Effect of hypotensive hypovolemia and thoracic epidural anesthesia on plasma pro-atrial natriuretic peptide to indicate deviations in central blood volume in pigs: a blinded, randomized controlled trial
Received 8 February 2019
Accepted for publication 16 May 2019
Published 25 June 2019 Volume 2019:12 Pages 47—55
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Amy Norman
Peer reviewer comments 2
Editor who approved publication: Dr Stefan Wirz
Rune B Strandby,1 Rikard Ambrus,1 Michael P Achiam,1 Amalie Henriksen,1 Jens P Goetze,2 Niels H Secher,3 Lars B Svendsen1
1Department of Surgical Gastroenterology; 2Department of Clinical Biochemistry; 3Department of Anesthesiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
Purpose: Changes in plasma pro-atrial natriuretic peptide (proANP) may indicate deviations in the central blood volume (CBV). We evaluated the plasma proANP response to hypotensive hypovolemia under the influence of thoracic epidural anesthesia (TEA) in pigs. We hypothesized that plasma proANP would decrease in response to hypotensive hypovolemia and that TEA would aggravate the proANP response, reflecting a further decrease in CBV.
Design: Randomized, blinded, controlled trial.
Setting: A university-affiliated experimental facility.
Participants: Twenty pigs randomized to administration of saline (placebo) or bupivacaine with morphine (TEA) in the epidural space at Th8-Th10.
Interventions: Relative hypovolemia was established by an inflatable Foley catheter positioned in the inferior caval vein just below the heart (caval obstruction), and hemorrhage-induced hypovolemia was by withdrawal of blood from the femoral artery, both aiming at a mean arterial pressure (MAP) of 50–60 mmHg. Hemodynamic variables and plasma proANP were determined before and after the interventions.
Results: Caval obstruction and withdrawal of blood reduced MAP to 50–60 mmHg. Accordingly, cardiac output, central venous pressure, and mixed venous oxygen saturation decreased (p<0.05). Yet, plasma proANP was stable after both caval obstruction (TEA: 72 [63–78] to 80 pmol/L [72–85], p=0.09 and placebo: 64 [58–76] to 69 pmol/L [57–81], p=0.06) and withdrawal of blood (TEA: 74 [73–83] to 79 pmol/L [77–87], p=0.07 and placebo: 64 [56–77] to 67 pmol/L [58–78], p=0.15).
Conclusion: Plasma proANP was stable in response to relative and hemorrhage-induced hypovolemia to a MAP of 50–60 mmHg, and the response was independent of TEA. The findings suggest that alterations in plasma proANP do not follow deviations in CBV during hypotensive hypovolemia in pigs.
Keywords: atrial natriuretic factor, hemorrhage, hypovolemia, epidural anesthesia, pigs, hypotension
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