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Does Paralysis Contribute to Awareness Under Anesthesia?

Sebel, Peter S. MB BS, PhD, MBA; Bowdle, T Andrew MD, PhD; Ghoneim, Mohamed M. MD; Rampil, Ira J. MD; Padilla, Roger E. MD; Gan, Tong Joo MB BS, FRCA, FFARCSI; Domino, Karen B. MD, MPH

doi: 10.1213/01.ANE.0000151474.73594.80
Letters to the Editor: Letters & Announcements

Emory University School of Medicine; Atlanta, GA; peter_sebel@emoryhealthcare.org (Sebel)

University of Washington Medical Center, Seattle; WA (Bowdle)

University of Iowa; Iowa City, IA (Ghoneim)

State University of New York; Stony Brook, NY (Rampil)

Memorial Sloan-Kettering Cancer Center; New York, NY (Padilla)

Duke University; Durham, NC (Gan)

Harborview Medical Center; Seattle, WA (Domino)

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In Response:

We thank Dr. Metz for his interest in our study and question concerning the relationship of awareness under general anesthesia and neuromuscular blockade. As Dr. Metz points out, 5 patients in our study had intraoperative awareness despite the lack of neuromuscular blocking agents. Although our study was not designed to evaluate the relationship of awareness with anesthetic agents, our limited data for approximately half of the study patients suggests that neuromuscular blockade was used in 65% percent of the study patients.

The fact that awareness can occur in a patient who is fully capable of movement is well described in a study of nearly 12,000 Swedish patients by Sandin et al. (1). The incidence of awareness was 0.10% in the absence of neuromuscular blocking drugs (4 patients), compared with 0.18% in the presence of neuromuscular blockade (14 patients). In addition, other studies have observed awareness and recall in the absence of neuromuscular blockade (2). While nonparalyzed patients may recall intraoperative events, they may less likely to describe severe pain or anxiety than patients who are incapable of movement. Sandin et al. (1) found that none of the 4 nonparalyzed patients had anxiety during the period of recall or postoperative nightmares and anxiety. However, the long-term outcome of patients with intraoperative awareness is unclear, as these investigators found a surprising number of psychological sequelae after intraoperative awareness in a 2-year postoperative follow-up of their patients (3). In fact, two of the patients who had been aware during nonrelaxant anesthesia and had denied nightmares in the immediate postoperative period, developed moderate symptoms of posttraumatic stress disorder.

Thus, awareness with recall during general anesthesia can occur in the absence of neuromuscular blockade. While these episodes may be associated with less pain or anxiety than in the paralyzed patient, the ultimate psychological outcome is unclear.

Peter S. Sebel, MB BS, PhD, MBA

Emory University School of Medicine; Atlanta, GA; peter_sebel@emoryhealthcare.org

T. Andrew Bowdle, MD, PhD

University of Washington Medical Center; Seattle, WA

Mohamed M. Ghoneim, MD

University of Iowa; Iowa City, IA

Ira J. Rampil, MD

State University of New York; Stony Brook, NY

Roger E. Padilla, MD

Memorial Sloan-Kettering Cancer Center; New York, NY

Tong Joo Gan, MB BS, FRCA, FFARCSI

Duke University; Durham, NC

Karen B. Domino, MD, MPH

Harborview Medical Center; Seattle, WA

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References

1. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000;355:707–11.
2. Wennervirta J, Ranta SOV, Hynynen M. Awareness and recall in outpatient anesthesia. Anesth Analg 2002;95:72–7.
3. Lennmarken C, Bildfors K, Enlund G, et al. Victims of awareness. Acta Anaesthesiol Scand 2002;46:229–31.
© 2005 International Anesthesia Research Society