Informed Written consent:  yes

    Anaesthesia Technique:

·       Patients will be thoroughly counselled during the pre-operative evaluation and will be properly explained about the procedure, and study before taking the written consent.

·       Patients will be kept nil by mouth for 8 hours.

·       In the operation Theatre, a good venous access will be secured with 18G IV cannula and all the patients will be preloaded with 8 ml/kg of Ringer’s lactate solution.

Premedication:

·       Injection Ondansetron 4mg(0.1mg/kg)IV 5 min before induction

·       Injection Glycopyrrolate 0.2mg/kg  (5 mcg/kg)IV5 min before induction

·    All baseline parameters will be observed and recorded which consist of Electrocardiography(ECG), Heart rate(HR), Non-invasive Blood Pressure(NIBP) and Pulse Oximeter(SpO₂) ,Respiratory Rate before the procedure.

·    Basic necessities like Anaesthesia machine, monitors,  resuscitation drugs, airway equipments and suction apparatus and equipment for spinal anaesthesia will be checked.

The patient will be kept in  lateral position with the limb to be operated on the lower side

•     Under all Aseptic & Antiseptic precautions spinal anesthesia will be given in L3 –L4 intervertebral space in all cases. 25G Quincke Spinal needle will be inserted. After confirmation of free CSF flow,with the bevel of the needle pointing down , study drug will be injected at the rate of 0.1ml/Second intrathecally according to Group.

•     Patient is made to remain in lateral position for 10 minutes.Monitoring of parameters will be started immediately on making the patient supine.

•     Surgery will be allowed once the peak sensory(T12) and motor blockade (Bromage 3)are achieved.

•     The study drug for spinal anesthesia will be prepared before anesthesia by an anesthesia assistant , who will not participate in the subsequent patient assessment. The solutions will be administered by a second attending anesthesiologist ,who will be blinded to the drug used.

•     If during study, there is failure of spinal anaesthesia or supplementation of general anaesthesia is required then that case will be excluded from study.

DRUG  PREPARATION-

Group L- Inj Levo-Bupivacaine 0.5% 1ml(5mg)

Group R-Inj. Ropivacaine 0.5% 1ml(5mg)

 The first patient in group L will be received 0.5% Levo-bupivacaine 1ml (5.0 mg) and the first patient in group R will be received 0.5%  Ropivacaine1ml(5.0 mg).

 The testing interval in each group will be 0.5 mg. If the response of the previous patient will effective, the dose of intrathecal  local anesthetic for the next patient will be decreased by 0.5 mg in that group.

Conversely, if the response of the patient will be ineffective, the dose of intrathecal  local anesthetic for the next patient will increase by 0.5 mg in that group.

An effective outcome will be defined as a T12 sensory blockade level maintained for more than 60 min, and a Bromage score of 3 on the operation side within 10 min after injection otherwise the outcome was ineffective.

 The ED₅₀ of 0.5% Levo-bupivacaine and 0.5% ropivacaine will be calculated using the Dixon and Massey formula( annexure 2)

·          For ensuring blinding, randomly allocated coded syringes of drugs will be prepared after taking all aseptic and antiseptic precautions by a fellow anesthesiologist not involved in performing subarachnoid block or recording of the outcome during intraoperative and postoperative periods. The Patient and theAnesthesiologist performing subarachnoid block will be blinded to the content of the drug.The content of the drug will be unblinded after 24 hours of performing subarachnoid block.