Postnatal exposure to hypobaric hypoxia and its impact on inflammation and injury indexes after a cardiac valve procedure

Abstract

Objectives: There is accumulating evidence that hypobaric hypoxia adaptation confers cardiac protection. We investigated whether postnatal exposure to a high-altitude hypoxia environment results in less inflammation injury and better clinical indexes after a cardiac valve procedure.

Methods: A total of 326 consecutively eligible patients undergoing mitral valve surgery from May 2013 through May 2019 in Sichuan Provincial People's Hospital were retrospectively included and stratified by the altitude of residence: the northwest Sichuan plateau residents (altitude 3000-4000 m, group A, n = 101) and the Sichuan basin residents (altitude <1000 m, group B, n = 225). The primary end point indexes included myocardial injury and inflammatory response indexes, which were assessed by measurements of the levels of cardiac troponin I and high-sensitivity C-reactive protein and of the neutrophil-lymphocyte ratio, in addition to lactate levels. Secondary end point outcomes were ventilation time, chest tube drainage volume and length of stay in the intensive care unit and the hospital.

Results: No differences in baseline data except for haemoglobin concentration were observed between the 2 groups. The serum levels of high-sensitivity C-reactive protein, cardiac troponin I and lactate and the neutrophil-lymphocyte ratio at each time point within 24 h postoperatively were lower in group A than in group B, respectively. The ventilation time was 9 ± 5 and 11 ± 7 h in group A and in group B, respectively (P = 0.004). The chest tube drainage volume was 647 ± 231 and 715 ± 164 ml in group A and in group B, respectively (P = 0.003).

Conclusions: Compared with the low-altitude residents, high-altitude patients exposed to postnatal hypoxia experienced less severe inflammatory reactions, less ischaemic injury and favourable postoperative recovery when undergoing a primary mitral valve procedure.

Keywords: Altitude; Cardiac surgical procedures; Cardiopulmonary bypass; Inflammation.