The Effect of Intraoperative Arterial Oxygen Pressures on Early Post-Operative Patient and Graft Survival in Living Donor Kidney Transplantation
Condition: Kidney Transplant; Complications; Hyperoxia; Graft Dysfunction
MeSH terms: Hyperoxia
Study type: Observational

Summary: 
      We evaluated the prognostic role of the intraoperative arterial oxygen partial pressures
      (PaO2) on postoperative patient and graft survival in living donor kidney transplantations.
    

Detailed description: 
      Undoubtedly, one of the most important elements of life on earth is oxygen. Aerobic organisms
      adapted to the 20.8% oxygen ratio in the atmosphere have survived even lower than this
      concentration by developing various defense mechanisms. The real question is whether high
      levels of oxygen in the blood, which are administered iatrogenically, leads to tissue
      destruction.

      Reactive Oxygen Species (ROS), which is a result of hyperoxia and may be useful even at low
      levels, may cause tissue loss due to oxidative stress, also called oxygen-free radicals. ROS,
      whose toxicity is very destructive with its accumulation, may cause damage to macromolecular
      structures such as lipids, protein, mitochondrial and nuclear DNA. On the organs of the
      exposed oxidative stress; For lung, asthma, chronic obstructive pulmonary disease (COPD),
      acute respiratory distress syndrome (ARDS), cardiovascular system, ischemic heart disease
      (IHD), hypertension, shock, heart failure, while kidney failure and glomerulonephritis can
      cause unwanted complications.

      The kidneys get for circulation, only 20% of the cardiac output. Since the arterial and
      venous (AV) structures in the kidneys are anatomically parallel to each other, the oxygen
      concentration in the renal vein may be relatively higher than the efferent arteriole and
      cortex because of the oxygen shunt. Thanks to this mechanism, in clinical situations where
      partial oxygen pressure (Pa02) is high, the oxygen concentration presented to the kidney
      tissues remains within a certain limit. In fact, AV shunt protects kidney tissue with a
      structural antioxidant mechanism. Thus, the increase in renal blood flow (RBF) will cause an
      increase in AV oxygen shunt in parallel, the blood coming to the kidneys participates in the
      systemic circulation without entering the renal microcirculation. It has been suggested that
      shunt occurs to protect from hyperoxia at the tissue level by decreasing blood volume in the
      kidneys. Oxidative stress, which is inevitable as a result, will increase tissue hypoxia
      paradoxically by increasing the oxygen consumption of the kidneys. It is stated that uremic
      toxin, especially indoxyl sulfate (IS) accumulation is the cause of the mentioned table.
      Apart from IS, phenyl sulfate and ρ-cresy sulfate make tubular cells susceptible by reducing
      glutathione levels. Thus, increased renal hypoxia, renal oxidative stress will result in
      renal inflammation and fibrosis.

      According to recent studies, the antioxidant defense mechanism has been shown not only to be
      limited to AV shunt. But also the dynamic regulation of intrarenal oxygenation in RBF
      changes. However, mechanisms developed to prevent hyperoxia have made kidney tissue sensitive
      to hypoxia. The increase in AV oxygen shunt causes an increase in tissue hypoxia.

      Although endogenous antioxidant mechanisms play a major role against free radicals, the
      postoperative effects of iatrogenic hyperoxia on transplanted kidney grafts and patient
      survival remain a subject to be investigated. That's why we aim to understand the impact of
      iatrogenic hyperoxia during the living donor kidney transplantation operations by
      retrospective data analyzing.
    

Intervention name(s): Arterial blood gas samples
Intervention type(s): Procedure
Intervention description(s): Blood gases taken during the operation will be analyzed retrospectively. Whether these results have an effect on graft survival will be examined by reaching their records in the postoperative period.
Observational model: Case-Control
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        We enrolled only 1000 adult living donor kidney transplantations closed files started from
        1st of January 2017 to 1st of November 2019. The study conducted at the Department of
        Anesthesiology and Critical Care with the Department of General and Visceral Surgery
        Medical Center. All recipient surgical procedure was carried out by the same specialized
        transplantation surgeons and anesthesiologists after a positive vote of the local ethics
        committee for transplantation. Recipients with a history of myocardial infarction, chronic
        respiratory disease (bronchial asthma, COPD) were excluded from the study.