Liberal Versus Restrictive Fluid Protocols in Adults

• SBP, DBP, MAP[ Time Frame: 24 hours ]
  systolic blood pressure (mmHg) diastolic blood pressure (mmHg) mean arterial blood pressure (mmHg)
• arterial oxygen saturation[ Time Frame: 24 hours ]
• heart rate[ Time Frame: 24 hours ]
  beats/min

The term acute kidney injury (AKI) is used to describe a rapid deterioration (hours to days) of renal function. This rapid deterioration leads to accumulation of plasma waste products, such as urea and creatinine. Accumulation of urea and other nitrogen-containing substances in the blood stream lead to a number of symptoms, such as fatigue, loss of appetite, headache, nausea and vomiting. Marked increases in the potassium level can lead to irregularities in the heartbeat, which can be severe and life-threatening. Fluid balance is frequently affected, though blood pressure can be high, low or normal. Pain in the flanks may be encountered in some conditions (such as thrombosis of the renal blood vessels or inflammation of the kidney); this is the result of stretching of the fibrous tissue capsule surrounding the kidney. Perioperative AKI is a leading cause of morbidity and mortality; It is associated with increased risk of sepsis, anemia, coagulopathy, and mechanical ventilation. The first publication of consensus criteria for AKI was published in 2004. The system was named RIFLE (risk, injury, failure, loss of kidney function and end-stage renal failure) and used sCr or urine output to define AKI. Later, in 2007, a modified definition of the RIFLE criteria was published by the Acute Kidney Injury Network (AKIN) .Although the AKIN criteria evolved from the RIFLE criteria, a major advance was the understanding that even small changes in sCr concentrations are associated with increased morbidity and mortality. The AKIN criteria allowed definition of AKI even without knowledge of baseline sCr. In 2012, a clinical practice guideline of AKI was proposed by the Kidney Disease Improving Global Outcomes (KDIGO) Foundation. The guideline included a comprehensive review of AKI definition, risk assessment, diagnosis, prevention, treatment and renal replacement therapy. A common practice to maintain effective blood volume and thus kidney perfusion is intravenous (I.V.) hydration. Correcting hypovolemia is an essential perioperative hemodynamic goal and appropriate hydration is considered important for the avoidance of AKI. Perioperative fluid therapy has been studied extensively, but the optimal strategy remains controversial and uncertain. Much of the current debate surrounds the type of fluids administered (colloid versus crystalloid), the total volume administered (restrictive versus liberal), and whether the administration of fluids should be guided by hemodynamic goals (goal directed [GD] versus not goal directed). Administering a large amount of I.V. fluid in the perioperative period is a common clinical practice. Although fluid loading may expand intravascular space, improve organ perfusion or tissue oxygenation and reduce minor postoperative complications in laparoscopic surgery, excessive fluid may also increase some perioperative complications. Intraoperative urine output is often monitored but rarely responds to fluid administration. Clearance of fluid during general anesthesia is only a small fraction of that observed in conscious volunteers. Infusion of crystalloids during anesthesia shows reduced clearance and slower distribution such that intraoperative oliguria may not reflect fluid status or predict future AKI. Given that liberal fluid administration can be correlated with worse postoperative outcome, the recommendation to maintain urine output of at least 0.5 ml/kg/h should be considered.

• Drug: Ringer lactate
  Randomization will be done using computer generated table of random numbers in a 1:1 ratio and will be conducted using sequentially numbered, opaque and sealed envelope. The trial will be planned that neither the doctors (investigators) nor the patients will be aware of the group allocation and amount of fluid received. Intraoperative and postoperative data collections will be achieved by the same blinded anesthiologist. Patients will be randomly allocated into two groups: Group L: 40 patients who will be subjected to ''liberal" approach of intraoperative 18-20 ml/kg/h of Ringer's lactate starting from conduction of spinal anesthesia. Group R: 40 patients who will be subjected to ''restrictive" approach of intraoperative 4-6 ml/kg/h of Ringer's lactate starting from conduction of spinal anesthesia. Blood loss will be replaced if more than 500 ml in a ratio of 3 ml crystalloid: 1 ml blood.

• Active Comparator: Ringer's lactate 18-20 ml/kg
  Patients will be randomly allocated into two groups of 40 patients each: Group L:will receive 18-20 ml/kg/h of Ringer's lactate starting from conduction of spinal anesthesia.
• Active Comparator: Ringer's lactate 4-6 ml/kg
  Patients will be randomly allocated into two groups of 40 patients each: Group R: will receive 4-6 ml/kg/h of Ringer's lactate starting from conduction of spinal anesthesia.