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Trial record 44 of 287 for:    Cerebral Hypoxia

Study of Methemoglobin as a Biomarker of Tissue Hypoxia During Acute Hemodilution in Heart Surgery Patients

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ClinicalTrials.gov Identifier: NCT01883713
Recruitment Status : Completed
First Posted : June 21, 2013
Last Update Posted : April 17, 2018
Sponsor:
Information provided by (Responsible Party):
St. Michael's Hospital, Toronto

Brief Summary:

Acute and chronic anemia continue to be associated with increased mortality in a number of clinical settings, including cardiac and non-cardiac surgery. However, "We have no clinical measures that let us know of impending insufficient oxygenation as anemia progresses" (R.B. Weiskopf). The current proposal is based on experimental and clinical data which suggest that plasma methemoglobin (MetHb) may be a sensitive biomarker of tissue hypoxia and "anemic stress" in surgical patients.

Hypothesis: Increased methemoglobin is a biomarker of tissue hypoxia during acute anemia.

Primary Objective: To demonstrate a direct relationship between decreased Hb and increased MetHb in patients undergoing acute hemodilution on cardiopulmonary bypass (CPB).


Condition or disease Intervention/treatment
Other Functional Disturbances Following Cardiac Surgery Device: Brain Oximetry

Detailed Description:
Acute and chronic anemia continue to be associated with increased mortality in a number of clinical settings, including cardiac and non-cardiac surgery. 1-6 However, as recently stated by one of the pioneers of anemia research; Dr. R.B. Weiskopf: "We have no clinical measures that let us know of impending insufficient oxygenation as anemia progresses".7 Toward achieving this goal, we have developed experimental models to define the adaptive mechanisms which maintain oxygen homeostasis during acute anemia. Our research has identified that increased nitric oxide (NO) production by nitric oxide syntheses (NOSs) may be an important survival mechanism in acute anemia.3;8;9 Experimental data suggests that nNOS may promote survival by maintaining oxygen (O2) homeostasis during acute anemia.10 Resultant increases in nitric oxide (NO) contributes to adaptive cell signaling mechanisms and also increase oxidation of hemoglobin (Hb) to methemoglobin (MetHb).3 In addition, oxygen extraction results in increased levels of deoxyhemoglobin which has been proposed to act as a nitrite (NO2-) reductase to generate additional bioactive NO, thereby promoting vasodilation in hypoxic vascular beds.11-15 Thus, by more than one mechanism, increased MetHb may be indicative of hemoglobin desaturation, tissue hypoxia and activation of adaptive tissue responses to anemia. These responses may identify the threshold for local tissue hypoxia or "anemic stress". In attempt to determine if such mechanisms are active in humans we performed a retrospective study in patients undergoing cardiopulmonary bypass (CPB) during heart surgery to determine if plasma MetHb increased as Hb decreased during CPB. We observed an inverse relationship between Hb and MetHb that was independent of red blood cell transfusion and exogenous nitrate use

Study Type : Observational
Actual Enrollment : 68 participants
Observational Model: Cohort
Time Perspective: Prospective
Official Title: A Prospective Analysis of Methemoglobin as a Biomarker of Tissue Hypoxia During Acute Hemodilutional Anemia in Patients Undergoing Heart Surgery
Study Start Date : January 2013
Actual Primary Completion Date : August 2016
Actual Study Completion Date : August 2016

Resource links provided by the National Library of Medicine


Group/Cohort Intervention/treatment
Heart surgery during CPB
All patients undergoing heart surgery using cardiopulmonary bypass who have a pre-operative Hb value greater than 90 g/L, no evidence of hypoxemia (SaO2 > 90%) and no history of congenital methemoglobinemia. Exclusion criteria will include severe hypoxemia, acute or chronic renal failure requiring dialysis, emergency surgery or the lack of a PA catheter. Non invasive brain oximetry will be used to assess the brain oxygen tension during surgical procedure.
Device: Brain Oximetry
Non invasive brain oximeter will be applied on the patient's forehead to monitor the brain oxygen saturation throughout the surgery.
Other Name: Nonin equinox oximeter




Primary Outcome Measures :
  1. Arterial methemoglobin levels [ Time Frame: 18 months ]
    To determine if there is an association between increased methemoglobin and tissue hypoxia following heart surgery


Secondary Outcome Measures :
  1. Cerebral tissue oxygen saturation [ Time Frame: 18 months ]
  2. Plasma erythropoietin levels [ Time Frame: 18 months ]
  3. Plasma nitrate/nitrite levels [ Time Frame: 18 months ]
  4. Plasma hepcidin levels [ Time Frame: 18 months ]
    Relationship between plasma hepcidin levels and hemoglobin levels


Other Outcome Measures:
  1. Adverse outcomes including mortality, myocardial infarction, low output syndrome, stroke and renal dysfunction [ Time Frame: 18 months ]

Biospecimen Retention:   Samples With DNA
Plasma will be retained for analysis of plasma erythropietin, hepcidin and and nitrate/nitrite levels


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Ages Eligible for Study:   18 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Sampling Method:   Non-Probability Sample
Study Population
heart surgery with cardiopulmonary bypass
Criteria

Inclusion Criteria:

  • patients undergoing heart surgery using cardiopulmonary bypass at St. Michael's Hospital who have a pre-operative Hb value greater than 90 g/L, no evidence of hypoxemia (SaO2 > 90%) and no history of congenital methemoglobinemia.

Exclusion Criteria:

  • severe hypoxemia, acute or chronic renal failure requiring dialysis, emergency surgery or the lack of a PA catheter (current standard of care at St. Michael's Hospital is to insert a PA catheter in > 90% of patients).

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01883713


Locations
Canada, Ontario
St. Michael's Hospital
Toronto, Ontario, Canada, M5B 1W8
Sponsors and Collaborators
St. Michael's Hospital, Toronto
Investigators
Principal Investigator: Gregory Hare, MD, PhD St. Michael's Hospital, Toronto

Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
Responsible Party: St. Michael's Hospital, Toronto
ClinicalTrials.gov Identifier: NCT01883713     History of Changes
Other Study ID Numbers: REB# 12-015
First Posted: June 21, 2013    Key Record Dates
Last Update Posted: April 17, 2018
Last Verified: April 2018

Keywords provided by St. Michael's Hospital, Toronto:
anemia
CPB
methemoglobin
hypoxia

Additional relevant MeSH terms:
Hypoxia
Pathologic Processes
Signs and Symptoms, Respiratory
Signs and Symptoms