Canadian Study Reveals High Rate Of Residual Paralysis
Paresis observed in nearly 60% of patients undergoing abdominal procedures
by Michael Vlessides
More than half of patients undergoing elective open abdominal or laparoscopic surgery experience residual neuromuscular blockade after tracheal extubation, according to an interim analysis of a Canadian multicenter study.
“There are currently no prospective, multicenter studies assessing residual paralysis in Canada,” said Andre Galarneau, PhD, medical advisor at Merck Canada in Kirkland, Quebec, who led the study. “When we started asking researchers to estimate the incidence of residual paralysis in their centers, everyone was saying between 10% and 15%. But as we found out, it’s actually a lot more than that.”
The RECITE study (REsidual Curarization and its Incidence at Tracheal Extubation) prospectively examined the incidence of residual neuromuscular blockade (defined by the researchers as a train of four [TOF] ratio lower than 0.9) during routine anesthesia practice.
The interim analysis included 141 patients recruited at eight centers between June and December 2011. Neuromuscular function was assessed in each subject using acceleromyography. Although the attending anesthesiologist and nurses in the post-anesthesia care unit (PACU) were blinded to the results of acceleromyography monitoring, they were free to provide care to the patients as they saw fit. That flexibility included the dosing of the neuromuscular blocking agent, administration of the reversal agent and the decision to extubate.
The use of reversal agents and the effect of neuromuscular blocker reversal on the incidence of residual neuromuscular blockade were assessed both at extubation and on arrival in the PACU.
“You need to reach a TOF of 0.9 to be considered to be safely extubated and not have any residual paralysis,” said Dr. Galarneau, who reported the findings at the 2012 annual meeting of the Canadian Anesthesiologists’ Society (abstract 1344674).
The study population was primarily female (74%), with a median age of 45 years. Patients were undergoing laparoscopic (54%) or open abdominal (46%) surgeries, and rocuronium was used in 99% of cases. Patients received neostigmine for reversal; the median dose was 35 mcg/kg (range, 6-77 mcg/kg).
Table. Incidence of Residual Neuromuscular Blockade (TOF<0.9)
No Reversal Agent
At extubation (n=141)
On PACU arrival (n=126)
PACU, post-anesthesia care unit; TOF, train-of-four
The overall incidence of residual paralysis was 57% at tracheal extubation and 45% on arrival to the PACU (Table).
Yet despite the fairly high rate of residual blockade in the study subjects, Dr. Galarneau was not surprised by the findings. “We hypothesized that we would find a rate of about 30%, but other studies have shown that these rates can be all over the map,” he said. “Nevertheless, the power of this study is that it’s multicentered and there was very little difference in terms of residual neuromuscular blockade rates between centers.”
Residual paralysis has proved to be a nettlesome problem for anesthesiologists. Recent data suggest that as many as 40,000 surgery patients in the United States each year experience serious respiratory problems resulting from unresolved neuromuscular blockade (seeAnesthesiology News, August 2011, page 1). Better use of conventional reversal agents or other interventions may be warranted in the typical clinical setting. Other potential solutions include improving the timing of reversal and better monitoring of patients, according to Dr. Galarneau.
Colin J.L. McCartney, MBChB, director of anesthesia research at Sunnybrook Health Sciences Centre in Toronto, Ontario, found the study’s incidence of residual neuromuscular block surprisingly high. “However, it is important to realize that these data are not from a randomized trial, nor do we have any information on rocuronium dose or incidence of any patient complications (subjective or objective) related to residual neuromuscular block. In other words, although the measured incidence of residual neuromuscular block was high, did this in fact make any clinical difference?”
He added, “Nevertheless, I agree with the investigators that the study underlines the need to monitor neuromuscular block in all patients given muscle relaxants, and further research to determine the clinical impact of residual neuromuscular block.”
Merck makes the reversal agent sugammadex, which is sold as Bridion outside the United States. The company hopes to obtain FDA approval for its drug later this year.