European Journal of Cardiovascular Medicine

Spinal anaesthesia is a safe, reliable, and inexpensive technique with the advantage of providing surgical anaesthesia and prolonged post-operative pain relief and it also blunts autonomic, somatic, and endocrine responses to surgical stimuli.¹

The subarachnoid block is among the most versatile regional block available today. It is a very old and well-established anaesthetic technique that is simple to perform and has a high success rate and a good safety profile. It has emerged as a viable alternative to general anaesthesia for a variety of infraumbilical, perineal, and lower limb surgeries.² 

Till recently 0.5% hyperbaric bupivacaine was the only drug used for spinal anaesthesia in India after discontinuation of lidocaine. In 2009, a newer local anaesthetic, Ropivacaine another aminoamide with less cardiotoxicity and CNS toxicity than bupivacaine has been introduced in India. Ropivacaine is unique amongst this group in that it is prepared for clinical use as the pure S-enantiomer rather than a racemic mixture. It is long-acting amide local anaesthetic agent, eliciting nerve block via reversible inhibition of sodium influx in nerve fibres. The advantage of Ropivacaine is that it produces less motor block when used in lower doses and can be very useful for ambulatory surgeries and also has a better safety profile in terms of cardiac and CNS toxicity.³

Knowledge and use of adjuvant drug therapy have rendered neuraxial analgesia more effective in the management of both acute and chronic pain conditions. Αlpha-2 adrenergic agonists have both analgesic and sedative properties when used as an adjuvant in regional anaesthesia. ⁴

Dexmedetomidine is a highly selective α2 agonist with 8 times greater affinity than clonidine. Intrathecal alpha-2 receptor agonists have antinociceptive action for both somatic and visceral pain.⁴   

It is known from previous studies that the addition of 5mcg of Dexmedetomidine as an adjuvant to 0.75% Ropivacaine provides a very good quality of hemodynamic stability and has excellent quality of post-operative analgesia with minimal side effects. This study has been planned to compare post-operative analgesia in patients undergoing elective lower limb orthopaedic surgeries under subarachnoid block who will receive either plain isobaric Ropivacaine (0.75%) or isobaric Ropivacaine (0.75%) with 5mcg of Dexmedetomidine as an adjuvant.

 OBJECTIVES

To determine the effects of intrathecal Dexmedetomidine (5mcg) as an additive to isobaric Ropivacaine 0.75% in patients undergoing elective lower limb orthopaedic surgeries concerning the following parameters.

Objectives:

1. Onset of sensory blockade (T10 dermatome)
2. Time to peak sensory block 
3. Onset and duration of motor blockade 
4. Duration of analgesia.

Source of data-

Patients admitted to Mandya Institute of Medical Sciences for elective lower limb orthopaedic surgeries

Study setting:

Department of Anaesthesiology at Mandya Institute of Medical Sciences, Mandya

Study design:

A double-blind randomized control trial.

Study duration:

The study was conducted over 12 months from May 2020 to April 2021

 Sampling method:

A prospective randomized double-blind study.

A total of 60 patients was allotted into two groups of 30 each(n=30).

Odd numbers (1,3,5,…) will be in Group R

Even numbers (2,4,,6,…) will be in Group RD

Group-R: Ropivacaine (0.75%) 22.5mg (3ml) with 0.5 ml of normal saline (Total volume-3.5ml)       

Group-RD: Ropivacaine (0.75%) 22.5mg (3ml) with Dexmedetomidine 5 mcg. (Total volume-3.5ml)

The patients were included in the study by applying the following inclusion and

exclusion criteria.

Inclusion Criteria:

1) All patients who are posted for elective lower limb orthopaedic surgeries and were willing to give informed consent

2) Age group 18 to 60 years of either sex

3) American Society of Anaesthesiologists (ASA)physical status grade I (normal healthy individuals) and grade II (patients with mild systemic diseases with no functional limitation eg. well-controlled diabetes mellitus with no complications). 

