The Impact of Residual Neuromuscular Blockade, Oversedation, and Hypothermia on Adverse Respiratory Events in a Postanesthetic Care Unit: A Prospective Study of Prevalence, Predictors, and Outcomes
Stewart et al, Anesthesia & Analgesia, Volume 123(4), October 2016, p 859–868
Dr Lena Al-Shammari
Residual neuro-muscular blockade (RNMB) [defined as a TOFR < 0.9] is highly prevalent.
RNMB is associated with adverse respiratory events (AREs).
Monitoring of NMB on PACUs is often omitted.
Prospective cohort study.
A university hospital in Australia.
Adult patients requiring non-depolarising NMB for surgery performed on weekdays.
No change in practice requested.
TOFR (electromyography at wrist [30mA rather than 60m]) & ARE (modified Murphy’s criteria)
599 patients recruited; managed by 81 anaesthetists.
RNMB in 186 (31% [95% CI, 27%–35%]).
Of these, median time to recovery to TOFR >0.9 was 15 min.
Presence of RNMB was associated with 1) type of operation (open abdominal), 2) duration of operation (<90m), 3) use of a reversal agent. After multi-variate analysis: RNMB associated with 1) increasing age, 2) type of operation (open abdominal), 3) length of operation (<90m).
Type of NMB and use of NMB monitoring were not associated with RNMB.
Only 24% of patients had some form of neuromuscular function monitoring.
In patients with RNMB, 21% [16%–28] experienced AREs. This compares to 14% [11–18%] of non-RNMB patients (P = 0.033).
AREs on PACU occurred in 16% [13%–19%]) of all cases – most commonly, obstruction, respiratory distress & mild hypoxaemia.
AREs on the PACU were significantly associated with RNMB, core temperature, and level of consciousness. The association with RNMB was statistically insignificant in the multivariate analysis
RNMB on PACU is common
Reversal agent is being given without depth of NMB monitoring in many cases.
AREs are associated with core temperature and level of consciousness.
2. RNMB assessed in a consistent manner, with most precise monitor for TOF (EMG)
3. Relevant clinical question
1. Observational. Hawthorne effect possible.
2. TOF stimulus amplitude reduced, possibly submaximal
3. Excludes out-of-hours cases and patients taken to ICU
4. No follow-up of patients beyond PACU; may miss some AREs
5. Data is from 2013 – has practice changed since then?
6. No pre-study sample size calculation done
7. Single centre (high rate of deep extubation)
8. Many of the ARE outcomes on the Murphy scale are not severe – are they clinically significant? (eg obstruction requiring jaw thrust)
We know RNMB is not good for patients. This study confirms it’s still common on PACU.
Potential for impact
There is a paper on RNMB and pneumonia in this month’s Anesthesiology (a retrospective cohort study demonstrating a significant link). Together these papers may prompt more attention to our use of NMBs.
Should we be abandoning subjective TOF monitors