High concentration of bupivacaine during labour is contraindicated due to its
**Core Concept**
Bupivacaine is a long-acting local anesthetic commonly used for regional anesthesia, including epidural anesthesia during labor. Its high concentration can cause adverse effects due to its pharmacological properties.
**Why the Correct Answer is Right**
High concentrations of bupivacaine can lead to systemic toxicity, which is primarily due to its lipid solubility and ability to cross the blood-brain barrier. This results in central nervous system (CNS) effects, including seizures and cardiac arrest. The mechanism of bupivacaine-induced cardiotoxicity involves sodium channel blockade, leading to abnormal heart rhythms and decreased cardiac contractility.
**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect as bupivacaine's local anesthetic effect is not its primary concern during labor; rather, it's the systemic toxicity associated with high concentrations.
**Option B:** While bupivacaine does have a high degree of protein binding, this is not the primary reason for its contraindication in high concentrations during labor.
**Option C:** Bupivacaine's vasodilatory effect is not the primary concern during labor; rather, its potential for causing systemic toxicity is the main concern.
**Clinical Pearl / High-Yield Fact**
To avoid bupivacaine-induced systemic toxicity, it's essential to use the minimum effective dose and concentration for epidural anesthesia during labor. A maximum dose of 175 mg of bupivacaine is recommended to minimize the risk of adverse effects.
**Correct Answer:** C. **Cardiotoxicity**