Exclusion Criteria:

1) Patients with morbid obesity (Body Mass Index (BMI) > 40 kg/m2)

2) Patients shorter than 150 cm and taller than 180 cm height

3) Patients posted for emergency surgeries

4) Patients with allergy to study drugs

5) Patients taking alpha-adrenergic receptor antagonists, calcium channel blockers and angiotensin-converting enzyme inhibitors

6) Patients having any absolute contraindications for spinal anaesthesia like increased intracranial tension, severe hypovolemia, history of bleeding diathesis, and local infection.

Method of collection of data:

After obtaining informed written consent from patients, sixty patients belonging to ASA I or II aged between 18-60 years scheduled for elective lower limb orthopaedic surgeries were enrolled in the study after a pre-anesthetic check-up. All patients were preloaded with 15ml/kg of Ringer’s Lactate solution via an 18-gauge IV cannula in the dorsum of the hand. Standard anaesthesia monitoring was used, including Non-invasive arterial blood pressure (NIBP), Electrocardiography (ECG), Heart rate (HR), and peripheral arterial oxygen saturation (SpO2). With the patient in a sitting position, spinal anaesthesia was performed at the level of L3-L4 or L4-L5 through a midline approach using a 23-gauge Quincke spinal needle with the bevel pointing laterally.

Patients were allotted into two groups of thirty each (n=30): - Group R and Group RD.

Group R received 22.5mg (3ml) of isobaric Ropivacaine (0.75%) with 0.5 ml of normal saline (total volume-3.5ml)

Group RD received 22.5mg (3ml) of isobaric Ropivacaine (0.75%) with 5 µg of Dexmedetomidine (1ml -50mcg of Dexmedetomidine is added to 4ml of normal saline to make it 5ml. From this 5ml, 0.5ml- 5mcg is added to 3ml of Inj. Ropivacaine 0.75% to get a total volume of 3.5ml)

Injections were made over 15-20 seconds. Patients and attending Anaesthesiologist were blinded to the study. Thereafter, patients were placed in a supine position for surgery. The patient’s sensation to pinprick and motor power were examined. Heart rate (HR), Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP), and Arterial Oxygen Saturation (SpO2) were monitored at specific intervals throughout the procedure. The sensory block level was assessed using the loss of sensation to pinprick along the midclavicular line bilaterally and the higher level was used for statistical purposes if the levels are not the same bilaterally. The motor block was assessed using modified Bromage scale (0- No motor block, 1- Inability to raise extended leg; able to move knees and feet, 2- Inability to raise extended leg and move knee; able to move feet, 3-Complete block of motor limb). The time to reach the T10 dermatome sensory block was recorded before surgery. Sedation was assessed using Ramsay Sedation Scale (RSS) (1- Anxious, agitated or restless, 2- Co-operative, oriented and tranquil, 3-Responds to command, 4-Asleep, but has a brisk response to a light glabellar tap or loud auditory stimulus, 5-Asleep, has a sluggish response to a light glabellar tap or loud auditory stimulus 6-Asleep, no response). Intravenous midazolam was allowed in increments of 1mg after the block if the patient was anxious. Visual Analog Scale was recorded for up to 8 hours to assess the adequacy of analgesia. The time from intrathecal injection to two dermatomes sensory regression and motor block regression to modified Bromage 0 was recorded. All durations were calculated in relation to the time of spinal injection. Rescue analgesia consists of iv fentanyl 25 mcg which was given when Visual Analogue Scale ≥5, that was repeated 2nd hourly if needed.

FIGURE 1: VISUAL ANALOGUE SCALE

         Occurrence of hypotension, bradycardia, nausea, vomiting, pruritus, respiratory depression were noted throughout the study duration. Hypotension was treated with intravenous fluids and boluses of 6mg intravenous Mephentermine if needed. Bradycardia was treated with boluses of 0.3- 0.6 mg intravenous Atropine. Respiratory depression (Respiratory rate <8/min or SpO2<95%) was treated with oxygen supplementation and respiratory support if required.

