DOI: 10.1097/01.SA.0000414677.82085.0d

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Issn Print: 0039-6206

Publication Date: 2012/06/01


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Intraoperative Acceleromyography Monitoring Reduces Symptoms of Muscle Weakness and Improves Quality of Recovery in the Early Postoperative Period

Glen S. Murphy; Joseph W. Szokol; Michael J. Avram; Steven B. Greenberg; Jesse H. Marymont; Jeffery S. Vender; Jayla Gray; Elizabeth Landry; Dhanesh K. Gupta

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Excerpt

When neuromuscular-blocking agents (NMBAs) are given to patients intraoperatively, they may later experience residual neuromuscular blockade in the postanesthesia care unit (PACU). Up to 64% of patients given intermediate-acting NMBAs have evidence of incomplete neuromuscular recovery, defined as a train-of-4 (TOF) ratio less than 0.9. Train-of-4 ratios less than 0.9 are associated with reduced upper airway volumes, airway obstruction, hypoxemia, and postoperative pulmonary complications along with notable delays in reaching PACU discharge criteria. Small degrees of residual blockade can be reliably detected only with the use of quantitative neuromuscular monitoring. This randomized study compared the use of acceleromyography monitoring with the conventional qualitative TOF monitoring in patients during their PACU stay.
A total of 155 patients undergoing elective surgery requiring neuromuscular blockade with a duration of at least 60 minutes were randomly assigned to the acceleromyography or TOF control group. Anesthetic management was standardized in all patients and standard monitoring was applied in the operating room. Anesthesia was with propofol, lidocaine, fentanyl, and rocuronium, supplemented with boluses of fentanyl. Neuromuscular monitoring (TOF-Watch SX; Bluestar Enterprises, Chanhassen, Minn) was applied to patients in both groups on arrival in the operating room. In the acceleromyography group, the data panel of the TOF-Watch SX was uncovered, and the TOF ratio information displayed was then used to guide intraoperative management. In the control group, the cover over the display panel was not removed and the TOF-Watch SX was used as a standard qualitative peripheral nerve stimulator because clinicians did not have access to the TOF ratio data. Additional doses of rocuronium were given to maintain a TOF count of 2 to 3 during portions of the operation requiring neuromuscular blockade. At the end of the surgery, when a TOF count of at least 3 was present, neuromuscular blockade was reversed with neostigmine 50 μg/kg and glycopyrrolate 10 μg/kg. Immediately on arrival to the PACU, the patient’s TOF ratios were measured using acceleromyography. A standardized examination was used to assess 16 symptoms and 11 signs of residual paresis and repeated 20, 40, and 60 minutes after PACU admission. Aldrete scores were assessed at arrival in the PACU and every 10 minutes for the next 60 minutes. Times required to meet discharge criteria and actual discharge were recorded. Quality of recovery (QoR) was quantified using QoR-9 (scores range from 0 to 18; that is, from extremely poor to extremely high QoR) and a 100-mm visual analog scale. The primary outcome variables were overall weakness scores, total number of symptoms of muscle weakness, and total number of signs of muscle weakness on admission to the PACU and every 20 minutes thereafter to 1 hour.
Five patients were excluded from the analysis because of protocol violations. The 2 groups did not differ in sex, age, weight, height, preexisting medical conditions, American Society of Anesthesiologists physical status, type of surgical procedure, duration of anesthesia, use of crystalloids, blood loss, or core temperature at the end of the procedure. Total doses of rocuronium used and numbers of repeat doses were similar in the 2 groups. Train-of-4 ratios on PACU admission were 0.98 (range, 0.48-1.28) in the acceleromyography group compared with 0.88 (range, 0.33-1.26) in the control group, a statistically significant difference. Train-of-4 ratios less than 0.9 were recorded in 14.5% of patients in the acceleromyography group and 50% of the controls; ratios less than 0.7 were recorded in 4.0% and 18.9% of patients, respectively. The acceleromyography patients had less overall weakness and fewer symptoms of muscle weakness at all time points.
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