Effect of Diaphragm Stimulation During Surgery

Study Overview
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Brief Summary
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During major surgical procedures general anesthesia is used to make the patient unconscious. General anesthesia insures that the patient is unaware of any pain caused by surgery. General anesthesia also prevents the patient from moving to prevent any potential surgical error. At the same time general anesthesia makes it impossible for the patient to breathe. To help the patient breathe a breathing tube is placed into the patient's airway and connected to the mechanical ventilator. A mechanical ventilator is an artificial breathing pump, which delivers gas into a patient's airways. The purpose of this research study is to determine if brief periods of diaphragm stimulation can prevent diaphragm problems caused by the use of mechanical ventilators and surgery. To answer this question the changes in the genes responsible for maintaining diaphragm function will be studied. A gene is the code present in each cell in your body and controls the behavior of that cell. In addition, the changes in the contractile properties of muscle fibers will be studied. The results from this study may help develop new treatments to prevent diaphragm weakness resulting from mechanical ventilation use.

Detailed Description
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Although mechanical ventilation (MV) is life-sustaining, it comes with a cost. MV dramatically reduces diaphragm contractility, induces ventilator-induced diaphragm dysfunction (VIDD) and sometimes leads to weaning failure. VIDD includes reduced mitochondrial respiration and increased oxidative stress, muscle fiber damage and decreased diaphragm force production. In animal models, intermittent diaphragm contraction during MV support attenuates VIDD. However, there are only limited data addressing this problem in humans. Here, the study team propose to directly test the hypothesis that intermittent electrical stimulation (ES) of the human hemidiaphragm during prolonged cardiac surgeries with MV support prevents/attenuates VIDD in the active hemidiaphragm. Mitochondrial function is central to energy metabolism and skeletal muscle function in a chronically active muscle, such as the diaphragm. Although abnormal mitochondrial function is thought to precipitate VIDD in animal models, limited data are available concerning mitochondrial contributions to VIDD in humans. Of even greater importance, there are no interventions available to attenuate these defects in humans. Here, the study team will test the impact of an innovative experimental treatment, intermittent electrical stimulation (ES) of the hemidiaphragm during prolonged surgeries with MV, on mitochondrial function, single fiber contractile properties and catabolic muscle pathways in human diaphragm. Using a within-subjects experimental design, muscle samples from a stimulated hemidiaphragms will be compared with samples from the unstimulated hemidiaphragm. The study team will investigate mitochondrial dysfunction and oxidative stress during prolonged CTS/MV, and the potential of ES to attenuate or prevent VIDD. Next, the study team will investigate the effects of ES on single fiber contractile properties and Titin integrity. Finally, the study team will study the effect of ES on proteolytic pathways (caspase, calpain and ubiquitin-proteasome) and ribosomal RNA markers of decreased protein synthesis implicated in VIDD.

Official Title
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The Effect of Intermittent Hemidiaphragm Stimulation During Surgery on Mitochondrial Function, Single Fiber Contractile Force and Catabolic Pathways in Humans

Conditions
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Mechanical Ventilation Complication, Diaphragm Injury

Intervention / Treatment
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* Other: Electrical stimulation of hemidiaphragm


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients undergoing complex, elective prolonged surgeries, usually lasting 5-8 hours or longer, including lung transplants (e.g. valveoplasty, coronary artery bypass and/or aortic repairs) Exclusion Criteria: history of prior surgery to the diaphragm or pleura; a diagnosis of COPD will be determined from a clinical history consistent with chronic bronchitis and/or emphysema, a long history of cigarette smoking, and pulmonary function tests consistent with irreversible airflow obstruction (FEV1 < 40% predicted, according to European Respiratory Society criteria [will not apply to transplant patients] a diagnosis of chronic heart failure (NYHA class IV) clinical diagnosis of other lung disease (cystic fibrosis, bronchiectasis, lung cancer; etc.) [will not apply to transplant patients] renal insufficiency (serum creatinine > 1.6 mg/dl); severe hepatic disease (any liver function tests > 1.5 times the upper limit of normal); undernourishment (body mass index < 20 kg/m2), chronic uncontrolled or poorly controlled metabolic diseases (e.g., diabetes, hypo- or hyperthyroidism) orthopedic diseases, suspected paraneoplastic or myopathic syndromes, if in the surgeons' judgment the patients' clinical status warrants, diaphragm stimulation will be stopped and biopsies will not be obtained,