The following parameters were observed and recorded

Duration of analgesia – Time from the injection of a drug to the first request for rescue analgesia.

The onset of the sensory blockade – Time from the injection of a drug to the loss of pinprick sensation at T10 dermatome.

Time for maximum sensory block- Time from the injection of a drug to the time taken for the maximum sensory blockade to be attained.

Onset of the motor blockade – Time from the injection of a drug to attainment of modified Bromage scale 1.

Duration of motor block – Time taken from the onset of motor block till the patient attains complete motor recovery (modified Bromage 0)

Time for two-segment regression of sensory blockade- Time taken for the sensory blockade attained to regress to two lower sensory dermatomal levels.

Quality of sensory block- loss of sensation to pinprick and touch  

Sample size estimation:

Where,

• n - required sample size; the value
• Z1-α/2 - standard normal distribution for a 95% CI
• σ is the expected SD
• d is the precision

According to the previous study conducted by Shah A et al, the mean onset of sensory block was 4.8 minutes with Dexmedetomidine as an adjuvant to intrathecal Ropivacaine 0.75%. Using the above-mentioned formula, the sample size came out to be 23 in each group. We have taken our sample size as 30 in both groups.  

Statistical analysis:

All data were entered in Excel sheet and analysed using the SPSS (Statistical Package for the Social Science) software. Continuous data were represented as mean +/- standard deviation and categorical data were represented as absolute numbers and percentages. Intergroup comparison of demographic data, duration of sensory and motor block and duration of analgesia, values was carried out by Student’s t-test.

Table 1: Time of Onset of Motor Block (Min)

p values calculated using two independent sample Student’s t-test

Table 1 shows the mean for onset of motor blockade among the two groups. Distribution is statistically similar in two groups.

Table 2: Time for Maximum Motor Block (Min)

p values calculated using two independent sample Student’s t-test

Table 2 shows the mean time for maximum motor block in both the groups. There is no statistically significant difference in both the groups in relation to time taken for maximum motor block (p value= 0.704)

Table 3: Time of Onset of Sensory Block at T10 Dermatome (Min)

p values calculated using two independent sample Student’s t-test

Table 3 shows the mean time for sensory onset at T10 dermatome in both the groups. There is no statistically significant difference in both the groups in relation to the time for sensory onset at T10 dermatome (p value= 0.228)

Table 4: Time for 2 Segment Regression (Min)

p values calculated using two independent sample Student’s t-test

Table 4 shows the meantime taken for 2 segment regression in both the groups. The mean time taken for 2 segment regression is 115.70±17.36 mins in Group RD and 79.47±17.38 mins in Group R. There is a statistically significant difference between the two groups regarding the time taken for 2 segment regression. (p<0.001).

Table 5: Grades of Motor Blockage

p values calculated using two independent sample Student’s t-test

Tables 5 showing grades of motor blockade in both the groups.

Table 6: Total Duration of Motor Block (Min)

p values calculated using two independent sample Student’s t-test

Table 6 shows the mean total duration of motor block among both the groups. The mean total duration of motor block in Group RD is 327.67±45.16 min and in Group R is 189.50±22.45 min. There is statistically significant difference in the total duration of motor block between both the groups (p value <0.001).  

Table 7: Total Duration of Analgesia (Min)

p values calculated using two independent sample Student’s t-test

Table 7 shows the mean total duration of analgesia in between 2 groups. The mean total duration of analgesia in Group RD is 379.50±57.27 and in Group R is 225.17±29.11. There is statistically significant difference among the groups with a p value of <0.001.

Table 8: VAS Scores- Post Operation

p value calculated using Mann-Whitney U Test.

