154 compared to 54 mmol per liter of sodium in intravenous maintenance fluid therapy for adult patients undergoing major thoracic surgery (TOPMAST): a single-center randomized controlled double-blind trial

PURPOSE

To determine the effects of the sodium content of maintenance fluid therapy on cumulative fluid balance and electrolyte disorders.

METHODS

We performed a randomized controlled trial of adults undergoing major thoracic surgery, randomly assigned (1:1) to receive maintenance fluids containing 154 mmol/L (Na154) or 54 mmol/L (Na54) of sodium from the start of surgery until their discharge from the ICU, the occurrence of a serious adverse event or the third postoperative day at the latest. Investigators, caregivers and patients were blinded to the treatment. Primary outcome was cumulative fluid balance. Electrolyte disturbances were assessed as secondary endpoints, different adverse events and physiological markers as safety and exploratory endpoints.

FINDINGS

We randomly assigned 70 patients; primary outcome data were available for 33 and 34 patients in the Na54 and Na154 treatment arms, respectively. Estimated cumulative fluid balance at 72 h was 1369 mL (95% CI 601-2137) more positive in the Na154 arm (p < 0.001), despite comparable non-study fluid sources. Hyponatremia < 135 mmol/L was encountered in four patients (11.8%) under Na54 compared to none under Na154 (p = 0.04), but there was no significantly more hyponatremia < 130 mmol/L (1 versus 0; p = 0.31). There was more hyperchloremia > 109 mmol/L under Na154 (24/35 patients, 68.6%) than under Na54 (4/34 patients, 11.8%) (p < 0.001). The treating clinicians discontinued the study due to clinical or radiographic fluid overload in six patients receiving Na154 compared to one patient under Na54 (excess risk 14.2%; 95% CI - 0.2-30.4%, p = 0.05).

CONCLUSIONS

In adult surgical patients, sodium-rich maintenance solutions were associated with a more positive cumulative fluid balance and hyperchloremia; hypotonic fluids were associated with mild and asymptomatic hyponatremia.

Introducing TOPMAST, the first double-blind randomized clinical trial specifically dedicated to perioperative maintenance fluid therapy in adults

BACKGROUND

Although prescribed to every patient undergoing surgery, maintenance fluid therapy is a poorly researched part of perioperative fluid therapy. The tonicity of the chosen solutions, could be an important cause of morbidity, with hyponatremia being a potential side effect of hypotonic solutions, where isotonic solution could lead to fluid overload.

METHODS

The TOPMAST-trial is an ongoing prospective single-center double-blind randomized trial comparing an isotonic and a hypotonic maintenance fluid strategy during and after surgery in patients undergoing different types of major thoracic surgery. Patients receive NaCl 0.9% in glucose 5% with an added 40 mmol L-1 of potassium chloride or a premixed solution containing 54 mmol L-1 sodium, 55 mmol L-1 chloride and 26 mmol of potassium at a rate of 27 mL per kg of body weight per day. The primary hypothesis is that isotonic maintenance solutions cause a more positive perioperative fluid balance than hypotonic fluids. Different secondary safety endpoints will be explored, especially the effect of the study treatments on the occurrence electrolyte disturbances (e.g. hyponatremia, hyperchloremia) and a set of clinical endpoints. Efficacy endpoints include the need for resuscitation fluids and assessment of renal and hormonal adaptive mechanisms. An anticipated 68 patients will be included between March 2017 and January 2018.

DISCUSSION

The study will provide the most comprehensive evaluation of clinically important outcomes associated with the choice of perioperative maintenance fluid therapy.