Article Notes
This small (N=64) post-operative audit of children receiving muscle relaxants in an Australian tertiary paediatric hospital identified a 28% incidence of post-operative residual paralysis, measured immediately before extubation.
Worryingly, the incidence of residual paralysis was even higher in the subgroup reversed with neostigmine (38%), which the authors attribute to anaesthetists not waiting long enough after administration.
Severe residual paralysis (TOFR < 0.7) was observed in 7% of cases.
Only 23% of anaesthetists used intra-operative neuromuscular monitoring.
Observation of pharyngeal function in 14 awake volunteers demonstrated pharyngeal dysfunction and increased aspiration risk at TOF ratios < 0.90.
“Partial neuromuscular paralysis caused by atracurium is associated with a four- to fivefold increase in the incidence of misdirected swallowing. … The majority of misdirected swallows resulted in penetration of bolus to the larynx.”
(Sundman in a 2000 follow-up study: The incidence and mechanisms of pharyngeal and upper esophageal dysfunction in partially paralyzed humans: pharyngeal videoradiography and simultaneous manometry after atracurium.)
Debaene et al. investigated residual paralysis in the PACU after a single intubating dose of intermediate NMBD in the absence of reversal.
They identified PORC (Post-Operative Residual Curarization = TOFR <0.9) in 45% of patients, with 'time since NMBD' ranging from 30 to 400 minutes.
In a subgroup of patients 2 hours after a single NMBD dose there was still a 37% incidence of PORC.
Additionally there was very wide inter-patient variability, with PORC persisting more than 6 hours in three patients, and several patients with TOFR of only 0.2 after 2 hours.
In 83 patients researchers compared intubation with propofol 1.5 mg/kg, remifentanil 0.30 μg/kg/min & sevoflurane 1.0 MAC to intubation with the same propofol & remifentanil dose, along with rocuronium 0.45 mg/kg.
Acceptable intubating conditions were 18% more frequent in the muscle relaxant group than in those receiving propofol/remi/sevo.
Incidence of laryngeal injury, hoarseness and sore throat was similar between the two groups - which is different to the result from an earlier, larger study of intubation without relaxant: Comparison of two induction regimens using or not using muscle relaxant: impact on postoperative upper airway discomfort.
Make sure to read the editorial in the same issue from Schneider, Restrict relaxants, be aware, and know the limitations of your depth of anaesthesia monitor, and a related study from back in 2003 from Messner, The bispectral index declines during neuromuscular block in fully awake persons.
This very large cohort study demonstrated an association between use of intermediate-duration NMBD and risk of postoperative desaturation and reintubation requiring ICU admission, and a similar association with these outcomes and neostigmine reversal.
Qualitative neuromuscular monitoring did not reduce this risk.
Study population was all patients at Massachusetts General Hospital undergoing general anaesthesia including a muscle relaxant over a 4 year period, and who were extubated at the end of the procedure.
This is a most fascinating study, both academically, clinically and psychologically. The full Method deserves to be read, along with the participant's description of their experience in the Results.
...fasciculations attributable to suxamethonium were painful, and the ensuing paralysis was experienced as a feeling of profound heaviness, ‘as if someone had pulled the plug and drained the fluid out’.
Interesting editorial accompanying Dr Peter Schuller's excellent study of BIS values in awake, paralysed volunteers.
The editors make a very interesting point critiquing the probabilistic, database-based approach to processed-EEG awareness monitors like BIS: (emphasis added)
"This database-driven approach may have limitations, in particular for the detection of intraoperative wakefulness: it is very unlikely that data from an awake and paralyzed subject are included in this database. Therefore, the resulting anaesthesia index has not been trained with a dataset that contains this clinical situation..."