BACKGROUND: Regional anaesthesia is one of the widely practiced ways for mitigating surgical pain. Interruption of pain is central to the anaesthetic practice .Onset, duration and the quality of block depends on type of local anaesthetic used. Many long acting local anaesthetics have been tried, viz..bupivacaine, ropivacaine ...etc to increase duration of action , but they have limitations like delayed onset, varying quality of blockade and unpredictable duration of action. Alkalinization of lignocaine has been shown to hasten the onset.
Efforts to find a better adjuvant in regional anaesthesia are underway since long. Sedation, stable haemodynamics and an ability to provide smooth and prolonged post- operative analgesia are the main desirable qualities of an adjuvant in central neuraxialanaesthesia . Epidural adjunct to local anesthetics (LA) have been in use since long and α2 agonists are being increasingly used for similar purpose. The present study aims at comparing the hemodynamic, sedative, and analgesia potentiating effects of epidurally administered dexmedetomidine. Our study is directed at evaluation of efficacy of dexmeditomedine in influencing the onset and duration of blockade as compared to that of NaHC03 when used as an adjuvant to epidural lignocaine.

METHOD After obtaining approval from ethical committee, written informed consent from patients was taken.

Study conducted at NRI Medical College in the Department of anaesthesiology, Chinakakani Prospective randomized double blind controlled trial

INCLUSION CRITERIA: • All adult patients with recent [<48hrs] lower limb trauma scheduled for orthopaedic surgeries . • ASA grade 1 and 2

EXCLUSION CRITERIA: 1) ASA grade 3 and 4.
2) History of drug allergy to sodium bicarbonate, dexmedetomidine, local anesthetic.
3) Coagulation abnormality
4) Patients with HTN, DM, pulmonary, hepatic, cardiac,renal disorders.
Patients are randomized and allocated into 3 groups –D, S and C using computer generated chart.
Patients in group D receive 12.5 ml of 2% Lignocaine + dexmedetomedine 0.5 mcg / kg in 1.5 ml solution (Total-14 ml)
Patients in group S receive 12.5 ml of 2% Lignocaine + 1.5 ml of 7.5% sodium bicarbonate (Total-14ml)
Patients in group C receive 12.5ml of Lignocaine + 1.5 ml of normal saline (Total-14 ml).

Drugs are loaded by an anaesthetist who is blinded to the study, coded and handed over to another anaesthetist who is blinded to the drug for administration.
Outcome in terms of
1. Onset of sensory block
2. Time for attaining peak sensory level
3. Time for two segment regression from peak level
4. Requirement of vasopressor are compared.

Statistical methods : Over all Power of the study was calculated by using online power and sample size calculator for K means .Power of the study for comparsion between two groups is calculated by using online power caluculator for difference between two means. Summarization of data was done with the help of measures of central tendecy and dispersion (Mean and SD).Differences between average values of different parameters under study was calculated with the help of t-test of difference between two independent sample means. Z-test of proprtions was used to test the differences in proportions of males and females between the groups.t-test and Z-test were done with the help of in-silico project support for life sciences online calculator .

DISCUSSION Morrison,G.Capogna et al did double blind randomized study in 116 healthy women to evaluate whether alkalinization potentiates the analgesic effect of lidocaine fentanyl epidural anaesthesia and concluded that alkalinization decreases analgesic requirement during surgery .Ruby Mehta, Ramesh Koppal et al did a study in 50 patients undergoing surgery under brachial plexus block. Patients are divided into two groups –1stlignocaine , 2nd that Alkalinization of lignocaine offers an earlier onset and it provides a good intensity and adequate depth and a satisfactory distribution of the regional block. Carollo DS et al Dexmedetomidine: A review of clinical applications showed epidural dexmedetomidine exhibits synergism with local anesthetics prolonging the sensory/ motor block duration time, postoperative analgesia, and results in intense motor block, without any additional morbidity.

RESULTS: Total 90 patients are enrolled in the study in 1year duration with 30 in each group.Demographic profiles of the patients in all groups are comparable with regards to age and sex. There is a highly statistically significant difference between average onset of sensory blockade of Dex group and soda bicorbonategroup.Average onset of sensory blockade ofDex is less than that of soda bicorbonate group. There is no statistically significant difference between average time for peak sensory level of Dex group and soda biocorbonategroup.There is a statistically significant difference between average 2 segment regression of Dex group and soda bicorbonategroup.Average time for 2 segment regression in minutes in soda bicorbonate is significantly less than that of dex group.

There is no statistically significant difference between average mephentramine consumed in Dexmedetomidine group and soda bicorbonate group.

CONCLUSIONS: Neuraxialdexmedetomidine is a favourable local anaesthetic adjuvant with faster onset and longer duration. group received group received lignocaine with sodium bi carbonate.