Spinal anaesthesia is a reliable and safe technique in lower limb and lower abdominal surgeries. Clonidine is a selective partial agonist for alpha-2- adrenoreceptors , which produces sedation,analgesia andhemodynamic stability. Dexmedetomidine is a highly selective alpha-2-adrenoreceptor agonist with the alpha 2:alpha 1 binding ratio of 1620:1 when compared with 220:1 for clonidine which is 8-10 times higher than that of clonidine. The prolongation of spinal anaesthesia after intravenous administration ofdexmedetomidine and clonidine explained by the supra spinal effects of these drugs.

 AIM

 Comparative study of intravenous clonidine( 1mcg/kg)versus intravenous dexmedetomidine (0.5mcg/kg) as premedication to intrathecal 0.5% bupivacaine in patients undergoing lower abdominal and lower limb surgeries.

 PRIMARY OBJECTIVE:

 To compare onset and duration of motor and sensory block

 To compare the duration of analgesia 

SECONDARY OBJECTIVE: 

To assess and compare the sedation score (Ramsay sedation score)

 To assess the shivering intraoperatively and postoperatively between both groups

 To compare the side effects -nausea,vomiting, bradycardia, hypotension. 

STUDY DESIGN:

 A prospective randomised double blind study. 

SAMPLE SIZE:

 The sample size calculated per group ,Group A=28 and Group B=28.

 Patients in each group will receive anaesthesia as follows : 

Group A ~(n=28) patients will receive IV infusion of clonidine 1mcg/kg in 100ml normal saline over 15 minutes+0.5% bupivacaine (hyperbaric)(3.5ml) intrathecal.

Group B~(n=28)patients will receive IV infusion of dexmedetomidine 0.5mcg/kg in 100ml normal saline over 15 minutes +0.5% bupivacaine(hyperbaric )(3.5ml) intrathecal. 

Compare two means (use mean and standard deviation) 

Alpha (a) 0.01 

Beta (ß) 0.05|

 Mean in group 1 (H,) 7.51 

Standard deviation in group 1 (o,) 1.66 

Mean in group 2 (H2) 5.83

 Standard deviation in group 2 (02) 1.29 

Ratio (Group 2 / Group 1) 1

 CALCULATE 

Minimum sample size needed for group 1: 28

Minimum sample size needed for group 2: 28

 Minimum total sample size needed: 56 

INCLUSION CRITERIA:

 American society of anaesthesiologists (ASA) grade I -II. 

Age group between 18-60years. 

Scheduled for lower abdominal and lower limb surgeries. 

Both elective and emergency procedures.

 EXCLUSION CRITERIA: 

Patient refusal.

 History of allergy to study drug.

 Bradycardia of heart rate < 50beats per minute 

Pregnancy

 Coagulopathy 

Major hepatic,renal and cardiovascular dysfunction. 

Obese patients BMI>30kg/m2. 

Tachycardia of heart rate > 100 beats/min 

The enrolled subjects will be randomized into the 2 study groups using computer generated randomization . All patients will be advised to stay nil per oral, solid diet to be consumed for 8 hours prior to surgery,as well as clear oral fluids for 4 hours prior to surgery. On arrival in pre op area IV access with 18G IV cannula will be secured and RL will be started. Establishment of proper standard monitoring systems (pulse oximetry,continuous ECG and non invasive blood pressure monitoring and SPO2).

 Group A(n=28) will receive 100ml NS along with IV infusion of clonidine 1mcg/kg,Group B(n=28)IV infusion of dexmedetomidine 0.5mcg//kg (group B) over 15minutes before spinal anaesthesia. Sitting position with parallel legs recommended for the patients included in this study. Under all sterile conditions,L3-L4 IVDS will be injected with 2ml of 2%lignocaine.Using 25 gauge Quincke spinal needle , the subarachnoid space will be entered at the level of L3/L4 IVDS .By observing free continuous flow in CSF, anaesthesiologist determine that needle placement been correct. 3.5ml of Hyperbaric bupivacaine 0.5% will be given. The patient will be placed in supine position to carry over the initial assessment.

The onset of sensory and motor blockade will be assessed at baseline and 3 minutes interval upto 15minutes. The degree of sensory inhibition will be assessed bilaterally in midclavicular line by assessing the changes in cold sensation using alcohol swab.The test will be performed every 3 minutes from the highest sensory block till 15 minutes and thereafter 5minutes till completion of surgery. Bilateral motor inhibition will be examined using modified bromage score. Theinitiation in motor function after administration of drug will be considered as modified bromage score 1 andfull motor blockade will be considered as modified bromage score 4. 

Post operative pain will be assessed using the visual analog scale (VAS) upto first request for rescue analgesia.This finding correlates with the duration of analgesia which is defined as the time from intrathecal injection to the time when VAS score is >4 or when the patient first demands for rescue analgesia. Inj paracetamol 15-20mg/kg along with injection tramadol 50mg will be given intravenously and inj ondansetron 4mg will be given if patient experiencingnausea and vomiting. Patient’s heart rate, NIBP, SPO2 will be monitored at 3 minutes interval upto 15 minutes after every 5minutes upto 60 minutes after that every 10 minutes until the end of the surgery.Through out the surgery patient will receive 6 litres of oxygen per minute through face mask. 

The Ramsay sedation score will be used to assess sedation. Excessive sedation will be defined as a sedation score which will be greater than four. Intraoperatively and postoperatively shivering will be assessed using Crossley and Mahajan score. Post operatively patient will be monitored for nausea, vomiting and shivering. 

References: 

Intravenous dexmedetomidine versus clonidine for prolongation of bupivacaine spinal anesthesia and analgesia- A randomized double-blind study Dr. Velayudha S Reddy, Department of Anaesthesiology, Rajiv Gandhi Institute of Medical Sciences, Kadapa - 517 502, Andhra Pradesh, India. Journal of Anaesthesiology Clinical Pharmacology 29(3):p 342-347, Jul–Sep 2013. | DOI: 10.4103/0970-9185.117101 Effects of intravenous dexmedetomidine on hyperbaric bupivacaine spinal anesthesia: A randomized study.Chilkunda N Dinesh, N A Sai Tej, Bevinaguddaiah Yatish , Vinayak S Pujari , R M MohanKumar, Chadalawada V R Mohan Department of Anesthesiology, M. S. Ramaiah Medical College, Bangalore, Karnataka, India. PMID: 24843333 PMCID: PMC4024677 DOI: 10.4103/1658-354X.130719 A Comparative Study of Intravenous Dexmedetomidine and Intravenous Clonidine for Postspinal Shivering in Patients Undergoing Lower Limb Orthopedic Surgeries. Manohar Panneer , Prakash Murugaiyan , Sufala Viswas Rao PMID: 28298775 PMCID: PMC5341633 DOI: 10.4103/0259-1162.183157