Ropivacaine

Mechanism of Action

Ropivacaine is a long-acting amide local anesthetic. It exhibits a similar mechanism of action to other local anesthetics in that it reversibly inhibits sodium ion influx in nerve fibers. Amides preferentially bind and inactivate sodium channels in the open state—thereby blocking the propagation of action potentials. The dose-dependent inhibition of potassium channels potentiates this action.

Ropivacaine has a few properties that make it unique. Ropivacaine is less lipophilic than other local anesthetics, such as bupivacaine, and is less likely to penetrate large myelinated motor fibers. It, therefore, selectively acts on the nociceptive A, B, and C fibers over the AB (motor) fibers. Ropivacaine is also manufactured as a pure S(-) enantiomer; the S(-) enantiomer has significantly less cardiotoxicity and neurotoxicity.[4][5]

Administration

Ropivacaine is administered in incremental doses. Factors that affect the dosing of any administered local anesthetic include the area to be anesthetized, the vascularity of tissues, the number of neuronal segments to be blocked, and the depth and duration of anesthesia required.[6]

An adequate test dose of 3 t5o 5 mL of short-acting local anesthetic with epinephrine should be used before the induction of the complete block. A repeat of the test dose should be given if the patient is moved in such a way that displacement epidural catheter may have occurred.

For lumbar surgery epidural blocks, the ropivacaine doses considered necessary to produce a successful block are 15 to 30 mL of 0.5% solution, 15 to 25 mL of 0.75% solution, 15 to 20 mL of 1% solution.

When used in lumbar epidural blocks for cesarean section, the doses for ropivacaine are 20 to 30 mL of 0.5% solution and 15 to 20 mL of 0.75% solution.

Dosages of ropivacaine when performing thoracic epidural blocks for surgical anesthesia are 5 to 15% mL dose of 0.5% solution and 5 to 15 mL of 0.75% solution.

When performing major nerve blocks, the dosages are 35 to 50 mL of 0.5% solution and 10 to 40 mL of 0.75% solution.

For field blocks (e.g., minor nerve blocks and infiltration), ropivacaine is dosed at a 1 to 40 mL dose of a 0.5% solution.

When managing post-operative pain, peripheral nerve blocks are continuously infused at a dose of 5 to 10 mL/hr of 0.2% solution. For pain management through lumbar or thoracic epidurals, the continuous infusion dose of ropivacaine is at 6 to 14 mL/hr of 0.2% solution.

In prolonged blocks, there should be consideration of the risks of reaching a toxic plasma concentration or inducing local neural injury. A 24-hour cumulative dose of up to 770 mg ropivacaine is generally well-tolerated in adults for postoperative pain management. Ropivacaine should be used with caution when administering it to debilitated patients for more than 70 hours.[7][8][9][10]

Adverse Effects

Ropivacaine is generally well tolerated. A pooled analysis from controlled clinical trials (n=1,661), in which patients received ropivacaine concentrations from 0.125 to 1% for nerve blocks, indicates that the most common adverse reactions are hypotension (32%), nausea (17%), vomiting (7%), bradycardia (6%), and headache (7%). A similar side effect profile occurred in patients who received bupivacaine concentrations of 0.25 to 0.75%. Overall, adverse events with ropivacaine are rare when it is properly administered.

Patients 61 years or older who received epidural ropivacaine 1% had a higher incidence of bradycardia than patients aged 41 to 60 years (58% vs. 15%); they also had a higher incidence of hypotension than patients aged 18 to 40 years old (74% vs. 20%).

The overall incidence of adverse reactions in children one month to 15 months is low; the most common adverse effects of ropivacaine in this age group were nausea and/or vomiting.

The most common fetal or neonatal adverse reactions following the use of ropivacaine in women undergoing cesarean section or labor were fetal bradycardia (12%), neonatal jaundice (8%), and unspecified neonatal complications (7%).[11]

Contraindications

The only absolute contraindication to ropivacaine is for patients with a known hypersensitivity to ropivacaine or any amide-type local anesthetic.[6]

Monitoring

Attention should be paid to vital signs (heart rate, blood pressure, oxygen saturation) after administering a test dose to ensure that the local anesthetic is not intravascular. Cardiovascular and respiratory vital signs should be monitored after each local anesthetic injection. Restlessness, anxiety, perioral paresthesias, metallic taste, tinnitus, tremors, and blurred vision are a few of the early signs of central nervous system toxicity.[12]

Toxicity

Local anesthetic system toxicity (LAST) primarily affects the central nervous system (CNS) and cardiovascular system. Local anesthetics can be assigned a cardiovascular collapse (CC) to CNS ratio, which is the ratio of the drug required to cause cardiovascular collapse compared to the drug dose required to produce seizures. Ropivacaine has a higher CC to CNS ratio (indicating a higher margin of safety) than bupivacaine and levobupivacaine. Ropivacaine has a greater arrhythmogenic cardiac effect and less of an effect on contractility.[13]

Enhancing Healthcare Team Outcomes

Multimodal analgesia involves using medications that act on different sites and pathways in an additive or synergistic manner to give pain relief with minimal or no opiate use. Opioids are associated with adverse effects such as nausea, vomiting, respiratory depression, and dependence syndromes. Local anesthetics play a large role in multimodal analgesia. Regional anesthesia can significantly reduce post-operative pain frequency and improve overall patient satisfaction. [Level I]

Ropivacaine has additional benefits compared to other local anesthetics because it is less cardiotoxic. This characteristic makes it a safer option as a pain relief option for patients being sent home postoperatively. Administration of ropivacaine often requires a team of health professionals, including prescribing clinicians (MDs, DOs, NPs, PAs), pharmacists, nursing, and home health.[14][15] When properly administered and monitored by an interprofessional team engaged in a collaborative effort and open communication, ropivacaine is a safe option for pain relief with very few adverse events. [Level 5]