Inspired Helium for Ischemic Protection During Knee Replacement Surgery

The purpose of this study is to determine whether breathing in helium reduces indications of injury to the skeletal muscle seen in blood tests after knee replacement surgery. The ability to reduce the risk of skeletal muscle injury may help improve patient safety by providing protection to the area of the body having its blood supply interrupted during a particular surgery.

During hospitalization, beginning the day after surgery, additional tests will be added to the daily standard of care blood samples. When daily blood samples are not ordered as part of a study participants care after surgery, blood samples only for the study tests, may be done. Up to 60 study participants will be selected to be in one of two possible groups. After hospital discharge the study participants physical therapist will be contacted for copies of the notes and reports about the participants progress in physical therapy. This information will be used to evaluate if the different breathing gases have any impact on how quickly people recover after surgery.

This group will be treated as any other patient would. Their anesthesia will be conducted as per routine with a target Fraction of inspired oxygen concentration (FiO2) of 0.25. During the course of the operation a small muscle biopsy will be collected.

This group will be treated with a single dose of inspired 75/25 heliox (75% helium 25% oxygen) breathed continuously for 15 minutes prior to the inflation of the surgical tourniquet. During the course of the operation a small muscle biopsy will be collected.

This group will be treated as any other patient would. Their anesthesia will be conducted as per routine with a target FiO2 of 0.25, (25%oxygen / 75%nitrogen) the only exception being that they will not be treated with inspired heliox.

This group will be treated with a single dose of inspired 75/25 heliox (75% helium 25% oxygen) breathed continuously for 15 minutes over any convenient window prior to the inflation of the surgical tourniquet. This will be the only change in their clinical care. Their anesthesia will be conducted as per routine and as the anesthesia team sees fit with a target FiO2 of 0.25, the only exception being that they will receive 75/25 heliox prior to the inflation of the tourniquet.

Post-operative expression of serum markers of injury to the skeletal muscle after knee arthroplasty. The primary endpoint will be detection of a decrease in the peak increase of CK detectable in the blood. A 15% decrease will be considered clinically significant.

Changes in the time course of the peak level of expression of lactate dehydrogenase will be analyzed..

Changes in the time course of the peak level of expression of creatinine phosphokinase (CK) will be analyzed.

Inclusion Criteria: Scheduled for an elective total knee arthroplasty > 18 years of age Expected to require inhaled oxygen concentrations < 25% Able to provide informed consent Exclusion Criteria: Expected to require inhaled oxygen concentrations > 25% < 18 years of age Member of a defined vulnerable population (e.g. pregnant, mentally handicapped, prisoners, etc.).