Liberal Versus Restrictive Fluid Protocols in Adults

Prior to surgery, all patients will undergo pre-anesthetic checkup including detailed history, physical, systemic examination, height and weight of the patient. All patients will be investigated for exclusion of any of the above mentioned contraindications. Routine preoperative laboratory investigations as complete blood count, grouping, coagulation profile, electrolytes and preoperative baseline serum creatinine will be measured. Patients should have low molecular weight heparin administered till the evening prior to daytime trauma lists. This precaution allows for an appropriate window of time to minimize the risk of bleeding related to neuraxial anesthesia. All patients will be kept nil per mouth 6 h for solids and 2 h for water and clear liquids.

Preparation of the patient and conduct of anesthesia:

Written consent and emergency resuscitation equipments including airway devices, advanced life support drugs for LA toxicity and intraoperative adverse events will be available. All patients will be anesthetized by the same team of anesthesiologists and operated upon by the same surgeon who will be unaware of the study medications.

After arriving at the operative room, the pulse oximetry, electrocardiography, temperature probe and non-invasive blood pressure monitor will be applied. A large bore I.V. cannula (18 gauge) will be inserted.

Spinal anesthesia will be used for all patients. Under aseptic technique and local skin infiltration with 1% lidocaine, spinal anesthesia will be performed at the L3-4 or L4-5 spinal interspace by 25 gauge spinal needle. After successful cerebrospinal fluid recognition, 10 mg heavy bupivacaine 0.5% mixed with 25 ug fentanyl will be injected into the subarachnoid space. Then the spinal needle will be removed and the patients will be positioned carefully to the suitable position. Once adequate anesthesia to at least T10 dermatome achieved, the operation will be allowed to be started. Supplemental oxygen will be administered via face mask at flow rate between 5 and 8 L/min. Management of the patients will be performed by another anesthesiologist unaware about the used protocol. Vital signs including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressur (MBP) and arterial oxygen saturation (SpO2) will be recorded as baseline 5 min before conduction of spinal anesthesia, immediately after conduction of anesthesia then every 5 min till end of surgery. The level of sensory block will be assessed before beginning of surgery using an ice cube. Urinary catheter will be inserted for all patients. Hypotension defined as decrease in mean blood pressure (MAP) to more than 20% of baseline values will be treated with a 3 mg I.V. bolus of ephedrine repeated every 2 min if hypotension persists. If hypotension persists after 30 mg ephedrine, additional amounts of Ringer's lactate (5ml/ kg) will be infused through the 18 gauge cannula.

Patients will be asked to report any intraoperative pain or discomfort using visual analog scale (VAS) of 0-10.

After finishing surgery, patients will be transferred to the surgical ICU where they will be monitored by an intensivist who will be blinded to the study group.

Once the patients sent to ICU, both groups will receive 1.5 ml/kg/h of Ringer's lactate solution as fluid maintenance. Follow-up will be done for 5 days postoperatively using:

- Monitors for HR, SBP, DBP, MBP, SpO2 , respiratory rate and recovery time of motor blockade (up to Bromage 2)

- Analgesia: paracetamol 1 gm/ 6 hours regularly

- Supplemental oxygen will be provided in the first 24 hours after the operation if arterial oxygen saturation < 94%.

- Early mobilization: will improve oxygenation and respiratory function.

- Fluid balance as hypovolemia is common postoperatively and oral fluid intake should be encouraged over the intravenous route.

- Urinary tract infections (UTI): is common and urinary catheters should be removed as soon as possible to reduce the risk of infection and urine output will be collected and calculated as [after 12 hours, on day 2 (in 24 hours), 3 (in 24 hours), and 5 (in 24 hours after surgery]

- Routine laboratory investigations as CBC, coagulation profile, electrolytes, blood urea and serum creatinine.

- Symptoms suggestive of AKI: fatigue, loss of appetite, headache, nausea, vomiting and pain in the flanks Patients will be discharged from ICU when hemodynamics are stable and laboratory investigations are within normal.