title: Pharmacodynamic Analysis of a Fluid Challenge.
abstract: OBJECTIVE
  This study aims to describe the pharmacodynamics of a fluid challenge over a 10-minute period in postoperative patients.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  General and cardiothoracic ICU, tertiary hospital.
  
  
  METHODS
  Twenty-six postoperative patients.
  
  
  METHODS
  Two hundred and fifty-milliliter fluid challenge performed over 5 minutes. Data were recorded over 10 minutes after the end of fluid infusion
  
  
  RESULTS
  Cardiac output was measured with a calibrated LiDCOplus (LiDCO, Cambridge, United Kingdom) and Navigator (Applied Physiology, Sydney, Australia) to obtain the Pmsf analogue (Pmsa). Pharmacodynamics outcomes were modeled using a Bayesian inferential approach and Markov chain Monte Carlo estimation methods. Parameter estimates were summarized as the means of their posterior distributions, and their uncertainty was assessed by the 95% credible intervals. Bayesian probabilities for groups' effect were also derived. The predicted maximal effect on cardiac output was observed at 1.2 minutes (95% credible interval, -0.6 to 2.8 min) in responders. The probability that the estimated area under the curve of central venous pressure was smaller in nonresponders was 0.12. (estimated difference, -4.91 mm Hg·min [95% credible interval, -13.45 to 3.3 mm Hg min]). After 10 minutes, there is no evidence of a difference between groups for any hemodynamic variable.
  
  
  CONCLUSIONS
  The maximal change in cardiac output should be assessed 1 minute after the end of the fluid infusion. The global effect of the fluid challenge on central venous pressure is greater in nonresponders, but not the change observed 10 minutes after the fluid infusion. The effect of a fluid challenge on hemodynamics is dissipated in 10 minutes similarly in both groups.
authors.affiliation: 1General and Cardiothoracic Intensive Care unit, Adult Critical Care Directorate, St George's University Hospitals and St George's University of London, NHS Foundation Trust, London, United Kingdom. 2Institute of Infection and Immunity, St George's University of London, NHS Foundation Trust, London, United Kingdom.
authors.forename: Hollmann D
authors.initials: HD
authors.lastname: Aya
authors.forename: Irina Chis
authors.initials: IC
authors.lastname: Ster
authors.forename: Nick
authors.initials: N
authors.lastname: Fletcher
authors.forename: R Michael
authors.initials: RM
authors.lastname: Grounds
authors.forename: Andrew
authors.initials: A
authors.lastname: Rhodes
authors.forename: Maurizio
authors.initials: M
authors.lastname: Cecconi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001499:Bayes Theorem; D002496:Central Venous Pressure / Q000502:physiology*; D005260:Female; D005440:Fluid Therapy; D006439:Hemodynamics; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D011182:Postoperative Care / Q000379:methods*; D011446:Prospective Studies; D062606:Tertiary Care Centers; D013997:Time Factors