,
—> Tremor
Mydriasis
Flushed skin, fever
Dry mouth
Urinary retention
Absent bowel sounds

Risk of: coma, seizure, arrythmia.

Question 2

Management of ANTICHOLINERGIC toxidrome:

Answer 2

PHYSOSTIGMINE 1mg over 5 mins, repeat 10 mins
–> Treats central features only

BZD for agitation, temp control
Fluids to prevent rhabdo/AKI
IDC for retention

Question 3

Examples of ANTICHOLINERGIC drugs:

Answer 3

• Atropine
• Oxybutynin
• Glycopyrrylate
• Benztropine
• Tiotropium
• Carbamazepine
• Antipsychotics
• TCAs
• SSRIs

+many more.

Question 4

Features of CHOLINERGIC toxidrome:

Answer 4

Muscarinic= DUMBELS
Nicotinic= FAT and Weak

Diarrhoea
Urination
Miosis
Bradycardia, bronchorrhoea
Miosis
Lacrimation
Salivation

(eg. Neostigmine, Rivastigmine, Physostigmine)

Question 5

Management of CHOLINERGIC toxidrome:

Answer 5

ATROPINE 20 microg/kg
–> Double the dose every 5 mins until dried up

BZD for agitation

Most will be ORGANOPHOSPHATE (eg. PPE, pralidoxime- see own section)

Question 6

Features of SEROTONERGIC toxidrome:

Answer 6

Almost always >1 agent
If single agent, never life-threatening

Triad: CNS, Autonomic, Neuromuscular- all elevated.

CNS:
- Agitation —> coma
AUTO:
- Hyperthermia, PR, RR, BP
- Sweaty
- Mydriasis
NEUROMUSC:
- Increased tone (LL > UL)
- Hyperreflexia and clonus

…Rhabdo, renal failure, DIC.

Self limiting in hours
Worst cases 1-2 days

Question 7

Management of SEROTONERGIC toxidrome:

Answer 7

Cease agent/s

Charcoal- YES

MILD/MOD:
- Control temp/ PR/ BP
—>1: IV BZD
–> 2: GTN infusion

-CYPROHEPTIDINE
—> 8mg PO 8 hourly (4mg child)
-Observe 8 hours

SEVERE
- I&V, paralyse
- Active cooling
- Hydrate to prevent rhabdo
- Resolution over days
*No role for cypro

Question 8

Which drug classes are SEROTONERGIC?

Answer 8

SSRI
SNRI
MAOI
TCA

TRAMADOL
Fentanyl, pethidine

Lithium

Amphetamines

Tryptophan
St John’s wort
Spirulina

Question 9

ANTIHISTAMINE OD

Answer 9

R
- Usual

R
- Nil specific
- Kids: accidental likely benign

S
ANTICIPATE:
- Mild sedation
- Mild anticholinergic
- QT prolongation only one that matters (Torsades)

SUPPORT:
- 4 hourly ECGs until QT improving
- Severe QT/ Torsades:
–> Usual
(elecs, isopren/pace, Mg)
- Anticholinergic:
–> Usual
(BZD, physostigmine for central)

I
- 12-lead, BGL, parac (delib)

D, E
- No

A
- Physostigmine for central antichol

D
- OBSERVE
–> 6 hours
- HOME WHEN
–> QT improving

Question 10

What additional concerns are there with SEDATING antihistamines?

Answer 10

eg. promethazine, doxylamine, cyprohep

• Sedation
• Some, in massive OD: Na channel blockade

Question 11

THEOPHYLLINE OD

Answer 11

ANY OD is potentially lethal (narrow TI)
“One pill can kill”

Very, very bad prognosis

• Severe, refractory hypoK (mg, PO4)
• Severe, refractory shock
• Hypoglycaemia
• Seizure

Need HAEMODIALYSIS
- Level > 550 umol acute OR SYMPTOMS OF TOX
- Level >330 umol chronic
- High-dose, arrhythmia, seizure or hypoTN.