EFFECT OF ADDING DEXMEDETOMIDINE vs FENTANYL TO INTRATHECAL BUPIVACAINE ON SPINAL BLOCK CHARACTERISTICS IN GYNECOLOGICAL PROCEDURES: DOUBLE BLINDED CONTROL STUDY

INTRODUCTION: Spinal Anaesthesia is used extensively for lower abdominal and lower extremity surgeries, because it has distinct advantages over general Anaesthesia. Lignocaine and Bupivacaine are the commonly used local anesthetic agents for spinal anesthesia. The adjuvants like opioids and α2 agonist are sometimes combined with Local anaesthetic for spinal anaesthesia. The rationale for combining adjuvants to local anaesthetic drugs is to lower the dose of each agent, and maintaining analgesic efficacy whilst reducing the incidence and severity of side effects. Surgery on the uterus and other genital organs performed under spinal or epidural block is often accompanied by visceral pain, nausea and vomiting. Fentanyl in various doses when added to spinal Bupivacaine increase the duration of analgesia and reduce intra operative nausea and vomiting. Dexmedetomidine is a α2-agonist that is approved as an intra venous sedative and co-analgesic drug. Most of the clinical studies about intrathecal α2 adreno receptor agonist are related to clonidine. The present study was designed to evaluate the efficacy and adverse effects of 5μg Dexmedetomidine Vs 25μg of Fentanyl when added to 0.5% Hyperbaric Bupivacaine administered intrathecally in patients undergoing elective vaginal surgeries. AIM OF THE STUDY: To compare the effect of addition of Dexmedetomidine Vs Fentanyl to 0.5% Hyperbaric Bupivacaine administered intrathecally for vaginal surgeries with respect to • Time to onset of sensory and motor block. • Duration of sensory and motor block. • Quality of intra operative anaesthesia. • Time for demand analgesia. • Side effects. MATERIALS AND METHODS: This study was conducted at the Kasturbai Gandhi memorial Government Hospital, Chennai-600 005 between June 2010 - August 2010 on 60 patients of ASA physical status I undergoing Elective adult surgical patient posted for vaginal wall repair & Vaginal Hysterectomy under subarachnoid block. This study was done after Government General Hospital Ethical committee approval and a written informed consent obtained from all the patients included in this study. Study Design: This study was done in a prospective double blinded randomized manner. Each group consisted of thirty patients. Group D: Patients in this group received 2.8 ml of 0.5% hyperbaric bupivacaine + 5μg [0.5 cc] of preservative free Dexmedetomidine to a total volume of 3.2 ml intrathecally. Group F: Patients in this group received 2.8ml of 0.5% hyperbaric bupivacaine + 25μg [0.5 cc] of Fentanyl to a total volume of 3.2ml intrathecally. The final volume of injected solution was 3.2ml in both groups. In this study 0.5% hyperbaric bupivacaine in 8% dextrose, Dexmedetomidine hydrocholoride 50μg/0.5ml and preservative free fentanyl 50μ/1ml. All solutions were prepared by the OT incharge anaesthesiologist under strict aseptic precautions, uninvolved in the administration of SAB or in the observation of results. Selection of Cases: Inclusion Criteria: • Patients in the age group of 30 and above undergoing elective vaginal hysterectomy and vaginal wall repair. • ASA physical status I. • Who have given valid informed consent. Exclusion Criteria: • Not statisfying inclusion criteria. • Contra indication to SAB. • Hypersensitivity to the study drug. • Renal or Hepatic dysfunction • Bleeding diasthesis • Uncontrolled labile Hypertension & Diabetes mellitus. SUMMARY: This double blinded prospective randomized controlled trial was designed to evaluate the onset and duration of sensory and motor block as well as operative analgesia and adverse effects of Dexmedetomidine vs fentanyl given intrathecally with heavy 0.5% Bupivacaine for spinal anaesthesia in patients scheduled for vaginal hysterectomy, vaginal wall repair patients receiving 25μg of fentanyl with 2.8cc of Bupivacaine intrathecally served as the control. The Following observations were made: • The addition of Dexmedetomidine significantly prolonged the duration of sensory and motor block. • The addition of Dexmedetomidine significantly prolonged the time for demand analgesia. • The addition of Dexmedetomidine intrathecally had no effect on the onset of sensory or motor block when compared with fentanyl. • The incidence of side effects was limited to the occurence of Hypotension, Bradycardia vomiting in the groups that received Dexmedetomidine intrathecally. • The incidence of pruritus were more in the groups that received fentanyl intrathecally. • The addition of Dexmedetomidine intrathecally had similar effect on sedation when compared to fentanyl. CONCLUSION: Intrahtecal Dexmedetomidine supplementation of spinal block seems to be a good alternative to intrathecal fentanyl since it produces prolonged sensory block and motor block. It is evident that this type of block may be more suitable for lower abdomen and lower extremities surgeries. A drawback of Dexmedetomidine supplemented spinal block characteristics is the increase in the duration of motor block which may not suit short term surgical procedures or ambulatory surgery.