Current status and future prospects of anesthesia in patients undergoing total knee replacement surgery

Background: The armamentarium of local anesthetic adjuvants have evolved overtime from classical opiods to a wide array of drugs spanning several groups and varying mechanism of action, to avoid intra operative visceral and somatic pain, and to enhance post operative analgesia. Clonidine, an alpha 2 adrenergic agonist, has a variety of actions, including potentiating the effects of local anaesthetics. The aim of this study was to evaluate the differences in onset and duration of sensory and motor block, hemodynamic effects, post operative analgesia, and adverse effects of fentanyl versus clonidine when given intrathecally along with hyperbaric 0.5% bupivacaine in pateints undergoing total knee replacement (TKR). Method: After approval from the institutional ethics committee and written informed consent from patient, 80 patients in the age group of 55-75 in ASA grade I and II undergoing elective total knee replacement surgeries were enrolled for the study. Patients were randomly allocated in two groups, group fentanyl (F) and group clonidine (C). Group F received bupivacaine 0.5% 3 ml, mixed with 25ug fentanyl to a total volume of 3.5 ml and group C received bupivacaine 0.5% 3ml with clonidine 50 ug . Statistical analysis were done using SAS 9.2, SPSS 15.0, Stata 10.1, medCalc 9.0.1 systat 12.0 and R environment Ver 2.11.1. Results: Mean duration of motor block was significantly higher in group C (411.55± 82.38) as compared with group F (237.73±59.91). Significant difference in duration of sensory block was noted between group C (462.28±82.74) and group F (251.45±51.87). Duration of post operative analgesia was significantly longer in group C as compared to group F (mean duration of first request to rescue analgesia). In either of the groups we did not observe any side effects i.e bradycardia or hypotension, either during or after anesthesia that required intervention. Conclusions: Intrathecal clonidine is associated with prolonged motor and sensory block, hemodynamic stability and reduced need for rescue analgesia in 24 hours as compared to fentanyl.