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: This is a within subjects design. One side of each subject's diaphragm will be stimulated. The other side of the subject's diaphragm will not be stimulated and will therefore serve as the control. Biopsies will be taken from both sides and compared.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Stimulation<br>Electrical stimulation of hemidiaphragm | Other: Electrical stimulation of hemidiaphragm<br>* Electrical impulses<br>|
| No Intervention: Control<br>No stimulation of hemidiaphragm | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mitochondrial respiration | High-resolution respirometry will be used to assess mitochondrial respiration. It will be quantified as pmol oxygen/sec/mg wet weight. | Up to eight hours | 
| Mitochondrial reactive oxygen species production | Mitochondrial reactive oxygen species (ROS) production will be assessed using an in situ approach to measure hydrogen peroxide production in permeabilized diaphragm skeletal muscle fiber bundles. It will be quantified as pmol/min/mg dry weight. | Up to eight hours | 
| Mitochondrial DNA mutation frequency | Long-Amplicon quantitative PCR will be used to measure the frequency of mitochondrial DNA mutations. It will be quantified as number of lesions/10 kilobases. | Up to eight hours | 
| Nuclear DNA mutation frequency | Long-Amplicon quantitative PCR will be used to measure the frequency of nuclear DNA mutations. It will be quantified as number of lesions/10 kilobases. | Up to eight hours | 
| Aconitase activity | In order to evaluate mitochondrial damage, actonitase activity will be measured spectrophotometrically. It will be quantified as units/mg protein. | Up to eight hours | 
| Lipid peroxidation | Lipid peroxidation will be assessed by measuring 4-hydroxy-2-nonenal-modified proteins. It will be quantified as arbitrary optical density units. | Up to eight hours | 
| Citrate cynthase activity | Changes in electron transport chain will be assessed by measuring citrate cynthase activity. It will be quantifed as nmol/mg protein/min. | Up to eight hours | 
| Cytochrome c oxidase (COX) activity | Changes in electron transport chain will be assessed by measuring cytochrome c oxidase (COX) activity. It will be quantifed as Units/mcg protein. | Up to eight hours | 
| Single diaphragm fiber, specific force | Single diaphragm fiber mechanical force properties will be measured. Specific force is quantified as kN/m^2. | Up to eight hours | 
| Single diaphragm fiber, rate of tension redevelopment | Single diaphragm fiber mechanical force properties will be measured. The rate of tension redevelopment is quantified as s^(-1). | Up to eight hours | 
| Single diaphragm fiber, maximum shortening velocity | Single diaphragm fiber mechanical force properties will be measured. The maximum shortening velocity is quantified as mm/s.. | Up to eight hours | 
| Titin size | Titin integrity will be assessed. A relative titin size will be quantified in nm. | Up to eight hours | 
| Total titin to myosin heavy chain ratio | Titin integrity will be assessed. The total titin to myosin heavy chain ratio will be presented as a unitless value. | Up to eight hours | 
| Titin exon composition | The composition of titin exons will be assessed and quantified via real-time polymerase chain reaction (qPCR). It will be presented as percent change in expression. as a percent change in expression. | Up to eight hours | 
| Titin binding proteins | Titin binding proteins will be assessed and quantified via real-time polymerase chain reaction (qPCR). It will be presented as percent change in expression. | Up to eight hours | 
| Calpain 1 | Calpain 1 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Calpain 2 | Calpain 2 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Calpain 3 | Calpain 3 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Caspase-3 | Caspase-3 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Caspase-9 | Caspase-9 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| 20S proteasome | 20S proteasome will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| 26S proteasome | 26S proteasome will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| MurF1 | MurF1 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Atrogin 1 | Atrogin 1 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| Foxo-3 | Foxo-3 will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| 28SrRNA | 28SrRNA will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| 18SrRNA | 18SrRNA will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 
| 45S pre-rRNA | 45S pre-rRNA will be measured with Western Blot anaylsis and will be presented as percent difference in expression. | Up to eight hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Mechanical ventilation, Diaphragm weakness, Difficulty weaning from mechanical ventilation, Diaphragm stimulation