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03-11-2011 | Surgery | Article

Intraoperative acceleromyography improves patients’ postanesthesia experiences


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MedWire News: Results of a randomized trial show that intraoperative acceleromyography monitoring reduces the number and severity of unpleasant muscular symptoms caused by residual neuromuscular blockade on waking from general anesthesia.

It is well-established that acceleromyography monitoring reduces the number of patients who still have a train-of-fours (TOF) ratio below 0.9 on emergence from anesthesia. For the current study, Glenn Murphy (University of Chicago Pritzker School of Medicine, Illinois, USA) and colleagues studied the subjective experiences of patients in the postanesthesia care unit (PACU).

They randomly assigned 155 patients to receive intraoperative acceleromyography monitoring or conventional qualitative TOF monitoring. As expected, residual blockade (TOF ratio <0.9) was much less frequent in the acceleromyography group than in the control group, at 14.5% versus 50.0%.

The patients completed tests for 11 objective signs of residual weakness, including the 5 second head lift, hand grip, and eye opening tests. Less than 6% of the patients failed these tests and the median number of signs of weakness was 0 in both groups.

"Although most patients successfully completed these tests with small degrees of neuromuscular blockade, many subjectively experienced difficulty completing the task or felt uncomfortable during the performance of the test," the team notes in the journal Anesthesiology.

For example, 52.7% had subjective difficulty with the eye opening test, 43.2% with tracking an object with their eyes, and 36.6% with speaking. The acceleromyography group had significantly fewer subjective symptoms of muscle weakness at all time-points (PACU admission, and 20, 40, and 60 minutes later), compared with the control group.

Subjective general weakness was present in 59.6% of all patients, and was significantly less, on a scale of 0-10, in the acceleromyography than control groups, at a median of 4 versus 6 points on admission to the PACU, falling to 2 versus 4 points an hour later.

The presence of at least five subjective symptoms was 87% sensitive and 82% specific for a TOF ratio below 0.9. "In contrast, clinical signs or bedside tests of muscle weakness were poor prognosticators of residual paresis and were not useful in assessing a patient's subjective sense of well-being," say Murphy et al.

Editorialists Sorin Brull (Mayo Clinic, Jacksonville, Florida, USA) and Mohamed Naguib (Cleveland Clinic, Ohio, USA) describe the study as "unique and important."

They highlight that anesthesiologists "continue to disregard obvious findings" showing that muscle weakness from residual neuromuscular blockade is an important safety issue.

"Because we can in most instances 'get away' with our clinical assessment and intuition about the state of reversal of our patients, we have little incentive to spend extra resources on purchasing monitors… or expend additional time applying the somewhat unwieldy electrodes and wires of the nerve stimulators," say Brull and Naguib.

"However, we must ask ourselves whether we are really doing the best for our patients when we cut corners."

By Eleanor McDermid

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