Intubation using propofol and remifentanil without muscle relaxant is associated with a greater incidence of poor intubating conditions.
Schlaich et al. compared intubation using only propofol and remifentanil with the addition of rocuronium at various doses (0.3, 0.45, 0.6 mg/kg) in four groups of 30 patients. Intubating conditions were poor in 40% of those not receiving rocuronium, versus almost universally good conditions (89 of 90) when rocuronium was used.
Intubation without muscle relaxant is associated with greater incidence of sore throat, hoarseness, hypotension, bradycardia and intubation difficulty.
Researchers compared induction with propofol (2.5 mg/kg), alfentanil (15 µg/kg) and rocuronium (0.6 mg/kg) to using propofol (2.5 mg/kg) and alfentanil (40 µg/kg) alone. Patients who did not receive muscle relaxants experienced more sore throat and hoarseness, more hypotension and bradycardia and a 10 times greater incidence of intubation difficulty.
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 paper is full of many important pearls, and should be read in full.
Regarding common practices in the conduct of BIS-guided anaesthesia:
It has been suggested that a BIS range of 60–75 is suitable for ‘the end of surgery’, but our results show that if neuromuscular block is used, this range is consistent with full awareness.
...and on the use of the Signal Quality Index:
Given that the major cause of patient-related artifact is movement, it is not surprising that the SQI will increase towards 100 when NMBDs are administered, as we found. Unfortunately, the high SQI will indicate that the BIS is at its most reliable exactly when it is performing most poorly in the aware but paralysed patient.
Muscle paralysis alone in an awake subject can cause significant drop in the Bispectral Index Score (BIS) to below that normally indicating unconsciousness and deep anaesthesia.
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’.
Researchers induced awake paralysis in 10 volunteers using separately both suxamethonium and rocuronium. Both the BIS A2000 (2003) and BIS Vista monitor (2013) were tested.
BIS decreased immediately after paralysis and did not fully recover until muscle recovery. BIS values decreased to as low as 44, despite the subject being awake.
In more than half of the 20 trials the BIS value decreased to below 60 at some point. In one case this lasted for almost 4 minutes, representing 76% of the total paralysis time for that subject.
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..."