Stewart's theory and acid-base changes induced by crystalloid infusion in humans: a randomized physiological trial.

Background: Stewart's acid-base theory states that, under isocapnic conditions, crystalloid infusion affects plasma pH due to changes in strong ion difference and total weak acid concentration: a comprehensive study also assessing renal response and hemodilution effects has not been conducted in humans. We aimed to evaluate Stewart's approach during crystalloid infusion in humans.

Methods: In this randomized trial, patients undergoing surgery with minimal blood losses were randomized to receive to normal saline (chloride content 154 mEq/L, strong ion difference 0 mEq/L), lactated Ringer's (chloride content 112 mEq/L, strong ion difference 29 mEq/L) or Crystalsol (chloride content 98 mEq/L, strong ion difference 50 mEq/L): patients received 10 ml/kg immediately after intubation, and 20 ml/kg after 2 h.

The Effect of Positive End-Expiratory Pressure on Pulmonary Vascular Resistance Depends on Lung Recruitability in Patients with Acute Respiratory Distress Syndrome.

A U-shaped relationship should exist between lung volume and pulmonary vascular resistance (PVR), with minimal PVR at FRC. Thus, positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS) should increase PVR if it induces significant lung distension compared with recruitment. However, this has never been proved in patients.