Rhomboid intercostal and sub-serratus (RISS) block

Intermediate. The scapula has to be moved out of the way, and the target is directly on a rib with the pleura just beneath.

The rhomboid major runs from the spinous processes T2–T5 to the medial border of the scapula, deep to trapezius. Below the lower end of the scapula, the rhomboid and serratus planes are continuous.

The rhomboid intercostal plane lies between rhomboid major and the intercostal muscles. Injected fluid spreads laterally under serratus anterior (the sub-serratus plane) to reach the lateral cutaneous branches of the intercostal nerves, and medially towards the dorsal rami.

Elsharkawy and colleagues showed staining of the lateral branches of the intercostal nerves from T3 to T9 in cadavers.

• Medial border and inferior angle of the scapula.
• Spinous processes T5–T7.
• The 'triangle of auscultation' between trapezius, latissimus dorsi and the scapula.

• Posterior and lateral rib fractures.
• Thoracotomy, VATS and posterior chest wall surgery.
• Scapular and upper back surgery.
• Upper abdominal wounds (with the sub-serratus component at lower levels).

• Lateral cutaneous branches of the intercostal nerves (about T3–T9).
• Variable spread to the dorsal rami (posterior chest).

Surface anatomy, relevant structures and landmarks

There is no landmark technique; this block is done with ultrasound.

Positioning

Not applicable.

Block technique

Not applicable.

Needle choice

Not applicable.

Neurostimulation technique

Not used.

Choice of local anaesthetic (including volume)

See the ultrasound technique.

Positioning

Lateral or sitting, with the arm across the chest to pull the scapula laterally.

Scanning technique

• Rhomboid intercostal: place the probe in an oblique-sagittal plane 1–2 cm medial to the medial border of the scapula at T5–T6. Identify trapezius, rhomboid major, the ribs, intercostal muscles and pleura.
• Sub-serratus: move the probe laterally below the inferior angle of the scapula, to about the posterior axillary line at T7–T9, and identify latissimus dorsi, serratus anterior and the ribs.

Structures to identify

• Trapezius
• Rhomboid major
• Medial border of the scapula
• Ribs
• Intercostal muscles
• Pleura
• Serratus anterior (sub-serratus part)

Position / ergonomics

Stand behind the patient with the screen in front of you.

Probe

Linear high-frequency probe.

Settings

Musculoskeletal preset, depth 4–5 cm.

Depth

2–4 cm.

Needle size

22 G, 50–80 mm.

Needling technique

In-plane from cephalad to caudad, through trapezius and rhomboid, to touch the rib. Inject between rhomboid major and the intercostal muscles. Repeat under serratus anterior for the sub-serratus component.

Optimal needle-tip position

On the rib, deep to rhomboid major (and, laterally, deep to serratus anterior).

Drug choice

0.25% levobupivacaine or bupivacaine, or 0.2–0.375% ropivacaine.

Volume

20–30 mL for each injection; keep within the maximum safe dose.

Optimal current if nerve stimulation is used

Not used.

Muscle responses acceptable

Not applicable.

Testing block success

• Loss of cold over the back and side of the chest
• Easier breathing and coughing with rib fractures

Indication

Multiple rib fractures, thoracotomy.

Kit

Tuohy needle with catheter.

Catheter

In the rhomboid intercostal or sub-serratus plane, advanced 3–5 cm.

Regime

0.2% ropivacaine at 5–10 mL/h, or programmed intermittent boluses.

• Move the arm forward to bring the scapula out of the way.
• Keep the needle tip on a rib.
• The two injections can be done through one skin puncture in slim patients.

• Elsharkawy and colleagues (2018) described the RISS block: in 6 cadavers, dye stained the lateral branches of the intercostal nerves from T3 to T9, and a series of 15 patients showed anterior chest numbness and pain scores below 5.
• Evidence is still limited to case series and small trials.

• Elsharkawy H, Maniker R, Bolash R, Kalasbail P, Drake RL, Elkassabany N. Rhomboid intercostal and subserratus plane block: a cadaveric and clinical evaluation. Reg Anesth Pain Med 2018;43:745–751. PubMed