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Background: Low sodium levels have been associated with worse prognosis in some subgroups of patients with malignancy. However, this phenomenon remains under-explored in patients undergoing lung resection for non-small cell lung cancer (NSCLC). Our aim was to explore the relationship between sodium levels and outcomes after lung resection and determine which variables affected sodium levels. Methods: All consecutive patients undergoing lung resection between 2016 and 2019 for NSCLC in a single UK centre were included. Patients with missing sodium values were excluded. Sodium levels immediately prior to and after surgery were measured and the difference between these two values was calculated. Hyponatraemia was defined as sodium <135 mmol/L as per the World Health Organisation classification. Primary outcomes were 90-day mortality, post-operative complications, post-operative length of stay (PLOS) and overall survival. Multivariable Cox and logistic regression analyses were performed to identify factors associated with reduced overall survival and low pre-operative serum sodium levels respectively. Results: The study comprised 1,448 patients. The mean age was 68.9 years (±8.7) and 44.1% (n=638) were male. Overall 90-day mortality was 1.9% (n=28). There was no link between lower pre-operative serum sodium levels and 90-day mortality low sodium: 2.4% (n=3) vs. non-low sodium: 1.9% (n=25), P=0.69, although there was a significantly higher composite rate of post-operative complications low sodium: 28.0% (n=35) vs. non-low sodium: 18.8% (n=249), P=0.01 and prolonged PLOS low sodium: 6 days (IQR 4–9 days) vs. non-low sodium: 5 days (IQR 3–8 days), P=0.002 for patients with pre-operative hyponatraemia. Lower pre-operative serum sodium was independently associated with reduced overall survival (hazard ratio 0.950, 95% confidence intervals: 0.922–0.978, P<0.001). Finally, stage III disease, higher Performance Status score, lower body mass index and lower haemoglobin level were all independently associated with pre-operative hyponatraemia. Conclusions: Lower pre-operative serum sodium levels may have an impact on short and long-term outcomes after surgery for NSCLC. If additional studies corroborate these findings, sodium levels should be considered for inclusion in models for risk prediction and prognostication after lung resection.
Singhania et al. (Mon,) studied this question.