Remifentanil
Chemical
Rapid onset, ultrashort acting
Synthetic selective µ agonist of PHENYLPERIDINE CLASS
Use
- Transient profound analgesia (CVS response laryngoscopy)
- Long case → avoid accumulation of opioid
- NeuroSx → stable CVS & quick recovery for assessment
- 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