Excessive Intraoperative Sodium Chloride Substitution is Associated with delirium and Prolonged Hospital Stay

Objectives: Application of Bretschneider’s cardioplegia often leads to intraoperative hyponatremia. Despite its frequent occurrence, the influence of intraoperative sodium substitution on postoperative outcome is not well known. The aim of this study was to investigate the effects of intraoperative sodium substitution on clinical adverse events.

Methods: This retrospective study included 119 patients who underwent surgical aortic valve replacement using Bretschneider’s cardioplegia. Patients were divided into following groups: (1) no sodium substitution, n = 39; (2) substitution of < 200 mmol hyperosmotic 5.85% sodium chloride solution, n = 49; (3) substitution of >200 mmol sodium chloride solution, n = 31. Sodium chloride substitution was applied when 30 minute post cardioplegia, serum sodium was < 130 mmol/L. Data evaluation included preoperative data, risk factors, laboratory analysis, intensive care unit stay, delirium and postoperative outcome.

Results: Preoperative patient data, organ function parameters, logarithmic EuroSCORE, as well as intraoperative parameters of aortic cross clamp time, extracorporeal circulation and surgery duration were comparable between the groups. All groups had a comparable lowest serum sodium concentration 30 minute after cardioplegia. Postoperative serum sodium concentration remained significantly lower in the no substitution group until 24 hour after surgery when compared with the substituted groups. Sodium chloride substitution led to a significantly increased postoperative diuresis, while the fluid balance after 24 hour was not affected. Mechanical ventilation time and ICU-stay were not significantly different, but the total length of hospital stay was significantly longer in the >200 mmol sodium group versus no substitution. Interestingly TISS10 score, indicating nursing workload on ICU, was significantly higher in the >200 mmol sodium group versus < 200 mmol sodium group at 24 hour after ICU admission. This was associated with higher incidence of delirium in the >200 mmol sodium group (43.4%). Postoperative delirium correlated with ventilation time, time of ICU-stay and with SAPSII score as predictor of morbidity and mortality.

Discussion: Our data show, that sodium substitution during extracorporeal circulation of >200 mmol was associated with prolonged hospital stay, higher TISS10 score and a higher incidence of postoperative delirium that needed medication.

No conflict of interest has been declared by the author(s).