Correspondence  |   October 2017
In Reply
Author Notes
  • Mayo Clinic College of Medicine, Jacksonville, Florida (S.J.B.).
  • (Accepted for publication June 30, 2017.)
    (Accepted for publication June 30, 2017.)×
Article Information
Correspondence   |   October 2017
In Reply
Anesthesiology 10 2017, Vol.127, 724-725. doi:10.1097/ALN.0000000000001807
Anesthesiology 10 2017, Vol.127, 724-725. doi:10.1097/ALN.0000000000001807
We wish to thank Prof. Hilary Grocott for his excellent letter and for the kind words regarding our review article1 ; we are honored by his praise. In his letter, Prof. Grocott had several important comments to which we would like to respond. First, we attempted to remind the reader that the issue of unintended patient awareness during periods of neuromuscular paralysis may occur in various clinical settings, including the intensive care unit. Specifically, it has been reported that neuromuscular blocking agents may be employed to control shivering (and decrease oxygen consumption) during induction of therapeutic hypothermia, and such therapy “may mask insufficient sedation” that may result in unintended patient awareness and recall.2  This was the basis for our inclusion of the reference.1 
Our discussion of posttetanic count included a description of the “transient increase in the amount of acetylcholine released,” and stated that, “the intensity of subsequent muscle contractions will be increased (potentiated) briefly (period of post-tetanic potentiation, which may last 2 to 5 min).”1 The period of posttetanic potentiation is based on the results reported by Brull et al.,3  which are consistent with the subsequent reports by Hakim et al.,4  as Prof. Grocott correctly points out. These effects are short-lived (minutes) only during clinical situations of steady-state neuromuscular block, however (i.e., during continuous infusion of neuromuscular blocking agents). During recovery from bolus doses of neuromuscular blocking agents, tetanic stimulation shortens the time to 75% recovery of vecuronium from 7.4 ± 2.8 min to 5.0 ± 2.6 min, “such that the response of the tested site may no longer be representative of other muscle groups.”5 
Finally, we are in complete agreement with, and fully supportive of, Prof. Grocott’s call for the American Society of Anesthesiologists to “take a more progressive stance on the subject and advocate for the use of monitoring whenever neuromuscular blocking drugs are used.”
Competing Interests
Dr. Brull has had investigator-initiated funded research from Merck, Inc. (Kenilworth, New Jersey; funds assigned to Mayo Clinic); is a shareholder and member of the Board of Directors in Senzime AB (Uppsala, Sweden); serves as a member of the Board of Directors for Anesthesia Patient Safety Foundation (Rochester, Minnesota); is a member of the Scientific Advisory Board for ClearLine MD (Woburn, Massachusetts) and The Doctors Company (Napa, California); and has a patent-licensing agreement with Mayo Clinic (Rochester, Minnesota). Dr. Kopman declares no competing interests.
Sorin J. Brull, M.D., F.C.A.R.C.S.I.(Hon), Aaron F. Kopman, M.D. Mayo Clinic College of Medicine, Jacksonville, Florida (S.J.B.).
Brull, SJ, Kopman, AF . Current status of neuromuscular reversal and monitoring: Challenges and opportunities. Anesthesiology 2017; 126:173–90 [Article] [PubMed]
Polderman, KH, Herold, I . Therapeutic hypothermia and controlled normothermia in the intensive care unit: Practical considerations, side effects, and cooling methods. Crit Care Med 2009; 37:1101–20 [Article] [PubMed]
Brull, SJ, Connelly, NR, O’Connor, TZ, Silverman, DG . Effect of tetanus on subsequent neuromuscular monitoring in patients receiving vecuronium. Anesthesiology 1991; 74:64–70 [Article] [PubMed]
Hakim, D, Drolet, P, Donati, F, Fortier, LP . Performing post-tetanic count during rocuronium blockade has limited impact on subsequent twitch height or train-of-four responses. Can J Anaesth 2016; 63:828–33 [Article] [PubMed]
Brull, SJ, Silverman, DG . Tetanus-induced changes in apparent recovery after bolus doses of atracurium or vecuronium. Anesthesiology 1992; 77:642–5 [Article] [PubMed]