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Effect of positive pressure on venous return in volume-loaded cardiac surgical patients

Van Den Berg, PCM and Jansen, JRC and Pinsky, MR (2002) Effect of positive pressure on venous return in volume-loaded cardiac surgical patients. Journal of Applied Physiology, 92 (3). 1223 - 1231. ISSN 8750-7587

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Abstract

The hemodynamic effects of increases in airway pressure (Paw) are related in part to Paw-induced increases in right atrial pressure (Pra), the downstream pressure for venous return, thus decreasing the pressure gradient for venous return. However, numerous animal and clinical studies have shown that venous return is often sustained during ventilation with positive end-expiratory pressure (PEEP). Potentially, PEEP-induced diaphragmatic descent increases abdominal pressure (Pabd). We hypothesized that an increase in Paw induced by PEEP would minimally alter venous return because the associated increase in Pra would be partially offset by a concomitant increase in Pabd. Thus we studied the acute effects of graded increases of Paw on Pra, Pabd, and cardiac output by application of inspiratory-hold maneuvers in sedated and paralyzed humans. Forty-two patients were studied in the intensive care unit after coronary artery bypass surgery during hemodynamically stable, fluid-resuscitated conditions. Paw was progressively increased in steps of 2 to 4 cmH2O from 0 to 20 cmH2O in sequential 25-s inspiratory-hold maneuvers. Right ventricular (RV) cardiac output (COtd) and RV ejection fraction (EFrv) were measured at 5 s into the inspiratory-hold maneuver by the thermodilution technique. RV end-diastolic volume and stroke volume were calculated from EFrv and heart rate data, and Pra was measured from the pulmonary artery catheter. Pabd was estimated as bladder pressure. We found that, although increasing Paw progressively increased Pra, neither COtd nor RV end-diastolic volume changed. The ratio of change (Δ) in Paw to ΔPra was 0.32 ± 0.20. The ratio of ΔPra to ΔCOtd was 0.05 ± 00.15 1·min-1·mmHg-1. However, Pabd increased such that the ratio of ΔPra to ΔPabd was 0.73 ± 0.36, meaning that most of the increase in Pra was reflected in increases in Pabd. We conclude that, in hemodynamically stable fluid-resuscitated postoperative surgical patients, inspiratory-hold maneuvers with increases in Paw of up to 20 cmH2O have minimal effects on cardiac output, primarily because of an in-phase-associated pressurization of the abdominal compartment associated with compression of the liver and squeezing of the lungs.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Van Den Berg, PCM
Jansen, JRC
Pinsky, MRpinsky@pitt.eduPINSKY
Date: 1 January 2002
Date Type: Publication
Journal or Publication Title: Journal of Applied Physiology
Volume: 92
Number: 3
Page Range: 1223 - 1231
DOI or Unique Handle: 10.1152/japplphysiol.00487.2001
Schools and Programs: School of Medicine > Critical Care Medicine
Refereed: Yes
ISSN: 8750-7587
PubMed ID: 11842062
Date Deposited: 22 Mar 2012 20:29
Last Modified: 19 Aug 2019 13:55
URI: http://d-scholarship.pitt.edu/id/eprint/11476

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