Effect of Intrathecal Dexmedetomidine and Fentanyl as Adjuvant to Hyperbaric Bupivacaine for Orthopaedic Lower Limb and Lower Abdominal Procedures: A Double Blind Control Study

Aims and Objectives: The aim of this study is to evaluate the effects of Dexmedetomidine and Fentanyl as intrathecal adjuvant to Bupivacaine on the onset and duration of sensory and motor block in spinal anaesthesiain orthopaedic lower limb and lower abdominal surgeries. Materials and Method: Ninety patients of ASA status I and II posted for lower limb and lower abdominal surgery were randomly divided into three groups. Group D was administered Hyperbaric Bupivacaine 15mg + Dexmedetomidine 5μg in 0.5 ml normal saline,group F was administered Hyperbaric Bupivacaine 15mg + Fentanyl 25 μg in 0.5 ml normal saline and group C were administered Hyperbaric Bupivacaine 15mg plus in 0.5 ml normal saline.Duration and quality of sensory and motor block were assessed. Results: Sensory and motor block in group D patients were longer than group F and C patients. Conclusion: Intrathecaldexmedetomidine when added tobupivacaine heavy (0.5%)provide better and prolonged analgesia in comparison to fentanyl. Key word: Fentanyl, Orthopaedic, Bupivacaine,Intrathecal, Dexmedetomidine Access this article online Quick Response Code: Website: www.innovativepublication.com DOI: 10.5958/2394-4994.2015.00030.X INTRODUCTION Subarachnoid block is the most commonly used technique for orthopaedic lower limb and lower abdominal surgeries.Postoperative pain control is a major problem in these surgeries because of relatively short duration of action of local anaesthetics, so early analgesic intervention is needed in the postoperative period. A number of adjuvants, such as clonidine and midazolam, and opiods have been studied to prolong the effect of spinal aesthesia .Fentanyl, in recent years, has emerged as a useful intrathecal adjuvant for prolonging the effect of spinal anaesthesia. Although it is one of the most widely used intrathecal adjuvant in the present scenario, its intrathecal use has been shown to be associated with side effects like respiratory depression and pruritus. Dexmedetomidine, a new highly selective α2agonist, is under evaluation as a neuraxial adjuvant as it provides stable hemodynamic conditions, good quality of intraoperative and prolonged postoperative analgesia with minimal side effects By virtue of its effect on spinal α-2 receptors, dexmedetomidine mediates its analgesic effects. Based on earlier human studies, it has been shown that a low dose of 5 μg, dexmedetomidine provides a prolonged anaesthesia and good quality post operative analgesia when used as an intrathecal adjuvant to bupivacaine with minimal effects on the hemodynamic status of the patient. Hence, the present study is being undertaken to evaluate and compare the effects of dexmedetomidine and fentanyl as intrathecal adjuvants to bupivacaine. MATERIAL AND METHODS This study was carried out at SCB Medical College & Hospital, Cuttack after obtaining approval from the Hospital Ethical Committee and written informed consent from the patients from July 2014 to Feb. 2015. Ninety ASA grade I or II patients of either sex, aged 18 to 60 years, weighing 50 to 90 kg and with a height of 150 cm to 180 cm, scheduled for lower abdominal and lower limb surgery were included in the study. Exclusion criteria werePatients presenting with known contra indications to spinal anaesthesia, pregnant patients, Patients on therapy with adrenergic receptor antagonist, calcium channel blocker, and/or ACE inhibitor, with history of heart block or dysarrythmia, hypersensitivity to any of the study drugs, who refused to consent to be part of study. The study population was randomized using random number table generated from computer software. Random intervention assignment slip was placed in serially numbered opaque and sealed Sidharth Srabam Routray et al. Effect of IntrathecalDexmedetomidine and Fentanyl as Adjuvant to... Indian Journal of Clinical Anaesthesia, 2015;2(4):204-208 205 envelopes. These envelopes were opened following enrolment of the case. 90 total patients randomly divided into 3 groups (n = 30):Group D: Hyperbaric Bupivacaine 15mg + Dexmedetomidine 5μg in 0.5 ml normal saline administered intrathecally.Group F: Hyperbaric Bupivacaine 15mg + Fentanyl 25 μg in 0.5 ml normal saline administered intrathecally. Group B: Hyperbaric Bupivacaine 15mg plus 0.5 ml normal saline administered intrathecally. All the patients were kept for 6 hrs fasting prior to surgery. Tablet Alprazolam(0.25 mg) was given as a premedication a night prior to surgery. Preloading was done with Ringer lactate solution (10 ml/kg body weight). Routine monitoring including non invasive blood pressure (NIBP), ECG, heart rate and pulse oximetry was done. All patients received supplemental oxygen via mask (3l/min). Under proper aseptic conditions, spinal anaesthesia was given at the level of L3-L4 interspace in sitting position using a midline approach by a 25G Quincke spinal needle. The drug was injected slowly over 10-15 seconds with the bevel of the needle pointing upwards and all patients were made supine. The intrathecal drug formula was prepared by a separate anaesthesiologist under strict aseptic conditions. The anaesthesiologist who administered anaesthesia was blinded to the group allocation. After administering anaesthesia the vital signs of the patient were recorded. Vitals were recorded every 2 minutes up to the 10 minute and every 5 minutes thereafter up to 20 minutes. Beyond 20 minutes the vitals were recorded every 20 minutes till the time of discharge from PACU (Post Anaesthesia Care Unit).The sensory dermatome level was assessed by loss of pin prick sensation to a 23 G hypodermic needle. The motor dermatome level was assessed according to the Bromage Scale:  Bromage 0-Patient able to move hip, knee and ankle.  