title: Right atrial pressure as measure of ventricular constraint in newborn lambs.
abstract: Although the lungs and pericardium constrain the heart and limit cardiac output, no method exists to assess this constraint in sick newborns. We hypothesize that a useful estimate of ventricular constraint may be obtained by measuring right atrial pressure (P(RA)) in the newborn. To test this hypothesis, we measured P(RA), thoracic inferior vena caval pressure (P(IVC); saline-filled catheters), and ventricular constraint (pericardial pressure, P(PER); liquid-containing balloon) in 4-wk-old (neonatal, n = 12) and 3-day-old (newborn, n = 6) anesthetized lambs. The measurements were made while LV filling pressure was altered (0-20 mmHg) and while positive end-expiratory pressure (PEEP) was maintained at 2.5 or 15 cmH2O. In all of the lambs, a strong linear relationship (r) existed between P(RA) and P(PER) (P(RA) = 1.19 P(PER) + 0.0, r = 0.99) and between P(IVC) and P(PER) (P(IVC) = 1.24 P(PER) + 0.1, r = 0.99; PEEP of 2.5 cmH2O). Similar relationships were also observed with increased PEEP (P(RA) = 1.29 P(PER)-1.2, r = 0.98 and P(IVC) = 1.32 P(PER)-1.2, r = 0.97). Because P(RA) provides an accurate measure of ventricular constraint in the normal lamb, it may be a useful measure of ventricular constraint in the sick newborn.
authors.affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Reproduction and Development, Monash University, Monash Medical Centre, Clayton, Melbourne, Victoria 3168, Australia.
authors.forename: J C
authors.initials: JC
authors.lastname: Fauchère
authors.forename: A M
authors.initials: AM
authors.lastname: Walker
authors.forename: E M
authors.initials: EM
authors.lastname: Skuza
authors.forename: D A
authors.initials: DA
authors.lastname: Grant
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016280:Atrial Function, Right / Q000502:physiology*; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology*; D006328:Cardiac Catheterization / Q000295:instrumentation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008365:Manometry; D008955:Models, Cardiovascular; D010496:Pericardium / Q000502:physiology; D011175:Positive-Pressure Respiration; D012044:Regression Analysis; D012756:Sheep; D014682:Vena Cava, Inferior / Q000502:physiology; D016276:Ventricular Function / Q000502:physiology*