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Perioperative changes in exhaled nitric oxide during oesophagectomy
Piers R Boshier1, Alison L Knaggs2, George B Hanna1
1Department of Surgery and Cancer, Imperial College London, United Kingdom.
Introduction:
Oesophagectomy is a major surgical procedure, associated with high rates of postoperative cardiopulmonary morbidity, that is in part due to the frequent requirement for periods of intraoperative one-lung ventilation (OLV). The current pilot study aims to investigate variation in exhaled NO levels during oesophagectomy with emphasis on the response to OLV and correlation to physiological variables and clinical outcomes.
Methods:
Breath-to-breath concentrations of NO were analysed in patients undergoing oesophagectomy at various stages of two-lung ventilation. Furthermore, we also analysed the effects of OLV both in the selectively ventilated and collapsed lungs.
Results:
Twenty-four patients were recruited to the study (17 male, 60.2 ± 12.8 years). Regarding two-lung ventilation, the baseline levels of NO (2.9 ppb), tended to increase after re-inflation of the collapsed lung (3.5 ppb, P = 0. 888) and decreased at 2 h (2.1 ppb, P = 0.022) and 12 h (2.2 ppb, P = 0.733) postoperatively. Compared to baseline, selective measurements of NO at the end of OLV demonstrated a significant reduction of NO levels in the ventilated lung (1.6 versus 3.1 ppb, P = 0.028), whereas re-inflation of the collapsed lung revealed higher levels of NO (3.4 versus 2.7 ppb, P = 0.657). Exhaled NO correlated significantly with systolic blood pressure and lactate (P < 0.007). Exhaled NO levels tended to be higher at all perioperative time points in patients who developed postoperative respiratory complications (P > 0.05).
Conclusion:
This study highlights effects of oesophagectomy and OLV on exhaled concentrations of NO. The observed variations may be related to differential ventilation during OLV altering the complex balance between synthesis and consumption of NO as well as local and generalised tissue injury associated with this surgery. Findings should prompt further larger studies to establish the relationship between exhaled NO and lung injury both during and after oesophagectomy and one-lung ventilation.