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CRITICAL CARE AND TRAUMA

The Role of Thoracic Epidural Analgesia in Receptor-Dependent and Receptor-Independent Pulmonary Vasoconstriction in Experimental Pancreatitis

Stefan Lauer, MD^*, Hendrik Freise, MD^*, Lars G. Fischer, MD^*, Kai Singbartl, MD^*, Hugo V. Aken, MD, FRCA, FANZCA^*, Markus M. Lerch, MD, and Andreas W. Sielenkämper, MD, MSc^*

From the *Department of Anesthesiology and Intensive Care Medicine, University Hospital Muenster, Germany; and Department of Gastroenterology, Endocrinology and Nutrition, Ernst-Moritz-Arndt Universität, Greifswald, Germany.

BACKGROUND: Acute pancreatitis commonly results in lung injury and deterioration of pulmonary endothelial function and vasoregulation. Despite a variety of potential risks with the use of thoracic epidural analgesia (TEA) in the critically ill, this technique is an important component of pain management in pancreatitis in selected cases. Although there is evidence that epidural analgesia improves lung function through effective pain relief, the influence of continuously applied epidural local anesthetics on pulmonary endothelial dysfunction is still unknown.

METHODS: In an in vivo model of TEA in awake rats with acute pancreatitis, we evaluated blood gas analysis, arterial blood pressure, and exhaled nitric oxide. This was followed by in vitro studies of receptor-dependent and receptor-independent pulmonary vasoconstriction using an isolated perfused lung model. Pulmonary myeloperoxidase activity, indicating leukocyte sequestration into the lungs and wet/dry ratio evaluating pulmonary edema, were also measured.

RESULTS: Deteriorated oxygenation, metabolic and lactate acidosis, as well as exhaled nitric oxide levels occurring during acute pancreatitis, were reduced by TEA to levels observed in sham-operated animals. TEA also partially ameliorated the hypotension occurring in pancreatitis. In isolated perfused lungs, receptor-dependent vasoconstriction due to angiotensin II was reduced during acute pancreatitis, indicating pulmonary vascular smooth muscle cell dysfunction. Hypoxic pulmonary vasoconstriction was likewise abolished. Treatment with TEA partly restored the vasoreactivity to angiotensin II and hypoxia. Bradykinin-induced vasoconstriction, indicating pulmonary endothelial dysfunction, myeloperoxidase activity and the degree of pulmonary edema, was not influenced by TEA.

CONCLUSIONS: Our study demonstrated that TEA improves pancreatitis-associated impairment of pulmonary vasoreactivity and gas exchange.