Comparison of Ropivacaine With or Without Fentanyl in Spinal Anaesthesia for Lower Limb Surgeries

Spinal anaesthesia has been a widely used mode of anaesthesia for lower abdominal and extremity surgeries. It blunts the "stress response" to surgery, decreases intraoperative blood loss, lowers the incidence of postoperative thromboembolic events, and decreases the morbidity in high-risk surgical patients. It serves as a useful method to extend analgesia into the postoperative period, where its use has been shown to provide better analgesia than parenteral opioids. In order to improve further and understand safety issues as well as the clinical use of spinal anesthesia, new local anesthetics and analgesic additives are being investigated for different application. With patient safety and comfort being the ultimate goal of any health practice, one must keep in mind about the side effects and related concerns of spinal anesthesia while achieving the desired level of anaesthesia and analgesia. Adequate anesthesia and analgesia during and post-surgery along with early ambulation and discharge seems to be the perfect recipe for the conduction of spinal anaesthesia in the current practice. Ropivacaine is one local anesthetic that could have the potential in this area. Ropivacaine is an amide local anesthetic with properties similar to bupivacaine producing similar sensory block at equipotent doses, but with a shorter duration of motor block. Thus, ropivacaine has a greater degree of motor sensory differentiation, which could be useful when motor blockade is undesirable. Ropivacaine blocks nerve fibers involved in pain transmission (A∂and C fibers) to a greater degree than those controlling motor function (Aβ fibers).Blockade of Aα and Aβ is slow and hence produces lesser motor blockade than bupivacaine. Though 40-50% less potent than bupivacaine, ropivacaine in an equipotent ratio of 1.5:1 produces results in a similar clinical profile with good preservation of motor function. Hence, its shorter duration, faster recovery of motor function, lower toxicity profile, and minimal hemodynamic alterations have been identified as a potential benefit for surgery of intermediate duration as well as for ambulatory surgery.

Though the use of bupivacaine is widespread, ropivacaine in the recent times has been used as a spinal anaesthetic agent and evaluated in many procedures because of its equivalent spinal anaesthetic effect and its lower risk of neurotoxicity and cardiotoxicity, compared with bupivacaine. In addition, there have been reports of fatal cardiovascular toxicity following use of bupivacaine in regional anesthesia.

Subarachnoid opioids with local anesthetics have become a well-accepted practice in spinal anesthesia for surgical procedures. Several combinations of local anesthetics such as lidocaine, bupivacaine, or ropivacaine, and opioids such as fentanyl have been reported for a variety of surgical procedures. The addition of small-dose fentanyl (10-25 μg) intrathecally to local anesthetics during spinal anesthesia has been shown to enhance duration of sensory analgesia.The addition of adjuvants to ropivacaine has shown to improve the quality of intra-operative and postoperative analgesia without compromising its benefits such as early mobilization and early voiding. Parlow et al. established the fact that hypobaricity influenced the extent of subarachnoid block and explained high cephalic levels of sensory block when fentanyl was added to isobaric local anesthetic solution.