Pain Medicine  |   October 2018
Effect of Thoracic Epidural Anesthesia in a Rat Model of Phrenic Motor Inhibition after Upper Abdominal Surgery
Author Notes
  • From the Departments of Anesthesia (W-S.C., S.C., D.S., T.J.B., S.K.), Neurology (G.B.R.), Molecular Physiology and Biophysics (G.B.R.), and Pharmacology (T.J.B.), Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa.
  • Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).
    Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).×
  • Submitted for publication January 4, 2018. Accepted for publication May 24, 2018.
    Submitted for publication January 4, 2018. Accepted for publication May 24, 2018.×
  • Address correspondence to Dr. Kang: Department of Anesthesia, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, Iowa 52242. sinyoung-kang@uiowa.edu. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Pain Medicine / Basic Science / Central and Peripheral Nervous Systems / Pain Medicine / Pharmacology / Regional Anesthesia / Respiratory System
Pain Medicine   |   October 2018
Effect of Thoracic Epidural Anesthesia in a Rat Model of Phrenic Motor Inhibition after Upper Abdominal Surgery
Anesthesiology 10 2018, Vol.129, 791-807. doi:10.1097/ALN.0000000000002331
Anesthesiology 10 2018, Vol.129, 791-807. doi:10.1097/ALN.0000000000002331
Abstract

Editor’s Perspective:

What We Already Know about This Topic:

  • Diaphragmatic dysfunction is common after upper abdominal surgery

  • Injury-induced reflex inhibition of phrenic motor neuron drive may support diaphragmatic dysfunction

What This Article Tells Us That Is New:

  • Upper abdominal incision in rats reduced phrenic motor output for several days after surgery

  • Thoracic epidural anesthesia using bupivacaine reduced incision-induced alterations in phrenic motor output

Background: One important example of impaired motor function after surgery is diaphragmatic dysfunction after upper abdominal surgery. In this study, the authors directly recorded efferent phrenic nerve activity and determined the effect of the upper abdominal incision. The authors hypothesized that phrenic motor output would be decreased after the upper abdominal incision; it was also hypothesized that blocking sensory input from the incision using thoracic epidural anesthesia would diminish this incision-induced change in phrenic motor activity.

Methods: Efferent phrenic activity was recorded 1 h to 10 days after upper abdominal incision in urethane-anesthetized rats. Ventilatory parameters were measured in unanesthetized rats using whole-body plethysmography at multiple time points after incision. The authors then determined the effect of thoracic epidural anesthesia on phrenic nerve activity and ventilatory parameters after incision.

Results: Phrenic motor output remained reduced by approximately 40% 1 h and 1 day after incision, but was not different from the sham group by postoperative day 10. One day after incision (n = 9), compared to sham-operated animals (n = 7), there was a significant decrease in spike frequency area-under-the-curve (median [interquartile range]: 54.0 [48.7 to 84.4] vs. 97.8 [88.7 to 130.3]; P = 0.0184), central respiratory rate (0.71 [0.63 to 0.79] vs. 0.86 [0.82 to 0.93]/s; P = 0.0460), and inspiratory-to-expiratory duration ratio (0.46 [0.44 to 0.55] vs. 0.78 [0.72 to 0.93]; P = 0.0023). Unlike humans, a decrease, not an increase, in breathing frequency has been observed after the abdominal incision in whole-body plethysmography. Thoracic epidural anesthesia attenuated the incision-induced changes in phrenic motor output and ventilatory parameters.

Conclusions: Upper abdominal incision decreased phrenic motor output and ventilatory parameters, and this incision-induced impairment was attenuated by thoracic epidural anesthesia. The authors’ results provide direct evidence that afferent inputs from the upper abdominal incision induce reflex inhibition of phrenic motor activity.