Hemodynamic Responses During Induction: Comparison of Marsh and Schnider Pharmacokinetic Models
Condition: Healthy
Study type: Interventional

Summary: 
      To compare the hemodynamic changes during anesthesia induction between Marsh and Schnider
      plasma TCI models. We put forward a hypothesis that, if one TCI model is associated with much
      more prominent vasodilation effect or cardiac depression, a more sharp decrease in mean
      arterial pressure, systemic vascular resistance , central venous return or stroke volume
      would be observed.
    

Detailed description: 
      Current systems of propofol TCI are pre-programmed with the Marsh and Schnider
      pharmacokinetic models. Rate constants of Marsh are fixed, whereas compartment volumes and
      clearances are weight proportional. Schnider model has fixed values for VC, V3, k13, and k31,
      adjusts V2, k12, and k21 for age, and adjusts k10 according to total weight, lean body mass
      (LBM), and height. One major beneﬁt of the Schnider model is that it adjusts doses and
      infusion rates according to patient age. This provides a strong argument for using the
      Schnider model in the elderly and unwell patients which may improve hemodynamic stability and
      safety.

      However for the vast majority of young and middle age patients, whether Marsh or Schnider
      would be a better choice for hemodynamic stability remains unknown.

      With marsh model, as VC is scaled to body weight, the amount of drug delivered is dependent
      of body weight. In the Schnider model, as VC at 4.27L is independent of body weight, VC in
      terms of ml/kg decreases as body weight increases. This and the influence of height and
      weight on clearance results in heavier patients receiving less propofol on a mg/kg basis
      whereas those with a lower lean body mass will initially receive about 30% less than
      delivered by Marsh, but after 30 min, the Schnider model delivers about 15% more. Besides,
      when Schnider model is used in the morbidly obese, the LBM equation can generate paradoxical
      values resulting in excessive increases in maintenance infusion rates. Nevertheless, the
      purpose of this study was to investigate the vast majority of Asian patients whose body
      weight were in normal range. Only patients with BMI between 18 and 29 were included to
      minimize the influential factor of body weight in TCI system.

      To compare the hemodynamic changes during anesthesia induction between Marsh and Schnider
      plasma TCI models. We put forward a hypothesis that, if one TCI model is associated with much
      more prominent vasodilation effect or cardiac depression, a more sharp decrease in mean
      arterial pressure, systemic vascular resistance , central venous return or stroke volume
      would be observed.
    

Intervention name(s): Marsh Plasma TCI with high initial target; Schnider Plasma TCI with high initial target
Intervention type(s): Procedure; Procedure
Intervention description(s): plasma target-controlled infusion in Marsh model(n=30) with an initial target concentration of 4 μg/ml. Target was then reset and gradually titrated to a sedation level with narcotrend index below 64.; plasma target-controlled infusion in Schnider model(n=30) with an initial target concentration of 4 μg/ml. Target was then reset and gradually titrated to a sedation level with narcotrend index below 64.
Other intervention name(s): Plasma target-controlled infusion in Marsh model; Plasma target-controlled infusion in Schnider model
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Diagnostic
Keywords: Target control infusion; propofol; cardiac depression; induction of anesthesia; hemodynamics