Table 8 shows the median VAS score at 2 hours, 4 hours, 6 hours and 8 hours in post- operative period. There is significant statistical values with respect to VAS score upto 6 hours in post- operative period with Group RD having less VAS score when compared to Group R. But the VAS score at 8 hours in both the groups are comparable.

Spinal anaesthesia is the most versatile type of regional anaesthesia with a very high success rate as it is easy to perform and has a very good outcome. Till recently Bupivacaine 0.5% heavy was the only drug used for spinal anaesthesia after the discontinuation of Lidocaine in intrathecal use. Ropivacaine is the first single enantiomer-specific compound, which has a reduced risk of cardiotoxicity, neurotoxicity, and rapid recovery of motor function. Ropivacaine is available as 0.75% isobaric and 0.5% isobaric for intrathecal anaesthesia and 0.2% for infiltration anaesthesia. Many studies prove that Ropivacaine can be efficiently used in lower limb orthopaedic surgeries when used intrathecally⁵. The use of adjuvants like alpha 2 agonists and opioids is known to prolong the duration of the block with good postoperative analgesia. 

A study entitled “Effects of intrathecal dexmedetomidine as an additive to isobaric ropivacaine in patients undergoing elective lower limb orthopaedic surgeries” was undertaken in Mandya Institute of Medical Sciences, Mandya from May 2020 to April 2021. This study aimed to evaluate the effects of intrathecal dexmedetomidine as an adjuvant to isobaric Ropivacaine in lower limb orthopaedic surgeries in terms of onset of the sensory blockade at T10 dermatome, onset and duration of motor block, time for two-segment regression and duration of analgesia. 

Drug selected for the study 

In our study, the drugs used were Ropivacaine and Dexmedetomidine. Ropivacaine is a shorter-acting local anaesthetic agent with a better safety profile. If its duration of action is prolonged with the addition of suitable adjuvants, then it can be a good alternative to Bupivacaine. The use of alpha 2 receptor agonist as an adjuvant to the local anaesthetic agent is very popular. Dexmedetomidine, a selective alpha 2 receptor agonist has an eight-fold affinity to alpha 2 receptors with respect to clonidine. Previous studies ^4,6,7 have shown that Dexmedetomidine can be effectively used as an intrathecal additive to the local anaesthetic agent with excellent post-operative analgesia and hemodynamic stability. Hence, we have used Dexmedetomidine as an adjuvant to intrathecal Ropivacaine.

Dose of the drug selected:

A previous study ⁸ was conducted to study the pharmacology of Ropivacaine and concluded that it is a well-tolerated regional anaesthetic agent with good surgical anaesthesia with efficacy similar to that of bupivacaine and levobupivacaine for peripheral nerve blocks but has a lower propensity for the motor blockade, and reduced potential for CNS toxicity and cardiotoxicity.

According to the study conducted by Van Kleef et al.⁹ Ropivacaine, 0.75% 3ml (22.5 mg) isobaric provided the most satisfactory conditions for lower limb surgery.

Shaheena Parveen et al.,³ conducted a study to estimate the minimum effective local anaesthetic dose of Ropivacaine among patients undergoing lower limb orthopaedic surgeries and they concluded that the minimum effective dose of intrathecal Ropivacaine was around 20mg and ED 50 was 15mg and ED95 was 20mg. Hence, we have used 22.5mg of Ropivacaine in our study.

Abd Elhamid B M et al., ¹⁰ compared 3 different doses of intrathecal Dexmedetomidine and their effect on the duration of spinal anaesthesia and they concluded that dexmedetomidine can prolong the duration of analgesia with a high safety profile without complications in both 3mcg and 5 mcg doses but not with a dose of 1.5 mcg. Many other similar studies conducted using 5mcg of Dexmedetomidine proved the efficacy of the drug when used intrathecally.^4,6,7

Therefore, we have used 5mcg of Dexmedetomidine as an intrathecal adjuvant to Ropivacaine in our study.

