Comparison of intrathecal hyperbaric bupivacaine with isobaric levobupivacaine and isobaric ropivacaine with fentanyl as adjuvant in outpatient knee arthroscopy: A randomised controlled study

Study title: Comparison of intrathecal hyperbaric Bupivacaine with isobaric   Levobupivacaine and Ropivacaine with Fentanyl as adjuvant in outpatient knee arthroscopy: A randomized controlled study

Rationale: Knee arthroscopic procedures are commonly performed nowadays on an outpatient basis preferably under spinal anaesthesia. Local anaesthetic agent Bupivacaine produces a denser motor and sensory blockade and is associated with adverse effects like cardiac and CNS toxicity. Ropivacaine and Levobupivacaine are relatively newer agents which are less cardiotoxic than Bupivacaine and cause less motor blockade which helps in early ambulation and discharge. To prolong the duration of postoperative analgesia intrathecal adjuvant like fentanyl can also be added to them. The published data comparing the three agents is lacking, their effects will be compared with fentanyl as adjuvant in knee arthroscopic surgeries.

Aim: To compare the efficacy of intrathecal 0.5% hyperbaric bupivacaine, 0.5% isobaric levobupivacaine and 0.5% isobaric ropivacaine with fentanyl as intrathecal adjuvant in knee arthroscopic surgeries.

Objectives:

Primary:

·          To compare the time to ambulation and time to discharge.

Secondary:

·         To compare the time of onset, maximum level, time to achieve maximum level and duration of sensory blockade.

·         To compare the time of onset, intensity and duration of motor block.

·         To compare the duration of postoperative analgesia.

·         To compare the incidence of adverse effects.

Setting:  Department of Anaesthesiology & Critical Care, Guru Teg Bahadur (GTB) Hospital and University College of Medical Sciences (UCMS), Delhi.

Study Design: Randomized double blind controlled study.

Time frame: November 2014 to April 2016

Population/participants: ASA I and II patients between the age of 18-60 years and the height of 150-180 cm undergoing knee arthroscopy.

Sample size: 60 patients divided in three groups (BF, LF, RF) of 20 each.

Methods: Subarachnoid block will be performed, Group BF will receive 10 mg of 0.5% hyperbarc Bupivacaine, LF will receive 10 mg of 0.5% isobaric Levobupivacaine and RF will get 10 mg of 0.5% isobaric Ropivacaine with 25 µg of fentanyl. A total volume of 2.5 ml study drug solution will be injected intrathecally in all patients. Patients will be assessed for characteristics of spinal anaesthesia, hemodynamic parameters, pain score, side effects and home readiness will be determined using PADSS criteria.

Statistical analysis: For intra and intergroup comparison repeated measure of ANOVA, followed by Tukeys test. P-value (<0.05) will be considered as significant.

Outcome measures

Primary

The duration of spinal analgesia and time to ambulation and discharge following intrathecal administration of 0.5% hyperbaric bupivacaine, isobaric levobupivacaine and isobaric ropivacaine with fentanyl as adjuvant in knee arthroscopy.

Secondary

·         Time of onset & duration of sensory block, maximum level& time to achieve

·         Time of onset, duration and intensity of motor block

·         Postoperative pain assessment (VAS) and total analgesia required in first 24 hours in 3 groups.

Results

The demographic profile was found to be comparable among the three groups with respect to age, weight, height, gender, and duration of surgery. The mean time of onset of sensory block was significantly delayed in ropivacaine group(7.05±2.96 min) as compared to bupivacaine group(4.95±2.11 min) and levobupivacaine group(3.90±1.37 min).The mean time to achieve maximum sensory level was significantly earlier in levobupivacaine(7.50±1.46 min) group as compared to bupivacaine group(9.40±4.40 min) and ropivacaine group(10.35±3.48 min).Maximum level of sensory block achieved in ropivacaine group was significantly lower(T6 in 50% and T8or T10 in 50%) as compared to other two groups where it was T6 in maximum number of patients.The mean duration of sensory block was comparable among the three groups.The mean time(log) to maximum  motor blockade was significantly delayed  in ropivacaine group(0.912±0.18 min) as compared to other two groups.Maximum motor block was B2 in  maximum patients in ropivacaine group which was less intense than other two groups where it was B1 in maximum number of patients.The mean time to complete motor recovery was significantly earlier in ropivacaine group(204.75±34.39 min) as compared to bupivacaine(260±40.78 min) and lebvobupivacaine group(280.25±28.72 min).The mean duration of spinal analgesia was comparable among the three groups.The mean time to ambulation and discharge was significantly earlier in ropivacaine group(10.10±2.10 hrs) followed by levobupivacaine group(12.40±2.30 hrs) and bupivacaine group(14.80±3.63 hrs). Hypotension and Bradycardia was seen in all three groups (least with levobupivacaine) which was clinically insignificant. None of the patients had other clinically significant adverse effects like shivering, respiratory depression, nausea and vomiting, pruritus, headache and urinary retention.

CONCLUSIONS: To conclude, the results of present study indicate that low dose(10 mg) of isobaric ropivacaine had a shorter duration of motor and sensory block, less intense motor blockade  and also a shorter time to ambulation and home discharge.So, intrathecal isobaric ropivacaine may prove as an attractive alternative when surgical anaesthesia of shorter duration is required as in day care surgeries.