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Effects of Animal Positioning on Catecholamine and Vasopressin Levels in Pigs Undergoing Laparoscopy

Background: The aim of this study was to determine the influence of different therapeutic interventions and positions on catecholamine and vasopressin levels in the pneumoperitoneum (PN) in a porcine model. Methods: In 43 pigs, a 14-mm-Hg PN was established and plasma concentrations of epinephrine, norepinephrine and vasopressin were measured in head-up, supine and head-down positions. Additionally, the effects of the following changes were studied: (1) increase in intrathoracic blood volume (ITBV) by means of hydroxyethyl starch infusion; (2) vasodilatation induced by sodium nitroprusside, or (3) selective sympathicolysis induced by esmolol. Again, catecholamines (ELISA) and vasopressin (RIA) were determined. Results: After PN, epinephrine levels did not significantly increase in the head-up position (p = 0.075) and remained also unchanged in the supine or head-down position. Plasma norepinephrine statistically significantly decreased in the head-up position (p = 0.046). Vasopressin concentrations remained unaltered. After increased ITBV, neither catecholamine nor vasopressin concentrations changed in any body position. Application of sodium nitroprusside or esmolol caused no changes. Conclusion: Changes in endogenous catecholamine levels safely prevent cardiocirculatory instability in small pigs. Volume substitution might reduce endocrine responses to PN in the head-up position.