Remifentanil

Chemical

Rapid onset, ultrashort acting

Synthetic selective µ agonist of PHENYLPERIDINE CLASS

Use

  1. Transient profound analgesia (CVS response laryngoscopy)
  2. Long case → avoid accumulation of opioid
  3. NeuroSx → stable CVS & quick recovery for assessment
  4. Intense analgesia when you can use NMBD i.e. facial N stimulation required by surgeon

Presentation

Powder

Vials 1mg, 2mg, 5mg

→ Unstable in solution for long periods

→ PHENYLPIPERIDINE CLASS but unique ester linkage

∴ susceptible to rapid hydrolysis by nonspecific plasma & tissue esterases

Dose

X 200 potency of M

Induction: 1mcg/kg/min

Maintenance: 0.25 – 0.5mcg/kg/min

Onset / DoA

UNIONISED 67% – low lipid solubility coefficient 17.9

= rapid onset & short DoA

  • Onset 1 min
  • Offset 2 – 4 mins

MoA

Pure µ OP agonist

PD

CNS – analgesia no effect on ICP/IOP

CVS – ↓HR, ↓BP

MSK – muscle rigidity at high dose

Immuno – no histamine release

Resp – potent resp depression

PK

A

– 

D

VD 0.4L/kg

Very small

Low lipid solubility

PPB 70%

M

Rapid ester hydrolysis

Non-specific plasma & tissue esterases

Into remifentanil acid x 5000 less potent cf. remi

E

Inactive metabolites

Renally excreted

NOT metabolised by plasma cholinesterase ∴not affected by deficiency

HIGH CLEARANCE = 40 – 60ml/kg/min

C5HT: 4 mins REGARDLESS OF INFUSION DURATION

Low lipid solubility + Low VD ∴ rapidly equilibrates with peripheral tissue + rapid metabolism = 4 min C5HT

Adverse Effects

Risk of extreme pain/stress if infusion ceased suddenly without administering longer acting opioid