The rise of sugammadex has lead me down a path looking into wider aspects of my own neuromuscular blocking drug (NMBD) use. The evidence for NMBD use, monitoring and reversal is interesting, both for how consistently the same messages have been repeated over the past three decades – and for how little we have improved our practice in spite of mounting evidence demanding that we should.1
I need to do better and you probably also need to do better with how we manage NMBDs.
What is PORC?
Post-operative residual curarisation (PORC) or residual paralysis, refers to persisting neuromuscular blockade in a patient after extubation. It is considered present when the Train-of-four (TOF) ratio is less than 0.9, usually measured in recovery or the post anesthesia care unit (PACU).
The historical comparison of studies investigating PORC is difficult because for many years a TOF ratio of 0.7 was considered the cutoff value for PORC. Volunteers given d-tubocurarine had normal vital capacity and inspiratory force when the TOFR recovered above 0.7. Then in the mid-1990s a TOF ratio of 0.8 was used in studies investigating PORC.
Now in the 21st century a TOFR 0.9 is considered the cut-off for defining PORC. A TOFR 0.9 has been chosen because consequences of residual paralysis, such as pharyngeal dysfunction and impairment of respiratory function have been shown below this TOF ratio.
Case in point: Donati F. Neuromuscular monitoring: what evidence do we need to be convinced? Anesth Analg. 2010 Jul;111(1):6-8. (pubmed) ↩