Anatomical target, Coverage
This peripheral nerve block is performed with the goal of depositing local anesthetic in the neurovascular “interfascial” plane between the internal oblique and transversus abdominis muscles. This plane contains anterior rami of spinal nerves T7 to L1, which provide innervation to the skin, muscles, and parietal peritoneum of the anterolateral abdominal wall. This block is effective for somatic and incisional pain, but lacks effectiveness for visceral pain.
Indications
Provision of analgesia for any lower abdominal procedures below the umbilicus, as well as laparoscopic surgery. Bilateral blocks can be administered for midline incisions, or for laparoscopic surgery. For analgesia above the umbilicus, augmentation with a “subcostal” TAP will more reliably achieve a higher block up to T7.
TAP blocks are most commonly done as a single injection; however, a catheter-based technique may be chosen in circumstances where longer block duration is required.
Block technique
This block is most commonly performed these days with ultrasound guidance. The block is performed on a supine patient, often under general anesthesia, but it can also be done with local or minimal sedation.
The ultrasound probe is placed transverse to the abdominal wall in the midaxillary line, between the costal margin and iliac crest. The needle is inserted on the medial side of the probe, in the plane of the ultrasound beam, ideally fully visualized as the needle is advanced into the plane above the transversus abdominis muscles. Typically two “popping” sensations are appreciated by the proceduralist as two fascial planes are being traversed on the way to the transversus abdominis plane: this was used as guidance in the pre-ultrasound era to perform this block.
Subcostal TAP block is performed by placing the probe just beneath the costal margin and parallel to it. The target is the interfascial plane between the posterior rectus sheath and the transversus abdominis muscle.
General dosing guide:
Adult patients >60kg
Single shot: 20-30ml of 0.2-0.5% ropivacaine
Infusion: 8ml/hour 0.1-0.2% ropivacaine
Block Duration
When performed with ropivacaine, the TAP block has an analgesia duration of up to 24 hours, with an average duration of about 6 hours.
Special Considerations
Contraindications, side effects, and complications
Patient refusal, coagulopathy, local anesthetic allergy, infection at the site of needle entry, inability to cooperate.
This block is usually well tolerated with few side effects, but potential complications include intraperitoneal injection, bowel perforation, bowel hematoma, hepatic perforation. Local anesthetic systemic toxicity (LAST) can also occur due to the large volumes required to perform this block, especially if done bilaterally.
Who do I contact if I feel my patient could benefit from a regional anesthesia technique?
When booking OR cases, surgeons can enter requests for regional anesthesia. The Department of Anesthesia schedules experienced providers to perform these blocks in all OR’s. For regional anesthesia in inpatients, reach out to the Acute Pain Service that covers your campus.
Please see the link for the pain team consult service: https://anesthesia.ucsf.edu/divisions/pain-medicine#for-providers--request-consult-or-refer-a-patient
Finnerty O, Carney J, McDonnell JG: Trunk blocks for abdominal surgery. Anaesthesia 2010; 65 Suppl 1:76-83.
Hebbard P. Subcostal transversus abdominis plane block under ultrasound guidance. Anesth Analg. 2008;106(2):674.