Sympathetic and sensory nerve activation during negative pressure therapy of sternotomy wounds☆

Christian Torbrand 0 3 Angelica Wackenfors 0 3 Sandra Lindstedt 0 2 Rolf Ekman 0 1 Richard Ingemansson 0 2 Malin Malmsjo 0 3 0 This study was supported by the Anders Otto Sward FoundationyUlrika Eklund Foundation, Anna Lisa and Sven Eric Lundgren's Foundation for Medical Research, the Ake Wiberg Foundation, the M. Bergvall Foundation, the Swedish Medical Association, the Royal Physiographic Society in Lund, the Swedish Medical Research Council, the Crafoord Foundation, the Swedish Heart-Lung Foundation, the Swedish Government Grant for Clinical Research and the Swedish Hypertension Society 1 Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg , Molndal, Sweden 2 Department of Cardiothoracic Surgery, Lund University Hospital , Lund, Sweden 3 Department of Medicine, Lund University Hospital , Lund, Sweden Negative pressure wound therapy (NPWT) has been adopted as the first-line treatment for poststernotomy mediastinitis as a result of the excellent clinical outcome. The knowledge concerning the effects of NPWT on the cardiovascular system and homeostasis is still limited. The aim of the present study was to investigate whether the plasma levels of neurohormones change during NPWT. Six pigs underwent median sternotomy followed by NPWT at -125 mmHg. The plasma levels of noradrenaline, adrenaline, neuropeptide Y, substance P, vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP) were determined before (0 min) and 5, 20, 60 and 180 min after the application of NPWT. The results show a transient increase in the plasma levels of noradrenaline and adrenaline when NPWT was applied. The plasma level of the adrenergic co-transmitter neuropeptide Y was higher in NPWT - than in sham-treated pigs, after 180 min of negative pressure. After 180 min of NPWT there was an increase in the plasma levels of the sensory nerve transmitter substance P, while no such effect was observed for CGRP or VIP. In conclusion, the results suggest sympathetic nerve activation during NPWT. This may be the result of an increase in workload on the heart during the initial phase of NPWT. 2008 Published by European Association for Cardio-Thoracic Surgery. All rights reserved. 1. Introduction Negative pressure wound therapy (NPWT) has remarkable effects on the healing of chronic and difficult wounds and has drastically reduced the mortality in poststernotomy mediastinitis following cardiac surgery. The technique entails application of negative pressure to a sealed, airtight wound. The suction force created by the subatmospheric pressure enables the drainage of excessive fluid and debris, which leads to the removal of wound edema, reduction in bacterial count and enhanced granulation tissue formation w1, 2x. Knowledge of the effects of NPWT in a sternotomy wound is limited w1x. The organs in the mediastinum are hemodynamically crucial and both vulnerable bypass grafts and reduced cardiac function should be taken into consideration during NPWT of sternotomy wounds. Recent publications have reported right ventricular rupture during NPWT in cardiac surgery w3x. Also, reduced cardiac output during NPWT has been reported w4x. No study has yet been performed to examine the effect of NPWT on neurohormones, many of which are considered to be released upon increased cardiac load. In the present study, we analyzed the plasma levels of noradrenaline, adrenaline, neuropeptide Y, substance P, vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP). Noradrenaline is a transmitter that is released by the sympathetic nerve terminals. The sympathetic nervous system also acts on the adrenal medulla to release catecholamines including adrenaline and, to a lesser extent, noradrenaline. Neuropeptide Y is co-localized with norepinephrine in sympathetic nerve terminals and is released when the rate of nerve firing is high w5x. Neuropeptide Y enhances the effects of noradrenaline and accounts for the long-lasting effects of sympathetic nerve transmission w5x. Sympathetic nerve activation results in increased cardiac pumping, sodium retention via the kidneys and constriction and hypertrophic effects on the peripheral vasculature. VIP is a co-transmitter in parasympathetic nerves w6x. It is involved in the autonomic regulation of the cardiovascular system, where it exerts positive inotropic and chronotropic effects, and causes coronary vasodilatation. Substance P and CGRP are released from primary afferent neurons and act in the periphery to stimulate vasodilatation and promote inflammation w7x. This mechanism, known as neurogenic inflammation, amplifies and sustains an inflammatory reaction. In the present study, the effects of NPWT on the plasma levels of neurohormones were examined in a pig sternotomy wound model. Noradrenaline, adrenaline, neuropeptide Y, VIP, substance P and CGRP were analysed before (0 min) and after 5, 20, 60 a (...truncated)