The Effect of an Expandable Polyvinyl Acetate (Merocel) Pack on the Healing of the Nasal Mucosa of Sheep David McIntosh, M.B.B.S.,*# Allison Cowin, Ph.D.,#§ Damian Adams, Ph.D.,#§ and Peter-John Wormald, M.D.,*# (Australia) ABSTRACT Background: There is a lack of knowledge about the healing of the nasal respiratory mucosa after endoscopic sinus surgery (ESS). Nasal packs often are placed after ESS in an attempt to improve hemostasis and reduce adhesion formation. Most na- sal packs need to be removed in the postoperative period. This is uncomfortable for the patient and the affect of these packs on the healing process is unknown. Methods: We have standardized the sheep as a suitable animal model to examine the healing of the nasal epithelium after ESS. The nasal mucosa of sheep was wounded under endoscopic guidance and either packed with expandable polyvinyl acetate– based pack (Merocel), which was removed at the 5th postop- erative day, or left unpacked to serve as control. Serial biopsies of the wounded area were taken every 28 days, up to 112 days postwounding, for examination using light and scanning elec- tron microscopy. Results: There was no significant difference in the rate of reepithelialization between the packed and control sides of the sheep (p  0.05). There was no significant difference in the total amount of surface cilia coverage between the packed and control sides at any time points (p  0.05). There was no significant difference in the maturity of the cilia between the packed and control sides at any time points (p  0.05). Conclusion: The use of Merocel packing postoperatively nei- ther impairs nor promotes wound healing in the postoperative period. (American Journal of Rhinology 19, 577–581, 2005) E ndoscopic sinus surgery (ESS) is the accepted form of surgical treatment for chronic rhinosinusitis that does not respond to medical therapy. The complications of this type of surgery include bleeding and the development of postoperative adhesions. 1 These adhesions may block the normal mucociliary drainage pathways of the sinuses caus- ing a recurrence of disease. To prevent postoperative bleed- ing and adhesions, nasal packing often is used. 1 Concerns about nasal packing include toxic shock syndrome 2 and the possibility of bacterial growth by occluding sinus ostia. 3 The most frequent problem with nasal packing comes at the time of removal, which can be the most unpleasant experi- ence associated with the operation and may be associated with hemorrhage. 4 This bleeding may be associated with reopening of the surgical wound and this may contribute to From the *Department of Surgery–Otolaryngology, Head and Neck Surgery, Adelaide and Flinders Universities, South Aus- tralia, Australia, #CRC for Tissue Growth and Repair, Ad- elaide, South Australia, Australia, §Child Health Research Institute, Women’s and Children’s Hospital, North Adelaide, South Australia, Australia Funded in part by the CRC for Tissue Growth and Repair, the Royal Australasian College of Surgeons, and the University of Adelaide. Xomed-Medtronic provided the nasal packing mate- rial (Merocel) Address correspondence and reprint requests to P.-J. Wormald, M.D., Department of Surgery–Otolaryngology, Head and Neck Surgery, Adelaide and Flinders Universities, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, S.A. 5011, Australia Copyright © 2005, OceanSide Publications, Inc., U.S.A. American Journal of Rhinology 577