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Wound hypoxia in deep tissue after incision in rats

Authors

  • Sinyoung Kang MD, PhD,

    1. Department of Anesthesia, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
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  • Dongchul Lee MD,

    1. Department of Anesthesia, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
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  • Brett E. Theusch MD,

    1. Department of Anesthesia, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
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  • Christopher J. Arpey MD,

    1. Department of Dermatology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
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  • Timothy J. Brennan MD, PhD

    Corresponding author
    1. Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
    • Department of Anesthesia, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
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Reprint requests:

Dr. T. J. Brennan, Department of Anesthesia, 200 Hawkins Drive, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.

Tel.: +1 319 356 7319;

Fax: +1 319 356 2940;

Email: tim-brennan@uiowa.edu

Abstract

Our previous studies using rat models of incisional pain have shown that tissue lactate levels increase and pH decreases for several days after incision, suggesting the presence of an ischemic-like condition. The purpose of this study was to evaluate the time course and the extent of tissue hypoxia that develops in incised muscle and skin. We directly measured oxygen tension at several time points after incisions of the gastrocnemius muscle, the paraspinal skin, and the plantar hindpaw in anesthetized rats using an oxygen-sensitive microelectrode. In vivo hypoxia of the incised tissues was also evaluated immunohistochemically using a hypoxia marker, pimonidazole hydrochloride. To minimize intersubject variability, unincised contralateral tissues were used as a control. Tissue oxygen tension was decreased in both skeletal muscle and skin compared with control, for several days after incision. When measured directly, oxygen tension decreased immediately and remained low for several days after incisions. Pimonidazole immunostaining revealed hypoxic areas in incised muscle and skin for several days. By postoperative day 10, tissue oxygen tension recovered to that of control tissue. These results support the evidence that a hypoxic condition is present in deep tissue after incisions and that an ischemic-like mechanism may contribute to postoperative pain.

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