Intraoperative fluid therapy for patients undergoing elective liver resection

INTERVENTION: The intravenous fluids most frequently used in perioperative care in Australia are Hartmann’s solution, Normal Saline, and to a lesser extent, Plasmalyte. One mechanism where perioperative fluid therapy can change acid‐base status is when a high chloride concentration found in fluids like Normal Saline causes a hyperchloremic metabolic acidosis. For this reason, Normal Saline is no longer considered a suitable intraoperative fluid replacement therapy for many major surgical procedures, and Hartmann’s Solution and Plasmalyte have become the crystalloid solutions of choice. These solutions are now termed “balanced” solutions as they contain less chloride and have more favourable acid‐base profiles. The quantitative acid‐base effects of fluid therapy during liver resection however is unclear and there are few studies directly comparing Hartmann’s solution and Plasmalyte in this setting. In this study all participants undergoing hepatic resection will be randomised to receive either Hartmanns's solution or Plasmalyte solution for intraoperative crystalloid fluid replacement therapy. General anaesthesia will be managed by a group of specialist anaesthetists using a protocol designed to standardise patient care for patients undergoing hepatic resection at our institution. Induction of anaesthesia will consists of a balanced technique, and anaesthesia and analgesia will be provided as part of routine care. Routine monitoring will include continuous electrocardiography, pulse oximetry, capnography, invasive arterial blood pressure, central venous pressure, urine output and core body temperature. Intra‐operative normothermia will be maintained with warm fluids and a forced‐air warming device. Intravenous fluid protocol: Preoperatively. Patients will be fasted as per Hospital protocols. Clear oral fluids (water, tea/coffee with no milk products, clear apple juice) are allowed up to 4 hours before surgery. Prior to anaesthesia and surgery patients will not receive any additional intravenous fluid boluses. Intraoperatively: Patients will receive their allocated fluid, Hartmann’s solution or Plasmalyte as the sole crystalloid during their surgery. The fluids will be provided in deidentified bags, provided by Baxter Healthcare, to will blind the anaesthetist to the allocated fluid. As per standard practice for patients undergoing liver at our institution, the administration of fluids will be reduced and central venous pressure will be maintained at less than 6 mmHg for the duration of hepatic parenchymal resection. After hepatic resection, an infusion of warm crystalloid fluids will be administered to render patients euvolaemic. The crystalloid fluid solution will be infused at a maintenance rate 1.5‐2 ml/kg/hr. Additional crystalloid boluses to replace surgical blood loss will consist of 3 mls of crystalloid solution for every 1 ml of blood lost. Urine output will be maintained at greater than 0.5 ml/kg/h, and systolic blood pressure maintained within 20% of the pre‐operative value. The use of water to control plasma sodium, dextrose for the treatment of hypoglycaemia, and blood products to correct anaemia or coagulopathy will be at the discretion of treating clinicians and in accordance with hospital protocols. The anaesthetist managing the patient may choose to use colloid in addition to the crystalloid. To avoid the acid‐base effects of different colloids being a confounder in this study, the colloid used in this study will be 20% Albumex (CLS) . We think this is a rational choice as it is supplied free of charge by CSL laboratory to all hospitals in Australia, and has a favorable acid base profile for use in liver surgery. CONDITION: Acid‐base physiology Intravenous fluid therapy Liver resection surgery At the completion of surgery the use of the trial fluid (Hartmanns or Plasmalyte) will discontinue and postoperative intravenous fluid therapy (type/amount and duration) will be continued at the discretion of the attending surgeon and perioperative clinician. PRIMARY OUTCOME: Acid‐base status (measured by base excess) Strong ion difference (sampled from routine blood tests and calculated from the diffrence between plasma cations (sodium and potassium) and anions (chloride and bicarbonate) Total weak acids (measured from routine blood tests which include plasma albumin, and phosphates) SECONDARY OUTCOME: Length of hospital stay Need for mechanical ventilation and its duration Neutrophil gelatinase associated lipocalin (NGAL). Neutrophil gelatinase‐associated lipocalin is a small protein expressed in neutrophils and certain epithelia, including the renal tubules. Renal expression of NGAL is dramatically increased in kidney injury from a variety of causes, and NGAL is released into both urine and plasma. NGAL levels rise within 2 hours of the insult, making NGAL an early and sensitive biomarker of kidney injury. This will be measured from serial urine and blood samples using western blots and Enzyme‐linked immunosorbent assay (ELISA) for NGAL expression. Plasma lactate concentration Serum creatinine Survival to hospital discharge INCLUSION CRITERIA: Adult patients having elective liver resection surgery