Bromage 1Patient unable to move hip, but able to move knee and ankle.  Bromage 2Patient unable to move hip and knee but able to move the ankle.  Bromage 3Patient unable to move hip, knee and ankle. The sensory and motor status was assessed prior to the spinal injection, then every 2 minutes after the spinal injection for the first 10 minutes, every 5 minutes for the next 10 minutes and thereafter every 20 minutes until the time to regression of sensory level to dermatome S2 and motor scale to bromage 0. Time to reach the sensory block up to highest dermatome level and motor block of bromage 3 level was noted. On achieving T8 sensory blocked level, the surgical procedure was carried out. Then time to regression to dermatome S2 level and time to reach bromage 0 was noted in post operative care unit.All durations were calculated taking the spinal injection time as time zero. If the sensory levels were not equal bilaterally the higher dermatome level was used for statistical analysis. Patient was discharged after the sensory block regresses to S2 level and motor block to bromage0. Postoperatively, the pain scoring was done by using visual analogscale (VAS) (0 = no pain, 10 = severe pain), with the vital recordings of the study until the patient was discharged. Paracetamol was given intravenous as rescue analgesia when VAS was greater than 4. Time of administering the first dose of rescue analgesia was noted.Sedation was assessed by using Modified Ramsay sedation score each time the vitals were noted. Modified Ramsay sedation scale: 1. Anxious, Agitated, Restless. 2. Cooperative, Oriented, Tranquil. 3. Responds to commands only. 4. Brisk response to light glabellar tap or loud noise. 5. Sluggish response to light glabellar tap or loud noise. 6. No Response. For the purpose of the study hypotension was defined as a decrease in systolic blood pressure more than 30% of the baseline value or fall below 90 mmHg, which was treated by Ephedrine 6 mg i.v. and fluids. Bradycardia was defined as heart rate less than 60/min but the intervention with iv atropine 0.6mg was done only when heart rate fell below 50/min. Side effects including nausea, vomiting, bradycardia, hypotension, pruritus, respiratory depression, urinary retention, shivering etc. were assessed both intra-operatively as well as postoperatively. All the patients were examined by the anaesthesiologist after 24 hrs of the spinal block and were assessed for anypostdural puncture headache or transient neurologic symptoms.Highest dermatomal level of sensory blockade, time taken to reach the highest dermatomal level of sensory block, to reach up to bromage 3 motor block, for sensory regression to S2 level, for motor regression to bromage 0 were noted.Hemodynamic status of the patient,sedation score and side effects if any were noted. All the statistical analysis was performed by using SPSS version 21. The various statistical tests that were used in this study were analysis of variance (ANOVA) test, Post hoc test (Bonferroni test) and nonparametric tests like Mann whitney U test and kruskalwallis test.For all statistical analysis p <0.05 was considered statistically significant. The results and interpretations are explained below. Sidharth Srabam Routray et al. Effect of IntrathecalDexmedetomidine and Fentanyl as Adjuvant to... Indian Journal of Clinical Anaesthesia, 2015;2(4):204-208 206 RESULT All the three groups were comparable as regard to age, sex, height and weight. There were no significant differences in heart rate, MAP, SPO2 between the three groups. Intergroup analysis showed a statistically significant difference in the highest level of sensory blockade amongst group D and F(p = 0.004), However no significant difference was found between group B and F and group D. Two segment regression time was more in dexmede-tomidine group in comparison to fentanyl and control group. Onset time to both sensory and motor block was faster on group D than group F and group B. Regression time of motor block to bromage 0 was slow and time to rescue analgesia was longer in dexmedetomidine group in comparison to other groups. Sedation score was more in dexmede-tomidine group in comparison to other group. VAS score was lower in dexmedetimidine group than other groups. In our study the incidence of bradycardia, hypotension, nasea, vomiting, pruritus and urine retention was not statistically significant. There was no incidence of respiratory depression. Table 1: Demographic profile Parameters Group B Group D Group F P value Age (years) 39.16±10.12 43.6±10.5 41.63±9.85 0.245 Sex(m:f) 20:10 19:11 17:13 0.548 Weight (kg) 66.87±7.20 66±7.82 64.83±7.50 0.577 Height (cm) 166.47±6.40 164.43±5.92 163.6±5.62 0.168 ASA(I:II) 21:9 18:12 20:10 0.641 Duration of surgery (min) 48±17.84 47.67±15.24 46.47±11.99 0.734 Table 2: Characteristics of spinal block Variable (min) Group B Group D Group F P value Time of onset of sensory block 8.2±1.6 8.0±1.5 8.3±2.1 0.235 Time of onset of motor block 9.5±2.3 9.3±2.7 9.7±3.2 0.124 Time taken to reach highest level of sensory block 10.4±4.01 9.33±3.50 10.67±3.65 0.346 Duration of sensory block 198.67±32.35 396.67±24.12 205.67±26.12 0.0001 Duration of motor block 140.67±21.32 338±21.24 154±19.76 0.0001 Duration of Spinal anesthesia 224.4±36.2 402.6±32.7 234.6±29.6 0.0001 Time to first dose of rescue analgesia 153.67±27.88 299±33.92 166.83±20.66 0.0001 Table 3: Highest dermatome level of sensory block