Effect of Intrathecal Clonidine on Postoperative Analgesia in Pregnant Patients

INTRODUCTION: “For all the happiness mankind can gain is not in pleasure, but in rest from pain” - John Dyrden. The relief of pain during surgery is the raison d’etre of anaesthesia. Pain is a fundamental biological phenomenon. The aim of anaesthesiology as a science is the removal of pain temporarily, started initially with pain relief for surgeries, and now extends to post operative pain relief, relief of chronic pain, and cancer pain. Effective post operative analgesia reduces post operative morbidity, allows early ambulation and discharge. Post operative analgesia is achieved by various techniques using various drugs among which neuraxial blockade plays an important role. The accidental entry of corning’s needle in 1885, in to the subarachnoid space paved the way for the greatest leap into spinal anaesthesia. His words “Be the destiny of this observation, what it may, has seemed to me on the whole worth recording..,” opened the prologue. The word spinal anaesthesia was coined by him. AIM OF THE STUDY: 1. To evaluate the efficacy of Clonidine in prolonging the duration of post operative analgesia when combined with Bupivacaine. 2. To study the property of Clonidine to potentiate the analgesic effect of Bupivacaine. 3. To observe the safety of intrathecally administered Clonidine. MATERIALS AND METHODS: Study design: This study was a randomized prospective comparative study. Study setting and population: After obtaining institutional ethical committee clearance, the study was carried out on 70 patients in the OT, Department of Anesthesiology, Tirunelveli Medical College, Tirunelveli, from April to August 2009. Inclusion criteria: Pregnant patients belonging to ASA I and II were randomly selected between 18 to 28 years of age, and weighing between 45-70 kgs. Exclusion criteria: 1. Patients with systemic illness like diabetes, hypertension, 2. Asthmatic, COPD, 3. PIH, Patients on anti-hypertensives, 4. Patients with partial block or failed block, 5. Height less than 145 cm, 6. Procedures ending with hysterectomy or requiring blood transfusion, 7. Anemia, bleeding disorders, 8. Contraindication to Clonidine, 9. Patients with psychiatric problems, 10. Patients having spinal deformities. PRE OPERATIVE EVALUATION: In all the patients, Age, I.P.No, Body Weight, Baseline vital parameters were recorded. History regarding previous anaesthesia, surgery, any significant medical illness, medications and allergy were recorded. Complete physical examination and Airway assessment were done. Following laboratory investigations were done: 1. Hemoglobin %, 2. Blood : sugar, urea, S. Creatinine, 3. S. Electrolytes : Na+, K+, 4. ECG in all leads. STUDY METHOD: After getting, informed consent, the patients were randomly allocated into two groups. Group ‘B’ (n = 35) was taken as Bupivacaine group and Group ‘C’ (n = 35) as Clonidine group. The 10 point visual analogue pain scale VAPS was explained to the patients. All the patients were premedicated with Inj. metoclopramide 10mg i.v, and Inj. ranitidine 50mg i.v 1 hour prior to anaesthesia. Standard monitoring was instituted after shifting the patient on the operating table. Baseline measurements of pulse rate, blood pressure and SpO2 were recorded. An intravenous access was established and the patients were pre-loaded with ringer lactate 10ml/ kg. They were then positioned in the right lateral position on a horizontal table. After strict aseptic precautions, the L3-L4 inter space was identified and a 23 gauge spinal needle was used for sub-arachnoid placement. 0.5% hyperbaric bupivacaine 10 mg was injected in B group and 0.5% hyperbaric bupivacaine 10 mg + clonidine 75μg was injected in C group. The patients were then turned supine and a wedge placed under the right buttock. The level of sensory blockade was assessed by pin prick and the surgery proceeded after adequate motor and sensory block were achieved. The pulse rate and blood pressure were monitored at an interval of every 2 min till the delivery of the baby and every 5 minutes thereafter. A fall of MAP by 25% from the base line value was considered as hypotension and managed with intravenous fluids, oxygen and Inj. ephedrine in titrated incremental doses. STATISTICAL ANALYSIS: The clinical trial clients had been matched for comparison in respect of their age and body weight by computing mean and SD. The significance of the mean ages was interpreted by UNPAIRED‘t’ test. Duration of pain relief, two segment regression and the hemodynamics like MAP, PR, SPO2 were measured at different time periods and compared between the ‘B’ and ‘C’ group by mean and SD and interpreted by students unpaired ‘t’ test. The above statistical procedures were undertaken by SPSS (130) at 5% level of significance (P = 0.05). The clients were matched in respect of their age and weights for comparison of the effect of two drugs (B and B+C) since the two variables were termed as independent variables and which were responsible for the pain relief. SUMMARY: The addition of 75 μg Clonidine to Bupivacaine produced a strong analgesia with a mean duration of 288 minutes (4 – 6 hrs). This extended analgesia offered by the studied dose was clinically and statistically significant, at the same time providing hemodynamic stability. The arousable sedation offered by the intrathecal administration of clonidine was also beneficial, requiring less and infrequent supplementation of systemic analgesics. Moreover, the side effects observed were no greater than that of administration of bupivacaine alone. In fact respiratory depression, urinary retention or pruritus were not even noted in any case, which otherwise would have been an embarrassing side effect of intrathecal opioid. CONCLUSION: The present study has demonstrated that addition of 75 μg Clonidine to hyperbaric Bupivacaine prolongs post op analgesia and the two segment regression after Caesarean section, without clinically significant haemodynamic derangements or any adverse effects. Hence intrathecal clonidine along with bupivacaine proves to be a safer alternative to intrathecal opioids and with a dose of 75 μg, the hemodynamic profile is also very acceptable. Thus intrathecal clonidine 75 μg not only potentiates and prolongs the analgesic effect of bupivacaine, but also has a good safety profile for intrathecal use. From this study it could be concluded that addition of 75μg of Clonidine to hyperbaric Bupivacaine is safe and beneficial to pregnant patients posted for LSCS