Thoracic Paravertebral Blockade and Thoracic Epidural Analgesia

To the Editor Cowie et al.1 showed that dye injected into the paravertebral space spread into the epidural space of 40% of cadavers receiving such injections. This observation confirms that of Purcell et al., who showed that as much as 70% of 5 mL paravertebral injections entered the epidural space in patients.2 The fact that the paravertebral space communicates freely with the epidural space through the intervertebral foramina3,4 should alert clinicians administering local anesthetics into the paravertebral space, whether percutaneously (blindly or ultrasound guided) or under direct vision intraoperatively, that a paravertebral block (PVB) often becomes an epidural block, unilateral or bilateral, and may under certain circumstances also result in total spinal anesthesia.5 PVB is currently being touted as the preferred method for pain relief after thoracic surgery.6 However, on the basis of a systematic review of 10 published trials comparing thoracic PVB with thoracic epidural analgesia (TEA) for postthoracotomy analgesia, we conclude that neither method was superior or safer.7 These trials were small and heterogeneous and none applied optimal TEA regimens,7 and the paravertebral dose of local anesthetic was frequently twice that of the epidural dose.7 In summary, the paravertebral space communicates with the epidural space, is close to the pleural space, and contains supply arteries to the spinal cord. PVB requires injection of relatively large volumes of concentrated local anesthetic solutions, which frequently and unpredictably2 spread to the epidural space and possibly to the subarachnoid space. Complications do occur, and a PVB requires at least the same degree of respect for indications, contraindications, and monitoring as does a TEA. With both methods, vigilant monitoring for early symptoms of complications and timely interventions are mandatory.7 Hilde M. Norum, MD Harald Breivik, PhD, MD Division of Anaesthesia and Intensive Care Medicine Oslo University Hospital Rikshospitalet Oslo, Norway [email protected]