Neuromuscular Blockade in ICU

Neuromuscular Blockade in ICU

2006-2-15 by 葉育彰

Indications

Depolarizing muscle relaxant

Emergent intubation

*Avoid in patients with hyperkalemia

Non-depolarizing muscle relaxant

Facilitation of mechanical ventilation

Control of ICP

Control of painful cramps in patients with tetanus

Decrease oxygen consumption

Caution

Use sedatives and analgesics before muscle relaxants

Drug

Depolarizing muscle relaxant

Succinylcholine (SCC) – for emergent intubation

Non-depolarizing muscle relaxant

Pancuronium^# (Pavulon) – *bolus or continuous

Bolus: 0.05-0.1 mg/kg loading then 0.01-0.02 mg/kg every 1-2h 

Continuous: 0.05-0.1 mg/kg loading then 1-2 μg/kg/min

ex: For 50 kg patient

2.5-5 mg loading then 2 ml/h (Pancuronium: 2 mg/ml)

Adjust 0.2-0.4 ml/h every 30 min to steady state

Once steady state is achieved, adjust 0.2-0.4 ml/h every 4 h

 ^# Avoid in patients with hepatic or renal dysfunction or contraindication to vagolytic drugs

Cisatracurium (Nimbex) – *continuous

Continuous: 0.1-0.2 mg/kg then 2-3 μg/kg/min

ex: For 50 kg patient

5-10 mg loading then 3 ml/h (Pancuronium: 2 mg/ml)

Adjust 0.2-0.4 ml/h every 30 min to steady state

Once steady state is achieved, adjust 0.2-0.4 ml/h every 4 h

* Recommended

Monitor the degree of block

Bolus - 

Watch regaining some muscle activity before next dose

Continuous -

1. TOF – one to two twitches

2. Clinical assessment – Ventilator dyssynchrony

3. Daily interruption – watch regaining some muscle activity – re-titration

TOF monitoring

Ø   50 mA / 200μsec / 2Hz

Ø   The ratio of response to the first and fourth twitches is a sensitive indicator of nondepolarizing muscle relaxation

Ø   The sequential disappearance of the twitches,

Disappearance of the fourth – 75% block

The third – 80% block

The second – 90% block

Clinical relaxation requires 75-95% blockade

Ø   Definition of steady state in ICU: 1 to 2 twitches

Ø   Monitoring in ICU

Every 5 min for the first 30 min after the loading dose

Then every 30 minutes until steady state was achieved.

Then every 4 hours

Ø   Stimulation: Distal ulnar nerve

Observation: Adductor pollicis twitch response – thumb movement

Ø   Stimulation: Facial nerve

Observation: Orbicularis oculi

Clinical assessment

Ventilator dyssynchrony

Bucking

Elevated mechanical ventilation peak pressure ↑ 4 cmH₂O