Where should local anesthetic be placed to achieve interpleural analgesia?

To achieve interpleural analgesia, local anesthetic should be placed immediately deep to the parietal pleura. This positioning is crucial because the parietal pleura is sensitive to pain and is innervated by the intercostal nerves. By injecting the anesthetic solution in this area, it can effectively block the transmission of pain signals from the thoracic cavity, providing the desired analgesic effect.

Injecting the anesthetic too far away from the target site, such as superficially to the internal intercostal muscle or deep to the visceral pleura, would not allow for adequate pain relief. The visceral pleura does not have pain receptors and would not be effective for analgesia. Similarly, placing the anesthetic along the cephalad border of a rib may not achieve the desired effect of blocking the pain pathways adequately, as it does not target the parietal pleura directly. The effectiveness of interpleural analgesia is thus fundamentally linked to accurately placing the anesthetic beneath the parietal pleura, which allows it to interact with the necessary nerve pathways.