Dr. Rabida C
Specialist in Anaesthesiology
Baby Memorial hospital , Kannur
Effective perioperative pain management plays a crucial role in improving surgical outcomes, reducing opioid consumption, and enhancing patient recovery. In recent years, ultrasound-guided fascial plane blocks have become an important part of multimodal analgesia strategies.
The External Oblique Intercostal Plane Block (EOIPB) is a relatively new ultrasound-guided interfascial block , first described in 2019 as a novel regional anaesthesia technique designed to provide analgesia for upper abdominal procedures. The block involves deposition of local anaesthetic in the fascial plane between the external oblique muscle and the external intercostal muscle near the costal margin. By targeting the thoracoabdominal nerves in this region, EOIPB provides somatic analgesia of the upper abdominal wall.
Given its superficial location and relative ease of performance under ultrasound guidance, EOIPB has emerged as a promising alternative to deeper regional techniques.
Anatomy
The sensory innervation of the anterior abdominal wall primarily arises from the ventral rami of the lower thoracic spinal nerves (T6–T12). After emerging from the intercostal spaces, these nerves continue anteriorly as thoracoabdominal nerves, coursing along the costal margin toward the abdominal wall.
During their course, the thoracoabdominal nerves travel between the intercostal muscles and subsequently enter the abdominal wall, where they run within fascial planes between the abdominal muscles. Along their pathway, they give rise to two important branches:
• Lateral cutaneous branches, which supply the lateral abdominal wall
• Anterior cutaneous branches, which supply the midline abdominal skin
Near the costal margin, a distinct
fascial plane exists between the external oblique muscle and the external intercostal muscle covering the ribs.
Injection of local anesthetic into this potential plane allows the anesthetic to track along the costal margin and block the anterior and lateral branches of the thoracoabdominal nerves. Anatomical and cadaveric studies have demonstrated that the spread within this fascial plane can produce sensory blockade typically extending from T6 to T10 dermatomes, thereby providing effective analgesia for the upper abdominal wall.
Technique
Block is performed under ultrasound guidance with the patient in the supine position. A high-frequency linear ultrasound probe is placed parallel to the costal margin, usually at the level of the sixth rib, between the mid-clavicular and anterior axillary lines.
On ultrasound imaging, the external oblique muscle appears as the most superficial muscular layer, with the rib and external intercostal muscle located beneath it. The pleura lies deeper and should be clearly identified to avoid inadvertent injury.
Using an in-plane needle approach, the block needle is advanced toward the fascial plane between the external oblique muscle and the rib/external intercostal muscle. After confirming correct needle placement with hydrodissection, 20–30 ml of local anesthetic is injected into the plane. The correct spread appears as a hypoechoic layer separating the external oblique muscle from the underlying rib.
For surgical procedures involving the midline or bilateral incisions, the block is usually performed bilaterally to achieve adequate analgesic coverage.
Clinical Indications
EOIPB provide effective analgesia for several surgical procedures involving the upper abdomen, including:
• Ventral hernia repair
• Upper abdominal laparotomy
• Lower thoracic surgery
• Bariatric surgery
• Laparoscopic cholecystectomy
• Open or laparoscopic hepatobiliary surgery
Advantages
• Superficial block with easy ultrasound visualization
• Lower risk of neuraxial or pleural complications
• Technical simplicity
• Effective opioid-sparing analgesia
• Suitable for bilateral use
• Compatible with enhanced recovery protocols
Because the injection site is away from the neuraxis and major vascular structures, EOIPB is considered relatively safe.
Limitations
Despite its promising role, EOIPB has certain limitations:
• Primarily provides somatic analgesia and may not adequately cover visceral pain.
• Dermatomal spread can be variable.
• Evidence is still limited, with relatively few randomized controlled trials available.
The external oblique intercostal plane block is a promising ultrasound-guided fascial plane block that provides effective analgesia for upper abdominal procedures. Its ease of performance, superficial location, and favorable safety profile make it an attractive addition to the armamentarium of regional anesthesia techniques.