Type of surgeries selected for the study:

According to Greene N et al.,¹¹ isobaric local anaesthetic agents can be used for surgeries below T10 block and high volumes are required for surgeries above T10 level. Hence we have selected elective lower limb orthopaedic surgeries which require T10 dermatome level block as the local anaesthetic of choice in our study is isobaric 0.75% Ropivacaine.

Sensory blockade:

The onset of sensory block:

The sensory block level was assessed using the loss of sensation to pinprick

along the midclavicular line bilaterally at T10 dermatomal level. In our study onset of sensory block was taken as the time lapse between drug administration and loss of sensation to pinprick at T10 dermatome which was tested by hypodermic needle. The results in our study were observed to be 7.50 ± 2.71 min in Group RD and 8.20 ± 1.56 min in Group R. There was no statistically significant difference in both the groups concerning the time for onset of sensory block at T10 dermatome (p value= 0.228).

Sule M P et al.,²conducted a study where they compared intrathecal 0.75% Ropivacaine and 0.5% Bupivacaine among 60 adult patients undergoing lower limb orthopaedic surgeries. In their study, the onset of sensory block was observed to be 9.4±2.63 min in the isobaric 0.75% Ropivacaine group which was nearly close to our results.

Nitish Kumar Parmar et al.,⁶  observed that the onset for the sensory block at T10 level was attained at 4.03±0.69 min in Group Ropivacaine with Dexmedetomidine and 3.96± 0.64 min in Group Ropivacaine among 120 patients undergoing vaginal hysterectomy. The onset of sensory block obtained in their study was earlier as compared to the results of our study but were statistically insignificant between the two groups. This difference in the attainment of onset of the sensory block might be due to demographical characteristics.  

Maximum Sensory Level 

We can achieve T 10 dermatome level block with isobaric local anaesthetic agents. But in our study, the level of maximum sensory blockade achieved was T6 dermatome in both the groups.

The maximum sensory level achieved in the study conducted by Nitish Kumar Parmar et al was also T6 dermatome level which was similar to our study as they have used the same dosage of Ropivacaine and Dexmedetomidine like we have used in our study. 

But, in the study conducted by Tailam et al, the level of sensory block was T6 in 24 (48%) of subjects, T4 in 17 (34%) of subjects, T8 in 6 (12%) and T2 in 3 (6%) of subjects.⁴ This difference in the level of sensory blockade attained might be due to differences in demographic characteristics.  

Two segment regression 

We observed that the two-segment regression occurred at 115.70 ± 17.36 mins in Group RD and at 79.47 ± 17.38 mins in Group R. There was a statistically significant difference (p< 0.001) in time taken for two-segment regression between both the groups with slower regression in Group RD. This difference in the regression is due to the addition of Dexmedetomidine, a selective α2 receptors agonist which can prolong the duration of sensory blockade when used intrathecally.

Similar results were obtained in the study conducted by Nitish Kumar Parmar et al in which the two-segment regression was observed to be 117.00 ± 15.65 min in Group plain Ropivacaine and 172.37±18.97 min in Group Ropivacaine with Dexmedetomidine.⁶

In another study conducted by Alka Shah et al., the two-segment regression was attained at 125.6 ± 16 minutes which was similar to our study and so was with the study conducted by Tailam et al., where the two segment regression occurred at 128.4 min. ^{4, 12}

Duration of analgesia

We observed that there was a statistically significant difference among the groups concerning the duration of analgesia. The duration of analgesia obtained in Group RD was 379.50±57.27 minutes and in Group R was 225.17±29.11 minutes with a p-value of <0.001.

