Ultrasound Guided Serratus Anterior Plane Block Versus Ultrasound Guided Thoracic Epidural Analgesia

Acute post-surgical pain leads to delayed discharge from post-operative recovery area, impairs pulmonary and immune functions, increases risk of ileus, thromboembolism, myocardial infarction and may lead to increased length of hospital stay. It is also an important factor leading to the development of chronic persistent post-operative pain in almost half of the patients. Post-operative pain, stress and use of morphine have been elucidated as factors responsible for increased risk of metastasis. Hence, an effective perioperative pain management of patients undergoing breast surgery is essential. Regional blocks have been considered as one of the modalities for effective perioperative pain control. They have an opioid-sparing effect, and allow early mobilisation and early discharge from hospital. Ultrasound-guided muscle plane blocks have changed the practice of regional anesthesia for breast surgeries. Different variations of Pecs block have been described with an aim to provide anesthesia and analgesia of the hemi thorax. Recently described serratus anterior plane (SAP) block was designed to target primarily the thoracic intercostal nerves, providing complete analgesia to the lateral part of the thorax. Compared with Pecs-II, the needle is placed more caudally and posteriorly in SAP block and local anesthetic (LA) is deposited either superficial or deep to the serratus anterior muscle. Serratus Anterior Plane (SAP) block has been described recently as injection of local Anesthetic (LA) in mid axillary line at the level of the 5th rib either superficial or deep to the serratus anterior (SA) muscle. The intention is to block the thoracic intercostal nerves to provide complete analgesia of the lateral part of the chest. There are some clinical reports validating its use in breast surgeries. Although serratus anterior plane (SAP) block affects the long thoracic nerve of bell supplying serratus anterior (SA) but there is no mention of blocking the thoracodorsal nerve supplying latissmus dorsi (LD).The thoracodorsal nerve is the sole nerve that supplies latissmus dorsi (LD) and forms a plexus between serratus anterior (SA)and latissmus dorsi (LD). On the other hand, regarding thoracic epidural analgesia, the results from MRI studies indicate that the spinal cord lies anteriorly within its thecal sac in the thoracic curve and the following measures were found: 5.19 mm in T2, 7.75 mm in T5 and 5.88 mm in T10, this let us say, sufficient distance to permit the careful advancement of a needle (accidentally or intentionally) without reaching the cord and administer anesthetic for a segmental spinal anesthesia. This anatomical explanation was proposed for the absence of spinal cord injury during an accidental perforation during attempted thoracic epidural.