Intrathecal Dexmedetomidine and Fentanyl as Adjuvant to Bupivacaine on Duration of Spinal Block in Addicted Patients
For spinal anesthesia, various local anesthetics have been used but there are significant physiologic and pharmacologic differences. Local anesthetics provide longer and better quality of block when used in adjunct to various drugs such as opioids.
It has been reported that addiction is an increasing problem in modern society. Prolonged use of opioids is associated with increased doses in order get relief from pain. Addicted patients have innate tolerance to local anesthetics in both neuraxial and peripheral blocks.
Dexmedetomine (Dex) is a highly selective α2 adrenergic receptor agonist used as additive to increase the quality and duration of peripheral nerve blocks. DEX is a newly discovered drug that gained much reputation in neuroanesthesia, intensive care unit (ICU) and cardiac anesthesia in recent years. It has been shown that dexmedetomidine has better effects on sensory and motor block duration of onset in comparison with ketorolac, as lidocaine adjuvants in infraclavicular brachial plexus block.
A randomized study was conducted for elective surgery of lower abdomen or lower extremities which was less than of three hours. 5 µg of dexmedetomidine was added to 12.5 mg (2.5ml) of 0.5% hyperbaric bupivacaine (DEX group) or 25 µg of fentanyl added to 12.5mg (2.5ml) of 0.5% hyperbaric bupivacaine (F group) or only 12.5mg of 0.5% hyperbaric bupivacaine were given to the patients who were selected for the study. Data recorded was based on the sensory block and motor block was tested using modified Bromage scale after every 30 minutes, until the end of block. Return time of Bromage scale to 0 was also recorded. All vital measurements (oxygen saturation, heart rate, electrocardiogram and non-invasive blood pressure) were performed at 0, 30, 60, 90, 120 and 180 minutes in all three groups. Group DEX was given dexmedetomidine additive and group F received fentanyl additive and group C (control) was given normal saline.
Total 84 patients were randomly divided into three groups of 28 patients. Sensory block onset of DEX group was reported significantly lower than fentanyl (P = 0.012) and control group (P = 0.001). However, duration of sensory block was significantly longer in DEX group than fentanyl (P = 0.043) and control groups (P = 0.016). Duration of motor block in the DEX group was significantly longer than fentanyl (P = 0.014) and control groups. Heart rate and mean arterial pressure were significantly higher in DEX group at 30, 60, 90, 120 and 180 minutes as compared to other two groups (P < 0.05).
Results have shown that dexmedetomidine added to bupivacaine in spinal anesthesia is more effective in increasing the duration of block and provides more appropriate sedation and less post operative pain scale and post operative nausea, vomiting (PONV) compared to fentanyl additive.