Is Pleth Variability Index (PVI) a Surrogate for Pulse Pressure Variations (PPV) in Pediatric Spine Fusion (SF) Surgery?
Condition: Scoliosis; Spinal Fusion
MeSH terms: Scoliosis
Study type: Observational

Summary: 
      Spine fusion is an involved procedure during which patients are at risk for significant
      intra-operative blood loss.This study will compare 2 ways of determining fluid status and
      response to fluid administration. One way is to measure the changes in the arterial wave form
      from the special IV that is usually placed in an artery (PPV). The second way is to use a
      non-invasive method of a finger probe that measures changes in the plethysmogram or the pleth
      variability index (PVI). No actual patient treatments will be based on these values during
      surgery.
    

Detailed description: 
      Spine fusion is an involved procedure during which patients are at risk for significant
      intra-operative blood loss. The resulting hypovolemia increases the fluctuations in arterial
      pressure associated with positive pressure ventilation. These respiratory induced arterial
      pressure variations (RIAPV) appear as cyclical peaks and troughs on the arterial waveform.

      Different approaches have been used to quantify the RIAPV. One such approach has been to
      measure the pulse pressure variation (PPV), using invasive arterial monitoring. In previous
      studies, PPV has been shown to be a good indicator of fluid responsiveness intra-operatively,
      but this has not been specifically evaluated in patients undergoing spine fusion. This
      patient population is of particular interest because of their underlying scoliosis as well as
      their prone position during the operation. These two variables could potentially alter
      lung-thorax mechanics in a manner which may influence RIAPV, which is specifically determined
      by the interaction between intrathoracic pressure and venous filling of the heart. A second
      approach to quantifying RIAPV relies on non invasive technology initially developed by the
      Masimo Corporation for pulse oximetry. This parameter has been coined pleth variability index
      (PVI), as it specifically quantifies real time changes in the plethysmogram associated with
      respiration. PVI, which is based on arterial blood volume changes, is therefore analogous to
      PPV, which is derived from changes in arterial pressure. To date PVI has only been evaluated
      in adult patients undergoing cardiac surgery and the data suggest that it may be a useful
      indicator of fluid responsiveness.

      Given the non-invasive and continuous nature of PVI, it is appealing for potential use as a
      bedside monitor to guide fluid resuscitation. However, photoplethysmography is known to be
      sensitive to noise due to motion, light and electrical interference. Furthermore, PVI is
      based upon a degree of quantitative evaluation of the photoplethysmogram that is the first of
      its kind. For these reasons, it is important to understand the limits of agreement between
      PVI and PPV before we can accept PVI as a non-invasive surrogate measurement. This study
      intends to evaluate PVI by analyzing it in relation to PPV. More specifically, paired
      measurements of PPV and PVI will be compared to determine the limits of agreement between the
      two parameters in patients undergoing spinal fusion.
    

Intervention name(s): Masimo multi-wavelength pulse co-oximeter
Intervention type(s): Device
Intervention description(s): Subjects will have a finger probe that will measure the pleth variability index. They will also have an arterial line (as standard of care) from which arterial pulse tracings will be obtained.
Other intervention name(s): Masimo Rainbow Set; pulse co-oximeter
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Subjects will be selected from those having posterior spinal fusion surgery at The
        Children's Hospital of Philadelphia.
      
Keywords: invasive procedures; hypovolemia