Nitish Kumar Parmar et al., observed that among 120 female patients who underwent vaginal hysterectomies, the duration of postoperative analgesia was significantly greater in Group D (Ropivacaine 0.75% with 5mcg of Dexmedetomidine) 270.00±38.75 min as compared to group R (plain isobaric 0.75% Ropivacaine) 174.77±22.31 min which correlated with our study results. ⁶

In a similar study conducted by Tailam et al., the duration of analgesia was 400 min ± 58min when 5mcg of Dexmedetomidine was used as an intrathecal adjuvant.⁴ The prolonged duration of analgesia as compared to our study might be due to demographical differences. 

Shah A, et al.¹² found that the analgesic effect of intrathecal Ropivacaine was potentiated by adding intrathecal Dexmedetomidine. 5 micrograms of intrathecal Dexmedetomidine prolonged the postoperative analgesic effect of Ropivacaine by approximately 8 hours which was similar to our findings.

 Gupta R et al.,¹³ observed that the duration of analgesia was significantly prolonged when dexmedetomidine was added to Ropivacaine (478.4±20.9 minutes) as compared to plain Ropivacaine (241.67±21.67 minutes) which also correlated with our findings.

The mechanism of action of local anaesthetics is by blocking sodium channels, whereas the alpha-2 adrenoceptor agonist acts by binding to pre-synaptic C-fibres and post-synaptic dorsal horn neurons. The analgesic action of intrathecal alpha-2 adrenoceptor agonist is by depressing the release of C-fibre transmitters and by hyperpolarisation of post-synaptic dorsal horn neurons.¹⁴ This antinociceptive effect may explain the prolongation of the sensory block when added to spinal anaesthetics. 

Motor blockade 

Motor block onset

The onset of motor blockade observed in our study was attained at 2.80±1.65 min in Group RD and 2.95± 0.87 min in Group R which was statistically insignificant between the two groups with a p value = 0.652.

In the study conducted by Tailam et al.,⁴ the onset of motor blockade was attained at 10.12 ±2.89 min which was comparatively slower than in our study group. This delay in onset of motor block is due to the difference in defining the onset of the motor block as they have considered the onset of the motor block as the time lapse between drug administration and attainment of Bromage 3 scale. Whereas we have considered the onset of the motor block as the time lapse between drug administration and attainment of modified Bromage 1 scale.

Maximum motor blockade:

We have defined maximum motor blockade as the time from the administration of injection into the subarachnoid space to the attainment of Bromage 3 in our study and observed that maximum motor block was attained at 5.34 ±2.44 min in Group RD and 5.54±1.50 min in Group R. 

 In the study conducted by Nitish Kumar Parmar et al., the maximum motor blockade was 5.46 ± 0.91 min in Group R and 5.54±0.85 min in Group D which was similar to the results of our study.⁶

Duration of motor block:

The duration of motor block in Group RD is 327.67±45.16 min and in Group R was 189.50±22.45 min. There is a statistically significant difference in the total duration of motor block (p value <0.001). The prolongation of the motor block of spinal anaesthetics may result from the binding of alfa-2 adrenoceptor agonists to motor neurons in the dorsal horn.^15,16

Tailam et al., observed that the duration of motor blockade was 350±50.4 min when 5mcg of dexmedetomidine was added to isobaric 0.75% Ropivacaine.

In the study conducted by Nitish Kumar Parmar et al.,⁶ the duration of motor blockade was observed to be 229.37 ± 28.74 min in Group R and 258.55±30.46 min in Group RD which was nearly close to the results of our study. 

VAS score: 

In our study, the median VAS score at 2 hours, 4 hours and 6 hours are statistically significant with p value <0.001. This can be explained due to the addition of 5mcg of Dexmedetomidine to intrathecal isobaric 0.75% Ropivacaine. But VAS score at 8 hours post-operative period among both the groups is comparable which indicated that the addition of 5mcg of dexmedetomidine to intrathecal isobaric 0.75% Ropivacaine provided analgesia up to 8 hours in the post-operative period.  

