Relationship between Adrenomedullin and Vasopressin-Aquaporin System under General Anesthesia

Aim: The roles of adrenomedullin (AM) in body fluid balance under general anesthesia were investigated. Methods: Time course changes in plasma osmolality, AM, arginine vasopressin (AVP), and urinary aquaporin 2 (AQP2) in 17 patients undergoing abdominal surgery under general anesthesia were examined. Results: Increases in plasma AM levels were observed in parallel with increases in the levels of urinary AQP2/creatinine (Cr) before induction and 90 and 180 min after initiation of anesthesia. Significant correlations between plasma AM and urinary AQP2/Cr (r = 0.62, p < 0.0001) as well as urinary AVP/Cr and AQP2/Cr (r = 0.60, p < 0.0001) were uncovered. Multivariate stepwise analysis identified plasma AM as the critical independent factor affecting urinary AQP2/Cr level. Conclusion: A novel correlation of AM and AQP2 which overlays an AVP-AQP2 system may play a key role in fluid homeostasis during general anesthesia.