Reversal of Neuromuscular Blockade

Abstract

To the Editor: In a recently published article, Hovorka et al. [1] reported that reversal of neuromuscular blockade with a combination of neostigmine 2 mg and glycopyrrolate 0.4 mg had no effect on the incidence or severity of postoperative nausea and vomiting (PONV). They imply that the previous studies [2-4] yielding positive results were invalid because the group sizes were inadequate. However, as mentioned in our previous studies [2,3], the effect of the reversal drugs on PONV is limited to the early recovery period. In their Table 2, the authors provide the time-related incidences of nausea and vomiting listed separately, but not the total incidence of nausea and vomiting. At each sampling interval, the incidence of nausea or vomiting varied from 0% to 25%; however, the incidences from 0 to 27 h were much higher (28%-40%). From this Table, it is not possible to determine the cumulative incidence of nausea, vomiting, or combined nausea/vomiting in the postanesthesia care unit. Of interest, there seems to be a significant difference between the reversed (A) and nonreversed (B) groups in the incidence of vomiting 1-2 h after surgery (12% vs 0%; P < 0.01). Finally, the incidences of PONV reported in the postanesthesia care unit in a study involving inpatients undergoing abdominal hysterectomy procedures may not be comparable to outpatients undergoing laparoscopic surgery! The well known effect of movement and postural hypotension in increasing PONV symptoms after ambulatory surgery may not be observed in the abdominal hysterectomy patient population. We were surprised that this factor was not mentioned as a possible explanation for the apparently conflicting results. In conclusion, we feel that the title of this article is misleading because the findings of Hovorka et al. [1] may not apply to the high-risk outpatient populations (e.g., laparoscopic, otolaryngologic, opthalmologic procedures) used in some of the earlier clinical studies [2]. Paul F. White, PhD, MD, FANZCA Mehernoor F. Watcha, MD Department of Anesthesiology and Pain Management; The University of Texas Southwestern Medical Center; Dallas, TX 75235