SUMMARY

A prospective randomised control double-blind study was conducted to assess the efficacy of 5 mcg of Dexmedetomidine as an intrathecal adjuvant to 0.75% isobaric Ropivacaine in 60 patients undergoing elective lower limb orthopaedic surgeries. They were randomised into Group-R patients received Ropivacaine (0.75%) 22.5mg (3ml) with 0.5 ml of normal saline (Total volume-3.5ml), Group-RD patients received Ropivacaine (0.75%) 22.5mg (3ml) with Dexmedetomidine 5 mcg. (Total volume-3.5ml). All patients were preloaded with 15ml/kg of Ringer’s Lactate solution via an 18-gauge IV cannula in the dorsum of the hand. Standard anaesthesia monitoring was used. With the patient in a sitting position, spinal anaesthesia was performed at the level of L3-L4 or L4-L5 through a midline approach using a 23-gauge Quincke spinal needle with the bevel pointing laterally. Thereafter, patients were placed in a supine position for surgery. Heart rate (HR), Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP), and Arterial Oxygen Saturation (SpO2) were monitored at specific intervals throughout the procedure. The patient’s sensation to pinprick and motor power was examined. The sensory block level was assessed using the loss of sensation to pinprick along the midclavicular line bilaterally at the T10 dermatome level. The motor block was assessed using a modified Bromage scale. The time to reach the T10 dermatome sensory block was recorded before surgery.  The time from intrathecal injection to two dermatomes sensory regression and motor block regression to modified Bromage 0 was recorded. 

The onset of sensory blockade, time for maximum sensory block, the onset of motor blockade, duration of motor blockade, time for two-segment regression of sensory blockade, and duration of analgesia were recorded. Occurrence of hypotension, bradycardia, nausea, vomiting, pruritus, respiratory depression was noted throughout the study duration.

Data were tabulated and analysed using SPSS software version 24. The qualitative data between the two groups were compared using the Chi-Square test and for comparison of the continuous variable independent t-test was used.

Table 9 - The following table shows the statistically significant results obtained in the present study

Demographic data in both the groups were not statistically significant. 

The mean total duration of sensory blockade obtained in Group RD was 374.67±50.50 min and in Group R was 217.17±25.62 min with a significant p value (<0.001). The mean total duration of motor block observed in Group RD was 327.67±45.16min and in Group R was 189.50±22.45 min. There was a statistically significant difference in the total duration of motor block (p value <0.001).  

The duration of analgesia obtained in Group RD was 379.50±57.27 minutes and in Group R was 225.17±29.11 minutes with a p value of <0.001. Hemodynamic stability was maintained throughout the intraoperative and postoperative period. Adverse effects were minimal and did not require any intervention in both groups. 

 Limitations of our study -:

Since our study was conducted on ASA I and II patients, the efficacy and pharmacokinetics of the study drugs could not be assessed in high-risk patients and patients undergoing emergency surgeries. Clinical trials are yet to be done to establish the effects of our study drugs among these patients.

Dexmedetomidine, when used as an additive to intrathecal 0.75% isobaric Ropivacaine, produced prolonged duration of analgesia and also extended duration of motor blockade which is not desirable for patients. Ropivacaine, known for its lesser motor blockade characteristics, on contrary, had a prolonged duration of motor blockade due to the addition of dexmedetomidine.     

 And the use of normal saline to isobaric ropivacaine can change the baricity of the local anaesthetic solutions which can cause delayed effects of the drugs

Our study revealed that 5mcg dexmedetomidine when used as an intrathecal additive to isobaric 0.75% Ropivacaine for elective lower limb orthopaedic surgeries-

• prolonged the duration of sensory blockade,
• prolonged the motor blockade
• extended the duration of analgesia

Hence our study can be evidence to prove that low dose Dexmedetomidine (5 mcg) can be used effectively and safely as an appealing choice, as an intrathecal adjuvant to isobaric Ropivacaine 0.75 % in surgical procedures like lower limb orthopaedic surgeries.

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