Preferred Neuromuscular-Blocking Agent in Liver Failure

Mechanism of Action and Metabolism

Atracurium is a non-depolarizing neuromuscular blocking agent that acts by competitively binding to cholinergic receptors at the motor end plate, and is inactivated in plasma by two mechanisms that do not depend on organ function: ester hydrolysis and Hofmann elimination 1, 2
The unique metabolism pathway of atracurium ensures that renal or hepatic dysfunction does not affect the duration of blockade, as stated by the American Society of Critical Care Medicine 3

Clinical practice guidelines note that atracurium has similar pharmacokinetic and pharmacodynamic profiles in patients with and without hepatic failure, according to the Anaesthesia guidelines 1
The Anaesthesia guidelines strongly recommend not modifying the initial dose of muscle relaxants in hepatic failure patients, regardless of the type used 1

Vecuronium is primarily eliminated in bile, and its clearance is reduced in cirrhotic patients with wide variability in the duration of action after repeated injections, as reported by the Anaesthesia guidelines 1
Pancuronium has a prolonged duration of action in patients with hepatic dysfunction as it relies on hepatic metabolism, according to the Critical Care Medicine guidelines 4
Pipecuronium is also dependent on hepatic metabolism and would have unpredictable effects in liver failure, as stated by the Critical Care Medicine guidelines 4

Laudanosine, a breakdown product of atracurium's Hofmann elimination, is metabolized by the liver and can accumulate in patients with hepatic failure, as reported by the Critical Care Medicine guidelines 3, 2

The American Society of Critical Care Medicine recommends using a peripheral nerve stimulator to optimize atracurium dosing, minimize the possibility of overdose, and help evaluate recovery 5
Train-of-four (TOF) monitoring is the most reliable method for evaluating the degree of neuromuscular blockade, as stated by the Praxis Medical Insights guidelines 5
Recovery of a TOF ratio >0.7 typically occurs within 34-85 minutes after drug discontinuation and is independent of organ function, according to the Critical Care Medicine guidelines 3

For patients with grade V liver injury requiring neuromuscular blockade, cisatracurium or atracurium should be used due to their organ-independent elimination via Hofmann degradation and ester hydrolysis, with continuous infusion preferred over intermittent bolus dosing to maintain stable neuromuscular blockade while minimizing total drug exposure 6

Pancuronium is contraindicated as it has prolonged duration of action in hepatic dysfunction due to dependence on hepatic metabolism 6

Continuous infusion is preferred over intermittent bolus dosing for grade V liver injury to maintain consistent neuromuscular blockade and facilitate train-of-four (TOF) monitoring 6
Cisatracurium infusion dosing: Start with 0.1 mg/kg bolus followed by 2-8 μg/kg/min continuous infusion, titrated to TOF response 7
Atracurium infusion dosing: Start with 0.5 mg/kg bolus followed by 0.6 mg/kg/hr (10 μg/kg/min) continuous infusion 8

TOF monitoring is mandatory for all patients receiving neuromuscular blockade, particularly in hepatic failure 6
Target TOF count of 1-2 twitches out of 4 to achieve adequate paralysis while avoiding excessive blockade 6
Recovery is defined as TOF ratio >0.7, which typically occurs within 34-85 minutes after cisatracurium discontinuation, independent of organ function 7

Consider daily drug holidays (stopping NMBAs until clinical condition necessitates restart) to decrease the incidence of acquired quadriplegic myopathy syndrome (AQMS), particularly important in patients also receiving corticosteroids 6
Discontinue NMBAs as soon as clinically feasible to minimize complications 6
For patients receiving both NMBAs and corticosteroids, make every effort to discontinue NMBAs as soon as possible due to increased risk of prolonged weakness and myopathy 6
Cisatracurium produces less laudanosine than atracurium (peak concentrations 16-21 ng/mL vs higher with atracurium), making it the safer choice for prolonged use 7

Quantitative train‑of‑four (TOF) monitoring with a peripheral nerve stimulator should be employed continuously during atracurium administration to optimise dosing, minimise overdose risk, and assess recovery of neuromuscular function. 9
After reversal agents have been given, TOF monitoring must be continued until the TOF ratio reaches ≥ 0.9, confirming adequate recovery. 9

Reversal of atracurium‑induced block should be performed with neostigmine 0.04 mg kg⁻¹ combined with atropine 0.02 mg kg⁻¹. 9
Reversal attempts are appropriate only when the TOF count shows the reappearance of at least 2–4 twitches (i.e., a partial return of muscle response). Initiating reversal at deeper levels of block or with insufficient doses increases the risk of residual neuromuscular weakness. 9