Comparison of Compensatory Reserve Index to Changes in Stroke Volume and Intravascular Volume
Condition: Hemorrhage
MeSH terms: Hemorrhage
Study type: Observational

Summary: 
      The purpose of this study is to demonstrate the correlation of the Compensatory Reserve Index
      (CRI) numeric and graphical trend readings to intravascular volume changes as compared to
      graded blood loss (removal of 20% of estimated total blood volume in ~333 mL aliquots) and to
      stroke volume as measured by the Nexfin monitor during the same graded blood removal period.
      Enrollment includes both men and women.
    

Detailed description: 
      Sequential Blood Loss: Blood loss will be simulated by withdrawal of 20% of estimated total
      blood volume. Estimated total blood volume for men = 75 mL/kg and for women = 65 mL/kg. The
      calculated target withdrawal volume is also consistent with an allowable estimated blood loss
      equation assuming a starting hematocrit (hct) of approximately 45% in males and 40% in
      females, where the expected drop in hct for this volume withdrawn is 7 percentage points in
      males and 6 percentage points in females. An actual drop in hct may not be observed in this
      study due to the relatively expedient removal of blood and no simultaneous administration of
      fluids (i.e., no "hemodilution" with crystalloid). Blood will be removed in aliquots up to
      ~333 mL. For safety, men will have no more than 4 units of blood removed (1,333 mL) and women
      will have no more than 3 units of blood removed (1,000 mL).

      The blood will be withdrawn via the venous catheter and we anticipate that it will take 15-20
      min for each stage of blood withdrawal to occur. A total of 3 aliquots will be withdrawn over
      approximately sixty minutes in women and 4 aliquots withdrawn over 80 minutes in men. The
      blood will be stored using preservatives and anticoagulation procedures similar to those used
      for perioperative hemodilution and/or intraoperative cell saver. The blood will remain in the
      study room until it is re-infused. We will use standard "auto-transfusion" blood collection
      equipment identical to that used in the ORs for perioperative hemodilution techniques. The
      blood will be drained by gravity from an indwelling vascular catheter into anti-coagulant
      preservative solution using tubing and bags systems provided by the autologous transfusion
      team that we routinely work with in the ORs. For the first several studies we will schedule
      them at a time when auto-transfusion OR personnel can be present and after that the
      anesthesiologists will be directly involved in drawing the blood, subsequent handling and
      reinfusion. The blood will never leave the autologous transfusion bag and a closed system
      will be used. The blood will be held at room temp with gentle agitation for ~60-80 minutes
      and then re-infused over 60-80 minutes via a large bore IV; monitoring will continue during
      reinfusion. Following completion of the reinfusion subjects will de-instrumented and observed
      in the physiology lab for two hours.
    

Intervention name(s): Pulse Oximeter
Intervention type(s): Device
Intervention description(s): Blood removal and reintroduction as measured by the plethysmograph of a pulse oximeter
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Twenty healthy volunteers between the ages of 18 and 55, men and women, American Society of
        Anesthesiology "class 1" health status.