The effect of standard versus restricted fluid therapy in pediatric patients undergoing major elective abdominal, thoracic and genitourinary surgery: a non-blinded randomized controlled trial

The main purpose of perioperative fluid therapy is to maintain hemodynamic stability and adequate tissue perfusion. Fluid overload will lead to pulmonary oedema, cardiac complication such as myocardial stress, electrolyte imbalance like dilutional hyponatremia and weight gain. Hyponatremia is the most common electrolyte disorder in postoperative period. On the other hand, inadequate fluid infusion will lead to hypovolemia, inadequate tissue perfusion and organ dysfunction. Standard fluid therapy in pediatric patients  includes infusing maintenance and deficit fluid according to Holliday-Segar formula and replacing third space blood losses. Holliday-Segar formula is known as 4-2-1 rule which is still widely used for fluid therapy in paediatric patients. Third space loss is the supposed seepage of fluid around the surgical site from vascular space, it’s replacement depends on the tissue exposure related to surgery i.e. 2ml/kg/hr for superficial surgery, 4-7ml/kg/hr for thoracotomy and 5-10ml/kg/h for abdominal surgery. Recently, its replacement has being questioned and is being mentioned as arbitrary. Restrictive fluid therapy is similar to standard fluid therapy but without third space loss replacement. Goal directed fluid therapy (GDT) is the fluid administration based on hemodynamic parameters and guided by cardiac output monitoring. The purpose of GDT is to avoid overloading the patient with fluids and at the same time not compromising tissue perfusion. GDT showed decreased postoperative morbidity and mortality in adults. In children, however, it is not well researched. Electrical cardiometry is a non-invasive technique for hemodynamic monitoring. It determines stroke volume, stroke volume variation, cardiac output, cardiac index based on changes in electrical conductivity within the thorax., i.e. Thoracic Electrical Bioimpedance. It has been validated against gold standard methods such as thermodilution. It is FDA approved and validated for neonates, children and adults. Studies are lacking regarding the effect of restrictive fluid therapy in paediatric patients. This study will try to explore the various effects of standard fluid therapy with replacement of calculated third space losses against restrictive fluid therapy in paediatric patients undergoing major abdominal, thoracic and genitourinary surgery.

STUDY PROTOCOL

Pre-operative evaluation

The detailed pre-anaesthesia checkup will be done including history, treatment history, airway examination and systemic examination, body weight estimation. Fasting guidelines (i.e., 8 hrs for solids, 6 hrs for formula feeds, 4hrs for breast milk, 2 hrs for clear liquids) will be explained to parents and informed written consent will be obtained from them. Investigations such as serum sodium, potassium, calcium, CBC, blood urea, serum creatinine, chest x ray will be done.

 Intra operative care

Patients will be randomised into 2 groups (Standard and restricted fluid therapy group). After ensuring adequate NPO status patient will be shifted to operating room and ASA standard monitors such as pulse oximeter, NIBP, electrocardiography will be attached and baseline values of pulse rate, SpO2, blood pressure, ECG will be recorded. Cardiometry will be attached and its baseline readings of cardiac output, cardiac index, stroke volume and stroke volume variation will be recorded. Anaesthesia will be induced by either inhalational anaesthetic agents or intravenous induction agents. IV cannula will be secured before or after induction depending upon the co-operation of the patient. Intravenous isotonic fluid (Ringer’s Lactate) will be started as per Holliday-Segar formula. Muscle relaxants will be injected and patient will be intubated with appropriate sized endotracheal tube. Surgery will be allowed to start once all the monitors are in place and the baseline values have been taken. Patients in the standard fluid therapy group will receive maintenance and deficit fluid according to Holliday-Segar formula, replacement for 3rd space loss and ongoing blood losses, whereas patients in restricted fluid therapy group will be infused with maintenance fluid, deficits and ongoing blood losses without replacement for 3rd space loss. Ongoing blood loss will be replaced 3:1 with isotonic fluids (Ringer’s Lactate) and 1:1 with blood according to the anaesthesiologists’ decision. Third space loss will be given according to the data in Table 1. Monitoring of cardiometry, type and volume of IV fluid given, ongoing blood losses, hemodynamic status assessment will be done. If any major blood loss occurs and blood transfusion is needed, those patients will be excluded from the study. During surgery if any patient develops major hemodynamic changes needing continuous infusion of vasopressors they will be excluded from the study. In both the groups if the SVV is more than 15% persistently for more than 5 min at any time intra-operatively fluid bolus will be given at 5ml/kg. Number of such fluid boluses will be recorded. At the end of surgery venous blood will be collected to measure serum lactate, sodium, potassium, calcium, blood urea and serum creatinine.

Table 1

Type of surgery

Third space loss replacement

|Thoracotomy

4-7ml/kg/h

|Abdominal surgery

5-10ml/kg/h

Post operative care

After completion of surgery, patient will be extubated and shifted to recovery room. Post operative weight will be taken for patients if possible. Post-operative nausea and vomiting will be assessed using Five-point scale (Table 2). Chest x ray will be done immediately in the postoperative period to look for any signs of fluid overload. Values of blood urea and serum creatinine will be taken on post-operative day 2. Duration of post-operative stay will be noted.

Table 2

Nausea score

Degree of nausea

|0

Nil

|1

Mild

|2

Moderate

|3

Severe

|4

Actual vomiting